Local impedance tissue characterization to enhance accessory pathway ablation

Background

Accurate localization of accessory pathways (APs) is crucial for successful ablation in patients with symptomatic Wolff–Parkinson–White (WPW) syndrome. Conventional point-by-point mapping remains the standard approach but may be limited by spatial resolution and tissue heterogeneity. Radiofrequency (RF) ablation catheters equipped with local impedance (LI) sensing technology provide real-time information on catheter–tissue contact and local substrate properties, potentially improving lesion targeting and procedural efficiency.

Objective

To evaluate the capability of LI measurements to predict successful RF ablation sites in consecutive WPW cases using different catheter technologies.

Methods

This multicenter observational study included consecutive patients who underwent successful ablation of a single AP at 10 European centers. Patients were stratified according to the ablation catheter used: IntellaNav MiFi (INT) or StablePoint (STP), both incorporating the DirectSense algorithm for distal electrode LI measurement. Each ablation site was characterized by baseline LI and LI drop during RF delivery. The procedural endpoint was complete abolition of AP conduction.

Results

Sixty-three patients were included: 31 (49.2%) ablated with INT and 32 (50.8%) with STP catheters. A total of 499 RF lesions were delivered (median 6 [4–8] lesions per patient; INT 5 [3–10] vs STP 7 [5–10], p = 0.13). The most frequent AP location was left lateral (36.5%), followed by left posterolateral (14.3%) and right postero-septal (12.7%), together accounting for over 60% of cases.

Mean baseline LI at AP insertion sites was 124.1 ± 16 Ω with INT and 162.2 ± 19 Ω with STP catheters. In both groups, LI at the insertion site was significantly higher than in the blood pool (97.7 ± 8 Ω, p < 0.0001 for INT; 145.7 ± 18 Ω, p < 0.0001 for STP) but lower than in adjacent healthy tissue (130.2 ± 17 Ω, p < 0.0001 for INT; 175.3 ± 18 Ω, p < 0.0001 for STP).

A difference greater than 10% between LI at healthy tissue and LI at the AP insertion site was observed in 25 of 31 (80.6%) INT cases and 31 of 32 (96.9%) STP cases, suggesting strong discriminatory capacity of LI in distinguishing the AP insertion zone. Acute success (abolition of AP conduction) was confirmed in all cases (mean LI drop of 22 ± 6 Ω for INT and 24 ± 8 Ω for STP). No procedural complications occurred.

Conclusion

Local impedance measurements obtained with RF ablation catheters demonstrate distinct tissue signatures at AP insertion sites compared with both blood pool and healthy atrial tissue. These findings may support the use of LI-guided tissue characterization as a complementary tool for accurate identification and effective ablation of APs.