title: Effect of biventricular pacing on heart rate variability in patients with chronic heart failure.
abstract: 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.
  
  
  OBJECTIVE
  To assess whether chronic resynchronization therapy can affect HRV in patients with heart failure.
  
  
  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 1 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 VO(2). 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-I (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).
  
  
  CONCLUSIONS
  Biventricular pacing in heart failure improves autonomic function by increasing HRV. This may have important prognostic implications.
authors.affiliation: Second Department of Cardiology, Onassis Cardiac Surgery Center, 356 Syngrou Avenue, 17674, Athens, Greece. elbee@ath.forthnet.gr
authors.forename: Efthimios G
authors.initials: EG
authors.lastname: Livanis
authors.forename: Panagiota
authors.initials: P
authors.lastname: Flevari
authors.forename: George N
authors.initials: GN
authors.lastname: Theodorakis
authors.forename: Fotis
authors.initials: F
authors.lastname: Kolokathis
authors.forename: Dionyssios
authors.initials: D
authors.lastname: Leftheriotis
authors.forename: Dimitrios Th
authors.initials: DT
authors.lastname: Kremastinos
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial; D002908:Chronic Disease; D004452:Echocardiography; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology; D005500:Follow-Up Studies; D006333:Heart Failure / Q000503:physiopathology* / Q000628:therapy*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D011788:Quality of Life; D013223:Statistics as Topic; D013318:Stroke Volume / Q000502:physiology; D016896:Treatment Outcome