Loppini Alessandro, Gizzi Alessio, Ruiz-Baier Ricardo, Cherubini Christian, Fenton Flavio H, Filippi Simonetta
Unit of Nonlinear Physics and Mathematical Modeling, Department of Engineering, University Campus Bio-Medico of Rome, Rome, Italy.
Mathematical Institute, University of Oxford, Oxford, United Kingdom.
Front Physiol. 2018 Dec 3;9:1714. doi: 10.3389/fphys.2018.01714. eCollection 2018.
We numerically investigate the role of mechanical stress in modifying the conductivity properties of cardiac tissue, and also assess the impact of these effects in the solutions generated by computational models for cardiac electromechanics. We follow the recent theoretical framework from Cherubini et al. (2017), proposed in the context of general reaction-diffusion-mechanics systems emerging from multiphysics continuum mechanics and finite elasticity. In the present study, the adapted models are compared against preliminary experimental data of pig right ventricle fluorescence optical mapping. These data contribute to the characterization of the observed inhomogeneity and anisotropy properties that result from mechanical deformation. Our novel approach simultaneously incorporates two mechanisms for mechano-electric feedback (MEF): stretch-activated currents (SAC) and stress-assisted diffusion (SAD); and we also identify their influence into the nonlinear spatiotemporal dynamics. It is found that (i) only specific combinations of the two MEF effects allow proper conduction velocity measurement; (ii) expected heterogeneities and anisotropies are obtained via the novel stress-assisted diffusion mechanisms; (iii) spiral wave meandering and drifting is highly mediated by the applied mechanical loading. We provide an analysis of the intrinsic structure of the nonlinear coupling mechanisms using computational tests conducted with finite element methods. In particular, we compare static and dynamic deformation regimes in the onset of cardiac arrhythmias and address other potential biomedical applications.
我们通过数值方法研究了机械应力在改变心脏组织电导率特性中的作用，并评估了这些效应在心脏机电学计算模型所生成的解中的影响。我们遵循了Cherubini等人（2017年）提出的最新理论框架，该框架是在多物理场连续介质力学和有限弹性产生的一般反应扩散力学系统背景下提出的。在本研究中，将经过调整的模型与猪右心室荧光光学映射的初步实验数据进行了比较。这些数据有助于表征由机械变形导致的观察到的不均匀性和各向异性特性。我们的新方法同时纳入了两种机电反馈（MEF）机制：牵张激活电流（SAC）和应力辅助扩散（SAD）；并且我们还确定了它们对非线性时空动力学的影响。研究发现：（i）只有两种MEF效应的特定组合才能进行适当的传导速度测量；（ii）通过新的应力辅助扩散机制获得了预期的不均匀性和各向异性；（iii）螺旋波的蜿蜒和漂移受到所施加机械负荷的高度介导。我们使用有限元方法进行计算测试，对非线性耦合机制的内在结构进行了分析。特别是，我们比较了心律失常发作时的静态和动态变形状态，并探讨了其他潜在的生物医学应用。
