Scaling exponent predicts defibrillation success for out-of-hospital ventricular fibrillation cardiac arrest

  • Callaway C
  • Sherman L
  • Mosesso V
 et al. 
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BACKGROUND:-Defibrillator shocks often fail to terminate ventricular fibrillation (VF) in out-of-hospital cardiac arrest (OOHCA), and repeated failed shocks can worsen the subsequent response to therapy. Because the VF waveform changes with increasing duration of VF, it is possible that ECG analyses could estimate the preshock likelihood of defibrillation success. This study examined whether an amplitude-independent measure of preshock VF waveform morphology predicts outcome after defibrillation. Methods and Results-Clinical data and ECG recordings from an automated external defibrillator were obtained for 75 subjects with OOHCA in a suburban community with police first responders and a paramedic-based emergency medical system. An estimate of the fractal self-similarity dimension, the scaling exponent, was calculated off-line for the VF waveform preceding shocks. Success of the first shock was determined from the recordings. Return of pulses and survival were determined by chart review. The first shock resulted in an organized rhythm in 43% of cases, and 17% of cases survived to hospital discharge. A lower mean value of the scaling exponent was observed for cases in which the first defibrillation resulted in an organized rhythm (P:=0.004), for cases with return of pulses (P:=0.049), and for cases surviving to hospital discharge (P:

Author-supplied keywords

  • Defibrillation
  • Electrocardiography
  • Fibrillation
  • Heart arrest
  • Survival

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  • Clifton W. Callaway

  • Lawrence D. Sherman

  • Vincent N. Mosesso

  • Thomas J. Dietrich

  • Eric Holt

  • M. Christopher Clarkson

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