Noninvasive assessment of stroke risk in asymptomatic and nonhemispheric patients with suspected carotid disease. Five-year follow-up of 294 unoperated and 81 operated patients.

Based on the assumption that greater than or equal to 50% stenosis of the internal carotid artery increases stroke risk, noninvasive tests are being used to screen patients for prophylactic carotid endarterectomy. To assess the validity of this concept, 104 asymptomatic and 190 nonhemispheric patients referred for cerebrovascular tests were reviewed after 5 years. Carotid stenosis greater than or equal to 50% predicted a 15% stroke incidence at 2 years compared to a 3% incidence with 1-49% stenosis (p less than or equal to 0.05). Five-year cumulative stroke incidence was 21% with greater than 50% stenosis, 14% with 1-49% stenosis (NS), and 9% with 0% stenosis (p less than 0.05). Stenosis greater than or equal to 50% predicted increased cardiac mortality (p less than 0.025). Hypertensive patients, greater than 70 years, with greater than or equal to 50% stenosis had a 37% incidence of stroke; normotensive patients, less than 70 years, with or without stenosis, had few strokes. In patients with greater than or equal to 50% disease, surgery reduced the 5-year stroke rate from 21 to 8% (p less than 0.05), mitigated the effects of age and hypertension, and improved survival. Noninvasive test results must be considered in conjunction with age and hypertension in predicting stroke risk.