SCN5A and hypertrophic cardiomyopathy: Sodium channel blockers have negative inotropic properties that preclude use for patients suffering from cardiomyopathies, particularly those associated with mutations in the SCN5A gene and other conditions overlapping with BrS, such as hypertrophic cardiomyopathy (HCM) and arrhythmogenic right ventricular cardiomyopathy (ARVC) (41–44).