Stroke Risk Population studies<4,5> have reported that patients with asymptomatic neck bruits are at increased risk for stroke: slightly more than 2% per year in the Evans County study (7.5 fold increase for men and 1 .6 fold increase for women) and in the Framingham study the two year incidence of stroke was 3% in men and 4% in women, a 2 to 3 fold increased risk. In these studies, the presence of a bruit did not predict the type (thromboembolic, cardioembolic, lacunar or hemorrhagic) or the hemispheric location of the stroke. Most of the strokes either occurred in a different vascular territory or their presumed cause was unrelated to the carotid stenosis itself. In more recent years, non-invasive imaging (ultrasonography), has shown that the risk of neurological events is directly correlated with the severity of carotid stenosis (Figure 1 ).<6- 1 2> It has also been observed that rapid progression of carotid bifurcation plaque may herald a significant risk of stroke.<6, 1 3> Correlation with plaque morphology such as ulceration or intraplaque hemorrhage as well as correlation with other risk factors is less well defined. In a Canadian prospective referral population study of 696 patients with asymptomatic bruits followed on average for 3.5 years,<7> the annual stroke rate was 1 .3% in patients with equal or less than 50% stenosis and 3.3% in those with greater than 50% stenosis. Ipsilateral stroke rate was 2.5% in patients with >50% stenosis. Other prospective studies of large populations of patients with asymptomatic bruits have shown similar results;<6,8- 1 0, 1 3> the overall risk of stroke is 1 to 2% annually, that is approximately three times the likelihood of having an ischemic stroke in an age- and sex-matched population without bruits.< 11 >
Cardiac Risk (Myocardial Infarction and Cardiac Death) In the study by Norris and colleagues,<7> the annual rate of cardiac ischemic events and cardiac death was 9.9% in those with 50% stenosis and 1 4.8% in those with >50% stenosis. Similarly, in most surveys on asymptomatic carotid bruit or stenosis the major risk is cardiac, not cerebrovascular.<4,5,7> However this depends on the type of population studied and their initial cardiac status; in another ongoing prospective study,< 1 0> in which patients with heart conditions requiring the obligatory use of aspirin were excluded, neurological events were more frequent among patients with asymptomatic bruits.
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