Time-frequency analysis of ventricular arrhythmias

Ventricular fibrillation (VF) is a potentially lethal disorder of heart rhythm. One persistent feature seen during VF is a prominent peak in the ECG spectrum between 3 and 7 Hz. The frequency of this peak generally increases during the first few seconds, and may also change abruptly during the arrhythmia. The presence of such a peak in the ECG spectrum indicates that the underlying electrical activity in the heart is periodic, the dynamics of this periodic activity may well be important in understanding the electrical mechanisms of VF. An example of the changes in spectra obtained using conventional techniques is shown in a figure. However, conventional frequency analysis techniques are inappropriate for use with nonstationary signals. The aim of this project was therefore to assess the suitability of the time-frequency distribution for identifying dynamic changes in periodic activity during VF.