Patent ductus arteriosus (PDA) is a condition in which a blood vessel called the ductus arteriosus fails to close normally in an infant soon after birth. (The word "patent" means open.)

The condition leads to abnormal blood flow between the aorta and pulmonary artery, two major blood vessels surrounding the heart.

Before birth, a baby receives oxygen in the blood through the umbilical cord. The ductus arteriosus allows this blood to bypass the baby's lungs. Soon after the infant is born and the lungs inflate with air, the blood vessel is supposed to close. If it does not, the PDA moves blood from the aorta to the pulmonary artery, leading to improper blood circulation.

Every year in the United States, about 3000 infants are diagnosed with PDA.

PDA affects girls more often than boys. The condition is more common in premature infants and those with neonatal respiratory distress syndrome. Infants with genetic disorders such as Down syndrome and whose mothers had German measles (rubella) during pregnancy at higher risk for PDA.

PDA is common in babies with congenital heart problems such as with coarctation of the aorta, transposition of the great vessels, and ventricular septal defect.

A small PDA may not cause any symptoms. However, if the PDA has increased the stress on the heart or the blood vessels in the lungs, the baby may have symptoms such as:

• Bounding pulse
• Fast breathing
• Poor feeding habits
• Shortness of breath
• Sweating while feeding
• Tiring very easily

Babies with PDA often have a characteristic heart murmur that can be heard with a stethoscope. However, in premature infants, a heart murmur may not be heard. Doctor's may suspect the condition if the infant has breathing or feeding problems soon after birth.

Changes may be seen on chest x-rays. The diagnosis is confirmed with an echocardiogram.

Sometimes, a small PDA may not be diagnosed until later in childhood.