Effect of beta-blockade on heart rate variability in decompensated heart failure

Background: One of the putative mechanisms for the salutary effects of β-blockers in patients with congestive heart failure is their ability to improve autonomic dysfunction. However, patients with profound neurohumoral abnormalities derive little survival benefit from β-blockers. The purpose of the current study was to evaluate the effect of β-blockers on heart rate variability in decompensated heart failure. Methods: Time and frequency domain heart rate variability indices were obtained from 24-h Holter recordings and compared to assess the role of β-blockade in 199 patients (mean age 60±14 years [range 21 to 87]) with decompensated heart failure (New York Heart Association functional class III [66%] and IV [34%]). Results: All heart rate variability indices were markedly suppressed but were substantially higher in patients who were on β-blockers. Time domain measures of parasympathetic cardiac activity, the percentage of RR intervals with >50 ms variation (4.9±0.6 vs. 7.7±1.2%, P=0.006) and the square root of mean squared differences of successive RR intervals (22.7±2.0 vs. 31.6±4.1 ms, P=0.004), were higher in the β-blocker group. Spectral analysis revealed that the total power and the ultra low frequency power were significantly higher in patients on β-blockers (82% and 59%, respectively). The high frequency power, a spectral index of parasympathetic modulation, was 41% higher in the β-blocker group (121±25 vs. 171±27 ms2, P=0.02). Multiple linear regression, adjusted for clinical parameters and drug therapies, revealed a strong positive relationship between β-blockade and higher values of time and frequency domain measures. The mean number of ventricular tachycardia episodes were significantly lower in patients on β-blocker therapy (3.6±1.5 vs. 19.0±5.3, P=0.04). Conclusions: β-blockers improve the impaired cardiac autonomic regulation during high sympathetic stress of decompensated heart failure.