Clin Auton Res (2010) 20:289–330 DOI 10.1007/s10286-010-0082-6

ABSTRACTS

Wednesday, November 3, 2010

Relationship between cardiovagal activity and endothelial function in young healthy subjects

Oral Presentations Respiration-adjusted low frequency power of heart rate variability reflects baroreflex function, not cardiac sympathetic innervation F. Rahman, S. Pechnik, D.J. Gross, L. Sewell, D.S. Goldstein Clinical Neurocardiology Section, CNP, DIR, NINDS, NIH, Bethesda, MD, USA Background: Power spectral analysis of heart rate variability is used clinically to assess cardiac autonomic function. High frequency power is related to respiratory sinus arrhythmia and therefore to parasympathetic cardiovagal tone. The relationship of low frequency (LF) power to cardiac sympathetic tone is less clear. We reported previously that LF power may reflect baroreflex function in supine subjects; however, clinical autonomic testing is often done with the patients sitting, and in the previous study LF power was not adjusted for possible influences of respiration. We assessed relationships of LF power, including respiration-adjusted LF power (LFa) using the ANSAR ANX 3.0 device, with cardiac sympathetic innervation and baroreflex function in chronic autonomic failure patients who either had or did not have neuroimaging evidence of cardiac sympathetic denervation. Methods: Values for LF power while seated at baseline and during the Valsalva maneuver were compared between patient groups with low or normal myocardial concentrations of 6-[18F]fluorodopaminederived radioactivity. Baroreflex-cardiovagal gain (BRS) was calculated from the slope of cardiac interbeat interval versus systolic pressure during the Valsalva maneuver with subjects supine. Results: Individual values for LF and LFa were unrelated to myocardial 6-[18F]fluorodopamine-derived radioactivity. During both sitting rest and the Valsalva maneuver the logs of LF and LFa correlated positively with the log of BRS (r = 0.61, p = 0.0005; r = 0.47, p = 0.009; r = 0.69, p \ 0.0001; r = 0.60, p = 0.0006). Patients with low BRS (=3 ms/mmHg) had low LF and LFa regardless of the status of cardiac innervation. Interpretation: LF and LFa reflect baroreflex function independently of cardiac sympathetic innervation.

A. Pinter, T. Horva´th, M. Kollai Institute of Human Physiology and Clinical Experimental Research, Semmelweis University, Budapest, Hungary Introduction: In various diseased states, such as diabetes mellitus or chronic heart failure, reduced cardiovagal activity (CVA) is accompanied by impaired endothelial function. It is unclear whether CVA and endothelial function are linked and negatively affecting each other, or these systems independently undergo dysregulation as a consequence of the disease process. In our study, we investigated the relationship between endothelial function and CVA within healthy, young population. Participants and methods: 30 young, healthy males were enrolled to the study (19 ± 3 years). Endothelial function was assessed by brachial artery flow mediated dilation (FMD) and hyperemic, diastolic shear rate was used to normalize FMD (nFMD). CVA was characterized by the indices of heart rate variability (HRV). Time- and frequency domain measures of HRV were calculated from 10 min ECG recordings (RMSSD—the root-mean-square of successive RRinterval differences; HF—high frequency power of RR-interval variability). Results: All values fell within the age related normal range (mean ± SD): FMD—(7.76 ± 3.22%); nFMD—(39.01 ± 15.1%/ cm/s); RMSSD—(66.80 ± 34.43 ms); HF—(1,566 ± 1,559 ms2). The relationship between FMD–RMSSD; HF and nFMD–RMSSD; HF were r = 0.37*; r = 0.45* and r = 0.48**; r = 0.53**, respectively. (*p \ 0.05; **p \ 0.01). Discussion: The correlation between endothelial function and CVA might be explained by central vasculoneural communication. The structure of the cerebral microcirculation allows endothelial mediators, such as NO, to exert neuromodulatory effects. NO was shown to act as a sympatholytic and vagotonic agent at various sites of the autonomic nervous system (ANS). Therefore, it might be hypothesized, that NO—originating from the capillary endothelium— influences CVA. On the other hand, ANS and endothelium on the periphery work together to maintain vascular tone. Sympathetic vasoconstrictor agents counteract the effect of endothelial vasodilator substances. Increased CVA is often associated with reduced sympathetic activity which may result in improved endothelial function.

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Autonomic function in mild cognitive impairment O. Collins, S. Dillon, C. Finnucane, B.A. Lawlor, R.A. Kenny Trinity College and St James’s Hospital, Dublin, Ireland Objectives: Autonomic dysfunction is prevalent in the common dementia subtypes. The structures involved in autonomic control are affected by the dementia process prior to the onset of clinical dementia. However, there are no studies examining autonomic function in mild cognitive impairment. We explored autonomic function in MCI participants compared with controls. Methods: MCI was defined using the Consensus criteria for MCI and by neuropsychological assessments (= 1.3 SD in memory/non-memory domain). Heart rate variability was performed from a 5 min continuous ECG recording. The Ewing’s battery of bedside autonomic tests included 3 parasympathetic tests (heart rate response to deep breathing, Valsalva manoeuvre and orthostasis) and 3 sympathetic tests (blood pressure response to orthostasis, Valsalva manoeuver and cold pressor test). Autonomic neuropathy was defined as having 2 or more abnormal heart rate responses. Cognitive assessments performed included the MMSE, CAMCOG and Computerized Drug Reaction Battery (CDR). Significant level was taken as \0.05. Results: Overall, 101 MCI participants and 37 controls completed assessments (median age 73 and 72 respectively). There were significant differences in the prevalence and severity of autonomic dysfunction compared with controls. The MCI group showed consistent parasympathetic dysfunction across assessments in Ewing’s battery (deep breathing p \ 0.005, orthostasis p = 0.01 and Valsalva manoeuver p = 0.02) and but not in heart rate variability. There was no difference in sympathetic dysfunction between groups. The prevalence of autonomic neuropathies was higher in the MCI group than controls (p \ 0.005). Participants with autonomic neuropathy showed more severe global cognitive deficits (P \ 0.001) and in memory (P = 0.002), attention (P = 0.001) and executive function (P = 0.004). Conclusion: Autonomic dysfunction, particularly parasympathetic dysfunction, is prevalent in MCI. This indicates that autonomic involvement in MCI is predominantly cardiovagally mediated. The exact mechanism between vagal nerve function and cognitive decline needs to be further explored but could be linked to the cholinergic anti-inflammatory pathway.

Parasympathetic ‘‘bias’’ as a form of autonomic dysregulation associated with depressive/hopeless states B.D. Miller, B.L. Wood Departments of Psychiatry and Pediatrics University at Buffalo, Buffalo, NY, USA Berntson makes a distinction between autonomic balance and autonomic regulatory capacity, with regulatory capacity defined as the extent to which mutual regulatory systems are able to flexibly and adaptively respond to changing demands. Primate and human studies show that separation of infants from parents results in an initial sympathetic (S) protest response, followed by a parasympathetically, (P) dominated ‘‘depressive’’ non-responsive condition. Miller proposed that this P bias may accompany depressive and hopeless emotional states in human children, and furthermore that this P bias would potentiate cholinergically mediated airway constriction in asthma. Depression is prevalent in pediatric asthma, and implicated in asthma morbidity and mortality. The goal of this study was to

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Clin Auton Res (2010) 20:289–330 examine whether P bias was associated with depressive states and airway compromise in children with asthma. Methods: Asthmatic children (aged 7–17) with high (D = 45) versus low (ND = 45) depressive symptoms were contrasted with respect to P and S reactivity and airway function before, during and after viewing an emotionally distressing film (E.T., the Extra-terrestrial). HFHRV(P) and PEP(S) reactivity to targeted scenes, airflow (FEV1), and respiratory resistance (Rint) were compared. P bias was defined as the preponderance of P over S reactivity to stress. Bias was operationalized as the normalized difference score of P minus S. (i.e. ZHFHRV minus ZPEP). The groups did not differ in demographics, medications, or adherence. The ND showed typical S activation to movie distress, whereas the D showed P activation and S withdrawal. The D group showed greater overall P bias (p = 0.03). The finding was most pronounced in loss and separation scenes (family distress/ loss (t = 1.95, p = 0.03); dying (t = 2.85, p = 0.003); and death (t = 1.90, p = 0.03) scenes). P bias was associated with airway resistance (r = 0.39; p = 0.004). Conclusion: P bias may constitute a form of ANS dysregulation that can potentiate disease process in autonomically mediated diseases.

Association of arterial pressure oscillations with direct measurement of sympathetic outflow in subjects with differing tolerances to central hypovolemia K.L. Ryan1, C.A. Rickards1,2, C. Hinojosa-Laborde1, V.A. Convertino1 1 US Army Institute of Surgical Research, Fort Sam Houston, TX, USA; 2 Department of Health and Kinesiology, University of Texas at San Antonio, TX, USA We have previously reported that low frequency (0.04–0.15 Hz) systolic arterial pressure oscillations (SAPLF) do not demonstrate high linear correlations with muscle sympathetic nerve activity (MSNA) during central hypovolemia induced by lower body negative pressure (LBNP; FASEB J 23:1019.5, 2009), suggesting that SAPLF may not be useful as a noninvasive marker of sympathetic activation. In the current study, we expand on this finding by leveraging innate individual differences in tolerance to central hypovolemia to further interrogate SAPLF as a marker of sympathetic activity. We tested the hypothesis that the relationship between SAPLF and MSNA will be similar across all subjects despite varying LBNP tolerances. Subjects (15 M/6 F) were instrumented to record ECG, beat-by-beat arterial pressure (Finometer) and MSNA (microneurography on peroneal nerve) during a progressive LBNP protocol to the point of tolerance (i.e., presyncope), followed by recovery. SAPLF was calculated following Fourier transform. Subjects were then retrospectively grouped into those that were high tolerant (HT; those who completed at least the -60 mmHg level of LBNP) and low tolerant (LT; those who did not complete the -60 mmHg level). At baseline, SAPLF was not associated with MSNA burst frequency or total MSNA (R2 = 0.04). For all subjects (n = 21), group means of SAPLF, MSNA burst frequency, and total MSNA increased progressively during LBNP. HT subjects (n = 15) demonstrated an exponential relationship between SAPLF and both MSNA burst frequency and total MSNA (R2 = 0.94). In contrast, LT subjects (n = 6) showed no increases in SAPLF despite increases in MSNA. These results therefore do not support the use of SAPLF as a noninvasive metric of sympathetic outflow since individuals with low tolerance to reductions in central blood volume do not increase SAPLF despite profound sympathetic activation.

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Cardiovascular autonomic assessment in rats with spinal cord injury J.A. Inskip1,2, L.M. Ramer1,3, M.S. Ramer1,3,4, A.V. Krassioukov1,5,6, V.E. Claydon1,2 1 International Collaboration on Repair Discoveries (ICORD), University of British Columbia (UBC), Vancouver, BC; 2 Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC; 3 Department of Zoology, UBC; 4 Department of Surgery, UBC; 5 Department of Medicine, Division of Physical Medicine and Rehabilitation, UBC; 6 GF Strong Rehabilitation Centre The severity of injury to cardiovascular autonomic pathways following clinical spinal cord injury (SCI) can be evaluated with spectral analyses. Whether this technique provides a translatable assessment of cardiovascular autonomic function in rodent models of SCI, or relates to measures of blood pressure control remains unknown. To assess this, we performed spectral analyses and cardiovascular assessments in rodents with SCI. We correlated frequency domain variables with the severity of orthostatic hypotension (OH), defined as the maximum decrease in systolic arterial pressure [SAP] during 90° head-upright tilting, and severity of hypertension during an episode of autonomic dysreflexia (AD), defined as the increase in SAP in response to colorectal distension. Beat-to-beat heart rate and blood pressure variables were obtained via carotid artery cannulation in male rats at rest 1 month after complete T3 SCI or T10 SCI, or in uninjured controls. Univariate autoregressive spectral analyses were performed on time series extracted from beat-to-beat data. Low frequency (LF), high frequency (HF) and very low frequency (VLF) peaks were identified and the power and central frequency of each peak calculated by computation of the residuals. Total power of both pulse interval and blood pressure variability was reduced in animals with T3, but not T10 SCI. VLF and LF pulse interval variability were reduced and HF variability increased in T3, but not in T10 SCI. VLF and LF blood pressure variability were reduced in T3, but not T10 SCI. In animals with SCI, severity of OH was negatively correlated with both HF and LF blood pressure variability. Severity of AD was positively correlated with LF blood pressure variability. We have shown that spectral analyses can detect alterations in cardiovascular autonomic function at rest. Importantly, these parameters also correlate well with the severity of AD and OH—clinically important measures of abnormal blood pressure control.

Thursday, November 4, 2010 Oral Presentations Prospective analysis of postural tachycardia syndrome K. Kimpinski1, V. Iodice2, D.M. Sletten3, W. Singer3, P. Sandroni3, A. Lipp4, T.L. Gehrking3, J.A. Gehrking3, K.K. Nickander3, P.R. Fischer5, J. Figueroa3, R.D. Fealey3, P.A. Low3 1 Department of Clinical Neurosciences, University Hospital, University of Western Ontario, London, ON, Canada; 2 Queens Square, Imperial College of London, London, UK; 3 Department of Neurology, Mayo Clinic, Rochester, MN, USA; 4 Department of Neurology, Charite´-University Medizin Berlin, Berlin, Germany; 5 Department of Pediatrics, Mayo Clinic, Rochester, MN, USA

291 Postural tachycardia syndrome (POTS) is defined by symptoms of orthostatic intolerance associated with heart rate increments[30 beats per minute (bpm) on head-up tilt with more severe cases reaching standing heart rates of[120 bpm. The prognosis in POTS appears to be favorable. A prior retrospective analysis showed that 80% of POTS patients improved and 60% became functionally normal over a 5-year period. However, prospective studies to confirm these findings are lacking. It was our aim to prospectively follow patients that met criteria for POTS. All patients underwent standard clinical autonomic testing including head-up tilt, Valsalva maneuver, cardiovagal studies, quantitative sudomotor axon reflex testing, and thermoregulatory sweat testing. Here we present our initial cohort of patients enrolled (n = 111) and 1 year follow up data for 45 patients. Female to male ratio was 4.6:1 at enrollment and 5.4:1 at 1-year follow up. Hyper-adrenergic and neuropathic phenotypes were seen at a frequency of 4.9 and 16.4% (at enrollment) and 5.3 and 26.7% (at 1 year), respectively. Composite Autonomic Severity Scores (CASS) revealed mild autonomic impairment at baseline (1.36 ± 1.11) and at 1 year (1.38 ± 1.61). Heart rate increment (head-up tilt at 5 min) at baseline (39.3 ± 15.0) did not differ from 1-year follow up (33.6 ± 15.6). Thermoregulatory sweat test results done at baseline showed a mild degree of sweat loss in our POTS population (% anhidrosis = 4.72 ± 13.48). Prospective follow up of our cohort reveals that the majority of our POTS patients had mild but present autonomic dysfunction at both baseline and 1-year follow up. Furthermore, a substantial fraction of these patients had modest sudomotor or adrenergic dysfunction compatible with the neurogenic variation of this syndrome. Overall, autonomic dysfunction did not significantly change over the 1-year follow up period.

Diurnal variations of blood pressure in postural tachycardia syndrome: dippers versus non-dippers J.J. Figueroa, D. Bott-Kitslaar2, J.A. Mercado1, J.R. Basford3, P. Sandroni1, W. Singer1, M.J. Joyner4, W.K. Shen2, D.M. Sletten1, T.L. Gehrking1, J.A. Gehrking1, P.A. Low1 1 Department of Neurology, Mayo Clinic, Rochester, MN, USA; 2 Department of Cardiology, Mayo Clinic, Rochester, MN, USA; 3 Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, MN, USA; 4 Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA Prior reports suggest that diminished nocturnal decrease in blood pressure (BP) occurs frequently in patients with postural tachycardia syndrome (POTS). We hypothesized that autonomic dysfunction due to either denervation or hyperadrenergic state contributes to non-dipping. We reviewed 51 patients with POTS evaluated at Mayo Clinic [2006–2009] in whom 24-h BP recordings and full autonomic function tests were performed. They all were evaluated in a uniform manner. Dippers were defined as those whose nocturnal systolic BP decreased = 10% of daytime BP. Neuropathic POTS required evidence of peripheral sudomotor denervation. Hyperadrenergic POTS was defined as standing norepinephrine (NE) [600 pg/ml. Of 51 patients (44 women; mean age 29 ± 8 years), 28 (55%) were nondippers. Age, body mass index and clinical characteristics did not differ between groups. Supine HR was comparable in both groups (75 ± 14 vs. 74 ± 14 bpm, p = 0.532) but orthostatic maximum heart rate increment was higher in dippers (DHR: 51 ± 15 vs. 41 ± 11 bpm, p = 0.007). Autonomic dysfunction was mild and did not differ between dippers and non-dippers, including frequency of distal sudomotor denervation (26 vs. 25%, p = 0.929). There was a trend towards a higher frequency of hyperadrenergic POTS in dippers (32 vs. 11%, p = 0.074). Dippers had a higher increase in orthostatic plasma NE than non-dippers (293 ± 136.6 vs. 209 ± 91.1 pg/ml, p = 0.028). 24-h urinary sodium excretion did not differ between groups (142 ± 76 vs. 131 ± 66 mEq, p = 0.564). In summary, the non-dipping phenomenon

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292 in POTS is frequent and in almost evenly distributed groups, dippers are significantly different to non-dippers in that they have greater orthostatic HR increment and NE increase. These findings suggest that dippers have a larger adrenergic response that is not due to differences in severity and distribution of autonomic failure or sodium intake (possibly plasma volume). Further studies are needed to confirm and determine the mechanism of this association.

Blood volume deficit and the non-dipping phenomenon in postural tachycardia syndrome A. Diedrich1, K. Sato1,2, S.R. Raj1, L. Diedrich3, V. Weimann1, I. Biaggioni1, D. Robertson1 1 Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Nashville, TN, USA; 2 Department of Clinical Pharmacology, Tokai University School of Medicine, Japan; 3 Department of Neurosurgery, Vanderbilt University, Nashville, TN, USA Background: We recently reported a high incidence of ‘‘non-dipping’’ (nocturnal drop in systolic blood pressure \10% from daytime) in patients with postural tachycardia syndrome (POTS). Previously, we found no relationship between autonomic baroreflex function and the non-dipping phenomenon. Here, we test the hypothesis that plasma volume regulation is different in ‘‘dipping’’ (DIPPER) and ‘‘nondipping’’ (NON-DIPPER) POTS. Methods: We recorded ambulatory BP and heart rate (HR) every 30 min for 24 h in patients with POTS (n = 28 female, age = 33 ± 10 years, BMI 22 ± 7 kg/m2, NON-DIPPERs/DIPPERs = 16/12). Following 3 days of a low-monoamine, caffeine-free diet containing 150 mEq sodium and 70 mEq potassium per day, we collected separate daytime and nighttime 12-h urines for urine catecholamines and volume. Plasma catecholamines, plasma renin activity (PRA), and aldosterone were also assessed. Total blood volume (TBV), plasma volume (PV), and red blood cell volume (RBCV) were determined by radioisotope dilution (DAXOR Corp) in 13 patients (NON-DIPPERs/DIPPERs = 7/6). Ideal volumes were calculated for each subject. Results: NON-DIPPERs had reduced PV (2.56 ± 0.34 vs. 2.92 ± 0.23 L, mean ± SD, p = 0.02) and a trend to lower TBV (3.74 ± 0.54 L vs. 4.27 ± 0.39 L, p = 0.05), but not RBCV (p = 0.14). NON-DIPPERs had greater deficits of TBV (-573 ± 279 vs. -33 ± 306 ml, p = 0.01), RBCV (-409 ± 120 vs. -203 ± 121 ml, p = 0.01) and PV (-164 ± 226 vs. +170 ± 200 ml, p = 0.01). DIPPERs did not have a PV deficit. Night-time urinary volume was significantly lower in NON-DIPPERs (668 ± 57 vs. 924 ± 350 ml, p = 0.03), but night-time urinary sodium excretion was not different (0.06 ± 0.04 vs. 0.07 ± 0.03 mE/mg, P = 0.38). Supine PRA (1.6 ± 0.5 vs. 1.3 ± 0.2 ng/ml/h; p = 0.55) and aldosterone (9.9 ± 2.2 vs. 7.1 ± 1.3 ng/ml; p = 0.59) were not different. Conclusions: This study suggests that blood volume is a predictor of dipping status in POTS patients. Non-dipping POTS patients have a blood volume deficit, whereas dipping POTS patients do not.

Regulation of the renin–angiotensin–aldosterone system in postural tachycardia syndrome H.I. Mustafa1,2,3, S.R. Raj1,2,3,4, B.K. Black1,2,3, S.Y. Paranjape1,2,3, I. Biaggioni1,2,3,4, D. Robertson1,2,3,4,5 1 Division of Clinical Pharmacology, 2 Paden Autonomic Dysfunction Center, 3 Departments of Medicine, 4 Pharmacology and 5 Neurology, Vanderbilt University School of Medicine

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Clin Auton Res (2010) 20:289–330 Background: Postural tachycardia syndrome (POTS) is characterized by excessive orthostatic tachycardia and significant functional disability. Previously, we reported that POTS patients had increases in plasma angiotensin II (Ang II) twice as high as normal subjects despite normal blood pressures. In this study, we assess systemic and renal hemodynamic and functional responses to Ang II infusion in patients with POTS compared with healthy controls. Methods: During a 3-day sodium controlled diet, we infused Ang II (3 ng/kg/min) for 1 h in POTS patients (n = 14) and healthy controls (n = 10) in the supine position. All study subjects were females, with similar ages for POTS and controls [30 ± 3 (mean ± SEM) vs. 27 ± 1 years; P = 0.24], baseline systolic blood pressure (SBP) (98 ± 2 and 98 ± 2 mmHg; P = 0.93), baseline diastolic blood pressure (DBP) (62 ± 1 and 63 ± 3 mmHg; P = 0.78) and baseline mean arterial pressure (MAP) (76 ± 1 and 76 ± 3 mmHg; P = 0.88) respectively. We measured the change from baseline in MAP, renal plasma flow (RPF), plasma renin activity (PRA), aldosterone and urine sodium in both POTS and controls. Results: POTS patients had a significantly blunted increment in mean arterial pressure (MAP) in response to Ang II infusion compared to controls (9 ± 1 vs. 13 ± 1 mmHg; P = 0.02) the increment in DBP (8 ± 1 vs. 11 ± 1 mmHg; P = 0.04) but not SBP (14 ± 2 vs. 12 ± 2 mmHg; P = 0.55) is blunted in POTS compared to control. Renal plasma flow (RPF) decreased similarly in POTS patients and controls (-169 ± 22 vs. -157 ± 14 mL/min/1.73 kg/m2; P = 0.70). Aldosterone increment in response to Ang II infusion was similar in POTS versus controls (18 ± 1 vs. 13 ± 3 pg/ml; P = 0.15). PRA decreased to a similar extent between the two groups (-0.85 ± 24 vs. 0.73 ± 0.29 ng/mL/h; P = 0.76). Urine sodium decreased to a similar extent in both POTS and controls (-52 ± 13 vs. -71 ± 22 mEq/g Cr; P = 0.44). Conclusions: Patients with POTS have blunted vasopressor response to Ang II. This impaired vasoconstrictive response might be exaggerated with upright posture, and may contribute to the subsequent orthostatic tachycardia that is the hallmark of this disorder.

Baroreceptor unloading augments peripheral and decreases central chemoreceptor sensitivity in postural tachycardia syndrome I. Taneja, D.A. Clarke, M.S. Medow, A.J. Ocon, J.M. Stewart Department of Pediatrics, New York Medical College, Valhalla, NY, USA Baroreflex unloading initiates increased minute ventilation (VE), decreased end-tidal carbon dioxide (ETCO2) and tachycardia in POTS. Since chemoreceptors modulate cardiorespiratory responses, we measured chemoreceptor sensitivity in 18 POTS (14F, 4M), 14 healthy controls (10F, 4M) 16–35 years old by exposing them to eucapneic hyperoxia–30% oxygen, eucapneic hypoxia (10% oxygen) and hypercapneic hyperoxia 30% oxygen + 5% carbon dioxide) in supine and HUT70 position. We measured heart rate (HR), mean arterial pressure (MAP), oxygen saturation, ETCO2, and VE. Chemoreflex sensitivity was ascertained by comparing hypoxic ventilatory response i.e. slopes determined from eucapneic hyperoxia–hypoxia to measure peripheral chemoreflex sensitivity (PCS), and hypercapnic ventilatory responseslopes between eucapneic hyperoxia–hyperoxic hypercapnia to measure central chemoreflex sensitivity (CCS). POTS and controls had similar PCS (0.2 ± 0.11 vs. 0.15 ± 0.05, p = ns). Baroreflex unloading by HUT70 did not increase PCS in controls (HUT vs. supine 0.19 ± 0.17 vs. 0.15 ± 0.05) but increased PCS for POTS (HUT vs. supine, 0.42 ± 0.38 vs. 0.2 ± 0.11, p \ 0.05). Also hypoxia during HUT, shifted the PCS for POTS upwards and to the right so that POTS had a higher minute ventilation and higher oxygen saturation than

Clin Auton Res (2010) 20:289–330 controls. In both POTS and controls, hypercapnia resulted in increases in VE. When supine, POTS had significantly lower CCS than controls (POTS vs. controls, 0.68 vs. 1, p \ 0.05). Baroreflex unloading did not change the hypercapnic ventilatory response in controls (HUT vs. supine, 1.04 ± 0.18 vs. 0.84 ± 0.27), but decreased the response in POTS (HUT vs. supine, 0.68 ± 0.34 vs. 0.49 ± 0.38, p \ 0.05) so that POTS had much lower hypercapnic ventilatory response than controls (HUT: POTS vs. controls, 0.49 ± 0.38 vs. 0.84 ± 0.27, p \ 0.05). POTS have higher peripheral chemoreflex and lower central chemoreflex sensitivity than controls. Baroreflex unloading increases peripheral chemoreflex sensitivity and decreases central chemoreflex sensitivity in POTS.

The effects of intense cardiovascular exercise on postural tachycardia syndrome: a physiologic success but a treatment failure C. Gibbons, R. Freeman Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA Background: Postural tachycardia syndrome (POTS) is characterized by an increase in heart rate in the upright position, accompanied by orthostatic intolerance. Recent reports have suggested that intense cardiovascular exercise may successfully treat POTS. Objective: To determine the effects of cardiovascular exercise on autonomic parameters, clinical events and symptoms in patients with non-neuropathic POTS. Methods: Twelve patients (8F) with non-neuropathic POTS participated in a minimum of 6 months of intense cardiovascular exercise (seated exercise on a recumbent bicycle for 3 months with progression to upright exercise) for 45+ min 6 days per week. Subjects underwent autonomic testing pre- and post-treatment with reports of clinical events (syncope) and assessment of symptoms (modified Likert scale) and global disability scores. Results: There were significant reductions in resting heart rate (75 ± 10 pre- vs. 59 ± 6 post-exercise, P \ 0.001), and standing heart rates (123 ± 15 pre- vs. 89 ± 8.8 post-exercise, P \ 0.001) after 6 months of exercise. The patients reported significantly lower numbers of syncopal spells in the 4 months after exercise compared to the 4 months before exercise (2.75 ± 1.6 pre- vs. 1.1 ± 1.2 post-exercise, P \ 0.001). There were no changes to patient reported lightheadedness or global impression of disability after 6 months of exercise. Discussion: After 6 months of intense cardiovascular exercise all subjects with POTS had improvement in cardiovascular parameters, ‘resolution’ of POTS by cardiovascular criteria in 50% and reduction in syncope frequency by 60%. Despite the hemodynamic improvements there were no reported improvements in lightheadedness or patient reported disability. Additional study is required to more comprehensively treat POTS.

Climate influence on emergency department syncope attendances: the role of temperature variability A. Galli1, F. Barbic2, M. Borella3, G. Costantino3, F. Perego4, F. Dipaola5, F. Casella2, P.G. Duca6, A. Diedrich7, S. Raj7, D. Robertson7, A. Porta8, R. Furlan2 1 Emergency Department, Vimercate Hospital, Vimercate, Milan, Italy; 2 Internal Medicine, ‘‘Bolognini’’ Hospital, Seriate, Bergamo, Italy; 3,4 Internal Medicine 2 and 3, ‘‘L. Sacco’’ Hospital, Milan, Italy; 5 Internal Medicine, Sesto S. Giovanni Hospital, Sesto S.Giovanni, Milan, Italy;

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Medical Statistics, Institute of Clinical Science ‘‘L.Sacco’’, Milan, Italy; 7 Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University, Nashville, TN, USA; 8 Department of Technologies for Health, Galeazzi Orthopaedic Institute, Milan; University of Milan, Italy Human pathophysiology suggests that heat may promote syncope during standing. We tested the hypothesis that the increase of ambient temperatures from January to July would be accompanied by an increased rate of syncope resulting in a higher frequency of Emergency Department (ED) visits. We also evaluated the role of maximal temperature variability in affecting syncope ED admittances. We included 770 of 2,775 consecutive subjects who were seen for suspected syncope at four ED between January and July 2004. This period was subdivided into three epochs: 23 January–31 March, 1 April–31 May and 1 June–31 July. In addition to tracking daily temperatures and heat indices, spectral techniques were used to analyze components of maximum temperature and syncope variability and to assess their relationship. There was no correlation between daily maximum temperatures and rates of syncope. Conversely, maximal temperature variability analysis showed a major fluctuation characterized by a 23-day period and two minor oscillations with 3and 7-day periods. This latter oscillation was linearly related to a similar 7-day fluctuation in ED visits for syncope. ED visits for syncope were lower in June and July when maximal temperature variability declined, although the maximal temperatures themselves were higher. A 7-day rhythm characterized both variability of daily maximal temperatures and ED visits for syncope, suggesting that climate variability may have a significant effect on the pattern of syncope occurrence. ED visits for syncope were not predicted by maximal daily temperature, but did correlate with increased temperature variability.

Hypertension, orthostatic hypotension and the risk of falls in a community-dwelling elderly population: the MOBILIZE Boston study A. Gangavati1,2, I. Hajjar1,2,3, L. Quach3, R.N. Jones2,3, D.K. Kiely3, P. Gagnon3, L.A. Lipsitz1,2,3 1 Department of Medicine, Division of Gerontology, Beth Israel Deaconess Medical Center; 2 Harvard Medical School; 3 Institute for Aging Research, Hebrew SeniorLife Background: Many physicians are concerned about precipitating orthostatic hypotension (OH) and increasing the risk of falls in elderly hypertensive patients by pharmacologically lowering their blood pressure (BP). Our aim was to investigate the relationships between uncontrolled hypertension, controlled hypertension, OH and falls in community-dwelling participants of the MOBILIZE Boston study (n = 722, mean age = 78.1 years). Methods: BP was measured by trained technicians using sphygmomanometry during resting supine conditions and after 1 and 3 min of standing. Systolic and diastolic OH at 1 and 3 min were defined as a 20 mmHg decline in systolic and 10 mmHg decline in diastolic BP, respectively, upon standing. Hypertension was defined as a BP =140/ 90 mmHg or receiving antihypertensives (controlled if BP \140/ 90 mmHg and uncontrolled if =140/90 mmHg). Falls data were prospectively collected using monthly postcard calendars. We defined fallers as those with at least 2 falls within 1 year of follow-up. Kaplan–Meier curves and multivariate Cox proportional hazard

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294 models were used to assess the risk of falls in those with OH, stratified by hypertension status. Results: OH was highest among the uncontrolled hypertensives [systolic OH at 1 min was 19% in uncontrolled hypertensives versus 5% in controlled hypertensives and 2% in non-hypertensives (p = 0.001)]. Those with uncontrolled hypertension and systolic OH at 1 min had an increased risk of falls (hazard ratio 2.6, 95% confidence interval 1.3–5.1). In contrast, neither controlled hypertension nor normotension, with or without OH, were associated with falls. Conclusions: Elderly people with uncontrolled hypertension and systolic OH at 1 min are at increased risk of falling within 1 year. Hypertension control, with or without OH, is not associated with an increased risk of falls in community-dwelling seniors. *Presented in part at American Geriatrics Society Annual Meeting, 2009.

