title: Effectiveness of implantable cardioverter defibrillators for primary prevention of sudden cardiac death in subgroups a systematic review.
abstract: BACKGROUND
  Previous systematic reviews of implantable cardioverter defibrillators (ICDs) used for primary prevention of sudden cardiac death (SCD) concluded that ICDs are less effective in women and the elderly.
  
  
  OBJECTIVE
  To examine ICD effectiveness for primary prevention of SCD across subgroups by sex, age, New York Heart Association class, left ventricular ejection fraction, heart failure, left bundle branch block, QRS interval, time since myocardial infarction, blood urea nitrogen level, and diabetes.
  
  
  METHODS
  MEDLINE and the Cochrane Central Register of Controlled Trials through 3 September 2013 with no language restriction.
  
  
  METHODS
  Researchers screened articles for studies comparing ICD versus no ICD for primary prevention.
  
  
  METHODS
  Data were extracted about study design, patients, interventions, mortality and SCD outcomes, subgroup characteristics, and subgroup effects. Quality of subgroup analyses was determined by consensus. Relative odds ratios comparing subgroup effects were calculated, and random-effects model meta-analyses were conducted on these ratios.
  
  
  RESULTS
  Meta-analysis of 14 studies showed a decrease in deaths and SCDs due to ICD treatment. Ten studies provided subgroup analyses. Nine studies compared ICD versus no ICD, whereas one compared cardiac resynchronization therapy plus a defibrillator versus no ICD. Within-study interaction tests and across-study meta-analyses yielded weak evidence that did not show differences for all-cause mortality in subgroups by sex, age, and QRS interval. The evidence was indeterminate for other evaluated subgroups because of a paucity of data.
  
  
  CONCLUSIONS
  Many subgroup analyses were underpowered, which may have resulted in false-negative findings.
  
  
  CONCLUSIONS
  Weak evidence fails to show differences for all-cause mortality in subgroups of sex, age, and QRS interval. Evidence is indeterminate for all-cause mortality in the other subgroups and for SCD.
  
  
  BACKGROUND
  Agency for Healthcare Research and Quality.
authors.forename: Amy
authors.initials: A
authors.lastname: Earley
authors.forename: Rebecca
authors.initials: R
authors.lastname: Persson
authors.forename: Ann C
authors.initials: AC
authors.lastname: Garlitski
authors.forename: Ethan M
authors.initials: EM
authors.lastname: Balk
authors.forename: Katrin
authors.initials: K
authors.lastname: Uhlig
mesh_terms: D000367:Age Factors; D002423:Cause of Death; D016757:Death, Sudden, Cardiac / Q000517:prevention & control*; D017147:Defibrillators, Implantable; D005260:Female; D006801:Humans; D008297:Male; D011322:Primary Prevention; D012307:Risk Factors; D012737:Sex Factors