Long-QT syndrome (LQTS) is characterized by a prolonged, heart-rate corrected QT (QTc) interval in the ECG. Typical QTc values are >480 ms. Two different forms of LQTS are known: an inherited and thereby often familial form of LQTS (congenital form / cLQTS) and the acquired, often reversible form (aLQTS). For typical ECG recordings see references [1, 7, 8, 9, 12]. The disease is characterized by a dysfunction of cardiac ion channels responsible for myocellular repolarization. In consequence, patients with either cLQTS or aLQTS have an increased risk of polymorphic ventricular tachyarrhythmias of the so-called Torsades de Pointes type (TdP). An estimated 10% of sudden infant deaths and 20% of unexplained adult deaths are thought to be due to LQTS. The congenital form has an estimated prevalence of 1: 2,000 and is caused by pathogenic variants in cardiac ion channel genes that directly lead an altered ion channel function due to ion current reduction or protein-protein interactions influencing correct ionic current flow. There are >10 genetic subforms known; the LQT1, LQT2 and LQT3 are the most common ones.

The most common subform is LQT1 (42-54%) where TdP are often triggered by high physical exercise (e.g., swimming) or emotional stress, i.e. adrenergic conditions. In contrast, in the second most common type, LQT2 (35-45%), known arrhythmia triggers are rest, emotions, acoustic triggers, and physical stress. In the subform LQT3, resembling 7-8% of all, possible triggers are rest or sleep, vagotonic conditions. The first clinical manifestation, often syncope, may occur in childhood or young adulthood due to exposure to triggers. In the majority (95%), the ventricular arrhythmia is selfterminating and spontaneously converts into sinus rhythm. In a minority, however, TdP may degenerate in ventricular fibrillation and cardiac arrest, fatally without outside help. The diagnosis is often difficult and requires precise ECG assessment and genetic diagnostics. This is beyond the scope of this short review. In LQT1, β-receptor blockers are effective in preventing clinical events. This effect is reduced in LQT2 patients and only slightly pronounced in LQT3 where sodium channel blocking agents such as mexiletine might be effective. Left cardiac sympathetic denervation (LCSD) is an ultimate and additive therapy to β-receptor-blockers. The use of an ICD for high-risk patients is recommended, but should not replace β-receptor blocker therapy, life-style modification and trigger prevention.