Right atrial monophasic action potential in healthy males. Studies during spontaneous sinus rhythm and atrial pacing.

Right atrial monophasic action potentials (MAP) have been recorded in 40 healthy males. At least one MAP recording was performed in each individual during spontaneous sinus rhythm. Right atrial pacing and simultaneous MAP recording were performed in 25 of the 40 individuals. The paced cycle length was successively decreased in steps of 100 msec between 800 and 400 msec. The durations of the MAP at 50 and 90% repolarization and the relative repolarization rate during phase 3 (RRR ph 3) were calculated and normal values for the variables are given. A correlation was demonstrated between the duration of the MAP and the cycle length-the longer the cycle length, the longer the duration of the MAP-both during sinus rhythm and during the atrial pacing. A significant correlation was also shown between the RRR ph 3 and the duration of the MAP at 90% repolarization-the shorter the MAP, the faster the RRR ph 3. One age group (45-54 years) deviated significantly from the rest in some respects, but in general there was no age trend in the whole material.