Patent Ductus Arteriosus (PDA) : Clinical Case Discussion & Key Points
Model Case Presentation
Patient Demographics
Name: Baby Ananya, Age: 3 months, Gender: Female, Informant: Mother (Reliable)
Chief Complaints
- Fast breathing and difficulty in feeding — 6 weeks
- Poor weight gain since birth
- Recurrent chest infections — 2 episodes in 2 months
History Summary
Baby Ananya was born at 34 weeks of gestation by LSCS, cried immediately. Birth weight 1.8 kg. She had required NICU admission for 3 weeks. Discharged on oxygen. Since discharge, mother notices rapid breathing especially during feeds, with excessive sweating from the forehead. Baby feeds for 5–7 minutes then stops, breathes rapidly, then resumes (suck-rest-suck cycle). No episodes of blue discoloration of lips or limbs noted. No squatting spells. No edema. Mother had a fever with rash in the first trimester — not evaluated. No family history of CHD.
Antenatal: Preterm labour managed in hospital. No maternal diabetes or drug intake noted.
Examination Summary
| Parameter | Finding | Significance |
|---|---|---|
| Weight | 3.1 kg | Failure to Thrive (expected ~5.5 kg for 3 months) |
| RR | 60/min | Tachypnea |
| HR | 155/min | Tachycardia |
| SpO2 (upper limb) | 98% | Normal |
| SpO2 (lower limb) | 98% | No differential cyanosis (rules out Eisenmenger) |
| Pulse character | Bounding/Collapsing | Wide pulse pressure — diastolic runoff into PA |
| Cyanosis/Clubbing | Absent | Acyanotic lesion |
Precordium: Hyperactive precordium. Apex beat at 5th ICS, anterior axillary line (displaced — cardiomegaly). Systolic thrill at left upper sternal border (2nd ICS).
Auscultation: Loud, harsh, Grade 4/6 continuous "machinery" murmur (Gibson's murmur) at the left infraclavicular area / 2nd left ICS, radiating to the back. Murmur envelops S2. Loud P2. Mid-diastolic flow murmur at apex (large shunt, relative mitral stenosis). S3 gallop present.
Other systems: Bilateral basal crepitations (pulmonary venous congestion). Hepatomegaly 4 cm below RCM (CCF).
✅ Complete Diagnosis
Acyanotic Congenital Heart Disease — Large Patent Ductus Arteriosus with Left-to-Right Shunt, in Congestive Heart Failure with Failure to Thrive and Moderate Pulmonary Arterial Hypertension, in a preterm infant, likely secondary to Congenital Rubella.
📝 History — Exam Q&A
PDA is the persistence of the fetal communication — the ductus arteriosus — between the main pulmonary artery (or left pulmonary artery at its origin) and the descending thoracic aorta (just distal to the origin of the left subclavian artery), beyond the neonatal period. Normally, it closes functionally within 24–72 hours of birth and anatomically within 2–3 weeks of life.
PDA accounts for 5–10% of all CHDs. Incidence in term infants is approximately 1 in 2000 live births. In preterm infants, incidence is much higher: ~20% in infants <32 weeks and up to 60–70% in infants <28 weeks of gestation. There is a female predominance (F:M = 2:1) in term infants. This gender ratio is not seen in preterm PDA.
- Prematurity — most common cause; immature ductal smooth muscle less responsive to oxygen-induced constriction
- Congenital Rubella syndrome — most common infection causing PDA (classic association)
- High altitude — chronic hypoxia prevents ductal closure
- Perinatal asphyxia — hypoxia and acidosis impair ductal constriction
- Associated CHDs: PDA is commonly seen alongside VSD, CoA, TOF, TGA
- Chromosomal anomalies (Trisomy 21, etc.)
