However, enhanced NCX1 activity and Ca2+ extrusion might be beneficial in subgroups of patients with HF with preserved ejection fraction (HFpEF), in which NCX1 activity has been reduced because of, e.g., increased and dominating Na+ levels (Eisner et al., 2020), and in HF that involves increased levels of pSer68-PLM (Bossuyt et al., 2005; Hafver et al., 2016). This evidence concerns the gene SLC8A1 and hydrops fetalis.