Patent Ductus Arteriosus

Patent ductus arteriosus (PDA) is a heart problem that occurs soon after birth in some babies. 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 ductus arteriosus typically closes within a few days as part of the normal changes occurring in the newborn circulation. In some babies, however, the ductus arteriosus remains open (patent). The result is that blood is able 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 arteries of the lung. Isolated PDA is relatively common, accounting for about 8% of congenital heart disease (CHD). Patent ductus arteriosus usually occurs in isolation, but occurs with increased frequency in premature births and in combination with other CHD (especially those with pulmonary hypertension).

Illustration showing normal anatomy and blood flow and a heart with patent ductus arteriosus. Source: National Institutes of Health

Parts of the Heart

Cross-section of a healthy heart and its inside structures. The blue arrow shows the direction in which oxygen-poor blood flows from the body to the lungs. The red arrow shows the direction in which oxygen-rich blood flows from the lungs to the rest of the body. Source: National Institutes of Health

A child's heart is a muscle about the size of his or her fist. It 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. Then, oxygen-rich blood returns from the lungs to the left side of the heart, and the left side pumps it to the body.

Chambers

The heart has four chambers and four valves and is connected to various blood vessels. Veins are the blood vessels that carry blood from the body to the heart. Arteries are the blood vessels that carry blood away from the heart to the body.

• The atria are the two upper chambers that collect blood as it comes into the heart.
• The ventricles are the two lower chambers that pump blood out of the heart to the lungs or other parts of the body.

Valves

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.

• The tricuspid valve is in the right side of the heart, between the right atrium and the right ventricle.
• The pulmonary valve is in the right side of the heart, between the right ventricle and the entrance to the pulmonary artery, which carries blood to the lungs.
• The mitral valve is in the left side of the heart, between the left atrium and the left ventricle.
• The aortic valve is in the left side of the heart, between the left ventricle and the entrance to the aorta, the artery that carries blood to the body.

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, and 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 first sound is made by the mitral and tricuspid valves closing at the beginning of systole. Systole is when the ventricles contract, or squeeze, and pump blood out of the heart.
• The second sound is made by the aortic and pulmonary valves closing at beginning of diastole. Diastole is when the ventricles relax and fill with blood pumped into them by the atria.

Arteries

The arteries are major blood vessels connected to the heart.

• The pulmonary artery carries blood pumped from the right side of the heart to the lungs to pick up a fresh supply of oxygen.
• The aorta is the main artery that carries oxygen-rich blood pumped from the left side of the heart out to the body.
• The coronary arteries are the other important arteries attached to the heart. They carry oxygen-rich blood from the aorta to the heart muscle, which must have its own blood supply to function.

Veins

The veins are also major blood vessels connected to the heart.

• The pulmonary veins carry oxygen-rich blood from the lungs to the left side of the heart so it can be pumped out to the body.
• The vena cava is a large vein that carries oxygen-poor blood from the body back to the heart.

The Heart with Patent Ductus Arteriosus

The ductus arteriosus is a blood vessel that connects a baby's aorta and pulmonary artery while the he or she is in the womb. This connection allows blood to be pumped from the right side of the heart straight to the aorta without stopping at the lungs for oxygen. In the womb, only a small amount of a baby's blood needs to go to the lungs because the baby gets oxygen from the mother's bloodstream. The baby's pulmonary artery, which carries blood to the lungs, is not needed at this time.

After birth, the baby is no longer connected to the mother's bloodstream. The baby's blood must now go to his or her own lungs to get oxygen. Normally, as the baby begins to breathe on his or her own, the pulmonary artery opens to allow blood into the lungs, and the ductus arteriosus closes. Once the ductus arteriosus closes, blood leaving the right side of the heart no longer goes straight to the aorta. First, it goes through the pulmonary arteries and stops at the lungs to pick up oxygen. Then, blood carrying oxygen returns to the left side of the heart and is pumped out to the rest of the body.

If the ductus arteriosus does not close after birth as it should, it is called a patent ductus arteriosus (PDA). A PDA allows blood to flow directly from the aorta into the pulmonary artery and from there to the lungs. This extra amount of blood flowing into the lungs strains the heart and increases the blood pressure in the arteries of the lungs.

