Long QT syndrome (LQTS) is a disorder of the heart’s electrical activity. It can cause sudden, uncontrollable, dangerous arrhythmias (ah-RITH-me-ahs) in response to exercise or stress. Arrhythmias are problems with the rate or rhythm of the heartbeat.

People who have LQTS also can have arrhythmias for no known reason. However, not everyone who has LQTS has dangerous heart rhythms. When they do occur, though, they can be fatal.


Congenital long QT syndrome is an uncommon disease (1 in 2000 live births) that is characterized by a long QT inter­val (usually greater than 470 ms) and ventricular arrhyth­mia, typically polymorphic ventricular tachycardia. It is due to a genetic abnormality in ion channel activity and may be associated with increased cardiac sympathetic activity. It may occur in the presence of congenital deafness (Jervell- Lange-Nielsen syndrome

) with autosomal recessive inheri­tance.

Acquired long QT interval is usually secondary to use of antiarrhythmic agents, methadone, antidepressant medications, or certain antibiotics; electrolyte abnormali­ties; myocardial ischemia; or significant bradycardia. Nota­bly, many antiarrhythmic medications that are effective for the treatment of atrial and ventricular arrhythmias may significantly prolong the QT interval (sotalol, dofetilide).

Signs and symptoms

The clinical presentation of congenital or acquired long QT syndrome is variable. Patients may be asymptomatic or have palpitations, sustained tachyarrhythmia, syncope, or sud­den cardiac arrest. In young patients with congenital long QT syndrome, syncopal episodes may be misdiagnosed as a primary seizure disorder.


The management of acute torsades de pointes differs from that of other forms of ventricular tachycardia. Class Ia, Ic, or III antiarrhythmics, which prolong the QT interval, should be avoided—or withdrawn immediately if being used. Intravenous beta-blockers may be effective, especially in congenital forms of long QT syndrome; intravenous magnesium should be given immediately. Increasing the heart rate, whether by infusion of beta-agonist (dopamine or isoproterenol) or temporary atrial or ventricular pacing, is an effective approach that can both break and prevent the rhythm.

Long-term management of acquired long QT syndrome generally involves withdrawal of the offending medication and correction of any electrolyte abnormalities. For congenital long QT syndrome, prognosis is excellent if the arrhythmia is controlled. Long-term use of beta-blockers (particularly propranolol or nadolol) is the mainstay of treatment. Surgical cervicothoracic sympathectomy should be considered for patients who do not respond to or are intolerant of beta-blockers.


ICD implantation is recommended for patients in whom recurrent syncope, sustained ventricular arrhythmias, or sudden cardiac death occurs despite medical therapy. An ICD should be considered as primary therapy in certain patients, such as those in whom sudden cardiac arrest is the initial presentation of the long QT syndrome.


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