A 45-month-old boy who had complex cardiac anomalies with interrupted inferior vena cava and polysplenia underwent extracardiac Fontan operation. He redeveloped deep cyanosis postoperatively. Cardiac catheterization showed a preferential flow of the hepatic venous blood to the right lung and arteriovenous malformations (PAVMs) in the left lung. He underwent revision of the conduit to attain balanced hepatic venous drainage with subsequent regression of the PAVMs and disappearance of cyanosis. Our experience shows that deficiency of hepatic venous flow played a crucial role in the development of PAVMs and that redistribution of the flow retained potential to ameliorate the pathological condition.