Figure 6b. Interruption of the left pulmonary artery in a 36-year-old man who was born with a persistent truncus arteriosus (surgically repaired in childhood). (a) Axial CT angiogram obtained at the level of the carina shows interruption of the left main pulmonary artery. The left lung is mildly hypoplastic with decreased vascularity. Note the calcified conduit (*) that connects the right ventricle to the main pulmonary artery and an aneurysmal ascending aorta (AO). (b) Coronal multiplanar reformatted image shows peripheral linear areas of increased attenuation in the left lung (arrows). This finding, which was confirmed at angiography, represents collateral vessels that invade the lung through the pleura. Inset demonstrates the plane of reformation.