4.7 Study limitations
Our study had several limitations. First, the sample size was relatively
small. Second, some patients underwent a prior ablation. In such cases,
we could not completely discriminate between the ablation lesions and
pre-existing atrial fibrosis around the PVs. Furthermore, the LGE sites
might have been overestimated on the posterior wall adjacent to the
vertebrae and anterior wall adjacent to the aortic cusp due to wall
compression by those organs. Moreover, it might have been difficult to
measure the thickness of the posterior LA wall with consistency in all
patients. Thirdly, the new phase-mapping system adopted in this study
may have had unknown limitations because it is widely used in Japan but
not in other countries. We expect that this system will be widely used
worldwide in the future. Fourth,
mapping was not performed in the right atrium (RA) because of the
stability of the mapping catheter and the reproducibility of the LGE-MRI
assessment in the RA. Finally, no histological validation was performed
in the LGE areas. LGE-MRI has a potential risk of over- and under-
estimating fibrosis.