Pulmonary atresia

In pulmonary atresia, the valve that lets blood flow from the heart to the lungs doesn't form as it should. Instead, some blood may enter the lungs through a temporary connection called the ductus arteriosus. The ductus arterious is between a baby's main artery, called the aorta, and the pulmonary artery. The right lower heart chamber, called the right ventricle, may be small in some babies with pulmonary atresia.