Effects of age on vasomotor sympathetic activity and hemodynamic responses during neurally mediated syncope Q. Fu1,2, M.M. Galbreath1,2, T.B. VanGundy1, S.S. Jarvis1,2, R.L. Meier1, B.D. Levine1,2 1 Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX, USA; 2 The University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA Background: It was recently demonstrated that the mechanisms for syncope following prolonged exercise in athletes differ with age. We tested the hypothesis that advancing age affects sympathetic and hemodynamic responses during syncope in healthy sedentary humans. Methods: Twenty-five young (30 ± 2 [SE] years) and nine elderly (65 ± 1 years) subjects who had no history of recurrent syncope but had presyncope during 60° upright tilt were studied retrospectively. Muscle sympathetic nerve activity (MSNA), heart rate (HR), finger blood pressure (BP), and beat-to-beat hemodynamics (Modelflow) were measured. Results: During early tilting, BP was similar, HR and cardiac index (CI) were lower, while HR increases and CI decreases were smaller in the elderly than the young. MSNA increased in all subjects and was greater in the elderly. BP dropped progressively and then rapidly preceding presyncope; the drop rate was smaller in the elderly than the young (0.29 ± 0.06 vs. 0.62 ± 0.09 mmHg/s, P = 0.009). A presyncope, HR remained unchanged in the elderly but decreased in the young. The decrease in CI from 180 s before presyncope was much smaller in the elderly than the young (0.08 ± 0.03 vs. 0.60 ± 0.10 L/min/m2, P = 0.002). CI was markedly lower at presyncope in the elderly. TPR decreased in 16 young subjects and remained unchanged in 9; as a group, the decrease in TPR was similar between the young and elderly (0.13 ± 0.03 vs. 0.16 ± 0.05 MU, P = 0.600). TPR was greater in the elderly at presyncope. MSNA dropped rapidly at presyncope and the decrease from 180 s before presyncope was similar between the young and elderly (16 ± 4 vs. 19 ± 4 bursts/min, P = 0.596). MSNA was greater in the elderly at presyncope. Conclusions: A small fall in cardiac index/output with coincident vasodilatation contributes to syncope in the elderly. Conversely, in the young, syncope is caused by a moderate or marked fall in cardiac output with or without vasodilatation. Sympathetic withdrawal at presyncope occurs in both young and elderly individuals. Supported by NIH R01 (HL091078) and K23 (HL075283) grants.

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Muscle sympathetic nerve activity responses during prolonged post faint hypotension J. Rozenberg1, W. Wieling1, D. Jardine2 1 Department of Internal Medicine, Academic Medical Center, University of Amsterdam, The Netherlands; 2 Department of Internal Medicine, Christchurch Hospital, New Zealand Background: Following tilt-induced syncope, blood pressure recovers within 1 min after tilt back to the horizontal in the majority of patients. However in some, prolonged post-faint hypotension [PPFH] is observed, and we hypothesised that the mechanism is vasodilatation secondary to prolonged sympathetic withdrawal. Objectives: To derive total peripheral resistance [TPR] from continuous BP measurement and measure muscle sympathetic nerve activity [MSNA] during head-up tilt and PPFH. Methods: 19 patients [9 females, aged 43.7 ± 4 years] experiencing PPFH after tilt-back were studied. In 14 patients presyncope was provoked by 0.4 mg sublingual NTG, administered in the 60° head-up tilt position after a 20 min drug-free head-up tilt. Continuous BP [MAP] and heart rate [HR] were monitored. Stroke volume [SV], cardiac output [CO], and TPR were derived using modelflow. PPFH was defined as a systolic BP =100 mmHg for at least 2 min after tiltback. Variables measured at this time were compared to baseline [supine levels before tilt]. Results: MAP [94.5 ± 5 vs. 61.5 ± 3 mmHg], SV [81.8 ± 5 vs. 63.5 ± 4 ml/] and CO [5.5 ± 0.3 vs. 4.3 ± 0.3 l/min] remained decreased [p \ 0.001]. However TPR was maintained [1.2 ± 0.1 vs. 1.1 ± 0.2 arbitrary units] [p = 0.3] and MSNA indices increased [23.6 ± 2 vs. 45 ± 7 bursts/min and 25 ± 2 vs. 42.6 ± 6 units/min] [p \ 0.001]. Conclusions: There was no evidence for vasodilatation or MSNA withdrawal as possible mechanism for PPFH.

Sympathetic nerve protein abnormalities in patients with recurrent vasovagal syncope M. Esler, L. Guo, E. Lambert, G. Lambert, G. Vaddadi Baker IDI Heart and Diabetes Institute, Melbourne, Australia The neural pathophysiology of recurrent vasovagal syncope remains unclear. To investigate this, we applied complementary methods (multiunit sympathetic nerve recording, measurement of whole body norepinephrine spillover, analysis of sympathetic nerve proteins) in 33 patients (all \50 years) with recurrent vasovagal syncope and 18 healthy young adults. Patients with POTS were excluded. Sympathetic nerve tissue was accessed via subcutaneous vein biopsy, proteins were extracted then quantified (Western blotting), with antibodies detecting tyrosine hydroxylase (TH), the norepinephrine transporter (NET), dynamin I and VMAT2. Microneurography and measurement of norepinephrine spillover was done supine, then with head up tilting at 20°, 30° and 40°. We detect two clinical phenotypes among patient with recurrent vasovagal syncope, with either low supine systolic blood pressure (75–95 mmHg), or normal supine BP. Responses to tilting differed. In the low supine BP variant, despite their lower BP, sympathetic nerve firing paradoxically was higher than in healthy subjects throughout (P \ 0.05). In the normal supine BP variant sympathetic nerve firing increments with tilting were normal. With tilting the mean increases in norepinephrine spillover were 286 ng/min (normals), 156 ng/min (low supine BP variant), 16 ng/min (normal supine BP phenotype) (P \ 0.05 for both patient

Clin Auton Res (2010) 20:289–330 groups vs. normals). Thus, in the patient groups, there was a disjunction between increments in nerve firing and norepinephrine spillover (spillover increase much less than anticipated). Analysis of sympathetic nerve proteins perhaps provides an explanation. TH abundance was reduced in the low supine BP phenotype, 10–50% of normal (P \ 0.01), suggesting that norepinephrine synthesis was impaired. In the normal supine BP phenotype, abundance of NET was increased threefold, suggesting that enhanced norepinephrine reuptake had lowered norepinephrine spillover. It seems that these abnormalities in sympathetic nerve proteins, by reducing transmitter availability at adrenoceptors, were overriding the influence of increased sympathetic outflow with tilting, and compromising neural circulatory control.

Experience with droxidopa (NortheraTM) in a phase III multinational, placebo-controlled, parallel group, induction-design study to assess clinical benefit and safety in subjects with neurogenic orthostatic hypotension H. Kaufmann1, C. Mathias2, P. Low3, I. Biaggioni4, R. Freeman5, and the Droxidopa Study Group 1 New York University School of Medicine, New York, NY, USA; 2 Imperial College School of Medicine, London, United Kingdom; 3 Mayo Clinic, Rochester, MN, USA; 4 Vanderbilt University, Nashville, TN, USA; 5 Beth Israel Deaconess Medical Center, Boston, MA, USA Background: Neurogenic orthostatic hypotension (NOH) is a disabling feature of autonomic failure. NOH causes a variety of symptoms such as dizziness, vision disturbance, fatigue, generalized weakness and impairment or loss of consciousness. Symptomatic NOH results from impaired norepinephrine release from sympathetic nerve terminals leading to low blood pressure (BP) upon standing and tissue hypoperfusion. Droxidopa is a synthetic amino acid that can augment norepinephrine levels and improve standing BP thereby reducing the signs and symptoms of NOH. We are conducting a study to evaluate the clinical benefit, safety and tolerability of droxidopa to treat symptomatic NOH. Methods: This clinical trial is being conducted at 85 centers in Austria, Canada, Czech Republic, France, Germany, Italy, Romania, Ukraine, and USA. The study enrolled 142 patients between January 2008 and May 2010. It is projected that the complete sample size of 150 will be enrolled by the end of June 2010. Patients were confirmed to have symptomatic NOH of non-diabetic origin during a 2-week baseline evaluation period. At the time of writing, 39% of patients were diagnosed with Parkinson’s disease, 15% with multiple system atrophy, 33% with pure autonomic failure and 13% with other autonomic neuropathies. The population is equally distributed between females (51%) and males (49%) and is predominantly Caucasian (98%) with a mean age of 54 years. Patients enter an open-label, forced titration to determine an optimal treatment dose of droxidopa ranging from 100 mg T.I.D. to 600 mg T.I.D in 100 mg T.I.D. increments. No apparent trend has emerged to date with respect to dose as an approximately equal number of patients have been determined to be ‘‘optimally’’ treated at all dose levels. Following titration, patients are washed out of drug for 1 week. Subsequently, patients are randomized in a blinded fashion to either resume droxidopa treatment at their previously determined optimal dose or receive placebo (1:1). Study outcome measures are assessed 1 week later. Results/Conclusion: The clinical effectiveness of droxidopa will be discussed in terms of its impact on each of the 10 components of the Orthostatic Hypotension Questionnaire (OHQ), clinical global

295 impressions of disease severity and hemodynamics. The primary efficacy variable for the trial is the OHQ composite score, which measures the global impact of NOH in a patient’s life. Data currently available from the open-label titration on the first 120 patients indicates a highly significant average improvement in standing systolic blood pressure of 23 mmHg measured during clinical testing. Finally, the safety of droxidopa based on the occurrence of treatment-emergent adverse events, ECG, and laboratory findings across the study will be presented.

Preserved peripheral vasoconstriction during an orthostatic challenge in pure autonomic failure J.T. Groothuis1,3, D.H.J. Thijssen1,4, J. Deinum2, J.W.M. Lenders2,5, M.T.E. Hopman1 1 Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; 2 Department of Internal Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; 3 Department of Rehabilitation, St Maartenskliniek, Nijmegen, The Netherlands; 4 Research Institute for Sports and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom; 5 Department of Internal Medicine III, University Hospital Carl Gustav Carus Dresden, Germany Background: Baroreceptor mediated activation of the sympathetic nervous system and the consequent peripheral vasoconstriction is the key mechanism to maintain blood pressure during orthostatic challenges. The preserved leg vasoconstriction in individuals with autonomic failure due to a spinal cord injury, however, suggests that the sympathetic nervous system is not obligatory for peripheral vasoconstriction during orthostatic challenges. To further elucidate the role of the sympathetic nervous system in the regulation of peripheral vasoconstriction during orthostatic challenges, we assessed peripheral vascular responses during head-up-tilt in individuals with pure autonomic failure (PAF), who have peripheral autonomic failure due to postganglionic lesions and sympathetic denervation. Methods: We assessed leg vasoconstriction during 60° head-up tilt in 5 patients with PAF and 8 healthy controls. Blood pressure was measured continuously using a non-invasive finger arterial blood pressure device and superficial femoral artery blood flow was measured using duplex ultrasound. Leg vascular resistance was calculated as the arterio-venous pressure gradient divided by blood flow. Results: Baseline (supine) leg vascular resistance was not significantly different between PAF and controls (1.3 ± 0.4 and 1.1 ± 0.4 mmHg/ ml/min, respectively). Baseline mean arterial blood pressure in PAF was significantly higher than in controls (124 ± 19 and 95 ± 10 mmHg, respectively). During 60° head-up tilt, leg vascular resistance increased both in PAF (0.4 ± 0.4 mmHg/ml/min) and controls (0.3 ± 0.3 mmHg/ml/min), whilst the magnitude of increase was comparable (30 ± 22 and 31 ± 33%, respectively). Nonetheless, orthostatic hypotension was present in all PAF patients (average decrease in mean arterial pressure of 48 ± 34 mmHg). Conclusions: Our results demonstrate that PAF patients, who have peripheral autonomic failure due to postganglionic lesions and sympathetic denervation, demonstrate a preserved leg vasoconstriction during 60° head-up tilt. This indicates that the sympathetic nervous system is not obligatory for peripheral vasoconstriction during orthostatic challenges. Probably, local vasoconstrictor mechanisms compensate for the loss in sympathetic nervous system control.

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Relationship between muscle sympathetic nerve activity and aortic wave reflection characteristics in young men and women D.P. Casey, T.B. Curry, M.J. Joyner, N. Charkoudian, E.C. Hart Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA Background: Increased arterial stiffness is associated with higher levels of aortic wave reflection and elevations in aortic blood pressure. Recent evidence suggests a link between muscle sympathetic nerve activity (MSNA) and indices of arterial stiffness. Therefore, the goals of this study were to examine (1) the relationship between resting MSNA and characteristics of central aortic pressure wave reflection, and (2) the influence of sex on these relationships. Methods: In 36 subjects (20 F/16 M; 25 ± 4 years), we measured MSNA via peroneal microneurography. Additionally, non-invasive aortic pressure waveforms were synthesized from high-fidelity radial pressure waveforms obtained from applanation tonometry. Aortic blood pressure, augmentation index (AIx), wave reflection amplitude [i.e. aortic augmented pressure (AG)], and wasted left ventricular effort (Ew) were calculated from the generated aortic pressure waveform. Results: Resting MSNA (bursts/100 heart beats) was not associated with any of the aortic pressure wave reflection characteristics for all individuals included in the study. However and interestingly, there was a trend towards a positive relationship between MSNA and AIx (r = 0.47, P = 0.06) in men. Furthermore, MSNA in the men was positively related to AG (r = 0.57, P \ 0.05) and Ew (r = 0.62, P = 0.01). In striking contrast to men, we found that women demonstrated strong inverse relationships between MSNA and AIx (r = -0.63), AG (r = -0.59), and Ew (r = -0.58) (P \ 0.01 for all). Conclusion: Relationships between MSNA and indices of aortic vascular characteristics exist in men and appears to be modified by sex. These contrasting relationships may provide additional insight into previously reported differences in blood pressure regulating variables between the sexes. NIH HL-083947 (MJJ), NIH DK-082424 (TBC), AHA 2170087(ECH), and CTSA RR-024150.

Beta-2 adrenergic receptor gene variation and the cardiovascular response to orthostatic testing E.D. Wittwer1, N.D. Warner1, Z. Liu2, D.R. Schroeder1, A.M. Nadeau1, A.R. Allen1, C.J. Murillo1, J.H. Eisenach1 1 Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA; 2 Department of Cardiology, Medical School of Zhejiang University, Hangzhou, China Genetic variation in the beta-2 adrenergic receptor (ADRB2) influences cardiovascular regulation. A study in postural orthostatic tachycardia syndrome (POTS) patients at our institution found associations between decreased orthostatic diastolic BP and the Gly16 allele, and between increased orthostatic HR and the Glu27 allele. The purpose of this investigation was to test the hypothesis that ADRB2 gene variation affects cardiovascular and catecholamine responses to head-up tilt (HUT) in lean, normotensive young adults. In an ongoing protocol–ClinicalTrials.gov: ‘‘High Resolution Phenotyping in Healthy Humans,’’ subjects underwent brachial arterial cannulation and catecholamine sampling at rest and following 5 min 60° HUT. The arterial waveform was analyzed by Beatscope software and hemodynamic variables were indexed to body surface area (stroke volume index, SVI; cardiac index, CI; systemic vascular resistance index, SVRI). Analysis was limited to 120 Caucasians (72

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Clin Auton Res (2010) 20:289–330 females, 48 males, mean age ± SE: 25.6 ± 0.6, BMI 24.1 ± 0.2). HUT increased MAP and DBP (p \ 0.001) but did not change SBP. Additive and recessive statistical models for minor/major alleles Arg16/Gly demonstrated significant associations with HR and SVI at baseline, and HR, SVI, and plasma norepinephrine during HUT. Individuals with one or two copies of Gly16 (n = 85) displayed a smaller increase in DBP and SVRI, and a smaller decrease in CI and SVI (p \ 0.05 for all). For minor/major alleles Glu27/Gln, a dominant statistical model revealed an association between HR at baseline and during HUT, such that Gln27 homozygotes (n = 58) had greater HR at baseline and during HUT. Taken together, these results suggest a relationship between ADRB2 polymorphism and resting HR, with variation at position 16 more influential than position 27 for orthostatic cardiovascular control. Compared to Arg16 homozygotes, Gly16 carriers displayed reduced orthostatic DBP and SVRI which is consistent with historical findings of increased agonist-mediated vasodilation and possibly POTS.

Quantitative pilomotor axon-reflex test (QPART): a novel quantitative test of pilomotor function T. Siepmann, C. Gibbons, J. Lafo, C. Brown, R. Freeman Center for Autonomic and Peripheral Nerve Disorders, Beth Israel Medical Deaconess Center, Harvard Medical School, Boston, MA, USA Objectives: Despite the availability of measures of cutaneous sudomotor and vasomotor function, there are no measures of cutaneous pilomotor function. Piloarrector muscles are innervated by sympathetic adrenergic nerve fibers. The objective of this work was to develop a quantitative test of axon-reflex mediated pilomotor function (QPART). Methods: 6 healthy male volunteers were studied. Piloerection was stimulated on the right volar aspect of the forearm over a 1 cm diameter region by iontophoresis of 1% phenylephrine. Pilomotor function was measured by analyzing the silicon indentations of piloarrector muscles. Silicon impressions were made 30 min postiontophoresis. The indentations were scanned and quantified by size, number and location. To differentiate between the direct (transmitter mediated) and indirect (axon-reflex mediated) pilomotor response, measurements were repeated following application of 2% lidocaine gel 40 min prior to phenylephrine iontophoresis; lidocaine attenuates the axon-reflex mediated response. Results: In the area of phenylephrine application, 19.2 ± 11.5 indentations were counted without lidocaine and 17.8 ± 5.7 after lidocaine application. In the area surrounding the area of phenylephrine iontophoresis, 55.2 ± 16.5 indentations were counted without lidocaine and 36.5 ± 15.6 after lidocaine application. Conclusions: Pilomotor responses to phenylephrine were attenuated by lidocaine in the area surrounding the area of phenylephrine iontophoresis. Piloerection appears to be provoked both directly and indirectly through an axon-reflex that is attenuated by lidocaine. These data suggest that QPART may be a useful test to supplement the measures of small fiber function.

Altered leptin sensitivity for baroreflex suppression within the solitary tract nucleus of older SpragueDawley rats is associated with increased endogenous leptin tone A.C. Arnold, D.I. Diz Hypertension and Vascular Research Center, Wake Forest University School of Medicine, Winston-Salem, NC, USA

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Age-related elevations in leptin are associated with metabolic resistance to the anorectic hormone. However, leptin sensitivity for cardiovascular actions during aging is unknown. Thus, we determined the effect of bilateral solitary tract nucleus (NTS) leptin microinjection (500 fmol/ 60 nL) on baroreflex sensitivity (BRS) for control of heart rate (HR) in older (16–20 months) urethane/chloralose anesthetized Sprague-Dawley rats with known elevated circulating leptin levels. In contrast to the 63% reduction in young rats, leptin injection did not significantly reduce the BRS for bradycardia evoked by phenylephrine in old Sprague-Dawley rats (n = 5; 0.75 ± 0.12 baseline vs. 0.62 ± 0.15 ms/mmHg after leptin). We hypothesized that the loss of sensitivity in old Sprague-Dawley rats is associated with endogenous suppression of the baroreflex by elevated leptin levels. Indeed, NTS administration of a leptin triple mutant antagonist improved the bradycardic BRS in old Sprague-Dawley rats at 60 min after injection (n = 5; 0.75 ± 0.12 baseline vs. 1.11 ± 0.30 at 10 min vs. 1.87 ± 0.32 at 60 min vs. 1.20 ± 0.54 ms/mmHg at 120 min; p \ 0.05), with no effect in young Sprague-Dawley rats with normal circulating leptin. Interestingly, transgenic rats with low brain angiotensinogen (ASrAOGEN) maintained sensitivity to leptin-mediated BRS impairment during aging (n = 5; 1.40 ± 0.09 baseline vs. 0.72 ± 0.12 ms/mmHg after leptin) in the face of lower circulating leptin levels. The present findings suggest that (1) normal aging is associated with resistance to the baroreflex actions of exogenous leptin within the NTS; (2) elevated leptin within the NTS provides tonic suppression to the BRS during aging; (3) long-term reductions in the brain renin-angiotensin system preserve leptin sensitivity for baroreflex suppression during aging. Collectively, these studies provide novel insight into potential mechanisms underlying age-related baroreflex dysfunction.

targeted directly to the cardiac vagus nerve in the pig, can increase cardiac baroreflex sensitivity, facilitate Ach release, and bradycardia. In the hypertensive rat or in the infarcted guinea-pig heart, this gene transfer strategy can restore parasympathetic responsiveness and improve short term survivability. Moreover, targeted gene transfer of nNOS with a noradrenergic cell specific adenoviral vector increases the bioactivity of nNOS and cGMP, resulting in decreases in cAMP levels in cardiac sympathetic nerves that is linked to decreased calcium entry and noradrenaline release in the normotensive rat. Placing nNOS directly into sympathetic nerves or pacemaking cells in hypertensive rats reduces sympathetic and beta adrenergic hyper-responsiveness to the normal responses seen in the normotensive WKY rat. When all results are taken together they demonstrate good proof of principle that manipulation of cardiac-neural nNOS levels can have potentially profound effects on cardiac excitability. However, whether this translates to effect long term survivability to several cardiac pathologies with established dysautonomia is not known, nor are the detailed cellular pathways underpinning the action of cyclic nucleotide regulation on cardiac neurotransmission. In addition to NO-cGMP linked pathways, both neuropeptide Y (NPY) and natriuretic peptides (BNP) also couple to cyclic nucleotide regulation of cardiac autonomic transmission. A part of vagal impairment in myocardial disease may well arise from the indirect inhibition of the vagus caused by enhanced co-transmission of NPY which is associated with excessive sympathetic activation. There is now direct evidence showing how NPY regulates Ach release via presynaptic Y2 receptor signalling in cholinergic neurons and that targeting this cross-talk pathway by inhibiting pre-synaptic Y2 receptors on these neurons may be therapeutically beneficial. Targeting receptor operator cGMP pathways could conceivably be beneficial over a longer period of time.

Friday, November 5, 2010

Sympathetic cardiovascular control functional mapping of the ventrolateral medullary surface in humans with microneurography and circulatory monitoring

Oral Presentations Linking cyclic nucleotide regulation to the neural control of cardiac excitability: implications for therapeutic targeting D.J. Paterson Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK Several cardiovascular pathologies involving oxidative stress are known to impair cyclic nucleotide coupled pathways linked to regulation of intracellular calcium in the autonomic nervous system at the end organ level. In particular, nitric oxide (NO) derived from neuronal nitric oxide synthase (nNOS) facilitates cardiac parasympathetic neurotransmission, and inhibits sympathetic transmission, via cGMP dependent modulation of neuronal calcium levels that in turn regulates exocytosis. In hypertensive rats, and following acute myocardial infarction in the guinea-pig, sympatho-vagal control of cardiac excitability is impaired leading to enhanced release of noradrenaline and diminished vagal responsiveness. In humans, single-nucleotide polymorphisms in nNOS activator protein (CAPON) have been identified as a key correlate for prolonged QT interval which is a marker for sudden death. However, a significant site of interest for this mutation may reside in cardiac neural tissue, and that impaired transmission could amplify the electrical phenotype of abnormal repolarization. Whilst NO donors and cGMP analogues may be beneficial because they augment vagal-induced bradycardia or conversely inhibit cardiac sympathetic neurotransmission, their pharmacological targeting is relatively non-specific with the actions being short lived. Emerging evidence has shown that adenoviral vector mediated nNOS gene transfer into cholinergic intracardiac ganglia in the mouse, rat and guinea-pig, or when

C.M. Welzig, S.J. Patel Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA Introduction: The ventrolateral medulla contains sympathoexitatory neurons that are part of the central control system involved in the longterm regulation of arterial blood pressure (ABP). In humans, the exact location and function of these medullary neuronal aggregates is being investigated. Elevated sympathetic vasomotor outflow has been implicated in the pathogenesis of neurogenic hypertension by arterial compression. In the present study, we aimed to map areas of the ventrolateral medullary surface (VLMS) that modulate sympathetic outflow and cardiovascular parameters subsequent to electrical stimulation. Methods: Normotensive patients undergoing posterior fossa surgery were subjected to continuous monitoring including the ABP waveform, ECG, heart rate (HR), computed cardiac output and systemic vascular resistance. Muscle sympathetic nerve activity (MSNA) was obtained from the peroneal nerve. Using a 3-mm spaced reference grid of stimulation points along the VLMS, we applied electrical impulse trains of 15 s duration through a bipolar electrode (100 Hz, 0.1 ms pulses, 1.5–5 mA). Return to baseline conditions was allowed between stimulations if an ABP, HR or MSNA response was observed. Cardiovascular and MSNA changes in response to stimulation were normalized and averaged for each reference point. Results: Mapping results identified a region of the rostral VLMS that responds to stimulation with a significant elevation in ABP and MSNA (P \ 0.05). In addition, an area of the caudal VLMS demonstrated a decrease in both ABP and MSNA (P \ 0.05) after stimulation. Conclusions: We have established that it is feasible to obtain MSNA in the challenging conditions during surgery and to safely apply

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298 electrical stimulation to the VLMS. We were able to compute a first map of the VLMS indicating regions sensitive to stimulation with either increase or decrease of MSNA and ABP. Mapping of such areas may facilitate the development of diagnostic algorithms for the identification of patients that are likely to respond to microvascular decompressive surgery with a clinically significant and lasting reduction in blood pressure.

Sympathetic neural responsiveness to increasing and decreasing arterial pressures in young and older humans: the role of baseline nerve activity E.C. Hart1, B.G. Wallin2, M.J. Joyner1, T.B. Curry1, N. Charkoudian3 1 Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA; 2 Institute of Neuroscience and Physiology, The Sahlgren Academy at Gothenburg University, Sweden; 3 Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA Background: Sympathetic neural activity appears to be more responsive to decreasing diastolic blood pressure (DBP) compared to increasing DBP in young men and women. This has been attributed to differences in the response of the central nervous system to afferent baroreceptor input when DBP falls or rises. We wondered whether this differential sensitivity varies based on sex and age. Methods: We investigated whether baroreflex control of burst occurrence during resting increasing and decreasing DBP was related to baseline muscle sympathetic nerve activity (MSNA) in 35 young men (26 ± 4 years), 17 young women (25 ± 3 years) and 14 older men (60 ± 6 years). MSNA was measured using peroneal microneurography and baroreflex control of burst incidence was evaluated using threshold analysis. Results: On average baroreflex control of burst incidence was more sensitive to decreasing DBP than increasing DBP in young men (6.9 ± 3.1 bursts/100 hb/mmHg vs. -4.8 ± 2.5 bursts/100 hb/mmHg, P \ 0.05) and women (-7.4 ± 3.0 bursts/100 hb/mmHg vs. -5.2 ± 1.9 bursts/100 hb/mmHg, P \ 0.05). In older men, the average baroreflex sensitivity was similar when DBP was increasing (–5.4 ± 2.5 bursts/100 hb/mmHg) and decreasing (-5.4 ± 2.5 bursts/100 hb/ mmHg; P [ 0.05). Investigation of individual variability in these data provided further insights into baroreflex function. Individual differences (deltas) between falling and rising baroreflex slopes correlated with baseline MSNA in young (r = 0.53, P \ 0.05) and older men (r = 0.69, P \ 0.05). Interestingly, this relationship was not observed in women (r = 0.14, P [ 0.05). Conclusions: Individual differences in responsiveness of sympathetic burst occurrence to increasing and decreasing DBP were related to baseline MSNA in young and older men, but not in young women. In older men, the attenuated baroreflex sensitivity to decreasing DBP in relation to the baroreflex sensitivity to increasing DBP may be related to high baseline nerve activity.

Elderly hypertensive women have lower cardiovagal but similar sympathetic baroreflex sensitivity compared with elderly hypertensive men Q. Fu1,2, M.M. Galbreath1,2, T.B. VanGundy1, S.S. Jarvis1,2, R.L. Meier1, S. Shibata1,2, W. Vongpatanasin2, B.D. Levine1,2 1 Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX, USA; 2 The University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA

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Clin Auton Res (2010) 20:289–330 Background: Previous studies have found that cardiovagal baroreflex sensitivity is reduced in hypertensive patients, and is much lower in middle-aged hypertensive women compared with age-matched hypertensive men. We tested the hypothesis that not only cardiovagal but also sympathetic baroreflex sensitivity is lower in elderly hypertensive women than in elderly hypertensive men. Methods: Fifteen untreated hypertensive women (68 ± 6 [SD] years) and eighteen age-matched hypertensive men (70 ± 4 years) were studied. Twenty-four hours ambulatory blood pressure monitor (ABPM) was performed prior to testing. Blood pressure, heart rate, and muscle sympathetic nerve activity (MSNA) were recorded continuously during a Valsalva maneuver (40 mmHg, 20 s) in the supine position. Cardiovagal baroreflex sensitivity was assessed using the RRI–systolic pressure correlation during early phase II (i.e., a hypotensive stimulus) and phase IV (i.e., a hypertensive stimulus). Sympathetic baroreflex sensitivity was assessed by relating all sympathetic bursts occurring during the 20-s straining period of the Valsalva maneuver to the maximum fall of diastolic pressure. Results: Twenty-four hours ABPM results were similar between the groups (142 ± 9/81 ± 6 in men vs. 140 ± 7/74 ± 8 mmHg in women, P [ 0.05). Elderly hypertensive women had reduced cardiovagal baroreflex sensitivity compared with elderly hypertensive men during both hypotensive (2.02 ± 0.66 vs. 3.70 ± 1.93 ms/mmHg, P = 0.001) and hypertensive stimuli (5.47 ± 2.11 vs. 7.54 ± 3.88 ms/mmHg, P = 0.075). However, sympathetic baroreflex sensitivity did not differ between the groups (-1.40 ± 1.02 in men vs. -1.47 ± 0.89 bursts/20 s/mmHg in women, P = 0.447). Conclusions: Elderly hypertensive women have lower cardiovagal but similar sympathetic baroreflex sensitivity compared with elderly hypertensive men. It is possible that the marked impairment of the cardiovagal baroreflex may contribute to the poor blood pressure control in these women. Supported by NIH R01 grant (HL091078).

Concurrent recording of spontaneous skin sympathetic nerve activity and whole-brain fMRI signal intensity in awake human subjects V.G. Macefield1,2, C. James1, L.A. Henderson2 1 School of Medicine, University of Western Sydney, Australia; 2 Prince of Wales Medical Research Institute, Australia; 3 Department Anatomy and Histology, School of Medical Sciences, University of Sydney, Australia Introduction: We have previously shown that it is possible to record sympathetic nerve activity—via microneurography—whilst performing functional magnetic resonance imaging (fMRI) of the brainstem in awake human subjects (Macefield and Henderson 2010). Although sympathetic nerve activity to muscle is involved in the regulation of blood pressure, that to skin is involved in thermoregulation and emotional expression. In the present study, we attempted to identify areas within the brain that may contribute to the generation of spontaneous skin sympathetic nerve activity (SSNA) at rest. Methods: SSNA was recorded from the common peroneal nerve in 10 subjects. Gradient echo, echo-planar fMRI was performed using a 3T scanner (Philips Achieva). 200 volumes (46 axial slices, TR = 8 s, TE = 40 ms, flip angle = 90°, raw voxel size = 1.5 mm3) were collected in a 4 s-ON, 4 s-OFF protocol. Total sympathetic burst amplitudes were measured from the RMS-processed mean voltage amplitude during the final 3 s of the 4 s-OFF period. Blood oxygen level dependent (BOLD) changes in signal intensity (SPM5: random effects, minimum cluster size 10 voxels, corrected false discovery rate p \ 0.05) were measured during the subsequent 4 s-ON period.

Clin Auton Res (2010) 20:289–330 Results: SSNA was positively correlated to signal intensity bilaterally in both the ventral hypothalamus and cerebellar vermis. There were no apparent correlations between SSNA and areas above the hypothalamus. Conclusions: We have shown that neuronal activity in the ventral hypothalamus and the cerebellar vermis covaries with spontaneous fluctuations in SSNA, suggesting that ongoing fluctuations in SSNA at rest may simply be a reflection of the underlying thermoregulatory demands rather than higher-order (emotional) processes. Reference: Macefield VG, Henderson LA (2010) Real-time imaging of the medullary circuitry involved in the generation of spontaneous muscle sympathetic nerve activity in awake subjects. Human Brain Mapping 31: 539–549

The role of reactive oxygen species (ROS) in the control of skin blood flow response to local heat in healthy subjects M.S. Medow1,2, N. Bamji1, D. Clarke1, A.J. Ocon2, J.M. Stewart1,2 Department of Pediatrics, New York Medical College, Hawthorne, NY, USA Local cutaneous heating produces vasodilation that is largely NOdependent. We showed that Angiotensin II (Ang-II) attenuates the local heat response by an AT1R-dependent mechanism, reversible with the antioxidant ascorbate indicating oxidative stress. Reactive oxygen species (ROS) produced by Ang-II predominantly employ the NADPH oxidase and xanthine oxidase (XO) pathways. To determine whether these mechanisms pertain to skin, we measured the effects on the cutaneous local heating response of oxidase pathway inhibition with and without Ang-II, using Apocynin to inhibit NADPH oxidase and Allopurinol to inhibit XO. We also investigated the effects of superoxide inhibition with Tempol and hydrogen peroxide and cyclooxygenase (COX) inhibition with Ebselen. Studies were performed in eight healthy volunteers aged 24.5–29.5. We heated the skin of the calf to 42°C and measured local blood flow to assess the percentage of maximum cutaneous vascular conductance (%CVCmax). We re-measured this response while perfusing Allopurinol, Apocynin, Ebselen and Tempol through individual microdialysis catheters. This was then repeated with Ang-II. Tempol and Apocynin had no effect on the heat response. Allopurinol enhanced the entire response (153% of heat-alone), while Ebselen suppressed the heat plateau (69% of heat-alone). Ang-II alone resulted in significant attenuation of the entire heat response (60%). When added to Ang-II, Allopurinol partially reversed the Ang-II attenuation, but did not cause the enhancement seen with Allopurinol and heat alone. The heat response with Ebselen and Angiotensin II were similar to that with heat and Ebselen; Ebselen reversed the attenuation caused by Ang-II. Apocynin and Tempol were each able to partially reverse the heat attenuation caused by Ang-II. This suggests that ROS produced by Ang-II via the NADPH oxidase and xanthine oxidase (XO) pathways, as well as local prostanoids control basal cutaneous blood flow as well as the response of skin to the application of local heat.

