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Identifying Risk Factors for Stroke in Asymptomatic Carotid Stenosis
The use of carotid endarterectomy (CEA) in asymptomatic carotid-artery stenosis is controversial. Although a large, randomized, prospective study of patients with severe symptomatic stenosis showed statistically significant benefit with CEA, critics argue that cost-benefit ratios are too high. The North American Symptomatic Carotid Endarterectomy Trial (NASCET) found that approximately 20 percent of strokes ipsilateral to symptomatic carotid stenosis had a lacunar or cardioembolic cause. In this analysis of NASCET data, researchers reasoned that if a similar or higher percentage of such strokes occurred with asymptomatic carotid stenosis, then indications for elective CEA would be further diminished.
Among 216 patients who had asymptomatic carotid stenoses of 60 to 90 percent, the 5-year risk for first stroke was 16.2 percent. With 75 to 94 percent stenosis, the 5-year risk was 18.5 percent. Nearly half (45 percent) of these strokes were attributable to either lacunae or cardioembolism; 55 percent were large-artery strokes attributable to the carotid stenoses.
Comment: This report supports a cautious approach when considering CEA for asymptomatic carotid stenosis. The findings regarding the subjects with 75 to 94 percent stenoses suggest that it is possible to identify an at-risk group in this population that can benefit from CEA. The risk factors for atherothrombosis and thromboembolic stroke due to carotid stenosis are multifactorial and include the character and composition of atheromas; their progression, inflammatory status, and multiplicity; and factors such as diabetes mellitus and silent brain infarcts. If it becomes possible to more precisely identify the nearly 10 percent of subjects with 60 to 94 percent stenoses who will suffer large-artery strokes within 5 years, outcomes results from CEA that are as favorable as those from NASCET may follow. Two ongoing studies should provide answers to these questions in the next several years.
FM Yatsu
Frank M. Yatsu, MD, is Roy M. and Phyllis Gough Huffington Chair in Neurology, Professor of Neurology and Chairman Emeritus, Department of Neurology, University of Texas-Houston Medical School, Houston, TX.
Published in Journal Watch Neurology August 9, 2000
Citation(s):
Inzitari D et al. The causes and risk of stroke in patients with asymptomatic internal-carotid-artery stenosis. N Engl J Med 2000 Jun 08 342
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