title: Preserved heart rate variability identifies low-risk patients with nonischemic dilated cardiomyopathy: results from the DEFINITE trial.
abstract: BACKGROUND
  The recent expansion of indications for prophylactic implantable cardioverter-defibrillator (ICD) placement in subjects with nonischemic dilated cardiomyopathy has raised concerns about the cost-effectiveness of this therapy.
  
  
  OBJECTIVE
  The purpose of this study was to identify low-risk patients with nonischemic dilated cardiomyopathy who may not require prophylactic ICD placement.
  
  
  METHODS
  This was a prospective study of 274 participants in the Defibrillators in Non-Ischemic Cardiomyopathy Treatment Evaluation (DEFINITE) trial, a randomized controlled trial that evaluated the role of prophylactic ICD placement in patients with nonischemic dilated cardiomyopathy. The patients underwent 24-hour Holter recording for analysis of heart rate variability (HRV). The primary HRV variable was the standard deviation of normal R-R intervals (SDNN). Patients with atrial fibrillation and frequent ventricular ectopy (>25% of beats) were excluded from HRV analysis (23% of patients). SDNN was categorized in tertiles, and Kaplan-Meier analysis was performed to compare survival in the three tertiles and excluded patients.
  
  
  RESULTS
  The study population was 73% male, with a mean age of 59 +/- 12 years and mean left ventricular ejection fraction of 21% +/- 6%. After 3-year follow-up, significant differences in mortality rates were observed: SDNN >113 ms: 0 (0%), SDNN 81-113 ms: 5 (7%), SDNN <81 ms: 7 (10%), excluded patients: 11 (17%) (P = .03). There were no deaths in the tertile with SDNN >113 ms regardless of treatment assignment (ICD vs control).
  
  
  CONCLUSIONS
  Patients with nonischemic dilated cardiomyopathy and preserved HRV have an excellent prognosis and may not benefit from prophylactic ICD placement. Patients with severely depressed HRV and patients who are excluded from HRV analysis because of atrial fibrillation and frequent ventricular ectopy have the highest mortality.
authors.affiliation: Division of Cardiology, Department of Medicine, University of Maryland at Baltimore, 22 South Greene Street, Room N3W77, Baltimore, MD 21201, USA. erashba@medicine.umaryland.edu
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Rashba
authors.forename: N A Mark
authors.initials: NA
authors.lastname: Estes
authors.forename: Paul
authors.initials: P
authors.lastname: Wang
authors.forename: Andi
authors.initials: A
authors.lastname: Schaechter
authors.forename: Adam
authors.initials: A
authors.lastname: Howard
authors.forename: Wojciech
authors.initials: W
authors.lastname: Zareba
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Couderc
authors.forename: Juha
authors.initials: J
authors.lastname: Perkiomaki
authors.forename: Joseph
authors.initials: J
authors.lastname: Levine
authors.forename: Alan
authors.initials: A
authors.lastname: Kadish
mesh_terms: D002311:Cardiomyopathy, Dilated / Q000401:mortality / Q000503:physiopathology* / Q000628:therapy; D003362:Cost-Benefit Analysis; D016757:Death, Sudden, Cardiac / Q000517:prevention & control; D017147:Defibrillators, Implantable / Q000191:economics / Q000706:statistics & numerical data*; D015716:Electrocardiography, Ambulatory; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D012307:Risk Factors; D013318:Stroke Volume; D016019:Survival Analysis