✅ Model Answer:
• Egg-on-string cardiac silhouette (narrow base, upturned apex).
• Narrow superior mediastinum (small thymus).
• Normal heart size (initially).
• Increased pulmonary vascularity (if high pulmonary flow).
• No specific chamber enlargement pattern.
• Diagnosis: d-Transposition of the Great Arteries (d-TGA).

✅ Model Answer:
• d-TGA: Aorta arises from the morphological RV (anterior, rightward), and pulmonary artery arises from the LV (posterior).
• Parallel circulation: Deoxygenated systemic venous blood returns to the RA → RV → aorta → systemic circulation (bypassing lungs). Oxygenated pulmonary venous blood returns to the LA → LV → pulmonary artery → lungs (bypassing systemic circulation).
• Survival requires mixing between the two circuits (ASD, VSD, or PDA).
• Without mixing, severe cyanosis and death occur.

✅ Model Answer:
• Severe central cyanosis – within hours to days of birth (SpO2 60-80%).
• Tachypnoea and respiratory distress.
• Single S2 (aortic valve closure dominates – anterior aorta).
• No murmur initially (or soft systolic ejection murmur if VSD/PDA present).
• Shock and acidosis if mixing is inadequate.
• The degree of cyanosis depends on the size of the ASD/VSD/PDA.

✅ Model Answer:
1. PGE1 (Prostaglandin E1) – 0.05-0.1 mcg/kg/min IV to maintain ductal patency and improve pulmonary blood flow / mixing.
2. Respiratory support – oxygen, ventilation (may worsen cyanosis if high FiO2 is given alone).
3. Correct acidosis and electrolytes.
4. Urgent echocardiogram to confirm diagnosis and assess mixing.
5. Balloon atrial septostomy (Rashkind procedure) – if severe hypoxemia despite PGE1 or if mixing is inadequate.
6. Urgent surgical referral for arterial switch operation (Jatene) within 2 weeks of life.

✅ Model Answer:
• Rashkind procedure (balloon atrial septostomy): A balloon-tipped catheter is passed across the PFO/ASD into the LA, inflated, and pulled back to tear the atrial septum.
• Indications:
- Severe hypoxemia (SpO2 <75%) despite PGE1 infusion.
- Inadequate atrial-level mixing.
- As a bridge to definitive surgery (arterial switch).
• Performed in the cardiac catheterization lab or at the bedside under echo guidance.
• Allows improved mixing of oxygenated and deoxygenated blood at the atrial level.

✅ Model Answer:
• Arterial switch operation (Jatene procedure) – definitive repair.
• Procedure: The aorta and pulmonary artery are transected and switched (aorta connected to LV, PA to RV). The coronary arteries are reimplanted to the neo-aorta.
• Optimal timing: Within the first 2 weeks of life (before LV muscle regresses).
• If LV pressure drops, the LV may not be able to support systemic circulation (LV "deconditioning").
• After 4-6 weeks, a two-stage repair may be needed (pulmonary artery banding first to "retrain" the LV).

✅ Model Answer:
• Right axis deviation (normal for neonate).
• Right ventricular hypertrophy (RVH) – tall R waves in V1-V2 (normal neonatal pattern, but may be exaggerated).
• Right atrial enlargement – tall P waves.
• May be normal in the first few days of life.
• In older infants with unrepaired d-TGA, RVH and right axis deviation persist.

✅ Model Answer:
• Ventricular septal defect (VSD) – in ~40% of cases.
• Pulmonary stenosis (or subpulmonary stenosis) – in ~5-10% (especially if VSD is present).
• Patent ductus arteriosus (PDA) – in ~20%.
• ASD/PFO – present in most (required for survival).
• Coarctation of aorta – uncommon.
• Coronary artery anomalies – important for surgical repair (various patterns).

✅ Model Answer:
• Supravalvular pulmonary stenosis – due to the Lecompte maneuver (most common).
• Aortic root dilatation and aortic regurgitation.
• Coronary artery stenosis – at the reimplantation site.
• Arrhythmias – atrial flutter/fibrillation, ventricular arrhythmias.
• Left ventricular dysfunction – late.
• Sudden death – rare, can be due to coronary ischemia.
• Long-term outcomes are excellent (>95% survival at 20 years).

✅ Model Answer:
• d-TGA with intact ventricular septum (IVS): Most common. Cyanosis is severe from birth. Requires PGE1 and Rashkind septostomy. Arterial switch within 2 weeks.
• d-TGA with VSD: Cyanosis may be less severe (more mixing). Heart failure may develop (due to increased pulmonary blood flow). Pulmonary hypertension may develop early. Repair (arterial switch + VSD closure) may be delayed to 2-3 months if the infant is stable.
• If pulmonary stenosis is present (TGA + VSD + PS), it is called "TOF physiology" and may require a different surgical approach (Rastelli procedure).

✅ Model Answer:
• Rastelli procedure: Used for TGA with VSD and pulmonary stenosis (or subpulmonary stenosis).
• Procedure: An intraventricular baffle is created to direct LV blood through the VSD to the aorta. A conduit is placed from the RV to the pulmonary artery (RV-PA conduit).
• Indications: When arterial switch is not feasible (e.g., TGA + VSD + severe PS).
• Long-term complications: RV-PA conduit stenosis, need for conduit replacement.

✅ Model Answer:
• Urgent echocardiogram to assess atrial septal defect size and mixing.
• Rashkind balloon atrial septostomy – to enlarge the ASD and improve mixing.
• If SpO2 remains low despite septostomy, consider:
- Adjusting PGE1 dose.
- Surgical atrial septostomy (Blalock-Hanlon) – rarely performed now.
- Urgent arterial switch operation.