title: Physician interpretation and quantitative measures of electrocardiographic ventricular fibrillation waveform.
abstract: OBJECTIVE
  The characteristics of the ventricular fibrillation (VF) waveform may influence treatment decisions and the likelihood of therapeutic success. However, assessment of VF as being fine or coarse and the distinction between fine VF and asystole are largely subjective. The authors sought to determine the level of agreement among physicians for interpretation of varying VF waveforms, and to compare these subjective interpretations with quantitative measures.
  
  
  METHODS
  Six-second segments of waveform from LIFEPAK 300 units were collected. Fifty segments, including 45 VF and five ventricular tachycardia (VT) distracters, were graphed to simulate rhythm strips. These waveforms were quantitatively described using scaling exponent, root-mean-squared amplitude, and centroid frequency. Thirty-two emergency medicine residents were asked to interpret the arrhythmias as VT, "coarse" VF, "fine" VF, or asystole. Their responses were compared with the qantitative measures. Interphysician agreement was assessed with the kappa statistic.
  
  
  RESULTS
  One thousand four hundred forty interpretations were analyzed. There was fair agreement between physicians about the classification of arrhythmias (kappa = 0.39). Mean values associated with coarse VF, fine VF, and asystole differed in all three quantitative measure categories. The decision whether to defibrillate was highly correlated with the distinction between VF and asystole (Pearson chi-square = 1,170.40, df = 1, p[two-sided] < 0.001).
  
  
  CONCLUSIONS
  With only fair agreement on the threshold of fine VF and asystole, defibrillation decisions are largely subjective and caregiver-specific. These data suggest that quantitative measures of the VF waveform could augment the current standard of subjective classification of VF by emergency care providers.
authors.affiliation: Department of Emergency Medicine, University of Pittsburgh, Pennsylvania, USA.
authors.forename: C B
authors.initials: CB
authors.lastname: Lightfoot
authors.forename: T J
authors.initials: TJ
authors.lastname: Sorensen
authors.forename: M D
authors.initials: MD
authors.lastname: Garfinkel
authors.forename: L D
authors.initials: LD
authors.lastname: Sherman
authors.forename: C W
authors.initials: CW
authors.lastname: Callaway
authors.forename: J J
authors.initials: JJ
authors.lastname: Menegazzi
mesh_terms: D000704:Analysis of Variance; D004562:Electrocardiography; D004635:Emergency Medicine / Q000193:education*; D006323:Heart Arrest / Q000145:classification; D006801:Humans; D007396:Internship and Residency; D011446:Prospective Studies; D014693:Ventricular Fibrillation / Q000145:classification*