💙 Transposition of the Great Arteries (TGA) is a cyanotic congenital heart defect where: ➡️ The aorta arises from the right ventricle (deoxygenated blood → systemic circulation). ➡️ The pulmonary artery arises from the left ventricle (oxygenated blood → recirculates to lungs). ⛔ Without a natural or created shunt (ASD, VSD, PDA), TGA is incompatible with life because the two circulations run in parallel rather than in series.

📖 About

Accounts for ~5–7% of all congenital heart disease.
Leading cause of cyanotic CHD presenting in the neonatal period.
❗ Cyanosis typically worsens once the ductus arteriosus starts to close (first days of life).

🧬 Aetiology & Pathophysiology

Embryological error: failure of the truncus arteriosus to spiral → great arteries arise from wrong ventricles.
RV → Aorta; LV → Pulmonary artery.
🔀 Survival depends on mixing through ASD, VSD, or PDA.

🩺 Clinical Features

💙 Severe central cyanosis (day 1–2, especially when duct closes).
😮‍💨 Tachypnoea / respiratory distress despite clear lungs.
📉 Hypoxaemia not relieved by 100% oxygen (“hyperoxia test” negative).
🍼 Feeding difficulty, poor weight gain, lethargy.
Less cyanotic if large VSD allows mixing (may present slightly later).
🫀 Usually no murmur unless VSD or PDA present.
👣 Clubbing if untreated long term.

🔎 Investigations

🩻 Chest X-ray: Classic “egg-on-its-side” appearance with narrow mediastinum, pulmonary plethora.
🫀 Echocardiography: Diagnostic gold standard, defines anatomy and shunts.
📉 Pulse oximetry: Persistent low saturations not corrected by oxygen.
🧪 Blood gases: Marked hypoxaemia, metabolic acidosis if severe.

🛠️ Management

Management Option	Description	Comments
💉 Prostaglandin E1 Infusion	Keeps ductus arteriosus open (PDA maintained).	Emergency stabilisation until surgery.
🕳️ Balloon Atrial Septostomy	Creates/enlarges ASD → better atrial mixing.	Life-saving bridge if mixing inadequate.
🔄 Arterial Switch Operation (ASO)	Restores normal ventriculo-arterial connections.	Performed within 2–3 weeks of life. 💯 Gold-standard; long-term outcomes excellent.
↔️ Atrial Switch (Mustard / Senning)	Redirects blood at atrial level.	Historic operation; older survivors need specialist follow-up for arrhythmias/RV failure.
📅 Long-term Follow-up	Lifelong cardiology surveillance.	Risks: coronary issues, arrhythmias, valve dysfunction.

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Transposition of the great arteries (TGA)

📖 About

🧬 Aetiology & Pathophysiology

🩺 Clinical Features

🔎 Investigations

🛠️ Management

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