Atrial repolarization in healthy males. Studies with programmed stimulation and monophasic action potential recordings.

Right atrial effective refractory periods (AERP) and monophasic action potentials (MAP) have been determined in 29 healthy males in four different age groups between 25 and 64 years. One age group (45-54 years) showed a significantly longer AERP than the others, with a mean of 283 msec compared with 230-238 msec in the other groups. However, no age trend was found in the total material. The AERP decreased at higher paced heart rates, the decrease between paced cycle lengths of 800 and 600 msec amounting to 13 msec. When the MAP and the AERP were determined in the same position of the atrium, they showed no statistically significant correlation. A possible explanation is that the cells contributing to the AERP and the MAP are not altogether the same. The MAP and the AERP determinations have a similar degree of reproducibility but possibly mirror different kinds of repolarization phenomenon.