Vascular risks of asymptomatic carotid stenosis.

We sought to determine the risks of stroke, myocardial ischemia, and vascular death in patients with asymptomatic carotid stenosis. Six hundred ninety-six patients with asymptomatic carotid stenosis referred to the Doppler laboratory were followed prospectively for a mean time of 41 months. These patients were studied both clinically and by carotid Doppler ultrasound, including evaluation of the effect of stroke risk factors. Transient ischemic attacks occurred in 75 patients and stroke in 29, while 132 had ischemic cardiac events. Five patients died from stroke and 59 from cardiac causes. Annual stroke rate was 1.3% in patients with carotid stenosis less than or equal to 75% and 3.3% in those with stenosis greater than 75%. Ipsilateral stroke rate was 2.5% in patients with greater than 75% carotid stenosis. Annual cardiac event rate was 8.3% and death rate 6.5% in patients with severe carotid stenosis. With carotid stenosis less than or equal to 75%, the stroke rate is negligible (1.3% annually) whereas the combined risk of cardiac ischemia and vascular death is as high as 9.9%. With stenosis greater than 75%, combined transient ischemic attack and stroke rate is 10.5% per year, with 75% of events ipsilateral to the stenosed artery.