Should patients with congenital heart disease and a systemic ventricular ejection fraction less than 30% undergo prophylactic implantation of an ICD? Implantable cardioverter defibrillator implantation guidelines based solely on left ventricular ejection fraction do not apply to adults with congenital heart disease.

A number of important prospective studies have firmly validated the idea that patients at elevated risk for sudden cardiac death (SCD) can have that risk reduced by the use of implantable cardioverter defibrillators (ICDs). Among patients resuscitated from a potentially lethal cardiac event, ICD placement is termed secondary prevention. Primary prevention is the extension of this protective principle to groups of patients who have yet to experience a cardiac arrest, but who by virtue of specific and carefully defined clinical characteristics are determined to be at elevated risk for this event.