Pediatric Cardiology • Parent Guide

Patent Ductus Arteriosus
(PDA)

A vessel that connects the heart’s two great arteries — essential before birth, but supposed to close within days. When it stays open, it becomes the condition called PDA.

📚 Rudolph’s Congenital Diseases of the Heart, 3rd Ed. (Ch. 6) | Moss & Adams, 10th Ed. (Ch. 31)
👨‍⚕️ Pediatric Cardiology

1 in 2000

Full-term births affected by PDA

~45%

Of premature infants (<1750g) have a significant PDA

48–72h

Time for spontaneous closure in healthy term newborns

Most common congenital heart defect overall

🫀 What Is PDA?

The Vessel That Should Have Closed

Before birth, the lungs don’t work — oxygen comes from the placenta. So the fetal body has a clever shortcut: the ductus arteriosus, a vessel that connects the pulmonary artery directly to the aorta, allowing blood to bypass the non-functioning lungs. This is completely normal fetal physiology.

At birth, when the baby takes its first breath, oxygen causes the ductus to constrict and seal shut — typically within 48–72 hours in a healthy full-term baby. Permanent fibrous closure is usually complete within 5–7 days (Rudolph, Ch. 6).

When this closure doesn’t happen, the ductus remains open — a Patent (open) Ductus Arteriosus. Blood continues to flow between the aorta and pulmonary artery in a way it shouldn’t postnatally.

💡

Why Does PDA Occur More in Premature Babies?

The ductus arteriosus in premature babies is less sensitive to oxygen (the main trigger for closure) and has higher levels of prostaglandin E₂ — a chemical that keeps the ductus open. The immature ductus also fails to develop the “intimal mounds” that seal it permanently. This is why PDA is far more common and clinically significant in premature infants.

Normal Circulation (After Birth) vs. Patent Ductus Arteriosus

✅ Normal After Birth — Ductus Closed	⚠️ With PDA — Ductus Remains Open
Aorta → Body (oxygenated) Pulmonary Artery → Lungs RV → Lungs (normal) LV → Aorta → Body (normal) Ductus Arteriosus SEALED SHUT ✓ Lungs receive correct blood flow	Aorta → Pulm. Artery (high-pressure shunt) PDA: Left → Right shunt ⚠️ Overloaded Lungs Extra blood floods the lungs RV and LV volume overloaded 🎵 “Machinery murmur” — continuous Left infraclavicular area

✅ Normal After Birth — Ductus Closed

⚠️ With PDA — Ductus Remains Open

Aorta → Body (oxygenated)
Pulmonary Artery → Lungs
RV → Lungs (normal)
LV → Aorta → Body (normal)

Ductus Arteriosus SEALED SHUT
✓ Lungs receive correct blood flow

Aorta → Pulm. Artery (high-pressure shunt)
PDA: Left → Right shunt

⚠️ Overloaded Lungs
Extra blood floods the lungs
RV and LV volume overloaded

🎵 “Machinery murmur” — continuous
Left infraclavicular area

PDA allows blood to shunt from the high-pressure aorta into the pulmonary artery, overloading the lungs and left heart. The characteristic continuous “machinery” murmur is heard in the left infraclavicular area.

🩺 Clinical Features

How Does PDA Present?

The clinical presentation depends critically on the size of the PDA and the age/maturity of the child:

Small PDA

Often detected incidentally. A characteristic “machinery murmur” — a continuous murmur heard in the left infraclavicular area that peaks around the second heart sound (Rudolph, p. 135). Child is otherwise well, with normal growth. No symptoms.

Risks: Endocarditis (rare but real). Usually does not affect exercise or lifespan.

Moderate PDA

Bounding pulses and wide pulse pressure (blood “bounces” in the circulation). Increased work of breathing. Child may tire easily with feeding. Left heart enlargement on echocardiogram.

Without treatment: risk of cardiac failure and pulmonary hypertension developing over months–years.

Large PDA (especially in preterms)

Significant respiratory distress syndrome, difficulty weaning from ventilator. Bounding peripheral pulses, hyperactive precordium. Pulmonary edema. Hepatomegaly. In extreme cases, Eisenmenger physiology (reversal of shunt).

Urgent treatment required.

⚠️

The PGE₁ Reversal — When an Open Ductus Saves a Life

In some critical congenital heart defects (pulmonary atresia, critical coarctation, HLHS, TGA), survival depends on the ductus staying open to provide blood to the lungs or body. In these situations, doctors give Prostaglandin E₁ (PGE₁) intravenously to deliberately keep the ductus open. Conversely, in preterm PDA, blocking prostaglandins with indomethacin or ibuprofen promotes closure.

PDA Management Pathway by Size & Context

PDA Detected
Echo + clinical assessment

▼

Preterm Infant (<37 weeks)

💊 Medical Rx
Indomethacin or Oral Ibuprofen
or Acetaminophen

If fails: Surgical ligation

Term / Older Child

Small: Observe — may close spontaneously

Moderate/Large: Close!
🔵 Catheter: Coil / Amplatzer device
🔴 Surgery (if catheter not possible)

Management of PDA differs by gestational age and size. Indomethacin works well in premature infants; term children with significant PDA need device closure.

🔧 Treatment

How Is PDA Treated?

