Carotid artery stenting: to be or not to be?

Carotid endarterectomy (CEA) has been the standard of care for suitable patients with symptomatic or asymptomatic high grade carotid stenosis since the landmark NASCET (North American Symptomatic Carotid Endarterectomy Trial), ECST (European Carotid Surgery Trial) and ACAS (Asymptomatic Carotid Artery Surgery) studies performed in the 1990s and more recently the ACST (Asymptomatic Carotid Surgery Trial). Carotid artery stenting (CAS) in the treatment of both symptomatic and asymptomatic patients with high grade carotid stenosis has recently been investigated as an alternative to CEA. We present a review of the most recent CAS trials and examine some of the controversies that surround them.     

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Background

Carotid endarterectomy (CEA) is a common procedure performed in patients who have suffered a stroke or transient ischaemic attack (TIA) to prevent a recurrent event. Clinical trials have provided evidence for the safety and efficacy of CEA in patients with recently symptomatic stenosis. Carotid artery stenting is an alternative to CEA. However, medical treatment has improved in the last 30 years and trials are ongoing to assess the use of modern medical treatment in selected patients with carotid disease as an alternative to revascularization.

Methods

We have reviewed the published results from clinical trials investigating the best treatment for symptomatic and asymptomatic carotid artery stenosis. In this review we discuss carotid endarterectomy, stenting and medical treatment. We have also included an update on the Second European Carotid Surgery Trial (ECST-2) which is an ongoing trial comparing revascularization to optimized medical therapy in patients with low to intermediate risk of recurrent stroke.

Results

The North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the European Carotid Surgery Trial (ECST) both show that patients with high-risk symptomatic carotid stenosis benefit from CEA over medical treatment alone. However, it has been shown that surgery appeared to be harmful or at least not beneficial in patients included in the trials whose characteristics predicted a low risk of recurrent stroke. The Asymptomatic Carotid Surgery Trial (ACST) also showed a small benefit in treating asymptomatic patients with CEA over medical therapy. Several published trials have compared stenting with endarterectomy and although endarterectomy appears safer in the short term, both treatments have similar long-term outcomes; therefore stenting can be used as an alternative to CEA for selected patients.

Conclusion

CEA and stenting can both be offered to patients with recently symptomatic carotid stenosis to prevent recurrent stroke. We await the results of current trials investigating the role of modern medical therapy in selected patients with low to intermediate risk of recurrent stroke as an alternative to revascularization. The English full-text version of this article is available at SpringerLink (under “Supplemental”).     

Audit of 149 consecutive carotid endarterectomies performed by a single surgeon in a district general hospital over a 12-year period.

Carotid endarterectomy has been established by two large randomised controlled trials (European Carotid Surgery Trial (ECST) and North American Symptomatic Carotid Endarterectomy Trial (NASCET)) as an important surgical procedure for the prevention of ischaemic strokes in patients presenting with transient cerebral ischaemia or non-disabling strokes attributable to severe ipsilateral carotid artery stenosis. The operation carries significant risk of death and stroke and it has been advocated by some that carotid endarterectomy should only be performed in a small number of designated regional centres in order to achieve good surgical results. It is doubtful that the regional centres alone can cope with the increasing numbers of patients requiring carotid endarterectomy and there is therefore a requirement for the procedure to be carried out by vascular surgeons in district general hospitals. It is important that surgical results are audited to ensure that comparable outcomes are achieved. We present an audit of our experience of carotid endarterectomy since 1981. A total of 149 consecutive carotid endarterectomies were performed by a single surgeon with a special interest in carotid surgery. The results are comparable to ECST with a 30-day mortality of 0% and an overall 30-day stroke rate of 5.7% (major strokes) for patients with severe, ie 70-99%, ipsilateral carotid artery stenoses. We have shown that carotid endarterectomy is an operation that can be performed safely and with good results by suitably trained surgeons in district general hospitals.     

