Total anomalous pulmonary venous return is a structural problem with the heart that causes oxygen-poor blood. It is a type of congenital heart defect, which means it develops before a baby is born.

With this defect, all the pulmonary veins from the lungs do not connect with the left side of the heart as they should. Instead, they connect to veins or structures that drain into the right side of the heart. This results in oxygen-rich blood flowing back into the right side of the heart.

The left side of the heart and the body get some oxygen-rich blood because of other defects that are usually present, including:

• Atrial septal defect, which is an opening in the wall (septum) between the upper chambers (atria) of the heart.
• Foramen ovale, which is an opening between the two upper chambers (atria) of the heart. This opening (which is present in the fetus but normally closes at birth) remains open in total anomalous pulmonary venous return.

Surgery is needed to correct the defect.