Electrical activity and reentry in acute regional ischemia: insights from simulations

In this work, the authors use computer modeling to investigate the mechanisms in figure-of-eight reentry ( a pattern of excitation which may lead to ventricular fibrillation and sudden cardiac death) during the acute phase or regional myocardial ischemia. For this purpose, a modified version of the Luo-Rudy dynamic model for the action potential and ionic currents was used, together with a two-dimensional model of the regionally ischemic ventricle. The virtual tissue comprises different realistically dimensioned transitional border zones for hyperkalemia, hypoxia and acidosis, simulating the substrate heterogeneity created by acute ischemia. Different types of patterns of excitation following the delivery of a premature stimulus were obtained, including figure-of-eight reentry. The effect of the degree of ATP-sensitive current activation, the severity of acidosis and the degree of hyperkalemia in the vulnerability to reentry were also studied. The results are in accordance with experimental observations, and demonstrate the ability of second-generation mathematical models to analyze and explain the mechanisms involved in ischemic reentry.