Adaptive reorientation of cardiac myofibers: the long-term effect of initial and boundary conditions

On the basis of results from modeling and experimental studies it has been hypothesized that myocytes adapt their orientation to achieve a preferred mechanical load. In a previous computational model study in which fiber reorientation was considered as a local response to local fiber cross-fiber shear strain, we have shown that predicted left ventricular (LV) myofiber orientations agreed well with experimental data. In this study, we investigated in the latter model the effect of initial and boundary conditions on predicted fiber orientations on the long term. After adaptation, predicted fiber orientation and deformation became more realistic, irrespective of initial and boundary conditions. As adaptation proceeded, the effect of initial conditions was found to disappear, suggesting that one single optimal fiber orientation field exists for the heart. In contrast, the effect of the boundary conditions persisted, indicating that modeling of in particular the interaction between myocardium and valvular annulus is relevant for predicting LV myofiber reorientation.