Limitations
Several limitations of this study warrant mention. First, while
operators attempted to maintain a 4-mm distance between ablation points,
the actual distances were variable. Unevenness in the distribution of
ablation points may influence conductivity along the linear ablation
line irrespective of ablation lesion formation at each point. Second,
although LI measurement is significantly influenced by catheter
orientation in relation to the myocardial surface, this study did not
consider this issue. Third, myocardial thickness should be considered
when creating a transmural ablation lesion. Target LI drop values may
differ among regions with different myocardial thickness. Although
regional analyses were performed to attempt to overcome this issue, the
small sample size made it difficult to interpret the results. Fourth, we
used the absence of a conduction gap as a surrogate for sufficient
lesion formation. However, because electrical connection between the
left atrium and PV is derived from prolonged myocardial sleeves
extending into PVs, contiguous lesion formation is not necessarily
required to achieve PV isolation.17 As a consequence,
ablation points without a gap do not always have transmural lesion
formation. Finally, the results of statistical analyses may have been
influenced by the relatively small size of the study population.