Carotid endarterectomy in patients with contralateral carotid occlusion

Total occlusion of the contralateral internal carotid artery has often been considered to be a predictor of adverse neurologic outcomes following carotid endarterectomy of an ipsilateral carotid stenosis. Results from both the North American Symptomatic Carotid Endarterectomy Trial and the Asymptomatic Carotid Atherosclerosis Study have suggested this to be true. However, each of these trials had relatively few patients with contralateral occlusion in the surgical arms of the studies. In contrast to these studies, there are multiple surgical series in the literature demonstrating excellent results of carotid endarterectomy in patients with contralateral total occlusion. Recently, advocates of carotid angioplasty and stenting have suggested that this technique may be preferable in patients with a contralateral occlusion because of the perceived poor outcomes with surgery. As carotid angioplasty and stenting becomes more popular, it is becoming even more crucial to better define those patients who are truly at increased risk following carotid endarterectomy; ultimately, this will help clinicians decide which patients may derive the most benefits from endovascular therapies. With these issues in mind, the purpose of this review is to examine results of carotid endarterectomy in patients with total occlusion of the contralateral carotid artery.     

A new idea for a safer approach to the supra-aortic trunks: the Piton™ catheter

Carotid artery disease is among the most common causes of stroke, and stroke is the third leading cause of death in industrialized countries. Thus the personal health and socioeconomic burden of carotid artery disease is significant. Carotid artery disease accounts for approximately 5-12% of new strokes in patients amenable to revascularization therapy. Atherosclerosis is the main reason for stroke and accounts for approximately one third of all cases. Carotid stenting is nowadays considered a valid standard alternative to surgical carotid endarterectomy, especially in patients having a high perioperative risk. The first carotid balloon angioplasty was carried out in 1979 and the first carotid balloon-expandable bare metal stents were implanted 10 years later, in 1989. However, carotid stenting at that time was associated with major complications, due to extrinsic compression and subsequent to the steel stents used. The Piton? GC (carotid guide catheter) is intended to facilitate the introduction and placement of interventional devices (e.g., guidewires, stent delivery systems, dilation balloons, angiographic- or micro-catheters, etc.) into the human vasculature to treat vascular obstructive disease, including but not limited to the supra-aortic vessels.     

Japan Carotid Atherosclerosis Study: JCAS

The recent randomized trials, North American Symptomatic Carotid Endarterectomy Trial, European Carotid Surgery Trial, and Asymptomatic Carotid Atherosclerosis Study, have demonstrated the effectiveness of carotid endarterectomy to reduce the incidence of cerebral infarction in patients with symptomatic and asymptomatic high-grade carotid artery stenosis. However, no studies on Japanese patients have been done until now, and recent progress in endovascular stent treatment has been made. The present prospective, multicenter (not randomized) trial, the Japan Carotid Atherosclerosis Study, has started to analyze present practice and propose treatment guidelines for Japanese patients. Here, the protocol and early results of 565 patients registered until the end of January 2004 are presented.     

Patient selection for carotid stenting versus endarterectomy: a systematic review

Carotid artery stenting has emerged as an alternative to carotid endarterectomy for the treatment of severe extracranial carotid stenosis in patients with anatomic or clinical factors that increase their risk of complications with surgery, yet there remains a substantial amount of variability and uncertainty in clinical practice in the referral of patients for stenting vs endarterectomy. By undertaking a thorough review of the literature, we sought to better define which subsets of patients with "high-risk" features would be likely to preferentially benefit from carotid stenting or carotid endarterectomy. Although only a single randomized trial comparing the outcomes of carotid stenting with distal protection and endarterectomy has been completed, a wealth of observational data was reviewed. Relative to endarterectomy, the results of carotid stenting seem favorable in the setting of several anatomic conditions that render surgery technically difficult, such as restenosis after prior endarterectomy, prior radical neck surgery, and previous radiation therapy involving the neck. The results of stenting are also favorable among patients with severe concomitant cardiac disease. Carotid endarterectomy, alternatively, seems to represent the procedure of choice among patients 80 years of age or older in the absence of other high-risk features. Overall, existing data support the concept that carotid stenting and endarterectomy represent complementary rather than competing modes of therapy. Pending the availability of randomized trial data to help guide procedural selection, which is likely many years away, an objective understanding of existing data is valuable to help select the optimal mode of revascularization therapy for patients with severe carotid artery disease who are at heightened surgical risk.     

