Toward discerning the mechanisms of atrial fibrillation from surface electrocardiogram and spectral analysis

Atrial fibrillation (AF) is the main cause of stroke and the most common sustained arrhythmia, afflicting about 2.3 million Americans. Clinical treatment and management of AF would benefit from a noninvasive and global assessment of the arrhythmia; however, that avenue seems currently limited in part by our poor understanding of arrhythmia itself. Experimental studies of AF in the isolated sheep heart demonstrated that high-frequency sources in the posterior wall of the left atrium drive the fibrillatory activity throughout both atria. Motivated by those results and by a growing body of work investigating how measurements of the cycle length of activity in patients during AF can contribute to its treatment, we focused our analysis on the dispersion of dominant frequency (DF) of the activity during AF in humans. Using electroanatomic mapping and Fourier methods, we generated 3-dimensional intracardiac DF maps of the atria in patients before AF ablation procedures and identified relatively small high-DF (HDF) sites. In patients with paroxysmal AF, the HDF sites are often localized to the posterior left atrium near the ostia of the pulmonary veins. In contrast, patients with permanent AF demonstrate HDF sites that are more often localized to the atria than the posterior left atrium-pulmonary vein junction. In our study, ablation at HDF sites resulted in significant slowing of the arrhythmia and termination of sustained AF in 87% of patients with paroxysmal AF. Furthermore, we found that abolishing, by ablation, preexisting left atrium to right atrium DF gradients predicted long-term freedom of AF in both paroxysmal and persistent AF patients. Overall, the analysis of intracardiac electrical recordings in the frequency domain has greatly enhanced our understanding of its underlying mechanisms and may contribute to monitoring drug effects and guide ablation procedures aiming at its termination. On the other hand, current body surface mapping methods have also suggested better correlations between surface AF frequency and intracardiac local DFs as compared with spatiotemporal activation patterns. Therefore, further study of the correlation of spectral observables obtained from the atria and from the surface electrocardiogram during AF seems to have the potential to advance our ability to diagnose and discern mechanisms of AF noninvasively.