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

The cause of most congenital heart defects is unknown.

Factors associated with a higher than normal rate of this disease include:

• Rubella or other viral illness in the mother during pregnancy
• Poor nutrition in the mother during pregnancy (prenatal nutrition)
• Alcoholism
• Mother's age over 40
• Diabetes

Transposition of the great vessels is a cyanotic heart defect. This means there is too little oxygen in the blood that is pumped from the heart to the rest of the body. Low blood oxygen leads to cyanosis (a bluish-purple color to the skin) and shortness of breath.

In normal hearts, blood coming back from the body goes through the lungs to get oxygen and then back to the body. In transposition of the great vessels, the blood that goes through the body lacks oxygen.

Symptoms appear at birth or very soon afterwards. How bad the symptoms are depends on the type and size of the associated heart defects (such as atrial septal defect or patent ductus arteriosus) and how much oxygen moves through the body's general blood flow. The condition is the second most common cyanotic heart defect.

• Blueness of the skin
• Shortness of breath
• Poor feeding
• Clubbing of the fingers or toes

The health care provider may detect a heart murmur while listening to the chest with a stethoscope. The baby's mouth and skin would be a blue color.

Tests often include the following:

• Chest x-ray
• Cardiac catheterization
• ECG
• Echocardiogram (if done before birth, it is called a fetal echocardiogram)
• Pulse oximetry (to check blood oxygen level)

The baby will immediatley receive a medicine called prostaglandin through an IV (intravenous line). This medicine helps blood flow through the lungs and body.

A procedure using cardiac catheterization (balloon atrial septostomy) may be needed to create a large hole in the atrial septum to allow blood to mix.

In most hospitals, a type of surgery called an arterial switch procedure can be used to permanently correct the problem within the first week of life. This surgery switches the great arteries back to the normal position along with the coronary arteries.

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.

• Arrhythmias
• Heart valve problems
• Coronary artery disease

This condition can be diagnosed before birth using a fetal echocardiogram. If it is not, it is usually diagnosed soon after 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 condition and new symptoms develop, get worse, or continue after treatment.

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

Zipes DP, Libby P, Bonow RO, Braunwald E, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 8th ed. St. Louis, Mo; WB Saunders; 2007.