Simulation study of the ionic mechanisms involved in the all-or-none repolarization observed under ischemic conditions

Several studies in dog have suggested that a mild (simulated) ischemia produces an heterogeneous shortening of the action potentials (APs) in the epicardium, by means of the suppression of the dome only in some areas, giving place to what is known as all-or-none repolarization. This produces a different restitution curve in epicardium and endocardium. The goal of the present work is to study the ionic mechanisms responsible for the characteristic restitution curve of the epicardium under metabolic inhibition conditions. The study has been carried out by means of computer simulations, using a modified version of the model from Priebe and Beuckelmann for human myocytes. Metabolic inhibition was simulated activating the potassium ATP-dependent channels (I_KATP). Our results show that the activation of the I_KATP may account for the restitution curve observed in other studies. In this study 1% of this channels open produce the abolition of the dome for interstimulus intervals greater than 600 ms (BCL of 2000 ms)