title: Left ventricular versus simultaneous biventricular pacing in patients with heart failure and a QRS complex ≥120 milliseconds.
abstract: BACKGROUND
  Left ventricular (LV) pacing alone may theoretically avoid deleterious effects of right ventricular pacing.
  
  
  RESULTS
  In a multicenter, double-blind, crossover trial, we compared the effects of LV and biventricular (BiV) pacing on exercise tolerance and LV remodeling in patients with an LV ejection fraction ≤35%, QRS ≥120 milliseconds, and symptoms of heart failure. A total of 211 patients were recruited from 11 centers. After a run-in period of 2 to 8 weeks, 121 qualifying patients were randomized to LV followed by BiV pacing or vice versa for consecutive 6-month periods. The greatest improvement in New York Heart Association class and 6-minute walk test occurred during the run-in phase before randomization. Exercise duration at 75% of peak Vo(2) (primary outcome) increased from 9.3±6.4 to 14.0±11.9 and 14.3±12.5 minutes with LV and BiV pacing, respectively, with no difference between groups (P=0.4327). LV ejection fraction improved from 24.4±6.3% to 31.9±10.8% and 30.9±9.8% with LV and BiV pacing, respectively, with no difference between groups (P=0.4530). Reductions in LV end-systolic volume were likewise similar (P=0.6788). The proportion of clinical responders (≥20% increase in exercise duration) to LV and BiV pacing was 48.0% and 55.1% (P=0.1615). Positive remodeling responses (≥15% reduction in LV end-systolic volume) were observed in 46.7% and 55.4% (P=0.0881). Overall, 30.6% of LV nonresponders improved with BiV and 17.1% of BiV nonresponders improved with LV pacing.
  
  
  CONCLUSIONS
  LV pacing is not superior to BiV pacing. However, nonresponders to BiV pacing may respond favorably to LV pacing, suggesting a potential role as tiered therapy.
  
  
  BACKGROUND
  URL: http://www.clinicaltrials.gov. Unique identifier: NCT00901212.
authors: Montreal Heart Institute, 5000 Belanger St, Montreal, QC, Canada H1T 1C8.   ablation2000@bellnet.ca.
authors: Bernard
authors: B
authors: Thibault
authors: Anique
authors: A
authors: Ducharme
authors: François
authors: F
authors: Harel
authors: Michel
authors: M
authors: White
authors: Eileen
authors: E
authors: O'Meara
authors: Marie-Claude
authors: MC
authors: Guertin
authors: Joel
authors: J
authors: Lavoie
authors: Nancy
authors: N
authors: Frasure-Smith
authors: Marc
authors: M
authors: Dubuc
authors: Peter
authors: P
authors: Guerra
authors: Laurent
authors: L
authors: Macle
authors: Léna
authors: L
authors: Rivard
authors: Denis
authors: D
authors: Roy
authors: Mario
authors: M
authors: Talajic
authors: Paul
authors: P
authors: Khairy
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy; D002170:Canada; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004562:Electrocardiography; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy*; D006352:Heart Ventricles; D006801:Humans; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D013599:Systole / Q000502:physiology; D016896:Treatment Outcome; D016277:Ventricular Function, Left / Q000502:physiology*; D016278:Ventricular Function, Right / Q000502:physiology*