Patent Ductus Arteriosus

Patent ductus arteriosus (PDA) is a heart problem that occurs soon after birth in some babies. In PDA, there is an abnormal circulation of blood between two of the major arteries near the heart. Before birth, the two major arteries—the aorta and the pulmonary artery—are normally connected by a blood vessel called the ductus arteriosus, which is an essential part of the fetal circulation. After birth, the vessel is supposed to close within a few days as part of the normal changes occurring in the baby's circulation. In some babies, however, the ductus arteriosus remains open (patent). This opening allows blood to flow directly from the aorta into the pulmonary artery, which can put a strain on the heart and increase the blood pressure in the lung arteries.

Figure A shows the normal anatomy and blood flow of the interior of the heart. Figure B shows a heart with a patent ductus arteriosus. The defect connects the aorta with the pulmonary artery, allowing oxygen-rich blood from the aorta to mix with oxygen-poor blood in the pulmonary artery.

A PDA is a type of congenital heart defect. A congenital heart defect is any type of heart problem that is present at birth.

If your baby has a PDA, but has an otherwise normal heart, the PDA may shrink and go away completely, or it may need to be treated to close it. But, if your baby is born with certain types of heart defects that decrease blood flow from the heart to the lungs or the body, medicine may be given to keep the ductus arteriosus open to maintain blood flow and oxygen levels until corrective surgery for the heart defect(s) can be performed.

About 3,000 infants are diagnosed with PDA each year in the United States. It is more common in premature infants (babies born too early) but does occur in full-term infants. Premature babies with PDA are more vulnerable to its effects. PDA is twice as common in girls as in boys.

Symptoms and Diagnosis

A heart murmur may be the only sign that a baby has patent ductus arteriosus (PDA). A heart murmur is an extra or unusual sound heard during the heartbeat.

Some infants may develop signs or symptoms of volume overload on the heart and excess blood flow in the lungs. Signs and symptoms may include:

• Fast breathing, working hard to breathe, or shortness of breath, or in the case of a premature infant, need for increased oxygen or ventilatory support
• Poor feeding and poor weight gain
• Tiring easily
• Sweating with exertion (such as while feeding)

To diagnose PDA, the following tests may be used:

• Echocardiogram. This test, which is harmless and painless, uses sound waves to create a moving picture of your baby's heart. During an echocardiogram, reflected sound waves outline the heart's structure completely. The test allows the doctor to clearly see any problem with the way the heart is formed or the way it's working. An echocardiogram is the most important test available to your baby's cardiologist to both diagnose a heart problem and follow the problem over time. In babies with PDA, the echocardiogram shows how big the ductus is and how well the heart is responding to it. When medical treatments are used to try to close a ductus in premature babies, echocardiograms are used to see how well the treatment is working.
• EKG (electrocardiogram). This test records the electrical activity in the heart. In the case of a PDA, it can show:
  • Enlargement of the heart chambers
  • Other subtle changes that can suggest the presence of a PDA

Causes

The cause of patent ductus arteriosus (PDA) is not known.

Genetics may play a role. A defect in one or more genes could prevent the ductus arteriosus from closing normally after birth.

PDA is more common in:

• Premature infants (babies born too early)
• Infants with genetic abnormalities such as Down syndrome
• Infants whose mother had German measles (rubella) during pregnancy

Reference:

National Heart, Lung, and Blood Institute, USA.