Fast Fourier transform analysis of ventricular fibrillation intervals to predict ventricular refractoriness and its spatial dispersion.

A technique of fast Fourier transform analysis has been used to derive mean ventricular fibrillation (VF) intervals, and to confirm that these VF intervals predict ventricular refractory periods. Twenty episodes of VF were induced by a rapid ventricular pacing in 12 sheep. VF activations in a 10-second period were simultaneously acquired from 64 epicardial sites with an electrode sock. The VF electrograms were analyzed by a fast Fourier transform analysis. The dominant peak frequency of the VF spectrum in each epicardial site was converted into milliseconds and served as a mean VF interval. The dominant peak frequency of VF electrograms ranged from 8.1 to 11.5 Hz, and the corresponding mean VF intervals were 87 to 124 ms. In five sheep, the mean VF intervals and the effective refractory periods were determined by the extrastimulus technique obtained from 29 epicardial sites. There was a very good correlation between the two parameters when the effective refractory periods were determined at a basic cycle length of 300 ms (r = 0.89, P < 0.001) and 400 ms (r = 0.87, P < 0.001), respectively. VF was induced twice in eight sheep. The maximum difference in the mean VF intervals between the two VF episodes in the same sheep was 3 ms (P > 0.05). In conclusion, mean VF intervals determined by the fast Fourier transform analysis have a good reproducibility and a good correlation with ventricular refractory periods measured by the classic extrastimulus technique. The mean VF intervals could serve as an index of ventricular refractoriness.