title: Irregularity of the ventricular rhythm during atrial fibrillation: effect of slow atrioventricular nodal pathway ablation.
abstract: BACKGROUND
  The contribution of dual atrioventricular (AV) nodal pathway physiology to the irregularity of the ventricular rhythm during atrial fibrillation has not been clarified.
  
  
  OBJECTIVE
  This study was performed to assess the effects of slow AV nodal pathway ablation on the irregularity of the ventricular rhythm during atrial fibrillation.
  
  
  METHODS
  Irregularity of the ventricular rhythm was quantified using analysis of heart rate variability. In 20 patients with AV nodal reentrant tachycardia, absolute heart rate variability during atrial fibrillation was quantified before and after slow AV nodal pathway ablation by the standard deviation of all NN intervals (SDNN). Relative heart rate variability was determined by computing the coefficient of variation, SDNN normalized for the standard deviation of the mean ventricular cycle length (MVCL-AF).
  
  
  RESULTS
  The slope of the regression between MVCL-AF and SDNN was significantly more gradual after slow pathway ablation (slope 0.39 vs. 0.23, p < 0.001). Coefficient of variation increased in 12 patients with heart rates > 120 beats/min at baseline (18.6 +/- 3.9 vs. 22.1 +/- 2.7% MVCL-AF, p < 0.05), but decreased in 8 patients with heart rates < 120 beats/min at baseline (25.6 +/- 3.1 vs. 22.2 +/- 2.2% MVCL-AF, p = 0.05). Furthermore, coefficient of variation correlated with MVCL-AF only at baseline (slope 0.034, r = 0.66), but no relation was found after slow pathway ablation (slope 0, r = 0).
  
  
  CONCLUSIONS
  Slow AV nodal pathway ablation alters the relation between absolute heart rate variability and mean ventricular rate during atrial fibrillation and eliminates cycle length dependency of relative heart rate variability. These data indicate that dual AV nodal pathway physiology contributes to the irregularity of the ventricular rhythm during atrial fibrillation.
authors.affiliation: Department of Cardiology, University of Vienna, Austria.
authors.forename: B
authors.initials: B
authors.lastname: Frey
authors.forename: G
authors.initials: G
authors.lastname: Kreiner
authors.forename: B
authors.initials: B
authors.lastname: Liebisch
authors.forename: S
authors.initials: S
authors.lastname: Sauermann
authors.forename: H D
authors.initials: HD
authors.lastname: Gössinger
mesh_terms: D000328:Adult; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000601:surgery; D017115:Catheter Ablation; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology* / Q000601:surgery; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000503:physiopathology; D016896:Treatment Outcome