Analytical model of large-diameter spherical-like catheter for pulsed field ablation in treating cardiac arrhythmias

Abstract Objective: To study the electrical performance of large-diameter spherical-like catheters used for pulsed field ablation (PFA) in treating cardiac arrhythmias, especially evaluating the effect of electrode radius, applied voltage and maximum current delivered on the PFA-induced lesion depth.
Approach: An analytical model was proposed which used spherical coordinates to estimate the value of the electric field around a spherical metal electrode. Lesion depth was estimated by the myocardium lethal electric field threshold. The paper also reviews the literature and proposes a relationship between this threshold and the total cumulative duration of the pulses applied during PFA.
Main results: Despite the model´s simplicity in geometric terms, the estimated values of baseline impedance (44 Ω) and impedance drop due to PFA (7-9 Ω) are closely related to those observed in experimental studies (43 Ω and 5-7 Ω, respectively). The PFA-induced lesion size potentially increases with the applied voltage, but this is only true if the generator can provide the electrical current needed to maintain the required voltage. A nonlinear relationship was identified between PFA-induced lesion depth and the electrode diameter, which was also modulated by the total duration.
Significance: The analytical model offers a physical explanation for the PFA-Induced electrical phenomenon, while emphasizing how certain technical characteristics (maximum current, applied voltage, electrode diameter) can affect the depth of the lesion.