Flow Patterns at the Stenosed Carotid Bifurcation: Effect of Concentric versus Eccentric Stenosis

Abstract

Carotid stenosis severity is a commonly used indicator for assessing risk of stroke. However, the majority of individuals with severe carotid artery disease never suffer a stroke, and strokes can occur even with only mild or moderate stenosis. This suggests local factors (other than stenosis severity) at or near the carotid artery bifurcation may be important in determining stroke risk. In this paper we investigate the effect of stenosis geometry on flow patterns in the stenosed carotid bifurcation, using concentrically and eccentrically stenosed anthropomorphic carotid bifurcation models having identical stenosis severity. Computational simulations and experimental flow visualizations both demonstrate marked differences in flow patterns of concentric and eccentric stenosis models for moderately and severely stenosed cases, respectively. In particular, we identify post-stenotic recirculation zone size and location, and spatial extent of elevated wall shear stress as key factors differing between the two geometries. As these are also rotid plaque more vulnerable to cerebral embolus prokey biophysical factors promoting thrombogenesis, we propose that the stenosed carotid bifurcation geometry--or the induced flow patterns themselves--may provide more specific indicators for those plaques that are vulnerable to enhanced thromboembolic potential, and hence, increased risk of ischemic stroke.

Eccentric Stenosis of the Carotid Artery Associated with Ipsilateral Cerebrovascular Events

“…5 Using the models, the deposition of platelet and monocyte-sized particles on the vessel wall was more distinct proximal to the eccentric stenosis than proximal to the concentric stenosis. 25 This suggests that eccentric stenosis is more prone to platelet activation and aggregation due to attenuated platelet deposition and plaque growth, as well as rupture due to attenuated monocyte deposition. Thus, eccentric stenosis may have a high potential for thrombus formation, which may lead to an increased risk of cerebrovascular events.…”

Comparison of Carotid Plaque Ulcer Detection Using Contrast-Enhanced and Time-of-Flight MRA Techniques

“…To illustrate the effect of ulcer orientation on blood flow patterns within the ulcer, we performed CFD simulations of pulsatile flow in an idealized carotid bifurcation with a 30% eccentric stenosis, as previously described, 29 to which we attached representative distally and proximally pointing ellipsoidal ulcers. 30 Flow patterns were visualized by randomly seeding 250,000 tracer particles within and away from the ulcer and tracking their evolution over 3 cardiac cycles, using previously reported techniques.…”

A Computational Simulation of the Effect of Hemodilution on Oxygen Transport in Middle Cerebral Artery Vasospasm

“…This is in contrast to many computational models of the arterial system, which uses a flow boundary condition based on experimentally or clinically measured flows (Hayase et al, 2011;Milner et al, 1998;Steinman et al, 2000). The limitation of this approach is that the flow pattern is highly dependent on upstream geometry that can vary from among patients, which we are not able to simulate.…”