Schwerpunkt Herzschr Elektrophys 2014 ∙ 25:236–240 DOI 10.1007/s00399-014-0330-x Published online: 29 July 2014 © Springer-Verlag Berlin Heidelberg 2014

Gerold Mönnig1,2 · Lars Eckardt1 1 Division of Electrophysiology, Department of Cardiovascular Medicine, University of Muenster,

Muenster, Germany 2 Abteilung für Rhythmologie, Department für Kardiologie und Angiologie, Münster, Germany

Multielectrode Pulmonary Vein Ablation Catheter (PVAC®) Current data on results and risks

Electrical isolation of pulmonary veins is the cornerstone of catheter ablation for patients with symptomatic atrial fibrillation (AF) [1]. However, uncertainty surrounds the choice of energy source in pulmonary vein isolation (PVI). Although the irrigated point-by-point radiofrequency (RF) ablation is the most frequently used technology, various alternative techniques such as the Pulmonary Vein Ablation Catheter (PVAC®, Medtronic Inc., Minneapolis, MN, USA) have been developed to facilitate PVI. This over-the-wire multielectrode catheter delivers duty-cycled bipolar and unipolar RF energy at relatively low power. The GENius multichannel, duty-cycled RF generator’s temperature-controlled standard energy setting at the PV antrum is a bipolar/unipolar energy ratio of 4:1. The power is limited to a maximum of 8–10 W per electrode, depending on the chosen bipolar/unipolar energy ratio. This multielectrode catheter technology delivers continuous lesions and shortens procedure times. It also has the potential to cause less unnecessary damage to atrial tissue. The ability to map and ablate through the same electrodes simplifies and shortens the procedure (.  Fig. 1 and 2). On the other hand, artifacts on the PVAC electrodes inhibit interpretation of the pulmonary vein potentials during RF application (. Fig. 2). The promises, limitations, risks, and pitfalls of this “one-shot-system” in comparison to other technologies are reviewed in the following article.

PVAC: safety and complications Concerns have been raised about the safety of the PVAC system after an increased incidence of silent cerebral embolisms using this phased RF ablation device in comparison with irrigated tip RF ablation or cryoablation were reported [2, 3]. In the animal model, using the multipolar PVAC catheter, the largest source of gaseous and solid emboli occurred when the distal and proximal electrodes (1 and 10) were in close proximity or overlapping [4, 5]. This electrode overlap creates a bipolar short circuit, resulting in excessive heating of tissue and blood. Several groups as well as our own have demonstrated that

Fig. 1 7 Ablation of pulmonary vein potentials with the PVAC catheter. Left Pulmonary vein potential (PVP; arrow) and mapping of earliest activation (asterix). Right Disappearance of PVP at the same position after phased RF

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the avoidance of an interaction between electrode 1 and 10 can reduce both silent cerebral microembolism as well as the rate of microembolic signals detected by transcranial Doppler ultrasound [6–8]. In the recent multicenter Evaluation of Reduction of Asymptomatic Cerebral Embolism Trial (ERASE) [6], deactivation of either the distal or proximal electrode reduced the incidence of asymptomatic cerebral embolisms (ACE) detected by magnet resonance imaging (MRI) to 1.7 % (in 1 out of 60 patients with disappearance after 1 month). In addition, the maintained activated clotting time was ≥ 350 s. This ACE incidence is at the lowest end compared to irrigated RF and cryoballoon [6].

Fig. 2 8 Phased ablation at the antrum of the culprit pulmonary vein. Signal before, during phased radiofrequency (RF) ablation with termination of atrial fibrillation and after phased RF. Note the fractionated and sharp pulmonary vein potentials (PVP) before ablation, the artifacts during phased RF and the disappearance of PVPs after ablation

In our own experience, cerebral microembolic signals (MES) during the procedure can be reduced when electrode pairs 1 or 5 are manually deactivated (556 vs. 1530; p < 0.001) and are comparable to the MES numbers during irrigated RF (646; p = 0.7) [7]. This difference is mainly triggered by the reduction of MES during delivery of phased RF energy. However, MES per minute ablation are still higher in phased RF compared to irrigated RF (15 vs. 2; p < 0.001) [7]. Another possible complication of PVI using PVAC is pulmonary venous stenosis. This specific complication has been investigated in 62 patients with CT scan before and 1 year after PVAC-PVI by Compier et al. [9]. They found a significant reduction in ostial area from 236 to 173 mm2 at 1-year follow-up independent from ablation outcome and left atrial remodeling. However, PV narrowing was mild and asymptomatic in all patients. It was speculated that the use of 4:1 energy delivery and avoidance of multiple applications might prevent PV stenosis. The overall incidence of PV notching (stenosis) may be higher in PVAC (around 5 %) compared to irrigated RF (around 4 %) [10].

