Signal analysis of the human electrocardiogram during ventricular fibrillation: Frequency and amplitude parameters as predictors of successful countershock

Study objective: To determine whether there is information in the human ventricular fibrillation (VF) ECG signal that is predictive of successful countershock. Methods: We carried out a retrospective analysis of ECG signals recorded during out-of-hospital treatment of adult patients in VF Four parameters - centroid frequency (FC), peak power frequency (FP), average segment amplitude (SA), and average wave amplitude (WA) - were extracted from the recorded ECG signal immediately before each countershock and compared with countershock outcome. Results: The outcome of each countershock (total, 128 countershocks) administered to 55 patients in VF was determined from available emergency medical services data sheets and time-domain ECG signal and voice recordings. The original 4-second time-domain ECG segment immediately before the countershock was used to extract SA and WA. The 4-second ECG segment immediately before each countershock was transformed into the frequency domain by means of Fourier analysis, and the parameters FC and FP were extracted from the result. These parameters were compared with countershock outcome by means of Kolmogorov-Smirnov analysis. Sensitivity and specificity of these parameters, as well as receiver operating characteristic curves, were constructed. FC was statistically higher for successful countershocks (FC, 5.48+/-.67 Hz) than for unsuccessful countershocks (FC, 4.85+/-1.16 Hz; P=.012). We found no statistical difference for FP (P=.066), SA (P=.549), and WA (P=.337). FP and FC, when used in combination and in certain ranges (3.5 Hz less than or equal to FP less than or equal to 7.75 Hz and 3.86 Hz less than or equal to FC less than or equal to 6.12 Hz) had a sensitivity of 100% and a specificity of 47.1% in predicting successful countershock. The probabilities of predicting countershock outcome for FC, FP, SA, and WA were .72, .70, .52, and .53, respectively. Conclusion: FC and FP are predictive of countershock outcome for patients in VF and hold the potential to guide therapy during cardiac arrest.