The aim of this study was to elucidate the effects of myocardial fiber orientation on the deformation of the left ventricular (LV) wall. An LV wall model was constructed by modeling the myocardial fiber structure as an anisotropic hyperelastic material. The shapes of the endocardium and epicardium were assumed to be two spheroids. LV wall deformation by constriction of the myocardial fibers was simulated for three fiber orientations:the myocardial fiber was oriented parallel to the short-axis plane (Case 1) ; the angle between the myocardial fiber and the short-axis plane varied linearly from +π/3 in the endocardium to -π/3 in the epicardium (Case 2) ; and the myocardial fiber was uniformly oriented at an angle of -π/3 with respect to the short-axis plane (Case 3). The results showed that the LV wall deformation was governed by the interaction among the constriction of fibers, the wall deformation as a continuum body, and the geometric constrains of the LV anatomy. Comparing the results of three cases revealed that the helical structure of fibers contributes to cause a twisting motion and efficient contraction of the LV wall, which produces a heterogeneous distribution of the deformation rates in the LV wall.