In PDA, aortic pressure exceeds pulmonary artery pressure throughout the cardiac cycle → continuous left-to-right shunt from aorta to pulmonary artery. This leads to:
- Pulmonary overcirculation: Increased pulmonary blood flow → pulmonary venous congestion → tachypnea, crepitations, recurrent LRTI
- Left heart volume overload: Increased pulmonary venous return → LA and LV dilation → CCF
- Diastolic runoff: Blood exits aorta into PA in diastole → wide pulse pressure → bounding/collapsing pulses
- Reduced systemic perfusion: Blood "stolen" into pulmonary circulation → FTT, poor feeding
- Pulmonary arterial hypertension: In large/untreated PDA, elevated pulmonary blood flow → pulmonary vascular remodeling
| Promotes Opening (Dilation) | Promotes Closure (Constriction) |
|---|---|
| Prostaglandins (PGE2, PGI2) | Oxygen (↑ PaO2 after birth) |
| Hypoxia / Low PaO2 | Indomethacin / Ibuprofen / Acetaminophen |
| Acidosis | Alkalosis |
| Prematurity (immature smooth muscle) | Endothelin-1 |
| Exogenous PGE1 (Alprostadil — used therapeutically) | COX inhibitors (block prostaglandin synthesis) |
💡 Clinical Application
PGE1 (Alprostadil) is used to keep the ductus open in duct-dependent congenital heart lesions (e.g., pulmonary atresia, critical aortic stenosis, hypoplastic left heart syndrome) as a life-saving measure until surgery.
| Feature | Preterm PDA | Term PDA |
|---|---|---|
| Cause | Immature ductal smooth muscle | Structural/genetic/Rubella |
| Presentation timing | First days of life (often day 3–7) | Weeks to months |
| Spontaneous closure | Likely (especially >28 wks) | Rarely after 3 months |
| Medical closure (Indomethacin/Ibuprofen) | Effective (~80%) | NOT effective |
| Murmur | Often only systolic (PVR still high) | Classic continuous machinery murmur |
| Pulmonary complications | Worsens RDS, BPD risk | Pulmonary plethora, PAH |
| Type | Features |
|---|---|
| Silent PDA | Tiny; detected only on echo (color Doppler); no murmur, no symptoms |
| Small PDA | Continuous murmur; no symptoms; normal heart size; Qp:Qs <1.5:1 |
| Moderate PDA | Symptoms present; mild cardiomegaly; Qp:Qs 1.5–2:1 |
| Large PDA | CCF, FTT, PAH; gross cardiomegaly; Qp:Qs >2:1; bounding pulses |
- No cyanosis in upper limbs — Rules out Eisenmenger (in Eisenmenger PDA, only lower limbs are cyanosed)
- No differential cyanosis — rules out shunt reversal
- No maternal rubella in first trimester
- No maternal drug intake (e.g., phenytoin, valproate)
- Gestational age — preterm vs term alters management
- No NICU admission for RDS (preterm infants) — severity of prematurity-related complications
🩺 Examination — Exam Q&A
The murmur of PDA is a continuous "machinery" murmur, also called Gibson's murmur. It is:
- Timing: Continuous — present throughout systole and diastole, enveloping (peaking around) S2
- Character: Harsh, "machinery-like" or "rolling thunder" quality
- Location: Best heard at the left infraclavicular area or left upper sternal border (2nd ICS)
- Radiation: Radiates to the back (left interscapular area) and axilla
- Grade: Usually Grade 3–4/6
💡 Key Pearl
In neonates and preterm infants, the murmur may be only systolic (not continuous) because pulmonary vascular resistance is still elevated and the diastolic pressure gradient is low. The classic continuous murmur develops as PVR falls over weeks.
The pulse is bounding / collapsing (also called water-hammer pulse or Corrigan's pulse), with a wide pulse pressure.
Mechanism: The ductus allows aortic blood to run off into the low-resistance pulmonary vasculature throughout diastole. Diastolic pressure falls disproportionately (diastolic runoff) while systolic pressure is maintained by compensatory LV stroke volume increase → wide pulse pressure → bounding, rapidly rising and falling pulse.
- Wide pulse pressure: >25 mmHg in neonates, >40 mmHg in older children
- Pistol-shot sound over femoral artery (Traube's sign) may be heard
Differential cyanosis = cyanosis and clubbing of the lower limbs only, with normal upper limb SpO2 and no upper limb clubbing.
Mechanism: When Eisenmenger syndrome develops in PDA, shunt reversal occurs — deoxygenated blood from the pulmonary artery enters the descending aorta (post-ductal). The head, neck, and upper limbs (supplied by branches arising proximal to the ductus — from the aortic arch) receive oxygenated blood. The lower body receives desaturated blood → lower limb cyanosis and clubbing.
