title: Biventricular versus right ventricular pacing in patients with AV block (BLOCK HF): clinical study design and rationale.
abstract: BACKGROUND
  Right ventricular (RV) pacing restores ventricular systole in patients with atrioventricular (AV) block, yet recent studies have suggested that in patients with AV block and left ventricular (LV) dysfunction, RV pacing may exacerbate the progression to heart failure (HF). BLOCK HF is a prospective, multi-center, randomized, double-blind, controlled trial designed to determine whether patients with AV block, LV dysfunction (EF < or = 50%), and mild to moderate HF (NYHA I-III) who require pacing benefit from biventricular (BiV) pacing, compared with RV pacing alone.
  
  
  OBJECTIVE
  The primary objective of this trial is to determine whether the time to first event (all-cause mortality, heart failure-related urgent care, or a > or = 15% increase in left ventricular end systolic volume index [LVESVI]) for patients with BiV pacing is superior to that of patients with RV pacing.
  
  
  METHODS
  Patients with AV block and LV dysfunction who require permanent pacing and undergo successful implantation of a commercial Medtronic CRT device, with or without an ICD, will be randomized to BiV or RV pacing. Patients are followed at least every 6 months until study closure. Up to 1,636 patients may be enrolled in 150 centers worldwide.
  
  
  CONCLUSIONS
  BLOCK HF is a large, randomized, clinical study in pacing-indicated patients with AV block, mild to moderate HF symptoms, and LV dysfunction to determine whether BiV pacing is superior to RV pacing in slowing the progression of HF.
authors.affiliation: University of South Florida, Tampa, Florida 33612, USA. acurtis@health.usf.edu
authors.forename: Anne B
authors.initials: AB
authors.lastname: Curtis
authors.forename: Philip B
authors.initials: PB
authors.lastname: Adamson
authors.forename: Eugene
authors.initials: E
authors.lastname: Chung
authors.forename: Martin St John
authors.initials: MS
authors.lastname: Sutton
authors.forename: Feng
authors.initials: F
authors.lastname: Tang
authors.forename: Seth
authors.initials: S
authors.lastname: Worley
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects / Q000379:methods*; D005260:Female; D006327:Heart Block / Q000150:complications* / Q000628:therapy*; D006333:Heart Failure / Q000209:etiology* / Q000517:prevention & control*; D006801:Humans; D038622:Internationality; D008297:Male; D008875:Middle Aged; D016032:Randomized Controlled Trials as Topic; D012106:Research