World J. Surg. 25, 328–336, 2001 DOI: 10.1007/s002680020378

WORLD Journal of

SURGERY © 2001 by the Socie´te´ Internationale de Chirurgie

Endoluminal Treatment of Internal Carotid Artery Stenosis Klaus Mathias, M.D., Horst Jäger, M.D., Svenja Hennigs, M.D., Hans-Martin Gissler, M.D. Department of Radiology, Academic Teaching Hospital, Städtische Kliniken Dortmund, Beurhausstrasse 40, D-44 137 Dortmund, Germany Published Online: April 11, 2001

Abstract. Percutaneous transluminal stent-angioplasty of the carotid artery has indications that are similar but not identical to those for carotid surgery. Certain clinical conditions and morphologic findings, such as myocardial infarction, occlusion of the contralateral carotid artery, or tandem stenoses, favor use of the endoluminal technique. On the other hand, large clots at the site of stenosis, heavily calcified plaques, or elongated, kinked carotid arteries are better suited for carotid endarterectomy. Our experiences with angioplasty of more than 800 carotid stenoses and reports of other groups dealing with carotid angioplasty permit a preliminary evaluation of the method. The technical success rates, complication rates, and the few known long-term results are more or less equal to those of vascular surgery. Therefore further prospectively randomized studies are necessary to determine from which procedure the patient with his or her individual condition can gain the highest benefit.

Treatment of the internal carotid artery (ICA) stenosis aims at preventing a stroke. Any treatment method must prove its benefit for the patient compared to that derived from the natural course of the disease and conservative therapy. It is thought that embolic, thrombotic, and hemodynamic causes of a stroke are relat in only two-thirds of patients with carotid stenosis. Investigations such as the European (ECST) or North American (NASCET) studies of the efficacy of carotid surgery in symptomatic patients showed that the patients derive benefit from carotid endarterectomy (CEA) when the degree of stenosis exceeds 70% [1, 2]. In patients with less severe ICA stenosis, carotid surgery is not justified on the basis of these study results with few exceptions. In asymptomatic patients with a stenosis . 60%, the Asymptomatic Carotid Atherosclerosis Study (ACAS) trial statistically demonstrated a slight advantage for surgically treated male patients with a life expectancy of more than 2 years [3]. The indication for an invasive treatment of an ICA stenosis of . 80% in asymptomatic patients is confirmed by an evaluation of the ECST [4]. The American Heart Association established that the morbidity and mortality of CEA in asymptomatic patients should be , 3% and in symptomatic patients , 5%. Percutaneous transluminal treatment of ICA stenosis must meet the same criteria as the operative treatment. Whether the endovascular intervention can provide these results is discussed Correspondence to: K. Mathias, M.D.

below. Carotid surgery is the main method used for comparison when evaluating stent angioplasty of ICA stenoses. However, surgery cannot be considered the gold standard, as numerous patients treated by dilatation and stent placement would be excluded from operation based on the recruitment criteria of the NASCET and ECST trials [1, 2]. Angioplasty and Stent-Angioplasty of the ICA Percutaneous transluminal treatment of the ICA stenosis is not a completely new procedure, the first experiments with its use occurring during 1977–1979 [5, 6]. The first ICA stenosis was removed in 1979 when a symptomatic 32-year-old woman with fibromuscular dysplasia was referred to us. The first treated atherosclerotic stenosis, in 1980, was in a 64-year-old man [7], and we placed a stent for the first time to improve the result in a patient with an intimal flap after dilatation in 1989. With stent placement, endoluminal treatment of ICA stenoses achieved wide medical publicity because the combination of dilatation and stenting had better primary results and a lower complication rate than simple balloon dilatation [7–14]. Hence stent-angioplasty seems to be an alternative to carotid surgery and to justify further testing. Indications The indications for angioplasty and stent-angioplasty of the ICA depend on the clinical stage of the patient; the degree, morphology, and location of the stenosis; the underlying disease; and the regional cerebral perfusion. Clinical Stage. In clinical stage II patients with transient ischemic attacks (TIAs) and a stenosis of more than 70%, intervention is indicated. In stage I patients the decision for carotid stent angioplasty requires additional criteria, among which are a higher degree of stenosis (at least 80%), severe stenosis or occlusion of the contralateral ICA, or the need for a more extensive operation [15]. In the stage IV patient being treated after a minor stroke, another cerebral event at the ipsilateral hemisphere must be anticipated and the ICA is critically stenosed. An interval of 6 weeks is allowed to elapse between stroke and treatment to avoid the risk of cerebral hemorrhage during the early reperfusion

