Right atrial isomerism, partial anomalous pulmonary venous connection (PAPVC) and atrioventricular septal defect

Partial anomalous pulmonary venous connection (PAPVC) is a rare congenital cardiac defect. As the name suggests, in PAPVC, the blood flow from a few of the pulmonary veins return to the right atrium instead of the left atrium. Usually, a single pulmonary vein is anomalous. Rarely, all the veins from one lung are anomalous. Thus, some of the pulmonary venous flow enters the systemic venous circulation.

Embryologically, PAPVC is similar to total anomalous pulmonary venous connection (TAPVC); however, TAPVC differs in that all or most pulmonary venous vessels connect to the right side of the heart in TAPVC (see the image below). Knowledge of the variation patterns of normal pulmonary venous drainage is necessary in order to diagnose PAPVC.