Timing of consecutive ablations during PFA: implications of back-to-back or interval spaced lesion stacking

Introduction During pulsed field ablation (PFA) procedures, delivering back-to-back, or “stacked”, ablations has been associated with increased risk of electrode heating and a potential increase in thromboembolic events. Strategies that reduce thermal build up may therefore improve procedural safety. One potential approach is to delay or revisit a target site later in the procedure rather than administering an immediate second ablation. However, it is unknown whether postponing the second ablation may compromise lesion depth, compared to immediate sequential delivery. Purpose Accordingly, this study investigated whether delayed repeat ablation can maintain lesion depth while enabling a non-stacked workflow. Methods Three experimental models were used to investigate the effects of different time intervals between ablations: a benchtop potato model (N=80), an in vivo thigh preparation model (N=38), and an in vivo porcine ventricle model (N=28). In the potato model, ablations were performed as two ablations separated by intervals of 0 minutes (immediate), 1, 2, 3, 4, 5, 10, or 30 minutes. In the thigh preparation and ventricle model, a second ablation was delivered either immediately after the first, after a 5-minute delay, or after a 10-minute delay. All ablations were performed using the commercial variable loop circular catheter (VLCC) Sequence 1 waveform with 30mL/min irrigation. Analysis of Variance (ANOVA) was used to assess whether there were statistically significant differences in lesion depths among the groups. Results In the potato model, average lesion depth following 1 ablation was 5.5±0.8mm and 6.5±0.4mm following two immediate back-to-back ablations. Across all inter-lesion intervals in the potato model, lesion depth remained consistent and did not differ significantly from back-to-back ablations, even with delays of up to 30 minutes between applications (Figure 1). Similar data was achieved in the thigh prep and ventricle model, where there was no significant difference in lesion depth when comparing immediate repeat ablation with delays of 5 and 10 minutes. (Thigh Prep: 4.4±1.4mm, 4.6±0.9mm, 4.4±1.5mm, respectively, p=0.934; Ventricle Model: 5.1±1.2mm, 4.9±1.2mm, 4.4±1.2mm, respectively, p=0.475; Figure 2). In the ventricular model, a modest decline in lesion depth was observed with longer delays; however, this trend did not reach statistical significance. Conclusion Across three experimental models, lesion depth was preserved even with repeat ablation delays of up to 30 minutes in the potato model and 10 minutes in the in-vivo ventricle model, supporting a non-back-to-back, non-stacked workflow that preserves efficacy while improving the procedural safety profile.Figure 1Figure 2