What is total anomalous pulmonary venous return?
Total anomalous pulmonary venous return (TAPVR) is a congenital (present at birth) heart defect. Due to abnormal development of the fetal heart during the first eight weeks of pregnancy, the vessels that bring oxygen-rich (red) blood back to the heart from the lungs are improperly connected.
Normally, oxygen-poor (blue) blood returns to the right atrium from the body, travels to the right ventricle, then is pumped through the pulmonary artery into the lungs where it receives oxygen. Oxygen-rich (red) blood returns to the left atrium from the lungs through four pulmonary veins. It then passes into the left ventricle, and is pumped through the aorta out to the body.
In TAPVR, the four pulmonary veins are connected somewhere besides the left atrium. There are several possible places where the pulmonary veins can connect. The most common connection is to a blood vessel that brings oxygen-poor (blue) blood back to the right atrium, usually the superior vena cava.
In TAPVR, oxygen-rich (red) blood that should return to the left atrium, the left ventricle, the aorta, and then the body, instead mixes with the oxygen-poor (blue) blood flowing into the right side of the heart. This situation by itself will not support life, because there is no way for oxygen-rich (red) blood to be delivered to the body.
Other heart defects are often associated with TAPVR, and they actually help the infant with total anomalous pulmonary venous return to live until surgical intervention is possible:
- An opening in the atrial or ventricular septum will allow blood from one side to mix with blood from another, creating "purple" blood with an oxygen level somewhere in-between that of the oxygen-poor (blue) and the oxygen-rich (red) blood.
- Patent ductus arteriosus will also allow mixing of oxygen-poor (blue) and oxygen-rich (red) blood through the connection between the aorta and pulmonary artery. The "purple" blood that results from this mixing is beneficial, providing at least a little oxygen to the body.
Total anomalous pulmonary venous return makes up about 1 to 2 percent of all cases of congenital heart defects and occurs equally in boys and in girls.