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Symptoms of Long QT Syndrome

Children with long QT syndrome (LQTS) do not have symptoms unless they develop an arrhythmia. If their heart does begin beating too fast, they might faint because their brain isn’t getting enough blood. First they might feel fluttering in their chest.

Sometimes a fainting spell is mistaken for a seizure or it seems like a response to stress, or a child nearly drowns or does drown because they fainted while swimming.

It’s important to have a health care provider check your child if they faint, have a seizure or nearly drown and there’s no clear reason. They should also be checked if you already know they have LQTS or if there are other family members with LQTS.

The heart of someone with LQTS can suddenly stop beating, a condition called sudden cardiac arrest. This may be the first sign of LQTS. Sudden cardiac arrest usually causes death. However, some children who receive treatment quickly, within minutes, can survive.

Long QT Syndrome Diagnosis

To diagnose this condition, your doctor will examine your child and use a stethoscope to listen to their heart.

The doctor will ask for details about any symptoms your child has, their health history and your family health history.

Your child will also need an electrocardiogram (ECG) test, which provides information about how their heart works.

Using an ECG, a health care provider can examine the electrical signal in your child’s heart. The signal produces a pattern. Providers name different parts of the patterns with the letters P, Q, R, S and T. The QT interval is the time from when the ventricles start to squeeze until they are relaxed and ready to squeeze again.

A provider can measure this time and know if it takes longer than normal. If it takes longer, it's called a prolonged QT interval. A child with a prolonged QT interval may have long QT syndrome.

Some children with LQTS do not have a prolonged QT interval all the time. So an ECG with not always detect it. To find out enough about the electrical signal in your child’s heart, your child may need to wear a portable ECG device, called a Holter monitor. This device can record their heart’s activity for 24 hours.

You child may also need an exercise stress test. This means we monitor their heart rate and rhythm while they exercise.

The doctor may suggest doing genetic testing to see if genes play a role in your child’s condition. If they do, then others in the family may need to be tested to see if they might be affected.

Who Treats This at Seattle Children's?

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Summer 2014: Good Growing Newsletter

In This Issue

  • Understanding the Power and Influence of Role Models
  • Legal Marijuana Means Greater Poisoning Risks for Children
  • Why Choose Pediatric Emergency Care?

Download Summer 2014 (PDF)