🩻 TOACS FCPS Station · Chest X‑ray in d‑TGA
📷 Chest X‑ray (PA view)
🔍 Key radiographic features:
- ✓ 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
📋 Clinical scenario (examiner prompt)
A 12‑hour‑old term neonate presents with central cyanosis and tachypnoea since birth. Oxygen saturation is 72% in room air. Cardiac auscultation reveals a single S2 with no murmur. The chest X‑ray (PA view) shows an egg‑on‑string cardiac silhouette.
🧑⚕️ Examiner tasks · TOACS
1. Identify the diagnosis from the X‑ray and clinical context.
2. Describe the underlying pathology (aorta from RV, PA from LV).
3. Describe the X‑ray findings (egg‑on‑string, narrow mediastinum).
4. Discuss immediate management (PGE1, Rashkind septostomy, arterial switch).
🎯 Expected answers (for examiners)
- • Diagnosis: d‑Transposition of the Great Arteries (d‑TGA)
- • Pathology: Aorta from RV (anterior), PA from LV (posterior) – parallel circulation
- • X‑ray: Egg‑on‑string heart (narrow base, upturned apex), normal size
- • Management: PGE1, Rashkind septostomy, arterial switch (Jatene) within 2 weeks
⚡ Quick FCPS‑style MCQ
The egg‑on‑string appearance on chest X‑ray in d‑TGA is due to:
A. Enlarged right atrium and left ventricle B. Narrow mediastinum with a small thymus and upturned apex C. Dilated pulmonary artery D. Pericardial effusion📌 Topic summary ·
Aorta from RV, PA from LV (parallel circulation)
Egg‑on‑string heart (narrow base, upturned apex)
PGE1 0.05‑0.1 mcg/kg/min
Balloon atrial septostomy for severe hypoxemia
Arterial switch (Jatene) within 2 weeks
Right axis deviation, RVH (normal neonatal pattern)