What is patent ductus arteriosus (PDA)?
Patent ductus arteriosus (PDA) is a heart condition that occurs when the ductus arteriosus does not close. The ductus arteriosus is a temporary blood vessel connecting the pulmonary artery (the main heart vessel leading to the lungs) to the aorta (the main blood vessel of the body). Everyone is born with a ductus arteriosus; if it remains open after birth, it is called a patent ductus arteriosus, or PDA.
Why does a baby have a ductus arteriosus?
Before birth, the fetus receives oxygen from the mother and the placenta, the organ that connects the growing baby to the mother’s uterus. Since the fetus does not need to use his or her lungs, very little blood needs to go to them to help them grow. The ductus arteriosus allows most of the blood to bypass the lungs and go to the rest of the body.
When the baby is born, his or her lungs take over and the body stops producing the chemicals that have kept the ductus arteriosus open. Under normal circumstances, the ductus arteriosus gradually narrows and closes in the first few hours or days after birth.
If it doesn’t close, the baby has patent (open) ductus arteriosus. This defect occurs more often in premature babies, but may also occur in full-term infants. The cause of PDA is not known in most cases.
What happens when the ductus arteriosus stays open?
When the ductus arteriosus stays open, blood goes in the opposite direction than it does in the fetus: from the aorta to the lungs. This extra blood, along with the normal flow of blood from the heart to the lungs, can cause a build-up of blood in the baby’s lungs. If the PDA is large, this extra blood flow is too much for the baby to handle and makes it harder for him or her to breathe. Because PDA increases the amount of work for the heart, the baby can have heart failure.
In many cases, the PDA is not large enough to cause symptoms of heart failure in infancy. However, if there is enough blood flow to cause a heart murmur (an abnormal noise), the PDA should be closed. A heart murmur can be heard with a stethoscope when the baby has a PDA.
In some cases, symptoms can occur later in life because of the increased blood flow into the lungs over many years. These symptoms include heart rhythm abnormalities, pulmonary hypertension (high blood pressure in the lung’s blood vessels), and heart failure. Another important reason to close a PDA in children is to prevent bacterial endocarditis, an infection of the blood vessels surrounding the PDA.