Variable effects of physical training of heart rate variability, heart rate recovery, and heart rate turbulence in chronic heart failure.

Background: Heart rate variability (HRV), heart rate turbulence (HRT), and heart rate recovery (HRR), indices that reflect autonomic nervous system (ANS) activity, are outcome predictors in patients with chronic heart failure (CHF). It is not clear, however, whether they reflect the same components of ANS activity. No study has examined the effects of physical training (PT) training on HRV, HRT, and HRR in CHF.
Study Objective: To examine the responses of HRV, HRT, and HRR to a PT program in patients presenting with CHF.
Methods: In 41 patients (mean age = 58.7 +/- 10.2 years) in New York Heart Association CHF functional classes II or III, and with a left ventricular ejection fraction <40%, HRV, HRT, and HRR were measured before and after 8 weeks of PT.
Results: The training was clinically effective in all patients. Before versus after PT, standard deviation of all normal RR intervals increased from 107 +/- 30 to 114 +/- 32 ms (P = 0.047), high frequency increased from 210 +/- 227 to 414 +/- 586 ms(2)/Hz (P = 0.02), and the low/high frequency ratio decreased from 1.8 +/- 1.55 to 1.1 +/- 1.2 (P = 0.002). HRT and HRR did not change significantly after PT.
Conclusions: In patients with CHF, the positive effects of PT were limited to HRV indices, which reflect parasympathetic activity, without significantly changing HRR and HRT. These observations indicate that different mechanisms modulate HRV, HRR, and HRT, which provide complementary information regarding ANS activity. The 8-week PT program failed to completely normalize ANS function.