Competing mechanisms of stress-assisted diffusivity and stretch-activated currents in cardiac electromechanics

We numerically investigate the role of mechanical stress in modifying the conductivityproperties of cardiac tissue, and also assess the impact of these effects in thesolutions generated by computational models for cardiac electromechanics. We followthe recent theoretical framework from Cherubini et al. (2017), proposed in the contextof general reaction-diffusion-mechanics systems emerging from multiphysics continuummechanics and finite elasticity. In the present study, the adapted models are comparedagainst preliminary experimental data of pig right ventricle fluorescence optical mapping.These data contribute to the characterization of the observed inhomogeneity andanisotropy properties that result from mechanical deformation. Our novel approachsimultaneously incorporates two mechanisms for mechano-electric feedback (MEF):stretch-activated currents (SAC) and stress-assisted diffusion (SAD); and we also identifytheir influence into the nonlinear spatiotemporal dynamics. It is found that (i) only specificcombinations of the two MEF effects allow proper conduction velocity measurement; (ii)expected heterogeneities and anisotropies are obtained via the novel stress-assisteddiffusion mechanisms; (iii) spiral wave meandering and drifting is highly mediated bythe applied mechanical loading. We provide an analysis of the intrinsic structure of thenonlinear coupling mechanisms using computational tests conducted with finite elementmethods. In particular, we compare static and dynamic deformation regimes in the onsetof cardiac arrhythmias and address other potential biomedical applications.