Role of the ATP-sensitive potassium current in extracellular potassium accumulation during myocardial ischemia: A simulation study

During acute myocardial ischemia, accumulation of K⁺ in the extracellular medium plays a major role in the development of reentrant arrhythmias. The Luo- Rudy (phase II) model for the ventricular action potencial, completed with the formulation of the I_K(ATP) by Ferrero et al., was used to simulate conditions of acute myocardial ischemia. A Na⁺-H⁺ countertransport was also formulated and introduced into the model to balance ion concentrations in normoxia. The I_K(ATP) current was activated during ten minutes of ischemia in a linear fashion from 0% to different maximum degrees. The effect of heart rate was studied considering different frecuencies of stimulation. Our results show that the maximal [K⁺]_o increment due to I_K(ATP) is less than 25% of the experimentally observed [K⁺]_o accumulation. These data support the hypothesis than other mechanisms must be responsible for the rest of the [K⁺]_o, increase.