Simulation of reentry induced by early afterdepolarizations during acute myocardial ischemia

Computer simulations were used to study the conditions which lead to the appearance of ectopic foci and to their propagation as re-entrant activity in partially ischemic tissue. To simulate action potentials, we used a modified version of the Luo-Rudy-II model (C.H. Luo & Y. Rudy, 1994), completed with the formulation of the ATP-sensitive potassium current [I/sub K(ATP)/] by J.M. Ferrero et al. (1996). The tissue was simulated as a ring-shaped structure comprising four different regions: early after-depolarizations (EADs), normal zone (NZ), ischemic zone (IZ) and border zone (BZ). Our results show that, when the length of each BZ is 2 mm, [K]/sub 0/ is 13.5 mmol/l and the length of the NZ is more than 26 mm (260 cells), then ectopic beats appear in the EAD region and they propagate along the tissue, causing re-entry, regardless of the length of the NZ. In conclusion, our theoretical study shows that the co-existence of EAD-condition zones and regional ischemia could set the stage for the appearance of ectopic foci and re-entry.