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Truncus arteriosus is a rare cyanotic congenital heart defect in which a single arterial trunk arises from the heart, giving rise to the aorta, pulmonary arteries, and coronary arteries. It is associated with a large ventricular septal defect (VSD) and results in complete mixing of systemic and pulmonary blood.

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https://www.youtube.com/watch?v=sa3yO42v_bQ

![The two Great Arteries (Aorta and Pulmonary Artery) have a single origin from the heart and blood from both ventricles passes across a VSD into the single arterial trunk. The lung circulation is exposed to very high pressure and increased blood flow (as with a large VSD). Heart failure often develops in the early weeks of life.

Cardiology : Truncus Arteriosus. Rch.org.au. Published 2025. Accessed July 11, 2025. https://www.rch.org.au/cardiology/heart_defects/truncus_arteriosus/ ‌](attachment:dde806dd-7097-42ec-b029-0d0a373eaa0e:20a_Truncus_arteriosus.jpg)

The two Great Arteries (Aorta and Pulmonary Artery) have a single origin from the heart and blood from both ventricles passes across a VSD into the single arterial trunk. The lung circulation is exposed to very high pressure and increased blood flow (as with a large VSD). Heart failure often develops in the early weeks of life.

Cardiology : Truncus Arteriosus. Rch.org.au. Published 2025. Accessed July 11, 2025. https://www.rch.org.au/cardiology/heart_defects/truncus_arteriosus/ ‌

Embryological Basis

Failure of conotruncal (aorticopulmonary) septation during fetal development prevents the normal division of the truncus arteriosus into the aorta and pulmonary artery.
It is commonly associated with DiGeorge syndrome (22q11.2 deletion).

Hemodynamics

Complete mixing of oxygenated and deoxygenated blood → systemic desaturation (cyanosis)
High pulmonary blood flow → congestive heart failure
Risk of pulmonary vascular disease if not corrected early

Classification

![(A–D) Collett-Edwards type 1–4 classifications. (D) Type 4 is now considered pulmonary atresia with a ventricular septal defect. (E–H) Van Praagh modifications of the Collett-Edwards classifications. (A–C) Collett-Edwards types 1–3 and (E and F) Van Praagh types A1 and A2 are similar, differing only in the number and location of the pulmonary arteries originating from the truncus. (G) Van Praagh type A3 has a single pulmonary artery arising from the truncus and the second pulmonary artery from the descending aorta. (H) In Van Praagh type A4, a hypoplastic aortic arch and a patent ductus arteriosus arise from the truncus arteriosus. Pulmonary arteries originate from the posterior aspect of the truncus arteriosus

Rapp CL, Drose JA: Persistent truncus arteriosus, in Drose JA (ed): Fetal Echocardiography. 2nd ed. St. Louis, MO, Saunders, 2010, pp 223–233. Fyock DG, Downs E. The Use of Sonography in a Mother and Fetus With Concordant Truncus Arteriosus. Journal of Diagnostic Medical Sonography. 2019;36(2):174-180. doi:10.1177/8756479319891073](attachment:87a947ab-cf6e-480c-b342-ce2fe3c5019d:10.1177_8756479319891073-fig6.jpg)

(A–D) Collett-Edwards type 1–4 classifications. (D) Type 4 is now considered pulmonary atresia with a ventricular septal defect. (E–H) Van Praagh modifications of the Collett-Edwards classifications. (A–C) Collett-Edwards types 1–3 and (E and F) Van Praagh types A1 and A2 are similar, differing only in the number and location of the pulmonary arteries originating from the truncus. (G) Van Praagh type A3 has a single pulmonary artery arising from the truncus and the second pulmonary artery from the descending aorta. (H) In Van Praagh type A4, a hypoplastic aortic arch and a patent ductus arteriosus arise from the truncus arteriosus. Pulmonary arteries originate from the posterior aspect of the truncus arteriosus

Collett and Edwards classification system:

Earliest form of classification, developed in 1949. It is based on where pulmonary arteries arise from the common trunk.

Type	Description
Type I	Main pulmonary is present and bifurcates into the left and right pulmonary arteries
Type II	Right & left branches arise adjacent to each other from the posterolateral segment of the common trunk
Type III	Right & left branches originate separately from the lateral segments of the common trunk
Type IV	Neither of the branches arise from the common trunk, but are perfused by aortopulmonary collaterals. This type is now categorized as a form of pulmonary atresia with a ventricular septal defect rather than TA

Van Praagh classification system:

Based on where the branch pulmonary arteries arise from the trunk as well as the development of the aortic arch and the presence of a patent ductus arteriosus (PDA). Each type may include a modifier “A” (with VSD) of “B” (intact ventricular septum).