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Prolongation of the QT interval has been implicated in the pathogenesis of the Sudden Infant Death Syndrome (SIDS). To test this hypothesis, 31 studies in 12 normal infants and 17 studies in 7 aborted SIDS infants were performed during sleep in the first four months of life. The QT index (QTc) was measured with an accuracy of 2 msec or better. In contrast to recent suggestions, the mean QTc was significantly smaller in the aborted SIDS than in the normal infants in both REM and quiet sleep (p< 0.05, unpaired t-test). Means ± SD are presented:

In both the normal and aborted SIDS infants, the mean QTc was significantly smaller in REM than in quiet sleep (p< 0.01, paired t-test). We suggest that 1) the smaller QTc in the aborted SIDS infants results from a uniform increase in the activity of the sympathetic outflow to the ventricles or an increase in circulating levels of catecholamines and 2) the smaller QTc in REM in both groups makes it unlikely that there is an imbalance in the sympathetic innervation of the ventricles in aborted SIDS. Although these studies do not support the hypothesis relating SIDS to prolongation of the QT interval, they may provide a basis for distinguishing normal from aborted SIDS infants.

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Haddad, G., Epstein, M., Epstein, R. et al. 972 THE QT INTERVAL IN ABORTED SIDS INFANTS. Pediatr Res 12, 526 (1978) doi:10.1203/00006450-197804001-00978

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