Transposition of the Great Vessels


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 circulationís.

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.

  Normal      Transposition

In this situation, the pulmonary arteries are supplied by the left ventricle, and the aorta by the right ventricle. This, of course, is the opposite of the normal arrangement. Infants can only survive if there is a shunt between the two sides of the heart, and an atrial septal defect needs to be actually enlarged to allow adequate mixing of blood to deliver enough oxygenated blood to the body. Significant advances have been made in the surgical treatment of this disorder.

Illustrations

The interior of the heart is composed of valves, chambers, and associated vessels.

The external structures of the heart include the ventricles, atria, arteries and veins. Arteries carry blood away from the heart while veins carry blood into the heart. The vessels colored blue indicate the transport of blood with relatively low content of oxygen and high content of carbon dioxide. The vessels colored red indicate the transport of blood with relatively high content of oxygen and low content of carbon dioxide. Transposition of the great vessels is a congenital heart defect in which the position of the two major vessels that carry blood away from the heart - the aorta and the pulmonary artery - is switched (transposed). This defect is classified as a cyanotic heart defect because the condition results in insufficiently oxygenated blood pumped to the body which leads to cyanosis (a bluish-purple coloration to the skin) and shortness of breath.

Alternative names    Return to top

Transposition of the great arteries

Definition    Return to top

Transposition of the great vessels is a congenital heart defect in which the 2 major vessels that carry blood away from the heart -- the aorta and the pulmonary artery -- are switched (transposed).

Causes, incidence, and risk factors    Return to top

The cause of most congenital heart defects is unknown. Prenatal factors associated with a higher than normal incidence of these disorders include maternal rubella or other viral illnesses during pregnancy, poor prenatal nutrition, maternal alcoholism, maternal age over 40, and diabetes, although it is unclear if any of these actually cause the problem.

Transposition of the great vessels is classified as a cyanotic heart defect because the condition results in insufficiently oxygenated blood pumped to the body which leads to cyanosis (a bluish-purple coloration to the skin) and shortness of breath.

In transposition of the great vessels, there is no communication between the pulmonary circulation and the systemic circulation. Fresh oxygenated blood from the lungs returns to the heart ready to nourish the body, but instead is whisked right back to the lungs. Conversely, oxygen-poor blood returns from the body to the heart and is then sent right back out to the body without being reoxygenated. There is usually an associated defect that permits the mixing of the systemic and pulmonary circulation to provide some oxygenated blood to the body. Without such a defect, the condition is rapidly fatal.

Symptoms appear at birth or very soon afterwards. The severity of the symptoms depends upon the type of associated defect and the resulting amount of oxygenated blood supplied to the general circulation. The condition affects approximately 40 out of 100,000 infants. It is the most common cyanotic heart defect identified in the first week of life.

Symptoms    Return to top

Signs and tests    Return to top

The health care provider may detect a heart murmur while listening to the chest with a stethoscope.

Tests often include the following:

Treatment    Return to top

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.

Expectations (prognosis)    Return to top

Improvement in symptoms and growth and development is seen after surgical correction of the defect. If corrective surgery is not performed, the life expectancy is shortened.

Complications    Return to top

Calling your health care provider    Return to top

This condition is usually diagnosed when a baby is born. Go to the emergency room or call the local emergency number such as 911 if your baby's skin develops a bluish color.

Call the health care provider if your baby has this disorder and new symptoms develop, become worse over time, or if symptoms continue after treatment.

Prevention    Return to top

Women who plan to become pregnant should be immunized against rubella if they are not already immune. Good nutrition, avoiding alcohol, and control of diabetes both before and during pregnancy may be helpful.

 

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