Simulation study of electrical alternans in epicardial myocytes under ischemic conditions

Several studies have shown that cardiac action potentials present an alternating behaviour during acute myocardial ischemia that creates spatial and temporal inhomogeneities which may predispose the myocardium to arrhythmias caused by reentry. The goal of the present work is to study the mechanisms responsible for the electrical alternans during acute ischemia and to analyse the role of the transient outward current in the generation of arrhythmic episodes. The study has been carried out by means of computer simulations, using a mortified version of the model from Priebe and Beuckelmann (1998) for human myocytes. The three main components of ischemia (metabolic inhibition, hyperkalemia and acidosis) were simulated. The authors' results show that the intracellular calcium transients may play a major role in the electrical alternation of both endocardium and epicardium, and suggest that the presence of a prominent transient outward current in epicardium plays an important role in the generation of reentrant-type arrhythmias.