The prevalence of sudden cardiac arrest after surgery for CHD is primarily related to the complexity of the congenital defect and the presence of residual defects, especially ventricular dysfunction. Among all causes of death in patients having CHD, about 19% lead to sudden mortality. The specific risk factors associated with the various congenital defects are poorly understood. The lone exception is tetralogy of Fallot, largely due to its high prevalence and the historically high post-operative survival rate. In tetralogy of Fallot, historical, haemodynamic, and electrical features contribute to risk, and electrophysiologic testing may be helpful, particularly to rule out risk. An implantable cardioverter–defibrillator is highly effective for secondary prevention in most forms of CHD, and future advances will improve its role in primary prevention.