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 an important purpose during pregnancy by routing blood away from the lungs, since the baby gets oxygen from the placenta instead. In healthy, full-term newborns, this vessel constricts and functionally closes within 12 to 24 hours of birth, with permanent closure happening within two to three weeks. When it doesn’t close, extra blood flows into the lungs and forces the heart to work harder.
Why the Ductus Arteriosus Exists
Before birth, a baby’s lungs aren’t doing anything. Oxygen comes from the mother through the placenta, so blood doesn’t need to pass through the lungs to pick up oxygen. The ductus arteriosus is a short vessel connecting the two major arteries leaving the heart, and it creates a detour that sends blood straight to the body, skipping the lungs entirely.
Two things keep this vessel open during pregnancy: low oxygen levels in the baby’s blood and hormone-like substances called prostaglandins, which the placenta produces. The moment a baby is born and takes that first breath, both of those conditions change at once. The lungs fill with air, oxygen levels rise, and the placenta (the source of prostaglandins) is gone. The muscular wall of the ductus arteriosus is sensitive to oxygen, and the rise in oxygen triggers it to squeeze shut. When this process doesn’t happen properly, the vessel remains open, or “patent,” and blood that should flow to the body leaks back into the lungs.
How Size Determines Severity
Not all PDAs are the same. The size of the opening makes a significant difference in how much it affects a child’s health. A small PDA may cause no symptoms at all. The heart and lungs don’t have to work noticeably harder, and the only sign might be an unusual heart murmur that a doctor picks up with a stethoscope. Small PDAs often close on their own within the first few months of life.
A moderate or large PDA is a different situation. The wider the opening, the more blood floods back into the lungs, raising pressure in the lung arteries. Research has shown a direct relationship: children with moderate-sized openings tend to develop moderate increases in lung artery pressure, while those with large openings are significantly more likely to develop severe pressure elevations. That extra workload on the heart is what drives symptoms and, if left untreated, can lead to serious complications.
Signs to Watch For
A small PDA may never produce visible symptoms. Larger openings, however, tend to show up as a cluster of signs that reflect the heart struggling to keep up with the extra work:
- Poor feeding and slow weight gain. Babies with a significant PDA often tire out during feedings and don’t gain weight the way they should.
- Fast or labored breathing. Because the lungs are receiving too much blood flow, breathing may be consistently rapid, sometimes with visible effort.
- Sweating during feeding or crying. Activities that should be routine become physically taxing.
- Easy fatigue and rapid heart rate. Older infants and toddlers may seem unusually tired or winded during normal activity.
In severe cases, these symptoms can progress to heart failure, which shows up as gasping breaths and a failure to gain weight despite adequate feeding. This is a serious situation that needs prompt medical attention.
How PDA Is Diagnosed
The first clue is usually a heart murmur. PDA produces a distinctive type of murmur, sometimes described as “machinery-like,” that a pediatrician can hear with a stethoscope. From there, the primary diagnostic tool is an echocardiogram, an ultrasound of the heart. This painless test shows blood flowing through the heart in real time and can reveal whether there’s a persistent opening, how large it is, and whether pressure in the lung arteries is elevated.
A chest X-ray may be used to check whether the heart appears enlarged or whether the lungs show signs of extra blood flow. An electrocardiogram (EKG) records the heart’s electrical activity and can reveal whether the heart is being strained. In most cases, the echocardiogram alone provides enough information to guide decisions. Cardiac catheterization, a more invasive test where a thin tube is threaded into the heart, is typically reserved for children who also have other heart conditions.
If a PDA is confirmed, your child will likely be referred to a pediatric cardiologist, a doctor who specializes in children’s heart conditions.
Treatment Options
Treatment depends on the size of the PDA, the child’s age, and whether symptoms are present.
Watchful Waiting
A small PDA that isn’t causing symptoms doesn’t necessarily need to be closed. The American Heart Association notes that small PDAs don’t make the heart and lungs work harder and may not require surgery or other intervention. These children do need periodic follow-up visits with a cardiologist to make sure the opening isn’t growing or causing problems over time, but many live completely normal, active lives without any restrictions on physical activity.
Medication
In premature babies, doctors may try to close the PDA with medication before considering any procedure. These drugs work by blocking the same prostaglandins that kept the vessel open in the womb. Three medications are commonly used, and clinical trials have found they work at similar rates, closing the ductus in roughly 70 to 80 percent of preterm infants. Some studies have reported success rates as high as 95 to 100 percent. If the first course doesn’t work, a second round may be tried before moving to a procedural option.
Catheter-Based Closure
This is the most common approach for children who need their PDA closed. A thin, flexible tube is guided through a blood vessel in the leg up to the heart, where a small device or coil is placed inside the open ductus to block blood flow. There’s no open-chest surgery involved, and hospital stays are short, typically around four days. This approach works well for small to moderate openings and is generally performed once a child is large enough to safely accommodate the catheter.
Surgical Ligation
Surgery is reserved for larger openings or for very young or very small infants who aren’t candidates for catheter-based closure. The surgeon makes a small incision between the ribs and ties off or clips the open vessel. Infants who need intervention early in life, particularly those in the first year, are more likely to undergo surgical ligation. In one study, the average opening in children who needed surgery was about 8.5 mm, compared to 3.6 mm in those treated with a catheter device.
What Happens If PDA Goes Untreated
A small PDA that causes no symptoms can be safely monitored. But a moderate or large PDA that’s left untreated can lead to serious problems over time. The constant extra blood flow into the lungs gradually damages the lung arteries, causing them to thicken and stiffen. This is called pulmonary hypertension, and it forces the right side of the heart to pump against increasing resistance.
If the damage to the lung arteries becomes severe enough, it can eventually reverse the direction of blood flow through the PDA, sending oxygen-poor blood out to the body instead of to the lungs. This irreversible condition, known as Eisenmenger syndrome, is the most feared complication of untreated PDA. At that point, closing the ductus is no longer an option because the lung damage has become permanent. Heart failure and infection of the vessel lining are additional risks of leaving a significant PDA open. This is why timely evaluation matters: catching and treating a hemodynamically significant PDA before lung damage sets in leads to far better outcomes.
Recovery and Long-Term Outlook
The outlook after PDA closure is excellent for most children. After a catheter-based procedure, children typically go home within a few days. The heart, which has been working overtime to compensate for the extra blood flow, begins to remodel itself once the shunt is eliminated. Echocardiographic studies show that heart size and function generally return to normal within about six months.
Children with a small, unrepaired PDA or a successfully closed PDA can participate in normal physical activities without restriction. Periodic follow-up with a cardiologist is still recommended, particularly in the first year after closure, to confirm the device is in place and the heart has recovered fully. For the vast majority of children, PDA is a one-time problem: once closed, it stays closed, and long-term heart function is normal.