Simulation study of epicardial action potential under normal and ischemic conditions

A computer model has been used to simulate the effects of activation of the ATP sensitive K/sup +/ channels on the action potential morphology and duration of canine-type epicardial myocytes. Simulations were based on a modified version of the Luo-Rudy mammalian action potential model. The authors' formulation of I/sub KATP/ and the transient outward current (I/sub to/) were included in this model. Their results show that the same fraction of open K-ATP channels has a more pronounced effect in epicardium than in endocardium. They conclude that the presence of a prominent outward current in epicardial but not in endocardial myocytes increases the APD reduction produced by the activation of the K-ATP channels and thus contributes to the dispersion of APD observed under ischemic conditions.