[Flow reversal in the carotid bifurcation. Detection using color-coded Doppler sonography]

Pulsatile blood flow within the normal carotid sinus involves at least two distinct components. Beside the laminar antegrade flow, there is a boundary layer separation zone in the posterolateral aspect with transient flow reversal. This flow reversal is well known from in vitro studies. It is now possible to document these flow velocity components using color-coded Doppler sonography. It is hypothesized that if flow separation is detected, this is indicative of a normal condition of the carotid bifurcation. When atherosclerosis develops, it involves preferentially the posterolateral bulb region, obliterating the normal configuration of the sinus with consequent loss of the flow separation. Therefore, loss of flow reversal should be indicative of atherosclerosis. We have studied this flow pattern retrospectively in 156 patients (312 arteries). In 4 patients no flow reversal could be detected although no atheromatous lesions could be found at the bifurcation, but in these cases there was no bulb formation in the common carotid artery or in the internal carotid artery. On the other hand, flow reversal was demonstrable in several pathological conditions within the carotid bifurcation. These included plaque formation after the bifurcation in 7 patients, internal carotid artery occlusion at the origin in 12, common carotid artery occlusion despite a patent bifurcation in 4, and marked dilatation of the lumen forming a pseudobulb following disocclusion of the carotid artery in 11 patients.