The implications of a relationship between prolonged QT interval and the sudden infant death syndrome.

Abstract

* Abbreviations: SIDS = : sudden infant death syndrome • ECG = : electrocardiogram • LQTS = : long QT syndrome We read with interest the article on the proposed association of prolonged QT interval and the sudden infant death syndrome (SIDS) by Schwartz et al.1 Recognizing the previous failures to determine cause(s) for SIDS and the risks of changing practice in response to one study, we wish to take this opportunity to place the findings of the study in perspective and reflect on directions that might be pursued. Although the mechanism for SIDS (the most common cause of death from 1 month to 1 year of age) remains unknown, certain factors, such as smoking during pregnancy and sleep position of the infant lter the risk of SIDS.2–7 The hypothesis that there is a relationship between SIDS and prolonged QT has been previously raised by Schwartz8 and other authors,9–12 and disputed by some,13–15 but the recent data by Schwartz et al1 are the most compelling to date. Schwartz et al obtained electrocardiogram (ECG) recordings 3 to 4 days after birth in 34 443 newborn infants, 24 of whom died within the first year after birth with a diagnosis of SIDS. The authors found that these 24 infants had an average QT interval (corrected for heart rate) that was longer than in 9725 randomly selected living infants and longer than in 10 infants who died of other causes. Accordingly, this report raises several important questions. What is the cause of the long QT interval in the infants? Schwartz et al1 suggest that the prolonged QT might be caused by: a) different rates of development of the right and left sympathetic nerves rendering the infant susceptible to an arrhythmia during sudden increases in sympathetic activity8 ,16 ,17; or b) mutation in one of the genes encoding sodium or potassium channels, as has been identified … Address correspondence to George Lister, MD, Department of Pediatrics, Yale University School of Medicine, 333 Cedar St, PO Box 208064, New Haven, CT 06520-8064.