PO-03-065 PULSED FIELD ABLATION IS MORE EFFECTIVE THAN RADIOFREQUENCY ABLATION FOR THE RETREATMENT OF CHRONIC ABLATION SUBSTRATE

Abstract

There are known limitations of radiofrequency ablation (RFA) in extending and homogenizing prior ablation. The effect of pulsed field ablation (PFA) following prior RFA is not known. To evaluate the differential ability of PFA versus RFA to penetrate chronic RFA lesions. A two step in-vivo study was designed to simulate a retreatment scenario. Step I : Six Yorkshire swine underwent intentional ineffective RFA using IntellaNav StablePoint catheter in three sites: I.1) Right atrium: intercaval line with multiple intentional gaps, I.2) Left atrium: right superior and inferior common pulmonic veins with intentional gaps, and I.3) Left ventricle: discrete lesions. Step II: Following a survival period of ≈5 weeks animals were remapped. Chronic RFA was identified via voltage mapping. Next, animals were retreated as following: II.1) Right atrium: PFA over prior intercaval line using a focal PFA catheter (FARAPOINT), II.2) pulmonic vein isolation using a single shot PFA catheter (FARAWAVE), and II.3) Left ventricle: animals were randomized into two arms, PFA or RFA. In each arm, two types of sub-chronic lesions were performed: PFA and RFA on chronic RFA scar or PFA and RFA on healthy myocardium. PFA was applied with 4 applications of 2.0kV. RFA was applied with 30W, 60s or a local impedance drop >50Ω. After 2-5 day survival, atrial electrical block was assessed via electroanatomical mapping. All lesions were measured sub-gross for the extent of the chronic and sub-chronic zones. Right and left atria: Retreatment with focal PFA resulted in complete intercaval block (width: 16-28mm) and isolation of all targeted pulmonic veins, expanding and homogenizing the disparate chronic RFA lesions. Left ventricle: the mean depth for chronic RFA was 4.8±1.4mm. When RFA was performed on healthy substrate, the mean depth of the sub-chronic zone was 7.6±1.3mm, compared to 3.9±1.6mm when RFA was applied on chronic RFA scar (p<0.01). In contrast, the mean depth for sub-chronic PFA on healthy substrate was 7.0±1.6mm, similar to the sub-chronic PFA zone on chronic RFA (7.1±1.3mm; p=0.94) demonstrating that PFA has the ability to penetrate chronic RFA scar. PFA may be advantageous for ablation following prior RFA, producing lesions that, unlike RFA retreatment, are not significantly impeded by the presence of scar from the prior RFA.