A PDA, or patent ductus arteriosus, is a heart condition where a blood vessel that normally closes shortly after birth stays open. Every baby has this vessel, called the ductus arteriosus, while in the womb. It serves as a bypass route that diverts blood away from the lungs, since a fetus gets oxygen from the placenta rather than by breathing. In healthy, full-term newborns, this vessel closes on its own within the first 12 to 24 hours of life. When it doesn’t close, the result is a PDA, which can range from harmless to serious depending on its size.
Why the Ductus Arteriosus Exists
Before birth, a baby’s lungs are filled with fluid and aren’t doing any work. The ductus arteriosus is a short, cone-shaped vessel connecting the pulmonary artery (which leads to the lungs) to the aorta (the body’s main artery). It lets most of the blood skip the lungs entirely and flow straight to the rest of the body, where it picks up oxygen from the placenta instead.
Two things keep this vessel open during pregnancy: low oxygen levels in the baby’s blood and chemical signals called prostaglandins produced by the placenta. The moment a baby is born and takes its first breath, both of those conditions change. Oxygen levels rise, the placenta is gone, and prostaglandin levels drop. The muscular walls of the ductus respond to these shifts by constricting, functionally shutting the vessel within hours. Over the next two to three weeks, the tissue permanently seals off and turns into a fibrous cord. If it hasn’t closed by about eight weeks, it generally won’t close on its own.
Who Gets a PDA
Premature birth is by far the biggest risk factor. Among babies born at 30 to 37 weeks, only about 10% still have an open ductus by day four of life. For extremely premature babies born at 24 weeks, that number jumps to over 90%. The earlier a baby is born, the less developed the muscular tissue in the ductus, and the less responsive it is to oxygen and the other signals that trigger closure.
Full-term babies can also have a PDA, though it’s much less common. In those cases, the cause isn’t always clear, but it can be associated with genetic conditions or maternal infections during pregnancy.
Signs and Symptoms
A very small PDA may produce no symptoms at all. These “silent” PDAs are sometimes discovered incidentally during a routine checkup when a doctor hears an unusual heart sound.
A larger PDA creates a more noticeable problem. Because the ductus connects a high-pressure vessel (the aorta) to a lower-pressure one (the pulmonary artery), blood flows backward into the lungs. This extra blood overloads the lungs and forces the heart to work harder. In infants, this can show up as:
- Fast or labored breathing
- Difficulty feeding and poor weight gain
- A characteristic heart murmur that sounds continuous, often described by doctors as a “machinery” murmur
- Frequent lung or heart infections
The heart murmur is often the first clue. Unlike many heart murmurs that occur only during one phase of the heartbeat, a PDA murmur runs continuously through both the pumping and resting phases, giving it that distinctive mechanical quality.
How a PDA Is Diagnosed
An echocardiogram, essentially an ultrasound of the heart, is the standard tool for confirming a PDA. It shows the open vessel directly, measures its size, and reveals the direction and volume of blood flowing through it. Doctors look at several markers to judge severity, including the size of the opening relative to the baby’s weight, whether the left side of the heart is enlarging from the extra workload, and whether blood flow in other arteries has reversed direction. These measurements help determine whether the PDA needs treatment or can be safely monitored.
Treatment With Medication
For premature infants, the first-line treatment is medication that mimics the natural closing process. The drugs used work by blocking prostaglandins, the same chemical signals that kept the ductus open before birth. Three medications are commonly used: indomethacin, ibuprofen, and acetaminophen (paracetamol). All three are given over a course of several days, sometimes repeated if the first round doesn’t work.
Success rates are similar across all three options, with cumulative closure rates (after up to two courses of treatment) ranging from about 68% to 77%. The key differences lie in side effects. Indomethacin and ibuprofen are both anti-inflammatory drugs that can temporarily stress the kidneys and, in rare cases, cause gastrointestinal bleeding. Acetaminophen appears gentler on the kidneys and gut, with one study showing no significant changes in kidney function or gastrointestinal complications after treatment. That safety profile has made it an increasingly popular choice, particularly for very fragile premature infants.
Procedures to Close a PDA
When medication doesn’t work, or when a PDA is found later in childhood or adulthood, a procedure is needed. There are two main approaches.
Catheter-Based Closure
This is the less invasive option and has become the preferred method in most cases. A thin tube is threaded through a blood vessel in the leg up to the heart, and a small plug or coil is placed inside the ductus to block blood flow. There’s no chest incision, hospital stays are shorter, and the mortality risk is extremely low. In a large study of neonates and infants at U.S. children’s hospitals, catheter closure had a 0% mortality rate.
Surgical Ligation
This involves a small incision between the ribs to reach the ductus and tie it off or cut it. Surgery is typically reserved for the youngest and most premature infants, whose blood vessels may be too small for a catheter device. Surgical patients tend to have longer hospital stays (roughly 3 to 4 extra days compared to catheter closure) and a small but measurable mortality risk of about 1.7%. The trend in recent years has been a steady shift toward catheter-based closure as devices have gotten smaller and techniques have improved.
What Happens After Closure
Recovery depends on which approach was used. After catheter-based closure, the American College of Cardiology recommends annual follow-up with echocardiograms for the first two years, then every three to five years after that. After surgical ligation with no remaining concerns, a child can often be discharged from cardiology care entirely after a routine post-procedure visit.
Very small, silent PDAs that were never treated may not need any follow-up at all. Small PDAs that are being monitored rather than treated typically only require a checkup every two to three years to make sure the heart chambers aren’t enlarging from the extra blood flow.
Risks of Leaving a Large PDA Untreated
A small PDA can be completely harmless for a lifetime. A large one is a different story. Years of excess blood flowing into the lungs gradually raises the pressure in the pulmonary arteries. Over time, this can cause permanent damage to the blood vessels in the lungs, a condition called pulmonary hypertension. In severe cases, the pressure in the lungs eventually exceeds the pressure in the rest of the body, reversing the direction of blood flow through the ductus. This is known as Eisenmenger syndrome, and it’s irreversible.
Eisenmenger syndrome causes chronic low oxygen levels, cyanosis (a bluish tint to the skin), fainting, and eventually heart failure. A case report published in Circulation described a 19-year-old with an unrepaired PDA who developed severe pulmonary hypertension with mean pulmonary pressures nearly five times normal, ultimately leading to respiratory failure. Cases like this are rare in countries with routine newborn screening, but they underscore why significant PDAs are treated early rather than left to chance.