Spatially distributed dominant excitation frequencies reveal hidden organization in atrial fibrillation in the Langendorff-perfused sheep heart

Introduction: Atrial fibrillation (AF) is characterized by complex wave pro pagation, yet periodic excitation suggesting a high degree of organization may be revealed during sustained AF. We provide a systematic quantification of the spatial distribution of dominant frequencies (DFs) of local excitat ion on the epicardium of the right atrial (RA) free wall and left atrial (L A) appendage of the isolated sheep heart during AF. The data reveal, for th e first time, hidden organization, independent of the activation sequences or nature of electrograms. Methods and Results: In 13 Langendorff-perfused sheep hearts, AF was induce d in presence of 0.1 to 0.6 mu M acetylcholine. Video movies (potentiometri c dye di-4-ANEPPS) of the RA and LA (>30,000 and >20,000 pixels, respective ly) were obtained at 120 frames/sec and a biatrial electrogram was recorded . Spectral analyses were performed on movies with DF maps constructed. Duri ng AF, the activity formed stable discrete domains with uniform DFs within each domain. Acceleration of AF increased the number of domains (R = 0.81, P < 0.0001) and the DF variance (R = 0.63, P < 0.001), indicating a decreas e in organization. Also, the LA was faster and more homogenous, with smalle r number of DF domains, compared to the RA (P < 0.00001). Conclusion: In this model, AF is characterized by multiple domains with dis tinct DFs on the atrial epicardium. The decrease in domain area with increa sed rate suggests that AF results from high-frequency impulses that undergo spectral transformations. The LA is generally faster and more organized th an the RA, suggesting that the sources for the impulses are localized to th e LA.