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Prolonged QT Interval and SIDS Findings Released

The Sudden Infant Death Syndrome Alliance 1314 Bedford Avenue
Suite 210
Baltimore, MD 21208
410-653-8226 voice
800-221-7437 voice
410-653-8709 fax

TO: Affiliate Presidents and Executive Directors
FROM: Phipps Cohe, National Public Affairs Director
DATE: 6/10/98
RE: Prolonged QT Interval and SIDS Findings Released

Serious consideration should be given to an Italian study entitled "Prolongation of the QT Interval and the Sudden Infant Death Syndrome," appearing in the June 11, 1998 edition of the New England Journal of Medicine. The long QT syndrome is characterized by a delay in repolarization--an important electrical process of the heart. In older children and adults, the long QT syndrome is a cardiac disorder which can produce fainting spells, seizures, and sudden death.

In this study, lead investigator Peter Schwartz et. al. report a strong association between prolongation of the QT interval in the first week of life and SIDS. This significant finding is based on electrocardiograms administered to 34,442 newborns on the third or fourth day of life beginning in 1976 and continuing through 1994. The newborns were followed prospectively for one year. One-year follow-up data were available for 33,034 of the infants.

During the one year of follow-up, there were 34 deaths: 24 due to SIDS and 10 due to other causes. The infants who died of SIDS had a longer corrected QT interval (QTc) than did the survivors and the infants who died from causes other than SIDS. The SIDS victims had no family history of long QT syndrome.

According to the study, inability to shorten the QT interval during increases in heart rate may be involved in SIDS. Such increases in newborn heart rate may be caused by a number of conditions, including sudden noise, exposure to cold, rapid eye movement sleep, apnea, and arousal.

The study suggests that the possible mechanism behind a long QT interval finding in SIDS infants may be developmental or genetic in origin, but is not yet known. We do not even know if the long QT interval is causing the deaths of these babies, as it does in older people--or whether it is a marker for something that is happening in the body, for example, in the nervous system. The fact that many infants in the study with prolonged QT intervals did not die of SIDS also indicates that other factors in the postnatal period contribute to the lethal event.

While further research is needed to confirm the results, publication of this study reopens an intriguing avenue for SIDS investigation, and contributes to the definition of normal electrocardiographic standards for newborns. It also suggests a potential screening tool for future diagnosis. It is premature, however, to propose that all newborns have a routine electrocardiogram for measurement of long QT.

Current indications include infants with a family history of long QT or those who have had a life-threatening event. Newborn EKGs require the expert administration and evaluation of a highly skilled pediatric cardiologist. The question of what a physician should do in the case of an infant who tests positive is as yet an unanswered one.

The current findings in no way diminish or challenge the "Back To Sleep" advisories that have become accepted parental and child care practice. Stomach sleeping has been clearly identified as a risk factor for SIDS. This study may have some significance with respect to our understanding of a percentage of infants at risk for SIDS for whom the current recommendations are having no effect.

In the meantime, parents and everyone who cares for an infant are reminded to position their infants on the back to sleep, avoid soft bedding for infant sleep, provide a smoke-free environment for infants, and maintain a regular schedule of immunizations and check-ups.


1.) While it is meaningful to study research topics such as long QT, it is important to keep in mind that the cause(s) of SIDS remain unknown. Prolonged QT has not yet been established as a risk factor. However, the association of long QT to SIDS presented by this study has stirred interest in further research of this topic.

2.) It is premature to view electrocardiograms as a screen or predictor for SIDS. There is currently no test available to determine which infants are at risk.

3.) Meanwhile, the SIDS Alliance continues to advise parents--and everyone who cares for an infant--to position babies on their backs for sleep; provide a smoke-free environment; use firm bedding; avoid overheating; and maintain regular check-ups and immunization schedules to reduce the risk of Sudden Infant Death Syndrome.

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