title: Antiarrhythmic effect of reverse electrical remodeling associated with cardiac resynchronization therapy.
abstract: BACKGROUND
  Antiarrhythmic and proarrhythmic effects of cardiac resynchronization therapy (CRT) remain controversial. We hypothesized that reverse electrical remodeling (RER) with CRT is associated with reduced frequency of ventricular tachyarrhythmias (VTs).
  
  
  METHODS
  The width of native and paced QRS was measured in lead II electrocardiogram before and 13 ± 7 months after implantation of a CRT defibrillator device in 69 patients (mean age 66.3 ± 13.9; 39 males [83%]) with bundle branch block (BBB) (41 patients with left BBB and three patients with bifascicular block) or nonspecific intraventricular conduction delay (25 patients, 36%), and New York Heart Association class III-IV heart failure. Biventricular pacing was inhibited for 10 seconds to record native QRS. RER was defined as a decrease in the native QRS duration ≥10 ms compared to preimplant. Patients were followed prospectively 24 ± 13 months after assessment for electrical remodeling.
  
  
  RESULTS
  RER was observed in 22 patients (32%), among whom QRS duration decreased by 30.9 ± 14.1 ms (P < 0.00001) with similar heart rate and QRS morphology. Native QRS duration increased by 10.3 ± 16.6 ms in the other 47 patients (68%) (P = 0.0001). Baseline mean ejection fraction did not differ between patients with and those without RER (24.9 ± 10.0 vs 24.2 ± 8.6%, NS). During 2 ± 1 years of further follow-up, 19 patients had VTs and 12 patients died. RER was associated with a fourfold decrease in the risk of death or sustained VTs requiring appropriate implantable cardioverter-defibrillator therapies, whichever came first (hazard ratio 0.25; 95% confidence interval 0.08-0.85; P = 0.026).
  
  
  CONCLUSIONS
  RER of the native conduction with CRT is associated with decreased mortality and antiarrhythmic effect of CRT.
authors.affiliation: Division of Cardiology, Department of Medicine, Johns Hopkins Hospital, Baltimore, Maryland 21287, USA. lteresh1@jhmi.edu
authors.forename: Larisa G
authors.initials: LG
authors.lastname: Tereshchenko
authors.forename: Charles A
authors.initials: CA
authors.lastname: Henrikson
authors.forename: Peter
authors.initials: P
authors.lastname: Stempniewicz
authors.forename: Lichy
authors.initials: L
authors.lastname: Han
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Berger
mesh_terms: D000368:Aged; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D017180:Tachycardia, Ventricular / Q000503:physiopathology* / Q000517:prevention & control*; D016896:Treatment Outcome