Department of Biomedical Engineering, Technische Universiteit Eindhoven, Eindhoven, The Netherlands.
Department of Mathematics, University of North Carolina, Chapel Hill, North Carolina.
Int J Numer Method Biomed Eng. 2018 Dec;34(12):e3137. doi: 10.1002/cnm.3137. Epub 2018 Oct 7.
Models for cardiac mechanics require an activation mechanism properly representing the stress-strain relations in the contracting myocardium. In this paper, we propose a new activation model that accounts for the transmural heterogeneities observed in myocardial strain measurements. In order to take the anisotropy of the active mechanics into account, our model is based on an active strain formulation. Thanks to multiplicative decomposition of the deformation gradient tensor, in this formulation, the active strains orthogonal to the fibers can be naturally described. We compare the results of our novel formulation against different anisotropic models of the active contraction of the cardiac muscle, as well as against experimental data available in the literature. We show that with the currently available models, the strain distributions are not in agreement with the reported experimental measurements. Conversely, we show that our new transmurally heterogeneous orthotropic activation model improves the accuracy of shear strains related to in-plane rotations and torsion.
心脏力学模型需要一种激活机制，该机制能够正确表示收缩心肌中的应力-应变关系。在本文中，我们提出了一种新的激活模型，该模型考虑了心肌应变测量中观察到的跨壁异质性。为了考虑主动力学的各向异性，我们的模型基于主动应变公式。由于变形梯度张量的乘法分解，在该公式中，可以自然地描述与纤维正交的主动应变。我们将我们的新公式的结果与心肌主动收缩的不同各向异性模型以及文献中可用的实验数据进行了比较。我们表明，使用当前可用的模型，应变分布与报道的实验测量结果不一致。相反，我们表明，我们新的跨壁各向异性正交激活模型提高了与平面内旋转和扭转相关的剪切应变的准确性。
