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Heart Disorder With a Genetic Component

Diagnosis * Long QT Syndrome, which can cause sudden death, requires an EKG test for all family members.

November 06, 2000|RIDGELY OCHS | NEWSDAY

His youngest son had several seizures at age 4, said Bruce of Smithtown, N.Y. All the tests came back normal, but the neurologist treated him for epilepsy.

About two years ago, his son, then 6, was in the deep end of the pool, where he took an abnormally long time resurfacing, said his father, who asked that his last name not be used.

When he came up, his son was crying and told his parents he had been "dreaming" under the water, which they interpreted as a fainting spell. Last year, as he was completing a gym class test, he passed out again. Stumped, the neurologist sent the boy to a pediatric cardiologist. "Rule out Long QT Syndrome," Bruce said the neurologist's order read.

When the cardiologist did an electrocardiogram, to measure the electrical activity of his son's heart, she said, "Oh, my God; get the rest of the family in here tomorrow," Bruce recalled.

All three of his children, his wife and her father were diagnosed with Long QT Syndrome, a disorder of the electrical system of the heart that can cause sudden death. Although not curable, the syndrome, if detected, can be treated.

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An inherited abnormality, Long QT Syndrome occurs in an estimated 1 in 5,000 people, making it "fairly common for a genetic disease," according to Jeffrey Towbin, professor of pediatric and molecular and human genetics at Baylor College of Medicine in Houston. Towbin said that estimate may be low because it very often goes undetected.

It also kills about 3,000 yearly, most of them children and young adults, according to the Sudden Arrhythmia Deaths Syndromes Foundation, a nonprofit group based in Salt Lake City. In one large study of Italian newborns published in 1998 in the New England Journal of Medicine, half of the babies who died of sudden infant death syndrome were found to have long QT intervals, meaning they had the syndrome.

Loss of consciousness, unexplained seizures or sudden death are the most common indicators, usually occurring during physical exertion or emotional excitement--although some forms of Long QT are triggered by loud noises or can occur in sleep. And about one-third of those with the syndrome never have symptoms.

After each heartbeat, the heart's electrical system repolarizes, or recharges. The QT interval is a measure of that time. Most people born with Long QT Syndrome show an unusually long QT interval on an EKG. This makes them vulnerable to a fast, abnormal heart rhythm, or arrhythmia. When this happens, no blood is pumped from the heart; the brain is in turn deprived of blood, leading to loss of consciousness or sudden death.

So far, mutations of six different genes have been identified as causing the syndrome, although more may be involved, Towbin said. If a mother or father has one of these mutations, a child has a 50% chance of inheriting it.

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One of the problems diagnosing the syndrome is that "a lot of physicians don't know about it," said Dr. Devyani Chowdhury, a pediatric cardiologist at Schneider Children's Hospital in New Hyde Park, N.Y. A child like Bruce's who has fainting spells is often treated for seizures without the underlying cause ever being detected, said Chowdhury, who diagnosed the young boy, his siblings and his mother.

"He could have easily died," she said. "That's what usually happens."

Chowdhury and Towbin said anyone in a family with a close blood relative who suddenly died for no apparent reason--especially at a young age or of SIDS--should be evaluated with an EKG for the syndrome. Similarly, someone with a history of fainting spells or unexplained seizures or who comes from a family where either is common should be given an EKG, Chowdhury said.

But Towbin and Chowdhury stopped short of calling for all children to get EKGs.

For more information, contact the Sudden Arrhythmia Death Syndromes Foundation at (800) 786-7723 or at http://www.sads.org.

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