Accessory subunits involved in modulating Nav1.5 inactivation: β-subunit (green),59-74,80,81,83,84,143-145, fibroblast growth homologous factors (FHFs) (purple),96,97,99,121,122 and the CaM/Ca2+ complex (yellow).24,89,91,95-97,146-150 Environmental factors including extracellular pH,101,102,104,105,110 and temperature103,112-120,122 may also modulate Na+ channel inactivation.