A generic cardiac biventricular fluid-electromechanics model

We present a fully-coupled fluid-electromechanics model of the heart using a generic biventricular structure to provide a tool for future multiphysics interaction studies. A simplified Purkinje fibre structure was embedded within the myocardium along with transmural variation of action potential duration to obtain realistic activation and relaxation sequences. To ease computational requirements, phenomenological action potential and excitation-contraction formulations were chosen, and coupled to transverse isotropic hyperelastic myocardial material physics. The action potential propagation was discretised within the material frame to achieve electromechanical coupling with gap junction-controlled propagation. Blood haemodynamics was represented by incompressible Navier-Stokes equations, whereby, the endocardial displacement deforms the blood domain, whilst blood pressure and viscous stress exert load on the myocardium. Realistic electrical activation and relaxation sequences were achieved along with basic cardiac mechanical properties such as torsion and apex displacement. The pressure-volume loops for both ventricles matched known values, and vortex formation was noted during the filling phase. The model could facilitate a better understanding of multiphysics and biventricular interactions under pathologic conditions and help formulate better treatments.