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.