SLC8A1 and atrial fibrillation: Elevated levels of NCX1protein have been observed in patients with AF, and an overly active NCX1 canpromote action potential alternans, thereby increasing susceptibility to AF [23].Wang et al. [24] found that FK506-binding protein 5 (FKBP5) issignificantly under-expressed in atrial samples from patients with persistentlong-term AF.