Signs & Symptoms Heart & Vascular

Long QT Syndrome
Signs and Symptoms

Although the exact frequency of LQTS is unknown, it may be as prevalent as one in 5,000 people and may cause 2,000 to 3,000 sudden deaths in children and young adults each year in the United States.

The most common symptom of long QT syndrome (LQTS) is a sudden loss of consciousness or fainting, called syncope. The condition may also cause seizures and in some instances, cardiac arrest and sudden death.

The severity of the condition varies greatly. Some people never experience syncope and others may have frequent episodes that could possibly lead to cardiac arrest and sudden death.

It is important to note that symptoms usually occur without warning and are caused by a very fast heart rhythm called torsade de pointes. Syncope may occur during or just after physical exertion, emotional excitement or sudden auditory arousal, such as from an alarm clock.

UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.

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