Inherited long QT syndrome (LQTS) is a cardiac disease characterised by episodes of ventricular tachyarrhythmia, presenting as syncope or sudden death. Untreated, the annual mortality rate is 1-2%. Sudden death has been reported as the first manifestation of the disease in some cases. Therefore, early (pre-symptomatic) diagnosis and management may save lives. However, clinically false negative relatives are also at risk of sudden death. On this basis we conclude assessment of relatives should be extended with genetic testing.