br Results The baseline characteristics of the study patient

Results The baseline characteristics of the study patients are shown in Table 1. The tachycardia DBU length was 350±95ms. To make the tachycardia sustained and stable, isoproterenol was infused in four patients. The activation map during AT was created by sampling from 152±28 RA points, and it revealed a focal activation pattern with the EAS close to the HB recording site in all patients (Fig. 1A). The EAS during AT was 11±7mm above (n=3), below (n=1), posterior (n=1), or right (n=1) to the HB recording site. Four of the six patients had the EAS within 10mm from the HB site.
Discussion
Conclusions
Funding sources
Conflict of interest Drs. Ken Okumura and Masaomi Kimura received speaker honoraria from Johnson & Johnson K.K. Shingo Sasaki and Daisuke Horiuchi received research grant support from Johnson & Johnson K.K. and Medtronic Japan Co., Ltd. The rest of the authors have no relevant disclosures.
Acknowledgments
Background The existence of localized rotors and focal impulses has been reported in human atrial fibrillation (AF) [1]. Phase mapping has been used to characterize the spatiotemporal variability of electrical activities, thereby providing insight into the mechanisms of AF [1,2]. Although the existence of a rotor, along with fibrillatory conduction, has been reported to contribute to maintenance of AF [3], the prevalence and specific role of stable rotors and/or focal impulses in human AF remain unclear. Therefore, we investigated whether rotors and focal impulses can be identified in human AF by analyzing intracardiac electrograms recorded from a multi-electrode catheter.
Methods
Results Patient mean age was 54±12 years, and all were men. The median AF duration was 60 (17–109) months, and mean transthoracic echocardiography-derived LA diameter was 38±5mm. The BCs were 38mm (4 patients), 48mm (9 patients), or 60mm (7 patients) in diameter. High-quality left atrial intracardiac electrogram recordings were obtained for 8 patients (40%). Intracardiac electrogram signals for the remaining 12 patients were of reduced quality due to insufficient contact between some of the BC electrodes and the LA wall, and thus did not furnish global maps. One or more localized rotors were detected in 3 (37.5%) of the 8 patients (Fig. 3A). Localized rotors lasted 1.9–6.8s. Regions in the rotor path were characterized by a distinct DF, whereas the region at the center of the rotor exhibited a fragmented, irregular, low-amplitude wavefront, resulting in no distinct DF (Fig. 3B). Of the remaining 5 patients, 4 were shown to have focal impulses (Fig. 3C), and 1 exhibited neither a rotor nor focal impulse. The regions at the focus exhibited a sharp DF.
Discussion The existence of rotor(s) during AF has been demonstrated in an isolated sheep heart [3], and subsequently demonstrated in human AF via BC recordings, epicardial mapping, and body surface mapping [6,10,11]. These procedures aimed to identify atrial sites that exhibited multiphasic and rapid activation, and ablation at those sites effectively terminated the AF [10,11]. However, the number of rotors and results of rotor ablation remain poorly defined [12]. Stable LA activation was recorded from the BC in 8 of the 20 study patients, and in 3 of these 8 patients, rotors localized to the LA were observed. Although limited, the present results suggest that BC-based phase mapping can be used to visualize the LA wavefront dynamics underlying AF. We found that the power spectra along the rotor path typically exhibited a single peak frequency, but the region at the center of the rotor did not show a single, clear DF. This finding is consistent with a previous report that the widespread frequency power distribution during the meandering of a rotor reflects the power spectra of signals outside its immediate vicinity, and thus explains the irregular and fragmented local electrograms [13]. Identification of the rotating wavefronts or focal impulses from multi-electrode catheter recordings is difficult because of low signal quality and/or low spatial sampling density. In 12 of the 20 patients, a number of BC electrodes did not adequately contact the LA wall, and thus the BC coverage posed a major methodological limitation in the assessment of global LA activation, as also reported previously [12].