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.
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.
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).