✅ Model Answer:
• Boot‑shaped heart (coeur en sabot) – upturned apex due to RVH.
• Concave main pulmonary artery segment (small/absent PA).
• Decreased pulmonary vascularity (oligemic lung fields).
• Right ventricular enlargement (apex elevation).
• Right aortic arch in ~25% (not always visible).
• Diagnosis: Tetralogy of Fallot (TOF).

✅ Model Answer:
• Four components:
1. Ventricular septal defect (VSD) – perimembranous, large.
2. Overriding aorta – aorta dextroposed over VSD.
3. Right ventricular outflow tract obstruction (RVOTO) – pulmonary stenosis (infundibular, valvular, or both).
4. Right ventricular hypertrophy (RVH) – secondary to pressure overload.
• Pathophysiology: RVOTO → RV pressure ↑ → RVH → right-to-left shunt through VSD → cyanosis. Degree of cyanosis depends on severity of RVOTO.

✅ Model Answer:
• Cyanosis (bluish discoloration) – especially during crying, feeding, or exertion.
• Squatting – increases systemic vascular resistance, decreases right-to-left shunt.
• Harsh systolic ejection murmur at LUSB (pulmonary stenosis).
• Single S2 – absent pulmonary component (PS).
• Clubbing – in older children with chronic cyanosis.
• Tet spell: Hypercyanotic episode – acute hypoxemia, deep cyanosis, hyperpnea, irritability, syncope. Triggered by crying, feeding, or fever. Mechanism: decreased SVR → increased right-to-left shunt → worsening cyanosis.

✅ Model Answer:
1. Knee-chest position – increases SVR, decreases right-to-left shunt.
2. 100% oxygen – treat hypoxia.
3. Morphine sulfate (0.1-0.2 mg/kg SQ/IM/IV) – reduces crying and ventilatory drive.
4. IV fluids – volume expansion to improve preload and RV filling.
5. IV propranolol (0.1-0.2 mg/kg) or esmolol – reduces RVOT spasm (decreases heart rate and contractility).
6. Sodium bicarbonate – if severe acidosis (metabolic).
7. Phenylephrine (IV) – vasoconstrictor to increase SVR (if refractory).
8. Emergent surgical repair if spells are refractory.

✅ Model Answer:
• TOF is associated with 22q11.2 deletion syndrome (DiGeorge / velocardiofacial syndrome) in 15-20% of cases.
• Features: Hypocalcemia (parathyroid aplasia), thymic aplasia (T-cell deficiency), cleft palate, conotruncal defects (TOF, truncus arteriosus, interrupted aortic arch), characteristic facies.
• Other associations: Down syndrome (TOF, AV canal), Alagille syndrome (TOF + JAG1 mutation), CHARGE syndrome.
• Screening: FISH for 22q11.2 deletion in all TOF patients.

✅ Model Answer:
• Primary repair: VSD closure + relief of RVOT obstruction. Performed at 3-6 months of age (or earlier if symptomatic).
• Palliative shunt (BT shunt – Blalock-Taussig): Used in neonates with symptomatic cyanosis or small pulmonary arteries. Subclavian artery to pulmonary artery anastomosis.
• Repair approach: Median sternotomy, cardiopulmonary bypass. Transannular patch may be needed if pulmonary valve annulus is small.
• RVOT repair: Infundibular resection, pulmonary valvotomy, or transannular patch.

✅ Model Answer:
• Early: Low cardiac output, bleeding, arrhythmias, complete heart block (1-2%), pericardial effusion, residual VSD.
• Late (long-term):
- Pulmonary regurgitation (PR) – most common – due to transannular patch → RV dilation → RV dysfunction.
- Ventricular tachycardia (VT) – risk of sudden death.
- RV dilation and dysfunction.
- Residual RVOT obstruction.
- Aortic regurgitation – progressive.
- Recurrent VSD (rare).
- Endocarditis prophylaxis required for 6 months post-repair.

✅ Model Answer:
• Pulmonary regurgitation (PR) is the most common late complication.
• Indications for pulmonary valve replacement (PVR):
- Severe PR with symptoms (dyspnea, exercise intolerance).
- RV dilation (RVEDV index >150 mL/m²).
- RV dysfunction (RVEF <45%).
- Progressive RV dilation on serial imaging.
- Sustained arrhythmias (VT).
• Melody valve: Transcatheter pulmonary valve replacement – preferred for older children/adolescents with dysfunctional conduits. Avoids repeat sternotomy. Excellent outcomes.

✅ Model Answer:
• Risk factors for sudden death (VT/VF):
- QRS duration >180 ms (wide QRS).
- RV systolic dysfunction.
- Inducible VT on electrophysiology study (EPS).
- Previous history of sustained VT or syncope.
- Left ventricular dysfunction.
• Management:
- ICD (implantable cardioverter-defibrillator) – indicated for high-risk patients (sustained VT, syncope, LV dysfunction, inducible VT).
- Catheter ablation – for scar-related VT.
- PVR (pulmonary valve replacement) – may reduce VT risk by improving RV hemodynamics.
- Regular follow-up with ECG, Holter, echo, and MRI.

✅ Model Answer:
• Excellent prognosis with modern surgical repair: >95% survival to adulthood.
• Most patients lead active lives with good quality of life.
• Long-term issues: pulmonary regurgitation, RV dysfunction, arrhythmias, aortic regurgitation, residual RVOT obstruction.
• Follow-up: Lifelong cardiology follow-up with annual echo, ECG, and periodic cardiac MRI.
• Activity restrictions: Competitive sports may be restricted based on RV function and arrhythmia risk. Low-to-moderate intensity activities are generally safe.
• Pregnancy: High-risk; requires pre-pregnancy counseling and multidisciplinary care.

✅ Model Answer:
• Key echo findings in TOF:
- Large perimembranous VSD with overriding aorta.
- RVOT obstruction (infundibular, valvular, or both).
- RVH (thickened RV wall).
- Small pulmonary annulus and branch pulmonary arteries.
- Right aortic arch (25%).
- Assess pulmonary valve size (z-score).
- Assess LV function and coronary anatomy (important for surgery).
• Post-repair: Assess for residual VSD, RVOT gradient, pulmonary regurgitation, RV size and function, and LV function.

✅ Model Answer:
• TOF: VSD + overriding aorta + RVOTO + RVH. Boot-shaped heart on CXR. Single S2. Systolic ejection murmur at LUSB.
• Truncus arteriosus: Single arterial trunk from heart, VSD, pulmonary arteries from truncus. Cyanosis + heart failure in infancy. Prominent pulmonary vascularity on CXR (not oligemic).
• Tricuspid atresia: No tricuspid valve, hypoplastic RV, VSD, pulmonary stenosis. ECG shows left axis deviation + LVH.
• Pulmonary atresia with VSD: Similar to TOF but with complete pulmonary atresia (no antegrade flow). PDA-dependent pulmonary blood flow.
• D-TGA: Cyanosis from birth, no murmur initially, "egg-on-string" heart on CXR, separate aorta and PA on echo.