title: Predictors of resuscitation in a swine model of ischemic and nonischemic ventricular fibrillation cardiac arrest: superiority of amplitude spectral area and slope to predict a return of spontaneous circulation when resuscitation efforts are prolonged.
abstract: OBJECTIVE
  We have demonstrated that a return of spontaneous circulation in the first 3 mins of resuscitation in swine is predicted by ventricular fibrillation waveform (amplitude spectral area or slope) when untreated ventricular fibrillation duration or presence of acute myocardial infarction is unknown. We hypothesized that in prolonged resuscitation efforts that return of spontaneous circulation immediately after a second or later shock with postshock chest compression is independently predicted by end-tidal CO2, coronary perfusion pressure, and ventricular fibrillation waveform measured before that shock in a swine model of ischemic and nonischemic ventricular fibrillation arrest.
  
  
  METHODS
  Animal intervention study with comparison to a control group.
  
  
  METHODS
  University animal laboratory.
  
  
  METHODS
  Twenty swine.
  
  
  METHODS
  Myocardial infarction was induced by steel plug occlusion of the left anterior descending coronary artery. Ventricular fibrillation was untreated for 8 mins in normal swine (n=10) and acute myocardial infarction swine (n=10).
  
  
  RESULTS
  End-tidal CO2, coronary perfusion pressure, and ventricular fibrillation waveform characteristics of amplitude spectral area and slope were analyzed before second or later shocks. For an amplitude spectral area>35 mV-Hz, the odds ratio for achieving return of spontaneous circulation after that shock was 72 (95% confidence interval, 3.8-1300; p=.004) compared with an amplitude spectral area<28 mV-Hz and with an area under the receiver operator characteristic curve of 0.86. For slope>3.6 mV/s, the odds ratio for achieving return of spontaneous circulation was 36 (95% confidence interval, 2.7-480; p=.007) compared with slope<2.72 mV/s with an area under the curve of 0.86. End-tidal CO2 and coronary perfusion pressure were not predictive of return of spontaneous circulation after a shock, although coronary perfusion pressure was significantly related to both amplitude spectral area (p<.001) and slope (p<.001).
  
  
  CONCLUSIONS
  : In prolonged untreated ventricular fibrillation arrest, the waveform characteristics of amplitude spectral area and slope predict the attainment of return of spontaneous circulation with a second or later shock. This has implications for the ideal means to customize the timing of shocks and chest compressions when return of spontaneous circulation is not promptly obtained.
authors.affiliation: Sarver Heart Center, Department of Internal Medicine, The University of Arizona College of Medicine, Tucson, AZ, USA. jindik@arizona.edu
authors.forename: Julia H
authors.initials: JH
authors.lastname: Indik
authors.forename: Daniel
authors.initials: D
authors.lastname: Allen
authors.forename: Madhan
authors.initials: M
authors.lastname: Shanmugasundaram
authors.forename: Mathias
authors.initials: M
authors.lastname: Zuercher
authors.forename: Ronald W
authors.initials: RW
authors.lastname: Hilwig
authors.forename: Robert A
authors.initials: RA
authors.lastname: Berg
authors.forename: Karl B
authors.initials: KB
authors.lastname: Kern
mesh_terms: D000818:Animals; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D003326:Coronary Circulation / Q000502:physiology*; D004195:Disease Models, Animal; D004554:Electric Countershock / Q000379:methods*; D006323:Heart Arrest / Q000209:etiology / Q000401:mortality / Q000628:therapy*; D006334:Heart Function Tests; D009203:Myocardial Infarction / Q000150:complications*; D011237:Predictive Value of Tests; D011897:Random Allocation; D020127:Recovery of Function; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D015996:Survival Rate; D013552:Swine; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000150:complications*