ИСТИНА

The study presents an axisymmetric model of the left ventricle (LV) of the heart in the circulatory system. The LV was approximated by a body of rotation, and the properties of the material of the ventricular wall were described by a new electromechanical model of the myocardium. Atria, the right ventricle, and the blood vessels of the systemic and pulmonary circulation were represented by a lumped parameter model. The active mechanical stresses in the models depend on biochemical parameters described by the system of ordinary differential equations. Myocardial electrophysiology is described by a simple model with two variables. Despite the simplifications, the model correctly reproduces the dynamics of electrical excitation and mechanical contraction of the myocardium in various scenarios, including the dependence of the developed force on time between adjacent electrical stimuli allowing one to simulate correctly variations of stress and strain of the LV wall in response to a change its conductivity or stimulation frequency. The major variables of the system hemodynamics were calculated under various scenarios: at rest; during physical activity modeled by increasing the heart rate from 60 to 120 beats per minute and reducing the peripheral blood resistance in the systemic circulation; at atrioventricular blockade, simulated by a skip of one ventricular contraction per four atrial contractions, and acute myocardial infarction of the LVs apex. The results demonstrate a significant increase in the LV contractility with an increase in heart beat rate as well as the ability of the LV to partially compensate loss of blood flow and arterial pressure in the case of an atrioventricular blockade due to an increase in ventricular contractility in the contraction following the missed one. The results also indicate that a decrease in the LV apex conductance in the case of apical infarction decreases the LV performance. All results correspond to empirical data. The research was supported by RSF grant 20-74-00046.