Development of biomechanical models incorporating microstructures for vascular tissue rupture and implant design optimization

开发包含血管组织破裂微结构和植入物设计优化的生物力学模型

• 批准号: 217183-2013
• 负责人: Mongrain, Rosaire
• 金额: $ 2.7万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=638530
• 关键词: Development; biomechanical; models; incorporating; microstructures

Vascular tissue rupture is a common phenomenon associated with many catastrophic cardiovascular diseases including coronary plaque rupture, aortic dissection and aortic aneurysm rupture. Biomechanical criteria based on peak stress have been proposed to assess the severity of the diseases and the potential of rupture. However, these indexes cannot account for all observed ruptures. For example, for coronary plaque rupture, the conventional load analysis which predicts stress concentration at the plaque shoulders cannot account for about 30 % of the ruptures occurring in the mid portion of the plaque. In fact, peak stress predominates so much the literature that certain results have essentially become paradigms (rupture at plaque shoulders). The fact is that the biomechanics of vascular tissue rupture is incompletely understood. There is a need for a better model capable of explaining the various clinically observed ruptures. A core hypothesis is that toughness (resistance to tear) is the principal physical criterion governing vascular tissue rupture and that diseased vessels present microstructure alterations (plaque inclusions, medial degeneration, collagen degradation) that constitute flaws that can induce a crack propagation causing rupture. It is proposed to use the new micro-indenter just obtained with a NSERC RTI to directly measure the inherent mechanical properties of the plaque microstructures (fibrous cap, inclusions) and aortic tissue wall alterations (medial degeneration). In analogy with endurance S-N curve, a toughness exhaustion J-N curve is proposed. The shape of the experimental J-N curves can be fitted with functions of exponential type and allows for extrapolating the number of cycles required to reach a certain threshold of toughness at which the tissue would rupture. To the best of the applicant's knowledge, the concept of toughness exhaustion has not been applied to vascular tissue. Finally, the toughness concept will be used to identify the conditions associated with injuries sometimes caused by implants. Indeed, vascular implants interact with the vascular tissue and for unclear reasons can induce injuries. This would constitute the first design methodology incorporating the microstructure and the tissue mesoscale (cells agglomeration).

血管组织破裂是与许多灾难性心血管疾病相关的常见现象，包括冠状动脉斑块破裂、主动脉夹层和主动脉瘤破裂。已提出基于峰值应力的生物力学标准来评估疾病的严重程度和破裂的可能性。然而，这些指数不能解释所有观察到的破裂。例如，对于冠状动脉斑块破裂，预测斑块肩部处的应力集中的传统载荷分析不能解释斑块中部发生的破裂的约30%。事实上，峰值应力在文献中占主导地位，以至于某些结果基本上已经成为范例（斑块肩部破裂）。事实上，血管组织破裂的生物力学尚未完全了解。需要一种更好的模型来解释临床上观察到的各种破裂。一个核心假设是韧性（抗撕裂性）是控制血管组织破裂的主要物理标准，病变血管存在微结构改变（斑块夹杂物、中膜变性、胶原降解），这些微结构改变构成可诱导裂纹扩展导致破裂的缺陷。建议使用刚通过NSERC RTI获得的新型微型压头直接测量斑块微结构（纤维帽、内含物）和主动脉组织壁改变（中膜变性）的固有机械性能。与疲劳S-N曲线相似，提出了韧性耗竭J-N曲线。实验J-N曲线的形状可以用指数型函数拟合，并且允许外推达到组织将破裂的韧性的某个阈值所需的循环次数。据申请人所知，韧性耗尽的概念尚未应用于血管组织。最后，韧性概念将用于识别与植入物有时引起的损伤相关的条件。事实上，血管植入物与血管组织相互作用，并且由于不清楚的原因可能引起损伤。这将构成第一个结合微观结构和组织中尺度（细胞聚集）的设计方法。