Patent ductus arteriosus

Definition

Patent ductus arteriosus (PDA) is the failure of the ductus arteriosus to close after birth, allowing blood to inappropriately flow from the aorta into the pulmonary (lung) artery. The ductus arteriosus is a normal opening between the aortic arch and the pulmonary artery that functions while the fetus is in the uterus. It normally closes within the first few days of life.

Description

The ductus arteriosus is an opening between the aortic arch and the pulmonary artery that allows some of the blood pumped from the right ventricle toward the lungs to bypass the lungs and enter the aortic arch for distribution throughout the body. This bypass is used while the fetus is developing in the uterus and the lungs are not in use. After birth, when the lungs are in use, the ductus arteriosus normally closes; thus, all the blood pumped from the right ventricle goes to the lungs.

If the ductus arteriosus fails to close, the blood from the aortic arch will enter the pulmonary artery and recycle through the lungs. This causes the heart to work harder trying to supply enough blood to the body. If the ductus is sufficiently large, the left ventricle is forced to pump blood to both the lungs and the body. In which case, pulmonary congestion and left ventricle heart failure may result.

In most cases, the left ventricle responds to the increased demands for more blood by enlarging, and the blood vessels in the lungs may adapt to the increased pressure. In cases where the blood pressure in the lungs is higher than that of the body, blood returning to the heart is shunted back into the aorta without passing through the lungs. Such blood does not carry much oxygen, and this results in insufficient oxygen being delivered to the body, especially the legs. Endocarditis (an inflammation of the lining of the heart) can be a complication of PDA. PDA is more common in premature infants.

Causes & symptoms

Usually, there are no overt symptoms of PDA, unless the ductus arteriosus size is large. Children with a large ductus arteriosus can show difficulty in breathing upon moderate physical exercise, and fail to gain weight.

Diagnosis

Diagnosis is made by detecting a characteristic heart murmur. Chest x ray, electrocardiogram, and echocardiograms are all used to support the initial diagnosis. Typically, a child will fail to gain weight, experience frequent chest infections, and breathe heavily during mild physical exertion.

Treatment

The first treatment is the drug indomethacin. This drug is used in many premature infants, a group whose ductus arteriosus closes at a slower rate. If the ductus still fails to close, surgery is required. Recently developed alternatives to surgical closure are interventional cardiac catheterization and video-assisted thorascopic surgical repair.

Prognosis

Children can survive with a small opening remaining in the ductus arteriosus. Surgery is usually successful and frequently without complications, and allows children to lead normal lives.

Key Terms

Catheterization

The process of inserting a hollow tube into a body cavity or blood vessel.

Echocardiograph

A record of the internal structures of the heart obtained from beams of ultrasonic waves directed through the wall of the chest.

Electrocardiograph

A record of the waves which relate to the electrical impulses produced at each beat of the heart.

Endocarditis

An inflammation of the interior lining of the heart, usually caused by infectious agents.

Further Reading

For Your Information

Books

• Alexander, R.W., R. C. Schlant, and V. Fuster, eds. The Heart. 9th ed. New York: McGraw-Hill, 1998.
• Berkow, Robert, ed. Merck Manual of Medical Information. Whitehouse Station, NJ: Merck Research Laboratories, 1997.
• Larsen, D.E., ed. Mayo Clinic Family Health Book. New York: William Morrow and Company, Inc., 1996.

Gale Encyclopedia of Medicine. Gale Research, 1999.