Causes and severity of ischemic stroke in patients with internal carotid artery stenosis

Context Therapeutic trials generally have not distinguished outcomes of str oke according to cause. Objective To determine whether stroke and subsequent disability was of larg e-artery, lacunar, or cardioembolic origin in patients with different degre es of symptomatic and asymptomatic carotid stenosis. Design Observational study of prospective data collected from the North Ame rican Symptomatic Carotid Endarterectomy Trial between 1987 and 1997. Setting and Patients A total of 2885 patients from 106 sites in the United States and abroad (median age, 67 years; 70% male) who had symptomatic inte rnal carotid artery stenosis. Main Outcome Measure Risk of stroke from each of the 3 causes at 5 years by territory and degree of stenosis. Results During an average follow-up of 5 years, 749 patients had 1039 strok es, including 112 of cardioembolic, 211 of lacunar, 698 of large-artery, 17 of primary intracerebral hemorrhage, and 1 of subarachnoid hemorrhage orig in. The 5-year risk of first stroke after entry into the trial in any terri tory was 2.6% of cardioembolic cause, 6.9% of lacunar cause, and 19.7% of l arge-artery cause. The proportion of cardioembolic strokes in the territory of the symptomatic artery was 12.0% and 6.9% in 60% to 69% and 70% to 99% arterial stenosis, respectively; large-artery strokes predominated (78.4%) at 70% to 99% arterial stenosis. With 70% to 99% arterial stenosis, the pro portion of strokes of cardioembolic and lacunar origin was 43.5% and 21.6% in asymptomatic and symptomatic arteries, respectively. A total of 67.6% of cardioembolic, 16.7% of lacunar, and 33.0% of large-artery strokes in the territory of the asymptomatic artery were disabling or fatal. Conclusions Our data suggest that approximately 20% and 45% of strokes in t he territory of symptomatic and asymptomatic carotid arteries with 70% to 9 9% stenosis, respectively, are unrelated to carotid stenosis. The cause of subsequent strokes in similar types of patients should be considered when m aking treatment decisions involving carotid endarterectomy for patients wit h asymptomatic carotid stenosis, since lacunar and cardioembolic strokes ca nnot be prevented by endarterectomy.