Pulmonary atresia is a complex congenital heart defect. Because the baby’s pulmonary valve is either missing or blocked, blood gets to the lungs through different pathways. It may get through a hole between their ventricles or a hole between their atria.
Also, there is a blood vessel between the aorta and the pulmonary artery (ductus arteriosus) that is present in all children before birth but normally closes shortly after birth. This blood vessel can be kept open with medicine to allow enough blood to travel to the lungs. In babies with pulmonary atresia, the ductus arteriosus may be the only way blood gets to their lungs.
With ventricular septal defect
Some babies with pulmonary atresia have a hole in the wall between their ventricles. This is called a ventricular septal defect (VSD).
In these babies, oxygen-poor (blue) blood comes from the body into the right atrium. Next it flows into the right ventricle. Then it goes through the VSD into the left ventricle, which pumps it through the aorta to the rest of the body. Blood flow to the lung arteries is either from the ductus arteriosus or similar blood vessels from the aorta.
Without ventricular septal defect
If the baby does not have a VSD, the blood coming into the right atrium is directed to the left side of the heart through an opening in the wall between the atria. This opening is normal in newborns and is called the foramen ovale. The foramen ovale closes soon after birth. Some of the blood that enters the aorta goes through the ductus arteriosus into the pulmonary artery and to the lungs.