Effect of carotid bulb size and blood viscosity in carotid atherosclerotic plaque using CFD

Carotid atherosclerotic plaque is one of the various causes of ischemic stroke. These plaques primarily accumulate in the carotid bulb and progress into blood clots, resulting in occlusion of the cerebral artery. In this study, we carried out CFD simulations to examine the blood flow characteristics depending on the carotid bulb size and blood viscosity. Based on the TF-AHCB model, the carotid bulb size was adjusted by modifying the maximum diameter of the ICA bulb. Blood was treated as an incompressible Newtonian fluid, and the arterial walls were set as rigid no-slip walls. The blood viscosities are 3.3, 5.2, and 7.5 cP corresponding to several hematocrit levels (30%, 45%, and 60%, respectively). The velocity fields showed that a larger carotid bulb size and lower blood viscosity generated a wider recirculation area in the ICA bulb. Quantifying the proportion of low wall shear stress (< 0.5 Pa) region to the total arterial wall area, i.e., ξ, the case of the largest carotid bulb size and the lowest blood viscosity resulted in the highest ξ (8.7%) among the simulated cases. As high ξ indicates a great likelihood of atherosclerosis, it may pose the highest risk of plaque formation.