Clinical outcome in patients with mild and moderate carotid artery stenosis

The natural history of incidentally discovered asymptomatic mild (< 50%) and moderate (50% to 79%) carotid artery stenosis is not known. The carotid artery duplex ultrasound surveillance program at the University of Washington Department of Vascular Surgery has serially evaluated patients with carotid artery disease for more than a decade and provides data on the progress and management of this disease.

Patients with asymptomatic carotid artery bruits who had carotid artery disease causing less than 80% lumen diameter narrowing at their initial visit were identified. At each return visit (6 months, 1 year, and annually thereafter) a clinical questionnaire was completed, and bilateral carotid artery duplex sonography was performed.

Two hundred thirty-two patients (136 men and 96 women) were monitored for up to 10 years with sufficient data for a 7-year life-table analysis. Progression in the degree of stenosis was noted in 23% of patients during follow-up, and nearly half of these progressed to severe stenosis (80% to 99%) or occlusion. The risk of progression to severe stenosis and occlusion was significantly greater for those patients with moderate initial stenosis than mild initial stenosis (p < 0.01). The cumulative stroke risk for patients with mild initial stenosis (6%) was half of that for patients with moderate initial stenosis (11%) after 7 years. Carotid endarterectomy was performed in 27 patients during follow-up; in 13 the indication was an event ipsilateral to the stenosis, and in 14 there was asymptomatic progression to high-grade stenosis.

Regular monitoring of mild to moderate carotid artery stenosis shows how these lesions progress over time, permitting a realistic appraisal of their potential for producing an ischemic cerebrovascular event.