BACKGROUND: Accurate determination of the QTc interval in children is important especially when using drugs which can prolong cardiac repolarization. Previous work suggests the most appropriate correction formula to be QTc = QT/RR(0.38) . We set out to compute the best population-derived age and gender-related QT correction formula factor in normal children.
METHODS: We evaluated a cohort of 1400 healthy children. From a resting 12-lead electrocardiogram, QT and RR intervals were measured. Subjects were divided into four age and gender groups: 0-1 years (n = 540); 1-5 years (n = 281); 5-10 years (n = 277), and > 10 years (n = 302). QT/RR intervals were plotted and fitted with two regression analyses, linear regression obtaining constant α (QTc = QT + α x (1-RR)), and log-linear analysis deriving constant β (QTc = QT/RR(β) ). Furthermore, regression analysis of QTc/RR for the two formulas was performed obtaining slope and R(2) .
RESULTS: Correction constant α decreased steadily with increasing age, genders remained on par until 10 years of age followed by more pronounced decrease in females (range 0.24-0.18). The β constant showed a similar trend however with more pronounced decline (range 0.45-0.31). Regression slopes of QTc/RR plots (all ages and both genders) were close to zero (both formulas).
CONCLUSION: For the full range of pediatric subjects, the optimum population-based correction factors α and β decreased with increasing age and gender, digressing more so in adolescent girls. More specific correction factors, based on age and gender, are necessary in QT correction.
- Age Factors
- Child, Preschool
- Cohort Studies
- Heart Rate
- Infant, Newborn
- Prospective Studies
- Reproducibility of Results
- Sex Factors