Atrial electrograms and the characterization of atrial fibrillation.

An improved method of calculating magnitude-squared coherence spectra on pairs of short-duration electrogram recordings is discussed. This method is based on adaptive signal processing techniques and yields spectra with higher resolution than those obtained using a straightforward direct method. The high-resolution spectra will make it possible to examine the time-varying relationship between activity at two sites during atrial fibrillation and may be useful for quick rhythm characterization by implanted devices or for constructing coherence maps in research studies. Example high-resolution spectra for sinus rhythm, atrial flutter, and atrial fibrillation are presented.