title: Bimodal RR interval distribution in chronic atrial fibrillation: impact of dual atrioventricular nodal physiology on long-term rate control after catheter ablation of the posterior atrionodal input.
abstract: BACKGROUND
  Radiofrequency (RF) catheter modification of the AV node in patients with atrial fibrillation (AF) is limited by an unpredictable decrease of the ventricular rate and a high incidence of permanent AV block. A bimodal RR histogram has been suggested to serve as a predictor for successful outcome but the corresponding AV node properties have never been characterized. We hypothesized that a bimodal histogram indicates dual AV nodal physiology and predicts a better outcome after AV node modification in chronic AF.
  
  
  RESULTS
  Thirty-seven patients were prospectively subdivided into two groups according to the RR histogram of 24-hour ECG monitoring. Before to RF ablation, internal cardioversion and programmed stimulation were performed. Among the 22 patients (group I) with a bimodal RR histogram, dual AV nodal physiology was found in 17 (77%) patients. Ablation significantly decreased ventricular rate with loss of the peak of short RR cycles after ablation (mean and maximal ventricular rates: 32% and 35% rate reduction, respectively; P < 0.01). In 15 patients with a unimodal RR histogram (group II), dual AV nodal physiology was found in 2 (13%), and rate reductions were 16% and 17%, respectively. At 6 months, 3 (14%) patients in group I and 6 (40%) in group II underwent elective AV nodal ablation with pacemaker implantation due to intolerable rapid ventricular response to AF.
  
  
  CONCLUSIONS
  Bimodal RR interval distribution during chronic AF suggests the presence of dual AV nodal physiology and predicts a better outcome of RF ablation of the posterior atrionodal input.
authors.affiliation: Department of Cardiology, Medical School Hannover, Germany. Tebbenjohanns.Juergen@MH-Hannover.de
authors.forename: J
authors.initials: J
authors.lastname: Tebbenjohanns
authors.forename: B
authors.initials: B
authors.lastname: Schumacher
authors.forename: T
authors.initials: T
authors.lastname: Korte
authors.forename: M
authors.initials: M
authors.lastname: Niehaus
authors.forename: D
authors.initials: D
authors.lastname: Pfeiffer
mesh_terms: D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000628:therapy; D001283:Atrioventricular Node / Q000503:physiopathology* / Q000601:surgery; D006328:Cardiac Catheterization; D002304:Cardiac Pacing, Artificial; D017115:Catheter Ablation; D002908:Chronic Disease; D015716:Electrocardiography, Ambulatory; D005260:Female; D006327:Heart Block / Q000517:prevention & control; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D011446:Prospective Studies; D016276:Ventricular Function / Q000502:physiology*