Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.
Graduate School of Systems Design, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji, Tokyo, 192-0397, Japan.
Ann Biomed Eng. 2021 Jul;49(7):1670-1687. doi: 10.1007/s10439-020-02706-7. Epub 2021 Feb 11.
Despite numerous experimental observations regarding heart failure with preserved ejection fraction (HFpEF), which is characterized mainly by left ventricular hypertrophy and a left ventricular ejection fraction over 50%, myocardial dynamics under HFpEF have not yet been fully clarified, particularly regarding the relationship between myocardial strain distribution and myocardial work. To address this issue, we numerically investigated radial distribution of myocardial strain during a cardiac cycle with fixed internal volume at the end of the systolic and diastolic phases under different mechanical conditions, such as those involving myocardial thickness and elasticity of myocardial fibers. The myocardium was a modeled as a visco-hyperelastic continuous material. This model was taken into account that active contractile stress along the myocardial fiber direction depends on membrane potential change. Our numerical results showed that both radial and circumferential strains decreased as wall thickness increased, which reflected cardiac hypertrophy, but that myocardial work became larger than that observed with thin ventricular walls. Further, the change in left ventricular diastolic internal pressure caused circumferential strain, while fiber stiffness contributed to radial strain. Since peak circumferential strain was well estimated by the maximum difference between total internal and myocardial volumes, measuring the epicardial contraction rate should be helpful in understanding patients with HFpEF.
尽管有许多关于射血分数保留的心力衰竭（HFpEF）的实验观察，其主要特征是左心室肥厚和左心室射血分数超过 50%，但 HFpEF 下的心肌动力学尚未完全阐明，特别是心肌应变分布与心肌做功之间的关系。为了解决这个问题，我们在不同的力学条件下，如心肌厚度和心肌纤维弹性，数值研究了收缩期和舒张期末期固定内部容积的心脏周期中心肌应变的径向分布。心肌被建模为粘弹性连续材料。该模型考虑到了沿心肌纤维方向的主动收缩力取决于膜电位的变化。我们的数值结果表明，随着壁厚度的增加，径向应变和周向应变都减小，这反映了心脏肥大，但心肌做功比薄壁心室观察到的更大。此外，左心室舒张内压的变化引起周向应变，而纤维刚度则导致径向应变。由于总内部体积和心肌体积之间的最大差值很好地估计了峰值周向应变，因此测量心外膜收缩率有助于理解 HFpEF 患者。
