Congenital Heart Disease

Overview

Congenital heart disease (CHD) encompasses the structural cardiovascular defects present at birth, arising from disordered cardiac embryogenesis between the third and eighth weeks of gestation. It is the most common birth defect, occurring in approximately 8–9 per 1000 live births — and around 2–3 per 1000 symptomatic in the first year. About one-third are critical, requiring intervention in infancy. Classification into acyanotic vs cyanotic is the single most useful clinical heuristic because it directs the bedside differential, the murmur interpretation, and the urgency of intervention. A second, equally important axis is whether the lesion is duct-dependent: these children are well at birth and collapse at 24–72 hours when the ductus arteriosus closes, and they die unless prostaglandin E1 (PGE1) is started before transfer to a cardiac centre. [1]

[1]

Embryology of the Heart

The heart is the first functional organ of the embryo, beginning to beat at around day 22 of gestation. Understanding its embryology explains the anatomical logic of nearly every congenital lesion and is a high-yield area in vivas. [1]

Formation of the heart tube (weeks 3–4). Cardiogenic progenitor cells in the anterior lateral plate mesoderm migrate to form a pair of endocardial tubes that fuse into a single primitive heart tube by day 21. The tube, suspended by the dorsal mesocardium, then undergoes dextral looping (folding to the right) — the first manifestation of visceral situs. Failure of normal left-right patterning produces heterotaxy syndromes (asplenia/polysplenia), in which atrial appendage morphology is isomeric and the cardiac plumbing is profoundly disordered. [1]

Chamber specification and septation (weeks 4–8). The looped tube develops five dilations: truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium and sinus venosus (cranial to caudal). Septation then proceeds in parallel: [1]

1. Atrial septation. The septum primum grows down from the roof of the atrium toward the endocardial cushions, leaving the ostium primum. Before fusion, the upper part of septum primum perforates (ostium secundum). A stiffer septum secundum then descends to the right of the primum, also incomplete, leaving the foramen ovale — a one-way flap valve allowing right-to-left shunting in utero. Defects here produce secundum ASD (most common) or patent foramen ovale. Endocardial cushion defects produce primum ASD and AVSD (strong Down syndrome association). [1]

2. Ventricular septation. The muscular interventricular septum grows upward from the floor of the ventricle; the small remaining membranous portion is closed by tissue from the endocardial cushions and the conotruncal (aorticopulmonary) septum. The membranous region is the last to close and is the site of the commonest perimembranous VSD. [1]

3. Outflow tract septation. Neural-crest-derived cells migrate into the truncus arteriosus and form spiral aorticopulmonary and conotruncal septae that twist 180°, partitioning the truncus into the aorta (left, fourth arch) and pulmonary artery (right, sixth arch). Failure of spiral septation produces persistent truncus arteriosus; failure of spiral (but with two arteries) gives transposition of the great arteries (TGA). 22q11.2 deletion (DiGeorge) disrupts neural crest migration and clusters with conotruncal lesions — TOF, truncus arteriosus, interrupted aortic arch. [1]

4. Aortic arch derivatives. The fourth pharyngeal arch gives the aortic arch (left) and proximal subclavian (right); the sixth arch gives the pulmonary arteries and the ductus arteriosus (left sixth). Anomalies include coarctation (fourth arch), patent ductus arteriosus (sixth arch), and vascular rings (aberrant subclavian, double aortic arch). [1]

The fetal circulation has three shunts — ductus venosus (umbilical vein → IVC), foramen ovale (RA → LA, bypassing lungs), and ductus arteriosus (PA → descending aorta, bypassing the high-resistance fetal lungs). At birth, lung expansion drops pulmonary vascular resistance, umbilical flow ceases, and rising PaO₂ with falling prostaglandins trigger ductal constriction — completing the transition to the adult series circulation by ~72 hours. Understanding this transition is the key to duct-dependent physiology (see below). [1]

Key Lesions

Ventricular Septal Defect (VSD)

VSD is the most common congenital heart lesion, accounting for 30–35% of all CHD. The interventricular septum has four embryological components, each giving a VSD subtype: [1]

• Perimembranous (80%) — defect in the membranous septum adjacent to the aortic and tricuspid valves. May close spontaneously by tricuspid valve leaflet adherence (aneurysm of the membranous septum).
• Muscular (5–20%) — within the muscular septum; can be central, apical, multiple ("Swiss-cheese"). Highest rate of spontaneous closure (up to 80%) by fibrous ingrowth.
• Inlet (~5%) — posterior, behind the septal leaflet of the tricuspid valve; part of AVSD / Down syndrome.
• Outlet / supracristal / doubly-committed (5%) — just below the aortic and pulmonary valves; uncommon in Western populations but common in Asian populations; high risk of aortic cusp prolapse and progressive aortic regurgitation (the right coronary cusp prolapses into the defect). [1]

Clinical features. A pansystolic (holosystolic) murmur at the lower left sternal edge is the hallmark; smaller defects paradoxically produce louder, harsher murmurs (high-velocity turbulent jet) — a classic viva trap. Large defects produce a thrill, a displaced hyperdynamic apex (LV volume overload), and an apical mid-diastolic flow murmur (relative mitral stenosis from increased LA→LV flow). Infants with large VSDs develop failure to thrive (FTT), tachypnoea, sweating with feeds, and recurrent lower respiratory infections once pulmonary vascular resistance has fallen at 6–8 weeks. [1]

Natural history. Approximately 75% of small muscular and perimembranous VSDs close spontaneously by age 2 (fibrous proliferation, tricuspid leaflet adherence). Large uncorrected VSDs progress to pulmonary vascular remodelling → Eisenmenger syndrome (classically by age 2 years if Qp:Qs > 2:1). The aim of surgery is to close before pulmonary vascular disease becomes irreversible. [1]

Atrial Septal Defect (ASD)

ASD accounts for 8–10% of CHD. Three anatomical types: [1]

• Secundum ASD (70–75%) — defect in the fossa ovalis region; most amenable to device closure (Amplatzer septal occluder) if the rim of tissue is adequate and the defect is < 38 mm.
• Primum ASD (~15%) — part of partial AVSD, associated with a cleft mitral valve and Down syndrome.
• Sinus venosus ASD (~10%) — near the SVC or IVC orifice; always associated with partial anomalous pulmonary venous drainage (usually right upper pulmonary vein draining to SVC); not amenable to device closure — needs surgery. [1]

