Duplex ultrasonography criteria for internal carotid stenosis of more than 70% diameter: angiographic correlation and receiver operating characteristic curve analysis.

To determine duplex ultrasonography criteria for detecting stenosis of 70% or more in the internal carotid artery, to be used as a means of selecting candidates suitable for endarterectomy (a procedure suggested by the North American Symptomatic Carotid Endarterectomy Trial as appropriate for symptomatic patients with 70% to 99% stenosis).Between Jan. 1, 1991, and Apr. 30, 1993, 120 patients underwent internal carotid angiography at a tertiary care hospital for transient ischemic attacks, asymptomatic bruits or preoperative assessment. Of these, 83 also underwent duplex ultrasonography within 31 days of angiography. The angiographic and sonographic studies for 145 vessels in 75 of the patients (50 men and 25 women) were suitable for further study. The sonographic criteria were selected on the basis of a receiver operating characteristic curve relating peak systolic velocity of the internal carotid artery to the degree of stenosis determined angiographically.Angiography indicated that 33 of the vessels had stenosis of 70% or more and that 12 additional vessels were completely occluded. The combined sonographic criteria of peak systolic velocity of less than 40 cm/s or 175 cm/s or more yielded 91% sensitivity and 60% specificity for angiographically determined stenosis of 70% or more.In this patient population the combined criteria of peak systolic velocity of less than 40 cm/s or 175 cm/s or more were highly sensitive and reasonably specific for internal carotid artery stenosis of 70% or more.