title: Response of type I atrial fibrillation to atrial pacing in humans.
abstract: BACKGROUND
  High-density mapping studies of atrial fibrillation (AF) have suggested the presence of an excitable gap. The purpose of this study was to assess the local and left atrial response to pacing at the high right atrium during type I AF in humans.
  
  
  RESULTS
  Pacing was performed at the high right atrium during type I AF in 24 patients in the electrophysiology laboratory. The response to pacing was assessed at cycle lengths 10, 20, 30, 40, and 50 ms less than the mean baseline atrial cycle length. Digitized tracings of the baseline tachycardia and the response to pacing were recorded from the high right atrium and from the distal coronary sinus. Computer analysis of these signals was used to calculate a left atrial electrogram density before, during, and after pacing. Two hundred eight-eight segments of AF with a duration of 3.9 +/- 0.5 seconds (mean +/- SD) were analyzed. Local capture of the right atrium during AF was demonstrated for at least one pacing cycle length in each patient. The left atrial electrogram density was significantly greater than baseline at each pacing cycle length that resulted in local capture, except when pacing at 50 ms less than the mean AF cycle length. There was no significant change in the baseline left atrial electrogram density compared with baseline when pacing did not result in local capture of AF.
  
  
  CONCLUSIONS
  Local right atrial capture is often possible by pacing during type I AF and consistently influences the left atrial electrograms recorded in the coronary sinus. These results confirm the presence of excitable tissue in the right and left atria in type I AF.
authors.affiliation: Department of Internal Medicine, University of Michigan, Ann Arbor 48109-0022, USA.
authors.forename: E G
authors.initials: EG
authors.lastname: Daoud
authors.forename: B
authors.initials: B
authors.lastname: Pariseau
authors.forename: M
authors.initials: M
authors.lastname: Niebauer
authors.forename: F
authors.initials: F
authors.lastname: Bogun
authors.forename: R
authors.initials: R
authors.lastname: Goyal
authors.forename: M
authors.initials: M
authors.lastname: Harvey
authors.forename: K C
authors.initials: KC
authors.lastname: Man
authors.forename: S A
authors.initials: SA
authors.lastname: Strickberger
authors.forename: F
authors.initials: F
authors.lastname: Morady
mesh_terms: D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000628:therapy*; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged