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

Background/purpose. 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 greater than or equal to60% carotid stenosis (ACS). This study analyzes the natural history of 60% to 69% ACS according to ultrasonic plaque morphology and its implication on treatment. Patient population and methods: 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 greater than or equal to70% stenosis or became symptomatic. Results. 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 greater than or equal to70% stenosis was also higher in group A than in group B: 25.3% versus 6.6% (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 greater than or equal to70% ACS) versus 13 (5.7%) in group B (five for stroke, seven for TIA, and one for greater than or equal to70% ACS; P = .0001; OR, 6.2). Conclusion: Patients with 60% to 69% ACS with heterogeneous plaque had a higher incidence rate of late stroke, TIA, and progression to greater than or equal to70% stenosis than patients with homogeneous plaque. Prophylactic CEA for 60% to 69% ACS may be justified if associated with heterogeneous plaque.