Restitution of action potential duration at the Purkinje-ventricular interface

Regional differences in the restitution of action potential duration may be arrhythmogenic. Though such a difference exists at the Purkinje-ventricular interface, restitution kinetics have not yet been defined between coupled Purkinje and ventricular cells. Thus, the purpose of this study was to determine the effects of coupling on restitution in Purkinje and ventricular cells. DiFrancesco-Noble and Luo-Rudy dynamic membrane equations were used to describe the ionic currents for Purkinje and ventricular cells, respectively. During homogeneous coupling (e.g., Purkinje to Purkinje cell or ventricular to ventricular cell), the restitution kinetics of well-coupled cells were intermediate to the intrinsic restitution kinetics of each cells. However, during heterogeneous coupling between a Purkinje and a ventricular cell, the restitution kinetics of the coupled cells were not simply a weighted average of the intrinsic kinetics. These results suggest that restitution is strongly affected by cell-to-cell coupling. Because Purkinje and ventricular cells have intrinsic differences in restitution that are differentially altered by many pharmacological agents, these results have implications for proarrhythmic effects of some antiarrhythmic drugs.