Pulmonary atresia is a congenital malformation of the pulmonary valve in which the valve opening fails to develop. The valve is completely closed thereby obstructing the outflow of blood from the heart to the lungs.

In a normal functioning heart, the opening to the pulmonary valve has three flaps that open and close like one way doors. The opening and closing of the flaps forces blood to flow forward into the pulmonary artery and backward into the right ventricle then forward again to the lungs where the blood becomes oxygenated.

In patients with pulmonary atresia the flap openings are completely covered by a layer of tissue, thus preventing the ability of blood flow to the lungs. This results in blood not being oxygenated. The body requires oxygenated blood for survival. Pulmonary atresia is not threatening to a developing fetus however, because the mother's placenta provides the needed oxygen since the baby's lungs are not yet functional. Once the baby is born its lungs must now provide the oxygen needed for survival. Due to thr condition, the newborn baby is blue in color and pulmonary atresia can usually be diagnosed within hours or minutes after birth.

Types

There are two types of pulmonary atresia:

• Pulmonary atresia with intact ventricular septum (PA-IVS). It is a rare congenital lesion. PA-IVS involves complete blockage of the pulmonary valve located on the right side of the heart.
• Pulmonary atresia with ventricular septal defect or VSD. It is identified by underdevelopment of the right ventricle (a second opening in the ventricular wall). This opening provides a way out for blood in the right ventricle. When this second opening (VSD) does not exist, very little blood goes to the right ventricle, which is what causes it to be underdeveloped. This defect can also be determined before birth.

Treatment

An IV medication called prostaglandin E1 is used for treatment of pulmonary atresia, which helps the blood circulate through the body, but it is extremely dangerous because it causes apnea. Heart catheterization may be performed to evaluate the defect. This procedure is much more invasive. Ultimately, the patient will need to have a series of surgeries to improve the blood flow permanently.