Sudden cardiac death (SCD) is defined as a natural death due to cardiac causes, heralded by an abrupt loss of consciousness within one hour of the onset of acute symptoms. It is mostly initiated by a sudden inappropriate and extreme increase in heart rate (typically more than 200/min), eventually leading to a mechanical arrest of the heart. Virtually any cardiac disease can lead to this fatal arrhythmia but most commonly (up to 75%) the underlying disease is coronary heart disease. In about 20% of patients, the underlying heart disease is an idiopathic congestive cardiomyopathy and in <5%, SCD develops consequential to a primary electrical abnormality of the heart. SCD is among the most common causes of death in developed countries. It is estimated that in Belgium yearly 15 000 people die suddenly as a consequence of a sudden cardiac arrest. Virtually all patients who develop a sudden cardiac arrest (SCA) eventually die 10 to 15 minutes later. The only way of preventing death is by delivering an external electrical shock (defibrillation) within minutes after the SCA took place. Considering that immediate defibrillation is only rarely available and that medical therapy to prevent the occurence of fatal arrhythmias barely offers any benefit, the hope for saving the life of victims of a SCA relies on prophylactically implanting a defibrillator, i.e. the “Implantable Cardioverter Defibrillator” or ICD, that provides an immediate shock in case a life threatening arrhythmia does occur. This means that one has to try to predict who is likely to develop a SCA and subsequently implant a device that will respond appropriately in case the expected fatal event takes place.