Measurement of vessel stenosis by using ultrasonography or angiography remains the principal method for determining the severity of carotid atherosclerosis and the need for endarterectomy. The ipsilateral stroke rate, however--even in patients with severely stenotic vessels--is relatively low, which suggests that the amount of luminal narrowing may not represent the optimal means of assessing clinical risk. As a result, some patients may undergo unnecessary surgery. Improved imaging techniques are, therefore, needed to enable reliable identification of high-risk plaques that lead to cerebrovascular events. High-spatial-resolution magnetic resonance (MR) imaging has been described as one promising modality for this purpose, because the technique allows direct visualization of diseased vessel wall and can be used to characterize the morphology of individual atherosclerotic carotid plaques. The purpose of this report is to review the current state of carotid plaque MR imaging and the use of carotid MR to evaluate plaque morphology and composition.

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Background-Current imaging modalities, such as contrast angiography, accurately determine the degree of luminal narrowing but provide no direct information on plaque size. Magnetic resonance imaging (MRI), however, has potential for noninvasively determining arterial wall area (WA). This study was conducted to determine the accuracy of in vivo MRI for measuring the cross-sectional maximum wall area (MaxWA) of atherosclerotic carotid arteries in a group of patients undergoing carotid endarterectomy. Methods and Results-Fourteen patients scheduled for carotid endarterectomy underwent preoperative carotid MRI using a custom-made phased-array coil. The plaques were excised en bloc and scanned using similar imaging parameters. MaxWA measurements from the ex vivo MRI were used as the reference standard and compared with MaxWA measurements from the corresponding in vivo MR study. Agreement between the in vivo and ex vivo measurement was analyzed using the Bland-Altman method.

Conclusion: After carotid endarterectomy (CEA) or carotid artery stenting (CAS), restenosis and occlusion of the internal carotid artery are infrequent and occur at the same rate for the two procedures.Summary: In the CREST trial, the frequency of the composite end point of myocardial infarction, stroke, or death during the periprocedural period, or ipsilateral stroke thereafter, occurred equally with CEA and CAS. A secondary analysis indicated that stroke was more frequent after CAS and myocardial infarction, primarily enzyme leaks, was more frequent after CEA. A secondary predescribed goal of CREST was to determine the composite end point of restenosis or occlusion after the two procedures. The original prespecified times for analysis were 6 and 12 months. However, the investigators agreed that analysis at 24 months would be more informative, and thus, this article reports 2-year anatomic durability of CAS and CEA. This was a per protocol analysis. CREST enrolled patients with stenosis of the internal carotid artery who were asymptomatic or who had a transient ischemic attack, amaurosis fugax, or a minor stroke. The study involved 117 centers in the United States and Canada, and enrollment occurred between December 21, 2000, and January 18, 2008. Restenosis and occlusion were assessed by duplex ultrasound imaging at 1, 6, 12, 24, and 48 months. Restenosis was defined as a reduction in diameter of the target artery of at least 70%. A peak systolic velocity of 300 cm/s was used as an indicator of 70% stenosis. All studies were done in CREST-certified laboratories and were interpreted at an ultrasound core laboratory at the University of Washington. Frequency of restenosis was calculated by Kaplan-Meier survival estimates and was compared at 2 years. Proportional hazard models were used to estimate the association between baseline characteristics and risk of restenosis. In the CREST study, 2191 patients received their assigned treatment #30 days of randomization and had eligible ultrasound images (1086 who had CAS, 1,105 who had CEA). In 2 years, 58 patients treated with CAS (Kaplan-Meier rate, 6.0%) and 62 patients who had CEA (6.3%) had restenosis or occlusion (hazard ratio, 0.9; 95% confidence interval, 0.63-1.29; P ¼ .58). Independent predictors of restenosis or occlusion after both procedures (hazard ratio, 95% confidence interval) were female sex (1.79, 1.25-2.56), dyslipidemia (2.07, 1.01-4.26), and diabetes (2.31, 1.61-3.31). Smoking was a risk factor for an increased rate of restenosis after CEA (2.26, 1.34-3.77) but not after CAS (0.77, 0.41-1.42). Defining restenosis as a peak systolic velocity of 230, 350, or 400 cm/s did not result in a difference in the frequency of restenosis between CAS and CEA. Using a restenosis definition of 210 cm/s indicated increased restenosis after CAS (14.8%) vs CEA (10.5%). Participants who had restenosis or occlusion at 2 years with adjustment for age, sex, and symptomatic status had an increased risk for ipsilateral stroke during the follow-up period (hazard ratio, 4.37...

