The ductus arteriosus is a normal blood vessel that connects two major arteries — the aorta and the pulmonary artery — that carry blood away from the heart in a developing fetus.
The lungs are not used while a fetus is in the womb because the baby gets oxygen directly from the mother's placenta. The ductus arteriosus diverts blood away from the lungs and sends it directly to the body. When a newborn breathes and begins to use the lungs, the ductus is no longer needed and usually closes during the first 2 days after birth.
But when the ductus fails to close, a condition called patent (meaning "open") ductus arteriosus (PDA) results, in which oxygen-rich blood from the aorta is allowed to mix with oxygen-poor blood in the pulmonary artery. As a result, too much blood flows into the lungs, which puts a strain on the heart and increases blood pressure in the pulmonary arteries.
The cause of PDA is not known, but genetics might play a role. PDA is more common in premature babies and affects twice as many girls as boys. It's also common among babies with neonatal respiratory distress syndrome, babies with genetic disorders (such as Down syndrome), and babies whose mothers had rubella (also called German measles) during pregnancy.
In the vast majority of babies with a PDA but an otherwise normal heart, the PDA will shrink and go away on its own in the first few days of life. Some PDAs that don't close then will close on their own by the time the child is a year old.
In premature infants, the PDA is more likely to stay open, particularly if the baby has lung disease. When this happens, doctors might consider treatment to close the PDA.
In infants born with other heart problems that decrease blood flow from the heart to the lungs or decrease the flow of oxygen-rich blood to the body, the PDA may actually help, and the doctor might prescribe medicine to keep the ductus arteriosus open.
Symptoms and Tests
Babies with a large PDA might have symptoms such as:
a bounding (strong and forceful) pulse
poor feeding habits
shortness of breath
sweating while feeding
tiring very easily
If a PDA is suspected, the doctor will use a stethoscope to listen for a heart murmur, which is often heard in babies with PDAs. Follow-up tests might include:
an EKG, a test that measures the heart's electrical activity and can show if the heart is enlarged
an echocardiogram, a test that uses sound waves to diagnose heart problems. These waves bounce off parts of the heart, creating a picture of the heart that is shown on a monitor. In babies with PDA, an echo shows how big the opening is and how well the heart is handling it.
The three treatment options for PDA are medication, catheter-based procedures, and surgery. A doctor will close a PDA if the size of the opening is large enough that the lungs could become overloaded with blood, a condition that can lead to an enlarged heart.
A doctor might also close a PDA to reduce the risk of developing a heart infection known as endocarditis, which affects the tissue lining the heart and blood vessels. Endocarditis is serious and requires treatment with intravenous (IV) antibiotics.