Novel role for the peripheral chemoreceptors in regulating blood glucose E.A. Wehrwein, R. Basu, A. Basu, T.B. Curry, R. Rizza, M.J. Joyner Mayo Clinic, Rochester, MN, USA

299 The peripheral chemoreceptors in the carotid bodies are well known for sensing arterial PO2 and regulating respiration. In isolated carotid glomus cells and animal models, there is evidence that the carotid bodies also directly sense hypoglycemia and play a role in the counterregulatory response to hypoglycemia. The present study was undertaken to test the hypothesis that the human carotid bodies can also sense hypoglycemia and mediate the counterregulatory hormone response to low blood glucose. Four healthy adult males and females (M/1; F/3) each underwent two 180 min hyperinsulinemic (2 mU/kg/ min), hypoglycemic (60 mg/dl) clamps separated by 7 days randomized to normoxia or hyperoxia (which desensitizes the carotid body glomus cells to hypoglycemia). Plasma glucose concentrations were the same during normoxia or hyperoxia at baseline (5.46 ± 0.17 vs. 5.64 ± 0.13 lmol/ml) and during the clamp (3.39 ± 0.07 vs. 3.75 ± 0.09 lmol/ml) (p [ 0.05). However the amount of glucose infused to maintain hypoglycemia was 51% higher during hyperoxia than normoxia (28.2 ± 0.15 vs. 42.7 ± 0.65 lmol/kg/min; p \ 0.01). Counterregulatory hormones released in response to hypoglycemia (glucagon, cortisol, growth hormone, epinephrine and norepinephrine) were significantly suppressed during the clamp on the hyperoxia day as compared to normoxia (p \ 0.05). Taken together, these data indicate that the carotid bodies play an important and largely underappreciated role in mediating the counterregulatory response to hypoglycemia in humans.

Modulation of the ventilatory baroreflex by changes in chemoreceptor activation D.A. Clarke, A.J. Ocon, I. Taneja, M.S. Medow, J.M. Stewart Department of Pediatrics, New York Medical College, Hawthorne, NY, USA Baroreflexes detect BP changes producing cardiovagal, sympathetic vasoconstrictive, and adrenal medullary responses. Less often considered are centrally mediated ventilatory responses. This ventilatory baroreflex produces changes in ventilation inversely related to changes in arterial pressure,. Whether chemoreceptor activation affects the ventilatory baroreflex is not known. Therefore, we investigated the relationship of ventilation to BP using bolus administration of 100 lg sodium nitroprusside, followed 60 s later by 150 lg of phenylephrine (modified Oxford method). 7 healthy subjects thus underwent baroreceptor unloading and loading under the following steady conditions of chemoreflex activation: room air (RA), 30% oxygen (hyperoxia), 10% oxygen (hypoxia) and 30% oxygen + CO2 (hypercapnia to 55–60 Torr). Mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), expiratory minute ventilation (VE), respiratory rate (RR) and end tidal CO2, were recorded. Hypercapnia increased MAP by 20% and VE by 287% above room air. Hypoxia and hyperoxia did not affect MAP but increased VE by 136 and 138%, respectively. Baroreflex unloading and loading produced the following findings: during RA, MAP decreased by 18 with 102% increase in VE; during hypoxia MAP decreased by 30 with 110% increase in VE. During Hyperoxia, MAP decreased by 18% and VE increased by 98%. During Hypercapnia, MAP decreased by 11% with 126% increase in VE, yielding a total 413% increase in ventilation from baseline. RR followed a similar trend as ventilation. At RA, RR increased by 5% from baseline, increased 5% during Hypoxia, increased 9% during Hyperoxia and increased 30% during Hypercapnia. CO increased by 44% during hypercapnia. There were no significant differences in HR. Ventilatory baroreflex sensitivity measured by the change VE to change in pressure was unaffected by hypoxia or hyperoxia but was markedly enhanced by hypercapnia. The inverse

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300 relationship between blood pressure and ventilation is evident under all conditions of chemoreflex stimulation.

Cardiovascular responses during acute intermittent apnea in normotensive and spontaneously hypertensive conscious rats S.L. Cravo1, M.V. Rossi1, T.A. Silva1, S. Tufik2, G.H.M. Schoorlemmer1 1 Department of Physiology, Federal University of Sao Paulo, Sao Paulo, Brazil; 2 Department of Psychobiology, Federal University of Sao Paulo, Sao Paulo, Brazil We designed new methods to induce obstructive apnea and to measure breathing effort in conscious rats. To induce apnea, we used a balloon-tipped catheter placed inside a rigid Teflon tube (6 mm long, i.d. 1.8 mm, o.d. 2.2 mm) that was implanted in the trachea. The catheter was led subcutaneously to the back of the neck, and injection of water through the catheter induced apnea without inducing pain. Breathing effort was measured with a balloon-tipped catheter (4 mm diameter, with ultrathin, non-elastic wall), that was lowered along the trachea into the mediastinum. Both implants were well tolerated for months, and the tracheal implant, left deflated, had little effect on resting breathing effort (intrathoracic pressure swing increased from 4.1 ± 0.4 mmHg before to 6.1 ± 0.2 mmHg, 4 weeks after tracheal implant, n = 3). Arterial SO2 fell from 97.7 ± 0.1 to 80.1 ± 2.1% during 15 s of apnea, with bradycardia (373 ± 23 to 141 ± 18 bpm), increased breathing effort (6.3 ± 0.2 to 38.5 ± 6.0 mmHg), and pressor responses (115 ± 3 to 133 ± 5 mmHg). Values returned to baseline within a few second after the end of apnea. SHR had increased pressor responses (167 ± 11 to 208 ± 10 mmHg), whereas bradycardia was similar (413 ± 20 to 184 ± 16 bpm), but a more rapid onset of bradycardia was observed. Apnea-induced bradycardia was blocked by methylatropine (1 mg/kg, i.v.), and the pressor response was blocked by prazosin (1 mg/kg, i.v.). Ligation of the carotid body arteries did not affect apnea-induced bradycardia, pressor responses, and breathing effort. In conclusion, these new methods show many similarities between the effects of apnea in rats and human patients. Results obtained in SHR suggest an increased reactivity and sympathetic activation during apnea.

Autonomic dysregulation precedes and predicts cardiac dysfunction and mortality in a mouse model of muscular dystrophy R. Sabharwal1, R.M. Weiss1, K. Zimmerman2, M.W. Chapleau1,2 1 University of Iowa, Iowa City, IA, USA; 2 Veterans Affairs Medical Center, Iowa City, IA, USA Mutations in sarcoglycans and other subunits of the dystrophin–glycoprotein complex cause muscular dystrophy and dilated cardiomyopathy (DCM). We reported previously that autonomic and locomotor functions are impaired while cardiac function is normal in young sarcoglycan delta deficient (Sgcd-/-) mice (FASEB J, 2008). In this study, we tested the hypothesis that autonomic dysregulation predicts left ventricular (LV) dysfunction and mortality in Sgcd-/mice at older ages. Cardiac function (echocardiography), blood pressure and heart rate (HR) (telemetry), spontaneous baroreflex sensitivity (BRS), and cardiac sympathetic and vagal tone (HR responses to propranolol and atropine) were measured at 4-week

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Clin Auton Res (2010) 20:289–330 intervals between 10 and 75 weeks of age in Sgcd-/- (n = 8) and control (n = 6) mice. Survival curves (Kaplan–Meier) were generated from mouse colony birth/death records. Autonomic regulation was impaired (P \ 0.05), while LV ejection fraction (EF) and end diastolic volume (EDV) were normal in Sgcd-/- mice at 10–30 weeks of age. The defining features of DCM (decreased EF, increased EDV) became evident between 30 and 75 weeks of age in Sgcd-/- mice and were accompanied by worsening of autonomic function and premature death (P \ 0.05). Increased sympathetic tone at a young age predicted decreased EF (r = 0.957) and increased EDV (r = 0.819) at an older age in Sgcd-/- mice (n = 6, P \ 0.05). In contrast, decreased vagal tone and BRS failed to predict cardiac dysfunction but were associated with reduced lifespan (vagal tone, r = 0.727; BRS, r = 0.832, n = 4). We conclude: (1) Sgcd-/mice exhibit autonomic dysregulation at a young age when cardiac function is normal. (2) Autonomic and cardiac functions progressively worsen with age in Sgcd-/- mice leading to premature death. (3) Increased sympathetic tone predicts later cardiac dysfunction, whereas decreased vagal tone and BRS are associated with increased mortality. (4) The results suggest that autonomic dysregulation contributes to the pathogenesis of DCM in muscular dystrophy.

Baroreflex failure makes patients super susceptible to volume overload and predisposes patients to pulmonary edema in the absence of left ventricular systolic failure K. Sunagawa Department of Cardiovascular Medicine, Kyushu University, Fukuoka, Japan Background: A small amount of volume reduction by diuresis often rapidly resolves pulmonary edema in patients with heart failure with preserved ejection fraction (HFpEF). Major risk factors of HFpEF such as aging and hypertension promote atherosclerosis/arteriosclerosis (SCLEROSIS). Since baroreflex is a powerful regulator of intravascular stressed blood volume and SCLEROSIS significantly impairs baroreceptor transduction, we hypothesized that SCLEROSIS-induced baroreflex failure plays a pivotal role in the pathogenesis of HFpEF. Method and results: In 5 anesthetized Sprague-Dawley rats with normal left ventricular (LV) function, we isolated bilateral carotid sinuses and controlled carotid sinus pressure (CSP) by a fast servo-controlled piston pump. We cut aortic depressor nerves bilaterally. We mimicked the normal baroreflex (NORMAL) by matching the CSP to arterial pressure and the baroreflex failure (FAILURE) by keeping CSP at a constant value irrespective of arterial pressure. We infused dextran (infused volume, V) at rates of 1–4 ml/kg every minute stepwise until left atrial pressure (LAP) reaches 14–16 mmHg. We obtained the LAP-V relation (LAPVR) under NORMAL and FAILURE. We fitted a monoexponential curve to the LAPVR and estimated an infused V (critical V) at which LAP reaches 20 mmHg (high enough to cause pulmonary edema). Critical V was 17.22 ± 1.91 ml/kg under NORMAL, whereas markedly decreased to 11.16 ± 1.58 ml/kg under FAILURE. The difference in critical V (DV) estimated for 70 kg patients exceeds 400 ml. Since baroreflex gain in normal subjects is considered to be a few times higher than that obtained from anesthetized animal experiments, DV in patients may well be at least a few times higher ([1,000 ml). Conclusion: Baroreflex failure makes patients extremely sensitive to volume overload and susceptible to pulmonary edema. Since atherosclerosis induces systolic hypertension and LV hypertrophy, concomitant increases in LV diastolic stiffness further predispose patients to heart failure even without sizable systolic dysfunction.

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Mechanism and durability of blood pressure reduction with catheter-based denervation in essential hypertension M. Esler1, M. Schlaich1, R. Whitbourn3, A. Walton2, H. Krum2 1 Baker IDI Heart and Diabetes Institute, Melbourne, Australia; 2 Alfred Hospital, Melbourne, Australia; 3 St Vincents Hospital, Melbourne, Australia Renal sympathetic nervous activation is seminal in the development of essential hypertension. Renal norepinephrine spillover is elevated 2–3-fold, on average. Renal denervation often normalizes the blood pressure in experimental hypertensions. Catheter-based renal sympathetic denervation was shown to substantially reduce blood pressure in a cohort of 45 patients with resistant hypertension (systolic BP [160 mmHg on 3 or more drugs), reported in the Lancet. Renal norepinephrine spillover measurements confirmed denervation. We now report on the durability of the antihypertensive effect, with follow-up in these and similar patients (117 in total) treated in Australia, Europe and the United States. Mean age was 57 ± 11 years, 40% were female, 33% diabetic, 22% with coronary artery disease. Mean baseline office BP was 176/98 mmHg, mean of 5.0 anti-HTN medications. The bilateral procedure lasted a median of 38 min. One renal artery dissection occurred, successfully treated by stenting. Postprocedure office BPs were reduced by 20/11, 24/10, 24/12, 25/12, 29/ 17 and 33/14 mmHg at 1, 3, 6, 12, 18 and 24 months respectively. An unexpected result was inhibition of extra-renal sympathetic activity, total norepinephrine spillover and muscle sympathetic nerve activity (microneurography) falling by 20–70% in individual patients. This probably resulted from ablation of renal afferent nerves, which project centrally to stimulate sympathetic outflow. Could catheter-based renal denervation perhaps cure milder hypertension? This speculation remains untested. For the procedure to be applied in mild hypertension, the BP lowering would need to be durable, and a high level of safety would be mandatory. Efferent sympathetic nerve re-growth is possible, but no cancelling out of the antihypertensive effect is evident at 2 years. It is probable that the procedure ablates renal afferent nerves, inhibiting sympathetic outflow and contributing to the blood pressure lowering. Any blood pressure reduction attributable to renal deafferentation is likely to be permanent.

Saturday, November 6, 2010 Oral Presentations What is the mechanism for circadian rhythms of body temperature?

301 regulate Tb responses to heating and cooling by means of at least two areas, the median and dorsolateral preoptic nuclei. Lesions in both, but not either area alone, cause prolonged elevation of Tb. But surprisingly, preoptic lesions have not been found to alter the daily cycle of Tb. Another site that regulates Tb is the dorsomedial nucleus/dorsal hypothalamic area. Lesions here lower Tb by about half a degree, but do not affect the daily cycles. There are some dorsal subparaventricular inputs to the median eminence, and we wondered whether there could be an endocrine component contributing to Tb cycling, but found that there was no difference in daily cycles of Tb in hypophysectomized animals, whether entrained to a light:dark cycle or free-running in constant darkness. A third site that is thought to be important in Tb regulation is the region of the raphe pallidus (RPA). The RPA is thought to send projections to the sympathetic preganglionic neurons that regulate both activation of brown adipose tissue (BAT) and cutaneous vasoconstrictor blood vessels, resulting in increased Tb. Animals with lesions of the RPA do not show elevation of Tb in response to cold challenge or immune stimuli that produce fever. But cell-specific lesions of the RPA also did not affect the diurnal cycles of Tb. This raised the question of whether the sympathetic nervous system was needed at all for the daily cycle of Tb. We studied rats with spinal transections at T2-3, in which we had implanted temperature telemetry transmitters. Surprisingly, these animals had daily cycles of Tb that were similar to intact animals in L:D. However, they had some sympathetic response intact (at the T1-2 level), and in addition, they had normal daily cycles of feeding. We wondered whether the food might cause local changes in gut perfusion (to absorb the food, thus shifting blood flow to deep vascular beds during the waking period). So, we also food deprived the rats for 48 h. This failed to eliminate the daily cycle of Tb. To determine if the last remaining bit of T1-2 sympathetic system was causing the daily cycles of Tb, we next gave rats iv doses of anti-DBH-saporin, a conjugate that kills all DBH producing neurons in the sympathetic ganglia. These animals had profound ptosis and meiosis, and cardiac sympathetic denervation was confirmed post-mortem. Nevertheless, the animals had a daily cycle of Tb that was about 60% of the amplitude of unlesioned animals in both 12:12 h light–dark (LD) or continuous dark (DD) cycles. However, because the animals had other activities that proceeded on a 24 h freerunning cycle even in the dark, we placed the animals in a forced desynchrony paradigm, with a 14:14 LD cycle, which animals cannot adapt to. On this cycle, the daily rhythms of Tb were finally nearly silenced in successfully sympathectomized rats. In summary, while the sympathetic nervous system plays a large role in determining Tb, the daily cycle of Tb depends upon many other factors, probably including the blood flows caused by daily cycles of feeding and the heat created by muscle activity during the active cycle. The sympathetic flow probably is responsible for the non-behavioral components of Tb cycling, but even in its absence, it is possible for animals (and probably humans) to maintain a reasonably good daily cycle of Tb due to the behavioral components alone.

Increased adrenergic innervation of sweat glands in early diabetic neuropathy

N. Vujovic, C.B. Saper Department of Neurology, Program in Neuroscience, and Division of Sleep Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA

C. Gibbons, N. Wang, C. Brown, R. Freeman Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA

The circadian rhythm of body temperature (Tb) is a well known physiological phenomenon, but its mechanism has remained unknown. The cycle depends upon the activity of clock neurons in the suprachiasmatic nucleus (SCN), and apparently requires a relay in the dorsal subparaventricular zone (just under the paraventricular nucleus) as cell-specific lesions in that site prevent daily cycles of Tb. However, the targets of the subparaventricular zone that mediate the Tb cycles are not known. One obvious possibility was the preoptic area. The preoptic area is thought to

Background: The sympathetic innervation of sweat glands shifts from adrenergic to cholinergic during early embryologic development, but catecholaminergic innervation appears necessary for sweat gland secretory responsiveness. Diabetic neuropathy results in progressive sudomotor degeneration but sweat output is often maintained or increased in early diabetic neuropathy. The corresponding structural sudomotor phenotypic changes that occur with diabetic neuropathy are not known.

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302 Objective: To determine the changes in cholinergic and adrenergic innervation of sweat glands in early diabetic neuropathy. Methods: Ten diabetic subjects and ten healthy controls were studied by physical examination, sudomotor function testing (QSART) and punch skin biopsies. Biopsies were stained with the panaxonal marker PGP 9.5, the cholinergic marker VIP, the adrenergic marker TH and the alpha 1 adrenergic receptor subtype (A1AR). The density of adrenergic and cholinergic fibers and A1AR expression in sweat glands was determined in all subjects. Results: In the sweat glands of healthy control subjects, cholinergic expression was tenfold greater than catecholaminergic expression (P \ 0.01 in distal leg, distal thigh and proximal thigh). In diabetic subjects, the density of VIP-positive fibers was decreased at all sites (P \ 0.01), compared to healthy controls. In contrast, TH-positive fibers increased at the distal leg (P \ 0.0001), the distal thigh (P \ 0.001) and the proximal thigh (P \ 0.05), and A1AR was correspondently increased (p \ 0.0001) in sweat glands at all sites, compared to healthy control subjects. Conclusions: In diabetic subjects there is a shift in expression from cholinergic to adrenergic fiber phenotypes around sweat glands in early neuropathy. Denervated sweat glands, analogous to observations during early development, may require catecholaminergic stimulation to return to functional status. These structural findings may represent evidence of ongoing nerve fiber regeneration.

Effects of inflammation on vasoreactivity, white matter hyperintensity and brain volume in diabetes P. Zhao1, B. Manor1, M. Munshi1, D. Alsop2, A. Abduljalil3, P. Novak4, P. Roberson5, V. Novak1 1 Gerontology, Beth Israel Deaconess Medical Center, Boston, MA, USA; 2 Radiology, Beth Israel Deaconess Medical Center, Boston, MA, USA; 3 Radiology, Ohio State University, Columbus, OH, USA; 4 Neurology, University of Massachusetts Medical School, Worcester, MA, USA; 5 Department of Biostatistics, University of Arkansas for Medical Sciences, Little Rock, AR, USA Diabetes mellitus (DM) is associated with increased risk of cerebral microvascular disease, vascular dementia and stroke. Hyperglycemia and pro-inflammatory cytokines are the leading causes of endothelial dysfunction and neuronal cell damage. Cerebromicrovascular disease manifests as hypoperfusion, white matter hyperintensities (WMHs) on MRI, regional atrophy and functional decline. We investigated the relationship between expression of serum inflammatory markers, regional WMHs, grey (GM) and white matter (WM) atrophy, and perfusion on MRI in older diabetic adults. We studied 71 type 2 DM and 76 controls using anatomical and perfusion MRI at 3 T. 3DCASL images were acquired to quantify cerebral blood flow and CO2 vasoreactivity (CO2VR). Inflammatory markers included sICAM, sVCAM, CRP, TNF-a, IL-6 and endothelin 1. Inflammatory markers were not different between groups. sICAM, sVCAM, and TNF-a were correlated (p \ 0.0016). sVCAM and sICAM were associated with higher glucose (p \ 0.0003) and global GM atrophy (p = 0.001). They were associated with reduced regional CO2VR (p \ 0.01) affecting multiple brain regions; were not associated with WMHs. These associations were not significant for CRP, IL-6 and endothelin 1. For the whole cohort, in multivariate models adjusted for age, glucose, sICAM and its interactions with glucose were associated with more atrophy and lower vasodilatation reserve (p = 0.004–0.03). For the whole cohort, higher IL-6 was associated

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Clin Auton Res (2010) 20:289–330 with greater temporal WMHs (p = 0.016). WMHs were not associated with inflammation markers, but were strongly associated with age (p \ 0.0001) and GM atrophy (p \ 0.001). The DM group showed more atrophy and WMHs (p \ 0.05) than controls. Markers of vascular integrity (slCAM and sVCAM) were associated with brain atrophy and impaired CO2VR in whole cohort. These observations indicate that inflammatory cytokines may mark different processes associated with abnormalities in perfusion, regulation, and neuronal degeneration. They may also indicate that the combination of proinflammatory state and chronic hyperglycemia may be one of the DM-specific mechanisms that accelerate cerebromicrovascular damage.

Features of cardiac autonomic neuropathy in patients with diabetic foot syndrome: effect of sympathetic vasomotor dysfunction and poor control of hypertension O.V. Mamontov1, O.E. Korotkova2, T.A. Zelenina2, E.V. Shlyakhto1 1 Almazov Federal Heart, Blood and Endocrinology Centre; 2 St. Petersburg Medical Academy of Postgraduate Education Diabetic foot syndrome (DFS) is a complication associated with a trophic tissue disorders, resulting in both macro- and microangiopathy. The close connection between vasomotor abnormalities with the microangiopathy and mediacalcinosis can be considered a destruction of autonomous regulation as a likely factor of the initial trophic disease in patients without leg vessels atherosclerosis. Objective: to evaluate the features of autonomic regulation violations in patients with diabetic foot syndrome. Patients and methods: The study included 174 patients with diabetes type 1/ 2 (23/151). All patients had a combined cardiac autonomic neuropathy, revealed by the positive response for at least one of the two paired tests, reflecting chronotropic and vasomotor regulation. Patients were divided into 2 groups: group 1 (G1) with DFS without stenosis leg vessels, n = 90, mean age 56.4 ± 9.6 years and group 2 (G2) without DFS, n = 84, 54.4 ± 9.7 years. Chronotropic function of the autonomic nervous system (ANS) were evaluated by an index Valsalva (IV) and arterial baroreflex (ABR), vasomotor function— using handgrip test (HG) and forearm blood flow response to the coldstress (COLD), as well as the Tilt-test 10-min protocol. Hemodynamic responses were assessed by Finometer-PRO and Dohn venous occlusion plethysmograph. Results: Was found that the IV correlated with the ABR (r = 0.71, p \ 0.001), whereas the COLD with the HG test (r = 0.73, p \ 0.001), which indicated the similarity of the functional significance of these paired tests. It found that in G1 vasomotor regulation significantly worse than in G2: HG 8.8 ± 5.8 vs. 13.8 ± 4.1 mmHg, p \ 0.01, COLD: 20.3 ± 11.9 vs. 32.1 ± 13.4, p \ 0.005, whereas chronotropic regulation in groups did not differ (IV: 1.34 ± 0.21 vs. 1.32 ± 0.21, p [ 0.05, ABR: 3.64 ± 2.24 vs. 3.86 ± 1.52, p [ 0.05). Despite the comparable occurrence of hypertension in both groups: 73.1 vs. 76.5%, p [ 0.05, in G1 severe hypertension was observed more often, x2 = 4.6, p \ 0.05. In both groups, are often encountered orthostatic hypotension and signs of secondary autonomic failure, indicating a comparable severity of autonomic dysfunction. Conclusion: Patients with DFS have considerably more serious vasomotor ANS function disorder and the worst blood pressure control, which may be useful to identify high-risk groups and amplify ways of preventing this complication.

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GSK3b: a new mechanism in cardiac diabetic autonomic dysfunction Y. Zhang1, H.-J. Park1, C.M. Welzig2, K. Picard1, C. Du3, S. Georgescu1, C. Vaickus1, M. Aronovitz1, W. Claycomb4, J.B. Galper1 1 Tufts Medical Center, Boston, MA, USA; 2 Medical University of South Carolina, Charleston, SC, USA; 3 Tufts University, Boston, MA, USA; 4 LSU Health Sciences Center, New Orleans, LA, USA Glycogen synthase kinase 3b (GSK3b), whose activity is inhibited by insulin via Akt mediated phosphorylation, has been implicated in the pathogenesis of diabetes and other diseases. Diabetic Autonomic Neuropathy is a major complication of diabetes which is associated with parasympathetic dysfunction of the heart. Parasympathetic stimulation of the heart involves acetylcholine (Ach) activation of the G-protein-coupled K+ channel, (GIRK1)2/(GIRK4)2 which mediates an Ach-gated K+ current (IKAch), hyperpolarization of the myocyte membrane and a decrease in beat rate. We have previously demonstrated that type 1 diabetic Akita mice develop parasympathetic dysfunction associated with impaired IKAch in atrial myocytes from these mice. Here we demonstrate that, compared to WT, GSK3b activity in the atrium of the Akita mouse is markedly increased as demonstrated by a 60 ± 8% decrease in pGSK3b while both GIRK1/ GIRK4 expression are decreased by 52 ± 8 and 46 ± 5% (n = 4, P \ 0.05), respectively. Insulin treatment of Akita mice increased pGSK3b and GIRK1/GIRK4 expression to levels in WT. Treatment of HL-1 atrial cells with the GSK3b inhibitor Kenpaullone stimulated IKAch 2.4-fold from -22.4 ± 3.2 pA/pF to -53.2 ± 5.8 pA/pF (n = 15 each, P \ 0.001). To further determine whether the decreased parasympathetic response and GIRK4 expression in the Akita mouse heart were due to increased GSK3b activity, Akita mice were fed Li+, an inhibitor of GSK3b (0.2%) for 1 week, which increased atrial GIRK4 expression 1.7 ± 0.2-fold (n = 6, P \ 0.05) compared to placebo. Finally, Li+ therapy in Akita mice increased the parasympathetic response of the heart. In response to carbachol the absolute decrease in heart rate increased from 244 ± 20 to 304 ± 14 bpm after Li+-treatment, while duration of bradycardia increased 75 ± 4% (n = 11, P \ 0.001). These data support the conclusion that increased GSK3b activity plays a role in the pathogenesis of parasympathetic dysfunction in the diabetic heart and that GSK3b inhibition might have a therapeutic role in the treatment of diabetic cardiac autonomic neuropathy.

An important pitfall in submaximal exercise testing in Parkinson’s disease patients J.T. Groothuis1,3, A.D. Speelman2, J.J.M. Verbeek2, B.R. Bloem2, M. Munneke2, M.T.E. Hopman1 1 Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; 2 Department of Neurology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; 3 Department of Rehabilitation, St Maartenskliniek, Nijmegen, The Netherlands Background: Parkinson’s disease (PD) patients are heavily inclined towards a sedentary lifestyle. The experience in clinical practice is that PD patients express a reduced exercise capacity, but little is known about the physical fitness of PD patients. The aim of this study

303 was to assess the physical fitness of sedentary PD patients using a submaximal cycle exercise test. Methods: 438 PD patients (64 ± 8 years; 65% men) with a sedentary ˚ strand-Rhyming submaximal lifestyle were invited to perform an A cycle exercise test. During a 6 min submaximal exercise protocol, the work load of the cycle ergometer is chosen to achieve a target steady state heart rate between 120 and 170 bpm. The heart rate in the fifth and sixth minute was used to estimate physical fitness [VO2max (ml/ ˚ strand-Rhyming normogram. min/kg)] according to the A Results: 231 (54%) PD patients (61 ± 8 years; 63% men) fulfilled the criteria of the submaximal exercise test and had an estimated VO2max of 24 ± 6 in men and 20 ± 6 ml/min/kg in women. 207 (47%) PD patients (67 ± 6 years; 67% men) failed to reach the target heart rate and estimating VO2max was, therefore, not possible. Not reaching the target heart rate was associated with a higher age, larger body mass index, lower resting heart rate, higher Hoehn and Yahr stage, higher Unified Parkinson’s Disease Rating Scale (UPDRS) III and longer disease duration. Conclusions: PD patients have a lower physical fitness compared with the general population. Interestingly, almost half of the PD patients failed to reach the target heart rate of at least 120 bpm, which might be caused by autonomic failure in these PD patients. Therefore, further research is needed to determine whether a submaximal cycle exercise test is suitable for PD patients.

Is Parkinson disease with orthostatic hypotension a distinctive entity? D.S. Goldstein, L. Sewell, C. Holmes, Y. Sharabi Clinical Neurocardiology Section, CNP, DIR, NINDS, NIH, Bethesda, MD, USA Background: About 40% of patients with Parkinson disease (PD) have orthostatic hypotension (OH). We explored whether PD + OH differs from PD without OH (PD No OH) and pure autonomic failure (PAF), which does not involve parkinsonism. Methods: Clinical laboratory data were reviewed from referred patients with PD + OH (N = 41), PD without OH (PD No OH, N = 45), or PAF (N = 22). Results: The PD + OH group was older at onset of motor dysfunction than the PD No OH group (62 ± 2 vs. 53 ± 2 years, p = 0.0007), had poorer smell test scores, more frequent hypohidrosis and dementia, and lower baroreflex-cardiovagal gain and orthostatic fractional increments in plasma norepinephrine (NE), without group differences in frequencies of constipation or depression. Of 12 PD + OH patients who had an MRI, all had evidence of cerebral atrophy (p \ 0.0001 vs. PD No OH). Plasma NE was lower in PD + OH (1.20 ± 0.13 vs. 2.25 ± 0.57 nmol/L, p = 0.04) but higher than in PAF (0.68 ± 0.15, p = 0.015). CSF dihydroxyphenylacetic acid (DOPAC) was lower in PD than PAF, and CSF dihydroxyphenylglycol:DOPAC ratios were lower in PAF than PD (p = 0.0007). All PD + OH patients but only about ‘ of PD No OH patients had low septal 6-[18F]fluorodopamine-derived radioactivity (p \ 0.0001). PAF patients had normal putamen:occipital cortex ratios of 6[18F]fluorodopa-derived radioactivity, with low ratios in PD (p \ 0.0001). Interpretation: PD + OH is distinguished from PD No OH by age at onset of motor dysfunction, cerebral atrophy, worse olfactory dysfunction, baroreflex failure, and cardiac and extra-cardiac noradrenergic denervation; and from PAF by striatal dopaminergic denervation, more severely decreased central dopaminergic than noradrenergic turnover, and milder peripheral noradrenergic denervation.

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Norepinephrine transporter blockade and cardiac sympathetic innervation C. Shibao, S.R. Raj, L.E. Okamoto, D. Robertson, I. Biaggioni Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN, USA We have previously reported that the pressor response to 18 mg of atomoxetine, a norepinephrine transporter blocker, can be used to determine the level of lesion in patients with autonomic failure. An increase in blood pressure has been associated with central autonomic failure (Multiple System Atrophy, MSA), whereas a blunted response is usually observed in peripheral autonomic failure (Pure Autonomic Failure, PAF and Parkinson’s Disease, PD). Previous studies have validated cardiac imaging studies as a useful tool to determine the level of the autonomic lesions. We, therefore, investigated whether the pressor response to atomoxetine correlates with cardiac sympathetic function as determined by I-123-metaiodobenzylguanidine (MIBG) uptake. A total of 11 patients with severe autonomic failure (9 males, 2 females, 67 ± 3 years old) were studied, 18 mg of atomoxetine was administered 2.5 h after a meal in a seated position. Blood pressure was measured for 30 min every 5 min at baseline and up to 60 min after drug administration. The change in systolic blood pressure at 60 min from baseline was considered as peak pressor response. Cardiac sympathetic innervation was assessed by the heartto-mediastinum (H/M) ratio. There was no correlation between the pressor effect of atomoxetine and H/M ratios (P = 0.8). Atomoxetine increased blood pressure by 26 ± 6 mmHg (range -11 to 56) but had little effect on heart rate (-5 ± 2 bpm, range -7 to 12). These results suggest discordance between cardiac and vascular sympathetic impairment in autonomic failure.

