Prevalence and Reproducibility of ECG-documented Premature Contractions (PCs) with Exercise in Young Adults

Abstract

Evaluation of exercise arrhythmias requires knowledge of distribution of such arrhythmias in a specific population. I have characterized a college-aged (R = 19 y r ) population i n terms of the prevalence and reproducibility of exercise PCs. Initially , 106 males (MI and 109 female^ (F), all Caucasian, non-smoking and clinically healthy, underwent standardized Bruce treadmill tests (Tl) with continuous recording of ECG lead V5 throughout exercise and 5 min. of recovery. Thirty-one (29%) M and 21 (19%) F demonstrated PCs. These were primarily of low frequency (<6), fairly evenly distributed in terms of a trial or ventricular origin, and found throughout exercise and recovery. No heart rate threshold for PCs was evident. Males with PCs exercised longer (14:55 vs 13:55, ps.01 ) than M without PCs. Of the 52 subjects (Ss) with PCs on Tl, 25 M and 19 F were retested (T2) within 6-119 days (E = 39 days). Eighteen (72%) M and 7 (37%) F showed PCs also on T2. Reproducibility was generally not precise i n terms of frequency of PCs, but PCs were generally of the same origin and often occurred at similar exercise intensities on both tests . Females who did not reproduce PCs exercised longer (11:05 vs 10:05, p</=.05) than F who did reproduce. The results show that at least occasional PCs are fairly common during exercise in clinically healthy young adults, with prevalence (p</=.10) and reproducibility (p</=.05) being higher in males than females. Reproducibility diminishes as one looks at specific frequencies of PCs. Individuals with six or more premature contractions during exercise are much more likely to demonstrate premature contractions during a subsequent exercise bout.