Action potential duration inhomogeneities in acute myocardial ischemia: a simulation study

It is well known that spatial heterogeneity in the distribution of action potential duration (APD) is one of the conditions that set the stage for cardiac arrhythmias. Alternans in the APD induced by myocardial ischemia is one of the mechanisms that may provoke this dispersion. As the genesis of these alternans is not well understood, the authors have used computer simulation to study this phenomenon. The Luo-Rudy model for the cardiac action potential (AP), completed with a formulation of the ATP-sensitive K⁺ current, was used to simulate ischemic APs. Under certain conditions, alternating APs that resembled those observed experimentally were obtained. Analysis of individual ionic concentrations currents and gates suggested that small differences in intracellular Ca²⁺ concentrations in the onset of consecutive APs, together with a reduced cellular excitability, might be the cause of the electrical alternans