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Prolongation of the QT interval and the sudden infant death syndrome
P J Schwartz1, M Stramba-Badiale, A Segantini
1Department of Cardiology, Policlinico San Matteo Istituto di Ricovero e Cura a Carattene Scientifico, University of Pavia, Italy.
Insights
Prolonged QT interval in newborns is linked to sudden infant death syndrome (SIDS). Early electrocardiogram screening may identify at-risk infants for preventive measures.
Area of Science:
- Cardiology
- Neonatal Medicine
- Pediatric Pathology
Background:
- Sudden infant death syndrome (SIDS) is a multifactorial condition with unknown causes.
- A prolonged QT interval, potentially due to abnormal cardiac sympathetic innervation, may increase the risk of fatal arrhythmias.
- This study prospectively tested the hypothesis linking QT interval prolongation to SIDS risk.
Purpose of the Study:
- To investigate the association between QT interval prolongation in newborns and the risk of SIDS.
- To determine if neonatal electrocardiographic screening can identify infants at risk for SIDS.
Main Methods:
- Electrocardiograms were recorded in 34,442 newborns within the first week of life.
- Infants were prospectively followed for one year to track mortality, including SIDS.
- QT intervals were analyzed with and without heart rate correction (QTc).
Main Results:
- Infants who died of SIDS had significantly longer corrected QT intervals (QTc) than survivors.
- A prolonged QTc (greater than 440 msec) was observed in 12 of 24 SIDS victims, but none of the other infants.
- The odds ratio for SIDS in infants with a prolonged QTc was 41.3.
Conclusions:
- Prolongation of the QT interval in the neonatal period is strongly associated with SIDS.
- Neonatal electrocardiographic screening could identify a significant percentage of infants at risk for SIDS.
- Early identification may enable the implementation of preventive strategies for SIDS.
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.