Hemodynamic Effects of Carotid Endarterectomy by Magnetic Resonance Flow Quantification

Abstract

Background and Purpose Blood flow can be evaluated noninvasively using magnetic resonance phase-contrast flow quantification. The purpose of this prospective study was to assess the feasibility of this method and to evaluate the hemodynamic effects of carotid endarterectomy. Methods Volumetric flow rates and peak systolic velocities of the internal and common carotid and the vertebral arteries were measured by magnetic resonance flow quantification. Sixteen patients undergoing 18 endarterectomies had complete flow data recorded preoperatively and 3 days after surgery. Results The inverse correlation between the angiographic stenosis degree and the preoperative flow rate in the corresponding internal carotid artery was highly significant ( r =−.69, P <.001). After endarterectomy, the mean flow in the ipsilateral internal carotid artery improved from 143 to 233 mL/min ( P <.001). The mean peak systolic velocity increased from 23 to 37 cm/s ( P <.001). No significant changes were seen in the contralateral carotid or the vertebral arteries. The mean total blood flow improved by 81 mL/min ( P =.08). In the severely stenosed bifurcations (70% to 99%, n=11), the flow rate improved by 106 mL/min and in the moderately (30% to 69%, n=4) or mildly (<30%, n=3) stenosed bifurcations by 63 mL/min. If the contralateral carotid artery was occluded or severely stenosed, the improvement was 164 mL/min. Conclusions Magnetic resonance flow quantification provides a useful tool for the follow-up of the hemodynamic effects of carotid endarterectomy. Our results indicate that surgery is followed by a significant increase of blood flow in the ipsilateral carotid artery and that there appear to be differences in flow increase between subgroups of patients with different degrees of stenosis.