Malposition of pulmonary arteries (crossed pulmonary arteries) in persistent truncus arteriosus.

Among 13 specimens with persistent truncus arteriosus, there were 3 cases with malposition of the pulmonary arteries. In 2 specimens, the ostium of the left pulmonary artery lay to the right of and above that of the right pulmonary artery. The 2 pulmonary arteries crossed each other as they proceeded to their respective lungs: "crossed pulmonary arteries." The third specimen presented anomalously positioned ostia of the pulmonary arteries but without crossing. This condition is considered to be a lesser form of classical "crossed pulmonary arteries." Each of these cases also exhibited interruption or atresia of the aortic arch.