Prospective evaluation of new duplex criteria to identify 70% internal carotid artery stenosis

Purpose: Large multicenter trials (North American Symptomatic Carotid Endarterectomy Trial, European Carotid Surgery Trial) have documented the benefits of carotid endarterectomy for treating symptomatic patients with ≥70% stenosis of the internal carotid artery. Although color-flow duplex scanning has become the preferred method for noninvasive assessment of internal carotid artery disease, no criteria have been generally accepted to identify this subset of patients. We previously reported a retrospective series to establish such criteria. This study details our results when these criteria were applied prospectively.Methods: Carotid color-flow duplex scans were compared with arteriograms in 457 patients who underwent both studies. Criteria for ≥70% internal carotid artery stenosis were peak systolic velocity >130 cm/sec and end-diastolic velocity >100 cm/sec. Internal carotid arteries with peak systolic velocity <40 cm/sec in which only a trickle of flow could be detected were classified as preocclusive lesions (95% to 99% stenosis). Arteriographic stenosis was determined by comparing the diameter of the internal carotid artery at the site of maximal stenosis to the diameter of the normal distal internal carotid artery.Results: Internal carotid artery stenosis of ≥70% was detected with a sensitivity of 87%, specificity of 97%, positive predictive value of 89%, negative predictive value of 96%, and overall accuracy of 95%. Eighty-seven percent of 70% to 99% stenoses were correctly identified. False-positive errors (n = 10) were attributed to contralateral internal carotid artery occlusion or high-grade (>90%) stenosis (n = 5) and to interpreter error (n = 1); no explanation was apparent in the other four. Eleven of 12 false-negative examinations occurred in patients with 70% to 80% internal carotid artery stenosis.Conclusions: In our laboratories, prospective application of the above velocity criteria identified internal carotid artery stenosis of ≥70% with a reasonably high degree of accuracy. Errors occurred when stenoses were borderline and in patients with severe contralateral disease. With suitably modified velocity criteria, color-flow duplex scanning remains the most reliable noninvasive method for identifying symptomatic patients who are candidates for carotid endarterectomy. (J V ASC S URG 1996;23:254-62.)     

Carotid endarterectomy using the eversion technique

Carotid endarterectomy by the eversion technique allows for all of the benefits of conventional endarterectomy but obviates the need for a distal suture line on the smaller internal carotid artery, and thus batching. Carotid artery reanastomosis onto the bifurcation can be quickly and simply performed with almost no risk of closure-related restenosis, given the anastomosis is on the larger of 2 arteries. In our experience of over 3,000 eversion carotid artery endarterectomies, the restenosis rate has been less than 1% judged by rigorous duplex follow-up. In this article, the technique and utility of eversion carotid endarterectomy is discussed.     

Refining the indications for carotid endarterectomy in patients with symptomatic carotid stenosis: A systematic review.

