Do Common Carotid Artery Velocities Consistently Decrease With Proximity to the Bifurcation?

Distal (near bifurcation) common carotid artery (CCA) peak systolic velocity (PSV) values are lower than near the origin (proximal). We investigate whether this applies to patients with internal carotid artery (ICA) stenosis ≥ 50% (PSV ≥ 125 cm/s). We studied 328 patients. We excluded carotid arteries with CCA stenosis and carotid endarterectomy. We evaluated degree of stenosis as absent, mild (1%-15%), moderate (16%-49%), and significant (≥50%; PSV ≥ 125 cm/s). We used paired t tests to compare the proximal with distal PSV values as a function of stenosis severity and analysis of variance for between stenosis differences. We studied 640 out of 656 bifurcations. Mean age was 68.9 (SD = 11.8) years, and 70% (228) men. Mean distal CCA PSV was 80.3 cm/s (SD = 23.1 cm/s) and proximal, 93.7 cm/s (SD = 26.6 cm/s). The difference between proximal and distal CCA PSV for ICA lesions < 50% (n = 553; 14.8 ± 22.6 cm/s) was higher (P = .004) than with an ICA stenosis ≥ 50% (n = 87; 4.6 ± 24.1 cm/s). While distal CCA PSV decreases in patients with absent/mild/moderate plaque, PSV velocities are more consistent along the length of the CCA with higher degrees of ICA stenosis. This might in part explain the reliability of the ICA/CCA velocity ratio for grading stenosis severity ≥50%.