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[Embryology](https://durgical.com/en/embryology/) · [Heart and vessels](https://durgical.com/en/embryology/#a-heart)

# Persistent truncus arteriosus

- Malformation

A single vessel leaves the heart instead of two, because the wall that separates the aorta from the pulmonary artery never formed.

Updated 2026-11-01

**See it in 3D:** [Ascending aorta](https://durgical.com/en/anatomy/ascending-aorta/) · [Pulmonary trunk](https://durgical.com/en/anatomy/pulmonary-trunk/) · [Pulmonary arteries](https://durgical.com/en/anatomy/right-pulmonary-artery/) · [Interventricular septum](https://durgical.com/en/anatomy/interventricular-septum/) · [Right ventricle](https://durgical.com/en/anatomy/right-ventricle/) · [Left ventricle](https://durgical.com/en/anatomy/left-ventricle/)

## Key points

- Cause: absent aorticopulmonary septum (failure of cardiac neural crest).
- Always with a VSD, because the conal septum also fails to close the interventricular foramen.
- One vessel with a single truncal valve, often leaky.
- Cyanotic (mixing), with pulmonary overcirculation and early heart failure.
- Classic association: 22q11.2 deletion (DiGeorge) syndrome.

## What it is

In persistent truncus arteriosus the truncal and conal ridges fail to fuse, and no aorticopulmonary septum forms. A single vessel with a single valve arises over a VSD and delivers mixed blood to the systemic, coronary and pulmonary circulations. It is cyanotic and strongly linked to 22q11.2 deletion.

## Embryological cause

- Weeks 5–7: the truncal and conal ridges fail to form or fuse.
- With no septum the truncus does not divide and a single vessel remains.
- The absent conal septum cannot close the interventricular foramen: an outlet VSD.
- Explained by poor migration of cardiac neural crest through arches 3, 4 and 6.

## Markers

- TBX1 (22q11.2)
- Cardiac neural crest
- PAX3

## How it presents

- Mild to moderate cyanosis in the first days.
- Fast breathing, sweating and poor weight gain from heart failure as pulmonary resistance falls.
- Bounding pulses; a systolic and sometimes diastolic murmur from truncal valve regurgitation.
- Look for hypocalcemia, infections and the facial features of 22q11.2 deletion.

## Diagnosis

- Prenatal or postnatal echocardiography: a single vessel overriding a VSD.
- Pulse oximetry screening; genetic testing for 22q11.2.
- Serum calcium and T-cell count when DiGeorge is suspected.

## Memory aid

If the neural crest never arrives, the trunk never splits: one pipe for everyone and a hole beneath it.

## Test yourself

Think of the answer, then tap the question to see it.

## What is the embryological cause of persistent truncus arteriosus?

Failure of the truncal and conal ridges to form or fuse: no aorticopulmonary septum forms.

## Which defect always accompanies persistent truncus arteriosus?

A ventricular septal defect, because the missing conal septum cannot close the interventricular foramen.

## Which genetic syndrome is associated with truncus arteriosus?

22q11.2 deletion (DiGeorge) syndrome.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/embryology/persistent-truncus-arteriosus/)

## See it in 3D

The structures of Durgical's 3D anatomy where it is found.

- [Ascending aorta](https://durgical.com/en/anatomy/ascending-aorta/)
- [Pulmonary trunk](https://durgical.com/en/anatomy/pulmonary-trunk/)
- [Pulmonary arteries](https://durgical.com/en/anatomy/right-pulmonary-artery/)
- [Interventricular septum](https://durgical.com/en/anatomy/interventricular-septum/)
- [Right ventricle](https://durgical.com/en/anatomy/right-ventricle/)
- [Left ventricle](https://durgical.com/en/anatomy/left-ventricle/)

## Related

- [Outflow tract: the spiral aorticopulmonary septum and neural crest](https://durgical.com/en/embryology/outflow-tract-the-spiral-aorticopulmonary-septum-and-neural-crest/)
- [Transposition of the great arteries](https://durgical.com/en/embryology/transposition-of-the-great-arteries/)
- [Tetralogy of Fallot](https://durgical.com/en/embryology/tetralogy-of-fallot/)
- [22q11.2 deletion (DiGeorge): the third and fourth pouches](https://durgical.com/en/embryology/22q11-2-deletion-the-third-and-fourth-pouches/)
- [Neural crest cells and their derivatives](https://durgical.com/en/embryology/neural-crest-cells-and-their-derivatives/)
- [Ventricular septal defect](https://durgical.com/en/embryology/ventricular-septal-defect/)

## Related conditions

- [DiGeorge syndrome (22q11.2 deletion syndrome)](https://durgical.com/en/conditions/digeorge-syndrome/)
- [Heart failure](https://durgical.com/en/conditions/heart-failure/)

[← All of embryology](https://durgical.com/en/embryology/)

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); [Truncus Arteriosus | Congenital Heart Defects (CHDs) | CDC](https://www.cdc.gov/heart-defects/about/truncus-arteriosus.html) (Centers for Disease Control and Prevention, 2024).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/embryology/persistent-truncus-arteriosus/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/embryology/persistent-truncus-arteriosus/