The ductus arteriosus is a normal connection in utero between the pulmonary artery and the aorta. Since the lungs are still developing, the baby receives oxygenated blood from the mother during pregnancy. The ductus arteriosus allows the greater part of the oxygenated blood to bypass the non-aerated lungs by flowing directly from the pulmonary artery to the aorta. After the baby is born and begins breathing, hormonal changes occur causing the ductus arteriosus to close. A patent ductus arteriosus, or PDA, is when this connection does not close as it normally should. If the ductus remains open, the direction of flow reverses and some of the oxygen-rich blood from the aorta flows to the pulmonary artery and into the lungs. This may cause an excessive amount of blood flow to the lungs.
There are two reasons that necessitate the closure of a PDA. The first is the size of the ductus, which in turn determines the volume of extra blood being directed to the lungs. A large volume overload may result in enlargement of the heart and over time heart failure. The second reason is to avoid the risk of developing an infection in the heart known as endocarditis. Approximately, one-eighth of patients with a PDA will develop endocarditis. This increases mortality by 50% whereas the risk of surgery is almost zero.
Depending on the size of the ductus, a PDA may be treated in one of two ways. If the ductus is large, the child may require surgery that involves closing off the ductus with a clamp or suture. However, in many cases, the PDA can be closed using a spring coil or a synthetic plug. Both devices are introduced through a heart catheter, which is passed through a vein in the leg that leads up to the heart.
How Does Patent Ductus Arteriosus (PDA) Differ From Normal Cardiac Anatomy?
If your child has patent ductus arteriosus (PDA) or another congenital heart defect, there's usually something wrong with the structure of his or her heart.
Heart with Normal Cardiac Anatomy
When your child has a congenital heart defect, there's usually something wrong with the structure of his or her heart's structure.
The heart is composed of four chambers. The two upper chambers, known as atria, collect blood as it flows back to the heart. The two lower chambers, known as ventricles, pump blood with each heartbeat to the two main arteries (the pulmonary artery and the aorta). The septum is the wall that divides the heart into right and left sides. The atrial septum separates the right and left atria; likewise, the ventricular septum separates the two ventricles.
There are four valves that control the flow of blood through the heart. These flap-like structures allow blood to flow in only one direction. The tricuspid and mitral valves, also known as the atrioventricular valves, separate the upper and lower chambers of the heart. The aortic and pulmonary valves, also known as the arterial valves, separate the ventricles from the main arteries. Oxygen-depleted blood returns from the body and drains into the right atrium via the superior and inferior vena cavas. The blood in the right atrium then passes through the tricuspid valve and enters the right ventricle.
Next, the blood passes through the pulmonary valve, enters the pulmonary artery, and travels to the lungs where it is replenished with oxygen. The oxygen-rich blood returns to the heart via the pulmonary veins, draining into the left atrium. The blood in the left atrium passes through the bicuspid, or mitral, valve and enters the left ventricle.
Finally, the oxygen-rich blood flows through the aortic valve into the aorta and out to the rest of the body.
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Patent Ductus Arteriosus (PDA)
The lungs are not used while a fetus is in the amniotic fluid because the baby gets oxygen directly from the mother's placenta. When a newborn breathes and begins to use the lungs, the DA is no longer needed and usually closes during the first 2 days after birth.
But when the DA fails to close, a condition called patent (meaning "open") ductus arteriosus (PDA) results, in which oxygen-rich blood from the aorta is allowed to mix with oxygen-poor blood in the pulmonary artery. As a result, too much blood flows into the lungs, which puts a strain on the heart and increases blood pressure in the pulmonary arteries.
The cause of PDA is not known, but genetics might play a role. PDA is more common in premature babies and affects twice as many girls as boys. It's also common among babies with neonatal respiratory distress syndrome, babies with genetic disorders (such as Down syndrome), and babies whose mothers had German measles (rubella) during pregnancy.
In the vast majority of babies with a PDA but an otherwise normal heart, the PDA will shrink and go away on its own in the first few days of life. Some PDAs that don't close then will close on their own by the time the child is a year old.
In premature infants, the PDA is more likely to stay open, particularly if the baby has lung disease. When this happens, treatment to close the PDA might be considered.
In infants born with additional heart defects that decrease blood flow from the heart to the lungs or decrease the flow of oxygen-rich blood to the body, the PDA could actually be beneficial and the doctor might prescribe medicine to keep the ductus arteriosus open.
Symptoms and Tests
Babies with a large PDA might experience symptoms such as:
- a bounding (strong and forceful) pulse
- fast breathing
- poor feeding habits
- shortness of breath
- sweating while feeding
- tiring very easily
- poor growth
If a PDA is suspected, the doctor will use a stethoscope to listen for a heart murmur, which is often heard in babies with PDAs. Follow-up tests might include:
- a chest X-ray
- an EKG, a test that measures the heart's electrical activity and can show if the heart is enlarged
- an echocardiogram, a test that uses sound waves to diagnose heart problems. These waves bounce off parts of the heart, creating a picture of the heart that is shown on a monitor. In babies with PDA, an echo shows how big the opening is and how well the heart is handling it.
The three treatment options for PDA are medication, catheter-based procedures, and surgery. A doctor will close a PDA if the size of the opening is large enough that the lungs could become overloaded with blood, a condition that can lead to an enlarged heart.
A PDA also might be closed to reduce the risk of developing a heart infection known as endocarditis, which affects the tissue lining the heart and blood vessels. Endocarditis is serious and requires treatment with intravenous (IV) antibiotics.
Reviewed by: Gina Baffa, MD
Date reviewed: February 2012