QT dispersion in healthy Chinese children and adolescents

Abstract

Background: QT dispersion (QT(d)) reflects the interlead difference in QT interval. It may provide a measure of repolarization inhomogeneity. Studies on QT(d) mainly involve adults, while QT(d) in children are less well studied. The aim of this study was to evaluate QT(d) in healthy children and assess the relationship of gender, age, and anthropometric parameters, viz. weight (W), height (H), body mass index (BMI), and body surface area (BSA) to QT(d). Methods: Five hundred and one Chinese children and adolescents (243 boys, 258 girls) with no history of cardiovascular diseases were studied. Their ages ranged from 6.3 to 17.5 years. Surface 12-lead electrocardiograms were measured in each child at rest. QT and R-R intervals in each of the 12 leads were manually measured at a magnification of 2X. QT was corrected to QT(c) according to Bazett's formula. QT(d) was calculated as the difference between the maximum and minimum QT of the measured leads, while corrected QT(d) (QT(cd)) was the difference between the maximum and minimum QT(c) of the measured leads. Adjusted QT(cd) was QT(cd) divided by the square root of the number of measurable leads. Results: Mean QT(d) of all subjects was 34 ms (95% CI 33.6-35.1 ms). Mean QT(d) for boys and girls was 35 ms and 34 ms, respectively (P = 0.18). Mean QT(cd) for the whole group was 47 ms (95% CI 45.8-48.2 ms), while mean adjusted QT(cd) was 14 ms (95% CI 13.8-14.5 ms). There were no significant gender differences in QT(cd) or adjusted QT(cd). Weak negative correlation existed between age and QT(d), QT(cd) and adjusted QT(cd) (r = -0.22, r = -0.26, r = -0.21, respectively, P < 0.001). Similarly, QT(cd) also had a weak significant negative correlation with W (r = -0.20), H (r = -0.21) and BSA (r = -0.22), P < 0.001. However, multiple stepwise regression analysis revealed that only age was significantly related to QT(cd) (R2 = 0.066) and QT(d) (R2 = 0.059), P < 0.001. Conclusions: The results of this study indicate a trend of decreasing QT(d) and QT(cd) with increasing age, supported by multiple regression analysis. However indices of QT(d) in children are not influenced by anthropometry. This information may be useful for the clinical application of QT(d) in children.