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Long QT Syndrome

What Is Long QT Syndrome?

Long QT syndrome is a condition that affects the electrical system of the heart. It takes longer for the heart to squeeze and then recover or "recharge." If it's not treated, the condition can be dangerous.

What Happens in Long QT Syndrome?

An area of the heart called the sinus node sends electrical signals that tell the heart to beat at a normal rate.

After each heartbeat, the heart quickly "recharges" for the next beat. The time it takes to recharge is called the QT interval. When this interval takes longer than it should, it changes the timing of the heartbeat and can cause an abnormal or dangerous rhythm.

What Are the Signs & Symptoms of Long QT Syndrome?

Some kids with long QT syndrome have no symptoms. Others may feel changes in their heartbeat, feel lightheaded at times, faint, or have a seizure.

Things like stress, exercise, or being startled can bring on symptoms. But sometimes symptoms can come on suddenly and without warning.

What Causes Long QT Syndrome?

Long QT syndrome can be:

  • congenital, which means it's inherited as a gene change and the baby has the condition at birth
  • acquired, which means the child develops it later. Causes include some types of medicines and electrolyte imbalances.

Congenital long QT syndrome can be treated, but it can't be "cured" and won't go away on its own. Acquired long QT syndrome usually stops if the cause (like certain medicines) goes away.

Long QT syndrome can affect people of all ages, but is sometimes more serious in children. Because congenital QT syndrome is inherited, other family members may also have it.

How Is Long QT Syndrome Diagnosed?

To diagnose long QT syndrome, doctors will ask about a child's health history and the family’s health history. They also order tests such as:

  • an ECG to check how the heart is beating
  • exercise testing (stress test)
  • sometimes, genetic testing

How Is Long QT Syndrome Treated?

Often doctors can treat long QT syndrome with medicines called beta blockers. Beta blockers help the heart beat more slowly.

Sometimes kids need a small device called a defibrillator implanted under their skin. If a child has a dangerous heart rhythm, the device can reset the heart back into a normal rhythm.

For children who have congenital long QT syndrome, treatment usually won't make the QT interval shorter. But it can lower the risk of dangerous heart rhythms and fainting.

What Else Should I Know?

Long QT syndrome can be a lifelong condition. So kids who have it will need regular checkups with a cardiologist (a doctor who treats heart problems). They should always check with their cardiologist to find out which medicines are safe to take.

By following the cardiologist's advice about medicines, diet, and exercise, most kids with long QT syndrome can stay healthy.

Some kids can play sports, but only under the careful guidance of a cardiologist. Check with your cardiologist to find out which activities your child should avoid and which ones are safe to do.

Reviewed by: Sharon M. Weinberger, MD, Priya Nigam, MD
Date Reviewed: Jan 1, 2022

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