Vascular surgical society of great britain and ireland: duplex ultrasonography overestimates internal carotid artery stenosis in the presence of contralateral disease

Abstract

BACKGROUND: Duplex ultrasonography is increasingly used as the only investigation before endarterectomy for internal carotid artery stenosis. Contralateral disease is present in approximately 20 per cent of these patients and may lead to overestimation of the carotid stenosis by duplex imaging before surgery. This problem was investigated in the present study. METHODS: Peak systolic and diastolic duplex velocities were compared with angiographic data before 126 consecutive carotid endarterectomies (106 symptomatic, eight asymptomatic, 12 precoronary revascularization). Some 3 months later velocities were repeated to assess whether endarterectomy of a diseased carotid artery affected contralateral velocity measurements. RESULTS: Significant contralateral carotid disease was present in 36 (29 per cent) of the 126 preoperative angiograms (14 occlusions, 22 stenoses greater than 60 per cent). Three months after operation 119 of the endarterectomy sites were widely patent. Duplex ultrasonography of the 105 non-operated patent contralateral arteries showed a decrease in mean(s.d.) peak systolic and diastolic velocities from 1.21(0.83) and 0.41(0.29) m s-1 before operation to 1.08(0.69) and 0.35(0.24) m s-1 respectively (P < 0.01, paired t test). Preoperative duplex velocities had indicated contralateral disease of greater than 50 per cent stenosis in 34 cases, but 14 of these were reclassified to less severe disease following surgery. Thirteen of these had been correctly classified by preoperative angiography while use of systolic and diastolic internal/common carotid artery velocity ratios reduced the overestimation of stenosis in eight of the 14 cases. CONCLUSION: Bilateral carotid artery disease is common and may lead to overestimation of stenosis by duplex ultrasonography, which should therefore be supplemented with other modes of imaging.