Effect of Stenosis Severity on Wall Shear Stress Based Hemodynamic Descriptors using Multiphase Mixture Theory

A variety of wall shear stress (WSS) based hemodynamic descriptors have been defined over the years to study hemodynamic flow instabilities as potential indicators or prognosticators of endothelial wall dysfunction. Generally, these hemodynamic indicators have been calculated numerically using ‘single phase’ approach. In single phase models, the flow-dependent cell interactions and their transport are usually neglected by treating blood as a single phase non- Newtonian fluid. In the present investigation, a multiphase mixture-theory model is used to define the motion of red blood cells (RBCs) in blood plasma and interactions between these two-components. The multiphase mixture theory model exhibited good agreement with the experimental results and performed better than non-Newtonian single phase model. The mixture-theory model is then applied to simulate pulsatile blood flow through four idealized coronary artery models having different degrees of stenosis (DOS) severities viz., 30, 50, 70 and 85% diameter reduction stenosis. The maximum WSS is seen at the stenosis throat in all the cases and maximum oscillatory shear index (OSI) is seen in downstream region of the stenosis. Our findings suggest that for degree of coronary stenosis more than 50%, a more disturbed fluid dynamics is observed downstream of stenosis. This could lead to further progression of stenosis and may promote a higher risk of atherogenesis and plaque buildup in the flow-disturbed area. The potential atherosclerotic lesion sites were identified based on clinically relevant values of WSS, timeaveraged WSS gradient (TAWSSG), time-averaged WSS (TAWSS), and OSI. Finally, the change in potential atherosclerotic lesion sites with respect to DOS has been quantified.