The importance of electrode-tissue proximity in creating pulsed field ablation lesions: insights from a sub-acute preclinical model.

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We sought to evaluate the anatomic and functional lesion development over time at different atrial sites immediately following delivery of pulsed field ablation (PFA). Using a porcine model, PFA ablations were performed in the superior vena cava (SVC), right atrial lateral wall (RA), left atrial appendage (LAA), and right superior pulmonary vein (RSPV) using four different PFA profiles. Mapping was done sequentially in 5-20-min increments up to 280-min post lesion delivery for low voltage area (LVA) assessment and conduction velocity. Lesion characteristics were noted with voltage mapping immediately post ablation and at the serial time points. In 9 animals, 33 sites were ablated. None of the four different profiles across all sites showed any statistical difference on acute lesion formation or persistence. Higher tissue contact was observed in the SVC and RSPV and lower tissue contact was observed in the LAA and RA locations. Higher contact areas were noted to have higher density electroanatomic low voltage area (LVA) (12/14 vs 5/18, p = 0.01) and larger lesions on gross pathology (2 /14 vs 6/16, p = 0.01) compared to lower contact areas. Lesion regression occurred in 16/33 sites. Sustained lesions were significantly more prevalent in higher versus lower contact sites (65% vs 38%, p = 0.037). The development of significant and durable lesions for PFA in a porcine model appears to be dependent on tissue proximity and contact.