title: Baseline functional capacity and the benefit of cardiac resynchronization therapy in patients with mildly symptomatic heart failure enrolled in MADIT-CRT.
abstract: BACKGROUND
  Mildly symptomatic heart failure (HF) patients were shown to derive substantial clinical benefit from cardiac resynchronization therapy with defibrillator (CRT-D) in Multicenter Automatic Defibrillator Implantation Trial in Cardiac Resynchronization Therapy. However, the relationship between functional capacity (FC) and CRT-D benefit in the trial was not assessed.
  
  
  OBJECTIVE
  To evaluate the association between FC and response to CRT-D in Multicenter Automatic Defibrillator Implantation Trial in Cardiac Resynchronization Therapy.
  
  
  METHODS
  We evaluated the association between preimplantation FC and the benefit of CRT-D in reducing the risk of HF or death in Multicenter Automatic Defibrillator Implantation Trial in Cardiac Resynchronization Therapy. Functional status was assessed by a 6-minute walk test (6MWT), dichotomized at the median value as poor (<350 m) or good (≥350 m).
  
  
  RESULTS
  Implantable cardioverter-defibrillator-only patients with a poor FC had an adjusted 73% increased risk for HF or death (P <.001) and a 2.4-fold (P = .001) increased risk for all-cause mortality. CRT-D therapy was associated with 63% (P <.001) and 44% (P <.001) reductions in the risk of HF or death among left bundle branch block patients with a poor FC and a good FC, respectively (P for interaction = .10). Among left bundle branch block patients with a poor FC, CRT-D was also associated with a significant reduction in the risk of all-cause mortality (hazard ratio 0.52; P = .015) whereas the survival benefit of CRT-D was not observed among those who had a higher FC at enrollment (hazard ratio 1.01; P = .98; P for interaction = .10).
  
  
  CONCLUSIONS
  Poor FC is a strong independent predictor for mortality and HF events in patients with mildly symptomatic HF. Left bundle branch block patients with poor baseline FC derive a pronounced benefit from CRT-D, manifest by a significant reduction in mortality.
authors.affiliation: Cardiology Division, Department of Medicine, University of Rochester Medical Center, Rochester, New York 14642, USA. Andrew_Brenyo@urmc.rochester.edu.
authors.forename: Andrew
authors.initials: A
authors.lastname: Brenyo
authors.forename: Ilan
authors.initials: I
authors.lastname: Goldenberg
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Moss
authors.forename: Mohan
authors.initials: M
authors.lastname: Rao
authors.forename: Scott
authors.initials: S
authors.lastname: McNitt
authors.forename: David T
authors.initials: DT
authors.lastname: Huang
authors.forename: Wojciech
authors.initials: W
authors.lastname: Zareba
authors.forename: Alon
authors.initials: A
authors.lastname: Barsheshet
mesh_terms: D000368:Aged; D000959:Antihypertensive Agents / Q000627:therapeutic use; D058406:Cardiac Resynchronization Therapy; D004232:Diuretics / Q000627:therapeutic use; D005080:Exercise Test; D005260:Female; D006304:Health Status; D006333:Heart Failure / Q000188:drug therapy / Q000401:mortality / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012189:Retrospective Studies; D012306:Risk; D013223:Statistics as Topic; D014481:United States
chemical_list: D000959:Antihypertensive Agents; D004232:Diuretics