Could a Test Predict the Risk of SIDS?

From the WebMD Archives

July 26, 2000 -- Although few things are more devastating to a family than losing a baby to sudden infant death syndrome (SIDS), experts still don't know exactly what causes the syndrome or how to prevent it. But some Italian researchers may have discovered another clue to unraveling the mystery: Some cases of SIDS, they say, may be linked to a heart rhythm problem called long-QT syndrome.

One reason this finding is important is that long-QT syndrome -- an abnormality in the heart's rhythm that usually runs in families -- can be detected by an electrocardiogram (also called EKG or ECG). Researcher Peter J. Schwartz, MD, of the University of Pavia in Italy, says he would like to see all babies screened for the heart problem, but other experts raise questions about the expense and feasibility of such widespread testing.

Nonetheless, "this is an important finding, and it adds information to what we already know about SIDS," Jeffrey Towbin, MD, tells WebMD. He says he hopes the discovery will help doctors learn more about the causes of SIDS, and ultimately prevent deaths from this mysterious disorder. Towbin is a professor of pediatric cardiology and molecular and human genetics at Baylor College of Medicine in Houston.

In a case study, published in the latest issue of TheNew England Journal of Medicine, Schwartz and colleagues report that an infant who experienced a near-SIDS episode was diagnosed with this heart problem.

The 7-week-old baby had been healthy before he was found blue, without a heartbeat, and not breathing. He was rushed to the emergency room, where doctors revived him. Once his heart began beating normally, they discovered that he had long-QT syndrome, as well as a genetic abnormality also found in people with this condition. The baby was put on medication, and five years later, his heart rhythm has improved and he has not had any further episodes.

This report is a follow-up to an earlier, 19-year study of more than 34,000 infants, in which the same researchers found in 1998 that infants who had long-QT syndrome were more likely to die from SIDS.

The 7-week-old's case helps to validate the previous work, Schwartz believes. "Maybe 25 to 30% of SIDS cases may be related to this," he says, "And what is important is that it is preventable." Schwartz is chairman of the department of cardiology at Policlinico San Matteo Istituto di Ricovero e Cura a Carattene Scientifico and the University of Pavia.

The findings have stirred debate among pediatricians and SIDS experts about whether screening all infants for the heart problem is feasible or even necessary, whether it will help reduce SIDS deaths, and whether the research evidence linking long QT with SIDS is convincing enough.

Based on his work over the past 20 years, Schwartz believes that all infants should be screened for long-QT syndrome. He points out that even if the syndrome doesn't lead to SIDS, it can cause death later in childhood.

But Michael Corwin, MD, believes it's inappropriate to perform EKGs on all newborns to screen for long-QT syndrome.

"This new article only provides an example of one case of long-QT in an infant that has a genetic basis," he tells WebMD. "And it does not in any way speak to the key issues, such as what percentage of SIDS cases may be related to long QT, and is it possible to screen infants in order to identify those who are at sufficient risk." Corwin, who was not involved in the study, is an associate professor of pediatrics at Boston University School of Medicine and team leader of data and evaluation at the National SIDS and Infant Death Program Support Center.

Whether the cost of screening every infant outweighs the potential risk is a major issue. Towbin believes it may be better to concentrate on screening infants who are at high risk of long-QT syndrome, such as those with a family history of irregular heartbeats, or those who had a very slow heart rate while still in the womb.

"Only a few babies will actually have this abnormality, and screening a million to find a few may not be as good a focus as screening a few to find a few," says Towbin, who wrote an editorial accompanying Schwartz's 1998 study in The New England Journal of Medicine. "One life lost is one too many, but you still have to do the evaluation in a way that is cost-effective --so you need a combination of what is both medically effective and cost-effective."

But the actual cost of monitoring is very low, Schwartz says. "In Europe it is $15-$20, and it may be a little more expensive in the U.S," he says. "It takes just a few moments and is a simple and non-invasive test. In my opinion, there are very few reasons not to do it. ... If I were a parent, I would not want to run the risk of long-QT syndrome. Even if it is rare, it can kill and does kill."

Also, he notes, several other screening tests are routinely performed, even for disorders for which the risk is extremely low. For example, all infants in the United States are tested for a genetic defect called phenylketonuria, which occurs in one in 100,000 babies. But with SIDS, says Schwartz, we are talking about maybe one in 2,000.

Other researchers have also been working to unravel the mystery of SIDS. One team has found that some infants who die of SIDS are unable to control their breathing while they sleep, and that this pattern may begin as early as the first week of life. These results led other researchers to investigate causes that may have begun before birth. In autopsies of infants who had died of SIDS, researchers found brain stem abnormalities, which probably formed while the baby was still in its mother's womb. These abnormalities may account for the breathing problems noted in some SIDS babies.

Unfortunately, there is no way to prevent SIDS entirely. But certain factors that may increase its likelihood have been identified. Taking precautions doesn't guarantee that a baby will be safe from SIDS, but they can reduce the risk.

Here are some ways you can cut the risk of SIDS:

  • Always place your baby to sleep on his or her back. This is perhaps the most important step to prevent SIDS, as stomach sleeping has been found to double its likelihood. The risks increase further for babies accustomed to sleeping on their backs who are accidentally put to sleep on their stomachs.
  • Avoid soft mattresses, pillows, waterbeds and beanbag furniture. Use a firm mattress in a safety-approved crib.
  • Keep the baby's sleeping area clear of clutter, including stuffed toys and soft bedding.
  • Avoid smoking during pregnancy. Keep your baby's environment as smoke-free as possible.
  • Keep the baby's room at a comfortable temperature. Avoid overheating, as well as wrapping the baby in too many blankets or in heavy sleepwear.
  • Bed sharing has not been found to protect against SIDS, according the American Academy of Pediatrics, and, under some conditions, can be hazardous to the baby's health.