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

Area of Science:

• Pediatric Cardiology
• Electrophysiology
• Clinical Pediatrics

Background:

• The corrected QT interval (QTc) is a crucial measure of cardiac repolarization.
• Understanding diurnal variations in QTc is important for pediatric cardiac health assessment.

Purpose of the Study:

• To evaluate day and night changes in corrected QT intervals in healthy children.
• To compare QTc measurements from 24-hour Holter monitoring with standard ECGs.

Main Methods:

• Analysis of 24-hour ECG recordings from 282 healthy children (6 months to 18 years).
• Calculation of the corrected QT interval (QTc) using standard formulas.
• Comparison of QTc values obtained from prolonged recordings versus single-lead ECGs.

Main Results:

• The QTc interval measured via 24-hour ECGs was approximately 40-50 ms longer than standard ECG measurements.
• The QTc interval demonstrated minimal variation over a 24-hour period in healthy children.
• QTc remained constant despite significant fluctuations in heart rate.

Conclusions:

• The corrected QT interval is remarkably stable throughout the day in healthy children.
• Routine ECGs appear adequate for screening QTc interval abnormalities, despite quantitative differences from 24-hour recordings.
• This stability supports the use of standard ECGs for initial QTc assessment in pediatric populations.