title: Human ventricular fibrillation during global ischemia and reperfusion: paradoxical changes in activation rate and wavefront complexity.
abstract: BACKGROUND
  Ischemic ventricular fibrillation in experimental models has been shown to progress through a series of stages. Progression of ischemic VF in the in vivo human heart has not been determined.
  
  
  RESULTS
  We studied 10 patients undergoing cardiac surgery. Ventricular fibrillation was induced by burst pacing. After 30 seconds, global myocardial ischemia was induced by aortic cross-clamp and maintained for 2.5 minutes, followed by coronary reflow. Epicardial activity was sampled (1 kHz) with a sock that contained 256 unipolar contact electrodes. Dominant frequencies were calculated with a fast Fourier transform with a moving window. The locations of phase singularities and activation wavefronts were identified at 10-ms intervals. Preischemic (perfused) ventricular fibrillation was maintained by a disorganized mix of large and small wavefronts. During global myocardial ischemia, mean dominant frequencies decreased from 6.4 to 4.7 Hz at a rate of -0.011±0.002 Hz s(-1) (P<0.001) and then increased rapidly to 7.4 Hz within 30 seconds of reflow. In contrast, the average number of epicardial phase singularities increased during ischemia from 7.7 to 9.7 at a rate of 0.013±0.005 phase singularities per second (P<0.01) and remained unchanged during reflow, at 10.3. The number of wavefronts showed a similar time course to the number of phase singularities.
  
  
  CONCLUSIONS
  In human ventricular fibrillation, we found an increase in complexity of electric activation patterns during global myocardial ischemia, and this was not reversed during reflow despite an increase in activation rate.
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom.
authors.forename: Chris P
authors.initials: CP
authors.lastname: Bradley
authors.forename: Richard H
authors.initials: RH
authors.lastname: Clayton
authors.forename: Martyn P
authors.initials: MP
authors.lastname: Nash
authors.forename: Ayman
authors.initials: A
authors.lastname: Mourad
authors.forename: Martin
authors.initials: M
authors.lastname: Hayward
authors.forename: David J
authors.initials: DJ
authors.lastname: Paterson
authors.forename: Peter
authors.initials: P
authors.lastname: Taggart
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D004195:Disease Models, Animal; D004566:Electrodes; D056149:Epicardial Mapping; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000503:physiopathology*; D015425:Myocardial Reperfusion; D010496:Pericardium / Q000503:physiopathology; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000503:physiopathology*