Cardiac sympatho-vagal balance changes induced by short-term exercise training are related to aerobic responses in patients with coronary artery disease

Background Changes in heart rate variability (HRV) and peak of oxygen uptake (VO 2 peak), both considered good predictors of mortality, may occur with training (Boutcher and Stein Eur J Appl Physiol. 1995). However, modalities of exercise and HRV record (Buchheit et al. Am J Physiol. 2004, Kiviniemi et al. Int J Sports Med. 2015) may interact on the relation between HRV and VO 2 peak changes to exercise. Purpose The present study aimed to test the hypothesis that changes in cardiac tone with chronic exercise were related to aerobic responses to short-term exercise training in patients with coronary artery disease (CAD). Methods Thirty-four CAD patients (58.5 ± 11.0-years, 173 ± 7 cm, 85.1 ± 21.3 kg) performed 4-weeks of exercise-based cardiac rehabilitation program. HRV was collected during slow-wave nighttime sleep (Buchheit et al. Am J Physiol. 2004) and VO 2 peak was determined during an incremental cycling exercise test before and after the training period (Lepretre et al. Int J Sports Med. 2016). Results The training program resulted in significant increases in VO 2 peak (19.2 ± 6.4 vs. 23.5 ± 7.0 mLO 2 ·min −1 ·kg −1 , i.e. + 22%, P  P  = 0.017) and a decrease in the alpha-2 exponent of the HRV derived from the detrended fluctuation analysis (DFA) ( P  = 0.011). The higher was the change in VO 2 peak, the greater was the standard deviation of the average of normal sinus to normal sinus (SDANN) alteration ( r  = 0.51, P  = 0.044 with a 95% confidence interval of [0.0179, 0.8023]). Conclusions VO 2 peak, alpha-2 exponent,–i.e. the long-term fractal component obtained from DFA–, and SDANN previously showed predictive values for all-cause mortality in elderly and cardiac patients (Myers et al. N Engl J Med. 2002, Hotta et al. Biomed Pharmacother. 2005, Task Force Eur Heart J. 1996). Our results suggest that 4-weeks of exercise-based cardiac rehabilitation induced autonomic nocturnal changes, which were related to beneficial cardiorespiratory adaptations.