PO-02-095 UTILITY OF LOCAL IMPEDANCE MONITORING TO GUIDE HIGH-POWER SHORT-DURATION RADIOFREQUENCY ABLATION FOR ATRIAL FIBRILLATION

Abstract

Local impedance (LI) measurement can predict tissue heating during RF ablation. To evaluate the utility of prespecified target LI to prospectively guide high power, short-duration (HPSD) RF ablation for PV isolation. This is a single-center prospective study of 44 consecutive patients who underwent initial PV isolation for AF. Circumferential ablation around the antrum of each PV was performed using using a 4 mm tip open irrigation RF ablation catheter with an LI sensor. RF energy was applied at each site at power output of 50 W. Adequacy of each RF application was solely guided by LI measured from the ablation catheter. PV electrograms were not monitored during RF ablation. Annotation of RF ablation applications was based on predefined parameters: the: (1) catheter stability <3 mm; (2) LI drops by >5 Ω (regardless of baseline LI) within the first 5 seconds; and (3) RF application duration of >5 seconds. Each tagged RF application was continued for a total duration of 6-10 seconds for the LA posterior wall and 10-15 seconds for other LA regions. If the LI failed to drop quickly (>5-Ω decrease within the first 5 seconds energy delivery), RF application was interrupted and ablation catheter adjusted to achieve better tissue contact, and RF was reapplied. RF application was stopped if esophageal temperature rose to >40°C or LI dropped by >30 Ω. Ultrahigh-density mapping was performed after first pass encircling of all PVs with inter-lesion distance of 4 mm. First-pass PV isolation was achieved in 163 of 175 PVs (93.1%) in 34/44 patients (77.3%). In 5 PVs (in 5 patients), high-density mapping identified 11 LA-PV conduction gaps at sites where RF applications did not meet annotation criteria (due to catheter instability, esophageal heating, or lack of sufficient LI drop). In 7 other PVs (in 7 Patients), 10 conduction gaps were identified at sites where RF applications did satisfy our ablation protocol. Compared to sites with tagged ablation points with conduction gaps, sites without gaps (suggestive of acutely effective ablation lesions) exhibited significantly larger absolute LI drop (16.4 ± 6.7 Ω vs. 12.2 ± 4.6 Ω, p=0.01) and % change in LI (14.8% ± 5.1% vs. 10.9% ± 4%, p=0.013) during RF energy delivery. The anatomical distribution of conduction gaps is shown in Figure. No steam pops or major complications occurred during or after the procedures. Our prespecified LI target drop magnitude may be used prospectively to guide safe and successful HPSD ablation for AF.