Makindo Medical Notes

💡 Key clinical clue: A continuous “machinery” murmur maximal at the left infraclavicular area is classic for a Patent Ductus Arteriosus (PDA). This congenital shunt connects the aorta and pulmonary artery and fails to close after birth. 🩸 Causes left-to-right shunt, pulmonary overcirculation, and later → Eisenmenger’s reversal (right-to-left shunt with cyanosis of toes but not fingers). ⚠️ Carries a significant risk of infective endocarditis.

🧠 About

• Common congenital lesion, particularly in premature infants and females (2:1).
• In fetal life, the ductus arteriosus (DA) shunts blood from the pulmonary artery → descending aorta, bypassing the lungs.
• After birth, increased oxygen tension and reduced prostaglandin levels should trigger closure within hours–days.
• PGE₂ (Prostaglandin E₂) keeps the duct open; NSAIDs (Indomethacin/Ibuprofen) help close it.

🌍 Risk Factors

• Premature birth (commonest cause).
• Female sex and high-altitude birth.
• Maternal rubella infection in 1st trimester.
• Fetal alcohol exposure or chromosomal abnormalities (e.g. Down, Edwards).

⚙️ Pathophysiology

• Persistence of the ductus → continuous flow from aorta (high pressure) → pulmonary artery (low pressure).
• Results in pulmonary overcirculation, left atrial and left ventricular volume overload, and eventually heart failure.
• Chronically increased pulmonary vascular resistance can cause shunt reversal → Eisenmenger’s syndrome with cyanosis confined to the lower limbs.

🧪 Dynamic Response to Drugs

• ↑ Oxygen & NSAIDs → close the ductus arteriosus.
• ↑ Prostaglandin E₂ → keeps ductus open (useful in duct-dependent lesions like TGA, CoA, ToF).

🩺 Clinical Features

• 💧 Infants: Poor feeding, failure to thrive, sweating, tachypnoea.
• 🔊 Murmur: Continuous “machinery” murmur below left clavicle, with thrill.
• ❤️ Cardiac signs: Bounding (“water-hammer”) pulse, wide pulse pressure, displaced apex beat.
• 🫁 Respiratory: Recurrent chest infections due to pulmonary congestion.
• 🔵 Eisenmenger’s physiology: Cyanosis of toes but not fingers (“differential cyanosis”).

🧫 Investigations

• Bloods: FBC, U&E, CRP, BNP (may be elevated if cardiac strain).
• ECG: May show LV hypertrophy or biventricular strain.
• CXR: Cardiomegaly + pulmonary plethora (overcirculation).
• Echocardiogram: Diagnostic — parasternal short-axis or suprasternal view shows continuous flow between aorta & pulmonary artery.
• Cardiac catheterisation: Defines size/anatomy pre-intervention.

🩹 Management

• 👶 Premature infants: May close spontaneously; trial of NSAIDs (Indomethacin or Ibuprofen) within first 10–14 days of life to inhibit prostaglandin synthesis.
• 💊 Medical therapy: Treat heart failure — diuretics, digoxin if needed.
• 🩺 Transcatheter closure: Amplatzer duct occluder device via catheter (first-line in children & adults if PDA remains open).
• 🔪 Surgical ligation: If duct large or unsuitable for catheter closure.
• 🦠 Infective endocarditis prophylaxis: Important in unrepaired PDA or early post-repair period.

📈 Prognosis

• Excellent if diagnosed and treated early — most children live normal lives post-closure.
• If untreated → progressive pulmonary hypertension, Eisenmenger’s syndrome, heart failure, and endocarditis risk.

💡 Teaching Tip

• PDA highlights how foetal circulation physiology continues postnatally — the duct that was essential in utero becomes pathological after birth.
• Mnemonic: “PGE keeps PDA open” — prostaglandins prolong ductal patency, NSAIDs close it.
• Compare and contrast with other left-to-right shunts (ASD, VSD) — continuous murmur is unique to PDA.

📚 References

• BNF: NSAIDs for ductal closure
• NICE NG204 (2021): Specialist neonatal management guidance
• Ohlsson A & Walia R. Indomethacin and ibuprofen for PDA in preterm infants. Cochrane Database Syst Rev, 2020.
• Gatzoulis MA et al., Congenital Heart Disease in Adults, 4th Ed. Elsevier 2021.