Changes in internal carotid blood flow after carotid endarterectomy correlate with preoperative stenosis

The relationship between preoperative stenosis and the effect of carotid endarterectomy (CEA) upon internal carotid blood flow (ICF) is not well understood. With the intention of better characterizing this, we compared intraoperative measurements of internal carotid blood with the maximum single diameter stenosis found in preoperative angiograms.

Fifty-two patients undergoing 64 carotid endarterectomies (12 bilateral) had transit-time ultrasound perivascular probes used to measure ICF before and after CEA, and the percent change in ICF (% delta ICF) achieved was calculated. Maximum single-diameter stenosis was determined by comparing the least diameter in the flow path from the common carotid to the normal-appearing internal carotid just distal to bifurcation disease.

The entire group had a mean of 53 +/- 21% stenosis found on preoperative angiograms, and % delta ICF averaged 64 +/- 92%. When divided into subgroups based on degree of stenosis, patients with 0% to 40% stenosis (n = 17) had % delta ICF of 32 +/- 46%, patients with 41% to 70% stenosis (n = 30) had % delta ICF of 72 +/- 105%, and patients with more than 70% stenosis had % delta ICF of 168 +/- 160%. The differences in % delta IC were significant for the > 70% group compared with the other groups (analysis of variance, P < 0.005), and marginally significant (P = 0.056) between the 0% to 40% and the 41% to 70% groups. The scatter plot of % delta ICF versus stenosis showed a significant second order direct correlation (r = 0.428, P < 0.001) and disproportionate increases in ICF above 60% stenosis.

A curvilinear relationship between stenosis and immediate increase in ICF after CEA was demonstrated in agreement with theory, and in those patients with more than approximately 60% single-diameter stenosis, large disproportionate increases in blood flow were more frequently observed.