Choice and Impact of a Non-Newtonian Blood Model for Wall Shear Stress Profiling of Coronary Arteries

Abstract

the modelling of the in-vivo physiological situation is complex and time-consuming. Methodological simplifications are desirable. The aim of this study was to investigate the impact of non-Newtonian blood modelling and to determine the best suitable blood model. This study simulates numerically steady blood flow in an anatomically realistic model of the left coronary artery main bifurcation. The geometry was reconstructed from a post-mortem vessel cast. Three non-Newtonian (Casson, Walburn-Schneck and Generalized Power Law) as well as the Newtonian blood models were compared. First we tested the ability of the models to fit different experimental data performed with different hematocrit and total protein minus albumin (TPMA) concentration values under different temperatures. It was found that wall shear stress (WSS) is influenced by the used model. However, only the Walburn-Schneck model revealed significantly varied WSS distribution (mean difference of about 30% measured point by point) and magnitude (17% higher mean WSS) if compared with Newtonian model. The adapted Generalized Power Law (GPL) model allows the best fitting to the known experimental data with a Pearson’s coefficient of R=0.9998. This is especially valid for fitting the flattening of the viscosity curve to very low shear rate values under pulsatile flow conditions. An adapted GPL model which includes the dependence of hematocrit, temperature and TPMA concentration is proposed. The impact of the non-Newtonian blood model in WSS profiling of coronary artery flow may be neglected for clinical studies with normal or obstructive (narrowed) coronary arteries. However, for dilated (enlarged) coronary arteries, the non-Newtonian blood model is significant and should be included in the numerical model of the coronary flow.