title: Reduction of right ventricular pacing with advanced atrioventricular search hysteresis: results of the PREVENT study.
abstract: BACKGROUND
  Right ventricular pacing predisposes to the development of heart failure and atrial fibrillation. Automatic atrioventricular search hysteresis (AVSH) is a commonly used strategy to decrease the percentage of right ventricular pacing (%VP) in patients without permanent AV block, but the results have not been optimal.
  
  
  METHODS
  The randomized, crossover PREVENT study evaluated whether an enhanced AVSH with two new features can reduce %VP compared with standard AVSH. The new features are the repetitive hysteresis [switch from extended to basic AV delay after a consistent loss of intrinsic AV conduction (IAVC) lasting for six consecutive atrial cycles] and the scan hysteresis (periodic IAVC search extension over six consecutive atrial cycles). Both standard AVSH and enhanced AVSH performed a periodic IAVC search every 180 cardiac cycles and operated with a basic AV-delay of 225 ms and a rate-independent maximum AV-delay of 300 ms for paced and sensed atrial events.
  
  
  RESULTS
  Among 178 patients, 53.4% had no evidence of AV block at enrollment and 46.6% had history of intermittent AV block. The median %VP was decreased by enhanced AVSH compared to standard AVSH (4.0% vs 5.5%, P < 0.001), particularly in patients with a history of AV block (21.4% vs 25.5%, P < 0.001). The primary study hypothesis that 25% of all patients would experience > 20% relative %VP reduction was not met as 46 (25.8%) patients (95% confidence interval, 20.5-31.8%) presented such relative reduction.
  
  
  CONCLUSIONS
  The enhanced AVSH algorithm reduces %VP compared with standard AVSH in patients with intermittent AV block.
authors: Deutsches Herzzentrum and 1. Medizinische Klinik rechts der Isar, Faculty of Medicine, Technische Universität München, Munich, Germany. kolb@dhm.mhn.de
authors: Christof
authors: C
authors: Kolb
authors: Roland
authors: R
authors: Schmidt
authors: Josef U
authors: JU
authors: Dietl
authors: Sonja
authors: S
authors: Weyerbrock
authors: Martin
authors: M
authors: Morgenstern
authors: Martin
authors: M
authors: Fleckenstein
authors: Thomas
authors: T
authors: Beier
authors: Christian
authors: C
authors: Von Bary
authors: Karl G
authors: KG
authors: Mackes
authors: Jochen
authors: J
authors: Widmaier
authors: Jörg
authors: J
authors: Kreuzer
authors: Verena
authors: V
authors: Semmler
authors: Bernhard
authors: B
authors: Zrenner
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001281:Atrial Fibrillation / Q000503:physiopathology / Q000628:therapy; D054537:Atrioventricular Block / Q000628:therapy*; D001283:Atrioventricular Node / Q000503:physiopathology; D002304:Cardiac Pacing, Artificial; D005260:Female; D005858:Germany; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial