Transposition of the Great Arteries 

Overview  

Transposition of the great arteries (TGA) is a congenital heart defect where the two main arteries responsible for carrying blood from the heart to the lungs and body are reversed. In this condition, the aorta, which should be connected to the left ventricle, is instead connected to the right ventricle, while the pulmonary artery, which should be connected to the right ventricle, is connected to the left ventricle. This abnormality results in oxygen–poor blood being sent to the body instead of the lungs, and oxygen–rich blood returning to the lungs instead of being distributed throughout the body. Without treatment, babies cannot survive with this condition. 

TGA has two types:  

• Dextro–transposition of the great arteries (D–TGA) is a medical condition that leads to a reduced supply of oxygen–rich blood to the body. The symptoms of this condition usually become apparent during pregnancy, shortly after birth, or within a few weeks following birth. If left untreated, D–TGA can give rise to severe complications or potentially result in death. 

• Levo–transposition of the great arteries (L–TGA) is a relatively rare form of transposition. Its symptoms may not manifest immediately, and the treatment approaches vary depending on the specific heart issues linked to this condition. 

One of the common heart defects associated with Transposition of the Great Arteries (TGA) is the presence of a ventricular septal defect (VSD), which refers to an opening in the ventricular septum. The ventricular septum is the wall that separates the two lower chambers of the heart. The presence of a VSD allows for the mixing of oxygen–poor blood and oxygen–rich blood. 

The standard treatment for TGA involves surgical intervention to correct the positioning of the arteries. Typically, this surgery is performed shortly after the baby is born. 

Symptoms  

During a routine pregnancy ultrasound, the condition known as transposition of the great arteries (TGA) can be detected in a baby before birth. However, individuals with the congenitally corrected form of TGA may not exhibit any symptoms for an extended period of time, sometimes spanning many years. 

After birth, symptoms of transposition of the great arteries may manifest as follows: 

• blue skin color (cyanosis) 
• Weak pulse. 
• Poor feeding 
• Poor weight gain. 

When a baby with TGA also has additional heart issues, any changes in skin color may not be immediately apparent due to the presence of other heart problems enabling some oxygen–rich blood flow throughout the body. However, as the baby becomes more active, the blood flow decreases, leading to a more noticeable blue or gray skin color. It is crucial to seek emergency medical assistance if anyone exhibits a blue or gray skin color. 

Causes  

Transposition of the great arteries can happen during pregnancy as the baby’s heart forms. The exact cause is often unknown.In a normal heart, the pulmonary artery, which carries blood from the heart to the lungs, is connected to the right ventricle, the heart’s lower right chamber. From the lungs, oxygen–rich blood is pumped to the left atrium, the upper left chamber of the heart. It then flows into the lower left chamber, known as the left ventricle. Finally, the body’s main artery, the aorta, is connected to the left ventricle, enabling the pumping of oxygenated blood out of the heart and its distribution to the rest of the body. 

Risk factors  

There are several factors that can increase the risk of transposition of the great arteries in a baby. These include: 

• German measles or another viral infection during pregnancy. 
• Consuming alcohol or taking certain medications while pregnant. 
• Smoking during pregnancy.
• Poorly controlled diabetes during pregnancy, also known as gestational diabetes.