In truncus, the pulmonary arteries don’t come off on their own. They come off the aorta. In addition, there’s also a large hole in the heart, called a VSD.

Truncus is repaired by dividing the pulmonary artery off the aorta, and connecting it to the right ventricle. Often, an artificial valve of some kind is needed to properly attach the pulmonary artery to the right ventricle. The VSD is also closed to get the circulation back to normal.