Normally, the aorta originates from the left ventricle and the pulmonary artery originates from the right ventricle. In the case of truncus arteriosus, the aorta and pulmonary artery are not fully separated, resulting in a single arterial trunk that arises above a VSD. The low-oxygen blood from the right ventricle and the oxygen-rich blood of the left ventricle mix and are pumped to both the lungs and the body. As a result, the lung circulation is exposed to high pressure and increased blood flow.
Corrective surgery must be performed in the first six months of life. Complete repair requires closure of the VSD and separation of the great arteries. The VSD is closed with a patch such that the truncus originates in the left atrium. Next, a connection is made between the branch pulmonary arteries and the right atrium using a valved conduit (tube containing a valve). Any connections between the branch pulmonary arteries and the truncal vessel are also patched closed.
View an animated heart with Truncus Arteriosus