Heart rate recovery after treadmill electrocardiographic exercise stress test and 24-hour heart rate variability in healthy individuals.

BACKGROUND Heart rate recovery after treadmill electrocardiographic exercise stress test is modulated by the autonomic nervous system. Analysis of heart rate variability can provide useful information about autonomic control of the cardiovascular system. OBJECTIVE The aim of the study was to test the hypothesis of association between heart recovery after treadmill electrocardiographic exercise test and heart rate variability. METHODS We studied 485 healthy individuals aged 42+/- 12.1 (range 15-82) years, 281(57.9%) women, submitted to treadmill electrocardiographic exercise stress tests and heart rate variability evaluations over time (SDNN, SDANN, SDNNi, rMSSD, pNN50) and frequency (LF, HF, VLF, LF/HF ratio) domains in 24-hour ambulatory electrocardiographic monitoring. RESULTS Heart rate recovery was 30+/- 12 beats in the 1st minute and 52+/- 13 beats in the 2nd minute after exercise. Younger individuals recovered faster from the 2nd to the 5th minute after exercise (r= 0.19-0.35, P< 0.05). Recovery was faster in women than in men (4+/- 1.1 beats lower in the 1st minute, p<0.001; 5.7+/- 1.2 beats lower in the 2nd minute, p<0.01; 4.1+/- 1.1 beats lower in the 3rd minute, p<0.001). There was no significant correlation between heart rate recovery and heart rate variability in 1st and 2nd minutes after exercise. SDNN, SDANN, SDNNi, rMSSD, and pNN50 indices demonstrated a significant correlation with heart rate recovery only at the 3rd and 4th minutes. CONCLUSION The hypothesis of association between heart rate recovery and 24-hour heart rate variability in the first two minutes after exercise was not substantiated in this study. Heart rate recovery after exercise was associated with age and gender.