Institute for Medical Engineering & Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Building E25-442, Cambridge, MA, 02139, USA.
Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering 'Giulio Natta', Politecnico di Milano, Milan, Italy.
Ann Biomed Eng. 2021 May;49(5):1298-1307. doi: 10.1007/s10439-020-02673-z. Epub 2020 Oct 29.
Bioresorbable vascular scaffolds were considered the fourth generation of endovascular implants deemed to revolutionize cardiovascular interventions. Yet, unexpected high risk of scaffold thrombosis and post-procedural myocardial infractions quenched the early enthusiasm and highlighted the gap between benchtop predictions and clinical observations. To better understand scaffold behavior in the mechanical environment of vessels, animal, and benchtop tests with multimodal loading environment were conducted using industrial standard scaffolds. Finite element analysis was also performed to study the relationship among structural failure, scaffold design, and load types. We identified that applying the combination of bending, axial compression, and torsion better reflects incidence observed in-vivo, far more than tranditional single mode loads. Predication of fracture locations is also more accurate when at least bending and axial compression are applied during benchtop tests (>60% fractures at connected peak). These structural failures may be initiated by implantation-induced microstructural damages and worsened by cyclic loads from the beating heart. Ignoring the multi-modal loading environment in benchtop fatigue tests and computational platforms can lead to undetected potential design defects, calling for redefining consensus evaluation strategies for scaffold performance. With the robust evaluation strategy presented herein, which exploits the results of in-vivo, in-vitro and in-silico investigations, we may be able to compare alternative designs of prototypes at the early stages of device development and optimize the performance of endovascular implants according to patients-specific vessel dynamics and lesion configurations in the future.
生物可吸收血管支架被认为是第四代血管内植入物，有望彻底改变心血管介入治疗。然而，支架血栓形成和术后心肌梗死的高风险超出预期，这使得人们对该技术的早期热情冷却下来，也凸显了实验室预测与临床观察之间的差距。为了更好地了解支架在血管的力学环境中的行为，我们使用工业标准的支架进行了动物和台架测试，并采用多模态加载环境。还进行了有限元分析，以研究结构失效、支架设计和载荷类型之间的关系。我们发现，施加弯曲、轴向压缩和扭转的组合能更好地反映体内观察到的情况，比传统的单一模式负荷更有效。当在台架测试中施加至少弯曲和轴向压缩时（>60%的骨折发生在连接峰值处），对骨折部位的预测也更准确。这些结构失效可能是由植入引起的微结构损伤引发的，并因心脏跳动产生的循环载荷而恶化。在台架疲劳试验和计算平台中忽略多模态加载环境，可能会导致潜在设计缺陷未被发现，因此需要重新定义支架性能的共识评估策略。通过本文提出的稳健评估策略，利用体内、体外和计算机模拟研究的结果，我们或许能够在设备开发的早期阶段比较不同原型设计，并根据患者特定的血管动力学和病变配置来优化血管内植入物的性能。
