Time-frequency coherence analysis of atrial fibrillation termination during procainamide administration

A time-frequency coherence estimator is developed and applied to study changes in signal characteristics as atrial fibrillation converts to sinus rhythm during administration of procainamide. A coherence spectrogram (CS) using multiple sinusoidal tapers is used in this study to assess phase relations between electrogram recordings at multiple atrial sites of seven patients who received procainamide to terminate atrial fibrillation. CSs are calculated (0 to 60 Hz) with 1 sec time resolution and 6.2 Hz frequency resolution. In agreement with previous studies, CSs generally exhibit low coherence during atrial fibrillation. Conversion to sinus rhythm is concomitant with an increase in coherence and emergence of structured time-frequency topography. Transition from atrial fibrillation to sinus rhythm is associated with a variety of time-frequency dynamics. Both gradual and abrupt increases in coherence coincide with conversion. Results suggest transient electrical organization in the atria during atrial fibrillation not seen in previous low-resolution coherence studies. CSs permit investigation of rhythm organization with unparalleled time and frequency resolution and thus are useful for studying transient changes in cardiac rhythms that may reflect underlying mechanisms.