🚨 Pathognomonic Sign
Differential cyanosis (lower limb cyanosis + upper limb clubbing absent) is pathognomonic of Eisenmenger syndrome due to PDA. It distinguishes PDA Eisenmenger from other causes of Eisenmenger.
- Inspection: Prominent / bulging left precordium (chronic LV volume overload), visible pulsations
- Apex beat: Displaced laterally (5th–6th ICS, anterior axillary line) — LV cardiomegaly. Character: hyperdynamic (volume overload)
- Thrill: Systolic thrill at left upper sternal border (2nd ICS) — due to turbulent systolic flow
- Parasternal heave: Present if RV also enlarges (secondary PAH)
- Auscultation: Continuous machinery murmur at LUSB; loud P2 (PAH); mid-diastolic flow murmur at apex (large shunt); S3 gallop (CCF)
Same as in large VSD — indicates a large left-to-right shunt (Qp:Qs >2:1). Massive pulmonary venous return floods the LA, which must pump a large volume through a normal-sized mitral valve → relative mitral stenosis → flow murmur. It is a marker of hemodynamic significance requiring intervention.
As PAH progresses and PVR approaches systemic levels:
- The diastolic component of the murmur disappears first (pressure gradient in diastole is lost first) → murmur becomes systolic only
- Eventually, even the systolic component disappears (equalization of pressures)
- A Graham-Steell murmur (early diastolic murmur of pulmonary regurgitation due to PAH-related pulmonary valve annular dilatation) may appear
- Loud, single or closely split S2 with dominant P2
| Condition | Location / Features |
|---|---|
| PDA | LUSB / left infraclavicular; envelops S2; bounding pulse |
| Aortopulmonary window | Similar to PDA; no bounding pulse; confirmed by echo |
| Coronary AV fistula | Anywhere over precordium; loud, superficial |
| Ruptured sinus of Valsalva aneurysm | Sudden onset; right or left sternal border; older patients |
| Venous hum | Right infraclavicular; disappears on lying down / neck vein compression; INNOCENT murmur |
| Systemic AV fistula | Over fistula site |
| Mammary souffle | Pregnant/lactating women; disappears on pressure |
💡 How to distinguish PDA from Venous Hum
Venous hum disappears on lying down or compression of the internal jugular vein on the same side. PDA murmur persists in all positions.
- Bounding/collapsing pulse — at radial, brachial, or carotid artery
- Wide pulse pressure — measurable by BP
- Prominent carotid pulsations — "carotid shudder"
- Head bobbing (de Musset's sign) — in very large shunts (similar to aortic regurgitation)
- Capillary pulsation (Quincke's sign) — in nail beds
- Pistol shot sound over femoral artery (Traube's sign)
- Failure to thrive, pallor (in CCF)
🔬 Investigations — Exam Q&A
- Cardiomegaly — CT ratio >0.55 in infants; predominantly LV enlargement
- Pulmonary plethora — increased pulmonary vascular markings to the lung periphery
- Prominent main pulmonary artery segment
- Prominent ascending aorta and aortic knuckle — unlike VSD where aorta is small (this is a differentiating feature)
- LA enlargement — elevation of left main bronchus, double shadow on right border
- In Eisenmenger: pruning of peripheral pulmonary vessels (peripheral vascular markings reduced despite enlarged central pulmonary arteries)
| PDA Size | ECG Pattern |
|---|---|
| Small (silent) | Normal ECG |
| Moderate | LVH — tall R waves in V5–V6, deep S in V1; LA enlargement (broad/notched P wave) |
| Large | Biventricular hypertrophy + LA enlargement |
| Eisenmenger PDA | Pure RVH — right axis deviation, dominant R in V1, deep S in V5–V6 |
2D Echocardiography with Color Doppler — It is the investigation of choice and provides:
- Direct visualization of the ductus (parasternal short-axis or suprasternal view)
- Size of PDA — minimal diameter at pulmonary artery end
- Direction of shunt — left-to-right (normal), bidirectional, or right-to-left (Eisenmenger)
- LA:Ao ratio — ratio of left atrial to aortic root dimension; >1.3–1.4 indicates significant shunt
- PA pressure estimation — from TR jet velocity or PDA flow velocity
- LV function and dimensions — volume overload pattern
- Associated cardiac anomalies
The LA:Ao ratio (left atrial to aortic root diameter ratio) measured on echocardiography (M-mode or 2D parasternal long-axis view) is a surrogate marker of the degree of left-to-right shunt in PDA.
