This study focuses on a novel mutation, T1857I, in the C-terminus of Nav1.5 that is linked to a family with an inherited arrhythmogenic phenotype characterized by atrial tachy-arrhythmias and polymorphic ventricular arrhythmia occurring at rest and with adrenergic stimulation, and a strong family history of SCD, akin to but not typical of CPVT. This evidence concerns the gene SCN5A and catecholaminergic polymorphic ventricular tachycardia.