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Table 1. Clinical stage and carotid stent-angioplasty. Stage

Preconditions

Procedure

I

.80% Stenosis, pseudoocclusion; occlusion of the contralateral ICA; before major operations; life expectancy . 5 years TIA; . 70% stenosis; TIA under medication with a 50%–70% stenosis Crescendo infarction; still no demarcation of stroke on CT Prevention of reinfarction in patients with minor ipsilateral stroke; . 70% stenosis; occlusion of ICA and blood supply of contralateral hemisphere by contralateral ICA

Stent-angioplasty

II III IV

Stent-angioplasty Local thrombolysis, eventually combined with stentangioplasty Stent-angioplasty

ICA: internal carotid artery; TIA: transient ischemic attack; CT: computed tomography.

phase and to preserve the option of thrombolytic therapy in the case of a complicating thromboembolism. The size of the infarcted area does not influence the decision for treatment when the contralateral ICA is occluded and the ipsilateral ICA provides blood flow to the entire anterior cerebral circulation (Table 1). Degree of Stenosis. Based on experience with vascular surgery, the degree of stenosis should exceed 70%. It should not be estimated but measured precisely; otherwise data about the degree of stenosis are unreliable, usually overestimating it. We prefer to perform this measurement using the NASCET method because the ECST method overestimates the degree of stenosis [1, 2]. The calculation results from the formula

~a 2 b) 3 100%/a where a signifies the diameter of the ICA distal to the stenosis, and b is the diameter in the stenosis (Fig. 1). Angiograms in at least two planes are necessary for the measurements. The angiograms must be produced selectively and offer high resolution. Contrast medium injections in the aortic arch are insufficient for this purpose. Doppler sonography and magnetic resonance angiography (MRA) are not suited to determine the degree of stenosis precisely. Doppler sonography mostly overestimates the degree of stenosis considerably, and MRA shows intolerable deviations of the diameter values. A sonographically determined stenosis of 80% frequently corresponds to an angiographic stenosis of only 50% therefore would not be an indication to intervene. Morphology of Stenosis. The morphology of the stenosis is evaluated by duplex sonography, angiography, and if necessary spiral computed tomography (CT). Plaques with an intact fibrous cap are ideally suited for stent-angioplasty (Fig. 2). Ulcerated plaques can be treated likewise and do not pose a high embolic risk during the procedure [7, 16]. Large thrombi should not be treated by angioplasty alone. It is not known if thrombolytic pretreatment with urokinase or recombinant tissue plasmin activator is useful.

Fig. 1. Determining the degree of stenosis according to the North American Symptomatic Carotid Endarterectomy Trial (NASCET) method. a: diameter of the internal carotid artery (ICA) distal to the stenosis; b: diameter of the stenosis.

Long severe stenosis (so-called pseudoocclusion of the ICA) appears to present a high risk of embolism, as it always contains thrombus. Minor calcifications, which are contained in almost all plaques, do not hinder stent-angioplasty. Spiral CT is done in patients with large amounts of calcification. If a thick clasp of calcification is found that encircles (horseshoe-like) more than half of the artery’s circumference, we abandon the dilatation. In such cases angioplasty may lead to eccentric overdistension of the vessel wall and is accompanied by the risk of formation of a false aneurysm or rupture of the artery. Localizing the Stenosis. Most stenoses are located at the carotid bifurcation. It is essential for stent-angioplasty whether it deals with an ICA stenosis or a lesion extending from the common carotid artery (CCA) to the ICA. When the ICA stenosis is situated more than 1 cm distal to the bifurcation, the stent, usually with dimensions of 20 3 8 mm, is placed in the ICA, whereas a larger stent is required for bifurcation disease crossing the origin of the external carotid artery (ECA) (Fig. 3). The stent must then taper based on the diameters of the CCA and ICA. The stent, usually 10 3 30 mm, must adapt well to the vessel wall of the CCA and ICA to become coated by a thin neointima. It is an advantage of the endoluminal procedure that stenoses can be treated proximal and distal to the carotid bifurcation, solving the problem of

