In total anomalous pulmonary venous return, one or more abnormal connections between the pulmonary veins and the heart causes oxygen-rich blood coming from the lungs to mix with poorly oxygenated blood (blue in color) before being pumped into the body. One result is that the child’s skin color may have a bluish cast (cyanosis).
In the normal heart, well oxygenated blood returns to the heart from the lungs through four pulmonary veins (two from each lung). The pulmonary veins connect directly into the heart’s left upper chamber (left atrium).
In anomalous pulmonary venous return, the pulmonary veins may connect to other veins, rather than directly to the back of the left upper chamber of the heart (left atrium). These can connect above the level of the heart into other veins (supracardiac), to parts of the heart other than normal (cardiac), to veins below the level of the diaphragm beneath the lungs (infracardiac), or may be a combination of these abnormalities (mixed). Most common is a supracardiac connection in which all of the pulmonary veins meet and drain into the major vein that returns blood from the upper body to the heart (the superior vena cava). In other cases, the pulmonary veins may meet to form a single vein that drains into the blood circulation of the liver or into the blood vessel that drains blood from the heart muscle (the coronary sinus).
When all or most of the pulmonary veins drain in an abnormal fashion, red oxygen-rich blood returning from the lungs mixes with bluish poorly oxygenated blood in the heart’s right upper chamber (right atrium). The result is bluish-colored blood.
This blood will flow to the right ventricle, increasing the amount of blood flow to the lungs and leading to lung congestion and heart failure. Some of the blood will cross from the right atrium to the left atrium through a hole in the wall that separates the heart’s two upper chambers. (All children are born with the hole.) It will then flow to the left ventricle and out to the body. The mixture of bluish and red blood in the body will cause the child’s lips and skin to become bluish in color.
Bluish discoloration of the skin may be a symptom of this condition. If or when lung congestion and heart failure result, the child may feed poorly and grow inadequately. Severe obstruction of these blood vessels may result in life-threatening deficiency of oxygen (cyanosis) very soon after birth. This is because the heart is unable to get oxygenated blood out of the lungs to the body, requiring emergency surgery or invasive catheterization procedures.
Progression and Possible Complications
If a baby is born with obstruction in the pathway that lets blood out of the lungs back to the heart, severe cyanosis may develop that is not responsive to additional oxygen. The cyanosis may be extremely severe, resulting in a life-threatening situation that requires emergency surgical or catheter-based intervention (a minimally invasive procedure performed using thin tubes). If there is no obstruction of blood in the pathway back to the heart, the effects of the blood flow is like that of a very large hole between the upper chambers of the heart. Lung congestion and heart failure can begin to occur within a few weeks to months after birth. Surgical repair will be necessary in infancy to route the blood directly back to the heart.
Surgical repair is necessary for anomalous pulmonary venous return. During surgery, the pulmonary veins are reconnected to the heart’s left atrium, and the hole in the wall between the two atria is closed.
Surgical results are typically very good, and children typically lead normal lives after the defect is repaired, unless there has been significant damage to the lungs due to obstruction of flow through the veins.
Occasionally after surgery, the pulmonary veins may become obstructed again at the point where they enter the left atrium. These factors may lead to high blood pressure in the lungs. This obstruction (and resulting high blood pressure) may be relieved through a catheterization procedure in which a physician delivers a a small wire mesh tube (stent) through the arteries and implants it at the entrance of the left atrium to help keep the pulmonary vein open. Alternatively, surgical re-repair of the obstructed veins may be performed.
Despite the use of stents, balloon angioplasty or reoperation, renarrowing of the pulmonary veins (restenosis) can be a significant problem. It is felt that there is an abnormal tissue response that causes abnormal growth within the vessels. Multiple angioplasty or stenting procedures may have to be performed. Another operation may be indicated as well.