Signs and Symptoms

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 unusually hard to breathe
• Shortness of breath
• Need for increased oxygen or ventilatory support
• Poor feeding and poor weight gain
• Tiring easily
• Sweating with exertion (such as while feeding)

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

Diagnosis

In full-term infants, a patent ductus arteriosus (PDA) usually is first suspected when the baby's doctor hears a heart murmur during a regular checkup. If a PDA is large, the infant may also develop symptoms of volume overload and increased blood flow to the lungs. When a PDA is small, it may not be diagnosed until later in childhood. Once a PDA is suspected, a consultation with a pediatric cardiologist will be arranged. A pediatric cardiologist is a doctor who specializes in diagnosing and treating heart problems in children.

In premature babies with PDA, the physical signs that are seen in full-term babies, such as heart murmur, may not be present. Doctors may suspect a PDA in premature babies who develop breathing difficulties soon after birth. Doctors use tests such as echocardiography to look for PDA in premature babies with breathing problems.

Tests

Two painless tests are used to diagnose a PDA.

• Echocardiogram. This test, which is harmless and painless, uses sound waves to create a moving picture of the 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 a 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.
• Electrocardiogram (EKG). This test records the electrical activity in the heart. In the case of a PDA, it can show enlargement of the heart chambers or other subtle changes that can suggest the presence of a PDA

Treatment

The goal of treatment is to close the patent ductus arteriosus (PDA) to prevent complications and reverse the effects of increased blood volume.

Small PDAs often close without treatment. For full-term infants, treatment is needed if the child's PDA:

• Is too large to close on its own
• Is causing the child to have health problems
• Does not close on its own by the time the child is one to– two years of age

For premature infants, treatment is needed if the PDA is causing respiratory distress or heart problems like congestive heart failure. If a 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 the 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.

Treatment

Treatment options for PDA include:

• Medicines
• Catheter-based procedures
• Surgery

Medicines

Medicines can be given to help close a PDA.

• Indomethacin is a drug that helps close a PDA in premature infants. It does not usually work in full-term infants. It works by stimulating the PDA to constrict or tighten, closing the connection.
• Ibuprofen is a medicine in the same family as indomethacin (non-steroidal anti-inflammatory or NSAID). It is also used frequently to close a PDA in premature infants.

If a PDA is small and the decision is made not to treat it right away, antibiotics may be prescribed to prevent endocarditis.

Catheter-based procedures

Catheters are thin, flexible tubes used in a procedure called cardiac catheterization. Catheter-based procedures are often used to close PDAs in infants or children who are large enough to have the procedure. The child's doctor may refer to the procedure as "transcatheter device closure." The procedure is sometimes done on small PDAs to prevent the risk of bacterial endocarditis.

During the procedure, the child will be sedated or given general anesthesia so he or she will sleep and not feel any discomfort. The doctor will place a catheter in a large blood vessel in the upper thigh (groin) and guide it into the child's heart.

A small metal coil or other blocking device is passed up through the catheter and placed in the ductus arteriosus to block blood flow through the vessel.

Catheter-based procedures:

• Do not require the child's chest to be opened
• Let the child recover quickly

Closing a PDA using a catheter is often done on an outpatient basis. Parents will most likely be able to take their child home the same day the procedure is done.

Complications of catheter-based procedures are rare and short term. They can include bleeding, infection, and movement of the blocking device from where it was placed.

Surgery

Surgery for PDA may be performed when:

• A premature or full-term infant develops health problems from the PDA and is too small to have a catheter-based procedure
• A PDA is not successfully closed by a catheter-based procedure
• Surgery also needs to be done for related congenital heart defects

Surgery often is not performed until after six months of age in infants who do not have health problems from the PDA. Doctors sometime perform surgery on small PDAs to prevent the risk of bacterial endocarditis.

The operation is done under general anesthesia so that the child will sleep and not feel any pain. The surgeon will:

• Make a small cut between the child's ribs to reach the PDA
• Close the PDA with stitches or clips

Complications of the surgery are rare and usually short term. They can include hoarseness, a paralyzed diaphragm, infection, bleeding, or fluid buildup around the lungs.

