Impedance measurements
LI of the ablation catheter floating in the left atrial blood pool was 93 ± 11 ohm. Pre- and post-RFA LI values are shown in Figure 3. Pre-RFA LI was significantly lower at ablation points with than without a gap (106 ± 13 vs. 116 ± 17 ohm, p<0.0001; Figure 3A). Regional analyses revealed higher pre-RFA LI only at non-anterior regions. There was no difference in post-RFA LI between ablation points with and without a gap (94 ± 12 vs. 93 ± 12, p =0.61; Figure 3B). At ablation points with a gap, the LI drop during RFA was half that at points without a gap, irrespective of whether or not measurements were conducted at anterior walls (12 ± 7 vs. 23 ± 12 ohm, p<0.001; Figure 3C). A representative case is shown in Figure 1.
With regard to GI, the degree of impedance drop was significantly smaller using GI than LI at ablation points without a gap (14 ± 10 vs. 23 ± 11, p<0.0001). In contrast, there was no difference in impedance drop at ablation points with a gap (12 ± 7 vs. 12 ± 7, p =0.87). In addition, LI and GI were poorly correlated (correlation coefficient of pre-RFA measurements=0.40, p<0.0001; post-RFA=0.51, p<0.0001; impedance drop during RFA=0.12, p<0.01).