Electrocardiographic evaluation of defibrillation shocks delivered to out-of-hospital sudden cardiac arrest patients

Resuscitation. 1999 Jul;41(2):133-44. doi: 10.1016/s0300-9572(99)00040-4.


Objective: Following out-of-hospital defibrillation attempts, electrocardiographic instability challenges accurate assessment of defibrillation efficacy and post-shock rhythm. Presently, there is no precise definition of defibrillation efficacy in the out-of-hospital setting that is consistently used. The objective of this study was to characterize out-of-hospital cardiac arrest rhythms following low-energy biphasic and high-energy monophasic shocks in order to precisely define defibrillation efficacy and establish uniform criteria for the evaluation of shock performance.

Methods: Automatic external defibrillators (AEDs) delivering 150 J impedance-compensating biphasic or 200-360 J monophasic damped sine waveform shocks were observed in a combined police and paramedic program. ECGs from 29 biphasic patients and 87 monophasic patients were classified as organized, asystole or VF at post-shock times of 3, 5, 10, 20 and 60 s.

Results: Post-shock time (P<0.0001) and shock waveform type (P = 0.02) affected the classification of post-shock rhythm. At each analysis time, there were more patients in VF following high-energy monophasic shocks than following 150 J biphasic shocks (P<0.0001). The percentage of patients in VF increased with post-shock time. The rate of VF recurrence was not a function of shock type, indicating that refibrillation is largely a function of the patient's underlying cardiac disease.

Conclusion: Defibrillation should uniformly be defined as termination of VF for a minimum of 5-s after shock delivery. Rhythms should be reported at 5-s after shock delivery to assess early effects of the defibrillation shock and at 60-s after shock delivery to assess the interaction of the defibrillation therapy and factors such as post-shock myocardial dysfunction and the patient's underlying cardiac disease.

Publication types

  • Comparative Study

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Analysis of Variance
  • Cardiopulmonary Resuscitation / methods*
  • Chi-Square Distribution
  • Child
  • Confidence Intervals
  • Electric Countershock / methods*
  • Electrocardiography*
  • Emergency Medical Services*
  • Evaluation Studies as Topic
  • Female
  • Heart Arrest / complications
  • Heart Arrest / diagnosis
  • Heart Arrest / therapy*
  • Humans
  • Male
  • Middle Aged
  • Retrospective Studies
  • Sensitivity and Specificity
  • Time Factors
  • Ventricular Fibrillation / complications
  • Ventricular Fibrillation / diagnosis*