title: Changes in heart rate variability, quality of life, and activity in cardiac resynchronization therapy patients: results of the HF-HRV registry.
abstract: BACKGROUND
  Cardiac resynchronization therapy (CRT) is a viable therapy in the treatment of heart failure (HF). Heart rate variability (HRV) is a prognostic marker of HF and mortality and is a sign of autonomic dysfunction. Acute improvements in measures of HRV have been demonstrated after CRT in small clinical studies. The purpose of the present study was to evaluate changes in HRV and patient outcomes over time and the relationship between these changes in a large generalized sample of patients who received CRT with defibrillator (CRT-D).
  
  
  METHODS
  The Heart Failure-Heart Rate Variability (HF-HRV) registry enrolled 1,421 patients who received a CRT-D device capable of measuring HRV. Patients were followed for a 1-year period. Device diagnostics, including HRV footprint; standard deviation of averaged normal R to R intervals (SDANN); and mean, minimum, and maximum heart rate were measured at each visit, in addition to activity log, New York Heart Association (NYHA) class, and quality of life (QOL) data.
  
  
  RESULTS
  This large sample of HF patients showed an overall improvement in SDANN (69.2 +/- 25.5, 78.5 +/- 27.8, 79.4 +/- 27.2, 80.7 +/- 28.2) and HRV footprint (31.5 +/- 11.8, 33.4 +/- 12.3, 34.2 +/- 12.2, 34.5 +/- 12.3) at the 2 week, 3 month, 6 month, and 12 month visits, respectively (both P < 0.001). There were also significant changes over time in clinical status (improved QOL, increased activity, and improved NYHA, all P < 0.0001), with the greatest changes occurring between the 2 week and 3 month visits.
  
  
  CONCLUSIONS
  In conclusion, these study results demonstrate that device measured HRV parameters and patient outcomes significantly improve after receipt of CRT.
authors.affiliation: Cardiology Associates of Northeast Arkansas, Jonesboro, AR 72401, USA. rgilliam@arkheart.com
authors.forename: F Roosevelt
authors.initials: FR
authors.lastname: Gilliam
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Kaplan
authors.forename: James
authors.initials: J
authors.lastname: Black
authors.forename: Kellie J
authors.initials: KJ
authors.lastname: Chase
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Mullin
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial; D004554:Electric Countershock; D005260:Female; D006333:Heart Failure / Q000503:physiopathology* / Q000628:therapy*; D006339:Heart Rate; D006801:Humans; D008297:Male; D011446:Prospective Studies; D011788:Quality of Life; D012042:Registries; D016896:Treatment Outcome