Koshiba Nobuko, Ando Joji, Chen Xian, Hisada Toshiaki
Graduate School of Frontier Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
J Biomech Eng. 2007 Jun;129(3):374-85. doi: 10.1115/1.2720914.
Atherosclerosis localizes at a bend andor bifurcation of an artery, and low density lipoproteins (LDL) accumulate in the intima. Hemodynamic factors are known to affect this localization and LDL accumulation, but the details of the process remain unknown. It is thought that the LDL concentration will be affected by the filtration flow, and that the velocity of this flow will be affected by deformation of the arterial wall. Thus, a coupled model of a blood flow and a deformable arterial wall with filtration flow would be invaluable for simulation of the flow field and concentration field in sequence. However, this type of highly coupled interaction analysis has not yet been attempted. Therefore, we performed a coupled analysis of an artery with multiple bends in sequence. First, based on the theory of porous media, we modeled a deformable arterial wall using a porohyperelastic model (PHEM) that was able to express both the filtration flow and the viscoelastic behavior of the living tissue, and simulated a blood flow field in the arterial lumen, a filtration flow field and a displacement field in the arterial wall using a fluid-structure interaction (FSI) program code by the finite element method (FEM). Next, based on the obtained results, we further simulated LDL transport using a mass transfer analysis code by the FEM. We analyzed the PHEM in comparison with a rigid model. For the blood flow, stagnation was observed downward of the bends. The direction of the filtration flow was only from the lumen to the wall for the rigid model, while filtration flows from both the wall to the lumen and the lumen to the wall were observed for the PHEM. The LDL concentration was high at the lumenwall interface for both the PHEM and rigid model, and reached its maximum value at the stagnation area. For the PHEM, the maximum LDL concentration in the wall in the radial direction was observed at the position of 3% wall thickness from the lumenwall interface, while for the rigid model, it was observed just at the lumenwall interface. In addition, the peak LDL accumulation area of the PHEM moved about according to the pulsatile flow. These results demonstrate that the blood flow, arterial wall deformation, and filtration flow all affect the LDL concentration, and that LDL accumulation is due to stagnation and the presence of filtration flow. Thus, FSI analysis is indispensable.
动脉粥样硬化定位于动脉的弯曲处和/或分叉处，低密度脂蛋白（LDL）在内膜中积聚。已知血流动力学因素会影响这种定位和LDL积聚，但该过程的细节仍不清楚。据认为，LDL浓度会受到滤过流的影响，而这种流的速度会受到动脉壁变形的影响。因此，一个包含血流、可变形动脉壁和滤过流的耦合模型对于依次模拟流场和浓度场将非常有价值。然而，这种高度耦合的相互作用分析尚未尝试过。因此，我们对具有多个连续弯曲的动脉进行了耦合分析。首先，基于多孔介质理论，我们使用能够同时表达滤过流和活体组织粘弹性行为的多孔超弹性模型（PHEM）对可变形动脉壁进行建模，并通过有限元方法（FEM）使用流固耦合（FSI）程序代码模拟动脉腔内的血流场、滤过流场和动脉壁内的位移场。接下来，基于获得的结果，我们通过FEM使用传质分析代码进一步模拟LDL的传输。我们将PHEM与刚性模型进行了比较分析。对于血流，在弯曲处下方观察到血流停滞。对于刚性模型，滤过流的方向仅从管腔到管壁，而对于PHEM，则观察到既有从管壁到管腔的滤过流，也有从管腔到管壁的滤过流。对于PHEM和刚性模型，LDL浓度在管腔-壁界面处都很高，并在停滞区域达到最大值。对于PHEM，在距管腔-壁界面壁厚3%的位置观察到壁内径向方向上的最大LDL浓度，而对于刚性模型，仅在管腔-壁界面处观察到。此外，PHEM的LDL积聚峰值区域随脉动流而移动。这些结果表明，血流、动脉壁变形和滤过流都会影响LDL浓度，并且LDL积聚是由于血流停滞和滤过流的存在。因此，FSI分析是必不可少的。
