抄録
The QT interval indicates the repolarization process of myocardium, and is considerably affected by the preceding sinus cycle (RR interval). Since excessively prolonged QT intervals may contribute to the initiation of lethal cardiac arrhythmia, the lability of repolarization in adults can be evaluated using the variability index (QTvi). On the other hand, no reports have been available regarding QTvi in newborn babies and preschool children. Thus, QTvi has been anticipated to indicate the changes accompanied with postnatal growth, based on the characteristics of the immature autonomic nervous system and myocardium of such young children.Electrocardiograms were recorded at rest in a total of 60 healthy children aged 0 days to 6 years. RR and QT intervals of 120 consecutive heart beats were measured to calculate QTvi.A tendency towards a decrease in QTvi was observed in children aged from 0 days to 7 years (linear regression line: y = -1.076x + 0.007, r = -0.464). Significant difference (p=0.0021) was observed between the average QTvi (-1.57 ± 0.11) of preschool children (average age: 6.3 ± 0.5 years) and that (-1.19 ± 0.29) of neonates (average month: 7.0 ± 4.1 months).It was suggested that repolarization time would change along with the sinus cycle during postnatal growth, resulting in a reduction of lability of repolarization. [J Physiol Sci. 2007;57 Suppl:S177]
