Background : This study investigated changes in left ventricular(LV) systolic function geometry after corrective surgery of ventricular septal defect(VSD) or closure of patent ductus arteriosus(PDA) with Amplazer ductal occluder. . Methods : We performed echocardiography before and after closure in large VSD(Group A, n=9) , small VSD (Group B, n=9) and large PDA (Group C, n=10). M-mode measurements were made form short axis parasternal images of LV. Mixes venous saturation , lactate and troponin I were measured postoperatively and the other ICU records were reviewed in Group A and B. Results : Ejection fraction(EF) and fractional shortening(FS) were decreased after volume unloading procedure in Group A and C(p=0.008,P=0.008). LV wall thickness and LV wall thickness/ enddiastolic dimension (EDD) ratio (as an estimate of mass/volume ratio) were increased in Group A after procedure (p=0.011,P=0.011). In group B, none did not changed significantly. Recovery time of systolic dysfunction was mean 3 days and mean 13 months in Group A and C, respectively. Immediately after procedure, decrease in LV endsystolic dimension(P=0.05, P=0.028) was significant but LV EDD did not changed significantly. EF or FS level did not correlated to Troponin I level. Conclusions :, There were significant dysfunction of LV and LV mass/volume ratio was increased after volume unloading procedure. The severity of dysfunction was not associated with myocardial injury of cardiopulmonary bypass. A recovery time may depends on age. Therefore close observation and management are needed immediately after volume reduction procedure.