[A comparative study of the Doppler methods for evaluation of the degree of carotid artery stenosis. Continuous, pulsed, color Doppler]

Abstract

Objective: Compare various Doppler methods for the quantification of the degree of stenosis on 85 patients.

Method: the following parameters were measured: maximal velocity (Vmax) inside the stenosis (PW), grades of spectral disturbances at the outlet of the stenosis (PW-CW), index of spectral disturbance (STI) at the outlet of the stenosis (PW-CW), ratio of velocities I(IC/CC) in internal and common carotid (PW), ratio of vessel cross section and residual lumen area (% STEN) by color Doppler. The reference method was the Grades of spectral disturbance and the index of stenosis measured post stenosis. (Method validated against angiography and pieces of endarterectomy.) The following comparisons were done; grades and STI by CW against grades and STI by PW, Vmax (PW) against grade and STI, % STEN (color) against grade and STI, % STEN (color) against Vmax (PW), I(IC/CC) (PW) against grade and STI, I(IC/CC) (PW) against Vmax.

Conclusion: (a) grades or stenosis index : showed the best reproductibility; (b) a high correlation was found between the grades or stenosis index post stenosis measured by CW or PW; (c) Vmax was not proportional to the stenosis degree and showed large fluctuations for the same stenosis degree; (d) the I(IC/CC) showed large fluctuations for the same stenosis degree, the correlation was poor for this velocity ratio. Both Vmax and I(IC/CC) allow to detect only 2 groups of stenosis > 75% or > 90% in area; (e) color doppler over-estimate stenosis degree by approximately 20% but was more accurate and reproducible than Vmax. An appropriate procedure was designed to avoid this over estimation.