Background: Pulsed field ablation may evolve into an efficient alternative to traditional RF ablation for cardiac arrhythmia treatment. However, achieving irreversible tissue electroporation is critical to suppress arrhythmic pathways, raising the need for accurate characterization of lesion geometry and transmurality.
Objective: To understand the physics behind the tissue response to pulsed field ablation, we propose a quasi-dynamic model that quantifies tissue conductance at end electroporation and identifies the regions that have undergone fully irreversible electroporation (IRE).
Methods: The model uses several parameters: baseline (0.2 S/m) and fully electroporated (0.8 S/m) tissue conductance, critical electric field depth at reversible (200 V/m) and irreversible (450 V/m) electroporation, and applied voltage amplitude. The model numerically solves the electric field diffusion into the tissue by iteratively updating the tissue conductance until equilibrium at end electroporation. The model yields the steady-state tissue conductance map used to identify the irreversible lesion and lesion penumbra.
Results: We conducted numerical experiments mimicking a lasso catheter featuring 9 – 3 mm electrodes spaced circumferentially at 3.75 mm and fired sequentially using a 1500 V and 3000 V pulse amplitude. The IRE lesion region has a surface area and volume of 780 mm2 and 1411 mm3, respectively, at 1500 V, and 1178 mm2 and 2760 mm3, respectively, at 3000 V. Lesion discontinuity was observed at 5.0 mm depth with 1500 V, and 7.2 mm with 3000 V. Transverse views tissue conductance profiles through the model-predicted lesions show the formation of lesion gaps beyond maximum-lesion connected depth.
Conclusion: The proposed quasi-dynamic model yields tissue conductance maps, predicts the fully irreversible lesion and reversible lesion penumbra at end electroporation, and confirms larger lesions with higher pulse amplitudes. Future work will predict time-based tissue response given specific pulse duration and delivery of sequential pulse trains, as well as compare numerical and experimental results.