OBJECTIVE: The purpose of this study was to summarize the existing literature on the efficacy of carotid endarterectomy in patients with ipsilateral symptomatic carotid stenosis. METHODS: Database searching, relevance assessment, methodologic quality assessments, and data extraction were all performed in duplicate with prespecified criteria. RESULTS: Twenty-three publications were identified from the North American Symptomatic Carotid Endarterectomy Trial, the European Carotid Surgery Trial, and the Veterans Affairs Cooperative Studies Program. Stenosis was reported as measured in the North American Symptomatic Carotid Endarterectomy Trial. In patients with >70% stenosis, carotid endarterectomy was associated with a pooled relative risk reduction of 48% (95% confidence interval [CI], 27% to 73%) and an absolute risk reduction of 6.7% (95% CI, 3.2% to 10%) for the outcome of death or major disability from stroke. This translates into a number needed to treat of 15 (95% CI, 10 to 31). For patients with 50% to 69% stenosis, the benefit of surgery was less and the confidence intervals were wider. A relative risk reduction of 27% (95% CI, 5% to 44%), an absolute risk reduction of 4.7% (95% CI, 0.8% to 8.7%), and a number needed to treat of 21 (95% CI, 11 to 125) were observed in this group. The patients with the lowest degrees of stenosis (<50%) were harmed by the intervention (number needed to harm, 45). Increasing degree of stenosis, increasing age, male sex, the presence of other medical risk factors, and the presence of hemispheric rather than retinal antecedent events were factors that increased the benefits from surgery. CONCLUSION: Carotid endarterectomy reduced death or major disability from stroke in patients with >50% symptomatic stenosis. To maximize the benefits of surgery, careful preoperative risk assessment and the maintenance of low rates of major perioperative complications are mandatory.     

Carotid endarterectomy in nonagenarians

HYPOTHESIS: The North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial demonstrated that a greater benefit from carotid endarterectomy (CEA) was seen in elderly compared with younger patients. However, no patients older than 89 years were included in either study. We hypothesized that CEA is safe and effective in patients 89 years and older. DESIGN AND SETTING: This is a retrospective review of 3 neurosurgeons' CEA experience with nonagenarian patients. PARTICIPANTS AND INTERVENTIONS: Of our 1800 patients who underwent CEA, 26 were 89 years or older. Twenty-three patients had had cerebral ischemic symptoms (unilateral hemispheric symptoms in 21 and 2 dizzy spells associated with bilateral high-grade stenosis). Cerebral angiography was performed in 3 patients. Twenty-three patients underwent noninvasive imaging. Four patients had bilateral high-grade stenosis and underwent staged bilateral CEA. All procedures were performed after the induction of general anesthesia with electroencephalographic (and, more recently, transcranial Doppler) monitoring and etomidate-induced burst suppression for cerebral protection during cross-clamping. RESULTS: Unusual technical difficulties were frequently noted, including high bifurcations, looping rotated internal carotid arteries, and marked adherence of surrounding soft tissues. In 3 of the 30 procedures, a shunt was used. There were no perioperative cerebral ischemic or cardiac events. The mean hospital stay was 2 days. One patient had a transient vocal cord paresis. Twenty-two patients were alive and well 24 months following the procedure. Four patients died of non-stroke-related causes. CONCLUSIONS: Carotid endarterectomy was successfully performed without perioperative cerebral or cardiac complications in our series of 26 patients 89 years and older undergoing 30 CEAs. Extrapolating from reported results from the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial, we believe CEA should be considered in nonagenarian patients with high-grade symptomatic carotid stenosis who are otherwise well medically. Our recommendations are less certain in the case of asymptomatic disease.     

Carotid endarterectomy versus stenting for stroke prevention: what we have and will learn from Carotid Revascularization Endarterectomy versus Stenting Trial

The Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) has major implications for the future of carotid revascularization and stroke prevention. The purpose of The William Hinter Harridge Lecture was to discuss the history of carotid revascularization before CREST, to delineate the emergence of carotid artery stenting as an alternative to carotid endarterectomy, analyze the key findings in CREST, and describe the next phase of investigation, CREST-2.     

