title: Distribution of fast heart rate episodes during paroxysmal atrial fibrillation.
abstract: OBJECTIVE
  To investigate the defibrillator waiting time (time between the recognition of atrial fibrillation and the actual shock) by studying paroxysmal atrial fibrillation episodes with RR intervals shorter than a certain limit (that is, episodes during which defibrillation should not be attempted).
  
  
  METHODS
  Long term 24 hour Holter recordings from a digoxin v placebo crossover study in patients with paroxysmal atrial fibrillation were analysed. In all, 23 recordings with atrial fibrillation episodes of at least 1000 ventricular cycles and with < 20% Holter artefacts or noise were used (11 recorded on placebo and 12 on digoxin). For each recording, the mean ("mean waiting time") and maximum ("maximum waiting time") duration of continuous sections of atrial fibrillation episodes with all RR intervals shorter than a certain threshold were evaluated, ranging the threshold from 400 to 1000 ms in 10 ms steps. For each threshold, the mean and maximum waiting times were compared between recordings on placebo and on digoxin.
  
  
  RESULTS
  Both the mean and maximum waiting times increased exponentially with increasing threshold. Practically acceptable mean waiting times less than one minute were observed with thresholds below 600 ms. There were no significant differences in mean waiting times and maximum waiting times between recordings on placebo and digoxin, and only a trend towards shorter waiting times on digoxin.
  
  
  CONCLUSIONS
  Introduction of a minimum RR interval threshold required to deliver atrial defibrillation leads to practically acceptable delays between atrial fibrillation recognition and the actual shock. These delays are not prolonged by digoxin treatment.
authors.affiliation: Department of Cardiological Sciences, St George's Hospital Medical School, London, UK. k.hnatkova@sghms.ac.uk
authors.forename: K
authors.initials: K
authors.lastname: Hnatkova
authors.forename: F D
authors.initials: FD
authors.lastname: Murgatroyd
authors.forename: C A
authors.initials: CA
authors.lastname: Alferness
authors.forename: A J
authors.initials: AJ
authors.lastname: Camm
authors.forename: M
authors.initials: M
authors.lastname: Malik
mesh_terms: D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000188:drug therapy / Q000503:physiopathology* / Q000628:therapy; D002304:Cardiac Pacing, Artificial; D018592:Cross-Over Studies; D004077:Digoxin / Q000627:therapeutic use*; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D013997:Time Factors
chemical_list: D000889:Anti-Arrhythmia Agents; D004077:Digoxin