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 circulation 1.
The original and more popular classification of truncus arteriosus was devised by Collett and Edwards in 1949, which divides this anomaly into four types 2:
- type I: common pulmonary artery arising from truncus – 80%
- type II: right and left pulmonary arteries arise separately from the posterior part of truncus
- type III: separate origins of the pulmonary arteries from the lateral aspect of the truncus
- type 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 types 3:
- type A1: identical to the Type I of Collett and Edwards
- type A2: separate origins of the branch pulmonary arteries from the left and right lateral aspects of the common trunk
- type 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
- type A4: coexistence of an interrupted aortic arch