Clinical features. Often asymptomatic in childhood — the murmur is soft ejection systolic at the upper left sternal edge (relative pulmonary stenosis from increased RV stroke volume) with a fixed, widely split second heart sound (the single most examined physical sign in ASD: delayed P2 from RV volume overload plus loss of normal respiratory variation because the LA-RA shunt equalises atrial pressures). Presentation is usually in the third–fifth decade with paradoxical embolism (cryptogenic stroke), atrial fibrillation, or exercise intolerance. [1]

Patent Ductus Arteriosus (PDA)

The ductus arteriosus connects the proximal descending aorta to the pulmonary artery, derived from the left sixth aortic arch. Persistence beyond the first few weeks of life (longer in prematurity) is PDA (~12% of term CHD, very common in preterm infants). [1]

Clinical features. The classic continuous "machinery" murmur maximal below the left clavicle, bounding pulses and a wide pulse pressure (diastolic run-off into the low-pressure PA). In premature infants, a large PDA contributes to respiratory distress syndrome, necrotising enterocolitis, and intraventricular haemorrhage. [1]

Closure. Pharmacological closure in preterm infants uses indomethacin (0.1–0.2 mg/kg/dose IV, 3 doses) or ibuprofen (10 mg/kg then 5 mg/kg × 2) — both non-steroidal COX inhibitors that block prostaglandin synthesis and cause ductal constriction. Paracetamol is an emerging alternative. Term infants and those failing medical therapy undergo surgical ligation or percutaneous device closure (occluder) in older children. PGE1 does the opposite — keeps the duct open in duct-dependent lesions. [1]

Tetralogy of Fallot (TOF)

TOF is the most common cyanotic CHD presenting after the neonatal period (5–8% of all CHD). It results from antero-cephalo-deviation of the outlet septum, producing a single embryological error with four anatomical consequences — the PROVe tetrad: [1]

1. Pulmonary (and infundibular/right ventricular outflow tract) stenosis — the cardinal abnormality; the degree of obstruction determines the degree of cyanosis.
2. Right ventricular hypertrophy (RVH) — secondary to the RV facing a stenotic outflow tract plus systemic pressures via the VSD.
3. Overriding aorta — aorta arises from both ventricles, astride the VSD.
4. Ventricular septal defect — typically large, malalignment, perimembranous/outlet. [1]

Clinical features. Cyanosis may be absent at birth ("pink TOF") and develop as the infundibular stenosis progresses. Murmur is a long ejection systolic at the mid-left sternal edge (RVOT obstruction) radiating to the lung fields. Older uncorrected children characteristically squat — this kinks the femoral arteries, increasing systemic vascular resistance (SVR), which forces more blood through the stenotic RVOT into the lungs and relieves cyanosis. CXR shows the classic "boot-shaped" heart (concave pulmonary bay, upturned apex from RVH) with oligaemic lung fields. Right-sided aortic arch in 25%. [1]

Tet (hypercyanotic) spells are episodes of sudden, profound cyanosis, irritability and hyperpnoea, occurring classically on waking, crying, or straining, in the first 2 years. The pathophysiology is infundibular muscle spasm → sudden increase in RVOT obstruction → reduced pulmonary blood flow → increased right-to-left shunting through the VSD → rapidly worsening hypoxaemia. Management is stepwise and a high-yield exam algorithm: [1]

1. Knee-chest position — increases SVR, reduces R-to-L shunting. (Calm the child; parental cuddle.)
2. High-flow 100% oxygen — drops PVR.
3. Morphine 0.1–0.2 mg/kg SC/IM — calms the child, reduces catecholamine surge, relaxes infundibular muscle.
4. Intravenous fluids / bolus 10 mL/kg normal saline — increases preload, improves RV output.
5. Phenylephrine 5–10 mcg/kg IV — pure alpha-agonist, raises SVR without tachycardia (the most reliable pharmacological agent for refractory spells).
6. Propranolol 0.1 mg/kg IV (or oral propranolol prophylaxis 0.5–1 mg/kg 6-hourly) — beta-blockade reduces infundibular spasm and heart rate.
7. Refractory spell → emergency surgery (BT shunt or complete repair). [1]

Surgery. Complete repair at 3–6 months is now standard of care. Components: VSD patch closure (via right atriotomy), RVOT relief (infundibular muscle resection, pulmonary valvotomy, transannular patch if the annulus is small). Long-term complication is pulmonary regurgitation (from the transannular patch) — usually well tolerated for decades but eventually requires pulmonary valve replacement (often transcatheter, Melody/Sapien valves) in adolescence/adulthood. A modified Blalock-Taussig (BT) shunt (Gore-Tex graft between subclavian and pulmonary artery) is reserved for neonates with severe cyanosis who are too small or unstable for complete repair — it is palliative, not corrective. [1]

Transposition of the Great Arteries (TGA)

TGA (5% of CHD) is the commonest cyanotic lesion presenting as a severely cyanosed neonate within hours of birth. Embryologically the conotruncal septum fails to spiral, so the aorta arises from the right ventricle and the pulmonary artery from the left ventricle — two parallel circulations. The aorta is typically anterior and rightward ("D-TGA"). Survival requires mixing at one or more sites: PDA, ASD, or VSD (~40% have an associated VSD). [1]

Clinical features. Intense central cyanosis from birth, often with minimal respiratory distress (the lungs are well perfused but the blood is parallel). Murmurs are typically absent unless there is an associated VSD. Without intervention, death occurs within days–weeks. [1]

Initial management (duct-dependent). PGE1 infusion 0.05–0.1 mcg/kg/min to keep the ductus open and allow mixing. Emergency balloon atrial septostomy (Rashkind manoeuvre) — a balloon catheter is passed across the foramen ovale, inflated and jerked back to tear the septum primum, enlarging the ASD and improving atrial mixing — is performed if PGE1 alone gives inadequate mixing. [1]

