Abstract
Objectives: Decreased heart rate variability (HRV) has been demonstrated in children with atrial septal defect (ASD). It has been reported that myocardial damage decreased HRV, increased lability in repolarization, and induced proarrhythmia. In this study, we examined whether increased left-to-right shunt would affect repolarization in ASD. Subjects and Methods: Thirty-four patients without heart failure were employed. QT variability (QTVI) was calculated using a linear regression based on the QT time at 120 beats and precedent RR. Left-to-right shunt ratio was determined by Doppler ultrasound to categorize patients into the high- (2.0 or more) and low-shunt (less than 2.0) groups. In addition, power of low, high, total, and respiratory frequency domains were determined by HRV, a QT/RR linear regression was drawn and the correlations between QTVI and power value examined in both groups. Results: Linear regression of the high-shunt group was distributed more broadly than that of the low-shunt group (p=0.0004). By contrast, QTVI was -1.29±0.32 in the low and -0.51±0.37 in the high (p<0.0001). Log10 RSA and QTVI showed a significant negative correlation (p<0.0001). Conclusion: Lability in repolarization was significantly increased in the high-shunt group, even in children without organic myocardial failure. This finding may derive from decreased vagal nerve activity. QTVI is assumed to reflect the input from the autonomic nerve to the heart, as well as HRV. [J Physiol Sci. 2008;58 Suppl:S188]
