title: The effect of QRS duration on cardiac resynchronization therapy in patients with a narrow QRS complex: a subgroup analysis of the EchoCRT trial.
abstract: OBJECTIVE
  In EchoCRT, a randomized trial evaluating the effect of cardiac resynchronization therapy (CRT) in patients with a QRS duration of <130 ms and echocardiographic evidence of left ventricular dyssynchrony, the primary outcome occurred more frequently in the CRT when compared with the control group. According to current heart failure guidelines, CRT is recommended in patients with a QRS duration of ≥120 ms. However, there is some ambiguity from clinical trial data regarding the benefit of patients with a QRS duration of 120-130 ms.
  
  
  RESULTS
  The main EchoCRT trial was prematurely terminated due to futility. For the current subgroup analysis we compared data for CRT-ON vs. -OFF in patients with QRS < 120 (n = 661) and QRS 120-130 ms (n = 139). On uni- and multivariable analyses, no significant interaction was observed between the two groups and randomized treatment for the primary or any of the secondary endpoints. On multivariable analysis, a higher risk for the primary endpoint was observed in patients with a QRS duration of 120-130 ms randomized to CRT-ON vs. CRT-OFF (hazard ratio 2.18, 95% CI 1.02-4.65; P = 0.044). However, no statistically significant interaction, compared with patients with QRS < 120 ms randomized to CRT-ON vs. CRT-OFF, was noted (P-interaction = 0.160).
  
  
  CONCLUSIONS
  In this pre-specified subgroup analysis of EchoCRT, no benefit of CRT was evident in patients with a QRS duration of 120-130 ms. These data further question the usefulness of CRT in this patient population.
authors.affiliation: Department of Cardiology, Heart Failure Clinic and Transplantation, University Heart Center Zurich, Zurich, Switzerland.
authors.forename: Jan
authors.initials: J
authors.lastname: Steffel
authors.affiliation: Robertson Centre for Biostatistics, University of Glasgow, Glasgow, UK.
authors.forename: Michele
authors.initials: M
authors.lastname: Robertson
authors.affiliation: Cardiac Arrhythmia Service, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Jagmeet P
authors.initials: JP
authors.lastname: Singh
authors.affiliation: Division of Cardiovascular Medicine, Ohio State University Medical Center, Davis Heart and Lung Research Institute, Columbus, OH, USA.
authors.forename: William T
authors.initials: WT
authors.lastname: Abraham
authors.affiliation: Department of Cardiology, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Jeroen J
authors.initials: JJ
authors.lastname: Bax
authors.affiliation: Division of Cardiovascular Medicine and Howard Gilmanand Ron and Jean Schiavone Institutes, State University of New York Downstate College of Medicine, New York, NY, USA.
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Borer
authors.affiliation: University of Bergen, Stavanger University Hospital, Stavanger, Norway.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Dickstein
authors.affiliation: Robertson Centre for Biostatistics, University of Glasgow, Glasgow, UK.
authors.forename: Ian
authors.initials: I
authors.lastname: Ford
authors.affiliation: University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: John
authors.initials: J
authors.lastname: Gorcsan
authors.affiliation: Nouvelles Cliniques Nantaises, Nantes, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Gras
authors.affiliation: Monash Centre of Cardiovascular Research and Education in Therapeutics, Melbourne, VIC, Australia.
authors.forename: Henry
authors.initials: H
authors.lastname: Krum
authors.affiliation: Aalborg University, Aalborg, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Sogaard
authors.affiliation: Department of Cardiology, Heart Failure Clinic and Transplantation, University Heart Center Zurich, Zurich, Switzerland.
authors.forename: Johannes
authors.initials: J
authors.lastname: Holzmeister
authors.affiliation: Cardiology Department, Thorax Institute, Hospital Clinic, University of Barcelona, Spain.
authors.forename: Josep
authors.initials: J
authors.lastname: Brugada
authors.affiliation: Department of Cardiology, Heart Failure Clinic and Transplantation, University Heart Center Zurich, Zurich, Switzerland frank.ruschitzka@googlemail.com.
authors.forename: Frank
authors.initials: F
authors.lastname: Ruschitzka
mesh_terms: D001145:Arrhythmias, Cardiac / Q000503:physiopathology / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy; D004562:Electrocardiography; D005260:Female; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D017211:Treatment Failure
keywords: Cardiac resynchronization therapy; Narrow QRS; QRS duration