Prolonged QT syndrome (aka Long QT Syndrome) consists of multiple different variations including long QT type 1-12, Romano-Ward syndrome and Jervell-Lange-Nielsen syndrome.

A prolonged QT interval increases the risk for polymorphic ventricular tachycardia (Torsades de Pointes), which can result in sudden cardiac death.

Long QT 1: The ECG shows broad-based T waves. A majority of arrhythmias in this group occur during exercise. Beta-blockers are effective treatment and an implantable cardioverter defibrillator (ICD) is not required unless syncope or cardiac arrest occurs. The risk for sudden cardiac death is 1% at 1 year in this group on beta-blocker therapy.

Long QT 2: The ECG shows low amplitude T waves frequently with a notch. Arrhythmias are more likely to occur during rest/sleep, especially with sudden awakening and/or auditory stimuli. Beta-blockers are somewhat effective. The risk for sudden cardiac death in this group is 7% at 1 year while on beta-blocker therapy.

Long QT 3: The ECG frequently shows an extended ST segment with a relatively narrow T wave, which can be peaked. This is also the finding when hypocalcemia prolongs the QT interval. Beta-blockers are not effective. Arrhythmias also occur during rest, similar to long QT 2. Sudden cardiac death risk is 14% at 1 year while on beta-blocker therapy.

Treatment includes beta-blockers and implantation of an ICD.