✅ Model Answer:
• ECG findings: Left axis deviation (superior QRS axis) – the hallmark feature (axis between -30° and -90°).
• Left ventricular hypertrophy (LVH) – tall R waves in V5-V6.
• Right atrial enlargement – tall, peaked P waves.
• Pathognomonic feature: Left axis deviation (superior QRS axis) in a cyanotic neonate is highly suggestive of tricuspid atresia.
• If ECG shows normal or right axis deviation → consider Type II (TGA).

✅ Model Answer:
• Absent tricuspid valve – no connection between RA and RV.
• Hypoplastic right ventricle – small and underdeveloped.
• Atrial septal defect (ASD) – required for mixing of systemic and pulmonary venous return.
• Ventricular septal defect (VSD) – size determines pulmonary blood flow.
• Left ventricle – is the systemic ventricle.
• Great arteries: Normally related (Type I, 70%) or transposed (Type II, 30%).
• Pulmonary flow depends on VSD size and presence of pulmonary stenosis.

✅ Model Answer:
• In tricuspid atresia with pulmonary stenosis or atresia, pulmonary blood flow depends on the patent ductus arteriosus (PDA).
• Acute management:
1. PGE1 (Prostaglandin E1) – 0.05-0.1 mcg/kg/min IV to maintain ductal patency.
2. Correct acidosis, hypoglycemia, and hypocalcemia.
3. Echocardiogram – to confirm anatomy.
4. BT shunt – performed in neonatal period to provide reliable pulmonary flow.

✅ Model Answer:
• Stage 1 (Neonate): BT shunt – systemic-to-pulmonary artery shunt for decreased flow. OR PA banding for increased flow.
• Stage 2 (4-6 months): Bidirectional Glenn shunt – SVC anastomosed to right PA. BT shunt taken down.
• Stage 3 (2-3 years): Fontan procedure – IVC connected to PA (total cavopulmonary connection – TCPC).
• Purpose: Staged approach allows the single ventricle (LV) to adapt to volume load and achieves separation of pulmonary and systemic circulations.

✅ Model Answer:
• Type I (70%): Normally related great arteries.
  - Type Ia: No PS (increased flow).
  - Type Ib: Mild PS (variable flow).
  - Type Ic: Severe PS or PA (decreased flow, ductal-dependent).
• Type II (30%): Transposition of great arteries.
  - Type IIa: No PS (increased flow).
  - Type IIb: PS (decreased flow).
• Type III (rare): Other anomalies.

✅ Model Answer:
• BT shunt: Systemic-to-pulmonary artery shunt (subclavian artery to PA) to provide pulmonary blood flow.
• Modified BT: Gore-Tex graft from subclavian/innominate artery to PA – preferred.
• Complications: Shunt thrombosis, occlusion, PA distortion, heart failure (if too large), paradoxical embolism, chylothorax.
• Prophylaxis: Aspirin for antiplatelet effect.

✅ Model Answer:
• Bidirectional Glenn shunt: SVC anastomosed end-to-side to right PA – passive pulmonary flow from upper body.
• Timing: 4-6 months of age.
• Purpose: Reduces volume load on single ventricle, improves oxygenation (sats 75-85%), removes BT shunt.
• Prerequisites: Normal PA pressure, good ventricular function, no significant AV valve regurgitation.

✅ Model Answer:
• Fontan procedure: Cavopulmonary connection – IVC connected to PA (lateral tunnel or extracardiac conduit). Completes TCPC.
• Timing: 2-3 years of age.
• Fontan criteria: Normal PA pressure (<15 mmHg), normal EF (>50%), no/mild AV valve regurgitation, normal PVR (<2 Wood units), normal sinus rhythm.
• Purpose: Complete separation of pulmonary and systemic circulations.

✅ Model Answer:
• Diagnosis: Protein-losing enteropathy (PLE) – loss of protein into the gut due to elevated CVP.
• Management: Diuretics, albumin infusion, heparin/LMWH, corticosteroids, Fontan revision (fenestration), heart transplantation for refractory cases.

✅ Model Answer:
• Risk factors: Stagnant flow (passive pulmonary flow), prothrombotic state, Fontan conduit thrombosis.
• Prophylaxis: Warfarin (INR 2-3) or LMWH for high-risk (fenestrated Fontan, prior thromboembolism). Aspirin for lower-risk patients.
• Surveillance: Regular echocardiograms and MRI for thrombus detection.