QT Correction Methods in Infants and Children: Effects of Age and Gender

BackgroundAccurate 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/RR0.38. We set out to compute the best population-derived age and gender-related QT correction formula factor in normal children. MethodsWe 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 (QTc = QT + x (1-RR)), and log-linear analysis deriving constant (QTc = QT/RR). Furthermore, regression analysis of QTc/RR for the two formulas was performed obtaining slope and R-2. ResultsCorrection constant 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 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). ConclusionFor the full range of pediatric subjects, the optimum population-based correction factors and 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.