Right Ventricular Monophasic Action Potentials in Man

Abstract Right ventricular monophasic action potential (MAP) has been recorded during abrupt changes of cycle length and during atrial fibrillation in patients undergoing heart catheterization. The abrupt cycle length changes were initiated by sudden changes of stimulation rate using right atrial pacing. A sudden prolonged cycle is terminated by a MAP with increased duration and decreased repolarization rate of phase 3. An acute shortening of the cycle is followed by a MAP with decreased duration. The repolarization rate of phase 3 of such a MAP is not generally increased as expected from in vitro studies. In atrial fibrillation a short cycle is followed by a MAP with short duration and rapid repolarization rate of phase 3, whilst a long cycle is terminated by a MAP with long duration and slower phase 3 repolarization. The similarity between the adaptation of the MAP configuration after abrupt changes of cycle length and during atrial fibrillation suggests that rate‐dependent adaptation of the contractile force—known from earlier in vitro studies—might also occur during atrial fibrillation in man.