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Long QT Syndrome

Long QT syndrome (LQTS) is a rare heart disorder caused by disruptions in your heart's electrical activity.

The disorder is named for readings on an electrocardioagrram (ECG), which measures heartbeats as five waves. Each wave has a letter designation: P, Q, R, S and T. The relationship between the Q and T waves is known as the QT interval. When this interval lasts longer than it ordinarily should, the timing of your heartbeat is disrupted and can lead to dangerous arrhythmias.


LQTS can appear suddenly. The first symptom often is fainting from arrhythmia caused by LQT.

If you don't seek immediate treatment, you could suffer from cardiac arrest or die.

Strenuous exercise, stress, shock and fright can trigger LQTS in some cases.

Risk factors

LQTS is often genetic. If one of your family members is diagnosed with LQTS, you and your parents, siblings and children should get tested.

Medications can also cause acquired LQTS. Ask your physician whether any medications you're taking can cause LQTS.

Diagnosis and treatment

An electrocardiogram (ECG) is the primary way LQTS is diagnosed. Since exercise can also trigger LQTS, you may be asked to take a treadmill test.

Genetic blood tests may help identify the abnormal gene that can cause genetic LQTS.

Once you have been diagnosed with LQTS, your treatment may include medications such as beta blockers, which help prevent a sudden heart attack.

Your physician may also recommend that an electrical device be implanted in your chest, such as an implantable cardioverter defibrillator or a pacemaker. These devices can detect and correct your irregular heartbeat when it happens.


Regular follow-up with your physician is the key to successful management of LQTS.

Medications, implanted medical devices and lifestyle changes are also major factors in decreasing your risk of a cardiac event. Those with a diagnosis of LQTS should:

  • Avoid strenuous exercise and activities
  • Avoid high-stress situations
  • Avoid startling noises and other shocking situations
  • Consider adding potassium to their diet to prevent LQTS complications
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