title: Differences in atrial fibrillation properties under vagal nerve stimulation versus atrial tachycardia remodeling.
abstract: BACKGROUND
  There are many similarities between atrial effects of atrial tachycardia remodeling (ATR) and vagal nerve stimulation (VS): both promote atrial fibrillation (AF), reduce atrial effective refractory period (AERP) and AERP rate accommodation, enhance AERP heterogeneity, and increase inward-rectifier K+ current.
  
  
  OBJECTIVE
  This study sought to compare the consequences of ATR and VS at similar levels of AERP abbreviation in dogs.
  
  
  METHODS
  ATR dogs (n = 6) were subjected to 7-day atrial tachypacing at 400 beats/min, with radiofrequency-induced atrioventricular block and ventricular demand pacing (80 beats/min) to control ventricular response. VS was applied in 6 matched dogs with stimulation parameters selected to produce similar mean AERP values to ATR dogs.
  
  
  RESULTS
  ATR and VS produced similarly short AERPs (79 +/- 12 and 80 +/- 12 ms, respectively), AERP rate-adaptation loss, and AERP heterogeneity increases. Although both ATR and VS increased AF duration, VS was significantly more effective in AF promotion, with mean AF duration of 992 +/- 134 seconds, versus 440 +/- 240 seconds (P <.05) under ATR. The greater AF-promoting effect of VS was associated with greater mean dominant frequency values during AF (11.7 +/- 1.8 versus 10.0 +/- 1.3 Hz ATR, P <.05). VS greatly enhanced the spatial dominant frequency variability, increasing the coefficient of variation to 15.2 +/- 1.9 Hz, versus 8.9 +/- 1.5 Hz for ATR (P <.05), primarily by increasing the per-dog maximum dominant frequency (15.4 +/- 0.6 Hz versus 12.5 +/- 0.6 for ATR, P <.01).
  
  
  CONCLUSIONS
  For matched AERP values, VS promotes AF more strongly than ATR. Despite similar AERP changes, VS produces considerably greater increases in dominant frequencies, particularly maximum values, consistent with previous suggestions that inward-rectifier K+ current enhancement is particularly effective at accelerating and stabilizing spiral wave rotors that maintain AF.
authors.affiliation: Department of Medicine, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada.
authors.forename: Grigorios
authors.initials: G
authors.lastname: Katsouras
authors.forename: Masao
authors.initials: M
authors.lastname: Sakabe
authors.forename: Philippe
authors.initials: P
authors.lastname: Comtois
authors.forename: Ange
authors.initials: A
authors.lastname: Maguy
authors.forename: Brett
authors.initials: B
authors.lastname: Burstein
authors.forename: Peter G
authors.initials: PG
authors.lastname: Guerra
authors.forename: Mario
authors.initials: M
authors.lastname: Talajic
authors.forename: Stanley
authors.initials: S
authors.lastname: Nattel
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000209:etiology / Q000503:physiopathology*; D004285:Dogs; D004594:Electrophysiology; D006325:Heart Atria / Q000503:physiopathology; D006329:Heart Conduction System / Q000503:physiopathology; D012032:Refractory Period, Electrophysiological; D013612:Tachycardia, Ectopic Atrial / Q000150:complications / Q000503:physiopathology*; D055536:Vagus Nerve Stimulation