Abstract
In patients with atrial septal defect (ASD), increased pulmonary blood flow by left-to-right shunting suppresses the respiratory vagal input to the heart and reduces the change in RR interval. We investigated the effect of increased shunt volume on the QT/RR relation and QT interval variability to mean the repolarization lability.The subjects were 32 patients with ASD. ECG was performed concurrent with echocardiography and the QT and RR intervals were determined. The QT/RR relation of 120 consecutive heart beats. In Doppler echocardiography, the pulmonary-to-systemic blood flow ratio was determined and the subjects were classified into the high- (2.0 or more) and low-shunt (less than 2.0) groups. In QT/RR linear regression and QT variability index (QTvi) were compared between the high- and low-shunt groups. Unpaired t-test for significance test was used.In the two groups, the high-shunt group exhibited a tendency toward variance, compared with the low-shunt group (p=0.007). In addition, QTvi were -0.856±0.632 and -0.091±0.718 in the low and high-shunt groups, respectively (p=0.0002).In ASD patients, reduced respiratory vagal input that was induced by an increased left-to-right shunt enhanced the QT/RR variance and increased QTvi. [J Physiol Sci. 2007;57 Suppl:S117]