Background: A novel measurement of the local impedance (LI) and electrograms recorded from micro-electrodes on catheter tip has been developed. However, the data during pulmonary vein (PV) ablation is not sufficient. We aimed to investigate the utility of this measurement during initial atrial fibrillation (AF) ablation. Methods: We investigated 111 representative radiofrequency applications in 7 AF patients without a history of prior ablation (6 males, age 68 [65-72] years, 2 persistent AF). The ablation strategy was PV isolation for paroxysmal AF and single ring box isolation for persistent AF, using MiFi catheter. The correlation of the generator impedance (GI) drop and LI drop after radiofrequency applications and the predictive value of the initial LI elevation before radiofrequency applications for LI drop were analyzed. Also, the LI and GI drop were investigated according to the location of RF applications. Results: The LI drop was higher than GI drop (23.7 [16.4-35.7] and 9.0 [6.0-12.0]; P <.01). There were correlations between the initial LI elevation and LI drop (R2 = 0.466, P <.01) and between the LI and GI drop (R2 = 0.263, P <.01). The LI drops significantly differed according to the different anatomical localizations by the Kruskal–Wallis test, although the GI drops did not differ (P <.01 and P =.49, respectively). Conclusion: LI drop was associated with initial LI elevation and was larger than GI drop. LI drop was different according to locations, although GI drop was not. These findings might indicate that LI drop would be a more sensitive marker for lesion formation than GI drop.
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