Finite Element Modeling of LDL Transport in Carotid Artery Bifurcations

Abstract

The Low Density Lipoprotein (LDL) accumulation is the major factor which affects atherosclerosis during its early stages. Endothelial permeability is also influenced by local wall shear stresses. This phenomenon increases the water and macromolecule transport from the artery lumen to the artery wall. This paper presents a computational model of LDL transport from the arterial lumen to the arterial wall. More specifically, we investigate the blood flow dependent LDL transfer in a carotid artery bifurcation. The blood flow is modeled using the Navier-Stokes equations and the Darcy’s law is employed to study the transmural flow in the porous artery wall. The mass transfer problem is solved using the convection — diffusion equations. The combined fluid dynamics and mass transfer equations are based on volume flux and solute flux calculated using the Kedem — Katchalsky equations. The endothelial permeability and hydraulic conductivity depend on the shear stress. The numerical solution of the above equations is obtained using the finite element method. Our results confirm what the experimental studies report that LDL accumulation is achieved in artery regions where low shear stresses exist. In particular, in our model we observe elevated LDL aggregation in areas where the wall shear stress is lower than 2 Pa. Also the increase of LDL concentration occurs in a thin layer close to the artery wall at the outer parts of artery segments, which also agrees with the experimental observation. In addition, we concluded that shear stress affects the transport of macromolecules from the blood to the carotid artery wall.