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Long QT syndrome (LQTS) happens when your heart takes longer than normal to be ready to beat again. With LQTS, the timing of your heartbeats, heart rate, and rhythm can change. This can lead to a heart attack.

What are the causes?

The cause depends on the type of LQTS that you have. Types include:

a. Inherited LQTS. You're born with this. It's caused by a gene that's passed down through your family.

b. Acquired LQTS. You get this later in life. It may be caused by:

1. Certain medicines, such as antibiotics or medicines to treat depression.
2. Changes in electrolytes, which are salts and minerals in your body.
3. Heart disease, such as heart failure.
4. Thyroid gland problems.

What increases the risk?

You may be more at risk if:

a. You're female.

b. You have an eating disorder.

c. You throw up or have liquid poop for a long period of time.

d. Someone else in your family has LQTS.

e. Your or someone else in your family has a history of:

1. Fainting with no known cause.
2. Drowning.
3. Sudden death.

What are the signs or symptoms?

Symptoms may include:

1. Fainting.
2. Fast or uneven heartbeats.
3. Seizures.

Some people have no symptoms.

Symptoms of inherited LQTS almost always start before age 40.

How is this diagnosed?

You may be diagnosed based on your health history and an exam. You may also have tests, such as:

a. Blood tests to look for:

1. Genes that cause LQTS.
2. Changes in electrolytes.

b. An electrocardiogram (ECG). This test records the electrical signals of your heart.

c. A test in which you wear a device to record your heart's electrical signals while at home.

d. An exercise stress test. This looks for signs of blocked arteries when the heart is stressed.

How is this treated?

There's no cure for LQTS, but treatment can help with symptoms. Treatment depends on the cause and if you have a family history of sudden death. You may be told to:

1. Make changes to your daily life.
2. Avoid certain sports.
3. Take supplements.
4. Take heart medicines.
5. Have an implantable cardioverter-defibrillator (ICD) put in. This device senses your heartbeat. It shocks your heart back to a normal heart rate as needed.

Follow these instructions at home:

Medicines

1. Take your medicines only as told.
2. Talk with your health care provider before you take any new medicines or supplements.

Lifestyle

a. You may need to avoid:

1. Doing things or going places that may cause stress.
2. Sudden loud noises.
3. Swimming and diving.

b. If you drink alcohol:

1. Limit how much you have to:
2. 0–1 drink a day if you're female.
3. 0–2 drinks a day if you're male.
4. Know how much alcohol is in your drink. In the U.S., one drink is one 12 oz bottle of beer (355 mL), one 5 oz glass of wine (148 mL), or one 1½ oz glass of hard liquor (44 mL).
5. Do not smoke, vape, or use nicotine or tobacco.

General instructions

1. Tell the people you live with about signs of sudden heartbeat changes.
2. Wear an alert bracelet or necklace that says you have LQTS and gives your contact info.
3. Get treatment and support if you feel afraid, worried, or stressed.
4. Keep all follow-up visits. Your treatment plan may need to change over time.

Contact a health care provider if:

1. You have stress.
2. You feel worried, sad, or hopeless.
3. You have a long period of throwing up.
4. You have liquid poop.

Get help right away if:

1. You have chest pain.
2. You have trouble breathing.
3. You have fast or uneven heartbeats.
4. You faint.
5. You have a seizure.

These symptoms may be an emergency. Consult a Doctor Immediately.

1. Do not wait to see if the symptoms will go away.
2. Do not drive yourself to the hospital.

This information is not intended to replace advice given to you by your health care provider. Make sure you discuss any questions you have with your health care provider.