Anssari-Benam Afshin, Tseng Yuan-Tsan, Holzapfel Gerhard A, Bucchi Andrea
Cardiovascular Engineering Research Laboratory (CERL), School of Mechanical and Design Engineering, University of Portsmouth, Anglesea Road, Portsmouth, PO1 3DJ, United Kingdom.
National Heart and Lung Institute, Heart Science Centre, Imperial College London, Middlesex, United Kingdom.
J Mech Behav Biomed Mater. 2020 Apr;104:103645. doi: 10.1016/j.jmbbm.2020.103645. Epub 2020 Jan 23.
In this study we investigate the rate-dependency of the mechanical behaviour of semilunar heart valves under biaxial deformation, from quasi-static to physiological loading rates. This work extends and complements our previous undertaking, where the rate-dependency in the mechanical behaviour of semilunar valve specimens was documented in sub-physiological rate domains (Acta Biomater. 2019; https://doi.org/10.1016/j.actbio.2019.02.008). For the first time we demonstrate herein that the stress-stretch curves obtained from specimens under physiological rates too are markedly different to those at sufficiently lower rates and at quasi-static conditions. The results importantly underline that the mechanical behaviour of semilunar heart valves is rate dependent, and the physiological mechanical behaviour of the valves may not be correctly obtained via material characterisation tests at arbitrary low deformation rates. Presented results in this work provide an inclusive dataset for material characterisation and modelling of semilunar heart valves across a 10,000 fold deformation rate, both under equi-biaxial and 1:3 ratio deformation rates. The important application of these results is to inform the development of appropriate mechanical testing protocols, as well as devising new models, for suitable determination of the rate-dependent constitutive mechanical behaviour of the semilunar valves.
在本研究中，我们研究了半月形心脏瓣膜在双轴变形下，从准静态到生理加载速率范围内力学行为的速率依赖性。这项工作扩展并补充了我们之前的研究，在之前的研究中，半月形瓣膜标本力学行为的速率依赖性是在低于生理速率的范围内记录的（《生物材料学报》，2019年；https://doi.org/10.1016/j.actbio.2019.02.008）。我们在此首次证明，在生理速率下从标本获得的应力-拉伸曲线与在足够低的速率和准静态条件下获得的曲线也明显不同。这些结果重要地强调了半月形心脏瓣膜的力学行为是速率依赖性的，并且瓣膜的生理力学行为可能无法通过在任意低变形速率下的材料表征测试正确获得。本工作中呈现的结果提供了一个全面的数据集，用于在等双轴和1:3比例变形速率下，跨越10000倍变形速率范围对半月形心脏瓣膜进行材料表征和建模。这些结果的重要应用是为制定合适的力学测试方案以及设计新模型提供依据，以便适当地确定半月形瓣膜的速率依赖性本构力学行为。
