A. Furosemide
B. Ibuprofen
C. Oxytocin
D. Misoprostol
E. Estradiol
Answer: Ibuprofen
Detailed discussion for MRCP
This premature infant has a patent ductus arteriosus (PDA), suggested by the classic continuous “machinery” murmur in the left infraclavicular region. PDA is particularly common in preterm neonates because immaturity of the ductal smooth muscle and higher circulating prostaglandin levels delay physiological closure. Normally, the ductus arteriosus constricts within hours to days after birth due to increased oxygen tension and a fall in prostaglandin E₂ levels. In preterm infants, this mechanism is inefficient, leading to persistent left-to-right shunting from the aorta into the pulmonary artery.
A haemodynamically significant PDA can cause pulmonary overcirculation, heart failure, prolonged ventilator dependence, necrotising enterocolitis, intraventricular haemorrhage, and chronic lung disease. For this reason, if the PDA remains clinically significant after a short period of conservative management (often around 5–7 days), pharmacological closure is recommended.
Ibuprofen (or indomethacin) is the drug of choice because it inhibits cyclo-oxygenase, reducing prostaglandin synthesis and thereby promoting ductal constriction and closure. Ibuprofen is increasingly preferred over indomethacin due to a more favourable renal and gastrointestinal safety profile. Paracetamol is an alternative in selected cases when NSAIDs are contraindicated.
In contrast, prostaglandin E₁ is used when ductal patency is desirable, such as in duct-dependent cyanotic congenital heart disease (e.g. transposition of the great arteries). Diuretics, sex hormones, or uterotonic agents have no role in closing a PDA. Importantly, pharmacological closure is effective mainly in preterm infants; term infants and older children usually require transcatheter device closure or surgery.
For MRCP candidates, key high-yield points include recognising the murmur, understanding why prematurity predisposes to PDA, knowing when to observe versus treat, and distinguishing drugs that close the duct from those that keep it open.
Cheat sheet for exam
- PDA = persistent connection between descending aorta and pulmonary artery
- Common in: prematurity, maternal rubella, high altitude
- Murmur: continuous “machinery” murmur at left infraclavicular area
- Haemodynamics: left-to-right shunt → pulmonary overcirculation
- First-line pharmacological closure (preterm): ibuprofen or indomethacin
- Mechanism: ↓ prostaglandin synthesis (COX inhibition)
- Alternative: paracetamol
- Do NOT use prostaglandins for closure (they keep PDA open)
- Term infants: transcatheter or surgical closure
- Complications if untreated: HF, NEC, IVH, pulmonary hypertension
Flash cards
- What murmur suggests PDA? – Continuous machinery murmur
- Typical location of PDA murmur? – Left infraclavicular area
- PDA shunt direction? – Left to right
- Why common in preterm infants? – High prostaglandins, immature duct
- First-line drug for PDA closure in preterms? – Ibuprofen
- Mechanism of ibuprofen in PDA? – COX inhibition → ↓ prostaglandins
- Alternative NSAID for PDA closure? – Indomethacin
- NSAID with fewer renal side effects? – Ibuprofen
- Non-NSAID alternative for PDA closure? – Paracetamol
- Drug that keeps ductus open? – Prostaglandin E₁
- Example of duct-dependent lesion? – Transposition of great arteries
- PDA pulse character? – Bounding pulse
- Pulse pressure in PDA? – Wide
- Cyanosis type in late PDA? – Differential cyanosis
- PDA management in term infants? – Device or surgical closure
- Risk of untreated PDA? – Heart failure
- PDA effect on lungs? – Pulmonary overcirculation
- Antenatal drug to prevent PDA? – None
- Timing of pharmacological closure? – After ~1 week if significant
- Maternal infection linked to PDA? – Rubella
MCQs
- A continuous murmur in a preterm neonate most strongly suggests:
A. VSD
B. ASD
C. PDA
D. Pulmonary stenosis
E. Coarctation
Answer: C - PDA results in which haemodynamic abnormality?
A. Right-to-left shunt
B. Reduced pulmonary flow
C. Left-to-right shunt
D. Decreased LV preload
E. Systemic hypoxia at birth
Answer: C - Which drug promotes PDA closure?