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Fig. 2. A 62-year-old man with two transient ischemic attacks (TIA) during the past 4 weeks. a.ICA 72% stenosis on the right side and a stent seen on the left side after stent-angioplasty 17 months ago. b. Stent (arrows) placed in the ICA without crossing the origin of the external carotid artery (ECA). After stent-angioplasty the arterial lumen is normal.

tandem stenoses. Principally, treatment is possible from the CCA origin at the aortic arch to the distal ICA at the skull base (pars petrosa and siphon). Etiology of Stenosis. More than 90% of patients with carotid stenosis suffer from atherosclerosis, but various other diseases must be considered for which angioplasty can be applied successfully (Fig. 4). Atherosclerotic carotid stenosis Fibromuscular dysplasia Neurofibromatosis Takayasu’s arteritis ICA stenosis after CEA: early: intimal flap, intimal proliferation,

clamping injury, fibrotic shrinkage at the anastomosis; late: progression of atherosclerosis ICA stenosis after radical neck dissection Postirradiation ICA stenosis Carotid stenosis due to fibromuscular dysplasia and Takayasu’s arteritis can be removed by simple balloon dilatation. Stenoses of a different pathophysiology are preferably treated with combined dilatation and stent placement. After radical neck dissection and radiotherapy the vascular wall is altered by scar tissue, and the stenosis is rigid. The risk of rupturing the vessel wall is increased in these patients. Therefore we dispense with the dilatation when a critical balloon pressure is reached and do not force an anatomically ideal dilatation result.

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Fig. 3. A 74-year-old man with coronary heart disease, aortocoronary bypass grafts, and several TIAs within 2 months. a. Note the 86% ICA stenosis on the right side with minor plaque extension in the common carotid artery (CCA). b. Stenosis is removed by stent-angioplasty. The stent crosses the ECA and is tapering well to the different diameters of the ICA and CCA.

Regional Cerebral Perfusion. Removal of an ICA stenosis aims at improving higher cortical functions and preventing stroke. In patients with obstructions of multiple brain-supplying arteries or with anomalies of the circle of Willis (most frequently hypoplasia or aplasia of the A1 segment of the anterior cerebral artery and missing cross-flow), careful analysis of the cerebral circulation is advisable and gives important information about the indications for treatment. When an ICA pseudoocclusion is fully compensated by the flow rate and blood distribution of the contralateral ICA and its collaterals, we abstain from an intervention. Should this vessel occlude, the growing thrombus will not overstep the carotid T when a functioning cross-flow is established via the anterior communicating artery. However, if angiography and measurement of regional cerebral perfusion show poor neurovascular reserve in the affected region, angioplasty is indicated.

technical limit for endoluminal treatment. In these patients direct puncture of the CCA may be helpful. We restrict this access to patients considered poor candidates for surgical treatment. The danger of carotid thrombosis or thromboembolism is probably increased using this approach. The small area in which the puncture and treatment take place increases the radiation dose to the hands of the radiologist. It must also be seen as risking carotid thrombosis during arterial compression after the procedure. When elongation of the ICA creates a hemodynamically significant kink, stent-angioplasty is not the appropriate treatment. Finally, bilateral iliac artery occlusions require a less favorable arterial access, such as the brachial or axillary artery. In patients with cerebral hemorrhage and fresh cerebral infarctions, clinical stability should be established to avoid cerebral bleeding as a sequelae of reperfusion.

Contraindications

Results

Stent-angioplasty should not be applied to stenoses with more than semicircular thick calcifications or large fresh thrombus because of the increased risk of arterial rupture or embolism. Extreme dilatation and elongation of the arterial system may be a

The indications for endoluminal treatment of an ICA stenosis must be evaluated not only from the viewpoint of technical feasibility but from the viewpoints of the success rate, complication rate, and patency rate. The technical success rate is defined as

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Fig. 4. A 68-year-old woman with recurrent disease 16 months after carotid endarterectomy (CEA) a. The ECA is occluded. The operative area contains a thrombus; and an 86% stenosis has developed distal to the endarterectomy site. b. After stent-angioplasty there is a smoothly delineated carotid artery with a minor spastic reaction of the distal ICA.