Report on initial experience with transradial access for carotid artery stenting

OBJECTIVE: Carotid artery stenting is emerging as an attractive alternative to surgical endarterectomy for the treatment of carotid artery disease. This study reports our initial experience using the radial artery as access for carotid stenting. METHODS: A retrospective study was performed in which 20 consecutive patients at high risk for carotid endarterectomy underwent carotid stenting with cerebral protection using radial artery access. All procedures were performed in the operating room from March 2006 to December 2006. Seven lesions were symptomatic, and 13 lesions were asymptomatic. Patients were evaluated for development of stroke or transient ischemic attacks, myocardial infarction, access site complications, procedural success, time to patient mobilization, and need for intravenous analgesia. RESULTS: Procedural success was achieved in 18 patients (90%). Intense radial artery vasospasm resulted in one failure, and the second failure occurred in a patient with a left-sided carotid lesion and type I arch. The 30-day incidence of stroke, transient ischemic attacks, myocardial infarction, and death was 0%. Radial artery occlusion only occurred in the one patient because of the development of intense vasospasm during the procedure. One patient had persistent local pain requiring intravenous medication for relief. All patients were mobilized 相似文献   

High-risk carotid endarterectomy: challenges for carotid stent protocols.

BACKGROUND: Carotid angioplasty and stenting is under investigation in clinical trials as an alternative to endarterectomy. Some clinicians have hypothesized that stenting would be applicable for patients at high risk who need carotid revascularization. To further test this hypothesis, we stratified our carotid endarterectomy procedures according to current carotid stent protocols. METHODS: We reviewed our computerized registry and the clinical charts of patients who underwent carotid endarterectomy. Each procedure was categorized as high risk or low risk, according to the following six separate high-risk factors: 1, severe cardiac dysfunction; 2, the requirement for combined coronary and carotid vascularization; 3, severe pulmonary dysfunction; 4, contralateral internal carotid artery occlusion; 5, previous ipsilateral carotid endarterectomy; and 6, anatomically limited access for carotid endarterectomy. Rates of stroke at 30 days, cardiac complications, and death were tabulated. RESULTS: Between January 1, 1998, and December 31, 2000, 415 carotid endarterectomies were performed on 389 patients. Ninety-eight procedures (23.6%) were classified as high risk on the basis of the following factors: 1, severe cardiac dysfunction (n = 30); 2, requirement for combined coronary and carotid revascularization (n = 14); 3, severe pulmonary dysfunction (n = 8); 4, contralateral carotid occlusion (n = 31); 5, previous ipsilateral carotid endarterectomy (n = 25); and 6, anatomically limited access (n = 4). Seven patients had ipsilateral postoperative strokes (1.7%), with two additional patients having contralateral hemispheric strokes. One patient died from exacerbation of congestive heart failure 9 days after undergoing a second carotid endarterectomy. The total stroke and death rate was 2.6% for all the patients. Two of the 98 procedures in the high-risk group were complicated with ipsilateral stroke (2.0%) as compared with six of the 317 low-risk procedures (1.9%; P = 1). Six procedures were complicated with cardiac dysfunction after surgery, including myocardial infarction, congestive heart failure, or the new onset of atrial fibrillation. Three cardiac complications occurred in the low-risk group (1%), and three occurred in the high-risk group (3.1%; P =.15). CONCLUSION: This series shows that patients at high risk can undergo carotid endarterectomy with stroke rates equivalent to the rates of patients at low risk. The cardiac morbidity rate may be increased in the high-risk group. Carotid stenting is unlikely to offer any improvement in stroke risk as compared with carotid endarterectomy, but stenting may reduce non-stroke morbidity rates associated with some high-risk cases.     

A late complication of internal carotid artery stenting

Carotid angioplasty and stenting is gaining in popularity as an alternative to carotid endarterectomy for the treatment of symptomatic critical stenoses of the internal carotid artery. However, the durability of this technique and the incidence of recurrent stenoses has not yet been fully evaluated. It has been reported that mechanical factors may cause deformity of a Palmaz stent, negating the initial benefits of the procedure. We describe successful carotid endarterectomy after distortion of a Strecker balloon-expandable stent.(J Vasc Surg 1998;27:753-5.)     

