Physiologic measurement of the ventricular fibrillation ECG signal: estimating the duration of ventricular fibrillation.

Estimating the duration of ventricular fibrillation may help determine the best initial therapy and provide estimates of the most appropriate dose of epinephrine to administer during cardiac arrest and resuscitation. In addition, estimating this time can provide a more sound methodologic approach to stratifying patients in the analysis of cardiac arrest studies. In an initial series of studies in swine, we attempted to determine whether changes in the frequency or amplitude (power) of the ventricular fibrillation ECG signal during cardiac arrest could be used to estimate this time. These studies characterized the dynamics of both the total power and the frequency distribution of the power in the ECG over time during ventricular fibrillation in swine. Our purpose was to determine whether sufficient information existed in either parameter to estimate the duration of ventricular fibrillation. The median frequency of the power spectrum was used to track power distribution. Both parameters followed a dynamic and repeatable pattern. A mathematical model of median frequency was developed and used with data obtained from additional swine to estimate the duration of ventricular fibrillation. The model estimated the duration of ventricular fibrillation to within +/- 1.3 minutes of the actual duration from one to ten minutes after the onset of ventricular fibrillation. We recently characterized the time course of the median frequency during ventricular fibrillation in human beings. The median frequency was extracted from each four-second segment of the ventricular fibrillation ECG recordings and plotted versus time from the onset of cardiac arrest. The median frequency in human beings followed a repeatable time course during ventricular fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)