Natural History of Carotid Atherosclerosis
Stroke is the third leading cause of death in the United States, constituting approximately 700 000 cases each year, of which about 500 000 are first attacks and 200 000 recurrent attacks. Ischemic stroke accounts for the largest number of new strokes (88%) followed by intracerebral hemorrhage (9%) and subarachnoid hemorrhage (3%). 1 Atherosclerotic plaque at the carotid bifurcation is the underlying cause of the majority of ischemic strokes, and the degree of carotid stenosis is strongly associated with stroke risk in symptomatic patients. 2 However, the degree of stenosis does not always predict those patients who will develop vulnerable lesions, as low-grade lesions may also result in cerebrovascular events. Pathologic studies comparing symptomatic and asymptomatic carotid plaques have demonstrated that specific plaque characteristics are associated with ischemic brain injury, and the mechanisms underlying plaque instability in the carotid circulation are similar to those in the coronary circulation. 3,4 In fact, plaque morphology is considered an additional independent risk factor for cerebral infarction.