Dependence of the Left Ventricular Ejection Fraction on the Myocardial Fiber Orientation in the Mechanical Model

The paper is devoted to a key indicator of the human cardiac performance, namely to the left ventricular ejection fraction (LVEF). The behavior of the LVEF as a function of two model features is investigated. Action potential duration (APD) in cardiomyocytes and myocardial fiber orientation in the ventricular wall were chosen as variable parameters that may influence on the ejection fraction. In our in-silico study, a simple electro-mechanical model of the human LV, that qualitatively reproduces electrophysiological and mechanical properties of the myocardium, is used. This work is performed using a population of models approach. It is observed that the parameters of fiber orientation in the structurally normal heart are near to optimal values providing for maximal cardiac performance. An increase in the action potential duration in a wide range leads to an increase in the ejection fraction, while there is an saturation point in the dependency, and a more significant increase in APD leads to the inverse effect.