In humans, drug effects on hERG, SCN5A (Nav1.5), KCNQ1/MinK and KCND3/KChiP2 (Kv4.3) channels often lead to Long QT syndrome (LQTS) or Short QT syndrome (SQTS), including Torsade de Pointes (TdP) arrhythmias, fraught with ventricular fibrillation and ultimately death [11], [12]. The gene discussed is KCND3; the disease is familial long QT syndrome.