Infracardiac TAPVR is a subtype of TAPVR in which the pulmonary veins drain to a confluence which in turn drains inferiorly, most commonly via a descending vertical vein through the diaphragm into the portal vein or ductus venosus prior to emptying into the inferior vena cava. This subtype of TAPVR often results in pulmonary venous obstruction as the descending vertical vein drains within the hepatic venous system. An atrial septal defect is necessary to allow pulmonary venous return to reach the left heart and systemic circulation.