SCN5A and long QT syndrome 3: SCN5A mutations are not limited to BrS but are associated with various other cardiac conditions, which include long QT syndrome (LQT3), cardiac conduction system dysfunction, myocardial contractile dysfunction, dilated cardiomyopathy, heart failure, sick sinus syndrome, familial atrial standstill, atrial fibrillation, ventricular arrhythmias (such as long QT syndrome type 3 and idiopathic ventricular fibrillation), and progressive cardiac conduction defect (Lenegre syndrome).