Finite element analysis of transport phenomena relating to atherosclerogenesis and thrombogenesis in the human internal carotid artery

The influence of the local geometry of the human internal carotid artery on the flow patterns and the mass transport of the blood constituents relating to the genesis of atherosclerosis and thrombosis were investigated through the finite element simulation, using FIDAP 7.52. The pulsatile blood flow was described by the Navier-Stokes equations for incompressible Newtonian fluid, and the mass transport was described by the convection diffusion equations. The two reaction mechanisms representing the hydrolysis of LDL into insoluble free cholesterol and the blood clot formation from fibrinogen and platelets were modeled using the constant reaction rate. These reactions were implemented at the fluid entity to represent the bulk reaction and at the wall entity to represent the surface reaction separately. The numerical solutions showed highly complex flow patterns at the sinus and the siphon. The expanded diameter of the sinus, the curvatures of the siphon, and sudden increase and decrease in flow rate at the inlet during first half cardiac cycle resulted in vortices. The vortices created temporal stagnant flow zones with relatively large temporal variations in wall shear stress. At these sites, high luminal surface concentrations of free cholesterol and blood clot were obtained for both bulk reaction model and surface reaction model with minor differences. It has been concluded that there are strong correlations between the influence of flow patterns and wall shear stress distributions induced by the arterial geometry on the mass transport of macromolecules and the development of atherosclerosis and thrombosis.