Changes of the corrected QT interval in healthy boys and girls over day and night.

Abstract

The study was designed to detect changes in corrected QT intervals over day and night in both sexes in healthy children. The corrected QT interval was calculated from 24 h ECGs obtained from 282 healthy children aged 6 months to 18 years. The QTc interval as measured by the 24 h recording differs to the standard ECG measurement which is in average of 40-50 ms shorter. The QTc interval changes little over a 24 h period and is remarkably constant despite significant heart rate changes in healthy children. The routine ECG-even if the calculated values differ markedly from those obtained over 24 h-seems to be a good screening method for the measurement of corrected QT intervals, because the corrected QT interval is kept constant over the whole day in healthy children.