Total anomalous pulmonary venous return.

TAPVR typically presents in early infancy due to excessive pulmonary blood flow and mild cyanosis. Presentation is earlier when there is obstruction to pulmonary venous flow where neonates present with severe cyanosis and cardiogenic shock, surgical repair must be planned immediately. Mixing of well oxygenated blood through the anomalous connection of pulmonary veins with the systemic blood in the right atrium results in similar oxygen saturation in all cardiac chambers and arteries, therefore pre and post ductal oxygen saturations are equal. Increased blood flow across the right heart causes delay in closure of the pulmonary valve, presenting as fixed splitting of second heart sound as well as systolic flow murmur over the pulmonic region. Supra-cardiac drainage of anomalous pulmonary veins to the superior vena cava result in figure-eight or snow man appearance of the cardiac silhouette on CXR.