Evaluation of autonomic function underlying slow postexercise heart rate recovery

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Function
• Exercise Stress Testing

Background:

• Reduced heart rate recovery (HRR) post-exercise is a strong predictor of cardiovascular and all-cause mortality.
• The underlying cause of slow HRR is thought to be diminished vagal activity, but direct evidence is lacking in affected populations.

Purpose of the Study:

• To investigate the autonomic nervous system's role in heart rate recovery (HRR).
• To analyze autonomic contributions to slow HRR using time-frequency spectral analysis.

Main Methods:

• Defined slow HRR as a heart rate reduction ≤ 18 bpm within 1 minute post-graded maximal exercise test (GXT).
• Employed continuous wavelet transform (CWT) for dynamic time-dependent spectral analysis of autonomic activity (LF and HF peaks).
• Compared autonomic responses during recovery in individuals with previously identified slow HRR versus a control group with normal HRR.

Main Results:

• A subset of individuals (7/20) consistently demonstrated slow HRR (14 ± 5 bpm) upon repeat testing.
• Individuals with consistently slow HRR exhibited significantly lower high-frequency (HF) and low-frequency (LF) power fluctuations during recovery compared to those with normal HRR (29 ± 5 bpm).

Conclusions:

• Attenuated heart rate recovery (HRR) following GXT is directly linked to impaired vagal reactivation.
• Prolonged sympathetic stimulation persists after maximal exercise cessation in individuals with slow HRR.
• Continuous wavelet transform (CWT) effectively assesses autonomic dysfunction contributing to abnormal HRR.