successful passage and dilatation of the stenosis. A hemodynamically irrelevant residual stenosis (, 20%) is accepted as a successful result based on this definition. With the techniques available today, success rates of 94% to 99% are reached. Significant residual stenoses (. 50%) are observed in patients with calcification or fibrosis of the vessel wall after surgery or radiotherapy. Complications are divided into nondisabling and disabling neurologic deficits and death. We differentiate neurologic deficits according to the Rankin scale, which classifies values of 0 –2 as minor stroke and 3–5 as major stroke. The mortality rate is defined as all deaths within 30 days after the intervention. Minor strokes amount to about 5% using this definition, with reported stroke rates between 2% and 9%. Major strokes occur in about 1% and deaths in , 1% [7, 13, 17]. Preliminary results of a prospective randomized trial (CAVATS

study) with angioplasty and carotid surgery have shown no significant differences between the two methods in a group of 560 patients. A single-center randomized study reported a somewhat higher rate of TIAs and minor strokes in the group of endoluminally treated patients compared to those who underwent surgery [18]. If one considers the fact that most interventional groups have their learning curve included in these figures and that they treat patients who are poor candidates for surgery for various medical reasons, the results of stent-angioplasty are encouragingly favorable. Only a few studies have reported long-term results of stentangioplasty. We have ascertained a 5-year patency rate of more than 90% (Fig. 5) [7, 13]. The team from Alabama (USA) found a 3-year recurrence rate of 3% [12]. Evidently, the long-term results are considerably more favorable than those of angioplasty

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Table 2. Differential indications for treatment of ICA stenosis.

Findings Contralateral carotid occlusion/ stenosis . 70% Short stenosis with intact surface Ulcerated stenosis Long filiform stenosis (. 25 mm) Irregular stenosis with protruding atherosclerotic material and thrombotic layer Postoperative recurrent stenosis Radiation stenosis Thick more than semicircular calcification Fibromuscular dysplasia Takayasu’s arteritis Spontaneous or traumatic carotid dissection Increased operative risk Female gender

Angioplasty/stentangioplasty preferred

CEA/eversion procedure preferred

XXX

X

XXX XX X X

X XX XXX XXX

XXX XXX –

X – XXX

XXX XXX XX

X – –

XXX XXX

X XX

CEA: carotid endarterectomy; –: not indicated; X: exceptionally or as a reserve method indicated; XX: indicated; XXX: preferably indicated.

dence-based medicine if possible— carotid stent-angioplasty should be accomplished only under study conditions. Basic requirements should be fulfilled, such as profound neurologic, neurophysiologic, and neuroradiologic knowledge, sufficient experience with catheter techniques, and the availability of a neurologic department in the hospital. Résumé

Fig. 5. Control angiogram 6 months after stent-angioplasty of an ICA stenosis. The stent covering the arterial segment shows slight widening and in-growth into the deeper layers of the arterial wall because of its radial force. The stent has no contact with the bloodstream. There is no myointimal proliferation.

of the coronary or leg arteries. Unquestionably, further studies are necessary for a more definitive evaluation of carotid stentangioplasty. Outlook Even with not entirely satisfying data about the chances and limits of carotid stent-angioplasty, we have collected enough evidence to give a preliminary recommendation concerning the differential indications for the treatment of ICA stenosis by surgery or endovascular intervention (Table 2). Presently, the use of carotid stent-angioplasty is spreading rapidly in the medical community, with the danger of uncritical application. Until a definitive evaluation of the method— by evi-

L’angioplastie transluminale percutanée de l’artère carotide par pose de stent a des indications similaires, mais non identiques, à la chirurgie. L’état clinique et des données morphologiques tels l’infarctus du myocarde, l’occlusion de la carotide contra-latérale ou des sténoses étagées sont plutôt des indications de la méthode endoluminale. D’un autre côté, des caillots sanguins plus volumineux au niveau de la sténose, les plaques fortement calcifiées, ou les artères tortilleuses, allongées, avec plicature, se prêtent mieux à l’endartérectomie. Notre propre expérience avec plus de 800 sténoses carotidiennes et les comptes-rendus d’autres groupes faisant état de leurs résultats d’angioplastie carotidienne permettent une première évaluation de la méthode. Les taux de succès technique, les taux de complications et les résultats à long terme, peu connus jusqu’à présent, sont plus ou moins égaux à ceux de la chirurgie vasculaire. D’autres études prospectives, randomisées, sont nécessaires pour savoir quel procédé est le mieux adapté à chaque patient pour en tirer le maximum de bénéfices. Resumen La angioplastia percutánea con colocación transluminal de un injerto (stent) en la arteria carótida tiene indicaciones semejantes, pero no idénticas, a las de la cirugía carotídea. El estado clínico y los hallazgos morfológicos que principalmente propician la técnica endoluminal son: el infarto cardiaco, la oclusión de la

