Truncus arteriosus is a rare congenital heart defect in which a single large blood vessel comes out of the heart instead of two separate arteries — the pulmonary artery and the aorta. In a normal heart, these vessels carry oxygen-poor and oxygen-rich blood to different parts of the body. However, in truncus arteriosus, both types of blood mix together and are pumped throughout the body, leading to inadequate oxygen delivery to tissues and organs.

This condition occurs during fetal development when the embryonic truncal vessel fails to divide into two distinct arteries. As a result, babies are born with one shared trunk and a hole between the ventricles known as a ventricular septal defect (VSD). Because the oxygen levels in the blood are lower than normal, infants may present with symptoms such as rapid breathing, bluish skin color (cyanosis), poor feeding, excessive sleepiness, and difficulty gaining weight.

Truncus arteriosus is…