title: Dynamic ventricular overdrive stimulation in atrial fibrillation: effects on ventricular rate irregularity, ventricular pacing, and fusion beats.
abstract: OBJECTIVE
  In pacemaker patients with preserved atrio-ventricular (AV) conduction, atrial fibrillation (AF) can lead to symptomatic ventricular rate irregularity and loss of ventricular stimulation. We tested if dynamic ventricular overdrive (DVO) as a potentially pacemaker-integrated algorithm could improve both aspects.
  
  
  RESULTS
  Different settings of DVO and ventricular-ventricular-inhibited-pacing (VVI) with different base rates were tested in two consecutive phases during electrophysiological studies for standard indications. Mean heart rate (HR), HR irregularity and percentage of ventricular pacing were evaluated. A fusion index (FI) indicative of the proportion of fusion beats was calculated for each stimulation protocol. Dynamic ventricular overdrive from the right ventricular apex was acutely applied in 38 patients (11 females, mean age 62.1 ± 11.5 years) with sustained AF and preserved AV conduction. Dynamic ventricular overdrive at LOW/MEDIUM setting increased the amount of ventricular pacing compared with VVI pacing at 60, 70, and 80 beats per minute (bpm; to 81/85% from 11, 25, and 47%, respectively; P < 0.05). It also resulted in a maximum decrease in interval differences (to 48 ± 18 ms from 149 ± 28, 117 ± 38, and 95 ± 46 ms, respectively; P < 0.05) and fusion (to 0.13 from 0.41, 0.42, and 0.36, respectively; P < 0.05) compared with VVI pacing at 60, 70, and 80 bpm. However, the application of DVO resulted in a significant increase in HR compared with intrinsic rhythm and VVI pacing at 80 bpm (to 97 bpm from 89 and 94 bpm, respectively; P < 0.05).
  
  
  CONCLUSIONS
  Dynamic ventricular overdrive decreases HR irregularity and increases ventricular pacing rate compared with VVI pacing at fixed elevated base rates and spontaneous rhythm. Fusion index might help to refine information on pacing percentages provided by device counters.
authors.affiliation: Klinikum Coburg, II. Medizinische Klinik, Coburg, Germany. georgnoelker@yahoo.com
authors.forename: Georg
authors.initials: G
authors.lastname: Nölker
authors.forename: Klaus-Jürgen
authors.initials: KJ
authors.lastname: Gutleben
authors.forename: Stefan
authors.initials: S
authors.lastname: Asbach
authors.forename: Guido
authors.initials: G
authors.lastname: Ritscher
authors.forename: Harald
authors.initials: H
authors.lastname: Marschang
authors.forename: Anil M
authors.initials: AM
authors.lastname: Sinha
authors.forename: Peter
authors.initials: P
authors.lastname: Boileau
authors.forename: Michael E
authors.initials: ME
authors.lastname: Benser
authors.forename: Benoit
authors.initials: B
authors.lastname: Hallier
authors.forename: Alexander
authors.initials: A
authors.lastname: Hümmer
authors.forename: Johannes
authors.initials: J
authors.lastname: Brachmann
mesh_terms: D000368:Aged; D000465:Algorithms; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000628:therapy; D001283:Atrioventricular Node / Q000503:physiopathology; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial / Q000145:classification; D016683:Supine Position