A numerical study of a single isolated human ventricular cell response to a periodic pulse stimulus current using the Rogers–McCulloch model

Abstract

Among the primary causes of cardiac arrhythmias are abnormalities in the generation of action potentials (APs) by the cardiac cells, which may be induced by alterations in the electrophysiological properties of the cells as well as the stimuli delivered to them. Through numerical simulations using the phenomenological model of Rogers–McCulloch, this study examined how external stimuli modulate the electrical activity of a single isolated human ventricular cell functioning under normal conditions. First, we investigated how the initial conditions of the two model state variables affect how the cell responds to a single rectangular current pulse. This allows for the determination of a critical curve, which separates the initial conditions that allow for AP activation from those that inhibit it. This critical curve can be used to predict AP activation not only when the cell is stimulated by a single current pulse but also by a periodic stimulus. Then, we examined the cell response to a periodic train of rectangular current pulses, with a focus on the effects of the stimulus pacing length and amplitude. Our findings demonstrated that, despite not considering any alteration in the dynamics of ionic currents through the cell membrane, the Rogers–McCulloch model was capable of reproducing some of the most common activation patterns that have been widely identified in several clinical, experimental, and numerical studies. Depending on the stimulus properties, the following activation patterns were identified: (1) AP activation in synchrony with the stimulus, with one AP activation per pulse; (2) quasi-periodic and periodic Wenckebach-like patterns, in which successive AP activations are interrupted by a skipped beat; (3) completely irregular patterns; (4) abnormal potential oscillations that interrupt the repolarization of a previously activated AP, followed or not by a skipped beat; and (5) abnormal potential oscillations that completely inhibit cell repolarization.