Aims The predictive role of local impedance (LI) drop in lesion formation using a
novel contact force sensing ablation catheter was recently described. The purpose
of our current study was to assess the temporal characteristics of LI drop during
ablation and its correlation with acute lesion efficacy. Methods and results Point-by-point
pulmonary vein isolation was performed. The efficacy of applications was determined
by pacing along the circular ablation line and assessing loss of capture. Local impedance,
contact force, and catheter position data with high resolution were analysed and compared
in successful and unsuccessful applications. Five hundred and fifty-nine successful
and 84 unsuccessful applications were analysed. The successful applications showed
higher baseline LI (P < 0.001) and larger LI drop during ablation (P < 0.001, for
all). In case of unsuccessful applications, after a moderate but significant drop
from baseline to the 2 s time point (153 vs. 145 Omega, P < 0.001), LI did not change
further (P = 0.99). Contradictorily, in case of successful applications, the LI significantly
decreased further (baseline-2 s-10 s: 161-150-141 Omega, P < 0.001 for all). The optimal
cut-point for the LI drop indicating unsuccessful application was <9 Omega at the
4-s time point [AUC = 0.73 (0.67-0.76), P < 0.001]. Failing to reach this cut-point
predicted unsuccessful applications [OR 3.82 (2.34-6.25); P < 0.001]. Conclusion A
rapid and enduring drop of the LI may predict effective lesion formation, while slightly
changing or unchanged LI is associated with unsuccessful applications. A moderate
LI drop during the first 4 s of radiofrequency application predicts ineffective radiofrequency
delivery.
