Variability of Doppler US measurements along the common carotid artery: Effects on estimates of internal carotid arterial stenosis in patients with angiographically proved disease

PURPOSE: To determine the effect of variability of common carotid arterial (CCA) velocities on velocity ratios used to assess internal carotid arteria l (ICA) stenosis. MATERIALS AND METHODS: Doppler ultrasonographic (US) velocity measurements were obtained at three levels in the CCA and in the carotid bulb and ICA in all patients referred for carotid US between September 1996 and October 19 97. Only ICAs (n = 98, in 57 patients) without ipsilateral CCA disease at a ngiography were analyzed. The range of CCA peak systolic velocities (PSVs) and end diastolic velocities (EDVs) and velocity ratios were calculated for each CCA measurement. For each ICA/CCA velocity ratio, receiver operating characteristic analysis was performed. RESULTS: CCA PSV and EDV ranges averaged 23.1 cm/sec +/- 15.7 (SD) and 5.1 cm/sec +/- 3.6, respectively. For a given side, the difference averaged 1.0 +/- 1.3 for PSV ratios and 2.7 +/- 6.9 for EDV ratios, depending on where CCA measurements were taken. By using a threshold of 60% stenosis as indica tion for endarterectomy, variability in CCA velocities could have altered r ecommendations in 16 (28%) of 57 patients. Receiver operating characteristi c analysis showed that ratios made by using the three CCA velocities or the ir mean were not significantly different. CONCLUSION: Variability in velocity measurements along the course of the CC A in patients with ICA disease can be substantial and can result in inaccur acies in assessment of carotid stenosis.