Simulation of a Pro-Atherogenic High-Risk Carotid Artery Bifurcation Geometry*

Pathological blood flow-induced shear stress is associated with atherosclerosis, a cardiovascular disease that is a leading cause of deaths in the US. Physiological flow CFD simulations are used to investigate the following wall-shear-stress metrics: time-averaged-wall-shear-stress (TAWSS), oscillatory shear index (OSI) and relative residence time (RRT) in carotid artery bifurcation models. Two carotid artery geometries were adopted from patient-averaged anatomies with different internal, external, and common carotid artery features (ICA, ECA and CCA, respectively). The geometry associated with high risk of disease has a larger ICA angle, asymmetric branching angle and lower ICA/CCA diameter ratio than the low-risk case. Unsteady flow simulations employ a physiological inflow waveform and resistive outflow conditions. Low TAWSS regions, generally associated with plaques, were found at the outer ICA sinus wall for both geometries. The high-risk geometry exhibits flow separation and low WSS with high multi-directionality in the ICA. Furthermore, high OSI and RRT were observed at the ICA and ECA outer walls, downstream of the bifurcation for the high-risk geometry. Results demonstrate the utility of OSI and RRT, to augment classical TAWSS, as indicators of atherosclerosis risk.