A CFD Study of the Luminal Surface Concentration of Low Density Lipoproteins in Coronary Arteries: The Effects of Wall Motion

摘要

The transport of low density lipoproteins (LDLs) from the blood to the arterial wall and their accumulation within the arterial intima are key steps in atherogenesis. In coronary arteries these may be affected by the local haemodynamic factors including their physiological motion, whose effect on LDL transport has not been studied elsewhere. Therefore, this study was initiated to investigate the transport of LDL to the endothelium (a semi permeable membrane) in a moving 3-D model of the Left Anterior Descending (LAD) coronary artery segment by using the commercial finite volume CFD solver, FLUENT (v6.1.18, Fluent Inc). A time varying inlet parabolic velocity and planar vessel wall motion waveforms obtained from literature were imposed as boundary conditions. The results showed the occurrence of flow-dependent concentration polarization of LDL at the endothelial surface in varying degrees in pulsatile flow and pulsatile flow with wall motion. In both the cases, this effect was more pronounced at the inner wall of bend where wall shear stress (WSS) was lower. The motion induced elevation of WSS and stronger secondary flows seem to promote better cross mixing, resulting in a lower concentration of LDL, especially at the inner wall when compared to the pulsatile flow simulations. Taken together, these results suggest that the vessel wall motion may have a dominant influence on LDL transport. However the degree of influence would also depend on the individual motion patterns and the reaction mechanisms used. This warrants future studies on more physiologic models to gain a fundamental understanding on LDL transport and consequently on conditions such as atherosclerosis.