Fibrillation power, an alternative method of ECG spectral analysis for prediction of countershock success in a porcine model of ventricular fibrillation

Background: Noninvasive prediction of defibrillation success after cardiac arrest and cardiopulmonary resuscitation (CPR) may help in determining the optimal time for a countershock, and thus increase the chance for survival. Methods: In a porcine model (n = 25) of prolonged cardiac arrest, advanced cardiac life support was provided by administration of two or three doses of either vasopressin or epinephrine after 3 or 8 min of basic life support . After 4 min of ventricular fibrillation and 18 min of life support., defi brillation was attempted. The denoised power spectral density of 10 s inter vals of the ventricular fibrillation electrocardiogram (ECG) was estimated from averaged and smoothed Fourier transforms. We have eliminated the spect ral contribution of artifacts from manual chest compressions and provide a definition for the contribution of ventricular fibrillation to the power sp ectral density. This contribution is quantified and termed "fibrillation po wer". Results: We tested fibrillation power and two established methods in their discrimination of survivors (n = 16) vs. non-survivors (n = 9) in the last minute before the countershock. A fibrillation power greater than or equal to 79 dB predicted successful defibrillation with sensitivity, specif icity, positive predictive value and negative predictive value of 98%, 98%, 99% and 97% while a mean fibrillation frequency greater than or equal to 7 .7 Hz was predictive with 85%, 83%, 90% and 77% and a mean amplitude greate r than or equal to 0.49 mV was predictive with 95%, 90%, 94% and 91%. Concl usions: We suggest that fibrillation power is an alternative source of info rmation on the status of a fibrillating heart and that it may match the est ablished mean frequency and amplitude analysis of ECG in predicting success ful countershock during CPR. (C) 2001 Elsevier Science Ireland Ltd. All rig hts reserved.