- Normal: LA:Ao ≈ 1.0
- >1.3–1.4: Indicates a hemodynamically significant shunt — LA is dilated due to volume overload from pulmonary venous return
- Used in preterm infants to guide need for treatment
Cardiac catheterization is not routinely required for diagnosis (echo is sufficient). Indications:
- Assessment of pulmonary vascular resistance (PVR) when PAH is suspected and operability is in question
- Vasoreactivity testing — using 100% O2 or inhaled nitric oxide to determine if PAH is reversible (operable)
- Interventional (therapeutic): Transcatheter device closure of PDA — most common indication today
- Echo findings inconclusive for PA pressure or anatomy
Operability criteria: PVR <8 Wood units, PVR/SVR ratio <0.66.
- CBC: Polycythemia (Eisenmenger), anemia (CCF/poor nutrition), thrombocytopenia (contraindication for indomethacin)
- Serum electrolytes, renal function: Before indomethacin; diuretic monitoring
- Blood glucose / calcium: In neonates
- TORCH screen: If maternal history suggests rubella or other infections
- BNP/NT-proBNP: Elevated in hemodynamically significant PDA; useful in preterm infants
- SpO2 in all four limbs: To detect differential cyanosis (pre- vs post-ductal)
💊 Management — Exam Q&A
Management depends on age of patient (preterm vs term), size of PDA, and hemodynamic significance:
- Conservative (watchful waiting): Silent / small PDAs — may close spontaneously; restrict fluids in preterm
- Medical management: CCF treatment + pharmacological closure (indomethacin/ibuprofen) — mainly in premature infants
- Transcatheter (device) closure: Procedure of choice in eligible patients (>6 months, >6 kg typically)
- Surgical ligation/division: For those not amenable to device closure, or very small premature infants
- Diuretics: Furosemide (1–2 mg/kg/day) ± Spironolactone (1–2 mg/kg/day) — reduce pulmonary congestion
- ACE Inhibitor: Enalapril / Captopril — reduces afterload; decreases left-to-right shunt
- Digoxin: Mild inotropic support (less commonly used now)
- High-calorie feeds: 120–150 kcal/kg/day; frequent small feeds or NG tube supplementation
- Treat infections: Prompt antibiotic therapy for LRTI
- Correction of anemia if present
🚨 Important
Medical therapy is a bridge to definitive intervention, not a cure for term-infant PDA. Pharmacological closure with COX inhibitors is not effective in term infants.
Mechanism: Prostaglandins (PGE2) maintain ductal patency. COX (cyclooxygenase) inhibitors block prostaglandin synthesis → reduction in PGE2 → ductal smooth muscle constriction → closure.
| Drug | Dose | Route | Notes |
|---|---|---|---|
| Indomethacin | 0.1–0.2 mg/kg q12–24h × 3 doses | IV | First-line; causes renal vasoconstriction — monitor urine output; oliguria is common |
| Ibuprofen | 10 mg/kg first dose, then 5 mg/kg × 2 doses q24h | IV / Oral | Less renal and gut side effects than indomethacin; equally effective |
| Paracetamol (Acetaminophen) | 15 mg/kg q6h × 3–7 days | IV / Oral | Newer option; mechanism: inhibits peroxidase activity of PGH2 synthase; better GI and renal profile |
Contraindications to indomethacin/ibuprofen:
- Renal failure / oliguria (urine output <1 ml/kg/h)
- Thrombocytopenia (<60,000/µL) or active bleeding
- Necrotizing enterocolitis (NEC) or suspected gut ischemia
- Hyperbilirubinemia (indomethacin displaces bilirubin from albumin)
- Intracranial hemorrhage
Efficacy: ~70–80% closure rate in premature infants <32 weeks with appropriate timing.
