[The ICD as primary prevention. Rare indications].

The most frequent cause of sudden cardiac death (SCD) is underlying coronary artery disease. Healthy appearing young individuals are affected in a minority of cases. These individuals are usually diagnosed with electrical or genetically determined structural heart disease. Arrhythmogenic right ventricular cardiomyopathy, hypertrophic cardiomyopathy, long and short QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, and early repolarization syndrome are generally considered rare underlying causes of SCD in these young patients. Affected patients typically present with syncope or cardiac arrest. Occasionally, disease is diagnosed during family screening. Risk stratification is difficult in this patient population. Risk of sudden death has to be weighed individually against risks associated with an implantable cardioverter defibrillator (ICD) in these young patients.