Truncus arteriosus

Truncus arteriosus is an uncommon congenital cardiac abnormality that occurs due to the failure of conotruncal septation during development of the fetus. It is characterized by a single arterial trunk that originates from the heart and supplies the systemic, pulmonary, and coronary circulation¹.

The original and more popular classification of truncus arteriosus was devised by Collett and Edwards in 1949, which divides this anomaly into four types²:

• Typetype I: Common pulmonary artery arising from truncus – 80%
• Typetype II: Right and left pulmonary artery arise separately from the posterior part of truncus
• Typetype III: Separate origins of the pulmonary arteries from the lateral aspect of the truncus
• Typetype IV: Neither pulmonary arterial branch arising from the common trunk (pseudotruncus), is now recognized to be a form of pulmonary atresia with VSD rather than truncus arteriosus.

In 1965, Van Praagh modified the classification system which also includes four primary types³:

• Typetype A1: Identical to the Type I of Collett and Edwards
• Typetype A2: Separate origins of the branch pulmonary arteries from the left and right lateral aspects of the common trunk
• Typetype A3: Origin of one branch pulmonary artery (usually the right) from the common trunk, with other lung supplied either by collaterals or a pulmonary artery arising from the aortic arch
• Typetype A4: Coexistence of an interrupted aortic arch.