Fractionation of Nanosecond Pulsed Electric Fields Lowers Lethal Dose by Enhancing Cardiomyocyte Membrane Permeability.

Abstract

Background: Nanosecond pulsed electric fields (nsPEF) are a promising method for cardiac Pulsed Field Ablation, currently in early clinical trials. However, effective ablation often requires high voltages, more pulses, and higher frequencies, which can raise tissue temperatures due to Joule heating. Fractionated pulse delivery can help mitigate thermal effects and potentially evoke electrosensitization, increasing cell damage.

Objective: This study evaluates the effects of fractionated nsPEF on treatment efficacy and its selectivity against cardiomyocytes, aiming to determine if fractionation improves ablation outcomes.

Methods: Monolayers of HL-1 murine cardiomyocytes, MHEC 5-T murine endothelial cells, AC16 human cardiomyocytes, and HUVEC human endothelial cells were exposed to pulsed electric fields using a contact electrode operated by a custom robotic system. Cell viability and permeability were measured using wide-field fluorescence microscopy. Stained areas were matched to simulated electric fields for dose-response curves. Fractionation effects were also validated in an ex vivo murine model.

Results: Fractionation of nsPEF reduced the ED50 (electric field affecting 50% of cells) for plasma membrane permeabilization by 10% compared to a single train of 200 pulses (p < 0.0001). This translated into enhanced cardiomyocyte ablation, with fractionated exposure lowering the ED50 for cell killing by 13% (p < 0.0001). Ex vivo results further confirmed a larger ablation area with fractionated nsPEF (p < 0.0001).

Conclusion: Fractionated nsPEF improves cardiac ablation efficiency by enhancing membrane permeability and cell-killing effect. These findings suggest that fractionated delivery could optimize nsPEF therapies, offering a more effective approach for cardiac ablation.