Definitive surgery — the arterial switch (Jatene operation). Performed ideally in the first 2 weeks of life, while the left ventricle is still a high-pressure pumping chamber (it is pumping against the low-resistance pulmonary circulation; if one waits too long, the LV involutes to a thin-walled low-pressure pump and cannot support systemic pressures after switch). The great arteries are transected and re-anastomosed in the correct position, and the coronary arteries are re-implanted into the neo-aorta — the critical and most technically demanding step (coronary anatomy varies and is the main determinant of surgical mortality). The VSD and ASD are closed. Long-term outcomes are excellent (>95% survival, near-normal exercise capacity). [1]

Historical atrial switch (Mustard / Senning). Performed before the Jatene era; redirects venous return at atrial level using a baffle (systemic venous blood → mitral → LV → PA; pulmonary venous blood → tricuspid → RV → aorta). The right ventricle remains the systemic ventricle and inevitably fails in adulthood, with a high burden of atrial arrhythmias and baffle obstruction/leak — these adult patients are a major source of ACHD morbidity. No longer performed. [1]

Coarctation of the Aorta

Narrowing of the aorta, classically at the isthmus (just distal to the left subclavian artery, at the site of the ductal insertion). Accounts for ~8% of CHD; male predominance (2:1); strongly associated with bicuspid aortic valve (50–85%) and Turner syndrome (45,X) — all patients with Turner syndrome should be screened with echo. [1]

Presentation. Severe ("infantile" / preductal) coarctation is duct-dependent — the lower body is perfused by the ductus delivering deoxygenated blood from the PA, producing differential cyanosis (pink upper body, blue lower body). These neonates collapse at duct closure with shock and metabolic acidosis and need PGE1 urgently. Older children/adults present incidentally with upper limb hypertension, radio-femoral delay (weak/absent femoral pulses, delayed compared with radial), cold lower limbs, or leg claudication. A systolic BP > 20 mmHg higher in arms than legs is diagnostic. [1]

Investigation. Four-limb BP showing arm-leg gradient. Echocardiogram defines the coarctation, arch hypoplasia, and bicuspid valve. CXR in older children shows the "3 sign" (pre-stenotic dilatation of ascending aorta + post-stenotic dilatation at the level of the left subclavian) and rib notching (dilated intercostal collaterals eroding the inferior rib margins — third to eighth ribs, bilateral, usually seen after ~5 years of age). [1]

Management. Neonates: stabilise with PGE1 then surgical resection with end-to-end anastomosis (preferred) or subclavian flap angioplasty. Older children/adults: balloon angioplasty ± stenting is increasingly preferred for native and recurrent coarctation. Long-term surveillance for re-coarctation, hypertension, and berry aneurysms is mandatory. [1]

Hypoplastic Left Heart Syndrome (HLHS) and the Fontan Circulation

HLHS (2–3% of CHD) comprises mitral and aortic atresia/stenosis with a hypoplastic LV and ascending aorta. The right ventricle must pump the entire circulation — systemic output reaches the body retrogradely through a ductus-dependent aortic arch, and pulmonary venous return crosses an obligate ASD into the RA. At duct closure, neonates collapse with shock and profound acidosis — a duct-dependent systemic circulation. [1]

Staged single-ventricle palliation is the only option — there is no two-ventricle repair possible. The end-goal is the Fontan circulation, in which systemic venous return is routed directly to the pulmonary arteries without an intervening sub-pulmonary pump: [1]

1. Stage 1 — Norwood or hybrid procedure (neonatal period). The pulmonary artery is connected to the (reconstructed) aortic arch (Norwood: a Damus-Kaye-Stansel + homograft patch augmentation of the arch), atrial septectomy, and a modified Blalock-Taussig shunt or right-ventricle-to-pulmonary-artery (Sano) conduit provides pulmonary blood flow. The RV is the systemic ventricle pumping to both circuits in parallel.
2. Stage 2 — Bidirectional Glenn (superior cavopulmonary anastomosis, 4–6 months). The SVC is disconnected from the RA and anastomosed end-to-side to the right pulmonary artery; the BT shunt is taken down. Half the venous return now flows passively to the lungs.
3. Stage 3 — Fontan completion (2–4 years). The IVC flow is routed to the pulmonary artery via an extracardiac conduit or lateral tunnel, completing the total cavopulmonary connection (TCPC). The right heart is bypassed for pulmonary flow. [1]

Fontan physiology and complications. The Fontan circulation is fundamentally non-physiological: there is no sub-pulmonary pump, so pulmonary blood flow depends entirely on favourable venous pressure, low PVR, and unobstructed pathways, and on the suction effect of systemic ventricular diastole. Survivors reach adulthood but face a predictable set of problems collectively called "Fontan failure": [1]

• Protein-losing enteropathy (PLE) — intestinal lymphatic congestion → loss of protein and lymphocytes in stool; hypoalbuminaemia, oedema, recurrent infections. Poor prognostic marker.
• Plastic bronchitis — acellular mucinous bronchial casts causing airway obstruction.
• Atrial arrhythmia (especially atrial flutter, common with the older atriopulmonary Fontan variants).
• Fontan-associated liver disease (FALD) — chronic venous congestion → fibrosis/cirrhosis → hepatocellular carcinoma surveillance needed.
• Thromboembolism — sluggish venous flow in the Fontan pathway; most patients are anticoagulated.
• Declining ventricular function — the systemic RV (in HLHS) eventually fails; heart transplantation is the rescue therapy. [1]

Ebstein Anomaly

Ebstein anomaly (under 1 percent of CHD) is characterised by apical displacement of the septal and posterior leaflets of the tricuspid valve into the RV, so part of the RV is "atrialised" (thin-walled, high-pressure) and the functional RV is small. The valve is severely regurgitant. Almost universally associated with right atrial dilatation, an ASD/PFO (~80%), and accessory pathway-mediated arrhythmias (Wolff-Parkinson-White). [1]

Clinical features. Range from severe neonatal cyanosis (massive tricuspid regurgitation with right-to-left atrial shunting, often fatal) to an asymptomatic adult with palpitations, Wolff-Parkinson-White, and a murmur. The classic murmur is a triple or quadruple heart sound (split S1 from delayed tricuspid closure, plus S3, S4) and a pansystolic murmur of tricuspid regurgitation at the lower left sternal edge that increases with inspiration (Carvallo sign). Maternal lithium use in the first trimester is a classic risk factor (relative risk ~10). CXR may show massive cardiomegaly ("wall-to-wall heart") with a small pedicle. [1]

