Transposition of the great vessels (TGV)
Transposition of the great vessels (TGV) is a form of congenital heart disease, in which the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle, with an associated intracardiac shunt.
In normal individuals, oxygen-depleted blood from the right ventricle goes through the pulmonary artery to the lung to get oxygenated. The oxygen-rich blood goes to the left ventricle, from which it gets ejected to the aorta to the rest of the body. In individuals with TGV, the oxygen-depleted blood from the right ventricle goes directly to the aorta to supply the rest of the body. This is not compatible with life, since the body would never get oxygen-rich blood.
As a safety mechanism, an intracardiac shunt (ie: an atrial septal defect) opens, and this allows the oxygen-rich blood that returns from the lungs to partially mix with the blood in the right ventricle, allowing oxygen to be delivered to the organs of the body. While the body does receive oxygen due to the intracardiac shunting, these individuals invariably have cyanosis.
In this congenital heart defect, the aorta (the main artery that carries blood to the body) originates from the right ventricle and the pulmonary artery (the artery that carries low oxygen blood to the lungs) from the left ventricle, resulting in two separate circulation’s.
Because the great arteries are reversed, the aorta carries blood from the right ventricle. This low oxygen rich blood and likewise the pulmonary artery carries blood from the left ventricle. This is already oxygen rich blood that is being carried back to the lungs. In order for the infant born with transposition of the great arteries to survive, they must have some communication between the right and the left sides of the heart to allow oxygen rich blood to reach the body. This mixing of blood is possible through any of the following: ASD, VSD, PDA. Even though there is mixing of oxygenated and de-oxygenated blood, it is often not adequate to sustain life for an extended period of time. Babies with transposition are extremely blue at birth.
The most common surgical procedure to correct this defect is called an arterial switch operation. That is, the major arteries are "switched". The aorta is connected to the left ventricle. This allows oxygen rich blood to be pumped to the body. The pulmonary artery is connected to the right ventricle. This allows low oxygen blood to go to the lungs where it can be oxygenated. Other surgical defects may also be needed to correct the communication between the left and right sides of the heart that was once needed for survival.
Immediately after diagnosis, a medication called prostaglandin is started intravenously to maintain the small connection (the ductus arteriosus) between the pulmonary and systemic circulations. Surgery to temporarily adjust the vessels may be required shortly after birth, with permanent correction postponed until the child is older. However, a surgical technique known as an arterial switch procedure allows permanent correction within the first month of life.