Effect of biventricular pacing on heart rate variability in patients with chronic heart failure

Background: Biventricular pacing is emerging as a long-term therapy for symptomatic heart failure. Analysis of heart rate variability (HRV) has become an important predictive tool in this syndrome. Aim of the study To assess whether chronic resynchronization therapy can affect HRV in patients with heart failure. Methods and results: Thirteen patients with heart failure were studied (mean age +/- 1 S.E. 65 +/- 2.2 years, QRS 195 +/- 5.3 ms, NYHA class 3.2 +/- 0.1, LVEF 21 +/- 1.7%). The protocol included a preliminary no pacing period for I month following device implantation. Twenty-four hour Holter ECG recordings were performed at the end of this period (baseline) and after 3 months of biventricular stimulation (VDD mode). Prior to and following pacing patients underwent NYHA class evaluation. 6-min walk test, Quality of Life Assessment and a cardiopulmonary exercise test. Biventricular pacing improved functional class (P<0.0001) and Quality of life (P<0.0001), increased 6-min walk distance, (P=0.008) and exercise duration (P<0.0001) but had no significant effect on peak exercise VO2. Resynchronization therapy increased mean 24-h RR (922 +/- 58 vs. 809 +/- 41 ms at baseline, P = 0.006), SDNN (111 +/- 11 vs. 83 +/- 8 ms, P = 0.003), SDNN-1 (56 +/- 10 vs. 40 +/- 5 ms, P = 0.02), rMSSD (66 +/- 14 vs. 41 +/- 8 ms, P = 0.003), Total Power (5724 +/- 1875 vs. 2074 +/- 553 ms 2, P = 0.03), Ultra Low Frequency Power (1969 +/- 789 vs. 653 +/- 405 ms(2), P = 0.03) and Very Low Frequency Power (2407 +/- 561 vs. 902 +/- 155 ms(2), P=0.004). Conclusion: Biventricular pacing in heart failure improves autonomic function by increasing HRV. This may have important prognostic implications. (C) 2002 European Society of Cardiology. Published by Elsevier Science B.V. All rights reserved.