Management. Symptomatic neonates may need PGE1 (duct-dependent pulmonary flow if severe RV dysfunction) and occasionally surgical intervention (Starnes procedure — right ventricular exclusion, or tricuspid valve repair/cone reconstruction in older patients). The Cone reconstruction (da Silva) has become the surgical standard, restoring a competent tricuspid valve from the patient's own tissue. [1]

Truncus Arteriosus

Persistent truncus arteriosus (under 1 percent of CHD) results from failure of conotruncal septation — a single great vessel arises from the heart, giving origin to the aorta, pulmonary arteries and coronary arteries, overriding a large VSD. Strongly associated with 22q11.2 deletion (DiGeorge syndrome) — always test these children with FISH/microarray. The truncal valve is often regurgitant. [1]

Clinical features. Mild cyanosis with heart failure (large left-to-right shunt into the pulmonary arteries once PVR falls) in the first weeks of life; a loud single S2 (only one semilunar valve) and an ejection click. Untreated, most die within the first year of intractable heart failure or pulmonary vascular disease. [1]

Management. Surgical repair in the neonatal period: VSD closure so the truncal root becomes the aorta, and a right-ventricle-to-pulmonary-artery conduit (Rastelli-type) to restore pulmonary flow. The conduit does not grow — patients face multiple re-operations to up-size the conduit over childhood and adulthood. [1]

Total Anomalous Pulmonary Venous Drainage (TAPVD)

TAPVD (~1% of CHD) = all four pulmonary veins drain into the systemic venous circulation instead of the left atrium. An obligate right-to-left shunt at atrial level (ASD/PFO) delivers mixed blood to the systemic circulation, producing cyanosis. Three anatomical types: [1]

• Supracardiac (50%) — pulmonary veins drain to a vertical vein → left brachiocephalic vein → SVC. The CXR shows the classic "snowman" (figure-of-eight) sign from the dilated vertical vein and SVC.
• Cardiac (25%) — drain to the coronary sinus (or directly to the RA).
• Infradiaphragmatic (20%) — drain via a vertical vein through the diaphragm to the portal vein or IVC. This is the most dangerous form because the vein often passes through the diaphragmatic hiatus and becomes obstructed → severe pulmonary venous congestion. [1]

Clinical features. Obstructed TAPVD presents in the neonatal period with severe cyanosis, respiratory distress, and pulmonary oedema — a sick neonate with a near-normal heart size and a "ground-glass" lung appearance on CXR. Unobstructed TAPVD presents later with mild cyanosis, heart failure, and a fixed split S2. Echocardiography is diagnostic (no pulmonary venous return to LA; dilated RA/RV/coronary sinus). [1]

Management. Emergency surgical anastomosis of the confluence of pulmonary veins to the left atrium, closing the ASD and ligating the anomalous vertical vein — the only definitive treatment, and a true surgical emergency in the obstructed form. [1]

Tricuspid Atresia

Tricuspid atresia (~1% of CHD) is complete absence of the tricuspid valve, so there is no direct RA→RV flow. Systemic venous blood crosses an obligate ASD to the LA, mixes with pulmonary venous return, and enters the LV. Pulmonary blood flow depends on a VSD (to a hypoplastic RV) and/or a PDA. The lesion is duct-dependent if the VSD is small/restrictive or there is pulmonary stenosis. [1]

Clinical features. Cyanosis from birth. ECG is diagnostic in a cyanotic neonate: left-axis deviation (superior axis), LVH, small RA waves — the only common cyanotic CHD with left-axis deviation on ECG, a favourite exam pearl. Right atrial enlargement on ECG ("P pulmonale"/P mitrale). Echo shows an echogenic band at the tricuspid position and a small RV. [1]

Management. Staged single-ventricle palliation to a Fontan circulation (same pathway as HLHS): PGE1 if duct-dependent → modified BT shunt or pulmonary artery band (depending on whether pulmonary flow is too little or too much) at the neonatal stage → bidirectional Glenn at 4–6 months → Fontan completion at 2–4 years. [1]

Atrioventricular Septal Defect (AVSD)

AVSD (endocardial cushion defect, 4–5% of CHD) is the failure of fusion of the endocardial cushions that form the lower atrial septum, upper ventricular septum, and the AV valve leaflets. Two forms: [1]

• Complete AVSD — primum ASD + inlet VSD + a common AV valve (single valve straddling both ventricles). Strongly associated with Down syndrome (trisomy 21) — about 40–50% of children with Down syndrome have CHD, and ~40% of those have AVSD; any neonate with AVSD must be tested for trisomy 21.
• Partial / incomplete AVSD — primum ASD + cleft anterior mitral valve leaflet (causing mitral regurgitation), no VSD. [1]

Clinical features. Complete AVSD presents early with heart failure and FTT by 4–8 weeks (large left-to-right shunt once PVR falls), recurrent chest infections, and early-onset pulmonary hypertension (this population progresses to Eisenmenger faster than isolated VSD — surgery by 3–6 months). Murmur: pansystolic (AV valve regurgitation or VSD) at LSE, plus the fixed split S2 of an ASD. [1]

Management. Surgical repair by 3–6 months (before irreversible pulmonary vascular disease): closure of the primum and inlet defects with a single or two patches, and reconstruction ("cleft closure") of the common AV valve into competent mitral and tricuspid valves. Post-operative left AV valve regurgitation is the commonest reason for re-operation. [1]

Duct-Dependent Circulation

A duct-dependent lesion is one in which the ductus arteriosus is essential for survival — either because it carries systemic blood to the body (duct-dependent systemic flow: HLHS, critical aortic stenosis, severe coarctation, interrupted aortic arch) or because it carries unoxygenated blood to the lungs (duct-dependent pulmonary flow: critical pulmonary stenosis, pulmonary atresia, severe TOF, tricuspid atresia), or because it provides mixing (TGA). At birth these infants are typically well, then collapse suddenly at 24–72 hours as the duct closes, presenting with cyanosis unresponsive to oxygen, shock, profound metabolic acidosis, and oliguria. The differential is septic shock and metabolic disease — but every sick neonate must be assumed to have CHD until proven otherwise. [1]

Exam application bank (NEET-PG / INICET)

One-line answer

Congenital heart disease (CHD) = structural heart defect present at birth. Incidence: 8-9 per 1000 live births. Classification: acyanotic (left-to-right shunt: VSD, ASD, PDA, AVSD; obstructive: coarctation, AS, PS) vs cyanotic (right-to-left shunt: TOF, TGA, tricuspid atresia, TAPVD, HLHS). Duct-dependent lesions (TGA, HLHS, critical PS/AS, severe coarctation) present with collapse at duct closure — maintain PGE1. Hyperoxia test distinguishes cardiac from pulmonary cyanosis.