SUMMARY A prospective study was initiated in January 1980 to follow with Duplex scanning a consecutive series of 167 asymptomatic patients with cervical bruits. Patients were seen at six month intervals for the first year and yearly thereafter. Based on previously validated criteria, disease at the carotid bifurcation was classified into 6 categories: (1) Normal, (2) 1-15% diameter reduction, (3) 16-^19%, (4) 50-79%, (5) 80-99%, and (6) occlusion. Patients were evaluated to assess: (1) the occurrence of new neurological symptoms, (2) the stability of the lesions at the carotid bifurcation, and (3) the possible role of risk indicators on disease changes.During follow-up, ten patients became symptomatic (6 with TIA's and 4 with stroke). The development of symptoms was accompanied by disease progression in 8 patients. By life table analysis, the annual rate occurrence of symptoms was 4%. The mean annual rate of disease progression to a greater than 50% stenosis was 8%. When progression in all categories was considered, 60% of the sides showed some disease aggravation. The presence of or progression to a greater than 80% stenosis was highly correlated (p = 0.00001) with either the development of a total occlusion of the internal carotid artery or new symptoms.The major risk factors associated with disease progression were cigarette smoking, diabetes mellitus, and age. Those patients under 65 years of age were most likely to show progression.Despite high rates of disease progression, this study further supports the contention that it is prudent to follow a conservative course in the management of asymptomatic patients presenting with a cervical bruit. Surgical treatment can be delayed until the appearance of TIA's or progression of disease to a greater than 80% stenosis.Stroke Vol 15, No 4, 1984

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Background In the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST), the composite primary endpoint of stroke, myocardial infarction, or death during the periprocedural period or ipsilateral stroke thereafter did not differ between carotid artery stenting and carotid endarterectomy for symptomatic or asymptomatic carotid stenosis. A secondary aim of this randomised trial was to compare the composite endpoint of restenosis or occlusion. Methods Patients with stenosis of the carotid artery who were asymptomatic or had had a transient ischaemic attack, amaurosis fugax, or a minor stroke were eligible for CREST and were enrolled at 117 clinical centres in the USA and Canada between Dec 21, 2000, and July 18, 2008. In this secondary analysis, the main endpoint was a composite of restenosis or occlusion at 2 years. Restenosis and occlusion were assessed by duplex ultrasonography at 1, 6, 12, 24, and 48 months and were defined as a reduction in diameter of the target artery of at least 70%, diagnosed by a peak systolic velocity of at least 3·0 m/s. Studies were done in CREST-certified laboratories and interpreted at the Ultrasound Core Laboratory (University of Washington). The frequency of restenosis was calculated by Kaplan-Meier survival estimates and was compared during a 2-year follow-up period. We used proportional hazards models to assess the association between baseline characteristics and risk of restenosis. Analyses were per protocol. CREST is registered with ClinicalTrials.gov, number NCT00004732. Findings 2191 patients received their assigned treatment within 30 days of randomisation and had eligible ultrasonography (1086 who had carotid artery stenting, 1105 who had carotid endarterectomy). In 2 years, 58 patients who underwent carotid artery stenting (Kaplan-Meier rate 6·0%) and 62 who had carotid endarterectomy (6·3%) had restenosis or occlusion (hazard ratio [HR] 0·90, 95% CI 0·63–1·29; p=0·58). Female sex (1·79, 1·25–2·56), diabetes (2·31, 1·61–3·31), and dyslipidaemia (2·07, 1·01–4·26) were independent predictors of restenosis or occlusion after the two procedures. Smoking predicted an increased rate of restenosis after carotid endarterectomy (2·26, 1·34–3·77) but not after carotid artery stenting (0·77, 0·41–1·42). Interpretation Restenosis and occlusion were infrequent and rates were similar up to 2 years after carotid endarterectomy and carotid artery stenting. Subsets of patients could benefit from early and frequent monitoring after revascularisation. Funding National Institute of Neurological Disorders and Stroke and Abbott Vascular Solutions

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