Effect of fiber geometry on pulsatile pumping and energy expenditure.

Myocardial fiber orientation is a topic that has recently received much attention in connection with cardiac pumping function. The twisting motion of the cardiac base to apex can be a direct result of this geometric orientation of these fibers. One important question that has not been addressed yet is whether there is any relationship between the contractile energy expenditure and the geometric orientation of myocardial fibers. In the present work, we study the effect of contractile fiber orientation on pumping function. We particularly compare the effect of fiber geometry on ejection fraction, and on the energy required for contraction in both cylindrical and half-ellipsoid shell models. The analytical models we used signify the importance of twisting motion in minimizing the energy required to generate certain ejection fraction. Indeed, we quantified that if the angle of contractile fibers is appropriate for the shape and the size of the pump, twisting scheme can tremendously reduce the energy requirement for pumping.