Impact of contact parameters on lesion dimensions during circular Pulsed-Field ablation in ex vivo and in vivo models.

Pulsed field ablation (PFA) is a novel nonthermal therapy for cardiac arrhythmias. The influence of contact force (CF), contact status, and application count on lesion characteristics in bipolar biphasic circular PFA remains uncertain. This study investigated lesion dimensions and acute histopathological changes using potato and porcine myocardial models. PFA was delivered in potato models under non-contact conditions or stratified contact forces (0–25 g, 25–50 g, > 50 g; 5 applications each). Porcine myocardium lesions were created with 1, 3, or 5 applications under contact or non-contact. Contact conditions yielded deeper lesions than non-contact in potato models (p < 0.001), with no significant differences among CF subgroups. In porcine myocardium, contact lesions were significantly deeper after three (4.82 ± 0.91 mm vs. 3.33 ± 0.74 mm; p < 0.05) and five applications (5.80 ± 0.49 mm vs. 3.55 ± 0.45 mm; p < 0.001) compared to non-contact. Lesion width was unaffected by contact status or application number. Histology demonstrated contraction-band necrosis, neutrophilic infiltration, edema, and hemorrhage with preserved microvasculature; these changes were more pronounced under contact. In the phantom model, lesion dimensions were predominantly governed by contact stability rather than contact force magnitude. In vivo validation confirmed that maintaining stable contact is a prerequisite for effective lesion formation. Furthermore, increasing the number of applications augmented lesion depth in porcine myocardium, while width remained stable.