Persistent fetal connection between aorta and pulmonary artery producing a continuous machinery murmur and L-to-R shunt.
Also known as: PDA, patent ductus, ductus arteriosus
Overview
Persistence beyond the neonatal period of the ductus arteriosus, the fetal vascular connection between the proximal descending aorta (just distal to the left subclavian artery) and the main pulmonary artery near its bifurcation. After birth the ductus normally constricts and closes within 24-72 hours; failure to close results in a left-to-right shunt of variable hemodynamic significance.
Epidemiology
Accounts for ~5-10% of congenital heart disease in term infants; much higher prevalence in preterm infants (up to 60% in those <28 weeks). Female predominance ~2:1 in term infants. Strong association with maternal rubella and high altitude.
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High-altitude birth (lower partial pressure of oxygen impairs closure)
Female sex
Trisomy 21, fetal alcohol syndrome, maternal phenytoin use
Family history of congenital heart disease
Pathophysiology
In utero, prostaglandin E2 (PGE2) maintains ductal patency. After birth, rising arterial oxygen tension and declining PGE2 levels promote constriction and anatomical closure. A persistent PDA allows blood flow from the higher-pressure systemic circulation (aorta) into the lower-pressure pulmonary circulation. Chronic volume overload leads to LA and LV dilation, pulmonary overcirculation, and over time pulmonary vascular disease. Large untreated shunts can produce Eisenmenger physiology with shunt reversal and differential cyanosis (cyanotic lower extremities with pink upper extremities).
Clinical presentation
Symptoms
Small PDA: asymptomatic, found incidentally on auscultation
Moderate-to-large PDA in infancy: poor feeding, diaphoresis with feeds, failure to thrive, tachypnea, recurrent pulmonary infections
Untreated through childhood: exertional dyspnea, palpitations, fatigue
Eisenmenger physiology (years later): differential cyanosis and clubbing of toes (not fingers), exercise intolerance
Signs / physical exam
Continuous 'machinery' or 'rolling thunder' murmur at left infraclavicular area / upper left sternal border (Gibson murmur), peaking around S2
Wide pulse pressure with bounding (water-hammer) peripheral pulses
Hyperdynamic precordium with displaced apical impulse if large
Mid-diastolic apical rumble from increased mitral inflow in large shunts
Differential cyanosis (post-ductal SpO2 lower than pre-ductal) in shunt reversal
Classic findings
Continuous machinery murmur with wide pulse pressure and bounding pulses in a child; differential cyanosis is pathognomonic when shunt reversal develops.
Differential diagnosis
Ventricular septal defect (VSD) — Harsh holosystolic murmur at LLSB, no diastolic component; CXR may look similar (increased pulmonary vascularity)
Atrial septal defect (ASD) — Fixed split S2 with mid-systolic flow murmur, no continuous machinery quality
Aortopulmonary window — Rare, large, near-obligate biventricular failure in infancy; continuous murmur but echo distinguishes
Coronary AV fistula — Continuous murmur but lower intensity and different location; coronary angiography or echo confirms
Venous hum (innocent) — Continuous murmur over neck/upper chest in children; eliminated by jugular compression or supine position
Ruptured sinus of Valsalva aneurysm — Sudden onset continuous murmur in older patient, often with acute decompensation
Truncus arteriosus — Single great artery overrides VSD; cyanosis and HF in infancy
Diagnostic workup
Labs
BMP, CBC
Genetic evaluation if features suggest a syndrome (Down, rubella exposure history)
Imaging
Transthoracic echocardiography with color Doppler — diagnostic; visualizes the ductus, direction and velocity of shunt, and chamber size
ECG: normal if small; LA enlargement and LVH with large shunts; biventricular hypertrophy with pulmonary HTN
Cardiac catheterization with measurement of pulmonary vascular resistance if pulmonary hypertension is suspected before closure
Diagnostic algorithm
Feature
PDA
VSD
ASD
Murmur timing
Continuous (machinery)
Holosystolic
Mid-systolic flow
Location
Left infraclavicular
LLSB
ULSB
S2
Often normal or paradoxically split
Normal or loud P2
Wide and fixed split
Pulse pressure
Wide, bounding pulses
Normal
Normal
Cyanosis pattern (if Eisenmenger)
Differential (lower limbs only)
Generalized
Generalized
First-line closure
Transcatheter device (term); NSAIDs (preterm)
Surgical / catheter device
Surgical / catheter device (secundum)
Distinguishing PDA from VSD and ASD on physical exam and management.
Treatment
First-line
Premature infants (hemodynamically significant PDA): supportive care first (fluid restriction, diuretics, optimize ventilation). Pharmacologic closure with indomethacin or ibuprofen (COX inhibitors) — first-line; acetaminophen is an alternative when COX inhibitors are contraindicated
Term infants and older children with persistent PDA: percutaneous transcatheter device closure (coil or occluder) is preferred over surgery for nearly all sizes and ages beyond infancy
Surgical ligation: reserved for very large PDAs, distorted anatomy unsuitable for catheter closure, or when catheter access is not feasible
Preterm infant
Conservative management is often appropriate for many asymptomatic PDAs (many close spontaneously)
Hemodynamically significant PDA: indomethacin or ibuprofen course; consider acetaminophen if NSAID contraindicated
Refractory or contraindicated medical therapy: surgical ligation or catheter closure
Term infant / child / adult
Silent PDA (no murmur, incidental echo finding): no closure required per most guidelines
Reassess pulmonary vascular resistance prior to closure in older patients
Second-line / adjunct
Endocarditis prophylaxis is NOT routinely indicated for unrepaired PDA per current AHA guidelines (only for unrepaired cyanotic CHD, repaired CHD with residual defect adjacent to prosthetic material, or first 6 months after device/repair)
Pulmonary vasodilator therapy (sildenafil, bosentan) for Eisenmenger physiology — closure contraindicated once pulmonary vascular disease has developed
Heart-lung transplant consideration in severe Eisenmenger syndrome
Complications
Heart failure from chronic volume overload
Pulmonary hypertension and Eisenmenger syndrome
Infective endarteritis (uncommon but classically reported on the pulmonary end of the ductus)
Aneurysmal dilatation of the ductus (rare)
Failure to thrive in infancy
PANCE pearls
PGE1 (alprostadil) is given to maintain ductal patency in neonates with ductal-dependent lesions (transposition, hypoplastic left heart, severe coarctation, tricuspid atresia) — the opposite indication of indomethacin.
Differential cyanosis (pink upper, blue lower extremities) is the hallmark of right-to-left shunting through a PDA with elevated pulmonary pressures.
Maternal rubella in the first trimester is classically associated with PDA (and cataracts, deafness).
Wide pulse pressure and bounding pulses in an infant with a continuous murmur should prompt urgent echocardiography.
Closure is contraindicated once severe pulmonary vascular disease has developed because the PDA serves as a pop-off valve.
References
AHA/ACC 2018 — 2018 AHA/ACC Guideline for the Management of Adults with Congenital Heart Disease (Stout et al., Circulation 2019)
AHA 2007 (updated) — Prevention of Infective Endocarditis: Guidelines from the AHA (Wilson et al., Circulation 2007; updated 2021)
Cochrane Review — Ibuprofen versus indomethacin for closure of PDA in preterm infants (Ohlsson et al., Cochrane Database 2020)
Cochrane Review — Paracetamol (acetaminophen) for PDA closure in preterm or low birth weight infants (Ohlsson and Shah, Cochrane Database 2020)
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