Carotid Artery Anatomy and Geometry as Risk Factors for Carotid Atherosclerotic Disease

Abstract

Background and Purpose-Traditional vascular risk factors do not completely explain the asymmetry, racial, and sex differences in carotid artery disease. Carotid anatomy and geometry may play a role in the pathogenesis of internal carotid artery (ICA) stenosis, but their effects are unknown. We hypothesized that carotid artery anatomy and geometry would be independently associated with ICA stenosis. Method-This is a retrospective study of patients with CT angiography at Monash Medical Centre, 2006 to 2007. Carotid arteries were segmented using semiautomated methods to estimate measures of carotid anatomy and geometry. Measurements of carotid artery geometry were performed according to the recent article by Thomas and colleagues. ICA stenosis was dichotomized as Ͻ30% or Ն30% stenosis. Cluster logistic regression was used to examine the associations of anatomy and geometry with stenosis accounting for the paired arteries within subjects, adjusting for age, sex, and vascular risk factors. Results-Mean age of the sample (nϭ178) was 68.4 years (SD, 14 years). The following were independently associated with ICA stenosis: ICA radius at the bifurcation (OR, 0.20; 95% CI, 0.14 -0.

Morphometric and hemodynamic analysis of atherosclerotic progression in human carotid artery bifurcations

“…51 Ϯ 16°, P ϭ 0.14), which was consistent with the results of Bijari et al (3). In contrast, Phan et al (23) found a significant increase of the ICA angle in adults with mild and severe stenoses. This disagreement may be attributed to racial differences (people of Caucasian origin vs. Chinese) (28).…”

“…Although a complete comparison showed significant difference of carotid artery bifurcations between control subjects and patients with carotid artery disease, the sample size (30 control subjects and 30 patients with carotid artery disease) in the retrospective study was relatively small compared with previous studies (3,23). This requires further analysis with larger sample size in a prospective study.…”

“…Atherosclerotic plaques usually reside in artery bifurcations with complex flow patterns (6,7,10,13,15,17). Because of its clinical relevance to stroke (9), the morphometry of human carotid artery bifurcation [comprised of the left and right common (CCA), internal (ICA), and external (ECA) carotid arteries] (16) has received intensive investigation (3,23,24,27). Researchers have proposed various geometric risk factors for the incidence of atherosclerotic plaques, e.g., increased bifurcation angle and enhanced differences in area ratios including the flare, proximal curvature, and tortuosity of ICA.…”

Atherosclerotic Plaque in the Left Carotid Artery Is More Vulnerable Than in the Right

“…Vessel anatomy in turn influences the hemodynamic forces and as such the left carotid artery may be exposed to higher arterial pressures. 6,32 Flow models have shown that atherosclerotic plaques preferentially develop in areas with low wall shear stress, such as at bifurcations or inner curves. 33 Wall shear stress and stress inside the vessel wall may affect plaque formation and composition by causing alterations in wall structure and metabolism.…”

“…6,7 Furthermore, it is feasible that not only plaque severity but also plaque composition vary according to location. 8 Some plaque components, such as intraplaque hemorrhage (IPH), are presumed to enhance vulnerability of the plaque, whereas calcification may promote plaque stability.…”