Clinical implications of impedance-guided procedure
As our strategy was not dependent on the AI value, exact AImin value for durable lesion creation was not determined. Although several data highlighted the significance of impedance drop in durable lesion creation,[18, 20] certain limitations need to be considered such as insufficiency without stable catheter contact[21] and influence by contact angle.[22] To avoid esophageal injury, we could not apply HP application for up to 5 seconds; as such, impedance drop was not a preferable parameter to predict acute PVRs in the SAE. Nevertheless, a strong association was identified between ILDmax and acute PVR in the SAE, and ILDmax of 4.8 mm had a strong association with durability with a specificity of 90%, suggesting that current protocol could be improved with tightened lesion creation. As Imp-min of 6.5 ohm was strongly associated with an acute durability with a specificity of 90% in the segments other than SAE, impedance-guided HPSD-PVI with a target value of above 6.5 ohm would be suitable in the future. Occasionally, unipolar signal could not be visible due to electrical artifacts even with an indifferent electrode; and unipolar signal could not be reflected by VisiTag on its nature. As impedance drop could be monitored on-site, and dynamic change visualized by VisiTag color, it could be used during PVI in persistent AF patients. While efficacy of impedance-guided HPSD-PVI requires further evaluation, providing sufficient catheter contacts and avoiding perpendicular contact, this technique might prove applicable.