Chen Winson X, Poon Eric K W, Thondapu Vikas, Hutchins Nicholas, Barlis Peter, Ooi Andrew
Department of Mechanical Engineering, Melbourne School of Engineering, The University of Melbourne, Victoria 3010, Australia.
Department of Mechanical Engineering, Melbourne School of Engineering, The University of Melbourne, Victoria 3010, Australia.
J Biomech. 2017 Oct 3;63:164-173. doi: 10.1016/j.jbiomech.2017.09.016. Epub 2017 Sep 27.
Incomplete stent apposition (ISA, also known as malapposition) is a complication that affects day-to-day coronary stenting procedures. ISA is more prominent in complex arterial geometries, such as curvature, asa result of the limited conformability of coronary stents. These malapposed struts disturb the otherwise near-wall laminar blood flow and form a micro-recirculation environment. The micro-recirculation environment is often associated with low wall shear stress (WSS) and upsets the delicate balance of vascular biology, providing possible nidus for thrombosis and restenosis. In this study, a three-dimensional (3D) stent model was virtually deployed into an idealised curved coronary artery. Computational fluid dynamics (CFD) simulations were carried out to systematically analyse the haemodynamic effects of increasing maximum ISA distances, ranging from 180 (moderate), 400 (intermediate) to 910μm (severe) in an artery with decreasing radius of curvature (ROC). Micro-recirculations around both proximal and distal malapposed struts become more pronounced as compared to fully-apposed struts. The accompanying areas of low temporally-averaged WSS (AL-TAWSS) can increase twofold compared to the fully-apposed condition. Furthermore, substantial regions (∼5.2% and 9.0%) of AL-TAWSS are detached from the distal end of the malapposed struts in both moderate and intermediate cases respectively. Malapposed stents also induce more variation of TAWSS at the inner bend of the artery. At the stent surface, maximum WSS increases threefold from the fully-apposed case to intermediate ISA. High WSS on the strut surface is known to activate platelets which when exposed to the micro-recirculation environment may lead to their deposition and thrombosis.
不完全支架贴壁（ISA，也称为贴壁不良）是一种影响日常冠状动脉支架置入手术的并发症。由于冠状动脉支架的顺应性有限，ISA在复杂的动脉几何形状（如弯曲处）中更为突出。这些贴壁不良的支柱扰乱了原本近壁的层流，并形成了一个微循环环境。微循环环境通常与低壁面切应力（WSS）相关联，打破了血管生物学的微妙平衡，为血栓形成和再狭窄提供了可能的病灶。在本研究中，一个三维（3D）支架模型被虚拟地植入到一个理想化的弯曲冠状动脉中。进行了计算流体动力学（CFD）模拟，以系统分析在曲率半径（ROC）减小的动脉中，最大ISA距离从180μm（中度）、400μm（中度）增加到910μm（重度）时的血流动力学效应。与完全贴壁的支柱相比，近端和远端贴壁不良支柱周围的微循环变得更加明显。与完全贴壁情况相比，伴随的低时间平均WSS（AL-TAWSS）区域可增加两倍。此外，在中度和中度情况下，分别有相当大的区域（约5.2%和9.0%）的AL-TAWSS从贴壁不良支柱远端分离。贴壁不良的支架还会在动脉内弯处引起TAWSS的更多变化。在支架表面，最大WSS从完全贴壁情况到中度ISA增加了两倍。已知支柱表面的高WSS会激活血小板，当暴露于微循环环境时，可能导致血小板沉积和血栓形成。
