To understand patent ductus arteriosus (PDA), it helps to know how a normal heart works. Your child's heart is a muscle about the size of his or her fist. The heart works like a pump and beats 100,000 times a day.
The heart has two sides, separated by an inner wall called the septum. The right side of the heart pumps blood to the lungs to pick up oxygen. The left side of the heart receives the oxygen-rich blood from the lungs and pumps it to the body.
The heart has four chambers and four valves and is connected to various blood vessels. Veins are blood vessels that carry blood from the body to the heart. Arteries are blood vessels that carry blood away from the heart to the body.
The heart has four chambers or "rooms."
Four valves control the flow of blood from the atria to the ventricles and from the ventricles into the two large arteries connected to the heart.
Valves are like doors that open and close. They open to allow blood to flow through to the next chamber or to one of the arteries. Then they shut to keep blood from flowing backward.
When the heart's valves open and close, they make a "lub-DUB" sound that a doctor can hear using a stethoscope.
The arteries are major blood vessels connected to your heart.
The veins also are major blood vessels connected to your heart.
For more information about how a healthy heart works, go to the Health Topics How the Heart Works article. The article contains animations that show how your heart pumps blood and how your heart's electrical system works.
The ductus arteriosus is a blood vessel that connects the aorta and pulmonary artery in unborn babies. This vessel allows blood to be pumped from the right side of the heart into the aorta, without stopping at the lungs for oxygen.
While a baby is in the womb, only a small amount of his or her blood needs to go to the lungs. This is because the baby gets oxygen from the mother's bloodstream.
After birth, the baby no longer is connected to the mother's bloodstream. Thus, the baby's blood must travel to his or her own lungs to get oxygen. As the baby begins to breathe on his or her own, the pulmonary artery opens to allow blood into the lungs. Normally, the ductus arteriosus closes because the infant no longer needs it.
Once the ductus arteriosus closes, blood leaving the right side of the heart no longer goes into the aorta. Instead, the blood travels through the pulmonary artery to the lungs. There, the blood picks up oxygen. The oxygen-rich blood returns to the left side of the heart and is pumped to the rest of the body.
Sometimes the ductus arteriosus remains open (patent) after birth. A PDA allows blood to flow from the aorta into the pulmonary artery and to the lungs. The extra blood flowing into the lungs strains the heart. It also increases blood pressure in the lung's arteries.
Full-term infants. A small PDA might not cause any problems, but a large PDA likely will cause problems. The larger the PDA, the greater the amount of extra blood that passes through the lungs.
A large PDA that remains open for an extended time can cause the heart to enlarge, forcing it to work harder. Also, fluid can build up in the lungs.
A PDA can slightly increase the risk of infective endocarditis (IE). IE is an infection of the inner lining of the heart chambers and valves.
In PDA, increased blood flow can irritate the lining of the pulmonary artery, where the ductus arteriosus connects. This irritation makes it easier for bacteria in the bloodstream to collect and grow, which can lead to IE.
Premature infants. PDA can be more serious in premature infants than in full-term infants. Premature babies are more likely to have lung damage from the extra blood flowing from the PDA into the lungs. These infants may need to be put on ventilators. Ventilators are machines that support breathing.
Increased blood flow through the lungs also can reduce blood flow to the rest of the body. This can damage other organs, especially the intestines and kidneys.
The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.