Changes in local endocardial electrograms immediately after PFA show dose-dependent variations

Abstract

Background/Introduction. Pulsed field ablation (PFA) is a novel nonthermal cardiac ablation technology based on irreversible electroporation. The behaviour of local electrograms after PFA has been poorly characterized and it remains unknown if it is possible to differentiate between different electroporation levels based on local electrogram analysis. Purpose. The objective of this study was to characterize the alterations in bipolar and unipolar endocardial electrograms after performing PFA at different doses. Methods. Five anesthetized pigs were submitted to PFA treatments. Endovascular access to the right atrium was gained through the femoral vein to create a line of ablation between the superior and inferior vena cava using a focal monopolar catheter. The catheter was switched between a conventional cardiac navigation system (CARTO system) and a custom PFA generator. Two different PFA doses were used: a high dose (HD-1600V) at top and bottom of the line and a low dose (LD-1000V) in the central part of the ablation line. Bipolar and unipolar electrograms were recorded with the ablation catheter before and immediately after each ablation. Additionally, high-density electroanatomical maps were acquired with a multielectrode catheter before and immediately after the procedures. Four weeks later, the animals were remapped again and subsequently euthanized. Atrial tissue was removed and processed to identify the presence of fibrosis in the previously ablated lesions. Results. We performed 106 ablations (84 high dose vs. 22 low dose). Four weeks later, histological staining of chronic lesions revealed that the HD lesions were larger and more fibrotic than the LD (Figure 1). Immediately after each ablation R/S-wave amplitudes and their corresponding |dV/dt|max decreased for the bipolar and unipolar electrograms. The percentages of bipolar electrogram reduction HD vs. LD were: R wave 73% vs. 39%, S wave 68% vs. 37% and |dV/dt|max 81% vs. 38%; 1 way-ANOVA p<0.05 for all, Figure 2). The R-wave amplitude in M1-M2 was significantly lower in HD compared to LD (HD vs. LD: 0.3 ± 0.2 mV vs. 0.7 ± 0.6 mV; 1 way-ANOVA p<0.01). S-wave and |dV/dt|max of unipolar electrograms presented a similar behaviour (M2 |dV/dt|max HD vs. LD: -116 ± 118 mV/s vs. -260 ± 267 mV; 1 way-ANOVA p<0.01). Conclusion. Local electrograms display PFA dose-dependent variations. This information could result useful to create new metrics to assess in real time the performance of PFA systems.