Patent Ductus Arteriosus (PDA) in Children: Causes, Symptoms and Treatment
Introduction
Patent ductus arteriosus is unusual among congenital heart conditions, because the vessel involved is not a malformation at all. It is a normal, necessary part of every baby's circulation before birth. The problem is only one of timing: it is supposed to close in the first days of life, and sometimes it does not.
It is one of the more common congenital heart findings, and among the most treatable.
Why the ductus exists before birth
An unborn baby does not breathe air. The lungs are fluid-filled and collapsed, and oxygen comes from the placenta instead. Sending large volumes of blood through lungs that are doing no work would be wasteful, so the fetal circulation includes a bypass: the ductus arteriosus, a short vessel connecting the pulmonary artery to the aorta. Blood leaving the right ventricle largely skips the lungs and goes straight out to the body.
At birth everything changes. The baby takes its first breath, the lungs expand, resistance in the lung circulation falls sharply, and oxygen levels rise. Rising oxygen and falling prostaglandin levels together signal the ductus to constrict and close, usually within 24 to 72 hours, becoming a small fibrous remnant.
What happens when it stays open
If it does not close, the pressure relationship is now reversed compared with fetal life. Pressure in the aorta is higher than in the pulmonary artery, so blood flows the other way — from the aorta back into the lung circulation. That blood has already been oxygenated. It travels through the lungs a second time unnecessarily, returns to the left side of the heart, and is pumped out again.
The result is extra volume passing repeatedly through the lungs and the left heart. A small duct adds very little. A large duct floods the lungs and overloads the left atrium and left ventricle.
Who is affected
- Premature babies. The mechanism that closes the duct is immature, and PDA is common in preterm infants — the more premature, the more likely.
- Babies with respiratory distress, where low oxygen levels discourage closure.
- Babies born at high altitude.
- Congenital rubella infection during pregnancy.
- Girls, roughly twice as often as boys.
Symptoms
Symptoms follow the size of the duct rather than its mere presence.
- Small PDA — usually no symptoms at all. Often found only because a doctor hears a murmur during a routine examination.
- Moderate to large PDA — rapid breathing, sweating during feeds, tiring quickly and taking long pauses while feeding, poor weight gain, and recurrent chest infections.
Feeding is the most sensitive early indicator in an infant. A baby who sweats on the forehead, breathes fast, and repeatedly stops to rest during a feed is telling you the heart is working hard.
On examination the classic finding is a continuous murmur, often described as machinery-like, because blood flows across the duct throughout the cardiac cycle rather than only during contraction. A wide pulse pressure and bounding pulses may also be present.
Diagnosis
Echocardiography is the definitive test. It confirms the duct, measures its diameter, shows the direction of flow, and — most importantly — measures the consequences: the size of the left atrium and left ventricle, and the pressure in the pulmonary artery. A chest X-ray may show a large heart and increased lung markings, and an ECG may show left-sided chamber enlargement.
Treatment
Medication
In premature infants, medicines that inhibit prostaglandin production — such as ibuprofen or indomethacin — can encourage the duct to close. This works in the newborn period and is not effective in older children.
Catheter closure
For most children beyond the newborn period, closure is performed through a catheter passed from a vessel in the groin, with a small device or coil deployed to seal the duct. There is no chest incision, recovery is quick, and hospital stay is usually short. This is the standard approach for suitable anatomy.
Surgical closure
Surgery remains important where the duct is very large, where the anatomy is unsuitable for a device, and in very small or premature infants. The duct is reached through a small incision on the left side of the chest — the heart itself is not opened and a heart–lung machine is not required. Results are excellent.
Why a significant PDA should not simply be left
Two reasons. First, the sustained extra flow enlarges the left heart and can lead to heart failure in infancy. Second, and more serious, long-standing high flow at high pressure damages the small arteries in the lungs. Over time this raises pulmonary artery pressure permanently, and once pulmonary vascular disease is established the duct can no longer be safely closed. The window for treatment closes.
This is precisely why an apparently well child with a known duct still needs proper cardiology assessment rather than reassurance alone.
After closure
Once a duct is closed, the outlook is normal in the great majority of children, with no restriction on activity. Follow-up confirms the closure is complete and that chamber sizes return to normal. Attention to dental hygiene is advised, particularly in the months after device closure.
Key points
- The ductus arteriosus is normal before birth and should close within days after it.
- If it stays open, oxygenated blood recirculates through the lungs, overloading the lungs and the left heart.
- Small ducts often cause no symptoms; larger ones show up as feeding difficulty, fast breathing and poor weight gain.
- Most are closed by catheter; surgery is used for large ducts and small infants.
- Leaving a significant duct untreated risks irreversible lung artery damage.
Related reading on this site: ventricular septal defect (VSD), tetralogy of Fallot, and the video PDA explained.
This article is general health education and is not medical advice about your child. If your baby is breathing rapidly, sweating with feeds, or gaining weight poorly, seek medical assessment. Treatment decisions are made by your paediatric cardiology team after individual evaluation.