Damijan Miklavčič

Pulsed field ablation (PFA) is a promising new treatment for atrial fibrillation (AF), in which pulmonary vein isolation is achieved by irreversible electroporation. Electroporation causes ATP to leak through the permeabilized membrane. ATP is required both for the healing of the cell membrane and for the functioning of ion pumps, such as sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) or Na+,K+-ATPase (NKA), which play a key role in maintaining continuous contractions of the heart muscle. We investigated the effects of electroporation on the expression of ion pumps and possible correlations with the activation of AMPK, the main energy sensor in cells. H9c2 rat cardiac cells were exposed to either monopolar or bipolar (H-FIRE) pulses. Cells lysed 4 or 24 h after electroporation were used for mRNA and protein expression analyses. Overall, both pulse protocols caused a dose-dependent downregulation of crucial SERCA and NKA isoforms, except for NKAα2 and β3, which were upregulated after 24 h. Monopolar pulses also decreased the phosphorylation of FXYD1, which may cause an inhibition of NKA activity. Both pulse protocols caused an increased AMPK activity, which may decrease both SERCA and NKA activity via calcium/calmodulin-dependent protein kinase. Our results provide important new insights into what happens in surviving cardiomyocytes after they are exposed to PFA.