Background— Recent studies have demonstrated spatiotemporal organization in atrial fibrillation (AF), with a left-to-right atrial frequency gradient during AF in isolated sheep hearts. We hypothesized that human AF would also manifest a left-to-right atrial frequency gradient.

Methods and Results— Thirty-one patients aged 56.7±10.5 years with a history of paroxysmal or persistent (>1 month) AF were included. Recordings were made at each pulmonary vein (PV) ostium and simultaneously from the coronary sinus (CS) and posterior right atrium (RA) during AF. Sequential fast Fourier transforms (FFTs) were performed. FFT profiles were analyzed to determine the dominant frequency (DF). There were 18 patients with paroxysmal AF and 13 with persistent AF. In the paroxysmal group, there was a significant left-to-right atrial DF gradient, with DF highest at the PV/left atrial (LA) junction, intermediate at the CS, and lowest in the RA (6.2±0.8, 5.5±0.7, and 5.1±0.6 Hz, respectively; P<0.001). There were no patients in whom DF was greater at the RA than the PV/LA junction. In the persistent group, there was no significant difference between DF recorded from the LA/PV junction, CS, and RA (6.1±0.7, 5.8±0.6, and 5.8±0.6 Hz, respectively; P=NS).

Conclusions— In humans with paroxysmal AF, DFs are highest at the PV/LA junction, intermediate in the CS, and slowest in the posterior RA. These findings agree with animal models that suggest that the posterior LA may play an important role in maintaining paroxysmal AF. The role of the posterior LA in persistent AF requires further study.