title: The prognostic benefit of cardiac resynchronization therapy is greater in concordant vs. discordant left bundle branch block in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT).
abstract: Discordant and concordant left bundle branch block (dLBBB/cLBBB) are characterized by negative or positive T waves, respectively, in lateral leads. We assessed if the two morphologies are associated with different clinical status and prognosis in patients with heart failure (HF) and current indication to Cardiac Resynchronization Therapy (CRT)/CRT-Defibrillator (CRT-D).
  
  
  
  Baseline electrocardiograms of 1270 patients with LBBB in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy cohort were analysed to identify dLBBB and cLBBB. The two groups were compared with respect to baseline clinical characteristics, primary endpoint (HF event or death), and secondary endpoint (ventricular tachycardia, ventricular fibrillation, or death) over a 3.5-year period, and benefit of CRT-D over implantable cardioverter defibrillator (ICD). dLBBB was identified in 909 (72%) patients, and cLBBB in 361 (28%). Patients with dLBBB were older, had more severe symptoms and systolic dysfunction, as well as higher brain natriuretic peptide. CRT-D was superior to ICD in patients with both LBBB morphologies. The occurrence of the primary outcome was significantly more frequent in patients with dLBBB than in those with cLBBB, both in the entire cohort (P = 0.005), and in the CRT-D arm (P = 0.002). There was a trend towards more frequent occurrence of the secondary endpoint in patients with dLBBB than in those with cLBBB, but statistical significance was not reached in the whole population or in the subgroup undergoing CRT-D. Among patients receiving CRT-D, dLBBB was an independent predictor of the primary endpoint.
  
  
  
  dLBBB morphology is associated with more severe HF clinical status and worse prognosis, even in patients receiving CRT-D, compared with cLBBB morphology.
authors.affiliation: University of Florence, Piazza di San Marco, 4, 50121 Firenze, Florence, Italy and IRCCS MultiMedica, Via Milanese, 300, 20099 Sesto San Giovanni (MI), Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Padeletti
authors.affiliation: Scuola Superiore Sant'Anna, Piazza Martiri della Libertà 33, 56127, Pisa, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Aimo
authors.affiliation: Division of Cardiology, University of Rochester Medical Center, 265 Crittenden Blvd., Rochester, NY 14642, USA.
authors.forename: Bella
authors.initials: B
authors.lastname: Vishenvsky
authors.affiliation: Division of Cardiology, University of Rochester Medical Center, 265 Crittenden Blvd., Rochester, NY 14642, USA.
authors.forename: Arielle
authors.initials: A
authors.lastname: Schwartz
authors.affiliation: Division of Cardiology, University of Rochester Medical Center, 265 Crittenden Blvd., Rochester, NY 14642, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: McNitt
authors.affiliation: Stanford University Medical Center, 291 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Wang
authors.affiliation: Division of Cardiology, University of Rochester Medical Center, 265 Crittenden Blvd., Rochester, NY 14642, USA.
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Moss
authors.affiliation: Scuola Superiore Sant'Anna, Piazza Martiri della Libertà 33, 56127, Pisa, Italy.|Fondazione Toscana Gabriele Monasterio, Via Moruzzi 1, 56124, Pisa, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Emdin
authors.affiliation: Division of Cardiology, University of Rochester Medical Center, 265 Crittenden Blvd., Rochester, NY 14642, USA.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Zareba
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000175:diagnosis / Q000209:etiology; D058406:Cardiac Resynchronization Therapy / Q000009:adverse effects / Q000379:methods / Q000706:statistics & numerical data; D058409:Cardiac Resynchronization Therapy Devices; D017147:Defibrillators, Implantable / Q000706:statistics & numerical data*; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006333:Heart Failure / Q000150:complications / Q000175:diagnosis / Q000401:mortality / Q000628:therapy; D006801:Humans; D007558:Italy; D008297:Male; D008875:Middle Aged; D009026:Mortality; D017063:Outcome Assessment, Health Care; D011379:Prognosis; D012307:Risk Factors; D012720:Severity of Illness Index