3.2　支架植入对血管的损伤和血流动力学的影响

血管支架的植入极大地改变了局部血管的力学微环境。宏观上看，由于支架对管腔的扩张作用，整个支架段血管恢复正常血管的疏通状态，同时斑块狭窄处血流的高切应力状态也将恢复为相对低的切应力。然而在植入支架的局部血管段，由于支架的存在导致单向流动的血流产生了一个流体分离区域，在支架与血管交界处流体发生急剧反转，血流紊乱形成扰动流，而在近心端的支架边缘和局部表面却具有较高的切应力（图3-1）。

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图3-1　支架植入对血流动力学的影响。ANSYS ICEM CFD模拟支架植入后血管壁的切应力分布，显示支架丝表面为高切应力区域，而血管壁面切应力较低。支架局部引起紊流，近心端具有较高切应力，形成涡流。［引自：Farhad R et al. Hemodynamics in coronary arteries with overlapping stents［J］. J Biomech, 2014, 47（2）: 505-511.］
Figure 3-1　Effect of stent implantation on hemodynamics. ANSYS ICEM CFD simulated the shear force distribution on the vascular wall after stent implantation, showing that the surface of the scaffold wire was a region of high shear force, while the shear force on the vascular wall was low. The scaffold locally causes turbulence, and the proximal end has high shear force, forming eddy currents. ［Adapted from: Farhad R et al. Hemodynamics in coronary arteries with overlapping stents［J］. J Biomech, 2014, 47（2）: 505-511.］