A. Prostaglandin E₁
B. Dopamine
C. Ibuprofen
D. Furosemide
E. Milrinone
Answer: C - Mechanism of ibuprofen in PDA is inhibition of:
A. ACE
B. COX
C. PDE-5
D. Beta receptors
E. Calcium channels
Answer: B - PDA is most commonly associated with:
A. Post-term birth
B. Prematurity
C. Maternal diabetes
D. Twin pregnancy
E. Male sex
Answer: B - Which murmur feature is classic for PDA?
A. Early diastolic
B. Ejection systolic
C. Continuous
D. Mid-systolic click
E. Late systolic
Answer: C - Which drug should be avoided if the aim is ductal closure?
A. Indomethacin
B. Paracetamol
C. Ibuprofen
D. Prostaglandin E₁
E. None
Answer: D - Preferred PDA treatment in term infants is:
A. Ibuprofen
B. Indomethacin
C. Observation only
D. Transcatheter closure
E. Prostaglandin infusion
Answer: D - A wide pulse pressure in PDA is due to:
A. Reduced LV output
B. Increased aortic compliance
C. Diastolic runoff into pulmonary artery
D. Bradycardia
E. Hypovolaemia
Answer: C - Which complication is linked to haemodynamically significant PDA in preterms?
A. NEC
B. Polycythaemia
C. Cyanotic spells
D. Tet spells
E. LV hypertrophy only
Answer: A - PDA connects which structures?
A. RA to LA
B. RV to LV
C. Pulmonary artery to aorta
D. Aorta to SVC
E. LV to pulmonary vein
Answer: C - Why does oxygen promote ductal closure?
A. Stimulates NO
B. Increases prostaglandins
C. Direct smooth muscle constriction
D. Reduces blood viscosity
E. Causes acidosis
Answer: C - Which NSAID is declining in use due to side effects?
A. Aspirin
B. Ibuprofen
C. Indomethacin
D. Naproxen
E. Diclofenac
Answer: C - PDA initially causes volume overload of which chamber?
A. Right atrium
B. Right ventricle
C. Left atrium
D. Left ventricle
E. Both atria
Answer: D - Late untreated PDA may cause:
A. Eisenmenger syndrome
B. Tetralogy of Fallot
C. Tricuspid atresia
D. Ebstein anomaly
E. HLHS
Answer: A - Best initial approach in asymptomatic preterm PDA?
A. Immediate surgery
B. Prostaglandin infusion
C. Expectant supportive care
D. ACE inhibitors
E. Beta-blockers
Answer: C - PDA murmur is best heard at:
A. Apex
B. Right sternal edge
C. Left infraclavicular area
D. Back
E. Carotids
Answer: C - Which maternal factor increases PDA risk?
A. Hypothyroidism
B. Rubella infection
C. Pre-eclampsia
D. Smoking
E. Anaemia
Answer: B - PDA pharmacological treatment is given to:
A. Mother antenatally
B. Mother postnatally
C. Infant postnatally
D. Infant antenatally
E. Placenta
Answer: C - Which statement is TRUE?
A. Prostaglandins close the ductus
B. PDA is usually cyanotic at birth
C. Ibuprofen reduces prostaglandin synthesis
D. PDA is rare in preterms
E. Surgery is first-line in all neonates
Answer: C
Summary for quick exam revision
Patent ductus arteriosus is a common acyanotic congenital heart defect, particularly in preterm infants, caused by failure of the ductus arteriosus to close after birth. It produces a characteristic continuous machinery murmur in the left infraclavicular region and results in a left-to-right shunt with pulmonary overcirculation. Prematurity, maternal rubella infection, and high altitude are key risk factors. Initial management is often conservative, as spontaneous closure may occur. If the PDA remains haemodynamically significant after about one week, pharmacological closure is recommended. Ibuprofen or indomethacin is used, acting via cyclo-oxygenase inhibition and reduced prostaglandin synthesis, with ibuprofen preferred due to fewer adverse effects. Paracetamol is an alternative when NSAIDs are contraindicated. Prostaglandin E₁ has the opposite role and is used to keep the duct open in duct-dependent cyanotic heart disease. In term infants and older children, device or surgical closure is the treatment of choice. Recognising the murmur, understanding drug mechanisms, and knowing age-specific management are high-yield MRCP points.