Long QT syndrome
Mutations resulting in a gain-of-function are causal for Long QT syndrome type 3 and are also more recently implicated in multifocal ectopic Purkinje-related premature contractions (MEPPC) Some gain-of-function mutations are also associated with AF and DCM. Gain-of-function of NaV1.5 is generally reflected by an increase in INa,L, a slowed rate of inactivation or a shift in voltage dependence of activation or inactivation (resulting in an increased window-current).