Pulsed-Field Ablation in Ventricular Myocardium Using a Focal Catheter: The Impact of Application Repetition on Lesion Dimensions.

Background - Pulsed-field ablation (PFA) is a rapid and nonthermal energy with higher selectivity to myocardial tissue in comparison to radiofrequency ablation (RFA). However, its effects on ventricular myocardium, and titration of lesion dimensions have not been well studied. This study examined the effect of PFA on ventricular myocardium, and the influence of application repetition on lesion dimensions. Methods - An 8Fr lattice catheter with a compressible 9 mm nitinol tip was used with a PFA generator (Affera Inc) applying a bipolar and biphasic waveform (±1.3-2.0 kV, 4 sec per application). We examined the impact of single applications (1x) vs four repetitive applications (4x) interspaced by 10 seconds. The latter was performed to determine whether repetitions of a similar electrical field can increase lesion dimensions. Experiments were performed in an in-vivo porcine model and a survival period of 24 hours (n=6) or 23±5.4 days (n=6) for evaluation of early and late histopathological effects. Results - PFA in ventricular myocardium showed repetition dependency. Acute lesion depth and volume increased from 5.6±1.43mm and 860±362mm3 to 8.8±0.74mm and 2383±548mm3 for 1x and 4x applications, respectively (P<0.001 for both comparisons). This effect was maintained in the chronic lesion phase with lesion depth and volume of 3.9±0.92mm and 655±286mm3 compared with 7.3±0.83mm and 2170±488mm3, respectively (P<0.001 for both comparisons). Acute lesions showed well demarcated necrotic core without coagulation necrosis while chronic lesions showed tissue thinning with fibro-fatty replacement. Conclusions - PFA in ventricular myocardium exhibits repetition dependency as lesion dimension increases with consecutive applications of a similar electrical field.