Right Ventricular Monophasic Action Potentials During Regular Rhythm

Right ventricular monophasic action potential (MAP) has been recorded during spontaneous regular rhythm in 27 out of 28 patients investigated with MAP recording technique. In addition 14 recordings of right ventricular MAP were obtained in 12 of the patients during pacing‐induced tachycardia. There is a good agreement between duration of right ventricular MAP and QT time in the absence of conduction defects. A higher heart rate is associated with a shortening of the duration of the MAP, both in individual cases during pacing‐induced tachycardia and in a patient group. A decreased duration of MAP recorded during spontaneous rhythm is due to shortening of phases 1–2 and 3 as well as increased repolarization rates during these phases. The shortening of a MAP induced by atrial pacing is not accompanied by a general increase of repolarization rate of phase 3, possibly due to lack of increased sympathetic discharge. Acute digitalization is accompanied by a shortening of the duration of the MAP in spite of decreased heart rate.