AKT · Child health/Congenital heart

Transposition of the great arteries (TGA)

Cyanotic CHD: aorta arises from the RV and pulmonary artery from the LV (parallel circulations)

Overview

A cyanotic lesion where the aorta arises from the right ventricle and the pulmonary artery from the left — two parallel circulations. Deoxygenated blood recirculates to the body; survival depends on MIXING (PDA/PFO/VSD). Presents with profound CYANOSIS in the FIRST DAY OR TWO of life. 'EGG-ON-A-STRING' heart on CXR. Emergency: PROSTAGLANDIN to keep the duct open, often balloon atrial septostomy, then arterial switch surgery.

Recognise

Profound CYANOSIS within the FIRST 1-2 DAYS of life, not responding to oxygen; often otherwise well-looking baby
Single loud S2; murmur may be absent (unless VSD); CXR: 'EGG-ON-A-STRING' (narrow mediastinum) with a globular heart
Survival depends on mixing (duct/atrial septum); duct-dependent

Red flags

Profound day-1 cyanosis → emergency: PROSTAGLANDIN (keep the duct open) ± balloon atrial septostomy
Failure to mix → severe hypoxia/acidosis

Differentials & how to tell them apart

Tetralogy of Fallotcyanosis often LATER, tet spells, boot-shaped heart; TGA is day-1-2 cyanosis, egg-on-string

Other duct-dependent cyanotic lesionstricuspid atresia, TAPVR, truncus — echo defines; all may need prostaglandin

Persistent pulmonary hypertension / respiratory cause of cyanosishyperoxia test + echo differentiate cardiac from non-cardiac cyanosis

Investigations

Pre/post-ductal saturations + hyperoxia test (cyanosis unresponsive to O2); echocardiography (the discordant connections, mixing); CXR (egg-on-a-string).

Management

Emergency prostaglandin (keep duct open) ± balloon atrial septostomy → arterial switch

1Profound day-1-2 cyanosis unresponsive to oxygen → start PROSTAGLANDIN immediately to maintain ductal mixing; urgent echo; balloon atrial septostomy improves mixing. Plan arterial switch.Gate: TGA is DUCT-DEPENDENT for mixing — prostaglandin to KEEP the duct open is life-saving (giving oxygen alone will not correct the cyanosis); the early timing (day 1-2) and egg-on-string CXR distinguish it from Fallot
2Balloon atrial septostomy as a bridge; arterial switch operation (definitive); lifelong cardiology follow-up.

PROSTAGLANDIN (alprostadil) — keep the duct OPEN — maintains mixing/oxygenation as an emergency

Balloon atrial septostomy (Rashkind) — improves atrial mixing

Arterial switch operation — definitive surgery in the first weeks

Key points

Profound cyanosis on DAY 1-2 + egg-on-a-string CXR + unresponsive to oxygen = TGA → prostaglandin (keep duct open) + septostomy + arterial switch. Earliest/most profound cyanosis of the cyanotic lesions.

Monitor & prognosis

Saturations, mixing, surgical outcome.

Excellent after arterial switch; fatal untreated.

Source: RCPCH; paediatric cardiology