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 potential, completed with the formulation of the I_K(ATP) by Ferrero et al. (1996), 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 frequencies of stimulation. The authors´ results show that the maximal [K⁺]₀ increment due to I_K(ATP) is less than 25% of the experimentally observed [K ⁺]₀ accumulation. These data support the hypothesis than other mechanisms must be responsible for the rest of the [K⁺]₀ increase