About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- CHD affects ~8 per 1,000 live births — most common congenital abnormality
- Acyanotic (left-to-right shunts): VSD (most common CHD overall), ASD, PDA, AVSD, coarctation of aorta
- Cyanotic (right-to-left shunts): Tetralogy of Fallot (most common cyanotic CHD), TGA, tricuspid atresia, total anomalous pulmonary venous return
- Duct-dependent lesions (present when ductus arteriosus closes at day 1–3): collapse, cyanosis, acidosis — give IV prostaglandin E1 (dinoprostone/alprostadil) to keep duct open
- VSD: pansystolic murmur at left sternal edge. Small VSDs are louder than large ones
- Down syndrome is strongly associated: AVSD (~40% of Down syndrome heart defects), VSD, ASD, PDA, Tetralogy
Overview
Congenital heart disease encompasses a wide spectrum of structural cardiac abnormalities present from birth. Lesions are broadly classified as acyanotic (left-to-right shunts causing volume overload and eventually pulmonary hypertension — Eisenmenger syndrome) or cyanotic (right-to-left shunts causing systemic desaturation). Some critical lesions are duct-dependent, meaning systemic or pulmonary circulation relies on flow through the patent ductus arteriosus. When the duct closes (typically 1–3 days of life), these infants present with acute cardiovascular collapse or severe cyanosis.
Epidemiology
CHD occurs in approximately 8 per 1,000 live births. VSD is the most common individual lesion (~30%). Tetralogy of Fallot is the most common cyanotic lesion. Many mild defects (small muscular VSD, small ASD) close spontaneously. Antenatal screening detects many cases, but some present postnatally. Risk factors include maternal diabetes, maternal rubella, alcohol, anticonvulsants (sodium valproate), and chromosomal abnormalities (Down syndrome — AVSD; Turner syndrome — coarctation, bicuspid aortic valve; Williams syndrome — supravalvular aortic stenosis; DiGeorge/22q11 — truncus arteriosus, interrupted aortic arch, Tetralogy).
Clinical Features
Symptoms
Cyanosis — central, not improving with supplemental oxygen (cyanotic CHD, fixed right-to-left shunt)
Heart failure: poor feeding, sweating during feeds, tachypnoea, failure to thrive
Recurrent chest infections (large left-to-right shunts with pulmonary overcirculation)
Tet spells in Tetralogy of Fallot: episodic cyanosis, squatting in older children
Acute collapse in first few days of life (duct-dependent lesion)
Signs
Murmur — type and location indicate the lesion (see exam tips)
Hepatomegaly (right heart failure)
Tachypnoea and subcostal recession (pulmonary overcirculation)
Absent or weak femoral pulses (coarctation of aorta)
Four-limb blood pressure discrepancy — higher in arms than legs (coarctation)
Failed newborn pulse oximetry screening (<95% in right hand or >3% difference)
Investigations
First-line
Pulse oximetry screeningNewborn screening: measure SpO2 in right hand and either foot at 6–12 h of age. <95% or >3% difference = refer for echocardiography
EchocardiographyGold standard for diagnosis and anatomical assessment of all congenital heart lesions
Four-limb blood pressuresIf coarctation suspected — significant gradient (>20 mmHg) between arms and legs
Second-line
CXRMay show cardiomegaly, pulmonary plethora (L-to-R shunt), pulmonary oligaemia (R-to-L shunt), boot-shaped heart (Tetralogy), egg-on-a-string (TGA)
ECGRVH, LVH, axis deviation, conduction abnormalities depending on lesion
Specialist
Cardiac catheterisationFor haemodynamic assessment, interventional procedures (balloon valvuloplasty, device closure of ASD/PDA/VSD)
Cardiac MRIFor complex anatomy, assessment of great vessels, surgical planning
1
Duct-dependent lesions — emergency management
- If duct-dependent lesion suspected (collapse or cyanosis in first days of life): start IV prostaglandin E1 (alprostadil 5–20 nanograms/kg/min)
- Side effects: apnoea (be prepared to intubate), hypotension, fever
- Transfer urgently to specialist paediatric cardiac centre
- Duct-dependent systemic circulation: critical coarctation, interrupted aortic arch, HLHS
- Duct-dependent pulmonary circulation: pulmonary atresia, critical pulmonary stenosis, Tetralogy with severe RVOTO
2
Heart failure management
- Diuretics: furosemide 1 mg/kg/dose
- ACE inhibitors: captopril or enalapril for afterload reduction
- Calorie-dense feeds to support growth
- Definitive repair when child is stable and of appropriate size
3
Surgical and interventional management
- Small muscular VSD: often closes spontaneously — observe
- Large VSD, AVSD: surgical repair (usually by 3–6 months if symptomatic)
- ASD: percutaneous device closure or surgical repair if haemodynamically significant
- PDA: percutaneous device or coil closure, or surgical ligation
- Tetralogy of Fallot: complete repair at 3–6 months (VSD closure + RVOT relief)
- TGA: arterial switch operation (Jatene) within first 2 weeks of life
- Coarctation: surgical repair or balloon angioplasty + stenting
Complications
- Heart failure: From volume overload in large left-to-right shunts
- Eisenmenger syndrome: Irreversible pulmonary hypertension causing reversal of shunt (L-to-R becomes R-to-L) — contraindication to surgical repair
- Infective endocarditis: Risk with unrepaired or recently repaired lesions
- Arrhythmias: Both pre- and post-operative
- Growth failure and developmental delay: From chronic hypoxia or heart failure
- Paradoxical embolism: Through septal defects
UKMLA Exam Tips
- 1VSD = most common CHD. Pansystolic murmur at left lower sternal edge. Small VSDs are LOUDER (high velocity jet)
- 2Tetralogy of Fallot = most common cyanotic CHD. Four features: VSD, overriding aorta, RVOT obstruction, RVH
- 3Absent femoral pulses in a neonate = coarctation until proven otherwise — check four-limb BPs
- 4Down syndrome + CHD = think AVSD first (most characteristic), also VSD, ASD, PDA, Tetralogy
- 5Duct-dependent collapse at day 1–3: immediate IV prostaglandin E1 to reopen the ductus
- 6Newborn pulse oximetry screening: <95% or >3% difference between hand and foot = refer for echo
- 7Tet spells: child goes blue and squats (increases SVR, forces blood through pulmonary circulation) — treat with oxygen, morphine, IV fluids, phenylephrine
practicetest your knowledge on congenital heart disease in childrenApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — paediatrics and beyond.
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