Heart rate recovery after exercise is associated with resting QTc interval in young men

Heart rate recovery (HRR) after exercise and spectral decomposition of heart rate variability (HRV), measures of autonomic nervous system function, are predictors of cardiovascular morbidity/mortality. QT interval, an index of ventricular depolarization and repolarization attained from surface ECG, is also associated with morbidity/mortality and is strongly influenced by autonomic tone. The purpose of this study was to assess the association between HRR after exercise, resting HRV and resting rate corrected QT interval in young healthy men. HRR was assessed in 37 men (23.3 +/- 0.6 years) 1 minute after a graded exercise test. Resting QT interval was derived from ECG recordings and rate corrected using five formulae (Bazett, Fridericia, Hodges, Framingham, and the nomogram method of Karjalainen). Resting HRV was spectrally decomposed using an autoregressive approach. A negative correlation was detected for QTc interval and HRR for each method (r = -0.36 to -0.48, P < 0.05). There was no correlation between high frequency power of HRV (a marker of parasympathetic modulation) and QTc interval. There was a negative relationship between absolute LF power (a marker of both sympathetic and parasympathetic modulation) and QTc interval for Karjalainen, Framingham, and Bazett correction methods (r = -0.33 to -0.47, P < 0.05). Resting LF power of HRV and HRR after exercise are inversely associated with resting QTc interval in young healthy men, supporting a relationship between cardiac autonomic nervous system function and ventricular depolarization and repolarization.