title: Differences in the characteristics of induced and spontaneous episodes of ventricular fibrillation.
abstract: OBJECTIVE
  The degree of organization of ventricular fibrillation (VF) can be examined in terms of the regularity of the electrical activity within the ventricle. Using electrograms (EGMs) stored within implanted cardioverter defibrillators (ICDs), we examined the hypothesis that the degree of organization, or regularity, was different if the VF was induced by electrical stimulation as opposed to occurring clinically due to ischemia or scar.
  
  
  RESULTS
  We compared the statistical characteristics of EGMs recorded by ICDs during spontaneous episodes with those induced during device testing in the laboratory in nine subjects. Regularity of the VF EGM signals was quantified using autocorrelation, Shannon entropy (derived from cycle to cycle activation complexes), and Kolmogorov entropy (derived from eight second long episodes of VF). All three measurements showed a statistically greater degree of regularity for induced VF than in spontaneous episodes.
  
  
  CONCLUSIONS
  Analysis of VF EGMs using these techniques is novel and robust, providing a new way for assessing electrical organization during VF. The clinical significance and utility of differences in VF waveform regularity is unclear at this stage.
authors.affiliation: Department of Medicine, University of Auckland, Auckland, New Zealand.
authors.forename: Nigel A
authors.initials: NA
authors.lastname: Lever
authors.forename: Emma G
authors.initials: EG
authors.lastname: Newall
authors.forename: Peter D
authors.initials: PD
authors.lastname: Larsen
mesh_terms: D000328:Adult; D000368:Aged; D017147:Defibrillators, Implantable; D004599:Electric Stimulation Therapy / Q000009:adverse effects*; D004562:Electrocardiography; D015716:Electrocardiography, Ambulatory / Q000379:methods; D019277:Entropy; D005260:Female; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000150:complications* / Q000503:physiopathology; D014693:Ventricular Fibrillation / Q000209:etiology* / Q000503:physiopathology* / Q000628:therapy