Atherosclerosis is a common and hazardous cardiovascular pathology that affects many humans each year. Experimental and computational studies have implicated a relationship with the local hemodynamics, such as wall shear stress (WSS), caused by blood flow in the vessels. Specifically, studies link the hemodynamics to a morphological response by the shear-sensitive endothelial cells (ECs) that line the vessel and the biological processes they regulate. However, blood transport computational simulation studies in the past assume a smooth wall and do not account for the shear-dependent shape of ECs when analyzing shear stress and other hemodynamics. In order to evaluate the effects of EC morphology on shear stress, a preliminary study was done by creating 3D models of straight and...[ Read more ]

Atherosclerosis is a common and hazardous cardiovascular pathology that affects many humans each year. Experimental and computational studies have implicated a relationship with the local hemodynamics, such as wall shear stress (WSS), caused by blood flow in the vessels. Specifically, studies link the hemodynamics to a morphological response by the shear-sensitive endothelial cells (ECs) that line the vessel and the biological processes they regulate. However, blood transport computational simulation studies in the past assume a smooth wall and do not account for the shear-dependent shape of ECs when analyzing shear stress and other hemodynamics. In order to evaluate the effects of EC morphology on shear stress, a preliminary study was done by creating 3D models of straight and curved vessels with either no cells, sheared ECs, or unsheared ECs. A kernal independent fast multipole boundary element method (BEM) code was used to simulate Stokes flow. This initial study on smaller vessels with a regular, idealized EC surface found that in all cases, maximum WSS was increased and average WSS was decreased with the inclusion of ECs. This idea was then applied to patient-specific, realistic, aorta models which are commonly used in atherosclerosis studies. A multiscale algorithm which applies a wall velocity boundary condition representing blood flow over an EC (slip velocity) in a finite volume method (FVM) simulation of aortic blood flow was developed. Simulation results from a branchless aortic aneurysm model with revealed that the inclusion of EC wall geometry in pathologically disturbed flow resulted in an increase in vessel wall area with low time-averaged WSS and high OSI, as well as large changes in time-dependent WSS at various points of the vessel. These results show that EC morphology should be considered in future studies using CFD to identify pathology triggering hemodynamic parameters.