Carotid artery disease: clinical features and management

The most common cause of ischaemic carotid territory stroke, around 50% of cases, is thromboembolism from stenoses at the origin of the extracranial internal carotid artery (ICA). Embolism is usually preceded by acute changes in plaque morphology, which predisposes towards overlying thrombus formation and embolization. The management of patients with carotid artery disease involves cardiovascular risk factor modification, antiplatelet and statin therapy in everyone. There is grade A, level I evidence that recently symptomatic patients with 50–99% stenoses gain significant benefit from carotid endarterectomy (CEA), despite a small risk of perioperative stroke. Maximum benefit is conferred if CEA is performed as soon as possible after onset of symptoms. Carotid artery stenting (CAS) is an alternative to CEA. Excluding operative risks, 9-year rates of ipsilateral stroke are virtually identical (i.e. CAS is durable), but (at present) 30-day death/stroke is significantly higher after CAS, compared to CEA. The management of patients with asymptomatic carotid stenoses (ACS) remains controversial. The 2018 European Society for Vascular Surgery (ESVS) carotid guidelines advise that patients with a 60–99% ACS who have one or more clinical/imaging features that make them ‘higher risk for stroke’ on best medical therapy (BMT) should be considered for CEA, with the remainder being treated medically.     

Carotid endarterectomy before and after publication of randomized controlled trials

BACKGROUND: In 1991, the European Carotid Surgery Trial (ECST) and the North American Symptomatic Carotid Endarterectomy Trial (NASCET) demonstrated that carotid endarterectomy (CEA), in addition to best medical therapy, significantly reduces ipsilateral stroke in patients with high-grade (70 per cent or more) carotid artery stenosis compared with best medical therapy alone. In 1995, the Asymptomatic Carotid Atherosclerosis Study demonstrated that CEA was of benefit in asymptomatic patients with stenosis greater than 60 per cent. The aim of this paper was to examine how the practice and outcome of CEA have changed since publication of these data. METHODS: A prospectively gathered computerized database comprising 634 consecutive CEAs was studied. Two time intervals were analysed: 1975-1991 inclusive (17 years) and 1 January 1992 to 1 May 1998 (6 years 4 months). RESULTS: Since 1991, there has been a fourfold increase in the number of CEAs performed annually for symptomatic disease. CEA is now performed almost exclusively for high-grade (more than 70 per cent) stenosis. There has been a significant reduction in the total peri-operative neurological event rate (12.5 versus 5.9 per cent, P < 0.05), and the 30-day combined major stroke (Rankin grade 3-5) and mortality rate has fallen to 2.0 per cent. The number of patients who have CEA for asymptomatic disease remains small with 16 of 30 being randomized within the Asymptomatic Carotid Surgery Trial. CONCLUSION: Publication of ECST and NASCET data has been associated with a major increase in the number of CEAs performed for symptomatic disease in this unit. Despite a greater proportion of high-risk patients, the results have improved progressively.     

Management of atherosclerotic carotid artery disease: clinical practice guidelines of the Society for Vascular Surgery

The Society for Vascular Surgery (SVS) appointed a committee of experts to formulate evidence-based clinical guidelines for the management of carotid stenosis. In formulating clinical practice recommendations, the committee used systematic reviews to summarize the best available evidence and the GRADE scheme to grade the strength of recommendations (GRADE 1 for strong recommendations; GRADE 2 for weak recommendations) and rate the quality of evidence (high, moderate, low, and very low quality). In symptomatic and asymptomatic patients with low-grade carotid stenosis (<50% in symptomatic and <60% in asymptomatic patients), we recommend optimal medical therapy rather than revascularization (GRADE 1 recommendation, high quality evidence). In symptomatic patients with moderate to severe carotid stenosis (more than 50%), we recommend carotid endarterectomy plus optimal medical therapy (GRADE 1 recommendation, high quality evidence). In symptomatic patients with moderate to severe carotid stenosis (>/=50%) and high perioperative risk, we suggest carotid artery stenting as a potential alternative to carotid endarterectomy (GRADE 2 recommendation, low quality evidence). In asymptomatic patients with moderate to severe carotid stenosis (>/=60%), we recommend carotid endarterectomy plus medical management as long as the perioperative risk is low (GRADE 1 recommendation, high quality evidence). We recommend against carotid artery stenting for asymptomatic patients with moderate to severe (>/=60%) carotid artery stenosis (GRADE 1 recommendation, low quality evidence). A possible exception includes patients with >/=80% carotid artery stenosis and high anatomic risk for carotid endarterectomy.     