Living with Patent Ductus Arteriosus

Most children are healthy and live normal lives after treatment for a patent ductus arteriosus (PDA).

If the child was not born prematurely (too early), he or she is expected to have normal activity levels, appetite, and growth after PDA treatment, as long as there are no other congenital heart defects.

If the child was born prematurely, the outlook after PDA treatment depends primarily on other factors, such as:

• How early he or she was born
• Whether he or she has other illnesses or conditions, such as other congenital heart defects

Chances of Developing Patent Ductus Arteriosus

About 3,000 infants are diagnosed with PDA each year in the United States. It is more common in premature infants 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.

Related Problems

Normal birth-weight infants

The larger a PDA is, the greater the amount of extra blood that passes through the lungs. A small PDA might not cause any problems, whereas a larger PDA is likely to cause problems.

• PDA can increase the risk of bacterial endocarditis. Bacterial endocarditis is an infection of the lining of the heart, valves, or arteries. In the case of PDA, the increased flow of blood can irritate the lining of the pulmonary artery where the PDA connects. This irritation makes it easier for bacteria in the bloodstream to collect and grow there.
• A large PDA that is allowed to remain open for an extended period of time can cause the heart to enlarge and to have to work harder. Also, fluid can build up in the lungs.

Premature infants

For premature infants, PDA can be more serious than in normal weight babies. Preemies with PDA are more likely to have damage to their lungs from the extra blood flowing through the PDA. Preemies with PDA may need to be on a ventilator to help them with their breathing.

• The increased flow of blood through the lungs also can reduce blood flow to the rest of the body. This can damage other organs, especially the intestines and kidneys.
• Children who have PDAs are at increased risk for bacterial endocarditis. To prevent this infection, the doctor may give antibiotics before medical or dental procedures (such as surgery or dental cleanings) that could allow bacteria into the bloodstream.
• Once the PDA is closed, a child will not need antibiotics before dental work or surgical procedures. If the PDA is closed surgically or by catheter and remains completely closed, antibiotics will not be needed after six months.

Clinical Trials

• ClinicalTrials.gov: PDA

Research

• There has been research into using a device called the Amplatzer muscular ventricular septal defect occluder (AMVSDO) for treatment of PDA with high pulmonary artery pressure. It carries a lower risk of embolization, a complication of other devices placed through catheterization.^{[1] [2]}
• A recent study also looked at the efficacy of doing repeated echocardiogram studies on premature infants rather than awaiting symptoms to follow progress. This type of monitoring may reduce complications of PDA. ^[3]
• A study was published in the journal "Pediatrics" in December 2007. It showed that some PDAs have a negative effect on the oxygenation of the premature brain. Prompt diagnosis and treatment of PDA may decrease the chance of brain damage from lack of oxygen. ^[4]

References

1. ↑ Pass RH, Hijazi Z, Hsu DT, Lewis V, Hellenbrand WE. Multicenter USA Amplatzer patent ductus arteriosus occlusion device trial: initial and one-year results. J Am Coll Cardiol. 2004 Aug 4;44(3):513-9. Abstract
2. ↑ B D Thanopoulos BD, Tsaousis GS, Djukic M, Al Hakim F, Eleftherakis N, and Simeunovic S. Multicenter USA Amplatzer patent ductus arteriosus occlusion device trial: initial and one-year results. Heart. 2002; 87(3): 260–263. PDF
3. ↑ O'Rourke DJ, El-Khuffash A, Moody C, Walsh K, Molloy EJ. Patent ductus arteriosus evaluation by serial echocardiography in preterm infants. Acta Paediatr. 2008;97(5):574-8. Abstract
4. ↑ Lemmers P, Toet M, van Bel F. Impact of Patent Ductus Arteriosus and Subsequent Therapy With Indomethacin on Cerebral Oxygenation in Preterm Infants. Pediatrics. 2008; 21(1):142-147. Full Text

External Links

American Heart Association: Patent Ductus Arteriosus (PDA)