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 arterial (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 1997. Only ICAs (n = 98, in 57 patients) without ipsilateral CCA disease at angiography 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 indication for endarterectomy, variability in CCA velocities could have altered recommendations in 16 (28%) of 57 patients. Receiver operating characteristic analysis showed that ratios made by using the three CCA velocities or their mean were not significantly different.
CONCLUSION: Variability in velocity measurements along the course of the CCA in patients with ICA disease can be substantial and can result in inaccuracies in assessment of carotid stenosis.