Tetralogy of Fallot 💔

💔 Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart defect (~10%). Babies may appear "pink" at birth but develop cyanosis as RV outflow obstruction worsens in the first months of life. Classic presentation includes cyanosis, murmurs, and Tet spells.

📖 About

• Most common cause of congenital cyanotic heart disease.
• Progressive RVOT obstruction → cyanosis usually between 6–9 months.
• "Tet spells" triggered by adrenergic stress (crying, feeding).
• Immediate cyanosis at birth suggests other defects (e.g., transposition).

🧩 The 4 Classic Defects

• 🔄 Overriding Aorta - aorta sits above the VSD → mixing blood.
• 💪 Right Ventricular Hypertrophy (RVH) - due to RVOT obstruction.
• 🚧 Sub-pulmonary stenosis - obstruction at/near pulmonary valve.
• 🕳️ Large VSD - usually unrestrictive, allows RV→LV shunt.

📊 Diagram

🔬 Pathophysiology

• Reduced pulmonary flow → systemic desaturation.
• Initially left→right shunt, later RV pressure ↑ → reversal (right→left shunt).
• Right-to-left shunt + hypoxia = cyanosis + clubbing.
• Similar shunting physiology seen in Eisenmenger syndrome.

🩺 Clinical Features

• 😴 Fatigue with feeding/exercise.
• 🔵 Cyanosis (progressive, not always at birth).
• 🎧 Harsh ejection systolic murmur at LSB (RVOT turbulence).
• ❌ Soft/absent P2 (↓ pulmonary flow).
• 🚨 Tet Spells: Sudden severe cyanosis, irritability, LOC risk.
• 🖐️ Clubbing in older children due to chronic hypoxia.

📷 Imaging & Tests

• 📸 CXR: "Boot-shaped" heart (coeur en sabot) + ↓ lung markings.
• 📉 ECG: RVH + right axis deviation.
• 🩻 Echocardiogram: Defines anatomy & severity → key test.
• 🧲 MRI/CT: Useful for surgical planning.

🩹 Management

• Acute Newborn Care: - 💉 Prostaglandin E1 infusion → keep ductus arteriosus open for pulmonary flow.
• 🚨 Tet Spell Management: - Knee-chest position (↑ SVR, ↓ R→L shunt). - 100% O₂ mask. - IV morphine (sedation, ↓ catecholamine drive). - Beta-blocker (propranolol) to slow HR & improve filling.
• Surgery: - 🥇 Complete Repair (<1 yr): VSD patch + relieve RVOT obstruction. - 🪢 Blalock–Taussig Shunt (palliative, ↑ pulmonary flow if small infant/unstable).
• Post-Surgical: - Good prognosis but requires lifelong follow-up. - Watch for arrhythmias, RV dysfunction, residual stenosis/regurgitation.

⚠️ Exam Red Flag: "Boot-shaped heart" on CXR + child squats during cyanotic spell = classic TOF presentation.

📚 References

• AHA – Tetralogy of Fallot
• ACC Review

🩺 Case 1 - Infant with Cyanotic Spells

A 6-month-old boy is brought to the emergency department with episodes of sudden cyanosis and breathlessness when crying, relieved by squatting. On exam: harsh ejection systolic murmur at the left upper sternal edge, central cyanosis, clubbing. Management: 🚑 During "tet spells" place in knee–chest position, give oxygen, morphine, and beta-blocker (propranolol). Definitive treatment is surgical repair (intracardiac repair within first year of life). Avoid: ❌ Delaying surgery in symptomatic infants; avoid dehydration (can worsen right-to-left shunt).

🩺 Case 2 - Child with Growth Delay

A 5-year-old girl with known congenital heart disease presents with poor growth, exercise intolerance, and clubbing. She has a loud systolic murmur and cyanosis on exertion. Echocardiography confirms TOF with right ventricular outflow obstruction and VSD. Management: 🩺 Supportive care, nutritional support, monitor for polycythaemia, and plan for complete surgical repair if not already done. Long-term cardiology follow-up is essential. Avoid: ❌ Neglecting infective endocarditis prophylaxis advice for dental procedures; avoid unnecessary delays to corrective surgery.

🩺 Case 3 - Adult with Repaired TOF

A 28-year-old man had surgical correction of TOF in childhood. He now presents with palpitations and reduced exercise tolerance. ECG shows right bundle branch block, echo reveals pulmonary regurgitation with right ventricular dilatation. Management: 💊 Lifelong follow-up with adult congenital cardiology; pulmonary valve replacement may be required. Screen for arrhythmias and sudden cardiac death risk. Avoid: ❌ Loss to follow-up - repaired TOF patients remain at risk of arrhythmias, right heart failure, and residual lesions.