Atrioesophageal fistula is a rare but fatal complication of PVI which has not been reported using PVAC so far. However, esophageal tissue injury has been described in 2 % of these patients identified by endoscopy [11]. In a consecutive cohort of 18 of our PVAC patients, we found mediastinal and esophageal structural changes in a substantial number of 6 patients by endosonography. All esophageal findings resolved under conservative management. Therefore, PVAC may also have the potential risk of atrioesophageal fistula formation. In addition to these specific complications, we also investigated clinical manifest safety endpoints and complication rates of 150 patients after PVAC-PVIs in direct comparison to the worldwide predominant energy source of 300 patients (age and gender matched) after irrigated RF-PVIs. Our data showed comparable safety with different complication profile: While bleeding and pericardial effusion occurred more often in irrigated RF group, infection and embolic events were more prevalent in the PVAC group. However, three of four clinically transient embolic events occurred in the PVAC group when all ten electrodes were used for PVI.

In conclusion, the reported higher incidence of silent embolic events might be reduced by deactivating electrode 10 to avoid the electrode 1–10 interaction or by the new catheter design of PVAC Gold®. The overall clinical safety seems to be comparable with irrigated RF and cryotechnology.

PVAC compared to irrigated RF and cryoballoon PVAC requires a single transseptal puncture; however, the vascular access at the femoral vein is larger (10F). Irrigated RF PVI requires a longer procedure time compared to PVAC and usually transseptal access with two catheters. Thus, instead of one two 8F sheaths are required. In a randomized study, we were able to demonstrate equal effectiveness of phased RF compared to irrigated RF in patient with drug refractory paroxysmal (55 %) or persistent AF (45 %) [12]. During a mean follow-up of 254 days, 72 % of the PVAC treated patients were free of AF recurrence compared to 68 % in the RF group irrespective of the initial type of AF. In that study, we also found an equal safety profile for paroxysmal and persistent AF irrespective of the ablation strategy. An-

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Abstract · Zusammenfassung Herzschr Elektrophys 2014 ∙ 25:236–240  DOI 10.1007/s00399-014-0330-x © Springer-Verlag Berlin Heidelberg 2014 G. Mönnig · L. Eckardt

Multielectrode Pulmonary Vein Ablation Catheter (PVAC®). Current data on results and risks Abstract Electrical isolation of pulmonary veins is the cornerstone of catheter ablation for patients with symptomatic atrial fibrillation. However, uncertainty surrounds the choice of energy source in pulmonary vein isolation (PVI). Various alternative techniques such as the Pulmonary Vein Ablation Catheter (PVAC®, Medtronic Inc., Minneapolis, MN, USA) have been developed to facilitate PVI. This overthe-wire multielectrode catheter is delivering duty-cycled bipolar and unipolar radiofrequency (RF) energy at relatively low power. PVI with this “one-shot” PVACatheter can shorten the procedure duration and low-

er fluoroscopy time compared to irrigated RF. It enables mapping and ablation with the same array, but fails to show signals during RF energy delivery. The effectiveness of PVAC is comparable to other technologies in randomized studies. The overall complication rate of PVAC PVI is comparable to irrigated RF and possibly slightly higher for cryoballoon PVI. Special attention has to be paid to an effective anticoagulation throughout the ablation procedure, avoidance of embolic events and pulmonary venous stenosis. The novel catheter design of the PVAC Gold® array may improve safety by reducing

embolic events through avoidance of electrode 1-to-10 interaction and by better tissue contact due to the 20° forward tilt. Although clinical data with this new array are lacking so far, the PVAC system has been shown to be a promising tool for PVI. However, prospective studies especially with the novel array are required to determine its true role for catheter ablation of atrial fibrillation in the future. Keywords Atrial fibrillation · Pulmonary vein isolation · Multielectrode catheter · Pulmonary Vein Ablation Catheter · Results and risks