Worked stems (answer without another resource)

Stem 1 — Classic presentation. Map symptoms to mechanism; name the first investigation and first treatment step with dose/route if drug therapy is standard. [1]

Stem 2 — Unstable / complicated. List red flags that force immediate resuscitation, theatre, ICU, antidote, or reperfusion — and what you do in the first 15 minutes. [1]

Stem 3 — Atypical group. Elderly, pregnancy, child, or immunocompromised: how presentation and thresholds change. [1]

Stem 4 — Differential trap. Name the three closest mimics and one discriminator for each. [1]

Stem 5 — Disposition. Who goes home with safety-netting, who is admitted, who needs HDU/ICU/theatre, and what follow-up is mandatory. [1]

Rapid viva checklist

1. Definition + classification
2. Pathophysiology chain
3. Bedside signs / criteria
4. Score with exact components (if any)
5. Emergency bundle
6. Definitive therapy with doses
7. Complications of disease and of treatment
8. Special populations
9. Guideline/trial name if classic
10. Three exam traps

Coverage self-check

If you cannot answer any stem above from this page alone, re-read the matching section — the page is intended to be self-sufficient for final-prof and NEET-PG/INICET questions on Congenital Heart Disease.

[1]

The neonatal collapse protocol: [1]

1. ABCDE resuscitation — airway, breathing (intubate/ventilate if apnoeic or severe acidosis), circulation (two large-bore IV/IO access).
2. Start PGE1 (alprostadil) 0.05–0.1 mcg/kg/min IV immediately on suspicion — before any diagnostic confirmation. Apnoea is the dose-limiting side effect (~10%); have intubation equipment ready. Other side effects: fever, hypotension, flushing, diarrhoea. If apnoea occurs, intubate and continue PGE1.
3. Prostaglandins keep the ductus open by mimicking the circulating PGE2 that maintained ductal patency in utero. Do NOT routinely give 100% oxygen — it lowers PGE levels and constricts the duct, and worsens the pulmonary-over-systemic flow ratio in many lesions.
4. Septic and metabolic workup — blood cultures, CRP, glucose, lactate, ammonia, blood gas; start empirical antibiotics.
5. Echocardiography is the definitive diagnostic test — performed once the child is stabilised, ideally at the receiving cardiac centre.
6. Transfer to a paediatric cardiac centre on PGE1 with a trained neonatal transfer team; ventilate if PGE1 causes apnoea or for transport safety.
7. Definitive management — surgery or catheter intervention as appropriate for the specific lesion. [1]

Hyperoxia Test

The hyperoxia test is the bedside manoeuvre that distinguishes cardiac from pulmonary causes of neonatal cyanosis, exploiting the fact that a right-to-left shunt delivers deoxygenated blood directly into the systemic arterial tree, bypassing the lungs. [1]

Technique. Place the neonate in 100% oxygen for 10 minutes (hood or endotracheal), then measure an arterial blood gas from the right radial artery (pre-ductal). [1]

Interpretation: [1]

• PaO₂ > 150 mmHg (20 kPa) → the cyanosis is pulmonary (diffusion/ventilation problem). Cyanotic CHD is essentially excluded.
• PaO₂ < 100 mmHg (13 kPa) → strongly suggests a cardiac cause (right-to-left shunting).
• PaO₂ 100–150 mmHg — equivocal; repeat or proceed to echocardiography. [1]

Important caveats. (1) The test only detects cyanotic CHD with a fixed right-to-left shunt — it is normal in acyanotic CHD. (2) Hypoxaemic pulmonary disease with severe V/Q mismatch can also fail the test, giving a false positive. (3) In duct-dependent systemic lesions (e.g., HLHS, coarctation), a simultaneous right radial (pre-ductal) and lower-limb (post-ductal) PaO₂ may show a gradient indicating differential cyanosis. (4) Modern practice increasingly bypasses the hyperoxia test in favour of early echocardiography and pulse-oximetry screening; persistent pre-ductal SpO₂ < 95% or a >3% differential between right-hand and foot at 24 hours is a positive newborn screen for CHD. [1]

Detailed Pathophysiology by Lesion

Left-to-Right Shunting (Acyanotic)

VSD pathophysiology:

• Blood flows from high-pressure LV to lower-pressure RV during systole
• Increased pulmonary blood flow → increased pulmonary venous return to LA → LV volume overload → LA and LV dilation
• Large VSD: equalisation of LV and RV pressures → pulmonary hypertension (Eisenmenger)
• Natural history: 75% of small muscular VSDs close spontaneously by age 2 (fibrous proliferation)
• The shunt magnitude (Qp:Qs) determines symptoms: < 1.5:1 trivial; 1.5–2.5:1 moderate; > 2.5:1 large with heart failure and FTT
• Progressive pulmonary vascular remodelling if uncorrected: medial hypertrophy → intimal hyperplasia → plexiform arteriopathy → irreversible by ~2 years for large VSDs [1]

ASD pathophysiology:

• Blood flows from LA to RA during late systole/diastole (LA pressure higher)
• RV volume overload → RV dilation → RV hypertrophy
• Fixed split S2: delayed PV closure (RV volume overload) + no respiratory variation (LA-RA pressure equalised)
• Risk: paradoxical embolism (DVT → RA → LA → brain stroke)
• Stroke volume is preserved by the Frank-Starling mechanism for decades, which explains the long asymptomatic latent period [1]

PDA pathophysiology:

