The impact of electrical connections between left ipsilateral pulmonary veins on the time-to-isolation values in cryoballoon ablation.

Background: The time-to-isolation (TTI) may be a physiological predictor of durable isolations, and TTI-guided dosing strategies are widely performed in cryoballoon ablation. We sought to investigate the impact of the order of targeting the pulmonary veins (PVs) on the TTI values of left ipsilateral PVs.
Methods: This study included 144 atrial fibrillation patients who underwent PV isolations using 28-mm fourth-generation cryoballoons. In 101 patients, the left superior PV (LSPV) was targeted and followed by the left inferior PV (LIPV) (group 1), and the LIPV was targeted and followed by the LSPV in the remaining 43 (group 2).
Results: The total LSPV and LIPV freeze durations were 193 ± 60 and 171 ± 40 s, respectively. Real-time PV isolation monitoring was capable in 137 (95.1%) LSPVs and 119 (82.6%) LIPVs and in 112 (77.8%) patients (78 in group 1 and 34 in group 2) in both LSPVs and LIPVs. Among them, the LSPV TTI was significantly longer in group 1 than that in group 2 (54.8 ± 32.1 vs. 34.1 ± 17.3 s, p < 0.0001), while the LIPV TTI was significantly shorter in group 1 than that in group 2 (23.7 ± 11.8 vs. 39.2 ± 19.4 s, p < 0.0001). The ΔTTI ((TTI in LSPV)-(TTI in LIPV)) was significantly greater in group 1 than that in group 2 (31.1 ± 31.4 vs. - 5.0 ± 25.9 s, p < 0.0001). In 5 patients (3 in group 1 and 2 in group 2), initially targeted left PVs were not isolated despite complete vein occlusions, while they were by subsequent applications at the other ipsilateral PVs.
Conclusions: In CB ablation, the order of targeting PVs highly influenced the TTI of the left PVs owing to the presence of electrical connections between left ipsilateral PVs.
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