To assess the ability to model AF using iPSC-aCMs in PC, peripheral blood mononuclear cells (PBMCs) were isolated from a patient with drug refractory AF who was heterozygous for a missense mutation (E428K) in SCN5A, which leads to gain of function as characterized by a significantly larger late sodium current (INaL) than wild-type (WT) controls (38). The gene discussed is SCN5A; the disease is atrial fibrillation.