title: Cardiac resynchronization therapy:  expanding clinical indications and refining patient selection.
abstract: OBJECTIVE
  Cardiac resynchronization therapy (CRT) can reduce morbidity and mortality in patients with heart failure. However, a proportion of patients do not respond to CRT. This review addresses important clinical questions regarding patient selection for CRT.
  
  
  RESULTS
  Three recent large randomized trials show that CRT reduces morbidity and mortality in patients with New York Heart Association (NYHA) functional class II heart failure. Observational studies and a recent meta-analysis suggest that patients with NYHA III heart failure and atrial fibrillation may benefit from CRT. However, atrioventricular node ablation should be considered in this population to ensure greater than 92% biventricular pacing. Data from clinical trials do not support the use of CRT in patients with baseline right bundle branch block (RBBB).
  
  
  CONCLUSIONS
  Careful selection of CRT candidates is vital to improve patient outcomes and reduce exposure to unnecessary complications. This review summarizes recent data on the selection of CRT candidates, with emphasis on patients with NYHA I and II heart failure, atrial fibrillation and RBBB.
authors.affiliation: University of Ottawa Heart Institute, Ottawa, Canada. Pnery@ottawa-heart.ca
authors.forename: Pablo B
authors.initials: PB
authors.lastname: Nery
authors.forename: Arieh
authors.initials: A
authors.lastname: Keren
authors.forename: David H
authors.initials: DH
authors.lastname: Birnie
mesh_terms: D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D014943:Global Health; D006329:Heart Conduction System / Q000503:physiopathology*; D006333:Heart Failure / Q000401:mortality / Q000503:physiopathology / Q000628:therapy; D006801:Humans; D009017:Morbidity; D018579:Patient Selection; D015996:Survival Rate; D016896:Treatment Outcome