Early rapid local impedance drop is associated with acute lesion efficacy during pulmonary vein isolation.

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 Ω, 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 Ω, P < 0.001 for all). The optimal cut-point for the LI drop indicating unsuccessful application was <9 Ω 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.