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Strokes In Patients With Narrowed Carotid Arteries May Be Due To Other Causes

CHICAGO, IL -- March 14, 2000 -- Strokes occurring in patients with severe narrowing of the carotid artery are commonly due to other causes, according to an article in the March 15 issue of The Journal of the American Medical Association (JAMA).

Henry J.M. Barnett, M.D., from the John P. Robarts Research Institute in London, Ontario, and colleagues analyzed data from 2,885 patients with symptomatic internal carotid artery stenosis (narrowing of one of the main arteries that supplies blood to the brain). The patients participated in the North American Symptomatic Carotid Endarterectomy Trial (NASCET), in which they were randomly assigned to receive either an endarterectomy (an operation that removes material [such as atherosclerotic deposits] and part of the lining of an artery to relieve blockages and increase blood flow) or medical management for the treatment of carotid artery stenosis.

The researchers followed the patients for an average of 5 years and categorized subsequent strokes by three possible causes: large-artery (carotid) blockage, cerebral lacunar (small areas of damage to the brain caused by blockages in smaller branches of arteries that supply blood to the brain), or cardioembolic (blockage caused by a clot traveling from the heart). During the follow-up period, 749 patients had 1,039 strokes. The overall risk of first stroke after entry into the study was calculated as 2.6 percent for cardioembolic, 6.9 percent for lacunar, and 19.7 percent for large-artery.

The researchers found that for those patients with symptoms with less than 70 percent stenosis, approximately 35 percent of the strokes were unrelated to narrowing of the carotid artery. For those patients without symptoms and with 60 to 99 percent stenosis, approximately 50 percent of the strokes were unrelated to narrowing of the carotid artery. "The cause of subsequent strokes in similar types of patients should be considered when making treatment decisions particular involving carotid endarterectomy for patients with asymptomatic carotid stenosis, since lacunar and cardioembolic strokes cannot be prevented by endarterectomy."

"The results of this study demonstrate that even in the presence of large-artery lesions, strokes arise from a variety of causes," the researchers write. "Expectations of benefit from endarterectomy in symptomatic patients with moderate disease or in asymptomatic subjects must consider the evidence that a large number of future strokes will not be related to the carotid artery lesion," the authors note.

"The risk of stroke expected from the large-artery lesion is only part of the story. In patients with carotid stenosis suspected of causing ischemic events, risk factors must be modified," the researchers write. "Before deciding on the final treatment strategy, consideration should be given to investigations to identify other potential causes of stroke." (JAMA. 2000;283:1429-1436)

Related Link: The Journal of the American Medical Association (JAMA).

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