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Who Is at Risk for Long QT Syndrome?

Long QT syndrome (LQTS) is a rare disorder. Experts think that about 1 in 7,000 people has LQTS. But no one knows for sure, because LQTS often goes undiagnosed.

LQTS causes about 3,000 to 4,000 sudden deaths in children and young adults each year in the United States. Unexplained sudden deaths in children are rare. When they do occur, LQTS often is the cause.

Inherited LQTS usually is first detected during childhood or young adulthood. Half of all people who have LQTS have their first abnormal heart rhythm by the time they're 12 years old, and 90 percent by the time they're 40 years old. The condition rarely is diagnosed after age 40.

In boys who have LQTS, the QT interval (which can be seen on an EKG test) often returns toward normal after puberty. If this happens, the risk of LQTS symptoms and complications goes down.

LQTS is more common in women than men. Women who have LQTS are more likely to faint or die suddenly from the disorder during menstruation and shortly after giving birth.

Children who are born deaf also are at increased risk for LQTS. This is because the same genetic problem that affects hearing also affects the function of ion channels in the heart.

Major Risk Factors

You're at risk of having LQTS if anyone in your family has ever had it. Unexplained fainting or seizures, drowning or near drowning, and unexplained sudden death are all possible signs of LQTS.

You're also at risk for LQTS if you take medicines that make the QT interval longer. Your doctor can tell you whether your prescription or over-the-counter medicines might do this.

You also may develop LQTS if you have excessive vomiting or diarrhea or other conditions that cause low blood levels of potassium or sodium. These conditions include the eating disorders anorexia nervosa and bulimia, as well as some thyroid disorders.

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September 21, 2011 Last Updated Icon

The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.