Analysis of thermal effects from pulsed field ablation

Abstract Background Pulsed field ablation (PFA) has been described as non-thermal, but abundant data exist in oncology applications [1-3], and growing data are emerging in cardiology [4], highlighting that thermal effects are in fact present with PFA. The particular parameters (such as voltage, pulse gap, pulse number) that most influence the development of thermal energy during PFA are less clear. Purpose We sought to evaluate the thermal effects arising from pulsed field ablation of myocardial and esophageal tissue over a range of typical peak voltage operating conditions. Methods Using a three-dimensional computer model of the left atrium and esophagus, we quantified the thermal effects from PFA applications over a range of peak voltage operating conditions (1 kV, 1.5 kV, and 2 kV). Bipolar electroporation was simulated using one electrode as the anode and the other as a grounded cathode. Far-field and symmetry boundaries were set as electrically insulating. A monophasic waveform with a pulse duration of 100 µs and pause between pulses of 1 s was applied for a total of 50 pulses in a single train. Myocardial thickness was 1.5 mm, esophageal thickness was 2 mm, and the pericardial fat layer was varied between 0.3 and 0.75 mm. Results Minimal temperature rise in the esophagus was seen with 1 kV pulses (corresponding to 13.4 J input). With 1.5 kV and 2 kV peak voltages (corresponding to 32.3 J and 66.2 J), temperature elevations reaching 46.3 °C and > 62 °C were seen, respectively. These elevations occurred after only a single pulse train of 50 pulses, implying that further elevations in temperature would be seen with subsequent applications. Conclusions Thermal effects from PFA depend on total energy deposited, of which peak voltage is an important component. Current commercially available systems appear to have the potential to induce collateral thermal injury, particularly with a thin pericardial fat layer, and with repeated applications of pulsed field energy.