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Heart Misfiring May Cause Some Cases of SIDS

Study finds first evidence for possible culprit in infant deaths

WEDNESDAY, Nov. 20, 2002 (HealthDayNews) -- A heart malfunction known to cause sudden death in young people and adults could also be responsible for some unexplained deaths in babies.

In what appears to be the first proven evidence for a possible cause for sudden infant death syndrome (SIDS), Dr. Michael J. Ackerman of the Mayo Clinic found that 5 percent of the infants he studied had genetic mutations indicating a heart condition called the long Q-T syndrome, a proven cause of sudden death in children and adults.

"All we have been able to give is theories, but now we can provide direct proof for a small but important percentage of SIDS deaths," says Ackerman, who heads the Mayo Clinic's sudden death genomics lab and long Q-T syndrome clinic. He presented his findings yesterday at the American Heart Association's scientific sessions meeting in Chicago.

Robert D. Hinnen, program director of the SIDS Center of New Jersey, which is part of Hackensack University Medical Center, echoes Ackerman's words.

"This is a very important finding. This is a relatively new area of research that we need to take into serious consideration," he says.

"We know that the Q-T syndrome has a direct link to unexplained deaths in older people, but nothing has ever been done relating Q-T to SIDS. It's a logical area of research and sheds light on areas where we've only had a dim flashlight," Hinnen adds.

In the long Q-T syndrome, the heart electronically recharges itself too slowly or in a disorganized fashion and, in children and adults, sudden activation of the adrenal system triggers the syndrome, causing cardiac arrest and sudden death.

Ackerman says that same thing could be happening to infants who get the long Q-T syndrome, which is why he and his colleagues conducted the study.

"It was logical to think that some SIDS deaths could be explained by this genetic electrical problem," he says, "and now we can provide direct proof for a small, about 5 percent, but important percentage of SIDS deaths."

According to the U.S. government's National Vital Statistics reports, there were 2,500 deaths attributed to SIDS in 2000. However, this is a 40 percent reduction in the incidence of deaths from SIDS since 1992, when the American Academy of Pediatrics first recommended that babies be put to sleep on their backs instead of stomachs.

In the study, Ackerman and his colleagues performed a genetic autopsy on 93 infants whose unexplained deaths had been investigated by the Arkansas State Crime Laboratory between 1997 and 1999. Researchers extracted DNA from frozen heart tissue and studied the five genes linked to long Q-T syndrome.

They found that approximately 5 percent of the infants in the study had genetic anomalies in those genes, compared to none of a racially matched control group of 200 infants.

What triggers the heart malfunction in infants is unknown, Ackerman says, but it could be the same activation of the adrenal system that affects children and adults, albeit on a much smaller scale.

"We really don't know. It's possible that it could be anything that could catch the heart off guard -- we call them electrical hiccups -- like a phone ringing in the baby's room, or a breath-holding spell," he says.

However, he adds that the condition affects such a small number of babies that parents should not take any special precautions.

Better to focus on prevention, he says, because there are treatments to insure that long Q-T syndrome causes no harm.

"If we know someone has long Q-T syndrome, there are things we can do. We can put them on medical treatment," he says.

Screening for the syndrome, usually done by EKG, is one option, although Ackerman says it is time-consuming and expensive.

"We have to get smarter on how to identify it," he says.

In the meantime, parents should stick to the common sense recommendations for preventing SIDS.

"Every parent can already do the time-proven things that are free and have resulted in a dramatic reduction in SIDS," he says, including making sure babies sleep on their backs, not smoking in the baby's room and not sleeping with the baby.

What To Do

For a thorough review of Sudden Infant Death Syndrome (SIDS), go to National Institute of Child Health and Human Development Also on that site are prevention tips to reduce the risk of SIDS in your baby.

SOURCES: Michael J. Ackerman, M.D., Ph.D., director, Mayo Clinic's sudden death genomics lab and long Q-T syndrome clinic, Rochester, Minn.; Robert D. Hinnen, M.S.W., program director, SIDS Center of New Jersey, Hackensack University Medical Center; Nov. 19, 2002, presentation, American Heart Association scientific sessions meeting, Chicago
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