Effect of endothelial injury and increased blood pressure on albumin accumulation in the arterial wall: a numerical study.

The present study investigates the influence of endothelial damage and of blood pressure on albumin accumulation in the arterial wall. For this purpose a numerical model for the coupled mass transport processes in the arterial lumen and in the various layers of the arterial wall is developed. The model considers the transport in the endothelium, intima, internal elastic lamina (IEL) and media of a straight axisymmetric arterial segment. In the arterial lumen fully developed stationary blood flow is assumed, the filtration velocity in the wall layers is calculated applying Darcy's law. The description of the luminal mass transport uses the stationary convection-diffusion equation, the transport in the porous intima and media is modelled applying the volume-averaged stationary convection-diffusion-reaction equation. The transport processes in the lumen, intima and media are coupled by the flux across the endothelium and IEL, which is mathematically described using the Kedem-Katchalsky equations. The numerical solution of the transport equations applies the finite element method. The results demonstrate a high resistance of the healthy endothelium to macromolecule exchange between blood and the artery wall. The reduced resistance of an injured endothelium causes an increased mass flux into the wall which results in higher concentration levels within the wall. The effect of the blood pressure on the wall concentration level is different for a helathy and an injured endothelium. In the case of a healthy endothelium a blood pressure increase causes a decrease of the intimal concentration and an increase of the medial concentration, whereas in the case of an injured endothelium an increased blood pressure results in higher concentration levels within the intima and media.