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arteria carótida contralateral y la existencia, en la arteria carótida afectada, de múltiples estenosis. Por el contrario la endoarteriectomia carotídea está formalmente indicada cuando: existan grandes trombos a nivel de las estenosis, grandes placas ateromatosas muy calcificadas y en las carótidas elongadas y racemosas. Nuestra experiencia con angioplastias en más de 800 estenosis carotídeas, junto con las publicaciones de otros grupos que también efectúan angioplastias, nos permite efectuar una evaluación preliminar de este proceder. El porcentaje de éxito técnico, de las complicaciones y los poco conocidos resultados a largo plazo son más o menos similares a los obtenidos con cirugía vascular. Por ello, se precisa un mayor número de estudios prospectivos y randomizados para decidir que procedimiento es más beneficioso para el paciente, teniendo muy en cuenta sus circunstancias personales.

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6. 7. 8. 9. 10. 11.

12.

Acknowledgments We thank our colleagues of the Neurological Department, particularly its chairman, H.-O. Lincke, M.D., for their constant responsiveness, advice, and support.

13.

References

15.

1. European Carotid Surgery Trialists Collaborative Group MRC European Carotid Surgery Trial: interim results for symptomatic patients with severe (70 –99%) or mild (0 –29%) carotid stenosis. Lancet 337:1235, 1991 2. North American Symptomatic Carotid Endarterectomy Trial Collaborators Beneficial effect of carotid emdarterectomy in symptomatic patients with highgrade carotid stenosis. N. Engl. J. Med. 325:445, 1991 3. Executive Committee for the Asymptomatic Carotid Atherosclerosis Study Endarterectomy for asymptomatic carotid artery stenosis. J.A.M.A. 273:1421, 1995 4. European Carotid Surgery Trialists’ Collaborative Group Randomised trial of endoarterectomy for recently symptomatic carotid stenosis: final results of the MRC European Carotis Surgery Trial (ECST). Lancet 351:1379, 1998 5. Mathias, K.: Ein neuartiges Kathetersystem zur perkutanen translu-

Invited Commentary DOI: 10.1007/s002680020379

Hugh G. Beebe, M.D. Jobst Vascular Center, Toledo, Ohio, USA Published Online: April 11, 2001

It was with great interest that I read the summary by Mathias and his colleagues on the current status of endoluminal treatment of carotid artery disease because of Professor Mathias’s known longstanding interest in this approach to stroke prevention. Frequently, at continuing medical education meetings and professional conferences where carotid stenting is discussed, it sometimes appears that fascination with this technique obscures the goal of stroke prevention. A great many of the papers on the

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16.

17.

18.

