Abstract
Background : The QT interval reflects the repolarization process of the ventricular myocardium. Berger et al presented QT variability index (QTVI) shown the lability of repolarization, and evaluated proarrhythmia in adults with the heart diseases and the prognosis. The aim was to find the standard value with the healthy children to evaluate the proarrhythmia in the healthy children with the heart diseases by using QTVI. Materials and Methods : The subjects are 120 normal children without heart disease. ECG was recorded by using MP-150. RR and QT intervals of 120 consecutive beats were measured, and calculated QTVI. Averaged QTVI of infant, first grader of elementary school and healthy students were compared. In addition, we calculated heart rate variability of 120 consecutive beats. The relation between the standardized characteristic (LF/HF, RSA/TF) and the QTVI value was examined. P < 0.05 was considered statistically significant. Results : Significant difference (p = 0.0018) was observed between the average QTVI (-1.50 ± 0.21) of first graders and that (-1.15 ± 0.39) of infants. RSA/TF that reflected the vagal nerve activity and QTVI showed a significantly negative correlation (y = -1.077–0.733 x, r = -0.412, p = 0.0015). Conclusion : The QT values of the newborn baby decreased with growth and became equal with an adult value for a first graders. The change of QTVI was suggested by the vagal nerve activity. This standard curve will be beneficial tool to evaluate proarrhythmia of children. [J Physiol Sci. 2008;58 Suppl:S188]
