• C G Brown, R F Griffith, P Van Ligten, J Hoekstra, G Nejman, L Mitchell, and R Dzwonczyk.
• Department of Emergency Medicine, Ohio State University, Columbus 43210.
• Ann Emerg Med. 1991 Jul 1; 20 (7): 787-9.

Study HypothesisCurrent American Heart Association guidelines recommend immediate defibrillation of ventricular fibrillation. When this is unsuccessful, there are no guidelines to help determine the optimum time at which to defibrillate after the administration of an alpha-adrenergic agonist. Previous studies have shown that the median frequency of the ventricular fibrillation ECG signal correlates with myocardial perfusion during CPR. We hypothesized that median frequency could predict the success of defibrillation and thus accurately determine the most appropriate time at which to defibrillate during ventricular fibrillation.Study PopulationTwenty-two mixed-breed swine weighing more than 15 kg were studied.MethodsVentricular fibrillation was induced electrically, and the ventricular fibrillation ECG signal was analyzed using fast Fourier analysis. After ten minutes of ventricular fibrillation, mechanical CPR was begun. After three minutes of CPR, the animals received one of three alpha-adrenergic agonists and CPR was continued. Defibrillation was attempted three and one-half minutes after drug administration. The average median frequency 20 seconds before defibrillation was calculated. Sensitivity and specificity of median frequency with respect to defibrillation success were determined.ResultsA median frequency of 9.14 Hz had a sensitivity of 100% and a specificity of 92.31% in predicting the results of defibrillation in this model.ConclusionThe median frequency may serve as a valuable parameter to guide defibrillation therapy during ventricular fibrillation.

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