DCL and faster focal activations
Although DCL is measured for the purpose of identifying rotational activity, which is another potential AF driver in the CARTOFINDER system, we used this algorithm as an alternative to identify and obtain a feasible estimate of the dominant area of AF. Since DCL simply represents typical CL at the recording site, it is reasonable to assume that an area with a shorter DCL has a profound substrate in the maintenance of AF, while an area with a longer DCL shows a passive area on the persistence of AF. DCL does not account for fragmented potentials, since it is difficult to detect fragmented potentials in unipolar signals. Nonetheless, the atrial effective refractory period is much longer than complex intervals in fragmented electrograms.17 Therefore, local atrial activation intervals could be adequately assessed using the DCL calculation, despite the fact that it fails to account for the fragmented electrograms. The concept of the DCL may be similar to that of the dominant frequency. Sanders et al. demonstrated that the global average frequency in the LA in patients with persistent AF was 6.4 ± 0.6 Hz, corresponding to approximately 156 ms in CL,18which is in line with the present study (155.7 ± 22.1 ms). The CL on unipolar signals can be used instead of the activation frequency. By observing the spatial distribution of the DCL, we defined DFAs in order to identify important focal activations for the maintenance of AF. There was little difference in electrical features between the DFAs and non-DFAs; however, if all DFAs were eliminated, AF was likely to terminate to sinus rhythm, convert to AT, and prolong the AF CL. Our results suggest that DFAs play an important role in AF. Previous studies on ablation strategies targeting focal discharge have demonstrated excellent clinical performance;3,4,8 however, DFAs could be used as a more focused therapeutic target to enhance the efficacy of ablation. In addition, although further verification is required to use DCL as an analytical tool, the DCL analysis in our study may provide a more precise perspective on the recognition of AF propagation.