Continuous-wave Doppler in the intraoperative assessment of carotid endarterectomy.

A sterile 8.5 MHz continuous-wave Doppler probe was used intraoperatively to evaluate the technical result of 229 consecutive carotid endarterectomies. Primary areas of evaluation included the proximal point of plaque transection and the internal and external carotid arteries at and distal to the termination of the endarterectomy. Subjective interpretation was made of the Doppler audio signal. Signs associated with inadequate technical results were a high-frequency signal indicative of luminal narrowing with a reduction in frequency distal to the area of stenosis, absence of a Doppler signal indicating occlusion, and a weak monophasic flow signal indicating poor distal perfusion. Abnormal signals were identified in 10 internal carotid arteries (4.3%) which prompted intraoperative angiography in eight and immediate reopening of the artery in an additional two. Significant lesions were identified in seven arteries (70%). Twenty external carotid lesions (8.7%) were detected by Doppler and in 19 cases (95%) a significant stenosis or obstruction was found when the vessel was reopened. Auscultation of a continuous-wave Doppler signal with a sterile probe at operation appears to have a high positive predictive value in the identification of both internal and external carotid stenoses. It is rapid, safe, relatively inexpensive, and avoids the problems associated with routine intraoperative angiography.