Ischemia, Heart Rate, and Ventricular Repolarization

Abstract

George Ralph Mines was probably the first to note that, after an abrupt change in heart rate, several beats were needed before the ECG attained a constant form. He considered this an interesting example of how “the previous history of the tissue may influence its immediate behaviour.”1 Later studies confirmed that the heart has a long “memory,” that changes brought about by transient changes in rate or rhythm persist for many beats, and that, on a sudden change in heart rate, several hundred beats at the new rate are needed for the refractory period to reach a steady state.2,3 Although in many studies the changes in action potential configuration during acute ischemia have been described (for references see Wit and Janse4), studies on the dynamic behavior of action potential duration and refractory period after sudden changes in heart rate in acutely ischemic myocardium are rare; therefore, the article by Leerssen et al.5 in this issue of Journal is a welcome addition.