Efficient frequency domain characterization of myocardial activation dynamics during ventricular fibrillation

A technique for quantitatively describing spatiotemporal myocardial activation dynamics in the frequency domain was developed and compared to results from the time domain. Peak frequencies (PFreq) from the FFT power spectrum were extracted from unipolar electrograms collected from 504 epicardial recording sites (1 mm separation) during multiple runs of electrically-induced ventricular fibrillation (VF) in open-chest pigs. To confirm that PFreq provides a reasonable metric of mean activation interval (MAI) during VF, we constructed spatial plots of PFreq over the mapped region and compared PFreq to the MAI at nine points equally-spaced over the mapped region during 2 s segments (n=20) of mapping data taken 1, 5, and 10 s after VF induction. To obtain data over a range of physiologically-relevant MAIs, a potent class III drug was used to decrease PFreq during VF. Regression analyses for all data revealed a statistically significant positive correlation between PFreq and MAI (R²=0.828, p<0.001). Description of temporally-averaged myocardial activation dynamics in the frequency domain provides a useful and computationally-efficient means to define the spatial distribution of MAI in fibrillating ventricular myocardium.