title: Double-counting of intracardiac electrogram during biatrial pacing.
abstract: BACKGROUND
  Biatrial pacing has a significant problem with memory function that misinterprets normal sinus rhythm as atrial tachyarrhythmias and in addition estimation of the atrial pacing thresholds (biatrial and uniatrial pacing thresholds) is sometimes difficult because of small P waves.
  
  
  RESULTS
  The intracardiac electrograms recorded by a pacemaker in 10 patients (age, 66.7+/-10.7 (SD) years) with implanted biatrial pacemakers were analyzed. Atrial sensing within the atrial refractory period after atrial pacing was counted in 6 of the 10 patients (timing of the double counting was 143+/-64 ms) when pacing failed in the left or right atrium. Atrial sensing within the atrial refractory period after atrial pacing disappeared when biatrial pacing was successfully performed. Atrial double-counts depend on interatrial conduction delay. The memory function of implanted pacemaker devices misinterpreted normal sinus rhythm as atrial tachyarrhythmias because of atrial double-counts. On the other hand, the biatrial pacing threshold was easily recognized using this phenomenon.
  
  
  CONCLUSIONS
  The memory function of pacemaker devices is unreliable because of atrial double-counting during sinus rhythm in patients with biatrial pacing. However, the biatrial pacing threshold is easily checked using this phenomenon.
authors.affiliation: Second Department of Internal Medicine, Yokohama City University School of Medicine, Japan. tishika@med.yokohama-cu.ac.jp
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Shinichi
authors.initials: S
authors.lastname: Sumita
authors.forename: Youhei
authors.initials: Y
authors.lastname: Yamakawa
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ohkusu
authors.forename: Kohei
authors.initials: K
authors.lastname: Matsusita
authors.forename: Katsumi
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Ichirou
authors.initials: I
authors.lastname: Nakazawa
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Mochida
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Ebina
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Uchino
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kimura
authors.forename: Satoshi
authors.initials: S
authors.lastname: Umemura
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation; D002304:Cardiac Pacing, Artificial / Q000592:standards*; D004562:Electrocardiography; D004868:Equipment Failure; D019544:Equipment Failure Analysis; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System; D006801:Humans; D008297:Male; D008838:Microcomputers; D008875:Middle Aged; D019919:Prosthesis Implantation; D013612:Tachycardia, Ectopic Atrial