Abstract Body (Do not enter title and authors here): Background: Pulsed field ablation (PFA) is an innovative modality for treating arrhythmias that is mostly non-thermal and renders myocardial tissue non-viable by creating pores in cardiac cell membranes. The impact of contact force (CF) on PFA efficacy is not well characterized.

Hypothesis: We hypothesize that, while contact is necessary for PFA, increasing CF will not have a significant effect on in vivo ablation lesion size.

Aim: We seek to investigate the effects of CF on acute PFA lesions in a beating porcine heart model.

Methods: The ventricles of 7 porcine animals were ablated in vivo with PFA (500V, at 20μs for 50 pulses separated by 200ms) using a focal bipolar irrigated ablation catheter and BTX 830 electroporation generator (Harvard Apparatus). CF was measured before and after each PFA application using CARTO 3. Lesions were divided into standard CF (5-15g), high CF (16-30g), and very high CF (>31g).

Results: A total of 46 lesions were analyzed. Gross pathology showed no significant difference in maximum width, lesion depth, and lesion volume between the three groups (Figure 1A-B). Linear regression showed a decrease of 0.003 mm in depth (depth = -0.003 × CF + 1.8, R = 0.05), an increase of 0.01 mm in width (width = 0.01 × CF + 5.7, R = 0.09), and a decrease of 0.05 mm³ in volume (volume = -0.05 × CF + 26.8, R = 0.03) for each additional gram of CF (Figure 1C).

Conclusion: While contact is necessary, increasing CF did not have a significant effect on in-vivo PFA lesion dimensions in a beating porcine heart model.