Who Is At Risk for Long QT Syndrome?

Long QT syndrome (LQTS) is a rare condition. 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 death in children is rare. But when it does 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 heartbeat by the time they're 12 years old, and 90 percent by the time they're 40 years old. The condition rarely is diagnosed in someone after age 40.

In boys who have LQTS, the QT interval (on the EKG) often returns toward normal after puberty. If this happens, the risk for LQTS symptoms and complications decreases.

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

LQTS also is common in children who are born deaf. 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 for having LQTS if anyone in your family has ever had it. Unexplained fainting or seizures, drowning or near drowning, or 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 prescription or over-the-counter medicines you take 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 and certain thyroid disorders.