Simulation of action potential propagation block on a bidimensional ventricular tissue model during regional myocardial ischaemia

During the acute phase of myocardial ischaemia, electrophysiological alterations in ventricular cells exacerbate serious arrhythmias such as reentries. Indeed, extracellular potassium accumulation in an ischaemic zone reduces conduction velocity. Concomitantly, the activation of ATP dependent potassium current (I_K(ATP)) under ischaemic conditions provokes a reduction in action potential duration (APD), creating inhomogeneities within the tissue, which represent the main cause of unidirectional block and reentry. In this work, we investigate the patterns of activation in an isotropic ischaemic bidimensional tissue by means of computer simulations. Using the Luo-Rudy phase II model of ventricular action potential and the I_K(ATP) formulation, we stimulated prematurely a bidimensional tissue of 5 cm² with a normal zone, an ischaemic zone and a border zone at different instants of time, to reproduce realistic conditions of reentry. Our results agree with experimental works and show the existence of a time interval (window of block), in which propagation is blocked in the central zone of ischaemia.