Given the association of paroxetine with both BrS and LQTS and its established inhibiting effect on neuronal NaV1.4, NaV1.7, and NaV1.8 channel function [32,33,34], the main objective of this study was to investigate the effect of paroxetine on the functioning of the highly homologous cardiac NaV1.5 channel. This evidence concerns the gene SCN9A and familial long QT syndrome.