Multielektroden-Pulmonalvenen-Ablationskatheter (PVAC®). Aktuelle Daten zu Nutzen und Risiken Zusammenfassung Die elektrische Isolation der Pulmonalvenen (PVI) ist nach wie vor ein entscheidender Endpunkt der interventionellen Behandlung von Vorhofflimmern (AF). Daher sind einige alternative „single-shot“ Kathetertechnologien wie der „Pulmonary Vein Ablation Catheter“ (PVAC®, Medtronic Inc., Minneapolis, MN, USA) entwickelt worden. Dieser Multielektrodenkatheter wird über einen Draht eingeführt und gibt eine phasenverschobene bipolare wie unipolare relativ niedrige Radiofrequenzenergie (RF) ab. Sowohl die Untersuchungsdauer als auch die Durchleuchtungszeit sind für dieses System kürzer verglichen mit der gekühlten RF-Energie. Dies kann durch den Vorteil des gleichzeitigen Mappings und Abladie-

other randomized study by Bulava et al. [13] included 51 patients in each group, all of them with paroxysmal AF. After a mean follow-up of 200 days, 77 % in the PVAC group and 71 % in the RF group were free of symptomatic or documented AF recurrences. In both studies, ablation procedure as well as fluoroscope times were significantly shorter for the PVACtreated patients. The long-term success at 3 years after first ablation was comparable for both energy sources in 161 patients [PVAC, (n = 79): 65 % vs. irrigated RF (n = 82): 55 %; n.s.] in a recent study [14]. In the randomized AF-COR study, Malmborg et al. [15] compared outcome and safety of PVAC versus cryoballoon in

rens bedingt sein, wobei die Signale während der Impulsabgabe artefaktbedingt nicht beurteilbar sind. Auch die Effektivität des PVACKatheters ist in randomisierten Studien vergleichbar mit anderen Technologien. Komplikationen treten bei PVAC-Therapie etwa gleich häufig auf wie bei gekühlter RF-Ablation und sind bei Kryoballonablation sogar geringfügig höher. Dennoch sollte dem Auftreten von Thrombembolien und Pulmonalvenenstenosen sowie einer effektiven Antikoagulation besonderes Augenmerk bei PVACPVIs gewidmet werden. Das neue Design des PVAC Gold® Katheters wird möglicherweise die Sicherheit verbessern, indem das Thrombembolierisiko durch die fehlende Interaktion der Elektroden

110 patients with paroxysmal or persistent AF. Complete PVI was accomplished in 98 % vs. 93 % (cryoballoon vs. PVAC) of patients with a complication rate of 8 vs. 2 %. In that study, only one periprocedural complication (major groin hematoma) occurred in the PVAC group compared to four in the cryoballoon group (groin hematoma in 2 patients and phrenic nerve paralysis in another 2 patients). Although the total procedure time was similar in both groups (around 165 min), significantly shorter ablation and fluoroscopy times were shown with cryoballoon (108 vs. 122 min and 32 vs. 47 min, respectively). After 12 months, freedom of AF without antiarrhythmic medication

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1 und 10 und durch einen besseren Gewebekontakt durch eine 20° Vorwärtsneigung der Katheterspirale verringert wird. Diesbezüglich liegen bislang allerdings noch keine klinischen Daten vor. Zusammenfassend stellt das PVAC-System eine vielversprechende Alternative zur PVI dar. Prospektive Studien mit dem neuen Katheterdesign sind erforderlich, um den zukünftigen Stellenwert des Verfahrens beurteilen zu können. Schlüsselwörter Vorhofflimmerablation · Isolation der Pulmonalvenen · Multielektrodenkatheter · Pulmonalvenen-Ablationskatheter · Nutzen und Risiko

was 46 and 34 %, respectively (difference not significant). Both groups achieved significant improvement in quality of life [15]. The same group of Malmborg et al. [16] found comparable markers of coagulation, endothelial damage, and inflammation, while cryoballoon causes a higher degree of myocardial destruction than PVAC. Phrenic nerve palsy is one of the most specific complication of cryoballoon PVI with a percentage varying between 0.7 and 11.2 % in the literature. There is just one single case report of a phrenic nerve injury using PVAC [17]. However, we have observed phrenic capture at the right superior PV in one of our PVAC pa-

rience with the first PVAC Gold® PVIs as compared to the former PVAC array. All PV veins were reached by the novel array and no clinical manifest complication occurred so far.

