Inertial-dominant flow in an arterial network contributes to atherogenesis by creating sparse regions of slow or recirculating flows

It has been known that plaque location is related to the shape of middle cerebral artery (MCA). Different plaque locations depending on the MCA shapes might come from inertial effect of blood flow. In this study, steady-state computational fluid dynamics simulations were carried out on various MCA shapes including four straight perforators under several Reynolds numbers (193, 261, and 400) based on diameter and average velocity at the MCA inlet. The blood and arterial walls were treated as incompressible Newtonian fluid and no-slip rigid walls, respectively. In the cases of straight- and U-shape MCAs, the blood can hardly flow toward perforators due to fluid inertia and low wall shear regions dominantly appear at entrance of the perforators (by recirculation), which increases probability of superior-side (usual origin of MCA perforators) atherosclerotic plaques. With increment of the Reynolds number by reduction of blood viscosity, the flows tend to sweep inner curvature of the MCAs due to increased contribution of inertia; hence, slow flow and low shear zones are created at outer curvature. Therefore, in terms of hemodynamics, low blood viscosity may promote branch atheromatous disease due to sparse zone formation by inertia dominance under equivalent MCA shapes.