Differentiation of Parkinson’s disease from multiple systems atrophy: comparison of clinical autonomic testing with 123I MIBG myocardial scintigraphy K. Kimpinski1, V. Iodice2, D.D. Burton3, M. Camilleri3, B.P. Mullan3, A. Lipp4, P. Sandroni3, T.L. Gehrking3, D.M. Sletten3, J.E. Ahlskog3, R.D. Fealey3, W. Singer3, P.A. Low3 1 Department of Clinical Neurological Sciences, London Health Sciences Centre, University of Western Ontario, London, ON, Canada; 2 Neurovascular and Autonomic Medicine Unit, Imperial College, London, UK; 3 Department of Neurology, Mayo Clinic, Rochester, MN, USA; 4 Department of Neurology, Charite´-University Medizin Berlin, Berlin, Germany In certain clinical situations, differentiation between idiopathic Parkinson’s disease (PD) and multiple systems atrophy (MSA) can be difficult. Several methods have been devised to provide objective data to help distinguish MSA from PD including standardized autonomic testing and iodine-123 meta-iodobenzylguanidine (123I MIBG) myocardial scintigraphy. It was the aim of this study to compare standardized autonomic testing and 123I MIBG myocardial scintigraphy in PD and MSA patients. Our results show that MSA patients had statistically higher degrees of both adrenergic (CASS sub-score 3.1 ± 0.33) and overall autonomic dysfunction (CASS total scores 5.7 ± 1.41, p \ 0.001) when compared to control (CASS adrenergic sub-score 0.3 ± 0.48 and CASS total score 1.0 ± 0.94) and PD groups (CASS adrenergic sub-score 1.6 ± 1.78 and CASS total score 3.1 ± 2.38). Additionally total body anhidrosis, on thermoregulatory

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Clin Auton Res (2010) 20:289–330 sweat testing, was significantly increased in MSA (% anhidrosis, 67.4 ± 12.42, p \ 0.001) versus PD patients (% anhidrosis, 1.7 ± 2.96). Postganglionic cardiac sympathetic innervation, as measured by I123 MIBG SPECT cardiac imaging, was significantly reduced in PD patients (H/M ratios: 15 min, 1.4 ± 0.36, p = 0.020; 4 h, 1.4 ± 0.40, p = 0.025) versus controls (H/M ratios: 15 min, 1.9 ± 0.27; 4 h, 2.0 ± 0.29) but not when compared to the MSA group (H/M ratios: 15 min, 1.8 ± 0.50; 4 h, 2.0 ± 0.76). Objective tests of autonomic function can aid in the clinical differentiation of MSA and PD particularly when used in combination. Furthermore, these findings further support previous assertions that the autonomic dysfunction in MSA is predominantly preganglionic in MSA and post ganglionic in PD.

Hemodynamic changes underlying nocturnal blood pressure dipping and morning surge in autonomic failure patients with supine hypertension L.E. Okamoto, A. Gamboa, C. Shibao, A. Diedrich, B.K. Black, S.R. Raj, S. Paranjape, D. Robertson, I. Biaggioni Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN, USA Blood pressure (BP) normally decreases during the night (by 10–30% of daytime values, ‘‘dipping’’) and increases on awakening (‘‘morning surge’’). The autonomic nervous system is thought to play a role in mediating this phenomenon. Accordingly, we previously reported a nondipping pattern in 66% of autonomic failure (AF) patients with supine hypertension. In the remaining 34%, however, BP ‘‘dipped’’ at night and returned to their elevated baseline values on awakening. To determine the hemodynamic changes underlying the dipping and morning surge phenomenon in 7 AF dippers we measured supine BP, cardiac output (CO), stroke volume (SV) and systemic vascular resistance (SVR) at 5 pm, 8 pm, 4 am and 8 am. Urine and body weight were measured from 8 am to 8 pm and 8 pm to 8 am. Nighttime systolic BP (12 am–6 am; 127 ± 9 mmHg) decreased by 20 ± 3% of daytime values (157 ± 6 mmHg). This was associated with a 28 ± 7% decrease in CO at 4 am (from 5.2 ± 0.4 during the day to 3.7 ± 0.4 l/min). SV and heart rate (HR) significantly decreased from daytime to 4 am by 24 ± 7% (71 ± 4 vs. 55 ± 8 ml, p = 0.028) and 6 ± 2% respectively (74 ± 4 vs. 69 ± 3 bpm, p = 0.028). Body weight decreased significantly during the night (1.9 ± 0.2 kg, p = 0.018), but we could not document a significant increase in nocturnal diuresis or natriuresis. The morning BP surge was 28 ± 5 mmHg and was associated with a non-significant increase in CO and SV from 4 am to 8 am (21 ± 9 and 19 ± 9%, respectively). SVR and HR remained unchanged (-5 ± 6 and 2 ± 2%, respectively). In conclusion, dipping was associated with a decrease in CO and SV, which are likely secondary to nocturnal volume loss. The morning BP surge was not associated with increases in SVR or HR; redistribution of body fluid and an increase in SV are possible mechanisms underlying this phenomenon.

Olfactory function in pure autonomic failure, multiple system atrophy and dopamine beta hydroxylase deficiency E.M. Garland, S.R. Raj, A.C. Peltier, D. Robertson, I. Biaggioni Autonomic Dysfunction Center, Vanderbilt University, Nashville, TN, USA

Clin Auton Res (2010) 20:289–330 Evidence suggests that a test of odor identification may be useful as an alternative to cardiac neuroimaging in the differential diagnosis of pure autonomic failure (PAF) and multiple system atrophy (MSA). The study of patients with autonomic disorders can also improve our understanding of olfactory function. The objective of this study was to compare the ability to identify odors in patients with peripheral (PAF) or central (MSA) autonomic neurodegeneration and in dopamine beta hydroxylase deficiency (DBH) patients who have intact autonomic neurons but undetectable norepinephrine. Olfactory function (University of Pennsylvania Smell Identification Test, UPSIT) was evaluated in 12 patients with PAF [5 males; mean (95% confidence interval) age 67.2 (61.5, 72.9) years], 10 patients with MSA [5 males; 60.5 (54.1, 66.9) years] and 4 patients with DBH deficiency [2 males; 22.4 (11.2, 33.6) years]. Odor identification was significantly impaired in PAF compared to MSA or DBH deficiency. Out of 40 possible correctly identified odors, mean UPSIT scores were 19.2 (14.1, 24.2), 34.4 (32.2, 36.6), and 31.7 (29.4, 34.1) (P \ 0.001), respectively. The difference between patients with PAF and MSA remained significant after adjustment for age (P \ 0.001). Compared with MSA, patients with PAF also had a greater orthostatic fall in systolic blood pressure [-77 (-91, -63) mmHg vs. -55 (-70, -39) mmHg, P = 0.021] and lower supine plasma norepinephrine levels [68 (43, 93) pg/mL vs. 151 (88, 213) pg/mL, P = 0.003]. Our results indicate that (1) olfactory function was relatively intact in patients with DBH deficiency; (2) peripheral noradrenergic innervation is important for olfactory identification but norepinephrine is not essential; and (3) UPSIT may be useful in the differential diagnosis between these disorders.

Poster Session I Poster #1 Hyperadrenergic postural tachycardia syndrome with sympathetic storms J.J. Figueroa1, P. Sandroni1, W. Singer1, J.R. Basford2, D.M. Sletten1, T.L. Gehrking1, J.A. Gehrking1, P.A. Low1 1 Department of Neurology and 2 Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, MN, USA Hyperadrenergic postural tachycardia syndrome (POTS) is thought to have centrally driven sympathetic activation. There is an unusual subset with episodic bouts of marked sympathetic overactivity. We report 5 female patients with hyperadrenergic POTS and sympathetic storms (SS) evaluated at Mayo Clinic [1997–2010] that had (1) orthostatic intolerance (OI) and postural heart rate (HR) increase [30 bpm over 5 min, (2) standing norepinephrine (NE) [600 pg/mL and/or orthostatic increase of SBP [10 mmHg, (3) paroxysmal sympathetic overactivity manifestations (e.g. tachycardia, hypertension, hyperhidrosis), and (4) no structural neurologic lesion to account for symptoms. In all cases, pheochromocytoma was excluded. Carcinoid was excluded if flushing was present. Median age and disease duration at evaluation were 39 [22–51] years and 13 [1–26] years, respectively. Interval between OI and SS ranged between a few months and 23 years. SS consisted of spontaneous bouts of marked tachycardia, hypertension (often [200 mmHg, SBP) and hyperhidrosis of sudden onset and duration of half to several hours. Additional manifestation included piloerection, flushing, headache, nausea and tremulousness. Orthostatic median values for DHR, max HR, DBP and max BP were 46 [33–86] bpm, 131 [116–178] bpm,

305 19/18 [5/10–40/26] mmHg and 143/91 [125/78–152/95] mmHg, respectively. Orthostatic hypertension occurred in 4 patients. Autonomic reflex screen and thermoregulatory sweat test showed intact sudomotor, cardiovagal and adrenergic function. Median plasma standing NE and orthostatic NE increase were 905 [450–1985] pg/ml and 536 [226–1177] pg/ml, respectively. Mean 24-h urine sodium of 76 [17–129] mmol indicated low sodium intake and possibly low plasma volume. In summary, otherwise unexplained sympathetic storms can be a manifestation of a subset of hyperadrenergic POTS. Major characteristics are the robust orthostatic NE, HR and BP responses (including orthostatic hypertension), intact autonomic pathways, and possibly decreased plasma volume. Brainstem dysregulation may be a shared mechanism.

Poster #2 Blood pressure’s persistent abnormal regulation in postural orthostatic tachycardia syndrome (POTS) R.C. Callejas1, B. Estan˜ol2 1 Hospital Universitario de Puebla, Beneme´rita Universidad Auto´noma de Puebla, Puebla, Mexico; 2 Departamento de Neurologı´a y Psiquiatrı´a, Laboratorio de Neurofisiologı´a Clı´nica. Instituto Nacional de Ciencias Me´dicas y Nutricio´n Salvador Zubira´n, Mexico City, Mexico Introduction: POTS is a very common entity; it is characterized by a heart rate (HR) increment of at least 30 bpm for at least 50% of the standing time, often with oscillations in HR and blood pressure (BP) during standing. Objective: Assess, in time domain, the beat-to-beat HR and systolic blood pressure (SBP) variability in POTS patients and healthy volunteers (HV) during active standing and 7 min forward. Methods: 25 POTS patients and 25 HV, aged from 15 to 50 years were studied. For the studying condition, a single 8 min record was obtained. SBP and HR were noninvasive recorded on a beat-to-beat basis using a Finapres device. HR increment, fall of SBP and time to return to basal SBP were measured. Results: HR increment was larger in POTS patients than in HV (44 ± 13 vs. 30 ± 10 bpm, P \ 0.05). SBP fall (48 ± 19 vs. 29 ± 15 mmHg, P \ 0.05) and time to return to basal SBP (19.6 ± 9 vs. 9.4 ± 2 s, P \ 0.05) was larger in POTS patients. SBP oscillations were observed during standing in POTS patients. Conclusions: POTS patients have a persistent failure in SBP and HR control. The data obtained suggest that the main defect in POTS is in the regulation of SBP during standing, because the SBP oscillations stand along the entire record; been the sympathetic hyperactivity a compensatory mechanism to keep an adequate SBP.

Poster #3 Menstrual cycle does not affect sympathetic neural and hemodynamic responses to upright tilt in the postural orthostatic tachycardia syndrome Q. Fu1,2, T.B. VanGundy1, S. Shibata1,2, M.M. Galbreath1,2, S.S. Jarvis1,2, B.D. Levine1,2 1 Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX, USA; 2 The University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA

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306 Background: The menstrual cycle affects muscle sympathetic nerve activity (MSNA) but not hemodynamics during orthostasis in healthy euvolemic women. Whether this is also true in women with the Postural Orthostatic Tachycardia Syndrome (POTS), who have a small heart coupled with reduced plasma volume, is unclear. We tested the hypothesis that increases in MSNA during upright posture would be smaller in the early follicular phase (EFP) than midluteal phase (MLP) of the menstrual cycle, but hemodynamic responses would be similar between phases in POTS women. Methods: Ten normally menstruating POTS women (15–42 years) were studied during the EFP and MLP. MSNA, blood pressure (BP), heart rate (HR), cardiac output (CO, C2H2 rebreathing), stroke volume (SV = CO/HR), and total peripheral resistance (TPR = mean BP/ CO) were measured supine and during a graded upright tilt (30° for 6 min, 60° for 45 min or till presyncope). Blood samples for catecholamines were collected. Results: Different from healthy euvolemic women, MSNA increases during tilting were similar between the EFP and MLP in POTS women (supine: 142 ± 36 [SD] vs. 165 ± 42 a.u./min, and after 5 min of 60° tilt: 894 ± 65 vs. 851 ± 106 a.u./min; P = 0.70 for phases). Upright systolic BP was lower in the EFP than MLP (P = 0.03), but upright diastolic BP did not differ between phases (P = 0.11). During tilting, HR and TPR increases were similar (P = 0.98 and 0.22), while CO and SV decreases did not differ between phases (P = 0.68 and 0.63). Plasma norepinephrine and epinephrine responses were also similar (P = 0.72 and 0.57 for phases). The tilt time did not differ between the EFP and MLP (32 ± 5 vs. 34 ± 5 min; P = 0.74). Conclusions: The menstrual cycle does not affect sympathetic neural and hemodynamic responses to upright tilt in POTS women. It is suggested that POTS per se is not caused by the fluctuations of sex hormones during the menstrual cycle. Supported by NIH K23 (HL075283) and GCRC grant (RR00633).

Poster #4 Pregnancy in postural tachycardia syndrome: clinical course and maternal and fetal outcomes S. Blitshteyn1, H. Poya2, G.C. Bett2 1 Department of Neurology, University at Buffalo School of Medicine and Biomedical Sciences, Buffalo, NY, USA; 2 Department of OB/GYN, University at Buffalo School of Medicine and Biomedical Sciences, Buffalo, NY, USA Objective: To determine the clinical course of POTS and maternal and fetal outcomes in pregnant women with preexisting POTS. Background: Postural tachycardia syndrome (POTS) is a disorder of the autonomic nervous system characterized by orthostatic tachycardia and symptoms of orthostatic intolerance. Since POTS predominantly occurs in women of child-bearing age, there is a great need in clinical practice to define the course of POTS and maternal and fetal outcomes as these relate to pregnancy and postpartum period. Design/methods: Participants were asked to complete a detailed questionnaire assessing the clinical course of POTS before, during and after pregnancy, as well as complications of pregnancy, labor and delivery and fetal outcomes. Results: Among 10 women with pre-existing POTS (pregnancy age 27 + 6 years, range 16–39), there were a total of 42 pregnancies and 17 live births. The rate of severe vomiting or hyperemesis

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Clin Auton Res (2010) 20:289–330 gravidarum in the first trimester was 60%. Out of 17 pregnancies resulting in live births, 2 were complicated by pre-eclampsia; 14 were normal vaginal deliveries, and 3 were C-sections. There were no stillbirths or congenital abnormalities; the average birth weight of 12 infants whose birth weights were reported was 3,076 ± 733 g. During pregnancy, POTS symptoms were either improved or stable in 6 of 10 women, and 4 of these women were treated with medications for POTS. Six months post-partum, POTS symptoms were improved in 3, stable in 2 and worsened in 5 women compared to before pregnancy. Conclusions/relevance: POTS may have a variable clinical course in pregnancy, with 60% of women reporting either improved or stable symptoms during pregnancy, and 50% of women reporting either improved or stable symptoms 6 months post-partum. There may be a higher rate of severe vomiting in the first trimester and a slightly lower infant birth weight in women with POTS than in general population.

Poster #5 POTS due to excessive venous pooling in an enlarged inferior vena cava C. Gaw1, R. Shields1, K. Mayuga3, H. Gornik2, C. Fonseca2, F. Fouad-Tarazi1 1 Center for Syncope and Autonomic Disorders, The Cleveland Clinic, Cleveland, OH, USA; 2 Section of Vascular Medicine, The Cleveland Clinic, Cleveland, OH, USA; 3 Division of Cardiology, University of California Davis Medical Center, Sacramento, CA, USA Postural orthostatic tachycardia syndrome (POTS) is characterized by orthostatic intolerance and is defined by an increase in heart rate (HR) [30 beats per minute (bpm) or a HR [120 bpm in response to orthostatic stress. Although numerous etiologies for POTS have been described, in many patients a precise etiology is not identified. We report a patient with POTS due to excessive venous pooling in an unusual vascular anomaly, an enlarged inferior vena cava (IVC), or a ‘‘megacava’’ (IVC diameter [30 mm). A 23-year-old woman presented with a 4-year history of orthostatic lightheadedness, dimming of vision, palpitations and sweating. Past history is notable for mitral valve prolapse, asthma, and bipolar disease. General physical and neurological examinations were unremarkable. Headup tilt test disclosed an increase in HR of 45 bpm, from 57 bpm at baseline to 102 bpm by 9 min of tilt. Blood volume was normal. Hemodynamic testing revealed supine hyperkinetic circulation, marked venous pooling, and no postural orthostatic hypotension. Standard cardiovascular autonomic reflex testing was essentially normal. Venous outflow plethysmography documented reduced outflow in the legs and exercise venous plethysmography disclosed reduced ejection fraction in the legs, both consistent with increased venous pooling. There was no evidence of venous obstruction or incompetency on abdominal and pelvic CT scans and venous ultrasound. Magnetic resonance arteriography and venography disclosed a megacava measuring 36.39 mm in diameter. The enlarged IVC is a likely mechanism for this patient’s POTS. The IVC could function as a large capacitance reservoir when the patient moves from a supine to standing position. This additional sequestering of blood could result in transient functional orthostatic hypovolemia and cause her POTS symptomatology.

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Poster #6 Neurohormonal and hemodynamic profile of patients with postural tachycardia and chronic fatigue syndrome L.E. Okamoto, S.R. Raj, A. Gamboa, C. Shibao, A. Diedrich, B.K. Black, G. Farley, D. Robertson, I. Biaggioni Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN, USA Background: Several studies have recognized an overlap between chronic fatigue syndrome (CFS) and postural tachycardia syndrome (POTS), a condition characterized by sympathetic overactivity. Chronic abnormalities in volume regulation and autonomic function have been proposed as possible common mechanisms in both conditions. The purpose of this study was to compare the neurohormonal and hemodynamic profile of POTS with CFS (CFS-P) with those POTS patients without CFS (POTS). We hypothesize that increased sympathetic activity contributes to the development of CFS in POTS. Methods and results: Of the 58 POTS patients initially recruited, 47 were eligible to participate and 30 of these (64%) met CFS criteria. Fatigue (measured with the fatigue subscale of the Checklist Individual Strength) was present in all CFS-P and 80% of POTS, but was more severe in CFS-P (51 ± 1 vs. 43 ± 3, p = 0.016). A similar proportion of CFS-P and POTS were on beta-blockers (64 and 65%) suggesting that fatigue was not drug-induced. CFS-P had greater orthostatic tachycardia than POTS (51 ± 3 vs. 40 ± 4 bpm, p = 0.039), and a higher supine (1.49 ± 0.22 vs. 1.02 ± 0.33 ng/ mL/h; p = 0.034) and upright plasma renin activity (5.42 ± 0.61 vs. 3.46 ± 0.81 ng/mL/h; p = 0.033). CFS-P had a greater increase in BP during late phase II of the Valsalva maneuver than POTS (18 ± 3 vs. 11 ± 2, p = 0.042) and a tendency towards greater LF-SBP at rest (6.2 ± 0.7 vs. 5.2 ± 1.1 mmHg2, p = 0.063). Supine and upright BP, aldosterone, plasma norepinephrine and the incidence of abnormal QSART did not differ between groups. Conclusions: These findings suggest that fatigue and CFS are common in POTS, and are associated with increased sympathetic and renin responses. There are, however, no distinguishing clinical features in POTS with or without CFS. Thus, it is not clear if the presence of fatigue is indicative of a different underlying pathophysiological process or if it is part of the spectrum of POTS.

Poster #7 Clinical observations in a cohort of patients with autonomic dysfunction A. Barboi, T. Prieto, M. Yellick, J. Bergholte, C. Dennis, N. Fabian, S. Jaradeh Department of Neurology, Medical College of Wisconsin, Milwaukee, WI, USA Between 2003 and 2008, 459 patients with a clinical diagnosis of autonomic dysfunction filled out a general review of systems questionnaire and underwent a full neurological clinical evaluation. All patients had autonomic and laboratory testing. Depending on clinical suspicion, electroneuromyography, fat pad aspirate, skin, and nerve or muscle biopsies were preformed. There were 118 men (mean age 47.3 years) and 341 women (mean age 44.4 years). Reasons for referral included: pain (50%), lightheadedness (22%), paresthesias

307 (16.8%), and gastrointestinal problems (7.2%). The onset was insidious in 85.6%, rapid in 14.4% and course was progressive in 92.8%. Onset of symptoms was in the first 2 decades for females (82.2%) and was uniform for men across the first 4 decades. A family history was positive in 55.3%, and was associated with increased chance of progression (60.9 vs. 39.1%; p \ 0.001) and earlier onset of symptoms (p \ 0.001). Other symptoms included: daily fatigue (73.2 %), tinnitus (44%), rhinitis (48.4%), orthostatic intolerance (56.6%), cyclic vomiting (1.1%), slow gut motility (30.1%), fast gut motility (25.9%), gastro esophageal reflux (24.8%), dysphagia (5%), and urinary frequency (17.9%). Painful complaints were diffuse leg predominant (31.4%), diffuse arm predominant (19.6%), segmental chest (8.1%), segmental abdomen (6.3%), and migraine (26.8%). Psychiatric co-morbidity included: depression (20.9%), anxiety (12.0%), somatization (7.7%), bi-polar disease (3.3%), and panic disorder (2.8%). The clinical phenotype included scoliosis (12.5%), mild foot and hand deformities (50%) increased joint mobility (39.2%) and increased skin elasticity (41.4%). Autonomic testing showed sudomotor abnormalities in 80% (preganglionic 43%, postganglionic 47.8% and both 7%), cardiovagal dysfunction (26.4%), vasomotor dysfunction (35.3%) and postural orthostatic tachycardia (20.5%). Skin biopsies were abnormal in 82.5% and were associated with clinical distal nociceptive loss (p \ .018) but not with postganglionic sudomotor dysfunction (p \ 0.365). These observations suggest the existence of an autosomal dominant, familial background autonomic dysfunction syndrome.

Poster #8 Serotonin reuptake inhibition acutely worsens symptoms in postural tachycardia syndrome (POTS) S.R. Raj, I. Biaggioni, B.K. Black, C.A. Shibao, S.Y. Paranjape, D. Robertson Vanderbilt University, Nashville, TN, USA Background: Selective serotonin reuptake inhibitors (SSRIs) are widely used in patients with POTS (heart rate [HR] increase[30 bpm on standing) both to treat anxiety/depression and for increasing vascular resistance and blood pressure. Despite their common, there is not much data on their effects in POTS. We prospectively tested the effects of sertraline on HR, blood pressure [BP] and symptoms in POTS. Methods: Patients with POTS (n = 31;29 female, 32 ± 9 years) underwent a randomized single-blind crossover trial with oral sertraline 50 mg and placebo on separate mornings in a post-absorptive and drug-free state. Non-invasive HR and BP were measured with the patient seated comfortably. At baseline, and hourly for 4 h postmedication, the patients stood for up to 10 min, and their standing HR and BP were recorded. Symptoms were self-recorded q2 hourly. Complete datasets were analyzed in the repeated measures model. Results: There was no difference in the standing HR from baseline (B) to 4 h post drug between sertraline (B: 116 ± 16 [mean ± SD] bpm, 4 h: 101 ± 14 bpm) than placebo (B: 118 ± 19 bpm, 4 h: 106 ± 22 bpm; PINT = 0.179). Nor were there significant differences in standing systolic BP between sertraline (B: 101 ± 9 mmHg, 4 h: 109 ± 10 mmHg) and placebo (B: 107 ± 16 mmHg, 4 h: 107 ± 14 mmHg; PINT = 0.267). The overall symptoms reduction was greater with placebo than sertraline (-0.2 ± 13.6 vs. -8.7 ± 12.4; P = 0.02), driven by lightheadedness (P = 0.03), mental clouding (P = 0.05), palpitation (P = 0.05), and tremulousness (P = 0.03). Conclusions: Acutely, serotonin reuptake inhibition does not alter standing HR or BP compared with placebo. Acute sertraline did not elicit any improvement in symptoms, and indeed multiple symptom

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308 indices were better after placebo. While these data call into question the use of SSRIs for POTS, it is recognized that most CNS benefits of this drug class arise after days to weeks. Further studies are needed to show if the adverse acute effects of sertraline shown here can be counterbalanced by chronic benefit.

Poster #9 Beta blockers and exercise in POTS A. Gamboa, L.E. Okamoto, A. Arnold, B. Black, A. Diedrich, G. Farley, S.Y. Paranjape, I. Biaggioni Department of Medicine, Vanderbilt University, Nashville, TN, USA Postural tachycardia syndrome (POTS) is a hyperadrenergic disorder characterized by an excessive increase in heart rate upon standing (more that 30 bpm) and extreme orthostatic intolerance. In addition, patients also suffer from varying degrees of physical deconditioning in part due to their profound exercise intolerance. Propranolol is the most frequently used pharmacological treatment to control tachycardia, but also has the potential side effect of increasing fatigue. Exercise training has been proposed as a nonpharmacological treatment of this condition and has the potential to chronically decrease baseline heart rate and improve orthostatic tolerance. We have recently shown that low doses of propranolol not only does not impair exercise tolerance but improves peak VO2. Now we determined if a selective beta-1 blocker (metoprolol) could provide additional benefit by avoiding the potential blockade by propranolol of beta-2-mediated muscle vasodilation during exercise. We studied five POTS patients in a double-blind, randomized, placebo controlled crossover study; VO2max was measured on three occasions, on patients received either placebo, 80 mg propranolol PO or 50 mg metoprolol 50 mg PO, 40 min prior to exercising in a recumbent bike. Resistance was increased by 25 W at 2-min intervals until maximal effort was achieved. Subjects’ baseline oxygen consumption, cardiac output, heart rate and blood pressure were similar in all days. Peak heart rate was lower with either betablockers (177 ± 8 vs. 147 ± 8 and 139 ± 11 bpm for placebo, propranolol and metoprolol respectively, p = 0.024), and peak VO2 was statistically higher on the propranolol day (27.0 ± 3.5, 29.5 ± 3.3 and 29.1 ± 3.7 ml/kg/min for placebo, propranolol and metoprolol respectively, p = 0.0085 by Friedman test). These results suggest that beta blockade improves heart rate control during exercise and provides a marginal improvement in exercise tolerance after a single bout of exercise. Metoprolol did not seem to be superior to propranolol in improving exercise tolerance. Pre-treatment with beta-blockade could be tested as an adjuvant to an exercise rehab program in POTS.

Poster #10 Alterations of cardiovascular autonomic profile in constitutional hypotension F. Barbic1, R. Furlan1, A. Porta2, M. Glago3, G. Jacob3 1 Internal Medicine, ‘‘Bolognini’’ Hospital, Seriate, Bergamo; 2 Department of Technologies for Health, Galeazzi Orthopaedic Institute, Milan; University of Milan, Italy; 3 Medicine F., Tel Aviv Medical Center Sourasky, University of Tel Aviv, Israel

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Clin Auton Res (2010) 20:289–330 Constitutional hypotension, defined by the World Health Organisation as recumbent systolic arterial pressure SAP\100 mmHg in female, is characterized by several complaints including fatigue, dizziness, palpitations, pre-syncope symptoms and syncope on standing. This suggests a potential underlying abnormality of the cardiovascular neural autonomic control. We compared a group of 15 female subjects (age 32 ± 4 years) affected by constitutional hypotension (HYPO) with 12 healthy volunteers (C) matched for age (31 ± 2 years) and gender. Every subject underwent beat by beat non invasive arterial pressure (Finometer), ECG and respiratory activity continuous recordings for 15 min at rest and during 75° head-up tilt. Power spectrum analysis of heart rate (HR) and SAP variability and of respiration provided the indices of cardiac sympatho-vagal instantaneous relationship (LF/HF) and of sympathetic vasomotor control (LFSAP, 0.1 Hz). At rest, SAP was lower in HYPO (97.4 ± 1.3 mmHg) compared to C (122.3 ± 1.7 mmHg), whereas HR and respiratory rate were similar in the two groups. LF/HF was higher and LFSAP was lower in HYPO (1.39 ± 0.19 and 0.79 ± 0.12 mmHg2, respectively) compared to C (0.68 ± 0.11 and 1.53 ± 0.30 mmHg2, respectively). During tilt, SAP was lower in HYPO (91.2 ± 2.2 mmHg) than in C (115.3 ± 3.7 mmHg). HR, LF/ HF and LFSAP increased similarly in the two groups. Thus, at rest individuals affected by constitutional hypotension were characterized by a reduced sympathetic modulation to the vessels and a cardiac sympatho-vagal balance shifted towards a sympathetic predominance compared to normotensive subjects. The fact that during tilt HYPO could increase the sympathetic cardiovascular modulation only by the same amount of controls, in spite of the reduced sympathetic vasomotor control at rest, might account for the higher rate of pre-syncope signs described in constitutional hypotension.

Poster #11 Multiscale entropy of heart rate and blood pressure: an effect of orthostasis M. Javorka1, Z. Turianikova1, K. Javorka1, M. Baumert2 1 Department of Physiology, Jessenius Faculty of Medicine, Comenius University, Martin, Slovak Republic; 2 School of Electrical and Electronic Engineering, The University of Adelaide, Australia Objective: Multiscale entropy (MSE) quantifies the information content of a signal over multiple time scales. In previous studies, MSE analyses of cardiovascular signals identified impaired cardiovascular control and increased cardiovascular risk in various pathological conditions. Despite the increasing acceptance of the MSE technique in clinical research, information underpinning the autonomic nervous system involvement in MSE of heart rate and blood pressure is scarce. Therefore, the aim of this study was to study the effects of orthostatic challenge on MSE of heart rate variability (HRV) and blood pressure variability (BPV) in healthy young subjects and to investigate the correlation between MSE and traditional linear measures. Methods: MSE analysis of HRV and BPV (noninvasively recorded by Finometer device) was performed in 28 healthy young subjects over 1,000-beats recordings in the supine and standing positions. The entropy values within multiscale entropy analysis were assessed on scales 1–10. Results: MSE analyses of heart rate and blood pressure signals were sensitive to changes in autonomic balance accompanying postural change from the supine position. The effect of orthostatic challenge

Clin Auton Res (2010) 20:289–330 on heart rate and blood pressure complexity were dependent on the time scale under investigation. MSE values did not correlate with the mean values of heart rate and blood pressure demonstrating only weak correlations with linear HRV and BPV measures. Conclusion: Multiscale analysis of heart rate and blood pressure entropy is able to detect changes in autonomic balance induced by changes in autonomic tone induced by postural change. Since these changes are scale dependent, the multiscale approach to the analysis of cardiovascular signals analysis is emphasized. This study was supported by project of Centre of Excellence for perinatological research No. 26220120016, grant VEGA no. 1/0064/08. Dr Baumert was awarded an Early Career Researcher Fellowship from the Health Faculty, University of Adelaide.

Poster #12 Characteristic pattern of autonomic dysfunction in chronic radiation-induced baroreflex failure presenting with orthostatic hypotension W. Singer, B.P. Goodman, T.L. Opfer-Gehrking, P.A. Low Department of Neurology, Mayo Clinic, Rochester, MN, USA Background: Denervation of carotid baroreceptors can occur following trauma, and as complication from surgical procedures or radiation therapy to the neck region. The phenomenon of baroreceptor denervation is well described in animals and humans with its acute and chronic effects on the cardiovascular system. The clinical presentation can be quite variable, in part depending on whether the denervation is acute or chronic, unilateral or bilateral. Chronic bilateral baroreceptor denervation can present as volatile hypertension, hypertensive crisis, orthostatic hypotension, orthostatic tachycardia, and malignant vagotonia. We raise the question whether a clinical presentation with orthostatic intolerance in patients with a history of neck irradiation is associated with a characteristic pattern of autonomic impairment reflecting chronic baroreflex failure. Methods: Two patients with history of neck irradiation for malignancies affecting the neck (Hodgkin’s lymphoma, tonsillar carcinoma) who presented with a chief complaint of orthostatic intolerance underwent standardized autonomic reflex testing at Mayo Clinic. This included autonomic reflex screen (ARS), thermoregulatory sweat test (TST), and 24-h blood pressure (BP) profile. There was no history of hypertension or known BP lability. Other potential causes for autonomic dysfunction were excluded. Results: ARS screen showed remarkable similarity between the patients: Heart rate (HR) responses to deep breathing were normal. Valsalva-ratio and vagal baroreflex gain were reduced. BP responses to the Valsalva maneuver showed markedly reduced late phase II, absent phase IV overshoot, and prolongation of BP recovery time. Head-up tilt showed orthostatic hypotension with a blunted HR response. Quantitative sudomotor axon reflex testing (QSART) at four standardized sites was normal. TST showed areas of anhidrosis in the region of the neck in both patients, likely reflecting radiation-induced sweat-gland atrophy. Twenty-four hours blood pressure profile revealed hypertension and BP lability. Conclusions: Patients with a history of neck irradiation can present with orthostatic hypotension due to radiation-induced baroreflex failure, even in the absence of a history of other symptoms related to baroreflex dysfunction. Autonomic testing reveals a characteristic pattern of abnormalities, demonstrating isolated adrenergic and vagal baroreflex failure, along with anhidrosis of the neck. Of interest, although asymptomatic, BP lability is also present, suggesting the described clinical presentation to represent one end of a wide, but overlapping, clinical spectrum of chronic baroreceptor denervation.

