Propagation of depolarization and repolarization processes in the myocardium-an anisotropic model

A three-dimensional finite-elements model of the left and right ventricles has been developed to study the process of myocardial electrical activation. The anisotropic properties are demonstrated during simulation of an abnormal cardiac cycle, when propagating is initiated at an ectopic ventricular site. Ischemia is simulated by low conduction velocities in the ischemic zone and wide dispersion of values in nearby locations; automaticity is described by restimulating cells in the injured area; the dangerous effects of a premature beat leading to reentry are simulated by reduction of propagation velocity in cells that are reactivated while they repolarized. The different activation patterns are calculated throughout the myocardium and on its surface. The generated surface activation maps are not sensitive to minute changes in location of the foci of activation within the normal conduction system. The maps show sensitivity to pathological velocities, ischemic areas, and the existence of ectopic foci. Thus, the model, with its distributed properties, may be useful for electrocardiographic studies due to its low sensitivity to normal cell-to-cell variability, but high sensitivity to the existence of abnormally propagating myocardial activity.