title: Randomized pilot study of a new atrial-based minimal ventricular pacing mode in dual-chamber implantable cardioverter-defibrillators.
abstract: OBJECTIVE
  We hypothesized that a new minimal ventricular pacing mode (MVP) that provides AAI/R pacing with ventricular monitoring and back-up DDD/R pacing as needed during AV block (AVB) would significantly reduce cumulative percent ventricular pacing compared to DDD/R.
  
  
  BACKGROUND
  Conventional DDD/R mode often results in high cumulative percent ventricular pacing that may adversely affect ventricular function and increase risk of heart failure and atrial fibrillation.
  
  
  METHODS
  MVP was made operational in 30 patients with DDD/R implantable cardioverter-defibrillators (ICDs) and no history of AVB. Patients were randomized to one week each in DDD/R and MVP. Holter monitor recordings (ECG, intracardiac electrograms, and event markers) and device diagnostics were analyzed for cumulative % atrial paced (Cum%AP), cumulative percent ventricular pacing, and frequency and duration of DDD/R pacing back-up. Diaries were used to report symptoms.
  
  
  RESULTS
  Age of the study population was 61 years +/- 12 years and 83% were male. Baseline PR interval was 204 ms +/- 32 ms and programmed AV intervals (DDD/R) were 200 ms +/- 50 ms (paced)/167 ms +/- 54 ms (sensed). Cum%AP was similar between MVP and DDD/R (47.9 +/- 37 vs 46.3 +/- 36). Cumulative percent ventricular pacing was significantly lower in MVP vs DDD/R (3.79 +/- 16.3 vs 80.6 +/- 33.8, P < .0001). Back-up DDD/R pacing during MVP operation due to transient AVB occurred in 10% of patients (9.3 +/- 7.4 [range 1-15] episodes/patient-day, duration 39.7 minutes +/- 156 minutes). Fifteen percent of AV intervals during MVP operation exceeded 300 ms. No significant symptoms were reported during MVP operation.
  
  
  CONCLUSIONS
  MVP dramatically reduced cumulative percent ventricular pacing compared to DDD/R while maintaining AV synchrony and providing sensor-modulated atrial pacing support. Intermittent oscillations between MVP and DDD/R during transient AV block appeared safe and well tolerated.
authors.affiliation: Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA. mosweeney@partners.org
authors.forename: Michael O
authors.initials: MO
authors.lastname: Sweeney
authors.forename: Julie B
authors.initials: JB
authors.lastname: Shea
authors.forename: Victoria
authors.initials: V
authors.lastname: Fox
authors.forename: Stuart
authors.initials: S
authors.lastname: Adler
authors.forename: Linda
authors.initials: L
authors.lastname: Nelson
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Mullen
authors.forename: Paul
authors.initials: P
authors.lastname: Belk
authors.forename: David
authors.initials: D
authors.lastname: Casavant
authors.forename: Todd
authors.initials: T
authors.lastname: Sheldon
mesh_terms: D001283:Atrioventricular Node / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D018592:Cross-Over Studies; D017147:Defibrillators, Implantable; D004554:Electric Countershock; D015716:Electrocardiography, Ambulatory; D005260:Female; D006327:Heart Block / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011446:Prospective Studies; D016037:Single-Blind Method; D016896:Treatment Outcome