Prospective controlled study of the natural history of asymptomatic 60% to 69% carotid stenosis according to ultrasonic plaque morphology.

Abstract

In spite of the conclusions of the Asymptomatic Carotid Atherosclerosis Study, some clinicians are still reluctant to recommend carotid endarterectomy (CEA) for patients with asymptomatic > or = 60% carotid stenosis (ACS). This study analyzes the natural history of 60% to 69% ACS according to ultrasonic plaque morphology and its implication on treatment. During a 2-year period, patients with 60% to 69% ACS entered into a protocol of carotid duplex scan surveillance/clinical examination every 6 months. The ultrasonic plaque morphology was classified as heterogeneous (group A, n = 162) or homogeneous (group B, n = 229) with HDI 3000/HDI 5000 systems (Advanced Technology Laboratories, Bothwell, Wash). CEA was done if lesion progressed to > or = 70% stenosis or became symptomatic. Three hundred eighty-two patients (391 arteries) were followed for a mean interval of 37 months. The clinical/demographic characteristics were similar for both groups. The incidence rate of future ipsilateral strokes was significantly higher in group A than in group B: 13.6% versus 3.1% (P =.0001; odds ratio [OR], 5). Similarly, the incidence rate of all neurologic events (stroke or transient ischemic attack [TIA]) was higher in group A than in group B: 27.8% versus 6.6% (P =.0001; OR, 5.5). Progression to > or = 70% stenosis was also higher in group A than in group B: 25.3% versus 6.1% (P =.0001; OR, 5.2). Forty-four late CEAs (27.2%) were done in group A (16 for stroke, 21 for TIA, and seven for > or = 70% ACS) versus 13 (5.7%) in group B (five for stroke, seven for TIA, and one for > or = 70% ACS; P =.0001; OR, 6.2). Patients with 60% to 69% ACS with heterogeneous plaque had a higher incidence rate of late stroke, TIA, and progression to > or = 70% stenosis than patients with homogeneous plaque. Prophylactic CEA for 60% to 69% ACS may be justified if associated with heterogeneous plaque.