Computer simulation of re-entry sources in myocardium in two and three dimensions.

Re-entry in a simple model of cardiac muscle is examined. The properties of vortices in two dimensions are studied at different values of the ratio of the action potential duration to its rise time. The vortex changes from stationary to non-stationary rotation as the action potential duration is increased. A test for identifying non-stationary rotation from monophasic action potential recordings at a single site in cardiac tissue is proposed. In three dimensions re-entry of the scroll ring type is examined. Contraction of the scroll ring and its vertical drift occurs in this model. The drift velocities are shown to depend inversely on the scroll ring radius. The dependence of these drift velocities on re-entry cycle length is estimated for cardiac tissue.