title: The impact of the distance between the atrial electrode and the atrial wall on atrial undersensing in patients with VDD pacemakers: long-term follow-up.
abstract: OBJECTIVE
  Atrial undersensing (AUS) in single-lead VDD pacemakers may be due to diminished P-wave amplitude secondary to local inflammation beneath the electrodes closer to atrial wall. The aim of this study was to assess the potential effect of distance between atrial electrode and atrial wall on immediate and long-term atrial sensing stability in VDD systems.
  
  
  METHODS
  A total of 275 patients with normal sinus node function who received VDD pacemakers were enrolled into the study and were followed up for a median duration of 33 months. During each control visit, a standard 12-lead electrocardiogram (ECG) was obtained and standard pacemaker function assessment was performed including testing for pacing threshold and atrioventricular synchrony. The distance between atrial electrode and atrial wall was measured from chest X-ray.
  
  
  RESULTS
  Of the 275 patients, AUS was detected in 59 patients. Univariate predictors of AUS were use of closely spaced bipolar ring atrial electrode (CSBR) (P = 0.01), wider atrial ring-spacing (P = 0.03), and atrial sensitivity programmed to a higher level (P = 0.001). Use of CSBR (P = 0.04) and atrial sensitivity > or =0.3 mV (P = 0.02) were observed to be the independent predictors for AUS. When the distance between atrial electrode and atrial wall was <7 mm, AUS was less with diagonally arranged bipolar ring electrodes (DABR) than it was with CSBRs (P = 0.02).
  
  
  CONCLUSIONS
  The distance between atrial electrode and atrial wall does not appear to affect AUS incidence in VDD pacemakers. For VDD electrodes closer to atrial wall, AUS was significantly less likely in DABR-type electrodes.
authors.affiliation: Ankara University School of Medicine, Department of Cardiology, Ankara, Turkey.
authors.forename: Timucin
authors.initials: T
authors.lastname: Altin
authors.forename: Muharrem
authors.initials: M
authors.lastname: Guldal
authors.forename: Basar
authors.initials: B
authors.lastname: Candemir
authors.forename: Cegerhun
authors.initials: C
authors.lastname: Polat
authors.forename: Aydan O
authors.initials: AO
authors.lastname: Ozdemir
authors.forename: Cansin
authors.initials: C
authors.lastname: Tulunay
authors.forename: Cagdas
authors.initials: C
authors.lastname: Ozdol
authors.forename: Omer
authors.initials: O
authors.lastname: Akyurek
authors.forename: Remzi
authors.initials: R
authors.lastname: Karaoguz
authors.forename: Cetin
authors.initials: C
authors.lastname: Erol
mesh_terms: D004562:Electrocardiography; D004567:Electrodes, Implanted; D005260:Female; D005500:Follow-Up Studies; D006325:Heart Atria / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial