Theoretical prediction of low-density lipoproteins concentration at the luminal surface of an artery with a multiple bend.

To elucidate the mechanisms of localization of atherosclerotic lesions in man, the effects of various physical and hemodynamic factors on transport of atherogenic low-density lipoproteins (LDL) from flowing blood to the wall of an artery with a multiple bend were studied theoretically by means of a computer simulation under the conditions of a steady flow. It was found that due to a semipermeable nature of an arterial wall to plasma, flow-dependent concentration polarization of LDL occurred at the luminal surface of the vessel, creating a region of high LDL concentration distal to the apex of the inner wall of each bend where the flow was locally disturbed by the formation of secondary and recirculation flows and where wall shear stresses were low. The highest surface concentration of LDL occurred distal to the acute second bend where atherosclerotic intimal thickening developed. At a Re0=500, the values calculated using estimated diffusivities of LDL in whole blood and plasma were respectively 35.1% and 15.6% higher than that in the bulk flow. The results are consistent with our hypothesis that the localization of atherosclerotic lesions results from the flow-dependent concentration polarization of LDL which creates locally a hypercholesterolemic environment even in normocholesterolemic subjects, thus augmenting the uptake of LDL by vascular endothelial cells existing at such sites.