[The variability in the duration of human atrial action potentials increases with age]

35 human atrial samples, presenting electrophysiological characteristics within "normal" limits, were studied in vitro. 19 were sampled from adult patients and 16 were sampled from very young patients. Maximum diastolic potential did not significantly differ between adult and young, either in mean value or in variability. Action potential duration increased with age, particularly during the earliest years of life. The variability of action potential duration, which is considered as an arrhythmogenic factor, is greater in the adult.