Reversal of deteriorated fractal behavior of heart rate variability by beta-blocker therapy in patients with advanced congestive heart failure

Beta-Blocker Therapy and Heart Rate Variability. Introduction: The slope of the power spectrum in heart rate variability (HRV) reflects the fractal or scaling behavior in HR dynamics and recently was confirmed as an independe nt predictor of postmyocardial infarction survival. Whether or not the new measurement in HRV foresees the functional evolution in patients with advan ced congestive heart failure treated by beta blockers is unclear. Methods and Results: Sequential 24-hour Holter ECG recordings were obtained at baseline, and 1 and 3 months after addition of atenolol therapy for adv anced congestive heart failure in 10 patients. The slope and intercept of t he regression line of power-law behavior, the short- and intermediate-term of detrended fluctuated analysis (DFA), the approximate entropy (ApEn), and the standard frequency spectra of the 24-hour HRV were compared sequential ly as well as with those in 12 age-matched normal controls. The results sho wed that the slope (-1.70 +/- 0.45 vs -1.22 +/- 0.21; P < 0.05) and the int ercept (5.11 +/- 0.46 vs 5.62 +/- 0.24; P < 0.05) of the regression line of power-law behavior and the short-term DFA (for 4 to 11 beats) (0.78 +/- 0. 18 vs 1.13 +/- 0.21; P < 0.05) increased after 3 months of atenolol treatme nt. However, the change in intermediate-term DFA (>11 beats) and ApEn was n ot apparent (1.24 +/- 0.21 vs 1.22 +/- 0.15 and 1.34 +/- 0.14 vs 1.36 +/- 0 .11; both P > 0.05). The evolution of the slope or intercept of the regress ion lint of the HRV power spectrum did not correlate with the echocardiogra phic or clinical cardiac function, or with the frequency spectral component s of the HRV (P > 0.05). Conclusion: Additional beta-blocker therapy upregulated the fractal behavio r control of the HRV in patients with advanced congestive heart failure. Th e improvement was independent of subjective and objective global cardiac pe rformance.