Who Is At Risk for Long QT Syndrome?

Populations Affected

Long QT syndrome (LQTS) is a rare condition. Experts suspect 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 with LQTS experience their first irregular heartbeat by the time they're 12 years old, and 90 percent by the time they reach 40 years old. Rarely is inherited LQTS first diagnosed in someone after age 40. In boys with LQTS, the QT interval often returns toward normal after puberty, and the risk of fainting and sudden cardiac arrest decreases.

LQTS is more common in women than men. Women who have LQTS are more likely to experience fainting or sudden death from the condition during menstruation and shortly after giving birth. LQTS also is common in children born deaf. This is because the same genetic abnormality that affects hearing also affects the working 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 (on your EKG) longer. Your doctor can tell you whether the 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 disorder anorexia nervosa and certain thyroid disorders.