McEvoy Eoin, Holzapfel Gerhard A, McGarry Patrick
Department of Biomedical Engineering, National University of Ireland Galway, Galway H91 TK33, Ireland e-mail: .
Institute of Biomechanics, Graz University of Technology, Graz 8010, Austria.
J Biomech Eng. 2018 Aug 1;140(8). doi: 10.1115/1.4039947.
While the anisotropic behavior of the complex composite myocardial tissue has been well characterized in recent years, the compressibility of the tissue has not been rigorously investigated to date. In the first part of this study, we present experimental evidence that passive-excised porcine myocardium exhibits volume change. Under tensile loading of a cylindrical specimen, a volume change of 4.1±1.95% is observed at a peak stretch of 1.3. Confined compression experiments also demonstrate significant volume change in the tissue (loading applied up to a volumetric strain of 10%). In order to simulate the multiaxial passive behavior of the myocardium, a nonlinear volumetric hyperelastic component is combined with the well-established Holzapfel-Ogden anisotropic hyperelastic component for myocardium fibers. This framework is shown to describe the experimentally observed behavior of porcine and human tissues under shear and biaxial loading conditions. In the second part of the study, a representative volumetric element (RVE) of myocardium tissue is constructed to parse the contribution of the tissue vasculature to observed volume change under confined compression loading. Simulations of the myocardium microstructure suggest that the vasculature cannot fully account for the experimentally measured volume change. Additionally, the RVE is subjected to six modes of shear loading to investigate the influence of microscale fiber alignment and dispersion on tissue-scale mechanical behavior.
虽然近年来复杂复合心肌组织的各向异性行为已得到充分表征，但该组织的可压缩性迄今尚未得到严格研究。在本研究的第一部分，我们提供了实验证据，表明被动切除的猪心肌会出现体积变化。在圆柱形标本的拉伸载荷下，在峰值拉伸为1.3时观察到体积变化为4.1±1.95%。围压实验也证明了该组织中存在显著的体积变化（施加的载荷达到体积应变10%）。为了模拟心肌的多轴被动行为，将一个非线性体积超弹性分量与已确立的用于心肌纤维的霍尔扎佩尔 - 奥格登各向异性超弹性分量相结合。该框架被证明能够描述在剪切和双轴载荷条件下猪和人体组织的实验观察行为。在研究的第二部分，构建了一个具有代表性的心肌组织体积单元（RVE），以剖析组织脉管系统对围压载荷下观察到的体积变化的贡献。心肌微观结构的模拟表明，脉管系统不能完全解释实验测量的体积变化。此外，对RVE施加六种剪切载荷模式，以研究微观尺度纤维排列和分散对组织尺度力学行为的影响。