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Poster #13 Mechanisms mediating tilt-induced (pre)syncope may be sensitive to age but not gender C. Schroeder1, J. Tank2, K. Heusser2, A. Diedrich3, F.C. Luft1, J. Jordan2 1 Experimental Clinical Research Center, Medical University Charite´ and Max Delbru¨ck Center for Molecular Medicine, Berlin, Germany; 2 Institute of Clinical Pharmacology, Hannover Medical School, Hannover, Germany; 3 Autonomic Dysfunction Service, Vanderbilt University, Nashville, TN, USA Background: Neurally mediated syncope is particularly common in younger women. Therefore, we tested the hypothesis that gender and age affect the hemodynamic response upon head-up tilt-induced (pre)syncope. Methods: We analyzed hemodynamic data from 173 consecutive patients (114 women, 59 men, 42 ± 1 years [range 12–79]) who had been referred for work-up of unexplained syncope. All had experienced (pre)syncope during head-up tilt for 20 min at 60°, followed by additional lower body negative pressure at -20 and -40 mmHg for 10 min each. We monitored heart rate and finger blood pressure. We determined onset and dynamics of hypotension and bradycardia manually and classified hemodynamic responses according to VASIS. Results. Women were 41 ± 2 years and men were 44 ± 2 years old (n.s.). Women reported more syncopal episodes (20 ± 3 vs. 11 ± 3, p \ 0.05) over a longer time (11 ± 1 vs. 6 ± 1 years, p \ 0.001). Women had lower blood pressure and higher heart rates in the supine position than men. Tilt time and onset and extent of hypotension and bradycardia upon (pre)syncope were similar in women and in men. VASIS classes were equally distributed between sexes. Patients aged 40 years or less had lower blood pressure and higher heart rates than patients older than 40 years. Neither the number and duration of syncopal episodes, nor the overall tilt time differed between younger and older patients. The decline in both, blood pressure and heart rate was steeper in younger compared with older patients (-0.6 ± 0.1 vs. -0.4 ± 0.0 mmHg/s, p \ 0.01 and -0.5 ± 0.1 vs. -0.2 ± 0.0 bpm/ s, p \ 0.001 respectively). Cardioinhibitory responses (VASIS class 2) occurred in 14% of the younger and 3% of the older patients (p \ 0.05). Conclusions. Although syncope in real life occurs more often in women than in men, hemodynamic responses during tilt-induced (pre)syncope appear to be independent of gender. However, the mechanisms setting off tilt-induced (pre)syncope may be sensitive to age.

Poster #14 Mechanisms for the reduction in facial skin blood flow at pre-syncope in normothermic and heat-stressed individuals C.G. Crandall, R.M Brothers, M.S. Ganio Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital of Dallas, and Department of Internal Medicine, University of Texas Southwestern Medical Center of Dallas, TX, USA Facial pallor is commonly associated with syncopal symptoms, suggestive of reduced facial skin blood flow. Possible mechanisms responsible for this observation include passive reductions in skin

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310 blood flow secondary to reductions in arterial blood pressure (i.e., reduced perfusion pressure) and neurally mediated reductions in cutaneous vascular conductance. Based upon prior findings showing minimal decreases in forearm cutaneous vascular conductance at presyncope, we tested the hypothesis that decreased facial skin blood flow at pre-syncope is due primarily to reductions in arterial blood pressure, with minimal neural influences. Forehead skin blood flux (an index of skin blood flow measured via laser-Doppler Flowmeter) and cutaneous vascular conductance (skin blood flux/mean arterial pressure) were evaluated during a graded lower-body negative pressure (LBNP) challenge to pre-syncope in 7 normothermic subjects and 15 heat stressed subjects (increase intestinal temperature 1.4 ± 0.2°C). Arterial blood pressure was obtained via radial artery catheterization or from the brachial-reconstructed FinometerÒ waveform. LBNP decreased mean arterial pressure from 90 ± 9 to 57 ± 11 mmHg at pre-syncope during normothermia and from 81 ± 8 to 57 ± 16 mmHg during heat stress (both P \ 0.01). Likewise, LBNP decreased forehead skin blood flux from 104 ± 40 to 52 ± 34 flux units at pre-syncope during normothermia and from 309 ± 69 to 181 ± 82 flux units during heat stress (both P \ 0.01). At pre-syncope, while normothermic 57 ± 34, and while hyperthermic 58 ± 42%, of the reduction in forehead skin blood flow could be accounted for by reductions in arterial blood pressure, with the residual *43% being attributed to reductions in cutaneous vascular conductance. Counter to our hypothesis, these data indicate that in both thermal conditions facial pallor associated with syncopal symptoms is due to a combination of passive decreases in skin blood flow secondary to reductions in arterial blood pressure and to active reductions in cutaneous vascular conductance that are presumably neurally-mediated.

Poster #15 During comprehensive autonomic testing dicrotic notch changes detected by transcranial Doppler monitoring helped to clarify the pattern of autonomic changes present in a patient with a history of syncope: a case study R.E. Leppanen1,2, J. Collins2, D. Morrison2, A. Line2 1 Knoxville Neurology Clinic, Knoxville, TN, USA; 2 Mercy Medical Center, Knoxville, TN, USA History: A 15-year old male experienced a syncopal episode 8 days before autonomic laboratory testing. For the previous month, he had experienced intermittent dizziness/lightheadedness and a tired feeling that limited his standing time. Testing: Autonomic testing consisted of the recording of: 1. Right upper and lower extremity quantitative sudomotor axon reflex (QSART) recordings, 2. Continuous beat-to-beat blood pressure, EKG and bilateral transcranial doppler (TCD) middle cerebral artery velocity with emboli detection studies during the heart rate response to deep breathing, Valsalva maneuver and head up tilt. Results: The QSART, tilt, mean Valsalva maneuver blood pressure changes and TCD studies were abnormal. The heart rate response to deep breathing, Valsalva ratio and Valsalva maneuver systolic blood pressure recovery time were normal. The Comprehensive Autonomic Severity Score was 2. During the tilt study, the heart rate increased by greater than 30 beats per minute, excessive blood pressure oscillations were present and the TCD dicrotic notch deepened. The dicrotic notch deepened, followed by the TCD blood flow stopping transiently during each Valsalva maneuver.

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Clin Auton Res (2010) 20:289–330 Conclusions: Routine studies: 1. Sympathetic neuropathy, 2. Decreased peripheral vasoconstriction, 3. Orthostatic intolerance, 4. Mild generalized decreased autonomic function. TCD studies: 1. Decreased cerebrovascular autoregulation (CVA) during the head up tilt study, 2. Decreased CVA during the Valsalva maneuver. The TCD changes provided another possible etiology for the patient’s symptoms which was an imbalance between cerebral perfusion pressure and vascular resistance. One possibility for this would be aortic valve dysfunction associated with the stress of testing.

Poster #16 The influence of autonomic neural control on human cerebral vessels ‘in vivo’ S. Purkayastha1, R. Zhang2, B.D. Levine2, P.B. Raven1 1 Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, TX, USA; 2 Institute for Exercise and Environmental Medicine, Presbyterian Hospital and the University of Texas Southwestern Medical Center, Dallas, TX, USA Recently, functional a-1 adrenergic receptors were identified to be present on cerebral vessels using Norepinephrine spillover measures across the brain. In addition, other studies have identified that the a-1 adrenergic receptor agonist Phenylephrine (PE) and ganglion blockade using Trimethaphan (T) effected dynamic cerebral autoregulation. We tested the hypothesis that increases in arterial pressure with PE infusion and ganglion blockade using T induced changes in cerebral vascular tone. We estimated changes in vascular tone using calculated measures of critical closing pressure (CCP) from four of the subjects challenged with systemic infusions of PE at: 0; 0.5; 1.0; and 2.0 lg/ kg/min and ganglion blockade using T infusions at 6 mg/min. The CCP was calculated from beat-to-beat systolic and diastolic arterial pressures (SAP and DAP) paired with their corresponding beat-tobeat systolic and diastolic middle cerebral artery blood velocities (MCA Vs and MCA Vd) across 20 cardiac cycles. Means and standard error of the means were calculated for each drug dosage and differences in calculated CCP were analyzed using one way repeated measures analysis of variance (ANOVA). 1.0; and 2.0 lg/kg/min of PE significantly increased CCP above the basal CCP and that of the 0.5 lg/kg/min of PE. Trimethaphan reduced CCP below basal (0) and all three doses of PE but was only significantly reduced below the 1.0 and 2.0 lg/kg/min doses of PE. We conclude that systemic infusions of drugs that effect a-1 adrenergic receptors and autonomic ganglionic activity resulting in changes in arterial pressure modify cerebral vascular tone in healthy human subjects.

Poster #17 What is the stimulus for oscillations in arterial pressure and cerebral blood velocity? C.A. Rickards1, K.L. Ryan2, C. Hinojosa-Laborde2, W.H. Cooke1, V.A. Convertino2 1 Department of Health and Kinesiology, University of Texas at San Antonio, TX, USA; 2 US Army Institute of Surgical Research, Fort Sam Houston, TX, USA

Clin Auton Res (2010) 20:289–330 Oscillations in arterial pressure (AP) and cerebral blood velocity (CBV) are associated with improved tolerance to progressive central hypovolemia (Rickards et al., FASEB J 2009). We utilized two techniques with opposing effects on central blood volume (lower body negative pressure (LBNP) and exercise) to test the hypothesis that increases in hemodynamic oscillations are unique to the hypovolemic state. Fifteen subjects participated in two experimental protocols; (1) progressive central hypovolemia via LBNP, and; (2) supine cycle exercise. Exercise workloads were determined by matching heart rate (HR) responses elicited at each LBNP level. HR (ECG), AP and stroke volume (SV) (Finometer), and CBV (transcranial Doppler ultrasound) were measured continuously; data were analyzed in time and frequency domains. Oscillations were calculated in the low frequency (LF; 0.04–0.15 Hz) and high frequency (HF; 0.15–0.4 Hz) bands. We compared physiological responses at baseline, and during the first four stages of LBNP and exercise. SV decreased by 45 ± 2% during LBNP (P \ 0.001), and increased by 11 ± 2% with exercise (P \ 0.001). RRI HF (representing vagal activity) decreased from baseline to stage 4 during both LBNP (71 ± 9%) and exercise (82 ± 7%), resulting in HR increases from 66 ± 3 to 98 ± 4 bpm during LBNP, and from 61 ± 3 to 98 ± 4 bpm during exercise. While spontaneous baroreflex sensitivity decreased (P \ 0.001) with similar magnitude under both conditions, oscillations (LF and HF) in mean arterial pressure (MAP) and mean CBV increased during LBNP (P = 0.013) but were not statistically distinguishable throughout exercise (P = 0.52). Conversely, respiration rate increased from 13 ± 1 to 18 ± 1 breaths/min during exercise (P \ 0.001), but did not demonstrate a statistically significant change during LBNP (13 ± 1 vs. 14 ± 1 breaths/min; P = 0.98). These data support our hypothesis that oscillations in AP and CBV increase with reductions in SV, but are not necessarily driven by changes in vagally mediated baroreflex responses or respiration.

Poster #18 Time domain indices of cerebral autoregulation and the nonlinear role of sympathetic control C. Ozan Tan1,2, J.W. Hamner 1, J.A. Taylor1,2 1 Cardiovascular Research Laboratory, Spaulding Rehabilitation Hospital, Boston, MA, USA; 2 Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA, USA Previous work has demonstrated a marked frequency-dependent increase in the gain relations between arterial pressure and cerebral blood flow following sympathetic blockade, and that sympathetic control may operate, at least in part, in a nonlinear fashion. However, the linear nature of prior analyses precluded quantification of this nonlinear component of sympathetic control. To circumvent this limitation, we applied a non-parametric projection pursuit regression to beat-by-beat arterial blood pressure and cerebral blood flow velocity recorded in eleven volunteers (21–40 years; 4 females) during oscillatory lower body negative pressure at 40 mmHg across 6 frequencies (0.03–0.08 Hz) before and after alpha-adrenergic sympathetic blockade. The model explained a significant proportion of the variation in cerebral blood flow for each individual, frequency, and condition [average r = 0.61 ± 0.02 (mean ± SE), p \ 0.01]. Estimated nonlinearity took the form of a ‘classical autoregulation curve’: two passive regions (mean arterial pressure \84 or [98 mmHg) where pressure changes induce parallel changes in cerebral blood flow, and an autoregulatory region where pressure changes are

311 counterregulated. This nonlinearity was consistent across individuals (p [ 0.95), and tended to linearize at higher frequencies and after sympathetic blockade (p \ 0.01; p = 0.91 for interaction.). The limits of the autoregulatory region were similar across frequencies, and did not change with blockade (84.3 ± 0.97–97.3 ± 1.42 before and 85.3 ± 0.9–97.7 ± 1.35 mmHg after blockade; p [ 0.1). Sympathetic blockade increased the slope within the autoregulatory region from -0.10 ± 0.06 to 0.10 ± 0.04 cm/s/mmHg (p = 0.006), indicating a transition from ‘counterregulation’ to ‘transmission.’ The magnitude of this transition tended to be larger at higher frequencies (p = 0.09; p [ 0.1 for frequency 9 condition interaction.). Therefore, our approach provides a complete picture of the sympathetic system’s ranges of action, reveals a characteristic nonlinearity within a range of blood pressures, and highlights the utility of robust yet simple nonlinear approaches.

Poster #19 Role of otolith inputs in cerebral blood flow regulation J.M. Serrador1,2,3, B. Deegan3, S. Forstbauer3, T. Nichols3, S.J. Wood5 1 Harvard Medical School and 2 Veterans Biomedical Research Institute and War Relate Illness and Injury Study Center, East Orange, NJ, USA; 3 National University of Ireland, Galway, Ireland; 4 NASA Johnson Space Center and Universities Space Research Association, NASA Johnson Space Center, Houston, TX, USA Assumption of the upright posture places the brain above the heart, causing a reduction in cerebral perfusion pressure due to hydrostatic pressure changes related to gravity. Since vestibular organs, specifically the otoliths, provide immediate feedback on position relative to gravity, vestibular inputs may assist in adaptation to the upright posture. The goal of this study was to examine the effect of direct vestibular stimulation using off vertical axis rotation (OVAR) on cerebral blood flow (CBF). During one session subjects were placed in a chair that was tilted 20° off-vertical and accelerated at 25°/s2 to a constant velocity. Rotation occurred at three frequencies (0.03125, 0.125 and 0.5 Hz). Subjects were tested with their heads facing forward, turned 45° left and 45° right during each frequency. The purpose of changing head position relative to the body was to determine if changing otolith orientation relative to gravity would also shift the cerebral blood flow response, even though effects of centripetal acceleration on the body were not changed. During testing, CBF (transcranial Doppler), blood pressure (Finapres), and end tidal CO2 (Puritan Bennet) were measured continuously. All rotations were done in the dark. Subjects demonstrated sinusoidal patterns of both cerebral blood flow (±2.6% at 0.5 Hz; ±8.8% at 0.125 Hz; ±8.7% at 0.03125 Hz) and blood pressure (±7.9 mmHg at 0.5; ±5.9 mmHg at 0.125; ±5.1 mmHg at 0.03125 Hz) that were related to the frequency of rotation. Turning subjects heads resulted in a phase shift in the associated CBF signal (42 ± 29° at 0.5 Hz; 6 ± 31° at 0.125 Hz; 52 ± 20° at 0.03125 Hz). In contrast, oscillations in blood pressure were unaffected by head position. These data indicate that changing otolith position 45° by head rotation resulted in a similar phase shift in CBF. The attenuated shift at 0.125 Hz may have been associated with the nauseogenic nature of the middle frequency disrupting normal vestibular inputs into CBF control. Since trunk position remained unchanged, these data suggest that oscillations in CBF associated with OVAR are primarily due to otolith stimulation. Supported by NIH NIDCD and NASA.

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Poster #20 Orthostatic hypotension in mild cognitive impairment O. Collins, C. Finnucane, S. Dillon, B.A. Lawlor, R.A. Kenny Trinity College and St James’s Hospital, Dublin, Ireland Objectives: Hypotension is cited as a vascular risk for dementia, but it’s role is poorly understood. Studies suggest an association between OH and reduced cerebral blood flow. Cerebral hypoperfusion induces over expression of beta amyloid in animal models. Hence, OH may be a risk factor for cognitive decline and dementia. We explored the prevalence and severity of OH in MCI. Methods: MCI participants were recruited from memory clinics. MCI was defined using the Consensus criteria for MCI and by neuropsychological assessments (=1.3 SD in memory/non-memory domain). Active stands were performed using beat-to beat technology. The profile of OH was explored using standard (baseline SBP, nadir and D SBP = baseline-nadir) and novel parameters. Novel parameters included time to recover baseline SBP values (TR), recovery 40 (baseline SBP –SBP at 40 s), and area under curve (AUC). Cognitive assessments performed were the CAMCOG and Cognitive Drug Research battery. Results: 105 MCI participants and 42 controls were recruited (median age 74.5 vs. 72.0 years). MCI participants showed greater changes in SBP on orthostasis [47 vs. 38 mmHg (P = 0.02)] and poorer recovery 40 pattern than controls [16 vs. 4 mmHg (P = 0.006)]. MCI participants showed increased but not significant TR and AUC values. Multivariate linear regression showed significant association between recovery 40 and executive function (P = 0.01), attention and working memory (P = 0.03). Conclusion: OH is more severe in MCI using both standard and novel parameters. The recovery profile of SBP is important and is associated with deficits in cognitive domains most vulnerable to cerebral hypoperfusion. Hence, OH induced cerebral hypoperfusion may be a risk factor for cognitive decline and dementia. Neuroimaging will help determine the association with white matter disease.

Poster #21 Are compression stockings really an effective treatment for orthostatic intolerance? C.L. Protheroe, A. Dikareva, V.E. Claydon Department of Biomedical Physiology and Kinesiology, Simon Fraser University, BC, Canada Syncope, or fainting, affects approximately 6.2% of the population at least once in their lifetime and is associated with significant comorbidity. Posturally related causes of syncope share hemodynamic similarities and are often managed with similar therapies. Compression stockings are one frequently prescribed non-pharmacological treatment for syncope, with the rationale that they minimise lower limb venous pooling and filtration and so prevent or delay syncope. However, research proving their efficacy is lacking. We aimed to investigate the effect of graded calf compression stockings on orthostatic tolerance. We evaluated orthostatic tolerance and haemodynamic control in 23 healthy volunteers wearing graded calf compression stockings in two separate placebo-controlled randomised double-blind trials. Placebo stockings tested were: (a) standard calf-length socks not designed to provide compression (n = 11); and (b) standard ankle-length socks that did not compress the calf (n = 12). Orthostatic tolerance was determined using combined head-

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Clin Auton Res (2010) 20:289–330 upright tilting and lower body negative pressure applied until presyncope. Beat-to-beat blood pressures, heart rate, stroke volume and cardiac output were recorded using finger plethysmography. Cerebral and forearm blood flow velocities were determined using Doppler ultrasound. End tidal gases were monitored on a breath-by-breath basis. There were no significant differences in orthostatic tolerance (time to presyncope) between compression stocking and calf (29.4 ± 2.3 and 26.8 ± 2.3 min) or ankle (24.0 ± 2.9 and 24.8 ± 1.8 min) placebo conditions. Cardiovascular, cerebral and respiratory responses were similar between compression stocking and placebo conditions. However, despite the lack of efficacy of compression stockings in the groups overall, certain individuals improved their orthostatic tolerance with compression stockings while others were worse. The efficacy of compression stockings was significantly related to anthropometric parameters (calf circumference, height and shoe size). These data question the rationale for the use of calf compression stockings for orthostatic intolerance and highlight the need for individualised therapy accounting for anthropometric variables when considering treatment with compression stockings.

Poster #22 Perceptions of exercise effects in younger patients with neurogenic orthostatic hypotension J.L. Gilden, T. Kim, T. Malledi, S. Maineni, S. Ubhayakar, D. Vahedi, A. Nuygen Rosalind Franklin University of Medicine and Science, Chicago Medical School and Saints Mary and Elizabeth Medical Center, Chicago, IL, USA Background: Neurogenic Orthostatic Hypotension (NOH) is characterized by a decrease in upright blood pressure with symptoms of cerebral hypoperfusion. The current treatment regimen includes: fluids, salt, exercise, and pharmacologic interventions. The optimal intensity and types of exercise for NOH are unclear. We evaluated the effects of exercise, perceptions of benefits, and muscle strength in younger NOH. Methods: 31 patients with NOH [(SBP decrease = 20 mmHg or DBP = 10 mmHg with inappropriate tachycardic response to bedside tilt and abnormal heart rate variability [(mean age = 37 years) (25 female:6 male) (BMI = 26.7 ± 8.2) (diagnosis NOH: 10 PAF:14 AI: 4 MVP:3 other)] were surveyed for history of exercise prior to NOH, types of current exercise regimens, and perceptions of benefits/tolerability, as well as subjective and objective tests of muscle strength (ability to stand, hand grip, and the ‘‘get up and go test’’). Results: Although exercise was recommended for all NOH, only 61% currently exercise, and 32% patients believed that exercise benefits their condition. 51% NOH felt more symptomatic from exercise, and 16% responded that they were unable to assess benefits of exercise. 84% patients stated that NOH prevented them from exercising more often. Patients who exercised had less SBP decrease (15.8 ± 10.7 vs. 19.9 ± 16.8 mmHg; p \ 0.05). Furthermore, SBP decrease was lower in non-weight bearing muscle strengthening (pilates, yoga, swimming, etc) versus weight bearing exercise (walking, jogging, etc) (11.5 ± 3.4 vs. 18.7 ± 13.0 mmHg). Despite subjective complaints, all patients had normal muscle strength. 77% exercised prior to the development of NOH, with 88% of those previously participating in athletic competition. Conclusion: Despite the beneficial effects of exercise, only 61% were able to adhere to these recommendations. In addition, subjective perceptions of muscle weakness did not correlate with objective measures. Understanding these obstacles may help to illuminate compliance issues with exercise recommendations for patients with neurogenic orthostatic hypotension.

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Poster #23 Poster #24 The influence of different wheelchair seating positions on cardiovascular control I.S. Sahota1,2, J.E. Camp1, C.S. Mah1, J.F. Borisoff2, L.T. McPhail2, V.E. Claydon1,2 1 Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada; 2 International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Vancouver, BC, Canada Introduction: Lightweight wheelchairs are available that allow users to adjust their seating position, offering improved comfort and increased independence. Our study examined whether cardiovascular control is affected by changes in seating position in two wheelchairs: Instinct Mobility’s Elevation and Levo’s LAE. Methods: We evaluated beat-to-beat heart rate (HR), blood pressures (BP; finger plethysmography) and cerebral blood flow velocity (CBFV; Doppler ultrasound), continuously for 15-min in supine, standard and upright (elevation = 688 and LAE = 858) seating positions. Stroke volume (SV), cardiac output and peripheral resistance responses were determined using the Modelflow technique. Evaluations were performed in healthy able-bodied subjects (Elevation: n = 13; LAE: n = 12). Results: BP increased (p \ 0.05) with both wheelchairs when subjects went from supine to standard or upright seating. CBFV decreased (Elevation p \ 0.05; LAE p \ 0.01) from supine compared to standard and upright wheelchair positions. HR was increased in all seating positions compared to supine (p \ 0.001), and increased further when upright compared to standard seating (p \ 0.05). With the Elevation wheelchair, SV showed a reciprocal pattern to HR, with significant decreases (p \ 0.001) in all positions compared to supine, and further decreases (p \ 0.05) when upright compared to standard seating positions. In the LAE, SV decreased (p \ 0.05) when upright compared to supine or standard seating. The magnitude of HR and SV responses from standard to upright seating were greater (p \ 0.05) with the LAE compared to the Elevation wheelchair. Discussion: These data suggest that transitions from supine to seated positions are not an inconsiderable orthostatic stress, even in healthy able-bodied people. The greater upright seating angle in the LAE may contribute to increased venous pooling and, consequently, larger changes in SV and HR. Further studies are warranted to elucidate the effect of altered seating positions on cardiovascular control in wheelchair users who may experience cardiovascular deconditioning, or with autonomic dysfunction, such as occurs with spinal cord injury.

Poster #25 ECG-based predictors for cardiac arrhythmias after spinal cord injury H.J.C. Ravensbergen1,2, M.L. Walsh1, A.V. Krassioukov2,3, V.E. Claydon1,2 1 Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada; 2 International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada; 3 GF Strong Rehabilitation Centre and Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada

313 Introduction: Individuals with spinal cord injury (SCI) have an increased risk for cardiac arrhythmias, particularly during autonomic dysreflexia. Impaired autonomic control of the heart after SCI may cause alterations in cardiac repolarisation. The interval between the peak and end of the T-wave of the electrocardiograph (ECG) provides an index of transmural dispersion of repolarisation, a factor underlying the development of ventricular arrhythmias. Variability in P-wave duration may be correlated with risk of atrial arrhythmias. We aimed to determine whether there is a difference in Tpeak-Tend and P-wave variability at rest in those with high level (above T5) SCI compared to those with lower level injuries (below T5) and able-bodied controls. A second aim was to determine correlations between ECG parameters and measures of autonomic impairment. Methods: We recorded an ECG continuously during 15 min of supine rest in 15 subjects with cervical SCI, 13 with thoracic SCI and 27 controls. ECG intervals (RR, QT, P-wave duration and Tpeak-Tend) were determined using customized software. Variability of these parameters was calculated using autoregressive spectral analyses. Autonomic severity of SCI was determined from sympathetic skin responses (SSR), and resting and upright noradrenaline (NA) levels. Results: We found significantly greater (p \ 0.05) Tpeak-Tend variability in those with high SCI compared to controls (93.21 ± 16.85 vs. 49.68 ± 12.68 ms2), although no difference was found in those with lower SCI. There was a trend for a negative correlation between Tpeak-Tend, SSR and the NA-change when upright. P-wave variability was increased in those with high SCI compared to controls (92.05 ± 31.97 vs. 28.58 ± 7.23). P-wave variability was negatively correlated to upright NA (r = -0.496, p = 0.035) and NA-change (r = -0.573, p = 0.047). Discussion: The higher Tpeak-Tend variability and P-wave variability in individuals with injury to cardiac autonomic pathways could be new risk assessment parameters for predisposition to cardiac (both ventricular and atrial) arrhythmias in this population.

Poster Session II Poster #26 Regional hypothalamic activity associated with spontaneous fluctuations in muscle sympathetic nerve activity in humans C. James1, L.A. Henderson2, V.G. Macefield1,3 1 School of Medicine, University of Western Sydney, Australia; 2 Department Anatomy and Histology, School of Medical Sciences, University of Sydney, Australia; 3 Prince of Wales Medical Research Institute, Australia Introduction: We have previously shown that it is possible to record spontaneous muscle sympathetic nerve activity (MSNA)—via microneurography—whilst performing functional magnetic resonance imaging (fMRI) of the brainstem of awake human subjects. We have identified the medullary circuitry involved in the regulation of the baroreflex (Macefield and Henderson 2010) and aim to further these findings by distinguishing suprabulbar regions involved in the generation of spontaneous MSNA. Methods: MSNA was recorded from the common peroneal nerve in 14 subjects. Gradient echo, echo-planar fMRI was performed using a 3T scanner (Philips Achieva). 200 volumes (46 axial slices, TR = 8 s, TE = 40 ms, flip angle = 90°, raw voxel size = 1.5 mm3) were

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314 collected in a 4 s-ON, 4 s-OFF protocol. Total sympathetic burst amplitudes were measured from the RMS-processed mean voltage amplitude during the final 3 s of the 4 s-OFF period. Blood Oxygen Level Dependent (BOLD) changes in signal intensity (SPM5: random effects, minimum cluster size 10 voxels, corrected false discovery rate p \ 0.05) were measured during the subsequent 4 sON period. Results: MSNA was positively correlated to signal intensity in the region of the paraventricular, lateral and the dorsomedial nuclei of the hypothalamus. Conclusions: We have identified three discrete regions of the hypothalamus in which neural activity covaries with spontaneous MSNA, supporting the idea that the hypothalamus contributes to the ongoing control of blood pressure at rest. Reference: Macefield VG and Henderson LA (2010) Real-time imaging of the medullary circuitry involved in the generation of spontaneous muscle sympathetic nerve activity in awake subjects. Human Brain Mapping 31: 539-549

Poster #27 Somatosensory inputs inhibit insular activation during baroreceptor unloading R. Goswami1, M.F. Frances1, J. K. Shoemaker1,2 1 School of Kinesiology, The University of Western Ontario, London, ON, Canada; 2 Department of Physiology and Pharmacology, The University of Western Ontario, London, ON, Canada This study tested the hypothesis that muscle sensory afferents and baroreceptors differentially affect regions in the cortical autonomic network. Based on previous research, it was expected that activity in the posterior insula would be increased during baroreceptor unloading with lower-body negative pressure (LBNP) and that this increase would be attenuated during concurrent muscle stimulation and LBNP. Seven participants (2 females; 23 ± 3 years) were studied while cortical activity was measured using functional magnetic resonance imaging, combined with heart rate (HR) recordings. Transcutaneous electrical nerve stimulation (TENS) at sub-motor threshold was performed over the forearm flexor muscles. LBNP at -30 mmHg was used to unload baroreceptors, and in turn increase sympathetic activity and HR. LBNP was performed with and without 30-s bouts of TENS to investigate the interactive effects. HR increased during LBNP (Rest: 59 ± 8; LBNP: 64 ± 10 bpm) (mean ± SD), with or without TENS. In a subtraction analysis of LBNP [ LBNP + Stimulation, greater activation was observed in the bilateral posterior insula during LBNP (p \ 0.001, uncorrected). LBNP + Stimulation was associated with deactivation in the mid right insula (p \ 0.001, uncorrected). At the individual level, LBNP increased activity in the left and right insula in five of seven individuals, and in six of seven individuals, respectively. Activity in the left insula during LBNP + Stimulation was observed in three participants while right insular activity occurred in two participants (p \ 0.005, uncorrected). These preliminary data indicate that somatosensory stimulation attenuates the insular activation induced by baroreceptor unloading. The data implicate an inhibitory effect of somatosensory afferents on sympathetic outflow during baroreceptor unloading, and that this interaction involves the posterior insula. This research was funded by the Heart and Stroke Foundation of Ontario.

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Poster #28 Cortical autonomic alterations with hypertension K.N. Norton1, R. Goswami1, R.P. Nolan2, J.K. Shoemaker1,3 1 School of Kinesiology, The University of Western Ontario, London, ON, Canada; 2 Division of Cardiology, Faculty of Medicine, University Health Network, University of Toronto, Toronto, ON, Canada; 3 Department of Physiology and Pharmacology, The University of Western Ontario, London, ON, Canada The role of cortical regions in mediating the impact of hypertension on parasympathetic control of heart rate (HR) is not known. This study tested the hypothesis that the medial prefrontal cortex (MPFC) is differentially involved in human cardiovagal control in normotensive (NT; n = 12; 57 ± 5 years; systolic blood pressure (SBP): 123 ± 9 mmHg, diastolic blood pressure (DBP): 75 ± 10 mmHg) versus hypertensive (HT; n = 11; 63 ± 6 years; SBP: 141 ± 12 mmHg, DBP: 92 ± 6 mmHg) populations. Functional magnetic resonance imaging was combined HR measures during a 30-s static handgrip (HG; 30% maximal strength) task that affects parasympathetic withdrawal. Cardiovagal baroreflex sensitivity (BRS; sequence method) was calculated. Baseline HR was higher in HT (68 ± 3 bpm) than NT (59 ± 2 bpm; p \ 0.05). Average BRS ranged from 16.4 ± 2.2 ms/mmHg in NT to 6.8 ± 1.7 ms/mmHg in HT groups (NS), which is below the average observed in previous studies of young subjects, 23 ± 5 ms/mmHg. Similar tachycardia was observed in response to HG (p \ 0.001) in both NT (59–63 bpm) and HT (68–70 bpm). In NT, the *4 bpm HR response was associated with deactivation in the MPFC and subgenual anterior cingulate (ACC; p \ 0.005, uncorrected). In contrast, no change was observed in the MPFC or ACC activation levels of HT individuals. Individual ‘‘responders’’ (R; n = 11) were identified by an increase in HR of [3 bpm to the HG task. MPFC deactivation was correlated with the HR time course and observed in each of the R subjects. No HR response or MPFC deactivation was observed in any ‘‘non-responder’’ (n = 12) individual. These results provide strong evidence for a brain-heart connection and indicate that HT itself does not directly predict BRS levels or HR response to HG in older individuals. If there is a response, the association between MPFC deactivation and HR is retained. Supported by the Heart and Stroke Foundation of Ontario.

