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APPROACH TO CONGENITAL HEART DISEASE (CHD)

For MD Examinations - 15 Marks

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1. DEFINITION & INCIDENCE

• Robbins & Kumar Basic Pathology, p. 347
• Schwartz's Principles of Surgery, p. 814

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2. ETIOLOGY & RISK FACTORS

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3. CLASSIFICATION

CHD
├── ACYANOTIC (L→R shunt initially, NO early cyanosis)
│   ├── WITH INCREASED PULMONARY BLOOD FLOW (shunts)
│   │   ├── VSD (most common CHD, 42%)
│   │   ├── ASD (10%)
│   │   ├── PDA (7%)
│   │   └── AVSD / AV canal defect (4%)
│   └── WITH NORMAL/DECREASED PULMONARY BLOOD FLOW (obstructive)
│       ├── Pulmonary stenosis (8%)
│       ├── Aortic stenosis (4%)
│       └── Coarctation of aorta (5%)
│
└── CYANOTIC (R→L shunt, EARLY cyanosis)
    ├── WITH INCREASED PULMONARY BLOOD FLOW
    │   ├── TGA - Transposition of Great Arteries (4%)
    │   ├── Truncus arteriosus (1%)
    │   └── TAPVC - Total Anomalous Pulmonary Venous Connection (1%)
    └── WITH DECREASED PULMONARY BLOOD FLOW
        ├── Tetralogy of Fallot (most common CYANOTIC CHD, 5%)
        ├── Tricuspid atresia (1%)
        └── Pulmonary atresia

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4. PATHOPHYSIOLOGY OF SHUNTS

Left-to-Right Shunts (Acyanotic)

• Increased blood flow into pulmonary circulation
• No early cyanosis
• Prolonged exposure leads to pulmonary hypertension and increased pulmonary vascular resistance (PVR)
• Eventually causes shunt reversal (R→L) = Eisenmenger Syndrome - marked by late-onset cyanosis
• Once significant pulmonary hypertension develops, the defect is considered irreversible - this is why early surgical repair is critical

Right-to-Left Shunts (Cyanotic)

• Pulmonary circulation bypassed
• Poorly oxygenated blood enters systemic circulation → cyanosis
• Leads to hypoxemia, polycythemia, clubbing

• Robbins & Kumar Basic Pathology, p. 348

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5. INDIVIDUAL LESIONS - DETAILED APPROACH

A. VENTRICULAR SEPTAL DEFECT (VSD) - Most Common CHD (42%)

1. Perimembranous (paramembranous) - Most common type requiring surgery (~80%) - involves membranous septum
2. AV canal (inlet) - Beneath tricuspid valve, limited by tricuspid annulus
3. Supracristal (outlet) - Within conal septum, limited by pulmonary valve
4. Muscular - Most common overall, surrounded by muscle; "Swiss-cheese" = multiple holes

• Small (restrictive) VSD: little shunting, often self-close
• Large (nonrestrictive) VSD: diameter ≥ aortic annulus, free L→R flow, equalization of RV/LV pressure → pulmonary hypertension → Eisenmenger's

• Pansystolic murmur at lower left sternal border
• Loud murmur = small VSD ("maladie de Roger")
• Large VSD: recurrent chest infections, failure to thrive, tachypnea

• Small: watchful waiting (many close spontaneously by age 2)
• Moderate-Large: surgical patch closure or transcatheter device closure
• Indication: Qp:Qs > 2:1, recurrent infections, failure to thrive
• Contraindication: PVR >12 Wood units (inoperable - Eisenmenger's)

• Schwartz's Principles of Surgery, p. 814

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B. ATRIAL SEPTAL DEFECT (ASD) - 10%

1. Ostium secundum - Most common (75%) - in fossa ovalis region
2. Ostium primum - Near AV valves, associated with cleft mitral valve
3. Sinus venosus - Near SVC/IVC entry; associated with anomalous pulmonary venous drainage
4. Coronary sinus type - Rare

• Often asymptomatic in childhood
• Wide fixed splitting of S2 (hallmark)
• Ejection systolic murmur in pulmonary area (due to increased flow, not ASD itself)
• Mild diastolic rumble at tricuspid area

• Secundum: transcatheter device closure (Amplatzer)
• Primum/sinus venosus: surgical repair
• Timing: elective repair 2-4 years (before school)

• Robbins & Kumar Basic Pathology, p. 348-349

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C. PATENT DUCTUS ARTERIOSUS (PDA) - 7%

• Continuous "machinery murmur" at left infraclavicular area (Gibson's murmur)
• Bounding pulse, wide pulse pressure
• Tachypnea, failure to thrive in large PDA

