Bispectral energies within electrocardiograms during ventricular fibrillation are correlated with defibrillation shock outcome

We investigated whether the degree of phase coupling among orthogonal elect rocardiograms during ventricular fibrillation (VF) was correlated with defi brillation shock outcome. We used cross bispectrum to estimate the degree o f phase coupling. In dogs, VF was electrically induced and terminated with a defibrillation shock with a 50% probability of success. The defibrillatio n shock was delivered between the right ventricular apex and a subcutaneous patch electrode. Bispectra were integrated within 8.7-11.7, 8.7-11.7 Hz ba ndwidths and compared between those trials for which the defibrillation sho cks were successful (206 trials, 49%) and unsuccessful (221 trials, 51%) in terminating VF. Results showed that between 200 and 1000 ms before defibri llation shock, unsuccessful trials had greater bispectral energy than succe ssful trials (p < 0.05). Although correlations between degree of phase coup ling and shock outcome do not indicate causal relationship or predictabilit y, they provide further evidence of the organization during fibrillation. W e discuss the nonstationary wavelet hypothesis, previously proposed in the literature by other investigators, as one of the possible mechanisms to exp lain the correlation between bispectral energy and shock outcome. (C) 1999 Biomedical Engineering Society. [S0090-6964(99)00502-0].