Clinical implication and future perspectives
The main clinical implication of this study is the recommendation of a target LI drop of 15 ohm at each RFA with a 4-mm distance between adjacent ablation points for impedance-guided PV isolation. Factors associated with an LI drop of <15 ohm in this operator-blinded study were short RFA time, low pre-RFA LI, and unexpected RFA suspension due to a rise in esophageal temperature and catheter dislodgement. These data suggest that insufficient catheter stability, catheter contact with tissue and RFA time contribute to an insufficient LI drop. Robust catheter-tissue contact using a contact-force-sensing catheter and prolongation of RFA time until achievement of an LI drop of ≥15 ohm may overcome the issue of insufficient ablation lesion formation. Multifaceted evaluation such as that using pre-existing lesion formation indexes based on contact force is expected to contribute to the creation of optimal lesions by radiofrequency ablation. 15, 16
In addition, to extend the potential benefits of impedance monitoring to improving the safety of the ablation procedure, future studies should clarify the LI predictor of steam pop. Furthermore, identification of target LI drop values for optimal lesion formation is needed for a variety of arrhythmias.