title: Clinical response with adaptive CRT algorithm compared with CRT with echocardiography-optimized atrioventricular delay: a retrospective analysis of multicentre trials.
abstract: OBJECTIVE
  Adaptive cardiac resynchronization therapy (aCRT) is a novel algorithm for CRT pacing that provides automatic ambulatory selection between synchronized left ventricular (LV) or bi-ventricular (BiV) pacing and optimization of atrioventricular (AV) and inter-ventricular (VV) delays based on periodic measurement of intrinsic conduction. We aimed to compare the clinical response between aCRT and standard CRT in historical trials.
  
  
  RESULTS
  The treatment arm of the aCRT trial was compared with a pooled historical control (HC) derived from the CRT arms of four clinical trials (MIRACLE, MIRACLE ICD, PROSPECT, and InSync III Marquis) with respect to the proportion of patients who had an improved clinical composite score (CCS) at the 6-month follow-up. Patients in the HC underwent echocardiography-guided AV optimization after the implant. A propensity score model was used to adjust for 22 potential baseline confounders of the effect of CRT. Patients were stratified into quintiles according to the propensity score and the adjusted absolute treatment effect was obtained by averaging estimates across these quintiles. The propensity score model included 751 patients (aCRT: 266, historical trials: 485). The adjusted absolute difference in percent improved in CCS between the aCRT and HC arms was 11.9% [95% confidence interval (CI): 2.7-19.2%] favouring aCRT. The patients in the aCRT group were significantly more likely to have an improved CCS than the patients in the HC (odds ratio = 1.65, 95% CI: 1.1-2.5).
  
  
  CONCLUSIONS
  The aCRT algorithm may be associated with additional improvement in clinical response compared with historical CRT with echocardiographic AV optimization.
authors.affiliation: Massachusetts General Hospital Heart Center, Harvard Medical School, 55 Fruit St., Boston, MA 02114, USA.
authors.forename: Jagmeet P
authors.initials: JP
authors.lastname: Singh
authors.forename: William T
authors.initials: WT
authors.lastname: Abraham
authors.forename: Eugene S
authors.initials: ES
authors.lastname: Chung
authors.forename: Tyson
authors.initials: T
authors.lastname: Rogers
authors.forename: Alex
authors.initials: A
authors.lastname: Sambelashvili
authors.forename: James A
authors.initials: JA
authors.lastname: Coles
authors.forename: David O
authors.initials: DO
authors.lastname: Martin
mesh_terms: D000368:Aged; D000465:Algorithms; D001283:Atrioventricular Node / Q000503:physiopathology*; D058406:Cardiac Resynchronization Therapy; D004311:Double-Blind Method; D004452:Echocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006333:Heart Failure / Q000503:physiopathology* / Q000628:therapy*; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome
keywords: Cardiac resynchronization therapy; Optimization; Pacing