1. Medical Treatment (Premature Babies)

Drugs that block prostaglandin synthesis promote ductal closure. According to Rudolph (Ch. 6), indomethacin given in the first 24–48 hours has 42% closure rate with first course, rising to 92% when combined with NOS inhibitors. Oral ibuprofen (equally effective, fewer renal side effects) and paracetamol/acetaminophen are also used. Furosemide (diuretic) helps manage fluid overload while waiting for closure.

2. Transcatheter Device Closure

The preferred approach for suitable anatomy in term infants and older children. A catheter is passed through a vein into the heart, and a coil or occluder device is deployed into the ductus to block blood flow. This is minimally invasive — no chest opening needed. The Gianturco coil and Amplatzer Duct Occluder are widely used devices. Success rate is excellent.

3. Surgical Ligation

Used when devices are too small to deploy (tiny premature babies) or when catheter closure is not feasible. A surgeon ties off the ductus through a small incision in the side of the chest (left thoracotomy). Highly effective. Video-assisted thoracoscopic surgery (VATS) can be done in larger infants with minimal scarring.

✅

Outcomes Are Excellent

Once a PDA is closed — by any method — the prognosis is excellent. The heart returns to normal function. Growth, development, and exercise tolerance are all normal. Long-term follow-up is required only to ensure no recurrence and to monitor for device-related issues (very rare).

📋 Reference

PDA at a Glance — Quick Reference

Feature	Small PDA	Moderate PDA	Large PDA
Murmur	Continuous “machinery” murmur	Loud continuous murmur	May soften as PA pressure rises
Pulses	Normal	Bounding, wide pulse pressure	Bounding pulses
Symptoms	None	Breathlessness on exertion	Respiratory distress, poor feeding, FTT
ECG	Normal	Left ventricular hypertrophy	Biventricular hypertrophy
Chest X-Ray	Normal	Cardiomegaly, pulmonary plethora	Markedly enlarged heart, pulmonary edema
Management	Observe / close if symptomatic or endocarditis risk	Close (device preferred)	Close urgently

❓ FAQ

Frequently Asked Questions

My newborn has been diagnosed with PDA. Is this serious?+

It depends on the size and context. In a healthy full-term newborn, a small PDA often closes on its own within the first few weeks. In a premature baby, a moderate-to-large PDA can be significant and may need treatment. Your cardiologist will assess the PDA by echocardiogram and decide if treatment is needed based on the size, your baby’s symptoms, and the clinical impact on the heart and lungs.

Can a PDA close on its own without treatment?+

Yes, small PDAs often do close spontaneously, sometimes over months to a few years. However, large or symptomatic PDAs in premature babies or older children are unlikely to close spontaneously and need treatment. A PDA that hasn’t closed by toddlerhood generally needs to be closed, as spontaneous closure in older children is unlikely.

What causes PDA — did I do something wrong during pregnancy?+

No. PDA is a congenital condition — meaning it develops during fetal development. Known associations include premature birth, rubella virus infection during pregnancy (the virus has a particular affinity for ductal tissue), and high altitude. Genetic factors may play a role. In most cases, there is no identifiable cause and no parent is at fault.

What is the “machinery murmur” doctors refer to in PDA?+

The PDA produces a characteristic murmur that is continuous — it runs through both the systolic and diastolic phases of the heartbeat (unlike most murmurs that occur only in one phase). It sounds like a machine running continuously — a rumbling, “churning” sound — which is why it’s called a machinery murmur. It is best heard at the upper left sternal border or left infraclavicular area. This murmur is very characteristic and often allows experienced cardiologists to diagnose PDA just by listening.

Is the device/catheter procedure for PDA safe?+

Yes — transcatheter device closure of PDA is one of the most successful and safest cardiac catheterization procedures. The success rate is very high and the risk of complications is very low in experienced centres. The child typically goes home the next day. The device (coil or disc occluder) remains permanently in the body and causes no long-term problems. No open-heart surgery is required.

What happens if PDA is left untreated?+

A small untreated PDA carries a small risk of bacterial endocarditis over a lifetime. A large untreated PDA leads to progressive pulmonary hypertension and eventually Eisenmenger syndrome — where the shunt reverses direction and becomes inoperable. This is why large PDAs should always be closed promptly. The good news is that with modern cardiology, PDA is almost always detected and treated well before reaching this stage.

Can my premature baby with PDA still breastfeed?+

Breastmilk is highly recommended for premature babies — it supports immune function and development. Feeding decisions (including amount, route, and frequency) are made by the NICU team based on your baby’s overall condition. A symptomatic PDA may mean more careful monitoring of feeds, but breastmilk itself is beneficial. Always discuss feeding plans with your neonatology and cardiology team.

🎯 Key Takeaways

PDA is the ductus arteriosus — a fetal blood vessel — that fails to close after birth. It is among the most common congenital heart defects.

Premature babies are especially vulnerable because their ductus is less responsive to oxygen and more sensitive to prostaglandins.

The classic sign is a continuous “machinery murmur” at the left infraclavicular area, with bounding pulses in moderate-to-large PDAs.

Treatment options include medical (indomethacin/ibuprofen for preterms), transcatheter device closure, or surgical ligation — all with excellent outcomes.

PGE₁ deliberately keeps the ductus open in duct-dependent heart lesions — so the same vessel can be life-saving or problematic depending on context.

Once successfully closed, outcomes are excellent with no long-term activity restrictions.