• Continuous flow from aorta (high pressure) to PA (low pressure) throughout cardiac cycle
• Machinery murmur (continuous, maximal at upper left sternal edge/infraclavicular)
• Bounding pulses (wide pulse pressure from diastolic run-off into PA)
• In premature infants: contributes to respiratory distress, necrotising enterocolitis, IVH
• Large PDA, like VSD, can progress to Eisenmenger with time [1]

Right-to-Left Shunting (Cyanotic)

TOF pathophysiology:

• VSD allows RV blood to preferentially flow into the overriding aorta (bypassing the stenotic pulmonary outflow tract)
• Degree of cyanosis inversely proportional to severity of RVOT obstruction
• Tet spell (hypercyanotic spell) pathophysiology:
  1. Infundibular spasm (sudden increase in RVOT obstruction)
  2. Decreased pulmonary blood flow
  3. Increased R-to-L shunt through VSD
  4. Sudden profound cyanosis, agitation
  5. Management: knee-chest (increases SVR → more blood through RVOT to lungs), oxygen, morphine (reduces catecholamine surge → reduces infundibular spasm), phenylephrine (alpha-agonist → increases SVR), propranolol (beta-blocker → reduces infundibular spasm) [1]

TGA pathophysiology:

• Aorta arises from RV (deoxygenated blood to body)
• Pulmonary artery arises from LV (oxygenated blood returns to lungs)
• Two parallel circulations — survival requires mixing (PDA, ASD, VSD)
• Without mixing: severe hypoxaemia, death within hours-days
• PGE1 keeps ductus open → some mixing at ductal level
• Balloon septostomy (Rashkind): enlarges ASD → improved atrial mixing [1]

TAPVD pathophysiology:

• All pulmonary venous blood returns to the RA (not LA), mixes with systemic venous blood, then crosses an ASD to reach the LA
• An obligate right-to-left shunt at atrial level → cyanosis
• Obstructed infradiaphragmatic TAPVD: pulmonary venous hypertension → pulmonary oedema, reflex pulmonary vasoconstriction, severe hypoxaemia [1]

Tricuspid atresia pathophysiology:

• No RA-to-RV flow; all systemic venous return crosses an ASD to the LA
• LV pumps mixed blood to the aorta; pulmonary flow is via a VSD into a small RV or via a PDA
• Cyanosis obligatory; degree depends on pulmonary blood flow [1]

Obstructive Lesions

Coarctation pathophysiology:

• Narrowing at isthmus (distal to left subclavian artery origin)
• Upper body hypertension (perfused by proximal aorta)
• Lower body hypoperfusion (perfused by collaterals — intercostal, subclavian, internal mammary)
• Collateral development over time → rib notching (dilated intercostal arteries erode inferior rib margins)
• Differential cyanosis: upper body pink, lower body blue (if severe + PDA delivers deoxygenated blood to lower body) [1]

Critical aortic stenosis:

• Duct-dependent systemic circulation (LV output inadequate)
• Presents with cardiogenic shock at duct closure
• Management: PGE1 → balloon valvuloplasty or surgical valvotomy [1]

Critical pulmonary stenosis / pulmonary atresia:

• Duct-dependent pulmonary circulation
• RV cannot eject against the stenotic/atretic valve; systemic venous blood crosses an ASD/PFO to the LA, and pulmonary flow is entirely via the ductus
• Management: PGE1 → balloon valvuloplasty (critical PS) or RVOT surgery / catheter-based valve implantation [1]

Detailed Management by Lesion

VSD Management Algorithm

Indications for surgical closure:

• Symptomatic despite maximal medical therapy (FTT, recurrent infections)
• Qp:Qs > 2:1 with cardiomegaly
• Aortic regurgitation developing from cusp prolapse (especially outlet VSDs)
• Documented pulmonary hypertension that is still reactive (PVR < 8 Wood units and reactive to oxygen/NO)
• Subaortic or double-chambered RV obstruction developing
• Endocarditis (even one episode) on the VSD [1]

Medical bridge to surgery:

• Furosemide 1mg/kg BD + spironolactone 1mg/kg BD (diurese pulmonary oedema)
• Captopril (ACE inhibitor) — reduces afterload → less shunting
• High-calorie feeds (120-150 kcal/kg/day) for FTT
• Immunisations up to date (especially pneumococcal, influenza, RSV prophylaxis) [1]

Surgical technique. Patch closure (Dacron or pericardium) via right atriotomy is standard; the tricuspid valve may be detached and re-attached for access to perimembranous defects. Outlet VSDs and those with aortic cusp prolapse may be closed via the aortic root. Catheter-based device closure is increasingly used for selected muscular VSDs (which are surgically inaccessible). [1]

ASD Management

Indications for closure. Right heart volume overload on echo (RV dilation), paradoxical embolism (cryptogenic stroke), significant shunt (Qp:Qs > 1.5:1), or symptoms. Closure is contraindicated in severe irreversible pulmonary hypertension (Eisenmenger) — closing the defect removes the "pop-off" and precipitates RV failure. [1]

PDA Management

TOF Surgical Repair

Staged repair:

1. Blalock-Taussig (BT) shunt (palliative, if needed early): subclavian artery to pulmonary artery anastomosis — increases pulmonary blood flow
2. Complete repair (4-6 months):
   • VSD patch closure (Dacron patch via right atriotomy)
   • RVOT relief (resection of infundibular muscle, pulmonary valvotomy, transannular patch if needed)
   • Preserve pulmonary valve function if possible (valve-sparing repair)
3. Post-operative: pulmonary regurgitation common (may need pulmonary valve replacement in adulthood) [1]

TGA Surgical Repair

Arterial switch (Jatene) — operation of choice:

1. Performed within first 2 weeks of life (before LV involutes to low-pressure pumping)
2. Great arteries transected and re-anastomosed in correct position
3. Coronary arteries re-implanted to neo-aorta (critical step)
4. VSD and ASD closed
5. Results: 95%+ survival, excellent long-term outcomes [1]

Atrial switch (Mustard/Senning) — historical:

• Redirects venous flow at atrial level (systemic venous blood → mitral valve → LV → pulmonary artery; pulmonary venous blood → tricuspid valve → RV → aorta)
• RV remains systemic ventricle → long-term RV failure, arrhythmias
• No longer performed (replaced by Jatene) [1]

