title: Defibrillation success is not associated with near field electrogram complexity or shock timing.
abstract: BACKGROUND
  It has been suggested that more-complex fibrillation requires higher energy shocks to terminate. Furthermore, animal studies have demonstrated that shock timing also plays a role. The objective of this study was to test these assertions in a clinical context.
  
  
  METHODS
  Near- and far-field electrograms were collected during defibrillation threshold testing. Fibrillation complexity was measured by quantifying the organization in the signals with wavelet-based methods, scaling exponent, and cross-correlation analysis. Receiver operator characteristic curves were used to determine predictive value. The effect of the phase at which defibrillation shocks were applied was also determined.
  
  
  RESULTS
  No measure was able to classify whether a particular shock would be successful. All performed very poorly. Shock timing played no role in defibrillation outcome.
  
  
  CONCLUSIONS
  Signal organization of a local electrogram and phase of shock delivery do not relate to minimum defibrillation shock energy immediately after ventricular fibrillation onset.
authors: Department of Electrical and Computer Engineering, University of Calgary, Calgary, Alberta, Canada. edward.vigmond@u-bordeaux1.fr
authors: Edward J
authors: EJ
authors: Vigmond
authors: Shane
authors: S
authors: Kimber
authors: Go
authors: G
authors: Suzuki
authors: Peter
authors: P
authors: Faris
authors: L Joshua
authors: LJ
authors: Leon
mesh_terms: D009202:Cardiomyopathies / Q000150:complications / Q000628:therapy; D003324:Coronary Artery Disease / Q000150:complications / Q000628:therapy; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000379:methods* / Q000592:standards; D022062:Electrophysiologic Techniques, Cardiac / Q000592:standards* / Q000706:statistics & numerical data; D006801:Humans; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity; D013997:Time Factors; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000209:etiology / Q000628:therapy*