View source for Prolongation of the QT interval and the sudden infant death syndrome

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Schwartz PJ, Stramba-Badiale M, Segantini A, Austoni P, Bosi G, Giorgetti R, Grancini F, Marni ED, Perticone F, Rosti D et al. (1998) Prolongation of the QT interval and the sudden infant death syndrome. N Engl J Med 338:24 1709–14.

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http://www.nejm.org/doi/pdf/10.1056/NEJM199806113382401

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BACKGROUND: The sudden infant death syndrome (SIDS) is multifactorial in origin, but its causes remain unknown. We previously proposed that prolongation of the QT interval on the electrocardiogram, possibly resulting from a developmental abnormality in cardiac sympathetic innervation, may increase the risk of life-threatening ventricular arrhythmias and contribute to this devastating disorder. We prospectively tested this hypothesis. METHODS: Between 1976 and 1994, we recorded electrocardiograms on the third or fourth day of life in 34,442 newborns and followed them prospectively for one year. The QT interval was analyzed with and without correction for the heart rate. RESULTS: One-year follow-up data were available for 33,034 of the infants. There were 34 deaths, of which 24 were due to SIDS. The infants who died of SIDS had a longer corrected QT interval (QTc) than did the survivors (mean [+/-SD], 435+/-45 vs. 400+/-20 msec, P<0.01) and the infants who died from causes other than SIDS (393+/-24 msec, P<0.05). Moreover, 12 of the 24 SIDS victims but none of the other infants had a prolonged QTc (defined as a QTc greater than 440 msec). When the absolute QT interval was determined for similar cardiac-cycle lengths, it was found that 12 of the 24 infants who died of SIDS had a QT value exceeding the 97.5th percentile for the study group as a whole. The odds ratio for SIDS in infants with a prolonged QTc was 41.3 (95 percent confidence interval, 17.3 to 98.4). CONCLUSIONS: Prolongation of the QT interval in the first week of life is strongly associated with SIDS. Neonatal electrocardiographic screening may permit the early identification of a substantial percentage of infants at risk for SIDS, and the institution of preventive measures may therefore be possible.

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*Retrospective study using EKGs recorded at day 3 or 4 of life in more than 34,000 infants over 18 years, with data from follow-up 1 year later available for more than 33,000. The average corrected QT interval among the 24 infants who died of SIDS was longer than the average for surviving infants. (Surprisingly, the 10 infants who died of causes other than SIDS had a signifcantly lower mean corrected QT interval than did survivors, with a relatively small standard deviation suggesting the effect was not due to one or two outliers.) For further discussion of QT intervals see annotation at Aurlien et al.

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