Effects of acute ischemia on the restitution curves of myocardial tissue: a simulation study

The Electrical Restiitution Curve (ERC) may play an important role in the generation and maintenance of Ventricular fibrillation (VF). As VF usually appears in ischemic hearts, we have studied the changes exerted by acute ischemia in ERCs using computer simulations. Our results show that the main effects of ischemia on rhe ERC are that (a) it shifts the ERC towards lower action potential durations (APDs) and (b) it significantly reduces the slope of the ERC. These findings are in accordance with experimental observations. When analyzing ionic currenis, it became clear that, as expected, the slow component of the delayed K current (I) was responsible for the slope of the ERC in normal conditions. However, an increased Ca inward current (I_caL) provoked by the altered [Ca²⁺] dynamics accounted for the flattening of the ERC in ischemia