Monopolar and Bipolar Pulsed Field Ablation: Impact of Application Repetition and Epicardial Fat on Ventricular Lesion Formation

BACKGROUND: Given that current pulsed field ablation (PFA) systems have been optimized for atrial applications, extending this therapy to ventricular targets will require a deeper understanding of lesion formation and the key determinants influencing dose-response. OBJECTIVE: In this study, we systematically evaluate the impact of PFA waveform, application repetition, and the role of epicardial fat on lesion geometry in a swine model. METHODS: Fourteen swine underwent in vivo endocardial and epicardial ventricular PFA using the FARAPOINT (Boston Scientific™) focal catheter. Endocardial ablations were performed using either the commercially available bipolar waveform or an experimental monopolar waveform, using predefined application numbers (4, 6, or 8). Epicardial lesions, monopolar or bipolar, were created using 4 applications in targeted regions with and without fat. After a one-week survival period, animals were euthanized for histopathologic analysis. RESULTS: A total of 53 endocardial PFA lesions were analyzed. Lesion depth was significantly greater with monopolar (n=23) compared with bipolar (n=30) delivery (8.3±1.6 mm vs. 7.1±1.4 mm; p=0.015). Increasing the number of applications from 4 to 6 did not affect the lesion depth. However, increasing to 8 applications resulted in a significant increase in lesion depth with monopolar delivery but not with bipolar delivery. 23 epicardial PFA lesions were obtained. Lesion depth was significantly greater with monopolar compared with bipolar delivery (7.5±0.9 mm vs. 5.7±0.7 mm; p<0.001). The presence of epicardial fat did not appear to significantly affect lesion depth in either waveform configuration (monopolar: 7.8 ± 1.4 vs 7.0±0.9; p=0.37 and bipolar: 6.1±1.3 vs 5.4±0.7; p=0.65). CONCLUSION: We systematically compare monopolar and bipolar ventricular PFA lesion characteristics beyond nominal application doses. Monopolar PFA produced deeper lesions compared with bipolar delivery. This effect was further enhanced by increasing the number of applications in the monopolar mode, whereas additional applications beyond 4 had minimal impact on lesion size with bipolar delivery. Notably, the presence of epicardial fat showed a trend towards lower lesion depth.