Computer model of excitation and recovery in the anisotropic myocardium. I. Rectangular and cubic arrays of excitable elements

A computer model of propagated excitation and recovery in anisotropic cardiac tissue is presented that consists of a large number of excitable elements whose subthreshold interactions are governed by the anisotropic bidomain theory but whose suprathreshold behavior (action potential) is largely preassigned. The model's performance was first tested in a two-dimensional configuration with uniform anisotropy; this method allowed comparison of simulated isochrones of excitation and extracellular electrograms with the results of experimental in vitro studies of cardiac tissue. Next the model was used to study propagated excitation in a three-dimensional region representing the anisotropic properties of the ventricular wall, with attention to the effects produced by variable fiber direction from "endocardium" to "epicardium".