title: Effects of cardiac resynchronization therapy on heart rate turbulence.
abstract: BACKGROUND
  Cardiac resynchronization therapy (CRT) improves the clinical status of patients with heart failure (HF), though its effects on heart rate turbulence (HRT) are unknown.
  
  
  METHODS
  We measured HRT indices in 58 recipients of CRT systems (mean age = 56 +/- 9 years, 41 men) in New York Heart Association HF functional class III-IV, and with a left ventricular (LV) ejection fraction < or =35%. At 6 months of follow-up, 42 patients were responders and 13 nonresponders to CRT, and three patients died suddenly. The HRT indices turbulence onset (TO%) and turbulence slope (TS ms/RR interval) were calculated from digital 24-hour electrocardiogram before and after 6 months of CRT. TO > or = 0% and TS < or = 2.5 ms/RR interval were considered abnormal.
  
  
  RESULTS
  Mean TO in the entire population was 0.4 +/- 1.5 before CRT, and decreased to -0.8 +/- 7.0 during the 6 months of CRT (ns). TS increased significantly from 2.0 +/- 1.7 at baseline, to 3.9 +/- 3.1 (P < 0.05), and a significantly lower proportion of patients had abnormal HRT indices at 6 months. In contrast to the significant increase observed in responders, not significant change in TS was observed among the nonresponders.
  
  
  CONCLUSIONS
  During 6 months of CRT, improvements in HRT indices and a decrease in the proportion of patients with abnormal HRT were observed. CRT may have beneficial effects on baroreflex sensitivity.
authors.affiliation: First Department of Cardiology, Medical University of Silesia, Silesian Center for Heart Diseases, Zabrze, Poland. bms@pro.onet.pl
authors.forename: Beata
authors.initials: B
authors.lastname: Sredniawa
authors.forename: Radoslaw
authors.initials: R
authors.lastname: Lenarczyk
authors.forename: Agata
authors.initials: A
authors.lastname: Musialik-Lydka
authors.forename: Oskar
authors.initials: O
authors.lastname: Kowalski
authors.forename: Jacek
authors.initials: J
authors.lastname: Kowalczyk
authors.forename: Sylwia
authors.initials: S
authors.lastname: Cebula
authors.forename: Anna
authors.initials: A
authors.lastname: Sliwinska
authors.forename: Mariola
authors.initials: M
authors.lastname: Szulik
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Kalarus
mesh_terms: D000222:Adaptation, Physiological; D001145:Arrhythmias, Cardiac / Q000503:physiopathology* / Q000517:prevention & control*; D017704:Baroreflex; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D005260:Female; D006333:Heart Failure / Q000503:physiopathology* / Q000517:prevention & control*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome