Comparison of techniques for time-frequency analysis of the ECG during human ventricular fibrillation

Ventricular fibrillation (VF) is a catastrophic and potentially lethal breakdown of heart rhythm. Despite its importance, it remains poorly understood; there are no effective techniques for predicting or preventing VF, and it can only be reliably terminated by a large current pulse: defibrillation. There is currently great interest in using linear and nonlinear signal processing techniques to characterise recordings of VF. Five episodes of VF were recorded from patients in a Coronary Care Unit. Time-frequency distributions (TFDs) of the first 10s of these recordings were estimated with the short-time Fourier transform, Wigner-Ville, smoothed Wigner-Ville and Choi-Williams algorithms. The smoothed Wigner distribution was found to give a TFD reasonably free of cross-terms, without the additional computational cost of the Choi-Williams algorithm. Used in tandem with the predictable short-time Fourier transform, the smoothed Wigner TFD is a valuable tool for characterising the TFD of human VF.