title: Eliminating right ventricular pacing may not be best for patients requiring implantable cardioverter-defibrillators.
abstract: BACKGROUND
  Excessive right ventricular (RV) pacing has been associated with adverse clinical outcomes in patients receiving pacemakers or implantable cardioverter-defibrillators (ICDs). It remains uncertain how much RV pacing is clinically deleterious.
  
  
  OBJECTIVE
  This retrospective analysis assessed the relationship between the amount of RV pacing and the composite of all-cause mortality and heart failure hospitalization in all patients programmed DDDR in the Inhibition of Unnecessary RV Pacing with AV Search Hysteresis in ICDs (INTRINSIC RV) study.
  
  
  METHODS
  Seven hundred fifteen patients consistently programmed to DDDR mode throughout follow-up (mean 11.6 months) were examined. The relationship between RV pacing tier and death and heart failure hospitalization was determined and compared with patient characteristics.
  
  
  RESULTS
  Across the six RV pacing tiers, patients differed significantly with respect to age, clinical history of ventricular tachycardia, atrial fibrillation, and atrial flutter, and amiodarone use. When controlling for these baseline differences, the best outcome was seen in the group with RV pacing between 10% and 19% (2.8% event rate; n = 106). Increasing levels of RV pacing were generally predictive of higher event rates (death or heart failure hospitalization; P = 0.003), except for the group (n = 344) with the least amount of RV pacing (0-9%). This group exhibited poorer outcomes than otherwise expected (P = 0.016), with 8.1% of these patients experiencing an event.
  
  
  CONCLUSIONS
  High levels of RV pacing are associated with heart failure hospitalization and mortality in a large ICD population. However, ICD patients with some RV pacing (10%-19%) exhibit lower event rates compared with those with very low levels (0-9%), possibly due to the physiologically appropriate nature of that RV pacing.
authors.affiliation: University of Iowa Hospitals, Iowa City, IA 52242, USA. brian-olshansky@uiowa.edu
authors.forename: Brian
authors.initials: B
authors.lastname: Olshansky
authors.forename: John D
authors.initials: JD
authors.lastname: Day
authors.forename: Darin R
authors.initials: DR
authors.lastname: Lerew
authors.forename: Scott
authors.initials: S
authors.lastname: Brown
authors.forename: Kira Q
authors.initials: KQ
authors.lastname: Stolen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D002318:Cardiovascular Diseases / Q000628:therapy*; D017147:Defibrillators, Implantable; D005260:Female; D006333:Heart Failure / Q000503:physiopathology; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged