Electrocardiographic markers of sudden cardiac death

Sudden cardiac death (SCD) is one of the major remaining challenges in clinical cardiology. Every year, approximately 300000 people die of sudden cardiac—in most cases, arrhythmic death. Unlike most other diseases, the first clinical manifestation of SCD is often fatal. Therefore, it is of utmost importance to detect patients at risk before their first event. Identification of these patients is most relevant as the implantable defibrillator provides a therapeutic option. The mechanisms that cause ventricular arrhythmias, the main cause of SCD, in hearts with advanced structural heart disease, for example, in patients with advanced cardiomyopathies or survivors of myocardial infarction, are well known, and clinical parameters such as QRS duration or left ventricular ejection fraction can reliably identify such patients. The past decade has identified another potentially large population of patients at risk for SCD due to primary electrical diseases. These patients, who often suffer from monogenic genetic abnormalities, can often be identified by a careful analysis of the surface electrocardiogram (ECG). Abnormal duration and/or shape of the ventricular action potential is one of the main changes associated with such primary electrical diseases: the first, and one of the most prevalent, is the long QTsyndrome. A prolongation of the QT interval (corrected QT interval N0.46) is an established sign of such a risk for proarrhythmia. The genetic causes of the long QT syndrome are mutations in potassium and sodium channels. Recently, the opposite sign, a relevant shortening of the QT interval, has been identified as another marker for SCD (so-called short QT syndrome). This condition is much less frequent than the long QT syndrome and may also be associated with mutations in potassium channels. A corrected QT interval b0.32 is suggestive of the diagnosis. Ventricular preexcitation, identified by a delta wave in the