title: Ventricular fibrillation scaling exponent can guide timing of defibrillation and other therapies.
abstract: BACKGROUND
  The scaling exponent (ScE) of the ventricular fibrillation (VF) waveform correlates with duration of VF and predicts defibrillation outcome. We compared 4 therapeutic approaches to the treatment of VF of various durations.
  
  
  RESULTS
  Seventy-two swine (19.5 to 25.7 kg) were randomly assigned to 1 of 9 groups (n=8 each). VF was induced and left untreated until the ScE reached 1.10, 1.20, 1.30, or 1.40. Animals were treated with either immediate countershock (IC); 3 minutes of CPR before the first countershock (CPR); CPR for 2 minutes, then drugs given with 3 more minutes of CPR before the first shock (CPR-D); or drugs given at the start of CPR with 3 minutes of CPR before the first shock (Drugs+CPR). Return of spontaneous circulation (ROSC) and 1-hour survival were analyzed with chi2 and Kaplan-Meier survival curves. IC was effective when the ScE was low but had decreasing success as the ScE increased. No animals in the 1.30 or 1.40 groups had ROSC from IC (0 of 16). CPR did not improve first shock outcome in the 1.20 CPR group (3 of 8 ROSC). Kaplan-Meier survival analyses indicated that IC significantly delayed time to ROSC in both the 1.3 (P=0.0006) and the 1.4 (P=0.005) groups.
  
  
  CONCLUSIONS
  VF of brief to moderate duration is effectively treated by IC. When VF is prolonged, as indicated by an ScE of 1.3 or greater, IC was not effective and delayed time to ROSC. The ScE can help in choosing the first intervention in the treatment of VF.
authors.affiliation: Department of Emergency Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pa, USA. menegazz+@pitt.edu
authors.forename: James J
authors.initials: JJ
authors.lastname: Menegazzi
authors.forename: Clifton W
authors.initials: CW
authors.lastname: Callaway
authors.forename: Lawrence D
authors.initials: LD
authors.lastname: Sherman
authors.forename: David P
authors.initials: DP
authors.lastname: Hostler
authors.forename: Henry E
authors.initials: HE
authors.lastname: Wang
authors.forename: Kristofer C
authors.initials: KC
authors.lastname: Fertig
authors.forename: Eric S
authors.initials: ES
authors.lastname: Logue
mesh_terms: D000818:Animals; D016887:Cardiopulmonary Resuscitation; D004554:Electric Countershock; D005260:Female; D015993:Life Tables; D008297:Male; D016019:Survival Analysis; D013552:Swine; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000503:physiopathology* / Q000628:therapy