Carotid bifurcation position and branching angle in patients with atherosclerotic carotid disease

Carotid artery bifurcation (CB) is the preferred site for development of atherosclerosis (AS) in extracranial cerebral arteries; internal carotid artery stenosis is the most common cause of ischemic stroke. The frequent atherosclerotic disease of CB may best be explained by the hemodynamic influence of complex blood flow that results from the unique geometry of the bifurcation. Few papers analyze all possible geometric structural characteristics of this bifurcation. While performing many carotid endarterectomies, we noticed that a certain correlation between CB height in the neck and its angle existed, that a larger angle is accompanied with increased frequency of elongation and kinking and that CB shape influences distribution of atherosclerosis. The purpose of this paper is to quantify and evaluate these clinical observations. Radiogrametric analysis of 154 bi-plane orthogonal aortic arch arteriograms of patients with symptomatic atherosclerotic carotid artery disease was performed and a total of 289 CBs were analyzed. The CB height in relation to cervical spine segments was measured and real angles of each bifurcation were calculated. A positive linear correlation between CB height and angle exists: the CB angle increases /decreases 3.34 degrees for each third of the cervical vertebral body height or intervertebral space height. The CB is positioned a little higher on the left side. The proximal border of the atherosclerotic process is found at the level of intersection of the axes of the common carotid artery branches in 92.6% of examined CBs. In lower CBs (with smaller angles) the proximal border was located in the last segment of the common carotid artery, while in high bifurcations (wider angles) the proximal border of the AS process is more distally in the blood flow, in the beginning of the internal carotid artery, and the process was more extensive. High CBs are more suitable for eversion endarterectomy while normal and low CBs are more suitable for open (classic) carotid endarterectomy. The influence of the geometric risk factor demands further investigation.