These findings are also consistent with hypomorphic SCN5A variants being associated with conduction disorders.5,6,18 Other known side effects of class 1 antiarrhythmic sodium channel blockers are atrial flutter, ventricular tachycardia, ventricular fibrillation, Torsades de pointes, and Brugada-like patterns. Here, SCN5A is linked to ventricular tachycardia.