minalen Angioplastie von Karotisstenosen. Fortschr. Med. 95:1007, 1977 Mathias, K., Mittermayer, C., Ensinger, H., Neff, W.: Perkutane Katheterdilatation von Karotisstenosen. Rofo Fortschr Geb Rontgenstr Neuen Bildgeb Verfahr 133:258, 1980 Mathias, K.: Perkutane transluminale Katheterbehandlung supraaortaler Arterienobstruktionen. Angiologia 3:47, 1981 Bergeron, P., Chambran, P., Bianca, S., Benichou, H., Massonat, J.: Traitement endovasculaire des artères a destinée cérébrale: echecs et limites. J Mal Vasc (Suppl. A) 21:123, 1996 Diethrich, E.B., Ndiaye, M., Reid, D.B.: Stenting in the carotid artery: initial experience in 110 patients. J. Endovasc.Surg. 3:42, 1996 Kachel, R., Basche, S., Heerklotz, I., Grossmann, K., Endler, S.: Percutaneous transluminal angioplasty (PTA) of supra-aortic arteries especially the internal carotid artery. Neuroradiology 33:191, 1991 Robbin, M.L., Lockhart, M.E., Weber, T.M., Vitek, J.J., Smith, J.K., Yadav, J., Mathur, A., Iyer, S.S., Roubin, G.S., Yadav, S., Iyer, S.S., Vitek, J.: Carotid stent-supported angioplasty: a neurovascular intervention to prevent stroke. Am. J. Cardiol. 78:8, 1996 Robbin, M.L., Lockhart, M.E., Weber, T.M., Vitek, J.J., Smith, J.K., Yadav, J., Mathur, A., Iyer, S.S., Roubin, G.S.: Carotid artery stents: early and intermediate follow-up with Doppler US. Radiology 205:749, 1997 Theron, J.G., Payelle, G.G., Coskun, O., Huet, H.F., Guimaraens, L.: Carotid artery stenosis: treatment with protected balloon angioplasty and stent placement. Radiology 201:627, 1996 Yadav, J.S., Roubin, G.S., Iyer, S., Vitek, J., King, P., Jordan, W.D., Fisher, W.S.: Elective stenting of the extracranial carotid arteries. Circulation 95:376, 1997 Babatasi, G., Massetti, M., Theron, J., Khayat, A.: Asymptomatic carotid stenosis in patients undergoing major cardiac surgery: can percutaneous carotid angioplasty be an alternative? Eur. J. Cardiothorac. Surg. 11:547, 1997 Mathur, A., Roubin, G.S., Iyer, S.S., Piamsonboon, C., Liu, M.W., Gomez, C.R., Yadav, J.S., Chastain, H.D., Fox, L.M., Dean, L.S., Vitek, J.J.: Predictors of stroke complicating carotid artery stenting. Circulation 97:1239, 1998 Wholey, M.H., Wholey, M., Bergeron, P., Diethrich, E.B., Henry, M., Laborde, J.C., Mathias, K., Subbarao, M., Roubin, G.S., Shawl, F., Theron, J.G., Yadav, J.S., Dorros, G., Guimaraens, J., Higishada, R., Kumar, V., Leon, M., Lim, M., Londero, H., Mesa, J., Ramee, S., Rodriguez, A., Rosenfield, K., Teitelbaum, G., Vozzi, C.: Current global status of carotid artery stent placement. Cathet. Cardiovasc. Diagn. 44:1, 1998 Jordan, W.D., Jr., Schroeder, P.T., Fisher, W.S., McDowell, H.A.: A comparison of angioplasty with stenting versus endarterectomy for the treatment of carotid artery stenosis. Ann. Vasc. Surg. 11:2, 1997

subject of carotid stenting have not described a hypothesis that is being prospectively tested and endpoints by which the data can be interpreted [1]. Hence it is important that Mathias et al. state at the outset of their article that the goal of treatment is “prevention of a stroke.” Among surgeons, neurologists, and cardiologists in the United States, there has been concern over the rapid expansion of the use of carotid stenting on the basis of limited data [2]. The morbidity of stroke is so great that only the best level of evidence should be accepted for definitive guidance in clinical decision-making. When single-institution results are reported by those who are also developers of devices and equipment relevant to the field, the possibility of bias in reporting is introduced [3]. As the literature on carotid stenting moves past anecdotal and single-institution reports of evidence toward prospectively gathered data from monitored trials, the quality of data will increase and be more generally applicable. It is encouraging that in the United States several