- Hemodynamically significant PDA — CCF, FTT, recurrent LRTI, PAH
- Moderate-large PDA with Qp:Qs >1.5:1
- Large PDA not responding to medical management
- Developing PAH (before reaching Eisenmenger threshold)
- Silent or small PDA — routine closure is controversial; however, many centers close to prevent infective endarteritis
- Failed pharmacological closure in preterm infants with hemodynamic compromise
Ideal timing: After 6 months of age for device closure (weight >6 kg preferred). Surgical closure can be done even in small premature infants.
Transcatheter closure is currently the procedure of choice for most PDAs in children >6 months / >6 kg. A catheter is introduced via the femoral vein/artery and a closure device is deployed across the ductus under fluoroscopic and echocardiographic guidance.
| Device | Best For |
|---|---|
| Amplatzer Ductal Occluder (ADO I) | Moderate-large PDAs; most widely used |
| ADO II | Small / tubular PDAs, also works in retrograde approach |
| Gianturco coils | Small PDAs (<2.5 mm minimum diameter) |
| Occlutech PDA Occluder | Various sizes |
| Piccolo Occluder | Very small premature infants (<700 g); transcatheter delivery via 4F sheath |
Advantages: No sternotomy, no cardiopulmonary bypass, shorter hospital stay, excellent safety profile.
Surgical ligation/division via left posterolateral thoracotomy (no cardiopulmonary bypass required). Approaches:
- Ligation alone: Suture ligation of the ductus; small risk of recanalization
- Division and suture closure: Gold standard surgical method — permanent, no recanalization
- Video-Assisted Thoracoscopic Surgery (VATS): Minimally invasive; clips applied to the ductus; preferred in many centers for older children
Indications for surgery over device closure: Very small premature infants (<1 kg) with hemodynamically significant PDA, PDAs too large or unfavorably shaped for devices, failed device closure.
Complications of surgery: Recurrent laryngeal nerve palsy (hoarseness), phrenic nerve injury, chylothorax, pneumothorax, rarely inadvertent ligation of left pulmonary artery or aorta.
- Eisenmenger Syndrome — irreversible PAH with right-to-left shunt reversal → differential cyanosis
- Infective Endarteritis (not endocarditis, because the ductus is arterial tissue — technically endarteritis)
- Congestive Heart Failure
- Failure to Thrive
- Recurrent LRTI (pneumonia, bronchiolitis)
- Pulmonary Arterial Aneurysm — from turbulent jet injury
- In preterms: Worsening of Respiratory Distress Syndrome (RDS), increased risk of Bronchopulmonary Dysplasia (BPD), Necrotizing Enterocolitis, Intraventricular Hemorrhage
As per AHA 2007 guidelines:
- Routine infective endarteritis prophylaxis is NOT recommended for unrepaired PDA
- Recommended only for: First 6 months following successful device or surgical closure, or if residual defect remains near prosthetic material, or prior history of infective endarteritis
- After complete closure with no residual shunt beyond 6 months — prophylaxis is no longer needed
- Silent PDAs — no murmur, found incidentally on echo; no hemodynamic significance
- Small PDAs in asymptomatic term infants and children — some have spontaneous closure
- Preterm infants >28 weeks with small PDAs who are asymptomatic — most will close spontaneously with conservative measures (fluid restriction, maintenance of normal O2 saturation, diuretics if needed)
- The trend in neonatology is shifting toward more conservative management of asymptomatic preterm PDA as evidence shows many close spontaneously and intervention may not improve long-term outcomes
🔭 Recent Advances — Exam Q&A
The Piccolo Occluder (Abbott) is a transcatheter PDA closure device specifically designed for very small premature and low-birthweight infants (even <700 g). It is delivered through a 4 French sheath, making it suitable for tiny femoral vessels. This device received FDA approval in 2019, enabling transcatheter closure in extremely preterm neonates who were previously only candidates for surgical ligation. It has significantly reduced the need for open thoracotomy in extremely premature infants.
Oral/IV acetaminophen is an emerging pharmacological option for ductal closure, particularly in preterm infants.
