Partial anomalous pulmonary venous return

Partial anomalous pulmonary venous return

In partial anomalous pulmonary venous return, some of the pulmonary veins carrying blood from the lungs to the heart flow into other blood vessels or into the heart's right atrium, instead of correctly entering the heart's left atrium. This causes some oxygen-rich blood from the lungs to mix with oxygen-poor blood before entering the right atrium. In a normal heart, as shown on the left, oxygen-rich blood from the pulmonary veins returns to the left atrium.