title: Predictors of response to cardiac resynchronization therapy: A systematic review.
abstract: BACKGROUND
  Multiple studies have sought to determine variables associated with improved "response" to cardiac resynchronization therapy(CRT). Such variables, however, are often derived from inadequately controlled, single center cohort studies calling external validity into question. We sought to determine predictors of response to CRT-D and CRT-P utilizing the methods of systematic review.
  
  
  METHODS
  We searched MEDLINE, Embase®, and the Cochrane Central Register of Controlled Trials (CENTRAL) from January 1, 1995, as this is the date of first article reporting use of CRT through October 20, 2014. Paired investigators independently screened search results to assess eligibility. For inclusion, investigators abstracted data sequentially and assessed risk of bias independently. Investigators graded the strength of evidence as a group.
  
  
  RESULTS
  We identified 13,015 unique citations of which 11,897 were excluded during the abstract screen. During the full-text screening, we excluded 1118 citations. 12 studies reported in 15 articles were included in this review. A left bundle branch (LBBB) morphology, non-ischemic cardiomyopathy (NICM), and female gender were generally associated with improved outcomes following CRT-D. Sinus rhythm (as compared to atrial fibrillation) and a wider QRS duration were associated with improved outcomes following CRT-D albeit with a lower strength of evidence. There was insufficient evidence to determine predictors of outcomes in patients undergoing CRT-P.
  
  
  CONCLUSIONS
  A native LBBB, NICM, female gender, sinus rhythm, and a wider QRS duration are associated with improved outcomes following CRT-D implant.
authors.affiliation: Cleveland Clinic, United States. Electronic address: rickarj2@ccf.org.
authors.forename: John
authors.initials: J
authors.lastname: Rickard
authors.affiliation: Johns Hopkins School of Medicine, United States.
authors.forename: Henry
authors.initials: H
authors.lastname: Michtalik
authors.affiliation: Johns Hopkins School of Medicine, United States.
authors.forename: Ritu
authors.initials: R
authors.lastname: Sharma
authors.affiliation: Johns Hopkins School of Medicine, United States.
authors.forename: Zackary
authors.initials: Z
authors.lastname: Berger
authors.affiliation: Johns Hopkins School of Medicine, United States.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Iyoha
authors.affiliation: Johns Hopkins School of Medicine, United States.
authors.forename: Ariel R
authors.initials: AR
authors.lastname: Green
authors.affiliation: Johns Hopkins School of Medicine, United States.
authors.forename: Nowreen
authors.initials: N
authors.lastname: Haq
authors.affiliation: Johns Hopkins School of Medicine, United States.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Robinson
mesh_terms: D002037:Bundle-Branch Block / Q000175:diagnosis / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy / Q000379:methods* / Q000639:trends*; D009202:Cardiomyopathies / Q000175:diagnosis / Q000628:therapy*; D002986:Clinical Trials as Topic / Q000379:methods; D006333:Heart Failure / Q000175:diagnosis / Q000628:therapy; D006801:Humans; D017202:Myocardial Ischemia / Q000175:diagnosis / Q000628:therapy; D011237:Predictive Value of Tests; D016896:Treatment Outcome
keywords: Biventricular pacing; Cardiac resynchronization therapy; Response