Anatomische Variante mit Ursprung der A.?occipitalis aus der A.?carotis interna

Carotid artery stenosis (CAS) is defined as the narrowing of the carotid artery lumen and is usually caused by calcification-associated constriction through an atherosclerotic process. As a result patients are faced with a main health-threatening danger, namely cerebrovascular accidents (CVAs), which can result in variable clinical presentation depending on the affected cortical areas and potentially lead to severe physical disability or even death. With appropriate indications CAS can be treated operatively by carotid endarterectomy (CEA). In order to minimize the risk of intraoperative complications and CVAs an exact surgical anatomical knowledge is essential. This includes the origin, course and anatomical variations of the internal and external carotid arteries which arise from the common carotid artery at the level of C3-C4. It is worth mentioning that the external carotid artery provides the blood supply to different cervical structures, whereas the internal carotid artery branches first after entering the skull. A detailed literature search revealed that there are only a few articles available describing the possible anatomical anomalies of the carotid arteries. This article presents the case of a 69-year-old patient with noticeable vascular variations, documented and observed during a CEA operation for symptomatic CAS and the medical relevance of these anatomical variations is discussed.     

Noninvasive analysis of conjunctival microcirculation during carotid artery surgery reveals microvascular evidence of collateral compensation and stenosis-dependent adaptation

OBJECTIVE: Hemodynamically relevant internal carotid artery (ICA) stenosis is a major cause of ischemic stroke. Despite its long-term benefit, carotid endarterectomy may also be associated with severe neurologic deficits. Intraoperative and early recognition of ischemia in the region of the ICA may reduce this risk. To date, direct imaging and quantitative analysis of microvascular structures and function in the human ICA region have not been possible. We purposed to visualize and quantify ischemia/reperfusion-induced microcirculatory changes in the terminal vascular bed of the ICA in patients undergoing unilateral ICA endarterectomy. METHODS: Sequential analysis of the ipsilateral and contralateral conjunctival microcirculation was performed with orthogonal polarized spectral imaging in 33 patients undergoing unilateral ICA endarterectomy because of moderate or severe ICA stenosis (North American Symptomatic Carotid Endarterectomy Trial score, 75% +/- 13%), before clamping the ICA (baseline), during clamping of the external carotid artery and ICA, during reperfusion of the ICA (intraluminal shunt), during the second clamping of the ICA (shunt removal), after declamping (reperfusion) of the external carotid artery and ICA, and 15 to 20 minutes after the second ICA reperfusion. RESULTS: During ICA clamping for shunt placement, ipsilateral and contralateral conjunctival capillary perfusion was significantly decreased, but it was completely restored after reperfusion with carotid shunting. Reclamping of the ICA for shunt removal caused microvascular dysfunction, which was significantly less pronounced than that observed during the first clamping. The individual degree of ICA stenosis was inversely correlated with the ipsilateral and contralateral decrease in conjunctival functional capillary density during the first ICA clamping. CONCLUSIONS: These results suggest adaptive mechanisms of capillary perfusion with increasing stenosis and development of collateral compensatory circulation in the vascular region of the human ICA. Conjunctival orthogonal polarized spectral imaging during unilateral ICA reconstruction enables continuous noninvasive analysis of bilateral conjunctival microcirculation in the terminal region of the ICA and enables monitoring for efficient carotid shunt perfusion during and after endarterectomy.