title: Predictors of loss of atrioventricular synchrony in single lead VDD pacing.
abstract: OBJECTIVE
  To evaluate maintenance of proper VDD function, defined as persistence of sinus rhythm with atrial synchronous ventricular pacing, and to define factors predicting failure of the VDD mode in patients with atrioventricular (AV) block and normal sinus function.
  
  
  METHODS
  Observational study in 86 consecutive patients (mean (SD) age 74 (12) years; 38 women, 48 men) with single lead VDD pacing systems (Intermedics Unity, n = 66, Medtronic Thera VDD, n = 20), implanted for high degree AV block with documented normal sinus node. Pacemaker function was assessed by event counters, telemetric measurements, and Holter recordings. Demographic, radiological, and pacing variables were correlated with loss of proper VDD function.
  
  
  RESULTS
  During a mean (SD) follow up of 10 (10) months (range 1-37), sinus rhythm and atrial triggered ventricular pacing were maintained in 70 of 86 patients (81%). Atrial undersensing was observed in nine patients, lead migration in two, atrial fibrillation in three, and symptomatic sinus bradycardia in two. Univariate predictors of loss of proper VDD function were: low position of the atrial dipole relative to the carina (> or = 6 cm; p < 0.01) during fluoroscopy; and maximum programmable atrial sensitivity of the pacemaker (p = 0.03). In a multivariate analysis, only dipole position remained predictive of outcome (p < 0.02). Not predictive were sex, age, symptoms before pacemaker implantation, cardiothoracic ratio or dilatation of individual heart chambers on chest x ray, side of device implant, and P wave amplitude at implant.
  
  
  CONCLUSIONS
  To maintain proper VDD function in the long term, a low anatomical dipole position relative to the carina should be avoided. Electrical guidance of dipole positioning does not seem to influence long term outcome.
authors.affiliation: Division of Cardiology, University Hospital, Basel, Switzerland. HunzikerPA@ubaclu.unibas.ch
authors.forename: P
authors.initials: P
authors.lastname: Hunziker
authors.forename: P
authors.initials: P
authors.lastname: Buser
authors.forename: M
authors.initials: M
authors.lastname: Pfisterer
authors.forename: F
authors.initials: F
authors.lastname: Burkart
authors.forename: S
authors.initials: S
authors.lastname: Osswald
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000209:etiology*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D015331:Cohort Studies; D005260:Female; D006327:Heart Block / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D018709:Statistics, Nonparametric; D017211:Treatment Failure