The corrected QT interval in 24 h ECGs in neonates.

BACKGROUND

A prolongation of the corrected QT interval (QTc) in the routine ECG of otherwise healthy neonates has been suspected to be a risk factor for sudden infant death. None of the studies published so far differentiated between awake and sleeping neonates.

OBJECTIVE

This study was designed to find possible differences of the QTc when neonates were asleep or awake, and to provide guide values for neonatal QTc in 24-h ECGs.

METHODS

Hundred neonates (51 male, 49 female, age 2-11 days) underwent ambulatory ECG with defined lead positions. The QT interval was measured constantly in three different leads, and the corrected QT interval was calculated using Bazett's formula. We compared the QTc obtained during sleep with the QTc obtained from wake periods.

RESULTS

The heart rate was significantly higher when the neonates were awake, and when awake higher in girls than in boys. While there was no statistically significant difference between the QTc when the babies were awake or asleep in leads 1 and 3, this reached the level of mathematical significance in the most cranio-caudal lead 2.

CONCLUSION

Changes of the corrected QT interval in neonates seems to be dependent on the lead position of ambulatory ECGs, and could be found only in one lead. Guide values for the sleeping and awake neonate are provided.