Heart composite material model for stress-strain analysis

Mechanical properties of the myocardium have been investigated intensively in the past four decades. Due to the non-linearity and history dependence of myocardial deformation, many complex strain energy functions have been used to describe the stress-strain relationship in the myocardium. These functions are good at fitting in-vitro experimental data from myocardial stretch testing into strain energy functions. However, it is difficult to model in-vivo myocardium by using strain energy functions. In a previous paper [1], we have implemented a transversely anisotropic material model to estimate in-vivo strain and stress in the myocardium. In this work, the fiber orientation is updated at each time step from the end of diastole to the end of systole; the stiffness matrix is recalculated using the current fiber orientation. We also extend our model to include residual ventricular stresses and time-dependent blood pressure in the ventricular cavities.