Carotid artery velocity patterns in normal and stenotic vessels.

Duplex scanning provides real time B-mode images of the carotid bifurcation vessels along with a single gate pulsed Doppler flow velocity detector. By using the B-mode output of the duplex system to measure the Doppler angle and spectrum analysis to measure the frequency content of the Doppler signal, instantaneous flow velocity can be calculated. Mean velocity at peak systole was calculated retrospectively in 68 common (CCA) and internal (ICA) carotid arteries of 39 patients who had undergone prior angiography and prospectively in 30 arteries of 15 healthy young controls. The ratio of mean peak ICA velocity to mean peak CCA velocity at systole (VICA/VCCA) was below 0.8 in all 36 normal arteries and above 1.5 in all 21 high-grade stenoses of 60% or greater diameter reduction. Sixty-one percent of 41 vessels with less than 10 to 55% diameter reduction had a velocity ratio between 0.8 and 1.5. Only 10% of all ICA's with any stenotic lesion were incorrectly classified as normal. VICA/VCCA appears to be an accurate indicator of the degree of ICA stenosis.