title: Course of quantitative ventricular fibrillation waveform measure and outcome following out-of-hospital cardiac arrest.
abstract: BACKGROUND
  Quantitative measures of the ventricular fibrillation waveform at the outset of resuscitation are associated with survival. However, little is known about the course of these measures during resuscitation and how this course is related to outcome.
  
  
  OBJECTIVE
  The purpose of this study was to determine how waveform measures change over the course of resuscitation and whether these changes might be used to guide resuscitation.
  
  
  METHODS
  We evaluated 390 persons treated by emergency providers following out-of-hospital ventricular fibrillation arrest. We assessed the ventricular fibrillation waveform using the amplitude spectrum area (AMSA) from the defibrillator's continuous electrocardiogram measured before each of the first three shocks. We used logistic regression to evaluate the relationship of AMSA and the change in AMSA with favorable neurologic survival as determined by the Cerebral Performance Category at hospital discharge 1-2.
  
  
  RESULTS
  Of the 390 patients who received an initial shock, 273 required a second shock and 210 required a third shock. The mean (standard deviation) for AMSA was 9.64 (0.52) for the 873 total shock cycles. AMSA₁ measured before the first shock was strongly associated with favorable neurologic survival (odds ratio [OR] 3.40, 95% confidence interval [CI] [2.48, 4.66] for 1 SD change). We observed a similar relationship for second-shock AMSA₂ (OR 3.53, 95% CI [2.42, 5.14]) and third-shock AMSA₃ (OR 3.10, 95% CI [2.03, 4.73]). The median change in AMSA was 0.24 for ΔAMSA₁₋₂ and 0.21 for ΔAMSA₂₋₃. A positive median change in AMSA between shocks was associated with favorable neurologic survival (OR 1.44, 95% CI [1.16, 1.80] for ΔAMSA₁₋₂ and OR 1.31, 95% CI [1.01, 1.71] for ΔAMSA₂₋₃).
  
  
  CONCLUSIONS
  Given their prognostic and dynamic qualities, quantitative waveform measures may provide an effective real-time strategy to guide individual treatment and improve survival.
authors.affiliation: Department of Medicine University of Washington School of Medicine, Seattle, Washington.
authors.forename: Peter
authors.initials: P
authors.lastname: Schoene
authors.affiliation: Department of Bioengineering, Seattle, Washington.
authors.forename: Jason
authors.initials: J
authors.lastname: Coult
authors.affiliation: Department of Medicine University of Washington School of Medicine, Seattle, Washington.
authors.forename: Lauren
authors.initials: L
authors.lastname: Murphy
authors.affiliation: King County Emergency Medical Services Division, Seattle, Washington.
authors.forename: Carol
authors.initials: C
authors.lastname: Fahrenbruch
authors.affiliation: King County Emergency Medical Services Division, Seattle, Washington.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Blackwood
authors.affiliation: Department of Medicine University of Washington School of Medicine, Seattle, Washington; King County Emergency Medical Services Division, Seattle, Washington.
authors.forename: Peter
authors.initials: P
authors.lastname: Kudenchuk
authors.affiliation: Department of Bioengineering, Seattle, Washington.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Sherman
authors.affiliation: Department of Medicine University of Washington School of Medicine, Seattle, Washington; King County Emergency Medical Services Division, Seattle, Washington. Electronic address: rea123@u.washington.edu.
authors.forename: Thomas
authors.initials: T
authors.lastname: Rea
mesh_terms: D016887:Cardiopulmonary Resuscitation / Q000592:standards*; D004562:Electrocardiography; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D058687:Out-of-Hospital Cardiac Arrest; D011379:Prognosis; D012189:Retrospective Studies; D014693:Ventricular Fibrillation / Q000401:mortality / Q000503:physiopathology*
keywords: AMSA; CI; CPR; Cardiac arrest; Cardiopulmonary resuscitation; ECG; EMS; Electrocardiogram; OR; Resuscitation; Signal processing; Ventricular fibrillation; Waveform; amplitude spectrum area; cardiopulmonary resuscitation; confidence interval; electrocardiogram; emergency medical services; odds ratio