Patent ductus arteriosus (PDA) is a defect in which the temporary blood vessel connecting the left pulmonary artery to the aorta in the fetal heart fails to close after birth. In the fetal heart, blood bypasses the lungs and gets oxygen from the placenta. But when the newborn’s lungs take over at birth, the body stops producing the chemicals that keep the ductus arteriosus open, and it closes naturally.

If the ductus arteriosus fails to close completely, the baby has PDA. While this problem is rare, it is sometimes associated with mothers who have had German measles (rubella) during pregnancy and with infants born before their due date (prematurely).

The result of this defect is that too much blood travels to the lungs. The severity of the problem depends on how large the opening is and how prematurely the baby was born.

What are the symptoms?

With mild cases of PDA, there may be a heart murmur that presents no problems. But in severe cases, too much blood is sent to the lungs. This increases the pressure in the pulmonary artery and causes fluid to build up in the lungs. In these cases, children may be short of breath and very tired.

Sometimes, PDA is hard to diagnose in premature babies because they may need to be on a breathing machine (called a ventilator) while their lungs develop. The ventilator may mask the presence of PDA.

How is it treated?

In premature infants, PDA sometimes can be treated with medicines that cause the ductus to close. In full-term infants and older children, surgery is used to tie off the ductus.

To block the ductus arteriosus without surgery, doctors may use a catheterization procedure to insert a tiny closure device.

It is important to correct PDA because it can lead to congestive heart failure and a disease of the right side of the heart (called cor pulmonale) later in life. PDA also increases the risk of endocarditis, a life-threatening infection of the lining that covers the heart chambers, valves, and main arteries.