Characterization of atrial fibrillation using the surface EGG: Time-dependent spectral properties

Time frequency analysis is considered for characterizing atrial fibrillatio n in the surface electrocardiogram (ECG). Variations in fundamental frequen cy of the fibrillatory waves are tracked by using different time-frequency distributions which are appropriate to short- and long-term variations, The cross Wigner-Ville distribution is found to be particularly useful for sho rt-term analysis due to its ability to handle poor signal-to-noise ratios. In patients with chronic atrial fibrillation, substantial short-term variat ions exist in fibrillation frequency and variations up to 2.5 Hz can be obs erved within a few seconds, Although time-frequency analysis is performed i ndependently in each lead, short-term variations in fibrillation frequency often exhibit a similar pattern in the leads V-1, V-2 and V-3. Using differ ent techniques for short- and long-term analysis, it is possible to reliabl y detect subtle long-term changes in fibrillation frequency, e.g., related to an intervention, which otherwise would have been obscured by spontaneous variations in fibrillation frequency.