Long QT syndrome (LQTS) is a disorder of the heart's electrical system. People with this syndrome are susceptible to an abnormally rapid heart rhythm called "Torsade des pointes." Long QT syndrome is characterized by a prolongation of the QT interval on ECG and a propensity to ventricular tachyarrhythmias, which may lead to syncope, cardiac arrest, or sudden death. LQTS is usually inherited as an autosomal dominant trait. In the case of LQT1, which has been mapped to chromosome 11, mutations lead to serious structural defects in the person's cardiac potassium channels that do not allow proper transmission of the electrical impulses throughout the heart. It is associated with syncope (loss of consciousness) and with sudden death due to ventricular arrhythmias. In the long Q-T syndrome, the above-described Q-T interval is prolonged. Arrhythmias in individuals with LQTS are often associated with exercise or excitement. The cause of sudden cardiac death in individuals with LQTS is ventricular fibrillation. Congenital LQTS is a rare disorder that is usually inherited (passed down through family members).

It usually affects children or young adults. In other cases, LQTS can be caused by certain medicines, or it can be the result of a stroke or some other neurologic disorder. LQTS can lead to an abnormal heart rhythm (arrhythmia); fainting or loss of consciousness (syncope); or even sudden death. Long QT syndrome may explain some rare instances of sudden death in young people where no obvious cardiac heart abnormality is found. People with this syndrome may show prolongation of the Q-T interval during physical exercise, intense emotion (such as fright, anger or pain), or by a startling noise. In LQTS, QT prolongation can lead to polymorphic ventricular tachycardia, or torsade de pointes, which itself may lead to ventricular fibrillation and sudden cardiac death. Individuals with LQTS have a prolongation of the QT interval on the ECG. The Q wave on the ECG corresponds to ventricular depolarization while the T wave corresponds to ventricular repolarization. The QT interval is measured from the Q point to the end of the T wave. People who have LQTS are at risk for syncope and sudden death, often at a young age.

Causes of Long QT syndrome

The common causes and risk factor's of Long QT syndrome include the following:

LQTS can be caused by certain medicines, or it can be the result of a stroke or some other neurologic disorder.

Heart medications.

Lipid-lowering medications.

Psychotropic medications.

Blood relatives of family members with LQTS.

You also have an increased risk for LQTS if other members of your family have the disorder.

Symptoms of Long QT syndrome

Some sign and symptoms related to Long QT syndrome are as follows:

Abnormal heart rhythms.

Seizures.

Sudden shortness of breath.

Fainting: In people with long QT syndrome, fainting spells (syncope) are caused by the heart temporarily beating in an erratic way.

Sudden death.

Sudden chest pain.

In one type of inherited long Q-T syndrome, the person is also deaf.

Treatment of Long QT syndrome

The common causes and risk factor's of Long QT syndrome include the following:

There are treatments for long Q-T syndrome, including medications such as beta blockers.

Some people may benefit from an implantable defibrillator.

Propranolol and nadolol are the beta-blockers most frequently used, though atenolol and metoprolol are also prescribed in patients with LQTS.

When LQTS causes uncontrolled ventricular fibrillation, you might need an implantable cardioverter defibrillator (ICD). An ICD is a device that sends an electric shock to your heart to restore a normal heartbeat.

For many people with LQTS, the implantable defibrillator is the best treatment.