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 huma n ventricular fibrillation (VF) ECG signal that is predictive of succe ssful countershock. Methods: We carried out a retrospective analysis o f ECG signals recorded during out-of-hospital treatment of adult patie nts in VF Four parameters - centroid frequency (FC), peak power freque ncy (FP), average segment amplitude (SA), and average wave amplitude ( WA) - were extracted from the recorded ECG signal immediately before e ach countershock and compared with countershock outcome. Results: The outcome of each countershock (total, 128 countershocks) administered t o 55 patients in VF was determined from available emergency medical se rvices data sheets and time-domain ECG signal and voice recordings. Th e original 4-second time-domain ECG segment immediately before the cou ntershock was used to extract SA and WA. The 4-second ECG segment imme diately before each countershock was transformed into the frequency do main by means of Fourier analysis, and the parameters FC and FP were e xtracted from the result. These parameters were compared with counters hock outcome by means of Kolmogorov-Smirnov analysis. Sensitivity and specificity of these parameters, as well as receiver operating charact eristic curves, were constructed. FC was statistically higher for succ essful countershocks (FC, 5.48+/-.67 Hz) than for unsuccessful counter shocks (FC, 4.85+/-1.16 Hz; P=.012). We found no statistical differenc e 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 les s than or equal to 6.12 Hz) had a sensitivity of 100% and a specificit y 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 c ountershock outcome for patients in VF and hold the potential to guide therapy during cardiac arrest.