Embryology · Heart and vessels
Transposition of the great arteries !
- Malformation
The aorta arises from the right ventricle and the pulmonary trunk from the left: oxygen-poor blood goes back to the body and the baby is born very blue.
Updated 2026-11-01
See it in 3D: Ascending aorta · Pulmonary trunk · Right ventricle · Left ventricle · Interatrial septum · Ligamentum arteriosum
What it is
In transposition of the great arteries (d-TGA) the aorticopulmonary septum grows straight instead of spiraling, so the aorta connects to the right ventricle and the pulmonary trunk to the left. The two circulations run in parallel, and survival depends on mixing through the foramen ovale, the ductus arteriosus or a VSD. It is the most common cyanotic heart defect in newborns.
Embryological cause
- Weeks 5–7: the truncal and conal ridges grow straight, without the normal 180-degree twist.
- The straight septum connects the anterior aorta to the right ventricle and the posterior pulmonary trunk to the left.
- Associated with abnormal migration or function of cardiac neural crest and the second heart field.
- The rest of the heart (atria, ventricles, AV valves) is usually well formed.
Markers
- Cardiac neural crest
- Maternal diabetes
How it presents
- Intense cyanosis in the first hours that does not improve with oxygen.
- There may be no murmur if the ventricular septum is intact.
- If the ductus closes, hypoxemia and acidosis worsen quickly.
- With a large VSD cyanosis is milder but early heart failure appears.
Diagnosis
- Prenatal echocardiography: the great arteries leave in parallel instead of crossing.
- Newborn pulse oximetry.
- Chest X-ray: 'egg on a string' from the narrow upper mediastinum.
Test yourself
Think of the answer, then tap the question to see it.
What is the embryological cause of transposition of the great arteries?
The aorticopulmonary septum grows straight instead of spiraling, so the aorta connects to the right ventricle.
Why does a newborn with transposition depend on the ductus arteriosus?
The circulations are in parallel, and the ductus (with the foramen ovale) lets oxygenated blood mix.
Which maternal factor is associated with transposition?
Poorly controlled maternal diabetes.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Outflow tract: the spiral aorticopulmonary septum and neural crest
- Tetralogy of Fallot
- Persistent truncus arteriosus
- Patent ductus arteriosus
- Atrial septal defect and patent foramen ovale
- Maternal diabetes and obesity as teratogens
Related conditions
Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.
Sources: Langman's Medical Embryology, 13th ed., ch. 13: Cardiovascular System (Wolters Kluwer, 2015); Dextro-Transposition of the Great Arteries (d-TGA) | Congenital Heart Defects (CHDs) | CDC (Centers for Disease Control and Prevention, 2024).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.