A 6-hour-old neonate is deeply cyanotic with no respiratory distress. SpO2 is 55% in room air. CXR shows an 'egg-on-side' cardiac silhouette with narrow superior mediastinum and increased pulmonary vascularity. Prostaglandin E1 is started. The underlying anatomical anomaly responsible for parallel circulations in this defect is:
- A Pulmonary artery arising from the left ventricle
- B Aorta arising from the right ventricle with pulmonary artery from the left ventricle ✓
- C Single ventricle supplying both great arteries
- D Pulmonary venous return directed to the right atrium
Correct answer: B. Aorta arising from the right ventricle with pulmonary artery from the left ventricle
Explanation
Complete transposition of the great arteries (D-TGA) has the aorta arising from the morphological right ventricle and the pulmonary artery from the morphological left ventricle, creating two parallel circuits rather than the normal series circulation. Oxygenated blood recirculates in the pulmonary circuit and deoxygenated blood recirculates systemically, making survival dependent on mixing via PFO, PDA, or VSD. PGE1 maintains ductal patency to improve mixing until balloon atrial septostomy or surgical correction.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.