Nouri Mohammad, Jalali Farhang, Karimi Gholamreza, Zarrabi Khalil
Department of Chemical Engineering, University of Tehran, Tehran, Iran.
Department of Chemical Engineering, University of Tehran, Tehran, Iran.
Comput Biol Med. 2015 Jul;62:206-21. doi: 10.1016/j.compbiomed.2015.04.013. Epub 2015 Apr 20.
Accumulation of low density lipoproteins (LDL) in the vessel wall is suggested as the initiator of atherosclerosis and coronary stenosis. This process is associated with the performance of endothelium layer that regulates entering of macromolecules to the vessel wall. Therefore, the present study aims to investigate sub-endothelial accumulation of LDL molecules in a coronary tree and predict atherosclerosis prone sites. Non-Newtonian blood flow is simulated for normal and hypertensive conditions through the lumen of a right coronary artery reconstructed from computed tomography (CT) images. A three-pore model is implemented as the endothelium boundary condition and hence, plasma flow and LDL transport are simulated within the arterial wall. Based on the pore model, endothelium pathways divide into normal junctions, vesicles and leaky junctions. Most of LDL molecules pass through the leaky junctions that arise at locations with low wall shear stress (WSS). Results indicate that increase in the number of leaky junctions at branch points with low WSS can lead to both elevated levels of sub-endothelial LDL accumulation and atherosclerosis risk. Findings reveal that at the branch points with disturbed flow, sub-endothelial concentration of LDL for the hypertensive condition is higher than the normal condition, however for the rest of regions with uniform geometry and unidirectional flow, this is reversed. Comparisons of non-Newtonian and Newtonian flows show mean increases of 34% and 13% in the sub-endothelial concentrations of Newtonian flows during the normal and hypertensive conditions, respectively.
血管壁中低密度脂蛋白（LDL）的积累被认为是动脉粥样硬化和冠状动脉狭窄的起始因素。这一过程与调节大分子进入血管壁的内皮细胞层的功能有关。因此，本研究旨在研究冠状动脉树中LDL分子的内皮下积累情况，并预测易发生动脉粥样硬化的部位。通过计算机断层扫描（CT）图像重建的右冠状动脉管腔，模拟了正常和高血压情况下的非牛顿血流。采用三孔模型作为内皮边界条件，从而在动脉壁内模拟血浆流动和LDL运输。基于孔模型，内皮通道分为正常连接、囊泡和渗漏连接。大多数LDL分子通过壁面剪应力（WSS）较低部位出现的渗漏连接。结果表明，低WSS分支点处渗漏连接数量的增加会导致内皮下LDL积累水平升高和动脉粥样硬化风险增加。研究结果显示，在血流紊乱的分支点处，高血压情况下LDL的内皮下浓度高于正常情况，然而在其余几何形状均匀且单向流动的区域，情况则相反。非牛顿流与牛顿流的比较表明，在正常和高血压情况下，牛顿流的内皮下浓度分别平均增加34%和13%。
