Assessment of temperature dynamics in pulsed field ablation with a variable-loop circular catheter: a comparative analysis of waveform configurations and irrigation rates in specimens of bovine ventricular myocardium

Aims Pulsed Field ablation (PFA) is a non-thermal ablation modality with functional myocardial sparing. Recent evidence suggests that clinically used PFA systems may produce non-negligible thermal effects, particularly at the tissue-catheter interface, potentially increasing the risk of thrombo-embolic complications. This study sought to characterize the temperature dynamics of two PFA pulse waveforms, delivered using a variable-loop circular catheter, under different irrigation conditions. Methods and results In total, 132 ablations were performed on 31 bovine myocardial tissue specimens, using Sequence_1 and Sequence_2 at two different irrigation rates - 4 and 30 mL/min. Maximum temperatures and their rise from baseline were measured at the tissue surface, and at 3 and 7 mm depths, across different ablation conditions. Sequence_1 at 4 mL/min produced the highest surface temperature (56.4°C [54.9-58.4]) and temperature rise (ΔT: 19.4°C [17.9-21.4]). Sequence_2 at 30 mL/min showed the most favourable thermal profile, with significantly lower surface temperatures (40.8°C [37.9-43.0], ΔT: 3.8°C [0.9-6.0], P < 0.0001). At 3 mm depth, temperature increases were reduced for all settings, but remained highest with Sequence_1 at 4 mL/min (42.5°C, ΔT: 5.5°C). At 7 mm depth, temperatures remained close to baseline. Both waveform and irrigation optimization independently and synergistically reduced tissue heating, with the Sequence_2 at 30 mL/min achieving the lowest thermal load at all depths. Conclusion This study confirms that PFA can induce relevant thermal effects, especially at the tissue interface. However, waveform optimization and active cooling significantly mitigate these effects. Such strategies to minimize thermal effects should be implemented in clinical practice to enhance procedural safety.