title: Meta-analysis: cardiac resynchronization therapy for patients with less symptomatic heart failure.
abstract: BACKGROUND
  Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in patients with advanced symptoms of heart failure.
  
  
  OBJECTIVE
  To assess the benefits and harms of CRT in patients with advanced heart failure and those with less symptomatic disease.
  
  
  METHODS
  A search of electronic databases (1950 to December 2010), hand-searching of reference lists, and unpublished data from principal investigators. Searches were not limited to the English language.
  
  
  METHODS
  Randomized, controlled trials of CRT compared with usual care and right or left ventricular pacing in adults with heart failure and a left ventricular ejection fraction of 0.40 or less.
  
  
  METHODS
  Two reviewers performed independent study selection, data abstraction, and quality assessment by using the Cochrane tool for assessing risk for bias.
  
  
  RESULTS
  There were 9082 patients in 25 trials. In patients with New York Heart Association (NYHA) class I and II symptoms, CRT reduced all-cause mortality (6 trials, 4572 participants; risk ratio [RR], 0.83 [95% CI, 0.72 to 0.96]) and heart failure hospitalizations (4 trials, 4349 participants; RR, 0.71 [CI, 0.57 to 0.87]) without improving functional outcomes or quality of life. In patients with NYHA class III or IV symptoms, CRT improved functional outcomes and reduced both all-cause mortality (19 trials, 4510 participants; RR, 0.78 [CI, 0.67 to 0.91]) and heart failure hospitalizations (11 trials, 2663 participants; RR, 0.65 [CI, 0.50 to 0.86]). The implant success rate was 94.4%; peri-implantation deaths occurred in 0.3% of trial participants, mechanical complications in 3.2%, lead problems in 6.2%, and infections in 1.4%.
  
  
  CONCLUSIONS
  Subgroup analyses were underpowered and lack data for persons with NYHA class I symptoms, atrial fibrillation, chronic kidney disease, or right bundle branch block.
  
  
  CONCLUSIONS
  Cardiac resynchronization therapy is beneficial for patients with reduced left ventricular ejection fraction, symptoms of heart failure, and prolonged QRS, regardless of NYHA class.
  
  
  BACKGROUND
  None.
authors.affiliation: Mazankowski Alberta Heart Institute, University of Alberta, Canada.
authors.forename: Nawaf S
authors.initials: NS
authors.lastname: Al-Majed
authors.forename: Finlay A
authors.initials: FA
authors.lastname: McAlister
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Bakal
authors.forename: Justin A
authors.initials: JA
authors.lastname: Ezekowitz
mesh_terms: D000368:Aged; D058406:Cardiac Resynchronization Therapy / Q000009:adverse effects; D002423:Cause of Death; D004562:Electrocardiography; D006333:Heart Failure / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D006760:Hospitalization; D006801:Humans; D008875:Middle Aged; D017594:Publication Bias; D011788:Quality of Life; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology