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Measures of cardiac repolarization and body position in infants
Sherri S Baker1, Angelo S Milazzo, Anne Marie Valente
1Division of Cardiology, Duke University Medical Center, Durham, NC 27710, USA.
Insights
This study found no significant difference in the QTc interval or QT dispersion between infants sleeping in supine versus prone positions. These findings suggest prolonged QTc interval is unlikely to explain the increased risk of Sudden Infant Death Syndrome (SIDS) associated with prone sleeping.
Area of Science:
- Cardiology
- Pediatrics
- Sudden Infant Death Syndrome (SIDS) Research
Background:
- Sudden Infant Death Syndrome (SIDS) is a leading cause of post-neonatal infant mortality.
- A prolonged QTc interval on electrocardiogram (ECG) has been linked to SIDS.
- Prone sleeping position is a known risk factor for SIDS, leading to campaigns like 'Back to Sleep'.
Purpose of the Study:
- To investigate whether infant body position (supine vs. prone) affects the QTc interval and QT dispersion.
- To explore a potential link between body position, QTc interval changes, and SIDS risk.
Main Methods:
- Electrocardiograms (ECGs) were recorded from 45 healthy infants in both supine and prone positions while asleep.
- Measurements included average QTc interval (Bazett's correction) and QT dispersion.
- ECGs were analyzed by blinded investigators.
Main Results:
- No statistically significant difference was found in the average QTc interval between the supine (403 ± 20 msec) and prone (405 ± 27 msec) positions.
- No significant difference was observed in QT dispersion between the two positions (supine: 20 ± 12 msec; prone: 22 ± 13 msec).
- One infant who died of SIDS showed differing QTc intervals between positions, but this was an isolated case.
Conclusions:
- In healthy, resting infants, body position does not appear to alter the QTc interval or QT dispersion.
- The increased SIDS risk associated with prone sleeping is unlikely to be explained by QTc interval prolongation in the general infant population.
- Further research may be needed for infants with pre-existing long QT syndrome.
Abstract:
Sudden Infant Death Syndrome (SIDS) is the most common cause of death in children between 1 and 6 months of age. Recent data suggest that a prolonged QTc interval on the 12-lead electrocardiogram (ECG) is associated with SIDS. Prone body position during sleep is also known to be a risk factor for SIDS; this has prompted the American Academy of Pediatrics to promote the "Back to Sleep" campaign. We postulated that the QTc interval in infants might change as a function of body position, linking the observations relating body position and QTc interval to SIDS. We recorded ECGs in a group of infants in both the supine and prone position to determine if the QTc interval and QT dispersion differ between the 2 positions. Forty-seven standard 12-lead EGGs and high-amplitude, rapid-sweep 12-lead EGGs were performed on 45 healthy infants (mean age 26 +/- 40 days) in both the supine and prone positions. The infants were asleep in a quiet, restful state. The ECGs were reviewed by 2 investigators blinded to the position of the infants during recording. Measurements included the average QTc interval (using Bazett's correction) and QT dispersion (the difference between the longest and the shortest QT intervals on a standard 12-lead EKG). The study was designed to detect a 3% difference in QTc interval with 80% power and alpha = 0.05. All subjects had telephone or clinical follow-up at 1 year. The average QTc interval was 403 +/- 20 milliseconds (msec) in the supine position and 405 +/- 27 msec in the prone position (p = NS). The QT dispersion was 20 +/- 12 msec in the supine position and 22 +/- 13 msec in the prone position (p = NS). One infant in the study group died of SIDS at the age of 3 months. The EGG of this patient revealed a QTc interval of 382 msec in the supine position and 407 msec in the prone position; the QT dispersion was 34 msec in the supine position and 34 msec in the prone position. We found no difference in QTc interval or QT dispersion as a function of body position in healthy infants resting quietly. Prolongation of the QTc interval is unlikely to explain the increased risk for SIDS associated with prone body position in the general population of healthy infants, unless patients with long QT syndrome are somehow more influenced by body position than normal patients are.