title: Biventricular pacing for atrioventricular block and systolic dysfunction.
abstract: BACKGROUND
  Right ventricular pacing restores an adequate heart rate in patients with atrioventricular block, but high percentages of right ventricular apical pacing may promote left ventricular systolic dysfunction. We evaluated whether biventricular pacing might reduce mortality, morbidity, and adverse left ventricular remodeling in such patients.
  
  
  METHODS
  We enrolled patients who had indications for pacing with atrioventricular block; New York Heart Association (NYHA) class I, II, or III heart failure; and a left ventricular ejection fraction of 50% or less. Patients received a cardiac-resynchronization pacemaker or implantable cardioverter-defibrillator (ICD) (the latter if the patient had an indication for defibrillation therapy) and were randomly assigned to standard right ventricular pacing or biventricular pacing. The primary outcome was the time to death from any cause, an urgent care visit for heart failure that required intravenous therapy, or a 15% or more increase in the left ventricular end-systolic volume index.
  
  
  RESULTS
  Of 918 patients enrolled, 691 underwent randomization and were followed for an average of 37 months. The primary outcome occurred in 190 of 342 patients (55.6%) in the right-ventricular-pacing group, as compared with 160 of 349 (45.8%) in the biventricular-pacing group. Patients randomly assigned to biventricular pacing had a significantly lower incidence of the primary outcome over time than did those assigned to right ventricular pacing (hazard ratio, 0.74; 95% credible interval, 0.60 to 0.90); results were similar in the pacemaker and ICD groups. Left ventricular lead-related complications occurred in 6.4% of patients.
  
  
  CONCLUSIONS
  Biventricular pacing was superior to conventional right ventricular pacing in patients with atrioventricular block and left ventricular systolic dysfunction with NYHA class I, II, or III heart failure. (Funded by Medtronic; BLOCK HF ClinicalTrials.gov number, NCT00267098.).
authors.affiliation: Department of Medicine, University at Buffalo, Buffalo General Medical Center, 100 High St., D2-76, Buffalo, NY 14203, USA. abcurtis@buffalo.edu
authors.forename: Anne B
authors.initials: AB
authors.lastname: Curtis
authors.forename: Seth J
authors.initials: SJ
authors.lastname: Worley
authors.forename: Philip B
authors.initials: PB
authors.lastname: Adamson
authors.forename: Eugene S
authors.initials: ES
authors.lastname: Chung
authors.forename: Imran
authors.initials: I
authors.lastname: Niazi
authors.forename: Lou
authors.initials: L
authors.lastname: Sherfesee
authors.forename: Timothy
authors.initials: T
authors.lastname: Shinn
authors.forename: Martin St John
authors.initials: MS
authors.lastname: Sutton
mesh_terms: D000368:Aged; D054537:Atrioventricular Block / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy / Q000009:adverse effects; D017147:Defibrillators, Implantable / Q000009:adverse effects; D018572:Disease-Free Survival; D005260:Female; D054143:Heart Failure, Systolic / Q000628:therapy*; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D009026:Mortality; D010138:Pacemaker, Artificial / Q000009:adverse effects; D013318:Stroke Volume; D016896:Treatment Outcome