• Premature neonates: Indomethacin (COX inhibitor, blocks prostaglandins that keep ductus open) or Ibuprofen; Acetaminophen as alternative
• Term infants/children: Transcatheter coil/device occlusion or surgical ligation
• Prostaglandin E1 (PGE1): Used to KEEP ductus OPEN in duct-dependent cyanotic CHD (e.g., TGA, pulmonary atresia) as bridge to surgery

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D. TETRALOGY OF FALLOT (TOF) - Most Common CYANOTIC CHD (5%)

1. Pulmonary stenosis (infundibular - most important; determines severity)
2. Right ventricular hypertrophy
3. Overiding aorta (straddles VSD)
4. VSD (large, perimembranous)

• Cyanosis (from birth or shortly after)
• Hypercyanotic ("tet") spells - sudden worsening cyanosis, irritability, syncope, posturing; precipitated by crying, feeding, fever, exertion
• Squatting posture - increases systemic vascular resistance → reduces R→L shunt (classic in older children)
• Clubbing (with longstanding cyanosis)
• Single S2
• Ejection systolic murmur (due to pulmonary stenosis)
• Boot-shaped heart on CXR ("coeur en sabot") - due to RVH elevating apex + concave pulmonary bay
• Right aortic arch in 25%

1. Knee-chest position (squatting equivalent)
2. Supplemental O2
3. Morphine (reduces infundibular spasm, calms patient)
4. IV fluids (increase preload)
5. Beta-blocker (propranolol) - reduces infundibular spasm
6. Phenylephrine (alpha agonist - increases SVR)
7. Sodium bicarbonate (for acidosis)

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E. TRANSPOSITION OF GREAT ARTERIES (TGA) - 4%

• Aorta arises from RV; pulmonary artery from LV
• Two parallel circuits (not in series) - incompatible with life unless mixing occurs
• Mixing via PFO, ASD, VSD, or PDA
• Most common cyanotic CHD presenting in neonates

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F. COARCTATION OF AORTA - 5%

• Preductal (infantile): Proximal to PDA - associated with PDA, presents with cyanosis of lower body in neonates; rapidly fatal without treatment
• Postductal (adult): Adjacent to ligamentum arteriosum - presents later in life

• Upper limb hypertension + lower limb hypotension/weak pulses (radiofemoral delay)
• Systolic murmur
• Rib notching on CXR (from enlarged intercostal collaterals)
• "Figure 3" sign on CXR (indentation of aorta + dilated post-stenotic segment)
• Associated with bicuspid aortic valve (>50%), berry aneurysms (Circle of Willis)
• Common in Turner syndrome (45,XO)

• Robbins & Kumar Basic Pathology, p. 350-351

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6. DIAGNOSTIC APPROACH

Step 1: History

• Age of presentation, cyanosis (central vs. peripheral)
• Feeding difficulty, failure to thrive, recurrent chest infections
• Maternal history (rubella, diabetes, drugs)
• Family history

Step 2: Clinical Examination

• Cyanosis (central - tongue/mucosa), clubbing, polycythemia
• Growth parameters
• Precordial bulge, apical impulse, heaves/thrills
• Heart sounds: S2 splitting pattern
• Murmur: systolic vs. diastolic vs. continuous; grading; radiation

Step 3: Investigations

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7. MANAGEMENT PRINCIPLES

General Principles

1. Anti-failure treatment before surgery (diuretics, digoxin, ACE inhibitors)
2. Endocarditis prophylaxis (for unrepaired and recently repaired defects)
3. PGE1 to maintain ductal patency in duct-dependent lesions
4. Indomethacin to close PDA in premature neonates
5. Timing of surgery based on physiology, not just anatomy

Surgical Options

• Open-heart surgery with cardiopulmonary bypass (CPB)
• Palliative (e.g., BT shunt for TOF, pulmonary artery banding for VSD)
• Corrective/Definitive repair
• Catheter-based interventions (device closure of ASD/VSD/PDA, balloon valvuloplasty, stenting)
• Heart transplantation for complex unrepairable lesions (hypoplastic left heart syndrome)

Eisenmenger Syndrome

• End-stage complication of large L→R shunts
• Irreversible pulmonary hypertension with R→L shunt reversal
• Late cyanosis, erythrocytosis, clubbing
• Surgical repair is contraindicated
• Management: Pulmonary vasodilators (bosentan, sildenafil), supportive care, transplantation

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8. COMPLICATIONS

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9. PROGNOSIS & OUTCOMES

• With advances in surgery, >85% of children with CHD survive to adulthood
• 1.5 million individuals currently living with CHD in the USA
• 25% require surgical intervention in the first year of life
• Operative mortality for most repairs: <2-4% in experienced centers
• Long-term follow-up is essential for arrhythmias, residual lesions, and re-interventions

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SUMMARY TABLE - Quick Exam Reference

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