Characteristics of fibrillatory activities during spontaneous termination of paroxysmal atrial fibrillation: new insight from high-density right atrium frequency mapping.

Background: Sinus node (SN) activity is difficult to assess during atrial fibrillation (AF). The aim of the present study was to investigate SN activity by frequency analysis during AF.

Methods: Thirteen patients with paroxysmal AF and atrial flutter in the right atrium (RA) underwent 3-dimensional noncontact mapping. The fibrillatory activity was recorded from a multielectrode array in the RA. A frequency analysis with 2- and 6-second time-segment lengths was performed. Spectral characteristics (dominant frequency and harmonic index) and isopotential activation maps were used to investigate the spatiotemporal activity of the SN region and the rest of the RA (crista terminalis, septum, and free wall) during the initiation, while ongoing, and before the termination of AF.

Results: With duration of 6 seconds, the whole RA had similar trends of frequency distribution. With duration of 2 seconds prior to termination, the SN region exhibited a trend of low-frequency pattern and high-organization distribution, compared with the segments for the 2 to 4 and 4 to 6 seconds before termination. The isopotential activation maps showed the spontaneous earliest activities had wave front propagation patterns similar to those during sinus rhythm (after termination).

Conclusions: The fibrillatory activity of the SN region was organized, and slow activation was detected, by frequency analysis and isopotential mapping, within 2 seconds just prior to AF termination.