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industry-sponsored trials, including one that randomly compares carotid stenting and endarterectomy, are under way [4]. Also, the National Institutes of Health has recently approved and funded a randomized prospective trial comparing stenting and endarterectomy for prevention of stroke due to carotid artery stenosis [5]. It was anticipated that this trial would have begun entering patients in 1999. The present paper by Mathias and colleagues is an expression of their opinion about the current status of carotid stenting and contains a number of generalizations and conclusions without supporting data by which to evaluate them. This opinion is certainly valuable, coming from a pioneer in the field with a large experience, but it should be recognized as such. Some specific points seem especially thought-provoking. Mathias et al. and others writing about carotid stenting place considerable emphasis on the fact that many patients treated by stenting would not have met the inclusion criteria of the NASCET, ACAS, and ECST studies. None of these trials designed their inclusion/exclusion criteria as risk stratification standards for carotid disease treatment. For that reason it does not seem appropriate to use them for such a purpose. Some specific examples can illustrate the point. In the NASCET trial, for example, patients were excluded from entry if they were over 80 years of age, lacked arteriographic visualization of the intracranial branches, had co-morbidity (e.g., kidney, liver, lung) likely to cause death within 5 years, had cardiac disease associated with cardioembolic symptoms, or had previously undergone carotid endarterectomy [6]. All of these criteria were used in the NASCET trial for the purpose of ensuring a high quality data set to answer the questions of the trial. They were not intended to be used for the purpose of measuring the risk for carotid surgery or any other procedure. It is also recommended here that a delay of 6 weeks occur between a stroke and carotid stenting to avoid intracerebral hemorrhagic risk and to “preserve the option of thrombolytic therapy in case of complicating thromboembolism” associated with carotid stenting. An increasing number of authors have questioned the traditional 6-week interval in recent years because of the stroke risk during the delay [7, 8]. It seems ill-advised to delay treatment simply to increase the potential for using thrombolytic therapy. The subject of carotid ultrasonography is too complex and controversial to discuss in detail here. However, Mathias et al. seem to dismiss its use as being “not suited to determine the degree of stenosis precisely.” Our practice leads us to an entirely opposite conclusion [9]. Furthermore, there are an increasing number of reports of successful carotid disease management based exclusively on carotid duplex imaging. Mathias et al.’s insistence of selective carotid catheterization for diagnostic arteriography can be expected to increase morbidity and cost [10]. Moreover, failure to interrogate carotid arteries by best quality B-mode imaging with modern duplex equipment may result in failure to record important details of plaque morphology that could aid in assessing which lesions are best suited to carotid stenting. In the discussion of stenosis morphology, Mathias and colleagues note that ulcerated plaques are not associated with a higher embolic risk. This may be true, but we should remember that our ability to identify the state of carotid ulceration by arteriography is not good. Probably the best evidence for this

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comes from the NASCET trial observation comparing preoperative arteriography with direct observation of the specimen prospectively in 500 patients [11]. The sensitivity and specificity of assigning ulceration status were only 45.9% and 74.1%, respectively, and therefore the assignments were often in error. This finding did not vary with the degree of stenosis. Given the limitation of arteriography to identify ulceration correctly, the opinion that ulceration is not a risk for carotid stenting seems to be a bold statement that puzzles carotid artery surgeons who look at the unstable surface of the carotid plaque with caution. Calcification in the carotid atheroma is common, especially so with high degrees of stenosis. If analogy with other arterial stenting experience is any guide, the iliac arteries serve as a good example: High levels of calcification predict a poor outcome, as Mathias et al. indicate. We presently lack a clinical grading scale for the amount of vessel calcification. Obtaining a cervical CT scan to identify the radial extent of calcification seems to be the best method presently available, but one wonders about the cost of obtaining this examination for the purpose of judging suitability for carotid stenting. In the section on localizing the stenosis, it is stated that, “It is an advantage of the endoluminal procedure that stenoses can be treated proximal and distal to the bifurcation, solving the problem of tandem stenoses.” This frank statement is surprising, as tandem stenoses have been specifically identified as an increased risk factor for stroke following carotid stenting by Roubin and colleagues [12]. In addition, the section on regional cerebral perfusion advises that carotid angioplasty is indicated if “measurement of regional cerebral perfusion show a poor neurovascular reserve.” The question remains how this measurement is accomplished. Do Mathias et al. mean an anatomic survey by arteriography, SPECT scanning by radioisotope, or PET scanning? One suspects the first method is what he has in mind. If so, it is also surprising because the large literature on this subject derived from carotid endarterectomy experience fails to reveal that it can be used to predict stroke risk. All of us should admire those who explore new treatment alternatives with careful accumulation of high quality data and primary concern for patient safety. Whether carotid endarterectomy can be replaced by stenting in a large number of patients remains to be seen. One thing is known for sure: that carotid endarterectomy is the most carefully studied vascular surgical procedure. What is known about carotid endarterectomy comes from highest quality data, and nothing less than similar-quality prospective clinical trials with appropriate controls, adjudication, and oversight will serve as a comparison between the two procedures. The reference (19 in Dr. Mathias’ paper cited as evidence) to support the opinion that carotid stenting results are “more or less equal to those of vascular surgery” includes information about the 30-day outcome of 2048 patients treated with carotid stents, but it is derived from a questionnaire sent to selected sites on four continents with no described control over reporting standards or data adjudication [13]. This type of report does not meet the level of evidence available by which to judge the safety of carotid endarterectomy. The foregoing comments are critical in nature and meant to be constructively so: The editors have asked a known critic of carotid stenting to supply them. Perhaps some surgical opinion could be added to that provided by Mathias et al. to expand the perspective

