title: The effect of bipole tip-to-ring distance in atrial electrodes upon atrial tachyarrhythmia sensing capability in modern dual-chamber pacemakers.
abstract: BACKGROUND
  Accurate atrial arrhythmia discrimination is important for dual chamber pacemakers and defibrillators. The aim was to assess the accuracy of atrial arrhythmia recording using modern devices and relate this to atrial tip-to-ring (TTR) distance.
  
  
  METHODS
  One hundred eighty-two patients (72 + or - 9 years, 55% male) with paroxysmal atrial fibrillation were enrolled and were included in the study if they had an atrial fibrillation (AF) burden of 1-50% during a monitoring phase. Seventy-nine patients fulfilled these criteria and were followed for at least 5 months. Electrodes were classified as having short (<10 mm), medium (10-12), or long (13-18) atrial TTR spacing.
  
  
  RESULTS
  Two thousand eight hundred eighty-three detailed onset reports were analyzed; 730 (25%) demonstrated aberrant sensing. Six percent were due to farfield R wave oversensing (FFRWO) and 19% due to undersensing, sometimes occurring in the same patient and study phase. FFRWO was significantly reduced with short TTR electrodes (P < 0.05). Undersensing due to sensitivity fallout was 18% (short), 24% (medium), and 17% (long) (P = ns). Undersensing due to pacemaker blanking was 11% (short), 11% (medium), and 12% (long) (P = ns). Active fixation electrodes did not show any difference from passive fixation.
  
  
  CONCLUSIONS
  Atrial electrodes with a short TTR (<10 mm) significantly reduce FFRWO without increasing undersensing and should be used routinely in patients with paroxysmal atrial tachyarrhythmias. However, 20% of atrial tachyarrythmia episodes were incorrectly classified as terminated by these modern devices due to undersensing. Clinicians should be wary of using device-derived endpoints that rely on AF episode number or duration as these may be falsely increased or reduced, respectively.
authors.affiliation: Cardiology Department, Eastbourne General Hospital, Eastbourne, UK.
authors.forename: John
authors.initials: J
authors.lastname: Silberbauer
authors.forename: Anita
authors.initials: A
authors.lastname: Arya
authors.forename: Rick A
authors.initials: RA
authors.lastname: Veasey
authors.forename: Lana
authors.initials: L
authors.lastname: Boodhoo
authors.forename: Kayvan
authors.initials: K
authors.lastname: Kamalvand
authors.forename: Sean
authors.initials: S
authors.lastname: O'Nunain
authors.forename: David
authors.initials: D
authors.lastname: Hildick-Smith
authors.forename: Vince
authors.initials: V
authors.lastname: Paul
authors.forename: Nikhil R
authors.initials: NR
authors.lastname: Patel
authors.forename: Guy W
authors.initials: GW
authors.lastname: Lloyd
authors.forename: Neil
authors.initials: N
authors.lastname: Sulke
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis; D004566:Electrodes; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D010138:Pacemaker, Artificial; D012680:Sensitivity and Specificity; D013610:Tachycardia / Q000175:diagnosis*