Introduction Long QT syndrome type 3 (LQT3) is a highly lethal channelopathy. It is associated with delayed closing of sodium channels, resulting from mutations in the SCN5A gene, with an autosomal dominant pattern, responsible for 7-10% of all long QT syndromes (LQTSs). The initial presentation can have a wide spectrum, from asymptomatic to sudden death in the first year of life. The addition of class IB sodium channel blocker (mexiletine) to propranolol or nadolol is considered a gene-guided treatment, as […]