Biophysical numerical model for pulsed field ablation.

Pulsed-Field Ablation (PFA) is a non-thermal technique for the treatment of cardiac arrhythmias. Predictive numerical models capable of reliably predicting lesion size and shape remain limited. We introduce a biophysics-grounded and inherently anisotropic model for cardiac PFA, derived by homogenization of a microscopic electroporation model. Unlike standard approaches relying on nonlinear tissue conductivities and macroscopic electric-field-based ablation criteria, our framework naturally incorporates cellular geometry and orientation through the local transmembrane voltage, which provides a biologically meaningful criterion to predict lesion sizes. Using this transmembrane voltage-based criterion, we demonstrate that fiber-induced anisotropy strongly influences lesion morphology, leading to markedly different lesion shapes along and across the myocardial fibers. In particular, the proposed approach improves the prediction of lesion width-to-depth ratios, which are poorly captured by standard criteria. Furthermore, we propose a simple static model to account for two or more consecutive pulses. Preliminary numerical results show that the computed lesion depths are consistent with epicardial ventricular experimental observations. This work provides a mechanistic modeling framework for PFA that links cell-scale and tissue scales and highlights the importance of local tissue anisotropy.