Patent Ductus Arteriosus (PDA)
What is patent ductus arteriosus (PDA)?
Because the placenta does the work of exchanging oxygen (O2) and carbon dioxide (CO2) through the mother's circulation, the fetal lungs are not used for breathing. Instead of blood flowing to the lungs to pick up oxygen and then flowing to the rest of the body, the fetal circulation shunts (bypasses) most of the blood away from the lungs. In the fetus, blood is shunted from the pulmonary artery to the aorta through the ductus arteriosus. However, with the first breaths of air the baby takes at birth, the fetal circulation changes. A larger amount of blood is sent to the lungs to pick up oxygen. Because the ductus arteriosus is no longer needed, it normally begins to wither and close off.
What causes patent ductus arteriosus?Almost all children have a PDA present at birth. In some children, the PDA does not close, and remains open. Although exact reasons why this happens in some patients and not in others are not known, the most common association for a PDA is prematurity.
Why is patent ductus arteriosus a concern?When the ductus arteriosus stays open, oxygen-rich (red) blood passes from the aorta to the pulmonary artery, mixing with the oxygen-poor (blue) blood already flowing to the lungs. The blood vessels in the lungs have to handle a larger amount of blood than normal. How well the lung vessels are able to adapt to the extra blood flow depends on how big the PDA is and how much blood is able to pass through it from the aorta.
Extra blood causes higher pressure in the blood vessels in the lungs. The larger the volume of blood that goes to the lungs at high pressure, the more the lungs have to cope with this extra blood at high pressure.
Children will have increased difficulty breathing because of this extra blood flow to the lungs at high pressure. They may remain on the ventilator for a longer period of time, especially if premature in the first place, which often requires support from the ventilator. The support from the ventilator also may be high, due to this extra blood flow to the lungs.
Rarely, some older children may have too much blood going to the lungs that the lungs get damaged. This is uncommon, however, since most children will have been treated for their PDA before the lungs get damaged.
Often, the PDA may be "silent," that is, causing no symptoms. This is especially true in older patients (beyond the first few months of life).
What are the symptoms of patent ductus arteriosus?Babies with small PDAs may not have any observable symptoms, but those with a larger opening often do. The following are the most common symptoms of PDA. However, each baby may experience symptoms differently. Symptoms may include:
- strong pulses
- heart murmur
- enlarged heart size
- respiratory difficulty
- cyanosis (blue coloring)
How is patent ductus arteriosus diagnosed?In addition to a complete medical history and physical examination (especially listening to the heart for sounds of the murmur that are common with PDA), diagnostic procedures may include:
- electrocardiogram - a test that records the electrical activity of the heart, shows abnormal rhythms and, detects heart muscle damage.
- x-ray - a diagnostic test which uses invisible X-ray energy beams to produce images of internal tissues, bones, and organs onto film.
- echocardiogram (echo) - a noninvasive test that uses sound waves to produce a study of the motion of the heart's chambers and valves. An echo is the most common way that a PDA is diagnosed.
- cardiac catheterization (when other heart defects are suspected) - a test in which a small catheter (hollow tube) is guided through a vein or artery into the heart to help see any defects on X-ray.
Treatment of patent ductus arteriosus:Specific treatment for patent ductus arteriosus will be determined by your baby's physician based on:
- your baby's gestational age, overall health, and medical history
- extent of the disease
- your baby's tolerance for specific medications, procedures, or therapies
- expectations for the course of the disease
- your opinion or preference
In premature babies, aspirin-type drugs may be given. Both intravenous indomethacin and ibuprofen have been shown to be very effective in causing the PDA to close. Further studies are being done to find out if these will also help prevent PDA in babies at risk for the condition.
If a PDA does not respond to medication, or is due to causes other than prematurity, surgery may be needed. This surgery is called ligation and involves placing a suture around the ductus to close it.
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