title: Effectiveness of Cardiac Resynchronization Therapy by QRS Morphology in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT).
abstract: BACKGROUND
  This study aimed to determine whether QRS morphology identifies patients who benefit from cardiac resynchronization therapy with a defibrillator (CRT-D) and whether it influences the risk of primary and secondary end points in patients enrolled in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT) trial.
  
  
  RESULTS
  Baseline 12-lead ECGs were evaluated with regard to QRS morphology. Heart failure event or death was the primary end point of the trial. Death, heart failure event, ventricular tachycardia, and ventricular fibrillation were secondary end points. Among 1817 patients with available sinus rhythm ECGs at baseline, there were 1281 (70%) with left bundle-branch block (LBBB), 228 (13%) with right bundle-branch block, and 308 (17%) with nonspecific intraventricular conduction disturbances. The latter 2 groups were defined as non-LBBB groups. Hazard ratios for the primary end point for comparisons of CRT-D patients versus patients who only received an implantable cardioverter defibrillator (ICD) were significantly (P < 0.001) lower in LBBB patients (0.47; P < 0.001) than in non-LBBB patients (1.24; P = 0.257). The risk of ventricular tachycardia, ventricular fibrillation, or death was decreased significantly in CRT-D patients with LBBB but not in non-LBBB patients. Echocardiographic parameters showed significantly (P < 0.001) greater reduction in left ventricular volumes and increase in ejection fraction with CRT-D in LBBB than in non-LBBB patients.
  
  
  CONCLUSIONS
  Heart failure patients with New York Heart Association class I or II and ejection fraction ≤ 30% and LBBB derive substantial clinical benefit from CRT-D: a reduction in heart failure progression and a reduction in the risk of ventricular tachyarrhythmias. No clinical benefit was observed in patients with a non-LBBB QRS pattern (right bundle-branch block or intraventricular conduction disturbances).
  
  
  BACKGROUND
  URL: http://www.clinicaltrials.gov. Unique identifier: NCT00180271.
authors.affiliation: Cardiology Division, University of Rochester, Rochester, NY, USA. wojciech_zareba@urmc.rochester.edu
authors.forename: Wojciech
authors.initials: W
authors.lastname: Zareba
authors.forename: Helmut
authors.initials: H
authors.lastname: Klein
authors.forename: Iwona
authors.initials: I
authors.lastname: Cygankiewicz
authors.forename: W Jackson
authors.initials: WJ
authors.lastname: Hall
authors.forename: Scott
authors.initials: S
authors.lastname: McNitt
authors.forename: Mary
authors.initials: M
authors.lastname: Brown
authors.forename: David
authors.initials: D
authors.lastname: Cannom
authors.forename: James P
authors.initials: JP
authors.lastname: Daubert
authors.forename: Michael
authors.initials: M
authors.lastname: Eldar
authors.forename: Michael R
authors.initials: MR
authors.lastname: Gold
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Goldberger
authors.forename: Ilan
authors.initials: I
authors.lastname: Goldenberg
authors.forename: Edgar
authors.initials: E
authors.lastname: Lichstein
authors.forename: Heinz
authors.initials: H
authors.lastname: Pitschner
authors.forename: Mayer
authors.initials: M
authors.lastname: Rashtian
authors.forename: Scott
authors.initials: S
authors.lastname: Solomon
authors.forename: Sami
authors.initials: S
authors.lastname: Viskin
authors.forename: Paul
authors.initials: P
authors.lastname: Wang
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Moss
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000000981:diagnostic imaging / Q000401:mortality / Q000628:therapy; D058406:Cardiac Resynchronization Therapy; D058409:Cardiac Resynchronization Therapy Devices; D017147:Defibrillators, Implantable; D004562:Electrocardiography; D005260:Female; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000401:mortality / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012306:Risk; D013318:Stroke Volume; D017180:Tachycardia, Ventricular / Q000000981:diagnostic imaging / Q000401:mortality / Q000628:therapy; D016896:Treatment Outcome; D014463:Ultrasonography; D014693:Ventricular Fibrillation / Q000000981:diagnostic imaging / Q000401:mortality / Q000628:therapy