Microsecond pulsed electric fields induce myocardial ablation by secondary mitochondrial damage and cell death mechanisms

Microsecond pulsed electric field (µsPEF) is a newer treatment modality to replace catheter ablation treatment of Atrial fibrillation (AF) due to its fewer side effects. This study aims to find out experimental parameters that effectively induce cardiomyocyte death and the precise mechanisms for microsecond pulsed electric fields (µsPEFs) ablation of cardiomyocytes. CCK8 and flow apoptosis analysis were employed to examine the effects of different µsPEFs on cardiomyocytes in vitro. The mechanisms by which the µsPEFs ablation works were explored through a combination of transcriptome study, transmission electron microscope (TEM) observation of mitochondria, pathway enrichment analysis, and interaction network analysis. In vivo experiments on mice involving HE, Masson, TUNEL and Immunofluorescence staining examinations were conducted to confirm the in vitro experimental results. When more than 30 pulses were applied, a continuous decline in post-ablation relative cell activity was observed, decreasing from 0.36 at 3 h to 0.13 (p < 0.01) at 48 h. Notably, at a voltage of 1500 V/cm and a pulse count of 50, the apoptosis rate exceeded 95%, coupled with a more stable and consistent cell ablation. Following ablation, a notable upregulation in mitochondria-related transcription levels was observed, accompanied by mitochondrial membrane disruption and an increase in Cytochrome C levels. Within a certain range, an increase in voltage and number of electric pulses corresponded to a greater quantity of cell mortality in the ablation zone. The µsPEFs induced cell injury by impairing mitochondrial function and potentially triggering the mitochondrial apoptosis pathway.