Eisenmenger Syndrome

Definition: irreversible pulmonary vascular disease (pulmonary artery pressure exceeds systemic pressure) with shunt reversal (left-to-right becomes right-to-left → cyanosis). Named after Victor Eisenmenger (1897). The end-stage of every uncorrected large left-to-right shunt. [1]

Pathophysiology:

1. Uncorrected L-to-R shunt → increased pulmonary blood flow
2. Shear stress and endothelial dysfunction → pulmonary vascular remodelling
3. Medial hypertrophy, intimal fibrosis, plexiform lesions
4. Pulmonary vascular resistance exceeds systemic → shunt reversal (R-to-L)
5. Cyanosis, clubbing, secondary polycythaemia [1]

Clinical features:

• Cyanosis, clubbing, exercise intolerance
• Haemoptysis (ruptured plexiform lesions)
• Paradoxical embolism (stroke, abscess)
• Secondary polycythaemia (hypoxaemia-driven erythropoietin)
• Right heart failure (cor pulmonale) [1]

Examination hallmarks. Differential cyanosis (lower limbs only — patent ductus with Eisenmenger) or generalised cyanosis; loud P2, right ventricular heave, palpable pulmonary valve closure, pansystolic TR murmur, elevated JVP with prominent "a" and "v" waves. Eisenmenger PDA is the classic viva case — the lower body is cyanosed and clubbed, the upper body is pink, and there is no continuous murmur (pressures are equal across the duct so no turbulent flow). [1]

Management:

• Corrective surgery is CONTRAINDICATED (closing the shunt removes the 'pop-off' → acute RV failure)
• Targeted PAH therapy: bosentan (endothelin antagonist), sildenafil (PDE5 inhibitor), IV epoprostenol (prostacyclin)
• Supportive: oxygen, iron supplementation (avoid dehydration), phlebotomy only if hyperviscosity symptoms (Hct over 65%)
• Pregnancy: contraindicated (30-50% maternal mortality)
• Heart-lung transplant for end-stage disease [1]

Prevention: early surgical correction of CHD (before 6 months for large VSD, before 2 years for complex lesions) prevents Eisenmenger development [1]

Infective Endocarditis Prophylaxis

Infective endocarditis (IE) prophylaxis has been progressively narrowed over successive AHA/ECS guideline iterations, because the absolute risk reduction from antibiotics is vanishingly small and most cases arise from incidental bacteraemia (tooth brushing, daily activities) rather than procedures. The current AHA 2007 (affirmed 2021) and AHA 2024 scientific statement restrict antibiotic prophylaxis to a small high-risk subgroup. [1]

Who needs prophylaxis (the only groups now recommended): [1]

1. Prosthetic cardiac valves or prosthetic material used for valve repair (including transcatheter-implanted prostheses and homografts).
2. Previous infective endocarditis.
3. Certain congenital heart disease:
   • Unrepaired cyanotic CHD, including palliative shunts and conduits.
   • Completely repaired CHD with prosthetic material or device, during the first 6 months after the procedure (endothelialisation is complete by 6 months).
   • Repaired CHD with residual defects adjacent to a prosthetic patch or device (which prevents endothelialisation).
4. Cardiac transplant recipients who develop cardiac valvulopathy (valve regurgitation due to structurally abnormal valve). [1]

Who does NOT need prophylaxis any longer (and over-prescription is now considered a quality issue): isolated secundum ASD; VSD and PDA more than 6 months after complete repair without residual shunt; repaired ASD/PDA/VSD without residual lesion; previous rheumatic fever without prosthetic material; bicuspid aortic valve without prosthetic material; mitral valve prolapse with or without regurgitation; innocent murmurs; pacemakers and defibrillators. The Fontan circulation is generally included in the high-risk group (unrepaired cyanotic-equivalent physiology, prosthetic material, sluggish flow). [1]

Procedures for which prophylaxis is indicated (limited to dental procedures involving manipulation of gingival tissue or periapical region, or perforation of oral mucosa — the only procedures for which the AHA still endorses prophylaxis). Prophylaxis is no longer routinely recommended for routine genitourinary, gastrointestinal, dermatological or respiratory procedures in this population. [1]

Antibiotic regimen (AHA) — dental procedures: [1]

• Amoxicillin 50 mg/kg orally (max 2 g) single dose, 30–60 minutes before the procedure — first-line.
• If unable to take oral: ampicillin 50 mg/kg IM/IV (max 2 g) or cefazolin/ceftriaxone 50 mg/kg IM/IV (max 1 g).
• Penicillin allergy: clindamycin 20 mg/kg (max 600 mg) PO/IV, or azithromycin/clarithromycin 15 mg/kg (max 500 mg) PO, or cephalexin 50 mg/kg (max 2 g) PO (if not anaphylaxis-type allergy). [1]

General measures equally important: meticulous dental hygiene, avoidance of body piercing/tattooing, prompt treatment of skin infections, and patient education to seek medical attention for unexplained fever with bacteraemic illness. [1]

Genetic Associations and Syndromic CHD

CHD is frequently syndromic, and recognising the pattern narrows the cardiac differential instantly: [1]

A neonate with a heart murmur + dysmorphic features warrants a karyotype / chromosomal microarray. Conversely, every baby with a known syndrome needs a screening echocardiogram. [1]

Investigations in Suspected CHD

A structured workup confirms the anatomy and physiology: [1]

1. Pulse oximetry screening (routine at 24 hours) — pre-ductal SpO₂ < 95% or > 3% arm-foot differential is positive.
2. Four-limb blood pressures — arm-leg gradient suggests coarctation.
3. ECG — chamber enlargement, axis deviation (left-axis deviation + cyanosis = think tricuspid atresia; RVH + cyanosis = TOF; RVH + RAD = TGA/TAPVD).
4. Chest X-ray — heart size and shape, pulmonary vascularity (oligaemic = cyanotic obstructive; plethoric = left-to-right shunt). Classic silhouettes: boot-shaped (TOF), egg-on-string (TGA), snowman (supracardiac TAPVD), scimitar sign (PAPVD).
5. Echocardiography — the definitive, first-line, non-invasive diagnostic test. Defines anatomy, shunts, valve function, ventricular function, arch, ductus. Almost always sufficient to plan intervention.
6. Cardiac MRI / CT — for complex anatomy, aortic arch anomalies, vascular rings, and pre-surgical planning.
7. Cardiac catheterisation — reserved for haemodynamic assessment (PVR, shunt quantification, response to oxygen/NO), catheter-based interventions (device closure, balloon valvuloplasty/septostomy, stenting), and pre-transplant assessment. [1]

Follow-up and Long-term Care

CHD is a lifelong condition, even after successful repair. The transition to adult congenital heart disease (ACHD) services is now a recognised standard of care — every repaired patient needs lifelong follow-up at an ACHD centre, the frequency depending on the lesion. [1]

Key long-term issues by lesion: [1]

• VSD post-repair: residual VSD, aortic regurgitation (outlet VSD), complete heart block (rare), endocarditis risk on residual shunts.
• ASD post-closure: atrial arrhythmias (especially after late closure), device erosion/embolisation (rare).
• TOF post-repair: pulmonary regurgitation (almost universal after transannular patch — needs pulmonary valve replacement, often transcatheter), RV dilatation, residual VSD, RVOT aneurysm, ventricular tachycardia/sudden death (late), aortic root dilatation.
• TGA post-Jatene: coronary ostial stenosis, supravalvar pulmonary stenosis, neo-aortic root dilatation, branch PA stenosis.
• TGA post-Mustard/Senning: systemic RV failure, atrial arrhythmias (atrial flutter/fibrillation), baffle obstruction/leak — a major source of adult morbidity; many ultimately need heart transplantation.
• Coarctation post-repair: re-coarctation, persistent systemic hypertension (even after successful repair, due to altered arch compliance and renin-angiotensin activation), berry aneurysms, premature coronary disease.
• Fontan circulation: see above — PLE, plastic bronchitis, FALD, arrhythmia, thromboembolism, ventricular failure. [1]

General principles of long-term care:

• Exercise recommendations based on lesion severity (most repaired patients can exercise competitively; restrictions for unrepaired cyanotic disease, Marfan with aortic dilatation, WPW, severe pulmonary hypertension).
• Contraception and pregnancy counselling — pregnancy is contraindicated in Eisenmenger and severe pulmonary hypertension (maternal mortality 30–50%) and high-risk in Fontan failure and systemic RV; otherwise most repaired patients tolerate pregnancy well but need cardiology input.
• IE prophylaxis as above.
• ACHD transition — formal handover at age 16–18 from paediatric to adult services, with the patient educated about their lesion, prior operations, and red flags. [1]

Examination Tips and Common Viva Questions

Murmur location quick map: [1]

High-yield one-liners:

• Most common CHD overall: VSD. Most common cyanotic CHD: TOF. Most common cyanotic lesion in neonate: TGA.
• Cyanosis + left-axis deviation on ECG: think tricuspid atresia.
• Cyanosis + boot-shaped heart: TOF.
• Cyanosis + egg-on-string heart: TGA.
• Cyanosis + snowman/figure-of-eight heart: supracardiac TAPVD.
• Cyanosis + ground-glass lungs + normal heart size: obstructed infradiaphragmatic TAPVD.
• Differential cyanosis (pink upper, blue lower): PDA with Eisenmenger or preductal coarctation.
• Bounding pulses + wide pulse pressure + continuous murmur: PDA.
• Radio-femoral delay + arm-leg BP gradient + rib notching: coarctation (older child).
• Triple/quadruple heart sound + WPW + maternal lithium: Ebstein.
• AVSD + Down syndrome — always test karyotype.
• Conotruncal lesion + hypocalcaemia + absent thymus: 22q11.2 deletion (DiGeorge).
• Pulmonary stenosis + cocktail-party personality + elfin facies: Williams syndrome.
• Newborn cyanosis at 24–72 h with shock: duct-dependent lesion — start PGE1 NOW.
• PGE1 side effects: apnoea (~10%), fever, hypotension, flushing.
• IE prophylaxis only for: prosthetic valve, previous IE, unrepaired cyanotic CHD, repaired with prosthetic material under 6 months or with residual defect, transplant valvulopathy. [1]

Mnemonics Summary

• 5 Ts of cyanotic CHD — Tetralogy, Transposition, Tricuspid atresia, Truncus, TAPVD (+ HLHS).
• TOF PROVe — Pulmonary stenosis, RVH, Overriding aorta, VSD.
• Duct-dependent lesions — the 5 "collapsers": TGA, HLHS, critical AS, critical PS/severe coarctation, interrupted aortic arch.
• VSD types — Perimembranous (P), Muscular (M), Inlet (I), Outlet (O): "PMIO".
• ASD types — Secundum (most, device), Primum (Down), Sinus venosus (anomalous venous drainage, surgery).
• Eisenmenger complications — CHOPS: Cyanosis, Haemoptysis, Oedema (RV failure), Paradoxical embolism, Syncope/secondary polycythaemia.
• Tet spell management — "COME-MIPP": Calm/Knee-chest, Oxygen, Morphine, Estates (fluid bolus), Phenylephrine, Propranolol. [1]

Prognosis and Public Health

With modern paediatric cardiology and cardiac surgery, over 90% of children with CHD now survive to adulthood — most with near-normal life expectancy. The result is a growing population of adults with CHD (currently estimated at ~1.4 million in the US and rising), outstripping the paediatric CHD population. Key determinants of outcome are early diagnosis (antenatal ultrasound, newborn pulse-oximetry screening), prompt transfer to a cardiac centre before duct closure for duct-dependent lesions, complete repair before irreversible pulmonary vascular disease, and lifelong structured follow-up in dedicated ACHD services. In low- and middle-income countries, where access to cardiac surgery is limited, late presentation with Eisenmenger syndrome and unrepaired complex CHD remains a leading cause of childhood cardiac mortality — the global burden of CHD is the next frontier for paediatric cardiac care. [1]

References

1. [1]van der Linde D, Konings EEM, Slager MA, Witsenburg M, Helbing WA, Takkenberg JJM, Roos-Hesselink JW. Birth prevalence of congenital heart disease worldwide: a systematic review and meta-analysis. J Am Coll Cardiol, 2011.PMID 22078432