High-frequency periodic sources underlie ventricular fibrillation in the isolated rabbit heart

The mechanism(s) underlying ventricular fibrillation (VF) remain unclear. W e hypothesized that at least some forms of VF are not random and that high- frequency periodic sources of activity manifest themselves as spatiotempora l periodicities, which drive VF. Twenty-four VF episodes from 8 Langendorff -perfused rabbit hearts were studied using high-resolution video imaging in conjunction with ECG recordings and spectral analysis. Sequential wavefron ts that activated the ventricles in a spatially and temporally periodic fas hion were identified. In addition, we analyzed the lifespan and dynamics of wavelets in VF, using a new method of phase mapping that enables identific ation of phase singularity points (PSs), which flank individual wavelets. S patiotemporal periodicity was found in 21 of 24 episodes. Complete reentry on the epicardial surface was observed in 3 of 24 episodes. The cycle lengt h of discrete regions of spatiotemporal periodicity correlated highly with the dominant frequency of the optical pseudo-ECG (R-2=0.75) and with the gl obal bipolar electrogram (R-2=0.79). The lifespan of PSs was short (14.7+/- 14.4 ms); 98% of PSs existed for <1 rotation. The mean number of waves ente ring (6.50+/-0.69) exceeded the mean number of waves that exited our mappin g field (4.25+/-0.56; P<0.05), These results strongly suggest that ongoing stable sources are responsible for the majority of the frequency content of VF and therefore play a role in its maintenance. In this model, multiple w avelets resulting from wavebreaks do not appear to be responsible for the s ustenance of this arrhythmia, but are rather the consequence of breakup of high-frequency activation from a dominant reentrant source.