Does exercise training still augment the heart rate variability of contemporary treated heart failure patients?

Excerpt

In patients with heart failure with reduced ejection fraction (HFrEF), diminished heart rate variability (HRV) is an independent predictor of foreshortened life expectancy [1]. Studies conducted prior to the widespread prescription of beta-adrenoceptor antagonists, employing classical methods that do not discriminate between the autonomic (i.e., vagal and sympathetic) and non-autonomic contributions to heart rate modulation, found that exercise training improves HRV in HFrEF [2, 3]. However, the majority of patients with HFrEF now being referred to cardiac rehabilitation programs are receiving beta-adrenoceptor antagonists, a drug class shown to augment total heart rate spectral power [4], tonic and baroreceptor-reflex-mediated vagal heart rate modulation, muscle sympathetic nerve discharge rhythmicity [5], and cardiac sympathetic neuronal function [6]. Moreover, HFrEF is a condition in which non-harmonic (fractal) noise often predominates at power spectral frequencies of less than 0.15 Hz [7, 8], and in which residual low-frequency harmonic power relates inversely to the intensity of efferent sympathetic discharge, i.e., at higher sympathetic nerve firing rates, the heart rate varies less [7]. …