Poster #29 Single-unit muscle sympathetic nerve activity responsiveness to lower body negative and positive pressure in healthy humans H. Murai, C.F. Notarius, B.L. Morris, D. Kimmerly, P. Picton, J.S. Floras Division of Cardiology, University Health Network and Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada For over 4 decades, efferent sympathetic traffic has been characterized in humans using multi-fibre recordings of muscle sympathetic nerve activity (MSNA), comprising the aggregate discharge of several single-units. However, unknown is whether all single-unit action potentials within a multi-fibre recording respond uniformly to the

Clin Auton Res (2010) 20:289–330 same afferent stimulus. In this study, we tested the hypothesis that lower body negative and positive pressure applied to achieve selective alterations in cardiac filling pressure would exert concordant effects on all individual units integrated into the multi-fibre neurogram. Method and results: Multi- and single-unit MSNA, arterial and central venous pressure, and heart rate were recorded in 9 healthy subjects during -10 mmHg (non-hypotensive) lower body negative pressure (LBNP) and +10 mmHg (non-hypertensive) lower body positive pressure (LBPP). As anticipated, multiunit MSNA rose from 33 ± 18 to 39 ± 17 bursts/min during LBNP (p \ 0.05) and fell to 31 ± 16 bursts/min with LBPP (p \ 0.05). Isolated, by super-imposition, were 24 single-units. Their responses to LBNP and LBPP displayed 2 distinct patterns. The firing rates of 20 (82%) single-units significantly increased during LBNP (+18 ± 17 spikes/min, p \ 0.05) and decreased during LBPP (-5 ± 11 spikes/min, p \ 0.05). By contrast, the firing rates of 4 (18%) single-units decreased during LBNP (-4 ± 2 spikes/min) and increased during LBPP (+10 ± 6 spikes/min). Conclusion: In healthy humans, some single-unit sympathetic vasoconstrictor fibers within the multi-unit recording respond paradoxically to cardiopulmonary baroreflex unloading and stimulation. Consequently, multiunit recordings of MSNA underestimate the magnitude of individual fibre responsiveness to such stimuli. In conditions characterized by altered cardiopulmonary reflexes, singleunit MSNA analysis may provide novel insight into the diversity of mechanisms regulating efferent sympathetic discharge.

Poster #30 Sympathetic and cardiovascular responses to glossopharyngeal insufflation in trained apnea divers K. Heusser1, G. Dzamonja2, T. Breskovic3, C. D. Steinback4, A. Diedrich5, J. Tank1, J. Jordan1, Z. Dujic3 1 Institute of Clinical Pharmacology, Hannover Medical School, Hannover, Germany; 2 Department of Neurology, Clinical Hospital Split, Split, Croatia; 3 Department of Physiology, University of Split School of Medicine, Split, Croatia; 4 Neurovascular Research Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario Canada; 5 Autonomic Dysfunction Service, Vanderbilt University, Nashville, TN, USA Glossopharyngeal insufflation (lung packing) is a common maneuver among experienced apnea divers to increase air volume within the lungs. Hypotension and syncope can occur. We tested the hypothesis that the packing-mediated increase in intrathoracic pressure enhances the baroreflex-mediated increase in MSNA in response to an exaggerated drop in cardiac output (CO). We compared changes in hemodynamics and MSNA (peroneal microneurography) during maximal breath-holds with and without prior moderate packing (0.79 ± 0.40 l) in 14 trained divers (12 men, 2 women, 26.7 ± 4.5 years, BMI 24.8 ± 2.4). Packing did neither change apnea time (3.8 ± 1.0 vs. 3.8 ± 1.2 min), nor hemoglobin oxygen desaturation (17.6 ± 12.3 vs. 18.7 ± 12.8%), nor the reduction in CO (1 min: 3.65 ± 1.83 vs. 3.39 ± 1.96 l/min, end of apnea: 2.44 ± 1.33 vs. 2.16 ± 1.44 l/min). Lung packing dampened the early increase in mean arterial pressure (MAP, 1 min: 9.2 ± 8.3 vs. 2.4 ± 11.0, p \ 0.01) and in total peripheral resistance (relative TPR, 1 min: 2.1 ± 0.5 vs. 1.9 ± 0.5, p \ 0.05) and augmented the concomitant rise in MSNA (1 min: 28 ± 12 vs. 39 ± 13 bursts/min, p \ 0.001; 33 ± 16 vs. 44 ± 15 bursts/100 heart beats, p \ 0.01; 3.3 ± 2.1 vs. 4.8 ± 3.2 au/min, p \ 0.05). Our data suggest that

315 moderate packing induces additional sympathoactivation which cannot be explained by excessive reduction in CO. The finding of lower MAP despite increased MSNA after packing might be explained by vasodilator substances released by the lungs.

Poster #31 Mental stress attenuates sympathetic baroreflex sensitivity in humans J.R. Carter, J.J. Durocher, C.E. Schwartz, J.C. Klein Department of Exercise Science, Health and Physical Education, Michigan Technological University, Houghton, MI, USA Mental stress (MS) consistently increases arterial blood pressure, and this pressor response is often accompanied by a paradoxical increase of muscle sympathetic nerve activity (MSNA). It has been suggested that MS-induced sympathoexcitation may be due, in part, to altered baroreflex function, but this has not been definitively determined. By examining the relations between spontaneous fluctuations of diastolic arterial pressure (DAP) and MSNA, we tested the hypothesis that sympathetic baroreflex sensitivity (BRS) would be attenuated during mental stress. MSNA and DAP were recorded during 5 min of supine baseline and 5 min of MS in 11 healthy adults (age 22 ± 2 years). The burst incidence (bursts per 100 cardiac cycles) and area of each burst were determined for each cardiac cycle and placed into 3 mmHg DAP bins; the slopes of the relations between MSNA and DAP provided an index of sympathetic BRS. During supine baseline, the relation between MSNA and DAP was negative when expressed as either burst incidence (slope = -1.72 ± 0.21; r = -0.81 ± 0.05; n = 10) or total MSNA (slope = -569 ± 112; r = -0.80 ± 0.04; n = 8). During MS, the slope of the relation between burst incidence and DAP became significantly (P \ 0.05) more positive (slope = -1.07 ± 0.16; r = -0.72 ± 0.04), indicating an attenuation of the sympathetic BRS. In contrast, MS did not alter the total MSNA slope (slope = -614 ± 116; r = -0.74 ± 0.04). In conclusion, the present study demonstrates that MS attenuates sympathetic BRS when expressed as burst incidence. This attenuation of sympathetic BRS is likely a contributor to MSinduced sympathoexcitation at a time when arterial baroreflexes typically reduce MSNA.

Poster #32 Autonomic tests: possible link between body composition and vulnerability to stress in healthy young adults S. Ghosh Department of Physiology, Faculty of Medicine, MAHSA University College, Kuala Lumpur, Malaysia Basal autonomic status of individuals needs to be assessed to identify the link between autonomic nervous system, body composition and vulnerability to stress in normal apparently healthy young adults. Medical students have been known to undergo tremendous stress during various stages of the MBBS course and some break down while others are able to cope up with the same. The present study was aimed to find

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316 out the relationship between self perceived level of stress, autonomic reactivity to mental stress and body composition in a group of young adult healthy male medical students and also to find if altered reactivity in the autonomic nervous system can determine the individual’s vulnerability to mental stress. Basal autonomic status was assessed by standard methods at rest and after application of mental stress in first year medical students. Sources of stress with stress coping strategies and resilience were assessed by a pre validated structured questionnaire. All data were expressed as mean ± SEM and statistical significance was assessed by using Student’s ‘T’ test and correlation. All students considered academic factors as the primary source of stress. Mental stress caused significant increases in the cardiovascular parameters as compared to rest. Students showing normal range of responses in heart rate with autonomic testing also were the ones who showed lesser alterations upon application of stress. Students with both high and low body fat % showed significant alteration of autonomic activity as compared to those with normal range of body fat %. It can therefore be concluded that the medical students considered academic stress as the most important stress inducer in the first year of their medical course and mental stress induced significant increases in cardiovascular parameters, which depended on the basal autonomic status and also the range of body fat %.

Poster #33 Does yogic breathing increase baroflex gain? S.M. Bertisch1,2, C.O. Tan2,3, J.A. Taylor2,3 1 Division of General Medicine and Primary Care, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA; 2 Cardiovascular Research Laboratory, Spaulding Rehabilitation Hospital, Boston, MA, USA; 3 Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA, USA Background: Nearly one in five Americans practice meditative therapies annually. While some purport meditative practices, such as yoga, improve cardiovascular health via shifting sympathovagal balance, sparse data exist on the effects of these practices upon autonomic cardiovascular control. In this context, we hypothesized that yogic breathing differentially impacts fluctuations in RR-interval and systolic blood pressure compared with paced respiration at 0.25 Hz. Methods: We enrolled five healthy advanced yoga practitioners. We continuously measured heart rate, beat-by-beat blood pressure, respiratory rate, inspiratory volume, and end-tidal CO2 during paced respiration (10 min) and yogic breathing (20 min). For yogic breathing, we asked practitioners to perform a slow technique that they practice regularly. We performed standard time and frequency domain analyses. Results: In this group of practitioners, yogic breathing was characterized by a mean respiratory rate of 4.32 ± 1.87 breaths/min, mean minute ventilation of 6.09 ± 4.17 L/min, and mean end-tidal CO2 of 39.98 ± 7.07 mmHg compared with a mean respiratory rate of 15.0 ± 0.60 breaths/min, minute ventilation of 8.66 ± 2.25 L/min, and mean end-tidal CO2 of 32.68 ± 5.22 mmHg during paced respiration. Mean coherence between respiratory volume and RR interval and respiratory volume and systolic blood pressure did not differ between the two breathing patterns (p = 0.74 and p = 0.14). However, we found increased gain between respiration and RR-interval fluctuations (400.00 ± 154.19 ms/L vs. 36.65 ± 10.32 mmHg/L, p = 0.02) and between respiration and systolic blood pressure fluctuations (15.97 ± 9.32 ms/L vs. 1.68 ± 0.68 mmHg/L, p = 0.02) during yogic breathing compared with paced respiration. Conclusion: Whether the larger gain relation between respiration and cardiovascular fluctuations during yogic breathing represents modulation

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Clin Auton Res (2010) 20:289–330 of baroreflex gain or is simply due to enhanced entrainment through repetitive practice remains to be established. However, these preliminary findings may explain some of yoga’s reported cardiovascular benefits.

Poster #34 Can meditation influence the autonomic nervous system? A case report of a man immersed in crushed ice for 80 minutes J.T. Groothuis1,3, T.M. Eijsvogels1, R.R. Scholten1,2, D.H.J. Thijssen1,4, M.T.E. Hopman1 1 Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; 2 Department of Obstetrics and Gynaecology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; 3 Department of Rehabilitation, St Maartenskliniek, Nijmegen, The Netherlands; 4 Research Institute for Sports and Exercise Sciences, Liverpool John Moores University, Liverpool, UK Background: The autonomic nervous system responds independently, autonomously and automatically to changes in the homeostasis of the cardiovascular system and thermoregulation. However, the world record holder of full-body ice immersion claims he can influence his autonomic nervous system through the Asian Tummo meditation technique, which is associated with descriptions of intense sensations of body heat. We, therefore, assessed the cardiovascular and thermoregulatory responses to full-body ice immersion in this individual. Methods: A 51-year-old male was fully immersed in crushed ice for 80 min whilst performing Asian Tummo meditation. Blood pressure and heart rate were measured continuously using an automatic blood pressure device. Core body and skin temperature were measured continuously using an ingestible telemetric temperature pill and wireless sensors, respectively. Oxygen consumption was measured using pulmonary gas exchange every 30 min. Results: Core body temperature during the 80-min ice immersion period decreased gradually from 37.7 to 37.1°C. Skin temperature decreased at the upper limbs from 28 to 5°C and at the lower limbs from 28 to 18°C. No immediate blood pressure or heart rate response at the beginning of full-body ice immersion was observed. Over the full 80-min ice immersion period, blood pressure gradually increased from 128/84 to 163/97 mmHg and heart rate from 70 to 90 bpm. Oxygen consumption doubled from 5.7 at baseline to 11.0 ml/min/kg during immersion and remained stable. Conclusions: No immediate blood pressure and heart rate responses were observed, as typically observed when (partially) submerged into ice (water). Despite 80 min of full-body ice immersion and significant heat loss through the skin, core body temperature was maintained probably by an increased energy expenditure (and therefore heat production). This individual may have influenced the autonomic nervous system, thereby actively regulating the cardiovascular system and thermoregulation.

Poster #35 Use of electrical impedance to measure sympathetic activity of human skin I. Wexler Delaware Neurology Associates, Lewes, DE, USA

Clin Auton Res (2010) 20:289–330 Deep inspiration causes increased eccrine sweat gland activity in human glabrous skin and also induces cutaneous vasoconstriction (Gilliatt et al. 1948). Thus, two separate indicators of sympathetic activity, one cholinergic (sweating), the other adrenergic (circulation) are potentially measurable from the skin’s surface. Unlike sweating, which is easily measured as a change in the skin’s electrical potential (galvanic skin response, GSR; sympathetic skin response, SSR), circulatory changes are more difficult to measure and require advanced technical methods. We investigated the use of electrical impedance (the resistance to passage of an AC current through a volume conductor) as a novel technique for measuring dynamic changes in skin circulation, testing the hypothesis that skin impedance increases during cutaneous vasoconstriction when blood flow is reduced and, alternatively, decreases when blood flow is increased during vasodilatation. We found that cutaneous vasodilatation induced by foot warming caused impedance of the sole to fall. Impedance also fell when venous blood was made to pool in the foot by means of a restricting cuff placed around the leg. Vasoconstriction followed by vasodilatation in leg blood vessels (the veno-arteriolar reflex, VAR; Hendriksen and Siersen 1977) caused impedance to increase during the initial (vasoconstrictor) phase, followed by a drop in impedance during subsequent vasodilatation. Deep inspiration had a paradoxical effect on impedance, depending upon the skin’s initial temperature: when cool (B28°C.) and sympathetic tone presumably high, skin impedance generally increased with inspiration. When the skin was initially warm (C30°C.) and sympathetic tone presumed low or absent, inspiration caused impedance to fall further, suggesting that some mechanism for additional vasodilatation had been activated. From these initial studies, it appears that electrical impedance can follow changes in skin circulation brought on by greater or lesser sympathetic tone. The method has the additional advantages of being non-invasive, relatively inexpensive and can easily be incorporated into the standard EMG/nerve conduction examination.

Poster #36 Melatonin differentially affects vascular blood flow in humans J.S. Cook2, C.L. Sauder1, C.A. Ray1,2 1 Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA, USA; 2 Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA, USA Melatonin is synthesized and released into the circulation by the pineal gland in a circadian rhythm. Melatonin has been demonstrated to differentially alter blood flow to assorted vascular beds by MT1 versus MT2 melatonin receptor activation and melatonin concentration in animal models. The purpose of the present study was to determine the effect of melatonin on blood flow to various vascular beds in humans. Renal (Doppler ultrasound), forearm (venous occlusion plethysmography), calf (venous occlusion plethysmography) and cerebral blood flows (transcranial Doppler), arterial blood pressure, and heart rate were measured in 10 healthy subjects (29 ± 1 years; 5 male, 5 female) while lying on a table for 3 min. The protocol began 45 min after the ingestion of either melatonin (3 mg) or placebo (sucrose). Subjects returned at least 2 days later at the same time of day to repeat the trial after ingesting the opposite drug. Melatonin did not alter heart rate and mean arterial pressure. Renal blood flow velocity (RBFV) and renal vascular conductance (RVC) were lower during the melatonin trial as compared to

317 placebo (RBFV: 40 ± 3 vs. 45 ± 2 cm/s; RVC: 0.47 ± 0.02 vs. 0.54 ± 0.01 cm/s/mmHg, respectively). In contrast, forearm blood flow (FBF) and forearm vascular conductance (FVC) were greater with melatonin compared to placebo (FBF: 2.4 ± 0.2 vs. 1.9 ± 0.1 ml/100 ml/min; FVC: 0.029 ± 0.003 vs. 0.023 ± 0.002 a.u., respectively). Melatonin did not alter calf or cerebral blood flow measurements compared to placebo. In summary, exogenous melatonin differentially alters vascular blood flow in humans. These data suggest the complex nature of melatonin on the vasculature in humans.

Poster #37 Influences of an acute ozone exposure on heart rate and blood pressure variability in healthy subjects J. Tank1, K. Heusser1, H. Biller2, W. Koch2, A. Diedrich3, N. Krug2, J. Jordan1, J. Hohlfeld2 1 Institute of Clinical Pharmacology, Hannover Medical School, Hannover, Germany; 2 Fraunhofer Institute for Toxicology and Experimental Medicine (ITEM), Department Clinical Airway Research, Hannover, Germany; 3 Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Service, Vanderbilt University School of Medicine, Nashville, TN, USA In epidemiological studies, increased ozone exposure is associated with reduced 24 h heart rate variability (HRV) and excessive mortality due to pulmonary disease. Data on the effects of experimental ozone exposure on HRV and blood pressure variability (BPV) are lacking. In a double blind, randomized, and cross-over fashion, we exposed 15 healthy volunteers to ozone (250 ppb) or filtered air in a challenge chamber for 3 h. Subjects exercised intermittently on a bicycle ergometer to increase ventilation to 20 l/min/m2. Twenty hours after end of exposure, we measured heart rate variability, blood pressure variability, spontaneous baroreflex sensitivity, muscle sympathetic nerve activity (MSNA), cardiac output with a rebreathing technique, and plasma catecholamines at rest followed by autonomic reflex tests. The percentage of neutrophils in induced sputum obtained 6 h after the start of challenge was increased after ozone compared to clean air. Supine blood pressure, heart rate, cardiac output, plasma norepinephrine levels, and MSNA were almost identical on both study days. HRV and BPV at supine rest and during deep breathing analyzed by spectral and cross spectral analysis were similar on both study days as was the spontaneous baroreflex sensitivity (sequence and cross spectral technique). Our findings suggest that an acute exposure to ozone does not induce a major change in HRV or BPV in healthy subjects.

Poster #38 Blood pressure variability after heart transplantation: patterns and probable mechanisms O.V. Mamontov, A.O. Konradi, E.V. Shlyakhto Almazov Federal Heart, Blood and Endocrinology Centre, St. Petersburg, Russian Federation Despite an increase in cardiac index after heart transplantation (HT), the complete disappearance of chronic heart failure (CHF) is not

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318 observed. This is probably due to imperfections of blood flow regulation associated with denervation of the heart. Aim: To assess changes of the blood pressure variability and its oscillation damping after heart transplantation. Patients and methods: We assessed 5 patients with coronary heart disease, cardiomegaly, congestive heart failure III–IV functional class, ejection fraction 18.4 ± 3.7%. Three of them were examined before and 1 month after HT. All patients were evaluated for autonomic regulation of circulation by means of the tilt-test and Valsalva maneuver. Hemodynamic parameters were recorded by Finapres method using beat-to-beat monitor Finometer-Pro with the following calculation of blood pressure variability and heart rate dynamic during Valsalva maneuver. Results: One month later after operation ejection fraction was 69 ± 2.9%. The survey revealed that in patients after HT tolerance to orthostasis is not reduced. Dynamics of arterial pressure before and after HT in orthostasis were: systolic —6.2 ± 8.5 and 1.7 ± 6.3 mmHg, p [ 0.05, diastolic 2.7 ± 7.9 and 3.1 ± 6.4 mmHg, p [ 0.05. Despite the small number of observations, revealed that after HT blood pressure variability (VAD) is significantly changed. In the very-low frequency range (VLF) was significantly lower: 53.3 ± 32.4 and 12.0 ± 3.3 mmHg2, p \ 0.05 whereas high-frequency (HF), on the contrary—is much higher: 4.9 ± 2.8 and 14.3 ± 3.7 mmHg2, p \ 0.05. At that time in orthostasis VAD in the HF range in patients with HT was growing more: at 1.1 ± 2.1 and 7.8 ± 7.7 mmHg2, p \ 0.05. Revealed changes in patients with HT were combined with the inversion of heart rate dynamics in third phase of Valsalva maneuver. In postoperative patients on a background of BP reduction observed decrease in heart rate at -0.092 ± 0.07 s, but it does not increase as the patients before surgery (to 0.31 ± 0.22 s), p \ 0.05. Conclusion: Thus, absence of neurogenic regulation of the heart in early period after HT leads to the paradoxical heart rate fluctuations in response to respiratory movements, and that probably causes the increase of blood pressure fluctuations associated with fluctuations in venous return in the process of respiration.

Poster #39 Valsalva maneuver: shortest optimal expiratory strain duration R.K. Khurana, D. Mittal, N.H. Dubin Department of Medicine, Union Memorial Hospital, Baltimore, MD, USA Background: Expiratory strain duration, an important confounding variable in the Valsalva maneuver (VM), varies from 10 s to 20 s in different laboratories. Moreover, patients find it difficult to sustain prolonged VM. Aim: To determine the shortest optimal expiratory strain duration which could be best tolerated by individuals and retain clinical usefulness in evaluating heart rate (HR) and blood pressure (BP) responses. Methods: HR and BP (Finapres, Ohmeda 2300) were recorded in 34 healthy subjects in response to three durations of expiratory strain: 10, 12, and 15 s in random order. For each VM trial, participants assessed the level of difficulty on a scale of 1–10. Delineation of four expected phases of BP responses to the VM was evaluated, and poorly delineated responses were counted. Analyzed parameters were BP phases II E and II L, tachycardia latency (TL), bradycardia latency (BL), systolic

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Clin Auton Res (2010) 20:289–330 overshoot latency (OV-L), and Valsalva ratio (VR). Data were analyzed by analysis of variance and expressed as mean ± SEM. Results: Thirty-four subjects performed 306 trials. Difficulty scores increased significantly (p \ 0.001) with increasing expiratory duration. Difficulty score was 5.1 ± 0.1 with 10 s, 5.9 ± 0.1 with 12 s, and 6.8 ± 0.1 with 15 s. Phase II of VM was poorly delineated in 30 of 102 trials with 10 s of expiratory strain duration compared with 5 of 102 trials with 15 s of expiratory strain duration. BP II E, TL, BL, OV-L, and VR responses did not differ statistically with increasing expiratory strain durations, nor were there differences in the variability. However, BP response of II L phase showed statistically significant increase with increasing expiratory strain duration. Conclusion: Difficulty performing the VM increased with increasing expiratory duration. Ten seconds expiratory duration is insufficient for phase II L BP response. Other parameters, however, remain useful with a low level of difficulty.

Poster #40 Autonomic imbalance may underlie labile hypertension: I. Possible remedy E.S. Pereira1, S. Baker1, R. Bulgarelli2, R.R. Arora3, S. Ghosh-Dastidar4, J. Colombo4 1 Baker-Gilmour Cardiovascular Institute, Jacksonville, FL, USA; 2 Cardiology Division, Riddle Memorial Hospital, Media, PA, USA; 3 Department of Cardiology, The Chicago Medical School, Chicago, IL, USA; 4 ANSAR Medical Technologies, Inc., Philadelphia, PA, USA Clinical disorder is documented when parasympathetic excess (PE) occurs during sympathetic challenge. PE may cause instability in response to disease and therapy in Labile Hypertension (LH) patients. P&S and BP data obtained using the ANX 3.0 Autonomic Monitor (ANSAR, Philadelphia, PA) were collected during a standard clinical study including rest, Valsalva, and stand challenges. P&S assessments were performed for 388 hypertensive patients (64.0 years; 244 Female), 60 assigned as controls: 219 demonstrated high BP; 173 demonstrated PE. A total of 127 PE patients (97 experimental, 30 control) demonstrated PE and high BP. Of 175 experimental hypertension patients, 94 were diagnosed with LH and included in the 97 PE and hypertension patients (PE + HTN). Following baseline P&S testing, the experimental group received either 6.25 mg, bid, Carvedilol or 12.5 mg QD (dinner) Amatriptyline to treat PE. The control group did not. At the end of the study, follow-up P&S testing revealed that all 30 control, PE + HTN patients still tested positive for PE + HTN. The same 27 diagnosed as LH still demonstrated widely varying BP. These patients demonstrated an average BP of 144/107 unchanged from 145/109. For the rest of the (frank) control hypertensives, the average BP decreased from 146/109 to 125/89. In the experimental LH group, all BP fluctuations were relieved and BP decreased from 141/107 to 118/71. BP decreased from 141/107 to 121/73 in the experimental, frank HTN group. In the experimental, LH subpopulation, 73% of the patients reduced Carvedilol to 3.125 mg bid and 32% reduced their HTN medications. Also, 92% of the experimental LH subpopulation remaining on PE therapy significantly decreased HTN therapy by 63%. The experimental, frank HTN subpopulation continued baseline dosing. Additional PE therapy in LH patients seems to assist in stabilizing and normalizing BP. Often, correcting PE reduced the patient’s need for medication to maintenance doses.

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Poster #41 Autonomic imbalance may underlie labile hypertension: II. Possible physiology S. Baker1, E.S. Pereira1, R. Bulgarelli2, R.R. Arora3, S. Ghosh-Dastidar4, J. Colombo4 1 Baker-Gilmour Cardiovascular Institute, Jacksonville, FL, USA; 2 Cardiology Division, Riddle Memorial Hospital, Media, PA, USA; 3 Department of Cardiology, The Chicago Medical School, Chicago, IL, USA; 4 ANSAR Medical Technologies, Inc., Philadelphia, PA, USA Parasympathetic and sympathetic (P&S) assessment (ANX 3.0, Autonomic Monitoring, ANSAR, Philadelphia, PA) enables independent, simultaneous measures of P&S activity. Parasympathetic excess (PE) is an abnormal increase in P activity in response to S challenge (e.g., Valsalva and stand). In a companion abstract, a study was documented comparing 388 hypertension patients (64.0 years; 244 female). An experimental group of 328 patients (64.0 years; 208 female), included 94 with labile hypertension (LH), the rest with frank hypertension. The remaining 60 patients (64.1 years; 36 Female) comprised the control group, including 30 LH patients. LH patients demonstrated PE with hypertension. Eighteen months additional PE therapy (low dose Carvedilol or Amatriptyline) relieved all fluctuations in BP and the PE in the experimental group and none in the control group. Therapy reduced the average experimental, LH patient’s BP from 141/107 to 118/71 and from 145/109 to 144/107 in the control group. The average frank hypertension patient’s BP decreased from 141/107 to 121/73 and from 146/109 to 125/89, for experimental and control, respectively. Carvedilol includes two compounds: a non-selective-beta-adrenergicantagonist and an alpha-1-adrenergic-antagonist. Carvedilol’s alphacomponent is reported to change activity sites with autonomic neuropathy, indirectly reducing PE. Reducing PE is Amatriptyline’s function. PE is reported to be the primary autonomic abnormality; accompanying sympathetic excess (SE), secondary. As reported elsewhere, treating the SE as the primary imbalance exacerbates concurrent PE and SE, leading to poor outcomes. Treating the PE primarily relieves the condition, leading to improved outcomes. SE is well documented to underlie hypertension and is demonstrated in both frank and labile hypertensives. PE is demonstrated only in LH patients. Therefore, PE seems to be the cause of instability and BP fluctuation, perhaps by forcing a greater SE during a sympathetic challenge (stress or exertion), without affecting resting sympathetic levels.

Poster #42 Baroreflex sensitivity associates with salt-sensitivity in patients with resistant hypertension A.O. Konrady1, I.V. Emelyanov1, A.Y. Bagrov2, E.V. Shlyakhto1 1 Almazov Federal Heart, Blood and Endocrinology Centre, St. Petersburg, Russia; 2 National Institute on Aging, NIH, Baltimore, MD, USA Objective: To assess the relationship between pressor response to saltloading (SL) and spontaneous baroreflex sensitivity (BRS) in patients with resistant hypertension (RHTN) and its associations with saltsensitivity of blood pressure (BP). Design and methods: We studied 34 patients (17 males, 17 females; 56 ± 6 yrs) with RHTN (taking combination antihypertensive

319 therapy (lisnopril 20 mg + amlodipine 10 mg + hydrochlorothiazide 25 mg per day and BP over 140/90 mmHg) and 6 healthy normotensive subjects (3 males, 3 females; 54 ± 2 years). SL was performed via i.v. infusion of 1,000 mL saline for 1 h. Beat-to-beat BP was registered using Finometer Pro device (Netherlands). Spontaneous BRS was calculated by sequence method. Results: Within 1 h of SL patients with RHTN exhibited elevation of systolic (SBP) and diastolic BP (DBP) (from 188 ± 6 to 161 ± 4 mmHg for SBP and from 104 ± 2 to 89 ± 2 mmHg for DBP, both p \ 0.01 vs. baseline). In 1 h after SL BP returned close to baseline level (158 ± 4 and 86 ± 2 mmHg, respectively). At baseline spontaneous BRS in RHTN was significantly lower compared to controls (5.61 ± 0.08 vs. 6.60 ± 0.10 ms/mmHg; P \ 0.05). Moreover, at peak of saline infusion BRS was also lower in patients with RHTN than in controls (4.81 ± 0.12 vs. 6.70 ± 0.10 ms/mmHg; P \ 0.01). In hypertensive patients BRS changes negatively correlated with the magnitude of NaCl-induced elevation of SBP (r = 0.48; P = 0.02) and DBP (r = -0.44; P = 0.04) BP. Hypertensive patients were subdivided on two groups: salt-resistant [SL-induced BP elevation \20 mmHg for both SBP and DBP (n = 15)] and saltsensitive [SL-induced BP elevation = 20 mmHg for SBP and/or DBP (n = 19)]. Spontaneous BRS at baseline was similar in both groups. In salt-sensitive patients a significant correlation of BRS delta with peak DBP delta was observed (r = -0.53; P = 0.02), while in saltresistant no such relation was documented. The final BRS was lower in salt-sensitive that in salt-resistant group (4.1 ± 0.12 vs. 5.8 ± 0.10 ms/mmHg; P \ 0.001). Conclusion: In patients with RHTN, spontaneous BRS is decreased and is negatively associated with the level of pressor response to SL. BRS inhibition during SL is observed only in salt-sensitive RHTN.

Poster #43 Autonomic nervous system and insulin sensitivity A. Gamboa1, L.E. Okamoto1, A. Diedrich1, G. Farley1, S.Y. Paranjape1, K. Jabbour2, N. Abumrad2, I. Biaggioni1 1 Department of Medicine, Vanderbilt University, Nashville, TN, USA; 2 Department of Surgery, Vanderbilt University, Nashville, TN, USA Objective: To examine the role of the autonomic nervous system in obesity-associated insulin resistance. Background: Several mechanisms are thought to contribute to insulin resistance in obesity, and sympathetic activation is proposed to play a role. The initial compensatory mechanism to insulin resistance is increased production of insulin. This hyperinsulinemia is proposed to increase central sympathetic outflow. We hypothesized that autonomic nervous system blockade would result in improvement in insulin resistance in obese subjects. Methods: Insulin sensitivity (hyperinsulinemic euglycemic clamp) was determined twice in obese subjects (30 \ BMI \ 40 kg/m2), during intact, or pharmacologically induced autonomic blockade (trimethaphan 4 mg/min continuous IV infusion). Blood pressure was clamped during insulin and autonomic blockade by concomitant titrated intravenous infusion of the NOS inhibitor L-NMMA. Results: Six obese subjects (34 ± 0.9 k/m2 of BMI, 43 ± 6 years old, with blood pressure of 141 ± 4/83 ± 3 mmHg) were studied. Rates of glucose utilization (mg/kg lean body mass per min) during the clamp were not different between the intact or blocked study days (5.9 ± 0.9 vs. 5.8 ± 0.8 mg/kg/min for the intact and blocked days, p = 1.0 by Wilcoxon matched-pairs signed rank test, figure). However, baseline muscle sympathetic nerve activity was not increased

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320 (14 ± 1.6 burst/min) in this group of patients. We conclude that sympathetic nervous system does not contribute to insulin resistance in a cohort of obese subjects with normal sympathetic activity.

