Impact of pulse duration on cardiac electroporation: nanosecond pulses enhance cardiomyocyte selectivity and promote a Raman-detected shift towards apoptotic cell death.

Aims: Pulsed field ablation (PFA), a cardiac ablation technique using microsecond pulsed electric fields (µsPEF), is widely used in clinical settings, while nanosecond pulsed electric fields (nsPEF) have recently entered clinical trials. Selective ablation of cardiomyocytes over endothelial cells is critical to prevent adverse remodelling, arrhythmias, and thrombosis, yet comparative data on nsPEF vs. µsPEF remain limited. This study investigates the cytotoxic effects and cell death mechanisms induced by nsPEF and µsPEF in cardiac and endothelial cells.

Methods and results: Human cardiomyocytes and endothelial cells were exposed to varying electric field intensities with nsPEF and µsPEF using custom-built automated setup to assess permeabilization and cell death. Raman spectroscopy evaluated biochemical changes in cardiomyocytes following electroporation. Ex vivo epicardial ablation was performed on murine hearts using customized electrodes. Maximal cardiomyocyte death occurred 24 h after both pulse types in vitro. Ex vivo, both pulse types produced visible myocardial lesions as early as 1 h post-exposure, with lesion size progressively increasing up to 4 h. Microsecond pulsed electric fields induced significantly greater endothelial damage (ED50: 1.18 kV/cm) than damage to cardiomyocytes (ED50: 1.28 kV/cm), whereas nsPEF affected both cell types equally (ED50: 7.27 kV/cm vs. 7.24 kV/cm). Raman spectroscopy analysis of exposed cells indicated that µsPEF predominantly triggered necrotic or unregulated cell death, while nsPEF exposure was associated with regulated, apoptotic cell death.

Conclusion: Pulse duration critically determines electroporation selectivity and downstream death pathways. Nanosecond pulsed electric fields favoured regulated cell death and cardiomyocyte selectivity, highlighting its potential to improve the safety and durability of PFA.