A cyanotic neonate on the first day of life has severe hypoxia (PaO2 25 mmHg) unresponsive to 100% oxygen (hyperoxia test negative) and a chest X-ray showing an 'egg on a string' (egg on its side) cardiac silhouette with narrow superior mediastinum. What is the underlying anatomical defect?
- A Truncus arteriosus — single great vessel from both ventricles
- B Total anomalous pulmonary venous return — pulmonary veins drain to right atrium
- C Tricuspid atresia — absence of tricuspid valve with obligatory ASD
- D Transposition of the great arteries — aorta arises from the right ventricle anterior to the pulmonary artery ✓
Explanation
The 'egg on a string' (or 'egg on a side') radiographic appearance in a cyanotic neonate with a narrow pedicle and parallel great arteries is classic for D-transposition of the great arteries (D-TGA). In D-TGA, the aorta arises from the morphological right ventricle (anteriorly) and the pulmonary artery from the left ventricle, creating parallel (rather than crossing) circulations with no mixing except through a PDA or ASD. The narrow mediastinum results from the AP alignment of the great vessels. Immediate management requires prostaglandin E1 and balloon atrial septostomy (Rashkind procedure). Arterial switch operation (Jatene) is performed within the first 2 weeks.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.