May also be called: Complete Transposition of the Great Arteries; Transposition of the Great Vessels; Transposition of the Great Arteries Complete transposition (trans-puh-ZIH-shun) of the great vessels is a heart defect where the aorta and the pulmonary artery (called the "great vessels" or "great arteries") are reversed, causing the heart to work incorrectly and preventing blood from getting oxygen. More to Know The human heart has four chambers: the right atrium, left atrium, right ventricle, and left ventricle. In a healthy heart, oxygen-poor blood from the body enters the heart through the right atrium. Blood then flows to the right ventricle and is pumped to the lungs through the pulmonary artery to pick up oxygen. The oxygen-rich blood then comes back to the heart through the left atrium. The blood flows to the left ventricle and takes the oxygen to the body through the aorta. When someone has a complete transposition of the great vessels, the pulmonary artery and the aorta are switched so that the aorta is on the right side of the heart and receives oxygen-poor blood, which is sent right back out to the body without getting more oxygen. The pulmonary artery is on the left side of the heart, receives oxygen-rich blood, and sends it back to the lungs again. So, oxygen-rich blood cannot get to the body. Babies with complete transpositions of the great vessels often appear very blue and have low oxygen levels in the bloodstream. They may have trouble feeding and problems breathing. Without treatment, transposition can be life threatening. Keep in Mind Treatment for complete transposition of the great vessels usually involves a surgical procedure called an arterial switch, where the aorta is attached to the left ventricle and the pulmonary artery is attached to the right ventricle. Although those who have had complete transposition of the great vessels need lifelong follow-up with a cardiologist, arterial switch allows most to go on to lead normal, healthy lives. All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts. Back to Articles Related Articles The Heart Your heart beats and sends oxygen throughout your entire body. Find out how it works and how heart problems can be fixed. Read More Your Heart & Circulatory System Your heart is a hard-working muscle. Find out more in this article for kids. Read More Coarctation of the Aorta When someone has coarctation of the aorta, that person's aorta (the major blood vessel that carries blood away from the heart to the body) is narrowed at some point. Read More Congenital Heart Defects Heart defects happen when there's a problem with a baby's heart development during pregnancy. Most heart defects can be treated during infancy. Read More Coarctation of the Aorta Coarctation of the aorta (COA) is a narrowing of the aorta, the major blood vessel that carries blood away from the heart to the body. Read More Patent Ductus Arteriosus (PDA) The ductus arteriosus is a blood vessel that connects two major arteries before birth and normally closes after a baby is born. If it stays open, the result is a condition called patent ductus arteriosus (PDA). Read More Atrial Septal Defect (ASD) Atrial septal defect (ASD) — also known as a "hole in the heart" — is a type of congenital heart defect. Most ASDs are diagnosed and treated successfully. Read More Ventricular Septal Defect Ventricular septal defect, or VSD, is a heart condition that a few teens can have. Find out what it is, how it happens, and what doctors do to correct it. Read More Ventricular Septal Defect (VSD) Ventricular septal defect (VSD) — also known as a "hole in the heart" — is a congenital heart defect. Most VSDs are diagnosed and treated successfully. Read More Heart and Circulatory System The heart and circulatory system (also called the cardiovascular system) make up the network that delivers blood to the body's tissues. Read More When Your Baby Has a Birth Defect If your child has a birth defect, you don't have to go it alone - many people and resources are available to help you. Read More Heart and Circulatory System The heart and circulatory system are our body's lifeline, delivering blood to the body's tissues. Brush up on your ticker with this body basics article. Read More Heart Health Are you heart smart? Learn about this amazing muscle, including how to care for kids with heart conditions. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.