- Mechanism: Inhibits the peroxidase active site of prostaglandin H2 synthase (a different site than classical COX inhibition by indomethacin/ibuprofen) → reduces prostaglandin synthesis
- Dose: 15 mg/kg q6h for 3–7 days (oral or IV)
- Advantages over indomethacin: Minimal renal vasoconstriction, better tolerated, no significant platelet or GI effects, oral route available
- Efficacy: Meta-analyses show comparable closure rates to indomethacin and ibuprofen (~70–80%)
- Particularly useful when indomethacin/ibuprofen are contraindicated
Recent evidence (including the Baby OSCAR and PDA-TOLERATE trials) suggests that conservative / expectant management of asymptomatic or mildly symptomatic preterm PDA (without pharmacological or surgical intervention) does not worsen neonatal outcomes and may be equally effective as routine pharmacological treatment, given that many PDAs close spontaneously.
Key aspects of conservative management include: fluid restriction, optimal PEEP on ventilation, diuretics, maintaining adequate hemoglobin. The decision to intervene is based on hemodynamic significance rather than mere echocardiographic presence of a ductus.
This has led to a global shift from prophylactic or routine medical treatment to symptom-guided, individualized management.
- Bosentan (dual endothelin receptor antagonist) — improves exercise capacity and functional class; recommended in Eisenmenger syndrome including PDA-related
- Sildenafil (PDE-5 inhibitor) — reduces PVR; used in borderline operability and Eisenmenger for symptom management
- Inhaled iloprost / treprostinil — prostacyclin analogues; used in advanced PAH
- Inhaled Nitric Oxide — used in catheterization lab to test pulmonary vasoreactivity to determine operability
These are not curative and do not reverse Eisenmenger. Surgery remains contraindicated. The only definitive option is heart-lung transplantation.
VATS ligation is a minimally invasive surgical alternative to open thoracotomy. Using 3 small ports in the chest wall, the surgeon clips the ductus under thoracoscopic vision. Advantages include less postoperative pain, faster recovery, smaller scars, and shorter ICU stay compared to open thoracotomy. It does not require cardiopulmonary bypass. VATS is now preferred over open surgery in larger infants and children where device closure is not feasible.
⚡ Key Points — Quick Revision
One-Liners for Exam
- PDA connects: Main pulmonary artery → descending aorta (just distal to left subclavian artery)
- Most common cause in preterm: Immaturity of ductal smooth muscle
- Most common infection causing PDA: Congenital Rubella
- Gender: Female > Male (2:1) in term infants
- PDA murmur: Continuous "machinery" (Gibson's) murmur — best at left infraclavicular / 2nd LICS
- Pulse character: Bounding/collapsing — due to diastolic runoff
- Wide pulse pressure: Hallmark of PDA
- Apical MDM in PDA: Indicates large shunt (Qp:Qs >2:1)
- Differential cyanosis: Lower limb cyanosis + upper limb normal — pathognomonic of Eisenmenger PDA
- CXR: Cardiomegaly + pulmonary plethora + prominent aortic knuckle
- Gold standard investigation: 2D Echo with Color Doppler
- LA:Ao ratio >1.3: Significant shunt
- Pharmacological closure (preterm only): Indomethacin / Ibuprofen / Acetaminophen (COX inhibitors)
- NOT effective in term infants: Indomethacin / Ibuprofen
- PGE1 (Alprostadil): Keeps ductus OPEN — used in duct-dependent CHDs
- Device of choice (term): Amplatzer Ductal Occluder (ADO)
- Device for tiny premature infants: Piccolo Occluder
- Surgical approach: Left posterolateral thoracotomy — ligation/division; no CPB needed
- Eisenmenger PDA: Surgery contraindicated; only medical management or heart-lung transplant
- Complication in preterm: Worsens RDS, increases BPD, NEC, IVH risk
- Infective endarteritis prophylaxis: NOT routinely recommended (AHA 2007)
- Venous hum vs PDA: Venous hum disappears on lying down / IJV compression — PDA does not
🔢 Numbers to Remember
- PDA = 5–10% of all CHDs
- Incidence in preterm <28 weeks: 60–70%
- F:M ratio = 2:1 (term)
- Ductal functional closure: within 24–72 hours of birth
- Anatomical closure: within 2–3 weeks of life
- Indomethacin dose: 0.1–0.2 mg/kg q12–24h × 3 doses
- Efficacy of indomethacin: ~70–80% in preterms
- Operability PVR cut-off: <8 Wood units; PVR/SVR <0.66