Truncus Arteriosus is a rare birth defect that affects the heart. People with this condition have one large blood vessel exiting the heart, instead of two separate vessels. Normally, the heart is separated into four chambers, two lower and two upper. However, people with truncus arteriosus are missing part of the wall that divides the two lower chambers. This results in oxygen-poor and oxygen-rich blood mixing in the lower chambers where they would not normally mix. Symptoms usually develop within the first few weeks of life, and may include: blue coloring of the skin, poor feeding, tiredness, poor growth, shortness of breath or rapid breathing, irregular heartbeats, and excessive sweating. A child should receive urgent care if they exhibit rapid, shallow or labored breathing, worsening of blue coloring, or loss of consciousness. A doctor can diagnose this condition using a heart test or an X-ray. Without treatment, truncus arteriosus can be fatal, but surgery to repair the defects is usually successful.