Poster #44 Autonomic function in mildly obese sleep apnea patients A.C. Peltier1, K. Bagai1, A. Diedrich2, E. Garland2, Y. Shi3, L. Wang3, D. Robertson1,2, B. Malow1 1 Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA; 2 Department of Medicine, Division Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA; 3 Department of Biostatistics, Vanderbilt University Medical Center, Nashville, TN, USA Obstructive sleep apnea (OSA) is associated with hypertension and cardiovascular disease, which is postulated to result from increased sympathetic activity induced by chronic intermittent hypoxia. Hyperglycemia is highly prevalent in OSA patients and may contribute to dysautonomia. Thirty-five patients with OSA [body-mass index (BMI) 32 ± 4.6] and 11 healthy controls (BMI of 29 ± 3.5) completed polysomnography, glucose tolerance testing, autonomic function tests, lying and upright plasma catecholamine determinations, overnight urine catecholamine measurement, and ECG and continuous blood pressure measurements for spectral analysis. A linear regression model adjusting for age, BMI, glucose and apnea hypopnea index (AHI, a measure of apnea severity) was used to analyze spectral data and catecholamines; other data were analyzed with the Wilcoxan test. Indices of heart rate variability included low frequency (LF) power, high frequency (HF) power, total power, Pnn50, and LF/HF ratio, a measure of sympathetic tone. AHI was 20.8 ± 16.5 in the OSA group. Nineteen OSA patients and two controls had hyperglycemia (using 2001 ADA criteria) (p = 0.11). Baseline heart rate was higher among OSA patients (68 vs. 58 beats per minute, p = 0.043) than controls. AHI correlated with LF power, (r = 0.131, p = 0.013) but not with LF/HF ratio (p = 0.25). Glucose had a negative correlation with LF and total power which remained a trend after adjustment for other variables (r = -0.187, p = 0.034; r = -0.159, p = 0.043). AHI correlated with supine norepinephrine (p = 0.019) but non-significantly after adjusting for age and BMI (p = 0.12). No differences in other autonomic tests were observed in OSA patients compared to controls. These data suggest that mildly obese OSA patients have minimal abnormalities in autonomic function and no evidence of increased sympathetic activity. Patients with diabetes were excluded, so effects of glucose may be minimized in this study. Age significantly affected results and should be considered carefully in studies of OSA and autonomic function.

Poster #45 Assessment of cerebral autoregulation and baroreflex in first-ever ischemic stroke patients S.J. Yeh1, C.C. Chiu2, B.Y. Liau3 1 Department of Neurology, Cheng-Ching General Hospital, Taiwan; 2 Institute of Automatic Control Engineering, Feng Chia University, Taiwan; 3 Department of Bioengineer, Hong-Kung Science University, Taiwan

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Clin Auton Res (2010) 20:289–330 Ischemic stroke can be resulted from unstable cerebral blood flow (CBF) due to the impairment of cerebral autoregulation (CA) and baroreflex (BR). If CA and BR can be monitored simultaneously, it would be helpful for management of stroke in clinical practice. The main purpose of this study is to assess CA and BR in first-ever ischemic stroke patients. Ten stroke patients (56.0 ± 10.6 years) and 11 healthy subjects (58.4 ± 8.0 years) are enrolled in this study. Blood pressure (BP), CBF velocity and heart rate signals are obtained in both supine and head-up tilting positions from Finapres and TCD. CA and BR were obtained and analyzed by using linear approaches. BP and CBF in stroke were higher than those in healthy persons (supine MABP: 88.3 ± 8.2 vs. 118.0 ± 17.5, p \ 0.05; supine CVF velocity: 58.5 ± 9.8 vs. 73.0 ± 10.2, p \ 0.05). Low frequency power of BP and CBF velocity in stroke patients lowered than those in healthy subjects (supine MABP LF = 3.7 ± 2.2 vs. 6.54 ± 2.2, p \ 0.05; supine MCBF velocity LF% = 51.2 ± 16.1 vs. 63.4 ± 8.6). In the analysis of CA by cross correlation function (CCF), the phase shift time lead in healthy subjects was higher than that in stroke subjects (1.68 ± 0.84 vs. 0.35 ± 3.36 s, p [ 0.05) and max CCF values was also higher than that in stroke subjects (0.57 ± 0.13 vs. 0.25 ± 0.07, p \ 0.05), it might indicate CA was more effective in healthy persons. The value of spontaneous baroreflex sensitivity (BRS) in healthy subjects was also significantly higher than that of stroke patients (supine: 7.29 ± 0.88 vs. 5.50 ± 1.25, p \ 0.05; tilt: 6.43 ± 0.98 vs. 5.37 ± 0.95, p \ 0.05). CA and BR in first-ever ischemic stroke patients are affected and impaired simultaneously. It might be partially due to impaired sympathetic function in stroke patients. CA and BR by CCF and BRS methods simultaneously, seem to be a simple and potential powerful method to investigate ischemic stroke.

Poster #46 Increased baroreflex sensitivity correlates with clinical improvement of acute stroke M.J. Hilz1,3, H. Marthol1, A. Akhundova1, P. De Fina2, S. Schwab1, S. Moeller1 1 Department of Neurology, University of Erlangen-Nuremberg, Erlangen, Germany; 2 International Brain Research Foundation, Edison, NJ, USA; 3 Department of Neurology, Medicine, and Psychiatry, New York University, New York, NY, USA Background: Reduced baroreflex sensitivity (BRS) is a marker of long-term prognosis in stroke (Robinson et al.; Stroke 2003;34:705–712). We hypothesize that BRS correlates with clinical stroke severity and disease development. Objective: To determine BRS changes upon admission and after 72 h of acute ischemic stroke and to assess BRS correlations with clinical severity. Methods: In 54 acute supratentorial ischemic stroke patients (30 men, 67 ± 13 years), we graded neurological deficits using the National Institute of Health Stroke Scale (NIHSS) within 24 h and after 72 h upon stroke onset. From spontaneous 5-min RR-intervals (RRI) and blood pressure (BP) recordings, we calculated spectral powers of mainly sympathetically mediated low- (LF: 0.04-0.15 Hz) and parasympathetically mediated high-frequency (HF: 0.15–0.5 Hz) RRI oscillations, sympathetic LF-powers of BP oscillations, and BRS as gain between RRI and systolic BP oscillations for coherence [0.7 using trigonometric regressive spectral analysis. We compared parameters obtained within 24 h and after 72 h using the paired t test.

Clin Auton Res (2010) 20:289–330 We correlated first and second measurement differences in NIHSS values and in BRS using the Spearman correlation coefficient (significance: p \ 0.05). Results: Seventy-two hours after stroke onset, patients had lower NIHSS scores (7.2 ± 5.5 vs. 5.8 ± 5.8, p \ 0.05) and systolic BPs (147.0 ± 24.3 vs. 133.2 ± 21.9 mmHg, p \ 0.05), but higher RRILF-powers (206.8 ± 249.6 vs. 537.0 ± 838.6 ms2, p \ 0.05), RRIHF-powers (96.1 ± 146.1 vs. 434.4 ± 891.7 ms2, p \ 0.05) and BRS (5.5 ± 3.3 vs. 9.3 ± 6.7 ms/mmHg, p \ 0.05) than within the first 24 h. RRIs and BP-LF-powers remained unchanged (p [ 0.05). BRSand NIHSS-differences between first and second measurements showed an inverse correlation (Spearman q: -0.386, p \ 0.05). Conclusions: Higher LF- and HF-powers after 72 h showed increased cardiac autonomic modulation which—together with higher BRS— reflects improved cardiac autonomic stability and prognosis. The inverse relation between higher BRS and lower NIHSS values, confirms BRS correlation with clinical neurological improvement.

Poster #47 Baroreflex regulates arterial pressure by modulating vascular properties, not by modulating ventricular properties K. Sunagawa Department of Cardiovascular Medicine, Kyushu University, Fukuoka, Japan Background: Baroreflex (BR) modulates both the ventricular and vascular properties. However, how changes in those mechanical properties quantitatively impact dynamic arterial pressure (AP) regulation remain unknown. We recently developed a framework of circulatory equilibrium (Am J Physiol 2004, 2005, the extended Guyton’s model) where we algebraically expressed both venous return and cardiac output as functions of mechanical subcomponents, i.e., left ventricular end-systolic elastance (Ees), heart rate (HR), systemic vascular resistance (R) and stressed blood volume (V). We investigated if the extended Guyton’s model quantitatively predicts the AP responses on the basis of BR induced dynamic changes of ventricular (Ees and HR) and vascular properties (R and V). Methods and Results: In 6 anesthetized dogs, we isolated carotid sinuses and randomly changed carotid sinus pressure (CSP) by a servo-pump, while measuring the beat-to-beat Ees (Millar and sonomicrometry), aortic flow (Transonic) and AP. We estimated transfer functions, over the wide frequency range, from CSP to HR, Ees, R and V using the initial half of the time series data in each dog. We then predicted dynamic changes in those parameters with the transfer functions in response to changes in CSP using the last haft of the time series data. Finally, we predicted dynamic changes in AP using the equilibrium framework. The predicted AP matched reasonably well with those measured (r2 = 0.81–0.95, p \ 0.001). Sensitivity analyses indicated that Ees and HR (ventricular properties) accounted for 17 ± 8% and \1%, respectively, whereas V and R (vascular properties) accounted for 34 ± 6 and 35 ± 9%, respectively, of BR induced AP regulation. Conclusion: The BR induced dynamic AP changes can be accurately predicted by the transfer functions from CSP to ventricular and vascular properties with the framework of circulatory equilibrium. Changes in the vascular properties, not the ventricular properties, predominantly determine the BR induced AP regulation.

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Poster #48 Angiotensin II-induced reactive oxygen species signaling in sympathetic ganglia S.W. Flanagan1, C.A. Whiteis1, F.M. Abboud1, M.W. Chapleau1,2 1 University of Iowa, Iowa City, IA, USA; 2 Veterans Affairs Medical Center, Iowa City, IA, USA Studies in our lab have demonstrated that angiotensin II (Ang-II) increases sympathetic nerve activity in part by direct activation of sympathetic ganglia (J Hypertens, 2001; Hypertension, 2004), and that reactive oxygen species (ROS) are increased in sympathetic ganglia of renin-angiotensinogen transgenic mice with hypertension and apolipoprotein E knockout mice with hypercholesterolemia (Auton Neurosci 2006). While Ang-II has been shown to generate ROS in many cell types, its effect on ROS production in sympathetic ganglia has not been studied previously. The goals of this study were to determine if Ang-II increases superoxide and/or hydrogen peroxide (H2O2) in neurons and/or glia dissociated from sympathetic ganglia, and identify cellular compartments of ROS generation. Cells were dissociated from superior cervical ganglia of male mice and exposed to Ang-II (200 nM) or vehicle for 10 min. Superoxide in cytosol and mitochondria, and H2O2 in cytosol were detected using three fluorescent redox-sensitive probes—dihydroethidium (DHE), MitoSOX Red, and dichlorofluorescein (CM-H2DCFDA), respectively. DHE fluorescence was increased by 53% (P \ 0.05) in neurons exposed to Ang-II (32,860 ± 4,665 units, n = 15) versus vehicle (21,490 ± 3,350 units, n = 21). The increase in DHE fluorescence was abolished by PEG-superoxide dismutase (n = 19), confirming that the fluorescence reflected superoxide. CM-H2DCFDA fluorescence was increased by 140% (P \ 0.05) in neurons exposed to Ang-II (n = 15) versus vehicle (n = 21). In contrast to DHE fluorescence, which was evident throughout cells, CM-H2DCFDA fluorescence was punctate and peri-nuclear, suggesting a different cellular location of H2O2 generation. Ang-II-induced increases in superoxide and H2O2 were also observed in glia. Ang-II did not increase MitoSOX Red fluorescence significantly (n = 10). We conclude that Ang-II increases superoxide and H2O2 in distinct cellular compartments in neurons and glia in sympathetic ganglia. Compartmentalization of ROS signaling and neuronal-glial interactions within sympathetic ganglia may regulate sympathetic activity with implications in pathological states associated with activation of the renin-angiotensin system.

Poster #49 Reduced SK channel function mediates enhanced excitability of pre-sympathetic PVN neurons and sympathoexcitation in heart failure L. Gui1, J.H. Zhu1, L.P. LaGrange2, Q.H. Chen3 1 Department of Cardiology, Affiliated Hospital of Nantong University Nantong, China; 2 Department of Pharmaceutical Sciences, University of the Incarnate Word, Feik School of Pharmacy, San Antonio, TX, USA; 3 Department of Exercise Science, Health and Physical Education, Michigan Tech University, Houghton, MI, USA A neural mechanism responsible for sympathoexcitation in heart failure (HF) rats was investigated. We hypothesized that down-

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322 regulation of small conductance Ca2+-activated K+ (SK) channel function in hypothalamic paraventricular nucleus (PVN) neurons projecting to spinal intermediolateral cell column (IML) could contribute to increased excitability and sympathetic outflow in HF rats. To test these possibilities, whole-cell recordings were made from IML-projecting PVN (PVN-IML) neurons in brain slices from rats with and without HF. Graded current injections induced graded increases in firing frequency in both groups, but responses to the maximally effective current of 200 pA were significantly greater in the HF group (42 ± 3 Hz, n = 5) compared to controls (22 ± 4 Hz, n = 5) (P \ 0.05). The SK channel blocker apamin (100 nM) significantly increased (p \ 0.05) discharge in neurons from sham rats (46 ± 4 Hz, n = 6), but had less effect on neurons from HF rats (45 ± 7 Hz, n = 5). The contribution of SK channel activity in regulating sympathetic activity was assessed by microinjecting apamin into the PVN of anesthetized rat. Apamin significantly (P \ 0.05) increased RSNA by 97 ± 11% in sham rats (n = 3), but was less increased in RSNA by 10 ± 3% in HF rats (n = 3). We conclude that increased excitability of PVN-IML neurons may contribute to sympathoexcitation of HF. Reduced SK channel function in these neurons may constitute an underlying neural mechanism.

Poster #50 Early autonomic dysfunction and cardiac failure in a mouse model of spinal muscular atrophy A.K. Bevan1,2, K.R. Hutchinson3,4, K.D. Foust1, L. Braun1, V.L. McGovern5, L. Schmelzer1, J.G. Ward6, J.C. Petruska7, P.A. Lucchesi3, A.H.M. Burghes2,5, B.K. Kaspar1,2,5 1 Department of Gene Therapy, The Research Institute at Nationwide Children’s Hospital, Columbus, OH, USA; 2 Integrated Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH, USA; 3 The Center for Cardiovascular and Pulmonary Research and The Heart Center, Nationwide Children’s Hospital, Columbus, OH, USA; 4 Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, New Orleans, LA, USA; 5 Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, OH, USA; 6 Specialty VETPATH, Seattle, WA, USA; 7 Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY, USA Purpose: Spinal muscular atrophy (SMA) is a debilitating neurological disease that is marked by isolated lower motor neuron death and the subsequent atrophy of skeletal muscle. This autosomal recessive disease is the number one genetic cause of infant death in the United States. While SMA pathology is classically thought to involve only the motor neurons and skeletal muscle, there are increasing numbers of reports regarding the coincidence of cardiac abnormalities in SMA patients. We therefore have sought to determine the extent of autonomic involvement in the development of heart failure in a mouse model of SMA and determine whether an AAV9-mediated gene-deliver approach is able to treat the deficit. Methods: The heart function of non-treated and scAAV9-SMN-treated D7SMN mice (SMN+/+, D7SMN+/+, Smn-/-) was compared to that

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Clin Auton Res (2010) 20:289–330 of their unaffected (SMN+/+, D7SMN+/+, Smn+/-) littermates at ages 7 and 14 days of age. Anatomical and physiological measurements were made by electrocardiogram (ECG) and echocardiographic visualization, including heart rate, ventricular dimensions, cardiac output, fractional shortening and Tei index. Results: At 14 days old, D7SMN mice have bradycardia and have significantly lower stroke volumes. They also show signs of decreased contractility and the development of a dilated cardiomyopathy (DCM). Signs of decreased heart function are also apparent in the 7-day-old animals, though to a lesser extent. scAAV9-treatment treats the likely cause of the heart dysfunction and prevent the formation of early DCM. The autonomic loci transduced by AAV9 include the motor nucleus of vagus, nucleus ambiguus, cardiac ganglia and sympathetic chain ganglia. Other sympathetic loci remain untransduced. Conclusions: SMA animals have significantly lower heart function, and this is likely due to dysregulation of the autonomic loci responsible for altering heart pacing. We have also demonstrated that AAV9 is a suitable vector for transducing key central and peripheral parasympathetic structures.

Poster #51 Blood flow dynamics in sciatic nerve supply artery detected by Doppler ultrasound J. Junuzovic1, M.L. Thorne1, J.C. Lacefield2,3, J.K. Shoemaker1,4 1 Department of Kinesiology, 2 Biomedical Engineering Graduate Program, 3 Robarts Research Institute, 4 Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada In this study, we report the first applications of Doppler ultrasound (45 MHz; Vevo 2100) to detect blood flow dynamics in the artery that supplies the sciatic nerve of anesthetised rats (250–300 gm). Arterial infusions of hexamethonium (HEX, ganglionic blocker) were given to alter sympathetic constriction and lower blood pressure and a saline bolus was given to transiently increase pressure with no change in neural vasomotor control. A catheter placed in the right iliac artery, such that the tip of the catheter is at the aortic bifurcation, delivered the agents through the left iliac artery and then into the left sciatic nerve supply artery. Preliminary data (n = 6) show that increases in supply artery blood flow velocity can be detected in response to a bolus infusion (under high pressure) of saline (baseline: 7.0 ± 0.7, bolus: 11.0 ± 2.1 mm/s; p = 0.08). During a 10 min steady saline injection at a lower pressure, velocity slightly decreased (baseline: 10.0 ± 1.9, injection: 8.0 ± 1.4 units, p \ 0.05) together with blood pressure so that the index of conductance (mean blood velocity/mean arterial pressure) was not changed (baseline: 0.12 ± 0.02, injection: 0.10 ± 0.02 mm/s/ mmHg). A systemic infusion of HEX decreased mean arterial pressure but did not change supply artery conductance (baseline: 0.12 ± 0.02, HEX: 0.14 ± 0.03 mm/s/mmHg). In contrast, the femoral artery conductance increased with HEX (baseline 0.59 ± 0.17, HEX: 1.50 ± 0.14 mm/s/mmHg; n = 3) suggesting that the sciatic nerve vasculature is not under the same magnitude of neural control as skeletal muscle vasculature. Overall, Doppler ultrasound was able to detect changes within the supply artery of the sciatic nerve and it appears that the sciatic nerve blood flow is, to a large extent, dependent on the arterial pressure. This research is supported by Canadian Institutes of Health Research.

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Poster Session III Poster #52 Postural tachycardia in children and adolescents—what is abnormal? W. Singer, D.M. Sletten, T.L. Opfer-Gehrking, P.A. Low Department of Neurology, Mayo Clinic, Rochester, MN, USA Background: Current definitions of Postural Tachycardia Syndrome (POTS) and orthostatic intolerance (OI) are based on a symptomatic excessive orthostatic increase in heart rate (HR). Based on adult normative data, a HR increment of greater than 30 bpm is commonly accepted for a diagnosis of a disorder of orthostatic tolerance. Our adult normative data suggest that the orthostatic HR increment is significantly influenced by age, and we have observed higher asymptomatic increases in HR in normal children and adolescents. We therefore raised the question whether it is appropriate to use the adult HR criteria for POTS and OI in a pediatric population, as seems to be common practice. Methods: 106 normal controls between the ages 8 and 19 years (14.5 ± 3.3 years) underwent standardized autonomic testing, including a 5 min 70° head-up tilt. The orthostatic HR increment and absolute orthostatic HR at 5 min were assessed and compared to 666 pediatric patients of similar age (15.5 ± 2.3 years), who were referred to our Clinical Autonomic Laboratory with symptoms of OI. Results: The HR increment at 5 min in control subjects was 27.0 ± 12.6 bpm, compared to a HR increment of 31.5 ± 14.4 bpm in patients referred for POTS/OI. Although the difference was highly significant, there was considerable overlap between the groups. 42% of normal controls had a HR increment of 30 bpm or more. The 90th percentile for the 5 min HR increment in normal controls was 44.0 bpm, the 95th percentile 51.3 bpm. Absolute orthostatic HR at 5 min in controls was 95.3 ± 16.3 versus 106.7 ± 18.0 bpm in patients. While there was still considerable overlap, the absolute orthostatic HR showed a greater and more consistent difference between groups. The 90th percentile for absolute HR at 5 min was 118.3, the 95th percentile 128.3 bpm. There was no influence of age on the HR increment in the age-group studied, but on absolute orthostatic HR. There was no influence of gender or BMI. Conclusions: The diagnostic criteria for OI/POTS in adults are inadequate for a pediatric/adolescent population. Considering pediatric normative data, a 30 bpm increase in HR is still well within normal range, and therefore has a low specificity as cutoff HR for a diagnosis of OI. A HR increase greater than 45 bpm would seem more appropriate to consider abnormal in children and adolescents. The findings raise many questions, including whether absolute orthostatic HR criteria need to be postulated and whether HR increment should be de-emphasized as diagnostic criterion for pediatric/adolescent OI and POTS.

Poster #53 Length of tilt table test in children: an unresolved problem S. Kassabian1, T.C. Chelimsky3, D. Zhang3, G. Chelimsky2,3 1 Department of Pediatrics, Metrohealth Medical Center, Case Western Reserve University School of Medicine; 2 Department of Pediatrics, Rainbow Babies and Children Hospital, Case Medical Center; 3 Department of Neurology and Autonomic Laboratory, University Hospitals Case Medical Center, Case Western Reserve University

323 Background: Standards for the optimal length of time to conduct a tilt table test in children does not exist. Each institution has different protocols making the interpretation of results difficult. Aim: Determine the needed length of tilt table test based on retrospective review of tilt table tests in our institution. Methods: An IRB-approved retrospective review of the autonomic laboratory database for all children ages 4 to 18 years old. Time at which a diagnosis was achieved was documented. Interval times were divided into 8 groups each with a 5-min interval. Tilt test provided 5 diagnoses: (1) POTS (increase in HR from supine to standing [30 bpm for 5 min within the first 10 min of the upright portion, without sustained drop in BP sustained with orthostatic symptoms; (2) orthostatic hypotension (OH) (sBP dropped [20 mmHg and/or dBP dropped by [10 mmHg in the first 3 min of the tilt); (3) Late POTS (symptoms of POTS arose after 10 min of the upright portion); (4) Late OH (finding of OH occurred after 3 min into the upright portion); Syncope (sudden drop in BP and HR). Results: 132/200 children included had abnormalities on tilt table. Mean age 14 years ± 2.6 years. 77% of diagnoses were made in first 10 min, 94% within first 20 min and 99% in the first 30 min. Conducting the test to 40 min did not identify any new diagnosis in children. Conclusion: The optimal time for tilt table in children is between 20 and 30 min. Tilt table tests performed for only 10 min will miss 23% of positive findings. Extending the test to 40 min does not add any benefit.

Poster #54 Co-morbidities in pediatric patients with postural tachycardia syndrome A. Ojha1, T.C. Chelimsky1, G. Chelimsky1,2 1 University Hospitals Case Medical Center, The Autonomic Laboratory, Neurologic Institute; 2 Rainbow Babies and Children’s Hospital, Division of Pediatric Gastroenterology Objective: There have been few investigations into the broad constellation of symptoms seen in pediatric patients with postural tachycardia syndrome (POTS). We investigated the frequency of various non orthostatic complaints in this population. Study design: We utilized our autonomic laboratory database to identify all pediatric patients with traditionally defined POTS that had filled out the Ohio Dysautonomia Survey (ODYSA). The responses of the patients to questions targeting various autonomic complaints such as syncope, gastrointestinal symptoms, sleep disturbances, headaches, urinary symptoms, chronic pain and Raynaud like symptoms were collected and analyzed. We compared the pediatric POTS co-morbidities to an adult cohort with POTS. Results: 53 pediatric patients filled out the questionnaire. There was a high frequency of sleep abnormalities (98%), chronic pain (85%), gastrointestinal abnormalities (79%), Raynauds like symptoms (74%), unexplained fatigue (61%), nausea and vomiting (60%) observed in the subjects with lower rates of headaches (45%), syncope (32%) and urinary complaints. POTS in our adult sample was also highly associated with sleep abnormalities and headaches. Symptoms of nausea/ vomiting were found to be significantly less in the adult sample and there was reduced occurrence of Raynaud like symptoms and chronic pain although the difference between the two groups was not statistically significant. Conclusions: Our results demonstrate the occurrence of various non orthostatic symptoms in pediatric POTS patients. These findings

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324 suggest the need for an interdisciplinary approach to the treatment and management of POTS as well as further investigation into the mechanisms that lead to the concurrent presentation of both orthostatic and non orthostatic symptoms in these patients.

Poster #55 Orthostatic tolerance and autonomic symptoms in a prospective cohort of adolescents with chronic fatigue syndrome and recovered controls following infectious mononucleosis B.Z. Katz, J.M. Stewart, Y. Shiraishi, C.J. Mears, R. Taylor Department of Pediatrics and Physiology, New York Medical College, Hawthorne, NY, USA Chronic fatigue syndrome (CFS) is a complex condition responsible for marked functional impairment. Orthostatic intolerance (OI) is frequently reported in the young. We recently reported a prospective study of acute infectious mononucleosis (IM) showing 13% of adolescents met criteria for CFS after 6 months. We studied 36/39 adolescents with CFS and 45/50 asymptomatic controls 6 months after IM to determine standing orthostatic tolerance and correlative symptoms of autonomic dysfunction. All subjects completed a modified Mayo Clinic Autonomic Symptom Profile (ASP) 0 and 6 months and had orthostatic tolerance testing (SOTT) comprising a 10 min supine rest followed by 10 min of quiet standing as tolerated. BP, HR and symptoms of OI were collected each minute. Criteria for abnormally decreased BP or HR, or increased HR were defined a priori. Chi square analysis and Spearman correlations were used to correlate the results of SOTT and modified ASP with the diagnosis of CFS. Evaluations were blinded to subject grouping. CFS and recovered controls did not differ significantly in age, weight or BMI. Orthostatic intolerance correlated with the diagnosis of CFS at 6 months (P \ 0.05). 14/36 CFS patients had abnormal SOTT compared with 9/45 controls. The ASP score at baseline and at 6 months following IM was significantly increased (P \ 0.001) in those with CFS. Adolescents who meet the criteria for CFS 6 months following IM appear to have, as a group, a greater likelihood of standing orthostatic intolerance and increased symptoms of autonomic disability than recovered controls. Whether these abnormal findings are cause or effect of CFS or whether they can be used to determine which adolescents following IM will develop CFS remains to be determined. However, this study uniquely and prospectively demonstrates that IM produces both fatigue and associated symptoms of autonomic dysfunction and orthostatic intolerance in a subset of young patients.

Poster #56 Functional gastrointestinal disorders (FGID): not just a GI problem G. Chelimsky1,2, D. Zhang2, S. Safder3, T. Chelimsky2 1 Rainbow Babies and Children’s Hospital, Case Medical Center, Cleveland, OH, USA; 2 Department of Neurology, Case Medical Center, Cleveland, OH, USA; 3 Arnold Palmer Hospital for Children, Orlando, FL, USA

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Clin Auton Res (2010) 20:289–330 Background: Many children with FGID suffer from complaints in other systems. There is no data about the non-psychiatric co-morbidities of FGID in children. Aim: Assess the co-morbidities of FGID in children in a questionnaire based study. Methods: Prospective IRB approved study. We enrolled children with FGID who met ROME II criteria. The children or parents filled an extensive questionnaire to evaluate for non-GI complaints. Results: 40 children were enrolled in the study (IBS: 19; Functional dyspepsia: 13; abdominal migraine: 4; Cyclic vomiting syndrome: 4). Orthostatic symptoms were very common, with 87% reporting orthostatic symptoms (dizziness, feeling sweaty, nauseated, etc). 20% reported having fainted[3 times in their lifetime. 52% reported more than 50 headaches in their life, with 37% having headaches lasting [4 h. Most of the headaches were described as throbbing and/or unilateral, with photo or phonophobia (85%) and associated with nausea/vomiting (65%). Chronic pains [3 month duration in the back, neck and extremities were quite common (48%). Many children reported lack of energy (64%) and not feeling refreshed after sleep (52%). Other sleep complaints like difficulty falling asleep, waking up earlier than needed and having trouble staying awake during the day time were common (about 60%). Raynaud-like syndrome was reported in 31% (fingers turning white, blue or red with cold). Urinary symptoms were not common. Conclusion: Children with FGID have many other associated symptoms that may contribute to poor quality of life. These symptoms may be exacerbate one another, for example poor quality of sleep worsening migraine or pain perception, and strongly suggest an interdisciplinary approach in the treatment of these disorders.

Poster #57 Headache following reflex syncope in adolescents may be due to deregulated cerebral blood flow A.J. Ocon1, D. Clark2, M.S. Medow1,2, J.M. Stewart1,2,3 1 Departments of Physiology, 2 Pediatrics, 3 Medicine, New York Medical College, Valhalla, NY, USA Reflex syncope commonly occurs in the adolescent population following orthostatic stress. Hypotension, bradycardia, and cerebral hypoperfusion occur prior to fainting. Cerebral blood flow (CBF) deregulation is associated with central hypoperfusion and faint. Following syncopal episodes, individuals often complain of a headache. We hypothesize that the post-syncopal headache is due to a faint-induced deregulation of cerebral blood flow. We tested 16 subjects, with a history of fainting and associated headaches, and 15 healthy non-fainting control volunteers during 70° tilt table testing while measuring mean arterial pressure (MAP), heart rate (HR), respiration, end-tidal CO2 (ETCO2), and CBF velocity (CBFV). Fainters were tilted until the time of faint and control subjects were tilted for 10 min, with the last 30 s being compared to values obtained from fainters immediately prior to faint. Upon fainting, fainters’ MAP decreased 49 versus 6% in controls (P \ 0.001) and HR decreased 15 versus a 35% increase in controls (P \ 0.001). In fainters, mean, systolic, and diastolic CBFV decreased 46, 11, and 66%, respectively, versus in controls 13% (P \ 0.001), 10% (P = NS), and 9% (P \ 0.001), respectively. Pulse CBFV (systolic– diastolic CBFV) increased in fainters by 38 vs. a 9% decrease in controls (P \ 0.002). ETCO2 decreased 23% in fainters versus 8%

Clin Auton Res (2010) 20:289–330 in controls (P \ 0.001). Returning to supine, fainters’ mean CBFV decreased 11 vs. 3% in controls (P \ 0.02); systolic CBFV increased 11 versus a 0.5% decrease in controls (P \ 0.01); diastolic CBFV decreased 19 versus 6% in controls (P \ 0.01); pulse CBFV increased 21 versus 3% in controls (P \ 0.02). Deregulation of the cerebral vasculature following fainting may predispose individuals to headache. Following faint, cerebral pressures at or near the critical closing pressure along with hypocapnia may lead to diastolic vascular collapse while hyperemic increases in flow during systole may be associated with systolic vasodilation, together leading to vascular diameter instability, increased pulse CBFV, and headache.

Poster #58 Familial dysautonomia: alterations in cardiopulmonary regulation during wakefulness and sleep M.S. Carroll1, A.S. Kenny1, J.M. Ramirez2, D.E. Weese-Mayer1 1 Department of Pediatrics (Center for Autonomic Medicine, Children’s Memorial Hospital, Northwestern University Feinberg School of Medicine; 2 Seattle Children’s Research Institute, University of Washington Rationale: Children with Familial Dysautonomia (FD), a hereditary sensory and autonomic neuropathy caused by an IKBKAP mutation, experience autonomic dysregulation, repeated autonomic crises and a high incidence of sudden unexplained death. We hypothesize that quantitative analysis of in-home physiological recordings would indicate pervasive cardiorespiratory dysregulation. Methods: Respiratory inductance plethysmography (chest/abdomen), ECG, hemoglobin saturation, and pulse waveform were recorded in-home during daytime wakefulness (n = 25) and nighttime sleep (n = 22) in children with mutation-confirmed FD and 25 age-, gender- and ethnicity-matched controls. Cardiorespiratory metrics (r-wave interval: RR-I; respiratory intervals; inspiratory duration; and heart rate variability, HRV, as standard deviation of normal ventricular r-wave intervals: SDNN) were calculated and analyzed. Results: Compared to data from controls, respiratory parameters were significantly altered in FD subjects. Respiratory intervals were shorter in waking FD subjects than in controls (2.82 ± 0.46 vs. 3.24 ± 0.44 s; p \ 0.001), reflecting a reduction in inspiratory durations (1.02 ± 0.14 vs. 1.33 ± 0.15 s; p \ 0.001). Ventilation was similarly altered during nighttime sessions, with reduced respiratory intervals (3.32 ± 0.44 vs. 3.69 ± 0.48 s; p \ 0.01) and inspiratory durations in FD (1.21 ± 0.15 vs. 1.57 ± 0.26 s; p \ 0.0001). Significant differences were also found for waking RR-I (0.64 ± 0.12 vs. 0.73 ± 0.12 s; p \ 0.01), waking HRV (SDNN: 77 ± 32 vs. 102 ± 38 ms. p \ 0.01) and nighttime HR (0.72 ± 0.10 vs. 0.85 ± 0.15 s; p \ 0.001). Conclusion: These results indicate that children with FD have more rapid respiration with shorter inspiratory durations during both waking and presumptive sleep epochs. Daytime recordings revealed differences in heart rate and heart rate variability while only heart rate was significantly altered in nighttime sessions. Taken together, these data begin to quantify the cardiorespiratory dysregulation experienced by children with FD during wakefulness and sleep. Extramural Support: Dysautonomia Foundation, Inc. provided grant support (DEW-M).