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on carotid stenting. There is nothing to indicate that carotid stenting will not find its proper place among methods of stroke prevention. Results are steadily improving, probably reflecting more sophisticated case selection and improved technique. There are also a large number of stents and devices specifically designed for the carotid application that can be expected to make the procedure work better and be safer than it is today. Mathias et al. state in their conclusion that there is a “danger of uncritical application” and that a definitive evaluation of the method “by evidence-based medicine” should be accomplished. On these points we agree completely. References 1. Beebe, H.G.: The carotid angioplasty premise. Vasc. Surg. 30:269, 1996 2. Beebe, H.G., Archie, J.P., Baker, W.H., Barnes, R.W., Becker, G.J., Bernstein, E.F., Brener, B., Clagett, G.P., Clowes, A.W., Cooke, J.P.: Concern about safety of carotid angioplasty. Stroke 27:197, 1996 3. Theron, J.G., Payelle, G.G., Coskun, O., Huet, H.F., Guimaraens, L.: Carotid artery stenosis: treatment with protected balloon angioplasty and stent placement. Radiology 201:627, 1996 4. Beebe, H.G.: Scientific evidence demonstrating the safety of carotid angioplasty and stenting: do we have enough to draw conclusions yet? J. Vasc. Surg. 27:788, 1998 5. Hobson, R.W., II, Brott, T., Ferguson, R., Roubin, G., Moore, W., Kuntz, R., Howard, G., Ferguson, J.: CREST: carotid revascularization endarterectomy versus stent trial. Cardiovasc. Surg. 5:457, 1997

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6. North American Symptomatic Carotid Endarterectomy Trial Collaborators Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N. Engl. J. Med. 325:445, 1991 7. Beebe, H.G.: Surgery for acute stroke. Semin. Vasc. Surg. 8:55, 1995 8. Whittemore, A.D., Ruby, S.T., Couch, N.P., Mannick, J.A.: Early carotid endarterectomy in patients with small, fixed neurologic deficits. J. Vasc. Surg. 1:795, 1984 9. Beebe, H.G., Salles-Cunha, S.X., Scissons, R.P., Dosick, S.M., Whalen, R.C., Gale, S.S., Pigott, J.P., Siewert, A.J.: Carotid arterial ultrasound imaging: A direct approach to stenosis measurement. J. Vasc. Surg. 29:838, 1999 10. ACAS (Executive Committee for the Asymptomatic Carotid Atherosclerosis Study) Endarterectomy for Asymptomatic carotid artery stenosis. J.A.M.A. 273:1421, 1995 11. Streifler, J.Y., Eliasziw, M., Fox, A.J., Benavente, O.R., Hachinski, V.C., Ferguson, G.G., Barnett, H.J.: Angiographic detection of carotid plaque ulceration: comparison with surgical observations in a multicenter study; North American Symptomatic Carotid Endarterectomy Trial. Stroke 25:1130, 1994 12. Mathur, A., Roubin, G.S., Iyer, S.S., Piamsonboon, C., Liu, M.W., Gomez, C.R., Yadav, J.S., Chastain, H.D., Fox, L.M., Dean, L.S., Vitek, J.J.: Predictors of stroke complicating carotid artery stenting. Circulation 97:1239, 1998 13. Wholey, M.H., Wholey, M., Bergeron, P., Diethrich, E.B., Henry, M., Laborde, J.C., Mathias, K., Myla, S., Roubin, G.S., Shawl, F., Theron, J.G., Yadav, J.S., Dorros, G., Guimaraens, J., Higashida, R., Kumar, V., Leon, M., Lim, M., Londero, H., Mesa, J., Ramee, S., Rodriguez, A., Rosenfield, K., Teitelbaum, G., Vozzi, C.: Currently global status of carotid artery stent placement. Cathet. Cardiovasc. Diagn. 44:1, 1998