title: Endocardial vagal atrioventricular node stimulation in humans: reproducibility on 18-month follow-up.
abstract: OBJECTIVE
  Control of atrioventricular (AV) node conduction by means of high-frequency stimulation (HFS) of efferent AV node vagal stimulation (AVNS) fibres enables the ventricular rate (VR) to be modulated during atrial fibrillation (AF). The aims of this study were to verify, on 18-month follow-up, the reproducibility of the dromotropic effect obtained on implantation and the long-term reliability of the system in patients who received an implantable cardioverter-defibrillator (ICD) with a standard atrial lead positioned at a location suitable for AVNS.
  
  
  RESULTS
  We enrolled 12 patients with paroxysmal or persistent AF who were candidates for ICD. The right atrium was mapped to locate the pacing site, and a transvenous screw-in lead was implanted in that region. The voltages required for VR modulation (25% VR reduction) and complete AV block at different pulse durations (from 0.1 to 0.5 ms) were recorded. Eleven out of 12 patients underwent 18-month follow-up examination. Atrial pacing parameters were adequate and did not differ from the baseline values (all P > 0.05): pacing threshold 0.9 ± 0.5 V (0.5 ms pulse duration) and impedance 556 ± 121 Ω, with P-wave amplitude of 1.6 ± 0.7 mV. High-frequency stimulation induced VR modulation in nine patients and complete AV block in eight patients at pulse durations ≥0.3 ms. No differences were observed in the voltages for VR modulation and complete AV block between implantation and 18-month examination (all P > 0.100).
  
  
  CONCLUSIONS
  Ventricular rate control during AF was obtained under HFS 18 months after implantation in patients with the atrial lead positioned at a location suitable for AVNS. The pacing outputs needed to achieve the dromotropic effect were comparable to those measured on implantation.
authors.affiliation: Department of Medicine, Electrophysiology and Pacing Unit, Belcolle Hospital, Viterbo, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Rossi
authors.forename: Stefano
authors.initials: S
authors.lastname: Bianchi
authors.forename: Sergio
authors.initials: S
authors.lastname: Valsecchi
authors.forename: Daniele
authors.initials: D
authors.lastname: Porcelli
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Sgreccia
authors.forename: Antonio
authors.initials: A
authors.lastname: Lucifiero
authors.forename: Sergio
authors.initials: S
authors.lastname: Canonaco
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Campoli
authors.forename: Mario
authors.initials: M
authors.lastname: Malavasi
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Piccirillo
authors.forename: Raffaele
authors.initials: R
authors.lastname: Quaglione
authors.forename: Paolo
authors.initials: P
authors.lastname: Azzolini
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000628:therapy*; D001283:Atrioventricular Node / Q000502:physiology*; D002304:Cardiac Pacing, Artificial / Q000379:methods; D017147:Defibrillators, Implantable; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000502:physiology*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D016896:Treatment Outcome