Truncus arteriosus is a type of heart defect in which a baby is born with one large blood vessel—normally there are two—that receives blood from both the heart’s ventricles. This single blood vessel mixes oxygen-rich blood with oxygen-poor blood. Oxygen-rich blood and oxygen-poor blood normally remain in two separate blood vessels in the heart.

Babies who are born with this defect may die of heart failure unless they have treatment soon after birth. Surgery divides the single large blood vessel into two separate blood vessels so that blood can circulate properly.