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Poster #59 Congenital central hypoventilation syndrome (CCHS): PHOX2B genotype/CCHS pupillary function phenotype P.P. Patwari, J. Chesniak, N.L. Kuntz, A.S. Kenny, D.E. Weese-Mayer Department of Pediatrics, Children’s Memorial Hospital, Northwestern University Feinberg School of Medicine, IL, USA Background: PHOX2B, the disease-defining gene for Congenital Central Hypoventilation Syndrome (CCHS), encodes a highly conserved transcription factor with an early embryologic role in panneuronal differentiation in the autonomic nervous system (ANS), and expression in multiple cranial nerve nuclei. CCHS-causing PHOX2B mutations are due to heterozygous polyalanine repeat expansion mutations (PARMs; genotypes indicate alanine number: 20/24–20/33 in CCHS; 20/20 is normal); or to non-PARMS (missense, nonsense, frameshift). We previously demonstrated an increased frequency of pupillary abnormalities in CCHS, and a genotype/phenotype relationship for other CCHS-phenotype features. Recognizing the PHOX2B gene regulatory role in the ANS and expression in nuclei regulating pupillary function, we hypothesized that the presence and severity of pupillary abnormalities in CCHS would correlate with PHOX2B genotype. Methods: A validated ANS questionnaire (ANS-Q) was administered to 96 PHOX2B mutation-confirmed CCHS subjects, with focus on pupillary reactivity. Pupillometry was performed in a subset of these subjects (0.3–19 years), with monocular measurements obtained in a darkened quiet room (NeurOptics PLR-2000): maximum/minimum pupil size, % constriction, and average velocity of constriction (ACV) and dilation (ADV). Results: Frequency (by ANS-Q) and severity (by pupillometry) of pupil abnormalities correlated with PHOX2B genotype. By ANS-Q, pupil abnormalities were reported in 15% (20/25), 45% (20/26), 58% (20/27), and 90% (20/28–20/33) of CCHS subjects. 55 separate pupillometry measurements demonstrated an inverse relationship between the most common genotypes 20/25, 20/26, and 20/27 and % pupillary constriction (27, 19, 5%, respectively), ACV (3.5, 1.8. 0.19, respectively), and ADV (1.0, 0.5, 0.2, respectively). Values are shown for the right eye, though no difference right versus left eye was noted in these measures. No correlation with age was identified. Conclusion: These results confirm our hypothesis that pupillary dysfunction in CCHS varies by PHOX2B genotype. Shorter PARMs may be associated with mild deficits that would go unrecognized without objective measures by pupillometry.

Poster #60 Longitudinal changes to neurophysiologic function in diabetes C. Gibbons1, R. Freeman1, A. Veves2 1 Department of Neurology and 2 Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA Background: Neuropathy is a debilitating complication of diabetes with a number of recent clinical trial failures, possibly due to primary endpoint selection. Neurophysiologic assessments include nerve conduction studies, autonomic testing, cutaneous blood flowmetry

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326 and quantitative sensory testing. There are few data defining temporal changes in neurophysiologic function in subjects with diabetes. Objective: To quantify the differences in neurophysiologic function over 18 months in subjects with diabetes. Methods: Sixty-five subjects with diabetes had detailed physical examinations, anthropomorphic measurements, autonomic testing (tilt table test, Valsalva maneuver, paced breathing), quantitative sensory testing [(QST) with thermal detection, thermal pain detection and vibration detection in hands and feet], nerve conduction studies [(NCS) of the sural and peroneal nerves] and laser-Doppler blood flowmetry [of the foot and arm] monitored at baseline and 18 months. Results: There were no changes to quantified physical examination scores, A1c values, lipid profiles or NCS during the 18 months. Among autonomic tests, decreases in the blood pressure response during phase 2 and phase 4 of the Valsalva maneuver were noted (P \ 0.05 vs. baseline). Among QST: cold, cold-pain, heat, and heatpain detection at the hands and feet worsened (P \ 0.05). LaserDoppler flowmetry declined in both the endothelial dependent and axon reflex mediate regions in the foot (P \ 0.05). Conclusions: Tests of autonomic and small nerve fiber function worsened over 18 months in subjects with well controlled diabetes. Tests of large fiber function showed no change over 18 months. Clinical trials of agents seeking to alter the natural history of diabetic neuropathy may require primary endpoints that focus on autonomic and small nerve fiber function in order to demonstrate meaningful improvements.

Poster #61 Heart rate and systolic blood pressure variability in patients with diabetic autonomic neuropathy R.C. Callejas1, B. Estan˜ol2 1 Hospital Universitario de Puebla, Benemerita Universidad Autonoma de Puebla, Puebla, Mexico; 2 Departamento de Neurologı´a y Psiquiatrı´a, Laboratorio de Neurofisiologı´a Clı´nica. Instituto Nacional de Ciencias Me´dicas y Nutricio´n Salvador Zubira´n, Mexico City, Mexico Introduction: Somatic diabetic neuropathy is a common finding among type 1 and 2 diabetic patients (DP). However, cardiac autonomic neuropathy and the resultant reduction in heart rate variability (HRV) are subclinical. Spectral power of HRV has three main frequency bands: very low frequency (VLF) band, low frequency (LF) band 0.04–0.15 Hz, and high frequency (HF) band 0.15–0.4 Hz. Objective: Asses, in time and frequency domain, the beat-to-beat heart rate (HR) and systolic blood pressure (SBP) variability in DP with autonomic neuropathy and healthy volunteers (HV) in three studying conditions: (1) supine position, (2) upright position (UP) and (3) rhythmic breathing (RB) at 6 cycles per minute. Methods: 15 DP and 31 HV, aged from 20 to 50 years were studied. For each studying condition, a single 5 min record was obtained. SBP and HR were noninvasive recorded on a beat-to-beat basis using a Finapres device. Frequency domain analysis was performed using a Fast Fourier transform analysis obtaining LF band, HF band and simpatho/vagal balance (SVB: LF/HF). Results: Mean of HR was significantly higher in DP than in HV in all studying conditions. SD of HR was decreased in DP in all studying conditions. Mean and SD of SBP were significantly higher in DP than in HV in UP. LF band and SVB were decreased in DP in UP and RB. Both LF band and SVB of the SBP were decreased in DP in all studying conditions, whereas HF band was increased.

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Clin Auton Res (2010) 20:289–330 Conclusions: DP with autonomic neuropathy have a decrease in HR and SBP variability. The decreased SVB, HF and LF band of the HR in both UP and RB highlights cardiovagal and cardiosympathetic impairment in DP. Sympathetic blood vessel innervation impairment is also shown by the decrement of both LF band and SVB in the SBP variability.

Poster #62 A unique deficit in pupillary function in autoimmune autonomic ganglionopathy S. Vernino Department of Neurology, UT Southwestern Medical Center, Dallas, TX, USA Autoimmune autonomic ganglionopathy (AAG) is an antibodymediated disorder of synaptic transmission in autonomic ganglia. This disorder presents as panautonomic failure affecting sympathetic, parasympathetic and enteric function. Patients with AAG may improve substantially with immunomodulatory treatment. The presence of serum antibodies specific for ganglionic acetylcholine receptors (AChR) serves to definitively confirm the diagnosis, however, some patients with a similar clinical presentation may be seronegative. Standard quantitative tests in the autonomic function laboratory typically show severe autonomic deficits but do not differentiate AAG from other forms of autonomic failure. AAG patients with ganglionic AChR antibodies often have impaired pupillary light reflex. We examined three patients with seropositive AAG using quantitative infrared video pupillometry. The pupillary constriction response in AAG had slowed constriction velocity and reduced constriction amplitude. In addition, the AAG pupil showed a unique pattern of pupillary fatigue. With prolonged light stimulus, the initial pupillary constriction was not sustained, and the pupil redilated despite continued light presentation. This premature redilation was not seen in any other subject tested including over 100 healthy controls and over 200 patients with various neurological disorders, including those with deficits in pupillary light reflex (diabetic autonomic neuropathy, congenital dysautonomia, Ross syndrome, optic neuropathy, seronegative AAG) and myasthenia gravis. Premature pupil redilation, or pupillary constriction fatigue, is consistent with the underlying pathophysiology of AAG. This pupillary deficit appears to be a unique diagnostic finding in AAG.

Poster #63 A case of autonomic autoimmune ganglionopathy: profound improvement with maintenance rituximab B.K. Black1,4, R.D. Hollenbeck1, A.C. Peltier2,4, I. Biaggioni1,3,4, D. Robertson1,2,3,4, E.F. Winton5, S.R. Raj1,3,4 1 Departments of Medicine, 2 Neurology, 3 Pharmacology, and 4 Paden Autonomic Dysfunction Center, Vanderbilt University School of Medicine and 5 Division of Hematology and Oncology, Emory University School of Medicine

Clin Auton Res (2010) 20:289–330 We report a case of autoimmune autonomic ganglionopathy (AAG) in a 65-year-old female who was successfully treated with plasma exchange (PLEX) and maintenance rituximab. This patient was diagnosed with low-grade B cell (CD20+) lymphoma in January 2004, which was managed conservatively. In July 2004, she developed progressive lightheadedness, recurrent syncope, constipation, anhidrosis and xerostomia. Despite treatment with fludrocortisone and midodrine, she became wheelchair bound and ceased to live independently. When first seen in the Autonomic Clinic (December 2005), she had severe orthostatic hypotension (BP drop from 151/77 mmHg supine to 56/29 mmHg standing 1 min) with no change in heart rate (66–67 bpm). Autonomic reflexes were severely impaired, plasma norepinephrine levels were very low both supine and upright, and she had absent QSART sweat response in leg sites. Her autonomic ganglionic acetylcholine receptor (nAChR) antibody titer was high (2.63 nmol/L). She was diagnosed with AAG. Her lymphoma was restaged, and she was treated with a 4-week cycle of rituximab (March 2006). Although she transiently had significant improvement of her symptoms, they deteriorated again (March 2007). She then completed a 5 day course of PLEX with subjective improvement of her symptoms, resolution of her xerostomia and she could again walk [10 min. However, her nAChR titers went back up and her autonomic failure symptoms returned. She underwent another 4 weeks course of rituximab with clinical improvement and decreased antibody titers. The patient insisted on maintenance rituximab therapy q2 months. Serial nAChR antibodies decreased and stayed low, eventually reaching undetectable levels. Clinically, she showed great improvement and eventually gave away her wheelchair and resumed independent living. Summary: this case illustrates both a good correlation between nAChR titers and some finding of autonomic failure in this patient. Further, unlike a prior report, a single course of rituximab was not adequate, and she required maintenance rituximab treatments.

Poster #64 Autonomic dysfunction in chronic inflammatory demyelinating polyradiculoneuropathy J.J. Figueroa1,2, P.J. Dyck1,2, P. Sandroni1,2, R.S. Laughlin1, J.A. Mercado1,2, R. Massie1,3, P.A. Low1,2 1 Department of Neurology, 2 Autonomic Reflex Laboratory and 3 Peripheral Nerve Laboratory, Mayo Clinic, Rochester, MN, USA Quantification of frequency, severity and distribution of autonomic deficits in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is lacking. The Composite Autonomic Severity Scale (CASS) is a validated instrument for laboratory quantification of severity and distribution of autonomic failure that corrects for the confounding effects of age and gender. We reviewed 47 patients who (1) met strict clinical and electrophysiologic criteria for CIDP after a full neurologic evaluation at Mayo Clinic between 1992 and 2009; and (2) had an autonomic reflex screen (ARS) done as part of their workup. Thermoregulatory sweat test (TST) was reviewed when available. A total CASS score [0 = no deficit; 10 = maximum deficit] with sudomotor [0–3], cardiovagal [0–3] and adrenergic [0-4] subscores were derived from the ARS ± TST. Of 47 idiopathic CIDP patients, 55% were male. The mean age at symptom onset was 41.4 ± 15.2 years. The majority were motor predominant, of insidious onset and progressive course. At

327 autonomic testing the mean disease duration was 3.5 ± 4.3 years and the mean neuropathy impairment score was 46.5 ± 32.7, indicating on average moderate severity. CASS abnormalities occurred in 47% of patients. Sudomotor and cardiovagal dysfunction comprised most of the abnormalities. Total, sudomotor, cardiovagal and adrenergic CASS scores were 0.9 ± 0.8, 0.5 ± 0.7, 0.2 ± 0.4, 0.1 ± 0.3, respectively. No patient had CASS = 4. Of 8 patients with TST, 5 showed abnormalities with anhidrosis ranging from 2 to 59% (mean 12.8 ± 21%) of anterior body surface in distal (n = 2), regional (n = 1), mixed (n = 1) and diffuse (n = 1) patterns. In summary, laboratory evidence of autonomic impairment in idiopathic CIDP is frequent but mild and limited in distribution (minimal cholinergic involvement with adrenergic sparing). A CASS = 4, indicating moderate to severe dysfunction, is not found in idiopathic CIDP and should raise consideration for an alternative diagnosis.

Poster #65 Prospective 5-year natural history study of probable multiple system atrophy (MSA) in 175 North American subjects S. Gilman1, P.A. Low2, S. May3, C. Tanner4, M. Stern5, P. Sandroni2, S. Reich6, F. Marshall7, P. Novak8, J. Jankovic9, G. F. Wooten10, B. Racette11, D. Sletten2, C. Shults3 1 University of Michigan, Ann Arbor, MI, USA; 2 Mayo Clinic, Rochester, MN, USA; 3 University of California, San Diego, CA, USA; 4 Parkinson’s Institute, Sunnyvale, CA, USA; 5 University of Pennsylvania, Philadelphia, PA, USA; 6 University of Maryland, Baltimore, MD, USA; 7 University of Rochester, Rochester, NY, USA; 8 Boston University, Boston, MA, USA; 9 Baylor College of Medicine, Houston, TX, USA; 10 University of Virginia, Charlottesville, VA, USA; 11 Washington University, St. Louis, MO, USA Objective: To examine disease progression and survival in 175 patients with probable MSA studied prospectively to determine (a) life expectancy as a prelude to designing pharmacologic interventions and (b) whether there is a difference in course between subjects who, at entry, show cerebellar ataxia and autonomic failure without parkinsonian features (MSA-C) as compared to those with parkinsonian features and autonomic failure without cerebellar ataxia (MSA-P) and subjects with mixtures of parkinsonian and cerebellar features plus autonomic failure (MSA-PC). Background: Previous studies of the natural history of MSA have been retrospective. This prospective study of the disorder was designed to examine natural history in subjects who entered the study with the diagnosis of probable MSA. Methods: We examined at 6-month intervals 175 patients with the diagnosis of probable MSA based upon the Second Consensus Criteria. On entry, the subjects were divided into three groups, MSA-C, MSA-P, and MSA-PC. Longitudinal follow-up included evaluations with UMSARS I, II, III, IV, COMPASS, and SF-36. Patients were followed for an average of 2.6 years. We analyzed data using Kaplan–Meier Survival Analysis. Results: The study group consisted of 105 (60%) males and 70 (40%) females, mean age at entry 63.4 8.6 yrs. We enrolled 20 patients with MSA-C, 72 with MSA-P, and 83 with MSA-PC. After 6 years, 101

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328 subjects had expired, of whom 39 received autopsy examination with verification of diagnosis in 32 cases (6 pending, 1 MSA not confirmed). Half of the patients who died had lived less than 2 years after enrollment, and by 3 years after enrollment only 53 patients (30%) remained able to participate in the study. Kaplan–Meier survival analysis revealed no differences between groups and we found no differences between groups in progression on any of the UMSARS scales. Conclusions: This study revealed a high mortality rate and a relatively short average survival time after enrollment. There was no difference in course or longevity based upon MSA type at enrollment. These data support enrollment of subjects at earlier stages to allow longer survival in pharmacologic intervention studies.

Poster #66 Autopsy confirmed multiple system atrophy (MSA) cases: Mayo experience and role of autonomic function tests V. Iodice1, A. Lipp2, J.E. Ahlskog3, P. Sandroni3, R.D. Fealey3, J.E. Parisi3, J.Y. Matsumoto3, K.K. Nickander3, D.M. Maraganore4, E.E. Benarroch3, K. Kimpinski5, W. Singer3, T.L. Gehrking3, J.A. Gehrking3, D.M. Sletten3, A.M. Schmeichel3, J.H. Bower, S. Gilman6, J. Figueroa3, P.A. Low3 1 Imperial College London, London, UK; 2 Charite´ - University Medicine Berlin, Germany; 3 Mayo Clinic, Rochester, MN, USA; 4 NorthShoreUniversity HealthSystem, Evanston, IL, USA; 5 London Health Sciences Centre, London, Ontario, Canada; 6 University of Michigan, Ann Arbor, MI, USA Objective: To evaluate the Mayo experience with particular focus on clinical features and autonomic function tests in autopsy-confirmed MSA cases seen at Mayo Clinic, Rochester, Minnesota. Background: The relentless progression of parkinsonism, cerebellar signs, and autonomic failure suggests the diagnosis of MSA. The Mayo experience has indicated that the severity and distribution of autonomic deficits may be helpful in the diagnosis of MSA. Methods: We analyzed our experience with 29 autopsy confirmed cases of MSA evaluated at Mayo Clinic who had undergone formalized autonomic testing. Patients underwent evaluation of adrenergic, sudomotor, and cardiovagal function and thermoregulatory sweat test (TST) from which we derived the composite autonomic severity score (CASS). We also measured plasma catecholamines. Results: Patient characteristics: M, 17; F, 12; age of onset, 57 ± 8.1 years; disease duration to death, 6.3 ± 3.1 years; first symptom: autonomic, 18; parkinsonism, 7; cerebellar 2. Clinical phenotype at onset was MSA-P, 19; MSA-C, 8; pure autonomic failure (PAF), 2. Clinical diagnosis at last visit was MSA for 28 cases. One case was diagnosed as PAF at his last (and only) Mayo visit. Autonomic manifestations included: orthostatic hypotension, 72%; neurogenic bladder, 89%; and severe constipation, and 77%. Sleep disturbances included REM sleep behavior disorder (54%); sleep apnea (38%); and nocturnal stridor (30%). Autonomic failure was severe: CASS was 7.2 ± 2.3 (maximum = 10). TST% was 65.6 ± 33.9% and exceeded 40% in 68%. The most common pattern was global anhidrosis. Other patterns suggesting of MSA were mixed, segmental, or regional anhidrosis. 2/22 patients had normal patterns. Norepinephrine (NE) was normal supine (203.6 ± 112.7) but orthostatic increment of 33.5 ± 23.2% was reduced. Abnormalities evolved with duration of disease.

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Poster #67 Norepinephrine transporter blockade, as diagnostic tool for early multiple system atrophy: case report C. Shibao1, L.E. Bradbury2, I. Biaggioni1 1 Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN, USA; 2 Department of Neurology, Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN, USA We present a case of a 71-year-old woman presenting with 2-year history of disabling orthostatic hypotension; her systolic blood pressure drops approximately 70 mmHg with minimal increase in her heart rate. Autonomic function testing revealed severe autonomic failure. She has a blunted sinus arrhythmia ratio 1.04 (normal [1.2). Her Valsava maneuver was abnormal, the fall in systolic blood pressure (SBP) during phase II was exaggerated (-78 mmHg, normal\20), and the expected increase during phase IV was absent (-42 mmHg, normal [20). Her blood pressure dropped with hyperventilation (-30 mmHg, normal \10 mmHg), and she did not increase her blood pressure with cold pressor and handgrip tests. Plasma catecholamines (norepinephrine and epinephrine) were 226 pg/dl and 18 mg/dl while supine and 221 pg/dl and 35 mg/dl while standing (abnormal low), respectively. This initial clinical presentation was consistent with pure autonomic failure. The patient, however, had a positive pressor response to atomoxetine, a norepinephrine transporter blocker, which suggests intact peripheral noradrenergic fibers as found in multiple system atrophy (MSA). During 3 years of follow up, she developed rapidly progressive parkinsonism unresponsive to carbidopa/levodopa 25/100 mg and amantadine. The Unified Multiple System Atrophy part II score was 24/56 in the motor examination scale portion with the largest deficits in her posture, balance, and severe inability to walk without assistance. I-123-metaiodobenzylguanidine–single photon emission computed tomography (MIBG–SPECT) indicated preserved cardiac MIBG uptake indicating integrity of post-ganglionic cardiac sympathetic neurons, consistent with multiple system atrophy. We argue that the pressor effect of atomoxetine might be a useful tool in the early detection of MSA. Early diagnosis of MSA has important prognostic implications and is essential for the development of treatment strategies aimed at neuroprotection.

Poster #68 Severe generalized autonomic failure in Parkinson disease P. Novak, L. Qin, P. Ravin Department of Neurology, University of Massachusetts, Worcester, MA, USA Background: Generalized autonomic failure (GAF) that is commonly seen in Parkinson disease (PD) can be responsible for significant morbidity. Severity and distribution of GAF in PD patients with prominent symptoms of dysautonomia remains unclear. Methods: This is a retrospective, single center study. 35 PD patients with complains in multiple autonomic domains were subjected to standardized autonomic testing that included deep breathing, Valsalva maneuver, head-up tilt and quantitative sudomotor testing at 4 sites. Severity of parkinsonism was evaluated by the UPDRS scores. The severity and distribution of dysautonomia was quantitated using Composite Autonomic Severity Score (CASS) in adrenergic, cholinergic and sudomotor domains.

Clin Auton Res (2010) 20:289–330 Results: UPDRS-T (total) = 48.9 ± 22.5, UPDRS-M (motor) = 28.2 ± 13.1. CASS scores were: 5.4 ± 2.0 total, 1.6 ± 1.1 cardiovagal, 2.0 ± 1.1 adrenergic and 1.8 ± 0.9 sudomotor. Severe GAF was detected in 12 patients (34.3%), moderate GAF in 16 patients (45.7%) and mild GAF in 7 patients (20%). Patients with severe GAF (total CASS score = 7.66 ± 0.8) had subscores: 2.4 ± 0.7 cardiovagal, 3.0 ± 0.9 adrenergic and 2.25 ± 0.9 sudomotor. There was significant correlation (p \ 0.05) between total and adrenergic CASS scores and both total and motor portion of UPDRS. Conclusions: Severe GAF is associated with PD. GAF affects all three main autonomic domains; the adrenergic domain being the most affected. The severity of dysautonomia correlates with severity of parkinsonism. Proper recognition of GAF in PD can lead to more optimal treatment of PD symptoms.

Poster #69 When in the course of Parkinson disease does cardiac sympathetic denervation occur? D.S. Goldstein Clinical Neurocardiology Section, CNP/DIR/NINDS/NIH, Bethesda, MD, USA Background: Cardiac sympathetic denervation characterizes most patients with Parkinson disease (PD) and all with PD and orthostatic hypotension (OH). The pathogenetic process has been proposed to occur early in autonomic nerves, with subsequent ascending pathology in the medulla and pons before involvement of the midbrain substantia nigra. These findings raise the possibility that cardiac sympathetic denervation might provide a biomarker of pre-symptomatic PD. Methods: Cases were reviewed of patients with clinically unequivocal PD who had serial cardiac 6-[18F]fluorodopamine scanning over up to 12 years. Results: One patient had documented cardiac sympathetic denervation 4 years before onset of motor signs of PD. A second patient had partial denervation confined to the left ventricular free wall and then rapid progression to diffuse absence of left ventricular myocardial 6[18F]fluorodopamine-derived radioactivity by 2 years later. A third did not develop neuroimaging evidence of cardiac sympathetic denervation until 8 years of follow-up, with progression to near-total denervation over the next 2 years. All patients with PD + OH had diffuse cardiac sympathetic denervation upon initial testing, regardless of the duration of the movement disorder. Across 30 PD patients who had both brain 6-[18F]fluorodopa and cardiac 6-[18F]fluorodopamine PET scanning, there was no relationship between the putamen:occipital cortex ratio of 6-[18F]fluorodopa-derived radioactivity and interventricular septal myocardial 6-[18F]fluorodopaminederived radioactivity. Interpretation: Early loss of cardiac sympathetic neurons is not an invariable finding in PD. Across PD patients cardiac sympathetic denervation occurs independently of nigrostriatal dopaminergic denervation.

Poster #70 Cooling of skin of the back: a novel autonomic function test D.S. Goldstein, L. Sewell, D.J. Gross, P. Sullivan, C. Holmes, R. Imrich, Y. Sharabi Clinical Neurocardiology Section, CNP, DIR, NINDS, NIH, Bethesda, MD, USA

329 Background: Most tests of sympathetic noradrenergic function depend on reflexive responses to decreased cardiac venous return. Cold exposure increases blood pressure, cutaneous vascular resistance, and sympathetic noradrenergic outflows, but patients may not tolerate the testing. Heat exposure evokes mainly sympathetic cholinergic rather than noradrenergic responses. We explored whether a mild, well tolerated, localized stimulus—26–28°C temperature at skin of the back—is sufficient for informative autonomic function testing. Methods: In 15 controls and 15 patients with neurogenic orthostatic hypotension and baroreflex failure (3 pure autonomic failure, 7 multiple system atrophy, 1 autoimmune autonomic ganglionopathy, 5 Parkinson disease), responses of finger skin temperature and microcirculatory flow, forearm and systemic hemodynamics, and plasma norepinephrine (NE) levels were measured during exposure of skin of the back to 38 and then 26–28°C for about 20 min each using water circulating pads. Results: In controls, cooling decreased finger skin temperature (p = 0.003), microcirculatory flow, and forearm blood flow (p = 0.02) while increasing systolic and diastolic blood pressures (p = 0.005, p = 0.0008), forearm vascular resistance (FVR, p = 0.0002), and plasma NE (p = 0.004). The patients had attenuated FVR, skin microcirculatory flow, and plasma NE responses (p = 0.03 each), without attenuation of pressor responses. Interpretation: Cooling of back skin evokes reflexive cutaneous and forearm vasoconstriction and increases sympathetic noradrenergic outflows. Patients with neurogenic orthostatic hypotension and baroreflex failure have reduced local hemodynamic and noradrenergic responses but normal systemic hemodynamic responses to this stimulus. Cooling at skin of the back offers an alternative to manipulations decreasing cardiac venous return in evaluating sympathetic neurocirculatory reflexes.

Poster #71 Postganglionic sympathetic function in Parkinson’s disease and multiple system atrophy C. Noack1, K. Hahn1, L. Zange1, R. Rukwied2, M. Schmelz2, A. Lipp1 1 Department of Neurology, Charite´ University Medicine Berlin, Germany; 2 Clinics of Anaesthesiology and Intensive Care Medicine, University Medicine Mannheim, Germany Several recent studies propose the use of I123MIBG myocardial scintigraphy (MIBG) for early detection of Parkinsonism and for separation of Parkinson’s disease from Multiple System Atrophy. While depletion of striatal presynaptic dopamine transporter correlates well with motor deterioration, as assessed by UPDRS, cardiac sympathetic denervation (represented by reduced cardiac uptake of MIBG) does not. Autonomic reflex testing as usually performed tends to overemphasize preganglionic (baroreflex mediated) autonomic function. We sought to determine whether reduced cardiac MIBG uptake is accompanied with impaired sudomotor function in PD. To assess postganglionic sympathetic function, we combined clinical autonomic tests (heart rate and blood pressure responses to deep breathing, Valsalva maneuver, and 60° HUT), quantitative sudomotor axon reflex testing (electrically induced sweat response), and MIBG in 22 patients (MSA-P/C: n = 12, PD: n = 10) and eight control subjects. Cardiac MIBG was performed by an injection of 180 MBq I123 MIBG. Planar static images and SPECT were acquired 15 min and 4 h after injection using a dual-headed gamma camera. Sweat responses were evoked by transcutaneous electrical stimulation (7.5 mA, 20 Hz, 5 pulses in intervals of 2 s for 30 s) applied by

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330 3 9 10 mm adhesive electrodes placed 10 cm distal of the medial epicondyle of the most affected forearm. Quantitative sudometry was performed using two capsules continuously flushed with dry air (100 ml/min) and placed over the electrodes (active) and 3 cm distal (control). Change of temperature and humidity was used as a measure of sweat production. Our current results do not support our initial hypothesis of a correlation between cardiac sympathetic denervation (MIBG) and postganglionic sudomotor dysfunction in PD. Quantitative sudomotor testing did not differ between groups (p = 0.3; ANOVA). There was no meaningful correlation between sudomotor responses and cardiac MIBG scintigraphy (r2 = 0.05) in patients. However, in our small sample cardiac MIBG scintigraphy not always matched the clinical phenotype: H/M ratio was reduced in three cases with MSA; four cases with levodopa responsive PD showed normal myocardial MIBG scans. Our data suggest that myocardial denervation in PD occur independent from possible postganglionic sudomotor dysfunction. The frequent discrepancy between clinical phenotype and MIBG result in our study might give reason to readjust the importance of scintigraphic imaging in diagnosing movement disorders.

Clin Auton Res (2010) 20:289–330 in the 4–8 h post-meal sample. These substantial increases in plasma and urinary dopa and DA were unexpectedly associated with decreased, rather than increased, urinary sodium at 0–4 h post-FB (73 ± 21 vs. 130 ± 2 mEq/g creatinine, P = 0.023) and at 8–12 h post-FB (65 ± 43 vs. 118 ± 49 mEq/g creatinine, P = 0.011). Supine blood pressure was not significantly altered by FB meals. Our results indicate that FB robustly raise renal DA production. The decrease in urinary sodium might suggest that FB-mediated changes were, however, not sufficient to stimulate natriuresis or that FB inhibit urinary sodium excretion by some mechanism that does not involve renal DA.

Poster #73 Positron emission tomography guided placement of deep brain stimulator electrodes in the treatment of medically refractory cluster headache W.P. Cheshire, R.E. Wharen Department of Neurology, Mayo Clinic, Jacksonville, FL, USA

Poster #72 Fava bean ingestion potently alters catecholamine metabolism T. Smith Cesar, E.M. Garland, S. Lonce, D. Robertson Autonomic Dysfunction Center, Vanderbilt University, Nashville, TN, USA Fava beans (Vicia faba) contain dopa and their ingestion may benefit parkinsonism by increasing dopamine (DA). Outside the central nervous system, renal DA is believed to play a major role in the regulation of blood pressure and blood volume via its natriuretic effect. This study was conducted to determine the relationship between dietary fava beans (FB), plasma and urinary catechols and urinary sodium excretion. Ten participants [3 males; 8 whites and 2 blacks; 35.5 ± 13.4 (mean ± SD) years] were studied in balance on a fixed sodium, low monoamine diet. Catechol and sodium data after two FB meals (0800 h and 1200 h) were compared with data obtained on a separate day after fixed sodium study diet. Blood was sampled at 1, 2, 4 and 6 h after the 0800 h meal, and 3, 4-h urine samples were collected. Plasma dopa was significantly higher 1 h after the 0800 h FB meal when compared to the control diet (13,600 ± 5,850 vs. 1,670 ± 380 pg/mL, P \ 0.001) and remained elevated for the next 5 h. Plasma DA increased 20-fold during this period (at 1 h, 99 ± 55 vs. 4 ± 1 pg/mL, P = 0.002). FB meals also increased urinary DA (P = 0.009 for each of 3 comparisons), with the highest concentration averaging 2,330 ± 1,730 vs. 170 ± 50 lg/g creatinine (P = 0.009)

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Cluster headache consists of periodic, severe, unilateral, periorbital headaches accompanied by ipsilateral facial autonomic phenomena. These may include signs of parasympathetic hyperfunction (lacrimation, rhinorrhea, nasal congestion, and eyelid edema) combined with sympathetic hypofunction (ptosis and miosis) or sympathetic hyperfunction (facial sweating or flushing). Cluster headache was the first trigeminal autonomic cephalalgia in which functional cerebral imaging studies detected an ictal marker. Positron emission tomography (PET) and functional magnetic imaging (fMRI) studies have correlated cluster headache attacks with activation of the ipsilateral posterior hypothalamus. A number of studies have also detected altered activity in the thalamus or midbrain tegmentum. Variations in patterns of activation of the diencephalon and its connections among cluster headache patients may explain the variable outcomes so far attained in attempting to treat cluster headache with deep brain stimulation. We describe our preliminary results of utilizing PET in combination with vasodilator provocation to localize the target for placement of the deep brain stimulator electrode in severe cluster headache patients refractory to pharmacologic therapy. In a representative patient, reproduction of a typical headache by sublingual nitroglycerin 0.4 mg was associated with ipsilateral increased hypothalamic and thalamic signal on PET. The following day, a deep brain stimulator electrode was advanced through a stereotactic head frame to the posterior hypothalamus. Again, a typical headache was provoked by administering 0.4 mg nitroglycerin. Intraoperatively, when the trial stimulation was turned on, the headache promptly resolved, and when it was turned off, the headache returned. At 1 month of follow-up, the patient with deep brain stimulation remains completely pain-free.