title: Clinical outcomes with synchronized left ventricular pacing: analysis of the adaptive CRT trial.
abstract: BACKGROUND
  Acute studies have suggested that left ventricular pacing (LVP) may have benefits over biventricular pacing (BVP). The adaptive cardiac resynchronization therapy (aCRT) algorithm provides LVP synchronized to produce fusion with the intrinsic activation when the intrinsic atrioventricular (AV) interval is normal. The randomized double-blind adaptive cardiac resynchronization therapy trial demonstrated noninferiority of the aCRT algorithm compared to echocardiography-optimized BVP (control).
  
  
  OBJECTIVE
  To examine whether synchronized LVP (sLVP) resulted in better clinical outcomes.
  
  
  METHODS
  First, stratification by percent sLVP (%sLVP) and multivariate Cox proportional hazards model was used to assess the relationship between %sLVP and clinical outcomes. Second, outcomes were compared between patients in the aCRT arm (n = 318) and control patients (n = 160) stratified by intrinsic AV interval at randomization.
  
  
  RESULTS
  In the aCRT arm, %sLVP ≥50% (n = 142) was independently associated with a decreased risk of death or heart failure hospitalization (hazard ratio 0.49; 95% confidence interval 0.28-0.85; P = .012) compared with %sLVP <50% (n = 172). A greater proportion of patients with %sLVP ≥50% improved in Packer's clinical composite score at 6-month (82% vs. 68%; P = .002) and 12-month (80% vs. 62%; P = .0006) follow-ups compared to controls. In the subgroup with normal AV (n = 241), there was a lower risk of death or heart failure hospitalization (hazard ratio 0.52; 95% confidence interval 0.27-0.98; P = .044) with the aCRT algorithm. A greater proportion of patients in the aCRT arm improved in the clinical composite score at 6-month (81% vs. 69%; P = .041) and 12-month (77% vs. 66%; P = .076) follow-ups compared to controls.
  
  
  CONCLUSIONS
  Higher %sLVP was independently associated with superior clinical outcomes. In patients with normal AV conduction, the aCRT algorithm provided mostly sLVP and demonstrated better clinical outcomes compared to echocardiography-optimized BVP.
authors.affiliation: University of Ottawa Heart Institute, Ottawa, Ontario, Canada. dbirnie@ottawaheart.ca
authors.forename: David
authors.initials: D
authors.lastname: Birnie
authors.forename: Bernd
authors.initials: B
authors.lastname: Lemke
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Aonuma
authors.forename: Henry
authors.initials: H
authors.lastname: Krum
authors.forename: Kathy Lai-Fun
authors.initials: KL
authors.lastname: Lee
authors.forename: Maurizio
authors.initials: M
authors.lastname: Gasparini
authors.forename: Randall C
authors.initials: RC
authors.lastname: Starling
authors.forename: Goran
authors.initials: G
authors.lastname: Milasinovic
authors.forename: John
authors.initials: J
authors.lastname: Gorcsan
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Houmsse
authors.forename: Athula
authors.initials: A
authors.lastname: Abeyratne
authors.forename: Alex
authors.initials: A
authors.lastname: Sambelashvili
authors.forename: David O
authors.initials: DO
authors.lastname: Martin
mesh_terms: D000368:Aged; D000465:Algorithms; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D004311:Double-Blind Method; D005260:Female; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006352:Heart Ventricles; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome
keywords: %sLVP; AV; AV delay; BVP; CCS; CI; CRT; Cardiac resynchronization therapy; HF; HR; LBBB; LV; LVEF; LVP; NYHA; New York Heart Association; Optimization; RV; Synchronized left ventricular pacing; VV; aCRT; adaptive cardiac resynchronization therapy; atrioventricular; biventricular pacing; cardiac resynchronization therapy; clinical composite score; confidence interval; hazard ratio; heart failure; interventricular; left bundle branch block; left ventricular; left ventricular ejection fraction; left ventricular pacing; percent synchronized left ventricular pacing; right ventricular; sLVP; synchronized left ventricular pacing