Effect of Nonlinear Blood Viscosity on LDL Transport and Fluid-Structure Interaction Biomechanics of a Multi-stenosis Left Circumflex Coronary Artery

Abstract

This paper investigates the relationships between nonlinear, non-Newtonian fluid viscosity variability and low-density-lipoprotein (LDL) particle transport in a biomechanical, fluid-structure interaction (FSI) model of the left circumflex coronary artery. Included in the in vivo based biomechanical model is a multi-layered, hyperelastic and viscoelastic artery wall with two lipid-rich plaques, three-dimensional motion of the heart, pulsatile fluid velocity and pressure and a non-Newtonian continuous phase with a discrete phase representing LDL. The in vivo-based model is fully coupled between the fluid and structure components as well as the continuous and discrete fluid phases. Significantly, the relationship between LDL transport and non-Newtonian blood viscosity that varies within physiological ranges (influenced by haematocrit ranging from 40 to 60%), is assessed using FSI for the first time. Results show an increase in LDL concentration at the lumen wall with increasing haematocrit; minimum wall shear stress (WSS) during diastole also increased across the stenosis while maximum (systole) WSS was unchanged. The von Mises stress in the intima peaks at the plaque shoulders which is also the location of minimum wall shear stress and maximum LDL concentration; as endothelial cells respond to mechanical stimuli, regions of peak von Mises stress and peak LDL concentration present high-risk sites for further plaque development. This emphasizes the importance of using accurate and patient-specific nonlinear fluid/blood properties during LDL transport modelling in FSI biomechanics. These results are significant for clinicians understanding of risk factors leading to atherosclerotic plaque development as well as engineers working to develop more robust and accurate biomechanical models of the coronary vasculature to predict disease.