Influence of Intel Conditions in Wall Shear Stress Distributions of Left Coronary Arteries in Patient-Specific Simulations

Abstract

The left coronary artery (LCA) is one of the most important sites of atherosclerotic plaque formation and its progression may lead to stroke. It is accepted that the location of atherosclerotic plaques is correlated with sites subjected to low abnormal values of wall shear stress (WSS). However, little is known about flow conditions at the inlet of the LCA, a factor difficult to determine in common clinic studies and which in turn may be determinant in the WSS distribution along the LCA. The purpose of this work is to investigate numerically the role of the flow inlet conditions of the LCA in the consequent WSS distribution in a proposed patient-specific method. A three-dimensional model of the LCA of a healthy patient was reconstructed based on a computer tomography (CT) study. A finite element volume mesh was constructed and blood flow trough it was modeled with the finite element method. Five simulations with different inlet conditions were performed: (S1) a surface normal parabolic velocity profile, (S2) a surface normal planar velocity profile, (S3) a surface normal Dean’s profile, (S4) a parabolic profile with the incidence direction being the bisectrix of aorta and ostium directions and (S5) a parabolic profile with a random incidence direction. WSS distributions were computed with later postprocessing. Results showed in all cases that the WSS distribution pattern did not differ between simulations. Being S1 the standard inlet condition, the other simulations showed some differences in WSS values, in all cases acceptable. S2 showed a mean WSS difference of 15%. S3 showed a mean WSS difference of 6%, whereas S4 and S5 of 32% and 38% respectively. In all cases, the difference in each point of the mesh was proportional to the WSS value, being more negligible the difference in the regions of interest (regions of low WSS). Also, the differences were concentrated in the first segment of the mesh where the flow developed. This work shows that WSS distribution pattern in the LCA does not depend of the inlet condition. Although the absolute values of WSS may be slightly different depending on the assumed condition (being the incidence direction the feature that most affected them), the objective is to localize the regions of low WSS, despite its absolute value. These results show that what is really determinant in WSS distribution is the particular geometry of the patient LCA.