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.