Detection of carotid stenosis. From NASCET results to clinical practice

Results from large multicenter studies have shown that carotid endarterectomy, performed with low perioperative morbidity and mortality, is beneficial for patients with symptomatic carotid stenosis > or = 70% as calculated according to strict angiographic criteria. To apply these results in clinical practice, individual institutions should determine whether locally implemented duplex ultrasonography adequately identifies patients with > or = 70% stenosis and whether the degree of stenosis reported by local angiographers correlates with strict angiographic measurements.

We compared estimates of carotid stenosis obtained by duplex ultrasonography and the radiologists' reports from conventional cerebral angiography with each other and with results obtained using North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria.

One hundred seventy-one vessels were available for review. In 155 (91%) of the cases, the reports from the ultrasound and angiogram were in agreement with regard to whether the stenosis was > or = 70% or < 70%. In 11 of the 16 cases where there was a disparity between the studies, the ultrasound was in closer agreement with measurements obtained using NASCET criteria. Nine of the angiography reports overestimated the degree of stenosis compared with NASCET measurements; twice angiography underestimated the stenosis. Twice the ultrasound underestimated the stenosis, and three times it overestimated the stenosis.

Duplex ultrasonography was highly sensitive for detecting significant carotid stenosis at our institution; however, angiography reports often graded the degree of stenosis to be more severe than measurements obtained using NASCET criteria. Institutions that evaluate patients for carotid endarterectomy should investigate the correlation between their ultrasound and angiographic studies so that the results of carotid endarterectomy trials can be accurately applied.