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stract-Regional differences in the restitution of action tential duration may be arrhythmogenic. Though such a fference exists at the Purkinje-ventricular interface, restitution netics have not yet been defined between coupled Purkinje and ntricular cells. Thus, the purpose of this study was to termine the effects of coupling on restitution in Purkinje and ntricular cells. DiFrancesco-Noble and Luo-Rudy dynamic embrane equations were used to describe the ionic currents for rkinje and ventricular cells, respectively. During mogeneous coupling (e.g., Purkinje to Purkinje cell or ntricular to ventricular cell), the restitution kinetics of wellupled cells were intermediate to the intrinsic restitution netics of each cells. However, during heterogeneous coupling tween a Purkinje and a ventricular cell, the restitution netics of the coupled cells were not simply a weighted average the intrinsic kinetics. These results suggest that restitution is ongly affected by cell-to-cell coupling. Because Purkinje and ntricular cells have intrinsic differences in restitution that are fferentially altered by many pharmacological agents, these sults have implications for proarrhythmic effects of some tiarrhythmic drugs. ywords DiFrancesco-Noble, Luo-Rudy dynamic membrane uations