Truncus arteriosus pronounced TRUNG-kus ahr-teer-e-O-sus), also known as common truncus, is a rare defect of the heart in which a single common blood vessel comes out of the heart, instead of the usual two vessels (the main pulmonary artery and aorta). What is Truncus Arteriosus. Truncus arteriosus is a birth defect of the heart.
https://www.cdc.gov/ncbddd/heartdefects/truncusarteriosus.html