The effect of repair techniques on the biomechanics of the aorta is poorly understood, resulting in significant levels of postoperative complications for patients worldwide. This study presents a computational analysis of the influence of Nitinol-based devices on the biomechanical performance of a healthy patient-specific human aorta. Simulations reveal that Nitinol stent-grafts stretch the artery wall so that collagen is stretched to a straightened high-stiffness configuration. The high-compliance regime (HCR) associated with low diastolic lumen pressure is eliminated, and the artery operates in a low-compliance regime (LCR) throughout the entire cardiac cycle. The slope of the lumen pressure-area curve for the LCR post-implantation is almost identical to that of the native vessel during systole. This negligible change from the native LCR slope occurs because the stent-graft increases its diameter from the crimped configuration during deployment so that it reaches a low-stiffness unloading plateau. The effective radial stiffness of the implant along this unloading plateau is negligible compared to the stiffness of the artery wall. Provided the Nitinol device unloads sufficiently during deployment to the unloading plateau, the degree of oversizing has a negligible effect on the pressure-area response of the vessel, as each device exerts approximately the same radial force, the slope of which is negligible compared to the LCR slope of the native artery. We show that 10% oversizing based on the observed diastolic diameter in the mid descending thoracic aorta results in a complete loss of contact between the device and the wall during systole, which could lead to an endoleak and stent migration. 20% oversizing reaches the Dacron enforced area limit (DEAL) during the pulse pressure and results in an effective zero-compliance in the later portion of systole.

中文翻译：

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形状记忆支架移植物对局部主动脉顺应性的影响。

修复技术对主动脉生物力学的影响知之甚少，导致全世界患者出现大量术后并发症。本研究对基于镍钛诺的设备对健康患者特异性人体主动脉的生物力学性能的影响进行了计算分析。模拟显示，镍钛诺支架移植物拉伸动脉壁，使胶原蛋白被拉伸到拉直的高刚度配置。消除了与低舒张管腔压力相关的高顺应性制度 (HCR)，并且动脉在整个心动周期中以低顺应性制度 (LCR) 运行。LCR 植入后的管腔压力-面积曲线的斜率几乎与收缩期天然血管​​的斜率相同。与原生 LCR 斜率相比，这种可忽略不计的变化发生是因为支架移植物在部署期间从卷曲配置增加了其直径，因此它达到了低刚度卸载平台。与动脉壁的刚度相比，沿此卸载平台的植入物的有效径向刚度可以忽略不计。如果镍钛诺装置在部署到卸载平台期间充分卸载，尺寸过大的程度对容器的压力区域响应的影响可以忽略不计，因为每个装置施加大致相同的径向力，其斜率与原生动脉的 LCR 斜率。我们表明，根据观察到的胸主动脉中部舒张期直径过大 10% 会导致收缩期设备与管壁之间完全失去接触，这可能导致内漏和支架迁移。20% 的超大尺寸在脉压期间达到了涤纶强制面积限制 (DEAL)，并导致在收缩后期有效的零顺应性。