title: The characteristics of postcountershock pulseless electrical activity may indicate the outcome of CPR.
abstract: OBJECTIVE
  When ventricular fibrillation is cardioverted to pulseless electrical activity (PEA), PEA has been regarded as a non-resuscitatable rhythm. Yet, recent reports and our earlier observations suggested otherwise. We therefore investigated outcomes after postcountershock PEA, and aimed to develop a scoring system for outcome classification at the onset of initial postcountershock PEA.
  
  
  METHODS
  Data from 215 domestic pigs were retrospectively reviewed. VF was induced and untreated for 7 min. Defibrillation was attempted with up to three 150 J biphasic shocks. Failing to restore spontaneous circulation (ROSC), 1 min of CPR preceded subsequent sequences of shocks until animals were resuscitated or for a total of 15 min. Fifty-nine instances of PEA followed defibrillation, including 29 animals that attained ROSC.
  
  
  RESULTS
  ROSC animals required a shorter interval between the first shock and the initial postcountershock PEA, fewer shocks prior to onset of initial postcountershock PEA, demonstrated a greater VF wavelet amplitude prior to onset of initial PEA, smaller QRS intervals, and higher heart rates. Using Fisher's linear discriminant analysis, 79.3% of the ROSC and 63.3% of non-ROSC cases were predicted correctly. A total of 71.2% of all cases were classified correctly.
  
  
  CONCLUSIONS
  Animals in which postcountershock PEA was converted to ROSC required shorter intervals from first shock to initial postcountershock PEA, fewer shocks prior to onset of initial postcountershock PEA, had greater VF wavelet amplitude prior to initial postcountershock PEA, small QRS intervals, and higher heart rates. Fisher's discriminant analysis is helpful in predicting the likelihood of ROSC for an individual animal presenting with postcountershock PEA.
authors.affiliation: Weil Institute of Critical Care Medicine, 35100 Bob Hope Drive, Rancho Mirage, CA, USA.
authors.forename: Xiangshao
authors.initials: X
authors.lastname: Fang
authors.forename: Wanchun
authors.initials: W
authors.lastname: Tang
authors.forename: Shijie
authors.initials: S
authors.lastname: Sun
authors.forename: Jinglan
authors.initials: J
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Huang
authors.forename: Max Harry
authors.initials: MH
authors.lastname: Weil
mesh_terms: D000818:Animals; D001775:Blood Circulation / Q000502:physiology; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D016002:Discriminant Analysis; D004195:Disease Models, Animal; D004554:Electric Countershock; D006323:Heart Arrest / Q000209:etiology / Q000628:therapy*; D011379:Prognosis; D011674:Pulse; D012189:Retrospective Studies; D013552:Swine; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000628:therapy*