Cellular responses to electrical stimulation: a study using a model of the ventricular cardiac action potential.

A mathematical model of the membrane action potential of a ventricular cardiac cell is used to examine the cellular responses to premature stimulation. Results demonstrate the importance of the slow recovery of INa in determining the response of the cell. Simulated responses to periodic stimulation include monotonic Wenckebach patterns and alternans in APD at normal [K]O. At low [K]O, nonmonotonic Wenckebach periodicities, aperiodic patterns, and enhanced supernormal excitability that results in unstable responses ("chaotic activity") are observed. These observations are consistent with recent experimental results, and the simulations provide insights into the underlying mechanisms at the level of membrane ionic channel kinetics.