Guan Debao, Yao Jiang, Luo Xiaoyu, Gao Hao
School of Mathematics & Statistics, University of Glasgow, Glasgow, UK.
Dassault Systemes, Johnston, RI, USA.
R Soc Open Sci. 2020 Apr 8;7(4):191655. doi: 10.1098/rsos.191655. eCollection 2020 Apr.
Myofibre architecture is one of the essential components when constructing personalized cardiac models. In this study, we develop a neonatal porcine bi-ventricle model with three different myofibre architectures for the left ventricle (LV). The most realistic one is derived from diffusion tensor magnetic resonance imaging, and other two simplifications are based on rule-based methods (RBM): one is regionally dependent by dividing the LV into 17 segments, each with different myofibre angles, and the other is more simplified by assigning a set of myofibre angles across the whole ventricle. Results from different myofibre architectures are compared in terms of cardiac pump function. We show that the model with the most realistic myofibre architecture can produce larger cardiac output, higher ejection fraction and larger apical twist compared with those of the rule-based models under the same pre/after-loads. Our results also reveal that when the cross-fibre contraction is included, the active stress seems to play a dual role: its sheet-normal component enhances the ventricular contraction while its sheet component does the opposite. We further show that by including non-symmetric fibre dispersion using a general structural tensor, even the most simplified rule-based myofibre model can achieve similar pump function as the most realistic one, and cross-fibre contraction components can be determined from this non-symmetric dispersion approach. Thus, our study highlights the importance of including myofibre dispersion in cardiac modelling if RBM are used, especially in personalized models.
肌纤维结构是构建个性化心脏模型时的重要组成部分之一。在本研究中，我们开发了一种新生猪双心室模型，其左心室（LV）具有三种不同的肌纤维结构。最逼真的一种源自扩散张量磁共振成像，另外两种简化结构基于基于规则的方法（RBM）：一种是通过将左心室分为17个节段，每个节段具有不同的肌纤维角度，从而实现区域依赖性，另一种则通过在整个心室中分配一组肌纤维角度来进行更简化的处理。从心脏泵功能方面比较了不同肌纤维结构的结果。我们表明，在相同的前/后负荷下，具有最逼真肌纤维结构的模型相比基于规则的模型能够产生更大的心输出量、更高的射血分数和更大的心尖扭转。我们的结果还表明，当纳入跨纤维收缩时，主动应力似乎发挥双重作用：其片层法线分量增强心室收缩，而其片层分量则起相反作用。我们进一步表明，通过使用一般结构张量纳入非对称纤维离散度，即使是最简化的基于规则的肌纤维模型也能实现与最逼真模型相似的泵功能，并且可以从这种非对称离散度方法中确定跨纤维收缩分量。因此，我们的研究强调了在使用基于规则的方法进行心脏建模时，尤其是在个性化模型中，纳入肌纤维离散度的重要性。
