Total anomalous pulmonary venous connection above the diaphragm Total anomalous pulmonary venous connection above the diaphragm. In this defect, the fully saturated pulmonary venous blood returns via the left innominate vein to the superior vena cava and, along with systemic venous return from the upper body, preferentially crosses the tricuspid valve to the right ventricle and main pulmonary artery. The less saturated systemic venous blood from the inferior vena cava passes preferentially across the foramen ovale to the left atrium and then into the left ventricle and ascending aorta. Therefore, pulmonary arterial oxygen saturation is higher than ascending aortic oxygen saturation. If there is a patent ductus arteriosus, a small right-to-left shunt causes descending aortic oxygen saturation to be higher than that in the ascending aorta. Contrast this diagram with the idealized situation depicted in Figure 7-2, where complete mixing is assumed to occur in the right atrium. Abbreviations: LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle. Source: Approach to the Infant With Excessive Pulmonary Blood Flow, Neonatal Cardiology, 3e Citation: Artman M, Mahony L, Teitel DF. Neonatal Cardiology, 3e; 2017 Available at: http://accesspediatrics.mhmedical.com/DownloadImage.aspx?image=/data/books/2045/neocard3_ch7_f009.png&sec=154265008&BookID=2045&ChapterSecID=154264904&imagename= Accessed: October 15, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved