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Congenital Heart Diseases (CHD) in Pediatrics

Definition & Epidemiology

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Frequency of Congenital Cardiac Malformations

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Pathogenesis / Risk Factors

• Prematurity, family history
• Maternal conditions: diabetes, hypertension, obesity, PKU, thyroid disorders, connective tissue disorders
• Teratogenic drugs: phenytoin, retinoic acid; smoking; alcohol
• Genetic disorders: Trisomy 21 (Down's), Trisomy 18, Trisomy 13, Turner syndrome, Noonan syndrome
• In utero infections: rubella (most classic), CMV, coxsackievirus, parvovirus B19, toxoplasmosis
• ~10% of defects are associated with genetic syndromes (VACTERL association, DiGeorge syndrome)

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Classification

1. Haemodynamic/clinical: Cyanotic vs. Acyanotic
2. Anatomic defect: Shunt, obstruction, transposition, or complex

Classification at a Glance

Cyanotic lesions = the "Five Ts": Tetralogy of Fallot, Tricuspid anomalies (atresia, Ebstein's), Truncus arteriosus, Total anomalous pulmonary venous return, Transposition of great arteries.

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Physiology of Shunts

• Left → Right shunt: No early cyanosis. Increases pulmonary blood flow → RV hypertrophy → if untreated, leads to pulmonary hypertension → shunt reversal (R→L) = Eisenmenger syndrome with late cyanosis.
• Right → Left shunt: Immediate cyanosis (poorly oxygenated blood enters systemic circulation). Associated with polycythemia, clubbing, hypoxic spells.

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ACYANOTIC HEART DISEASES

1. Ventricular Septal Defect (VSD)

• Defect: Opening in the interventricular septum; 90% are in the membranous (perimembranous/subarterial) region
• Physiology: L→R shunt → pulmonary overcirculation → if large, LV failure
• Clinical features:
  • Small VSD: Loud, harsh pansystolic murmur at left lower sternal border (LLSB); often asymptomatic; "Maladie de Roger"
  • Large VSD: Poor feeding, failure to thrive, recurrent respiratory infections, tachycardia, hepatomegaly, CHF
• Investigations: CXR — cardiomegaly, increased pulmonary vascular markings; Echo is diagnostic
• Management: Most small VSDs close spontaneously (by 2 years). Large VSDs require surgical patch closure or catheter-based device closure. Diuretics (furosemide) + digoxin for CHF

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2. Atrial Septal Defect (ASD)

• Ostium secundum (90%): Near foramen ovale; isolated defect
• Ostium primum (5%): Lower atrial septum; associated with mitral/tricuspid valve anomalies; part of AVSD spectrum
• Sinus venosus (5%): High in atrial septum; associated with anomalous pulmonary venous drainage
• Clinical features: Usually asymptomatic in childhood. Fixed splitting of S2 (hallmark), systolic ejection murmur at left upper sternal border (pulmonary flow murmur), mid-diastolic murmur at tricuspid area (flow)
• Complications: Atrial arrhythmias, right heart failure, pulmonary hypertension, paradoxical embolism
• Management: Device closure (catheter-based, for secundum) or surgical closure. Patent foramen ovale (PFO) ≠ true ASD — usually closes spontaneously; can cause paradoxical embolism

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3. Patent Ductus Arteriosus (PDA)

• Defect: Persistence of the ductus arteriosus (fetal communication between aorta and pulmonary artery) after birth; normally closes within 15 hours–3 days of life
• At risk: Premature infants, maternal rubella, high altitude births
• Physiology: L→R shunt (Ao → PA); wide pulse pressure; bounding pulses
• Clinical features:
  • Continuous "machinery" murmur at left infraclavicular area (Gibson murmur), best heard at left 2nd intercostal space
  • Widened pulse pressure, collapsing/bounding pulses (Corrigan's pulse)
  • Signs of CHF in large PDA
• Investigations: CXR — cardiomegaly, increased pulmonary markings; Echo is definitive
• Management:
  • Premature infants: Indomethacin or Ibuprofen (COX inhibitors to close) IV
  • Term infants/children: Surgical ligation or catheter-based device (coil/Amplatzer)
  • Prostaglandin E1 (PGE1) is used to keep PDA open in duct-dependent lesions (e.g., pulmonary atresia, critical coarctation)

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4. Coarctation of the Aorta

• Defect: Discrete narrowing of the aorta, usually near the ductus arteriosus insertion (juxtaductal, most common); can be preductal (infantile) or postductal (adult type)
• Associated: Bicuspid aortic valve (50–85%), Turner syndrome (classic association)
• Clinical features:
  • Upper limb hypertension, weak/absent femoral pulses
  • BP differential: Upper extremities > lower extremities (>20 mmHg)
  • Systolic murmur (left infraclavicular/interscapular)
  • In neonates: Can present with cardiovascular collapse when PDA closes
  • Rib notching on CXR (in older children >6 yrs, from intercostal collaterals) — "3-sign" on CXR
• Management: Balloon angioplasty + stenting (catheter-based) or surgical resection. Recurrence in 10% of cases.

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5. Pulmonary Stenosis (PS)

• Defect: Narrowing at pulmonary valve (most common), subvalvular (infundibular), or supravalvular level
• Associated: Noonan syndrome (classic), Williams syndrome (supravalvular), congenital rubella
• Clinical features:
  • Systolic ejection murmur at left upper sternal border with ejection click
  • Widely split S2 (delayed P2)
  • RV heave; cyanosis only if severe (critical PS with R→L shunt through PFO/ASD)
• Management: Balloon pulmonary valvuloplasty (catheter-based); surgery for subvalvular/supravalvular

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6. Aortic Stenosis (AS)

• Defect: Obstruction at valvular (most common — bicuspid aortic valve), subvalvular, or supravalvular level
• Clinical: Systolic ejection murmur radiating to neck; exertional syncope, angina, dyspnea (classical triad in older children)
• Critical AS in neonates: Duct-dependent systemic circulation; presents with severe CHF/shock
• Management: Balloon valvuloplasty or surgical valve repair/replacement

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CYANOTIC HEART DISEASES

1. Tetralogy of Fallot (TOF) — Most common cyanotic CHD

1. Pulmonary stenosis (infundibular/valvular)
2. Right ventricular hypertrophy (RVH)
3. Overriding aorta (dextroposition — sits over VSD)
4. Ventricular septal defect (large, perimembranous)

The primary defect is anterior malalignment of the infundibular septum → causes all four components.

• Clinical features:
  • Cyanosis (worsening with age and after feeding/exertion)
  • Hypercyanotic ("Tet") spells: Paroxysmal hyperpnea, increasing cyanosis, squatting behaviour (squatting increases SVR → decreases R→L shunt); peak 2–4 months–2 years
  • Clubbing of fingers and toes (chronic hypoxemia)
  • Single S2 (pulmonary component absent), harsh systolic ejection murmur at LUSB (due to RVOTO, not VSD)
• Investigations:
  • CXR: "Boot-shaped heart" (coeur en sabot) — upturned apex from RVH, concave pulmonary bay, right-sided aortic arch (25%)
  • ECG: Right axis deviation, RVH
  • Echo: Diagnostic
• Management:
  • Acute Tet spell: Knee-chest position, 100% O2, IV morphine, propranolol, phenylephrine (↑ SVR), IV fluid bolus
  • Definitive: Total surgical correction (patch VSD, relieve RVOTO); optimal at 3–6 months
  • Palliative (before correction): Blalock-Taussig shunt (subclavian → pulmonary artery)

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2. Transposition of the Great Arteries (TGA) — Most common cyanotic CHD presenting in neonates

• Defect: Aorta arises from RV; Pulmonary artery arises from LV → two parallel circulations (incompatible with life unless mixing exists via PFO/ASD/VSD/PDA)
• Clinical: Severe cyanosis from birth, no murmur (unless associated VSD/PS), tachypnea
• CXR: "Egg-on-side" heart (narrow mediastinum), increased pulmonary vascularity
• Management:
  • Immediate: PGE1 (keep PDA open), balloon atrial septostomy (Rashkind procedure) to increase mixing
  • Definitive: Arterial switch operation (Jatene) — reconnects aorta to LV and PA to RV; done in first 2 weeks of life

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3. Tricuspid Atresia

• Defect: Complete absence of tricuspid valve → no direct communication between RA and RV; requires ASD (mandatory) + VSD or PDA for survival
• Clinical: Cyanosis from birth, single S2, hepatomegaly; LV hypertrophy on ECG (unusual for cyanotic CHD)
• Management: Palliative Blalock-Taussig shunt → Fontan procedure (connecting IVC/SVC directly to pulmonary artery)

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4. Truncus Arteriosus

• Defect: Single arterial trunk arising from both ventricles (via large VSD), giving rise to systemic, pulmonary, and coronary circulations
• Clinical: Mild cyanosis, loud S2, harsh systolic murmur; early CHF from pulmonary overcirculation
• Association: DiGeorge syndrome (22q11 deletion)
• Management: Surgical repair in early infancy

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5. Total Anomalous Pulmonary Venous Connection (TAPVC)

• Defect: All four pulmonary veins drain into right atrium (or systemic veins) instead of left atrium; ASD (or PFO) is mandatory for survival
• Types: Supracardiac (most common), cardiac, infracardiac, mixed
• Clinical: Depends on obstruction — obstructed type presents with severe cyanosis and pulmonary edema at birth; unobstructed type shows mild cyanosis
• CXR: "Snowman" (figure-of-8) sign in supracardiac type
• Management: Surgical re-routing of pulmonary veins to left atrium (emergency if obstructed)

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6. Ebstein's Anomaly

• Defect: Downward displacement of abnormal tricuspid valve into RV → "atrialized" RV; associated with maternal lithium use
• Clinical: Variable; cyanosis (via ASD R→L), arrhythmias (WPW syndrome common — accessory pathway), S3/S4 gallop, systolic murmur
• ECG: Tall P waves, RBBB, delta waves (WPW); "Himalayan P waves"
• Management: Medical (arrhythmia control) or surgical valve repair/replacement

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Eisenmenger Syndrome

• Chronic high-pressure/volume pulmonary flow → irreversible pulmonary vascular disease → pulmonary hypertension → shunt reversal to R→L → late-onset cyanosis, clubbing, erythrocytosis
• Surgical correction is contraindicated once established (fixed pulmonary hypertension)
• Management: Pulmonary vasodilators (sildenafil, bosentan), heart-lung transplant

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Clinical Approach to CHD in MBBS

Hyperoxia Test (Nitrogen Washout Test)

• PaO2 rises >150 mmHg → Pulmonary cause (normal response)
• PaO2 does NOT rise (remains <100 mmHg) → Cyanotic CHD (R→L shunt)
• Blood turns pink in all causes except methemoglobinemia (remains chocolate-colored)

Key Murmur Summary

Key CXR Signs

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Surgical Procedures Summary

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• Robbins & Kumar Basic Pathology, p. 347–358
• Tintinalli's Emergency Medicine: A Comprehensive Study Guide, p. 861–870
• Bailey & Love's Short Practice of Surgery, p. 986