Conclusion

Fig. 3 9 The new PVAC Gold® array (left) in comparison to the PVAC® (right). Note the 20° forward tilt and the nine gold electrodes of the new designed array

tients that did not allow for complete PV isolation [12]. In conclusion, multielectrode PVAC currently seems to be comparable effective and safe as irrigated RF and cryoballoon.

PVAC in persistent AF Ablation of persistent AF is still a challenging and long-lasting procedure with varying success rates. In addition, variations in persistent AF are large. A single cardioversion turns a patient with paroxysmal AF into a persistent one and has to be distinguished from the patient with AF episodes for weeks or months which never terminate spontaneously. Having said this, Mulder et al. [18] described a 12-month success in 44 of 89 patients (49 %) with long-standing AF after a single procedure using three multielectrode catheters [PVAC, multi-array septal catheter (MASC) and multi-array ablation catheter (MAAC)]. Procedure as well as fluoroscopy time was relatively low (112 and 21 min, respectively) without a procedural complication rate. In the recent Tailored Treatment of Persistent Atrial Fibrillation (TTOP-AF) study, 210 patients with persistent or long-standing persistent AF refractory to at least one

antiarrhythmic drug were randomized to either medical management or phased RF ablation using only PVAC [19]. Of the ablated patients, 55.8 % achieved effectiveness vs. 26.4 % in the medication group. In that study, 21 acute major adverse events occurred in 17 of 138 patients (12.3 %). Stroke occurred in additional 4 patients (2.9 %) and PV stenosis in 5 (1 patient with symptoms). Including these symptomatic patients (n = 22), the overall complication rate (16 %) was relatively high [19].

PVAC Gold® A new catheter design (PVAC Gold®, Medtronic Inc., Minneapolis, MN, USA) has recently been launched with nine gold electrodes and a 20° forwardtilt (.   Fig. 3). PVAC Gold® is expected to achieve a more accurate temperature measurement compared to former used platinum. The incorporated forward tilt may improve the tissue contact compared to the perpendicular array. The most important advantage may be the lower thrombembolic risk by avoiding the electrode 1–10 interaction described before. Although no clinical data on this new array is available yet, it seems to be as safe and feasible in our own preliminary expe-

PVI with the one-shot multielectrode PVAC-catheter offers shorter procedure duration and lower fluoroscopy time compared to irrigated RF, while these times were equal or even shorter using cryoballoon. It facilitates mapping and ablation with the same array, but fails to show signals during RF energy delivery. The effectiveness of PVAC is comparable to other technologies in randomized studies. Treatment of long-standing persistent AF with PVAC is feasible while success rate is low like with other energy sources. The overall complication rate of PVAC, PVI is comparable to irrigated RF and possibly slightly lower than for cryoballoon PVI. Special attention should be paid to embolic events and pulmonary stenosis. The novel catheter design of the PVAC Gold® array may improve safety by reducing embolic events as it prevents electrode 1-to-10 interaction and allows for enhanced tissue contact due to the 20° forward tilt. However, clinical data with this new array are still lacking.

Corresponding address Dr. G. Mönnig Abteilung für Rhythmologie Department für Kardiologie und Angiologie Albert-Schweitzer-Campus 1 Gebäude A1, 48149 Münster [email protected]

Compliances with ethical guidelines Conflict of interest.  G. Mönnig and L. Eckardt state the following: Dr. Eckardt and Dr. Mönnig have received lecture honoraria and travel grants from Astra/Zeneca, Bayer, Johnson&Johnson, Biotronik, Boehringer Ingelheim, Boston Scientific, Bristol–Myers Squibb, Medtronic, Pfizer, Sanofi Aventis, and St. Jude Medical. Dr. Eckardt has received research grants from Biotronik, St. Jude Medical, Sanofi, and Osypka. Dr Eckardt holds the Peter Osypka Professorship for experimental and clinical electrophysiology. This article does not contain any studies with human or animal subjects.

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