CAROTID DUPLEX OVERESTIMATION OF STENOSIS DUE TO SEVERE CONTRALATERALDISEASE

BACKGROUND: In the quest to use carotid duplex to assess carotid occlu sive disease, it has been repeated that the current velocity criteria to calculate stenosis tends to overestimate the severity when there is a contralateral highly stenotic or occluded carotid artery. METHODS: patient records were reviewed for 592 consecutive carotid endarterecto mies performed from 1987 to 1994. Preoperative and postoperative duple x scan results were compared in a subset of patients in whom duplex ov erestimated the degree of stenosis, as compared to preoperative angiog raphy. RESULTS: A fetal of 146 patients were identified in whom duplex overestimated the degree of stenosis contralateral to a high grade st enosis or an occlusion. Of 76 arteries, 18 (23.7%) contralateral to an occluded artery were overestimated by duplex, and 128 (27.0%) of 474 arteries contralateral to a high grade stenosis were overestimated, Fo llowing endarterectomy 44 (51.8%) of 128 nonoperated contralateral ste noses decreased by at least one duplex category. The average peak syst olic frequency (PSF) decreased by 1175 Hz (P = 0.0018), and the averag e end diastolic frequency (EDF) decreased by 475 Hz (P = 0.011). CONCL USIONS: Patients with high grade stenosis have a significant decrease in PSF and EDF in the unoperated carotid after endarterectomy, support ing a compensatory flow phenomenon, This often results in a decrease i n the postoperative duplex defined stenosis by at least one category, The clinical significance of these findings is of increasing importanc e as carotid surgery is being performed more frequently without angiog raphy.