Beat-to-beat QT interval variability in children: Normal and physiologic data

Background: QT interval variability provides information on ventricular vulnerability. However, QT interval variability in children has not been adequately evaluated. Methods: One hundred seventy-three consecutive nursing infants and children (male-female, 106:67) up to school age with no intrinsic cardiac disease were included in this study, and they were categorized into 6 age-related groups. The QT variability index (QTVI) was calculated based on an electrocardiogram; and age-specific standard values, sex-specific classification, and a standard growth curve covering 0 to 7 years were constructed. Results: The QTVI decreased in an age-dependent manner, reached constant values after school age, and exhibited no sex-specific differences in 6 age-related groups. Conclusions: Based on the age-dependent standardized QTVI values, it is possible to estimate the instability of ventricular repolarization in pediatric patients with better accuracy.