Frequency analysis of ventricular fibrillation in three surface ECG leads

Surface electrocardiogram (ECG) signals on approximately orthogonal leads were recorded during six episodes of ventricular fibrillation (VF) provoked during electrophysiology studies. The aim was to examine the utility of frequency analysis for investigating recordings of VF made on three ECG leads. Successive 2.048-s data epochs were transformed into the frequency domain using a fast Fourier transform (FFT) algorithm. A similar and characteristic amplitude spectrum was observed on all ECG leads in all VF recordings. Coordination of separate ECG leads was assessed by determining the relative phases of frequency components at 4.39, 5.37, and 6.34 Hz. During four VF recordings these phase differences were variable but showed some periods of stability. During two VF recordings the phase differences at 5.37 Hz remained almost constant throughout the event. This study suggests that a degree of myocardial electrical organization exists during VF and is reflected in the surface ECG