Transposition of the Great Arteries

Transposition of the Great Arteries is one of the cyanotic congenital heart disorders in which the two main arteries leaving the heart are reversed (transposed).

Transposition of the great vessels is a cyanotic heart defect. This means there is decreased oxygen in the blood that is pumped from the heart to the rest of the body.

In normal hearts, blood that returns from the body goes through the right side of the heart and pulmonary artery to the lungs to get oxygen. The blood then comes back to the left side of the heart and travels out the aorta to the body.

In transposition of the great vessels, the blood goes to the lungs, picks up oxygen, returns to the heart, and then flows right back to the lungs without ever going to the body. Blood from the body returns to the heart and goes back to the body without ever picking up oxygen in the lungs.

Etiology
Etiology for transposition of the great arteries is unknown and is presumed to be multifactorial. Preexisting diabetes mellitus of an expectant mother is a risk factor that has been described for the fetus having TGV.

Clinical Presentation
Infants with transposition of the great arteries (TGA) are usually born at term, with cyanosis apparent within hours of birth.

The clinical course and manifestations depend on the extent of intercirculatory mixing and the presence of associated anatomic lesions.

The common findings include:

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

Workup
If a baby is suspected to have this condition the following tests are usually required:
Tests often include the following:

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

Management

Maintaining the Ductal PatencyInitial treatment consists of maintaining ductal patency with continuous intravenous (IV) prostaglandin E1 infusion to promote pulmonary blood flow, increase left atrial pressure, and promote left-to-right intercirculatory mixing at the atrial level. This is particularly important in patients with severe left ventricular outflow tract stenosis or atresia. Prostaglandin therapy may or may not benefit the patient with simple transposition of the great arteries (TGA) and an intact ventricular septum without left ventricular outflow tract obstruction.

Initial Supportive Care

• For the ill neonate, metabolic acidosis should be corrected with fluid replacement and bicarbonate administration.
• Mechanical ventilation may be necessary if pulmonary edema develops in concert with severe hypoxemia.
• Ultimately, the patient requires surgical repair or palliation early in life.

Surgery
Surgical approach depends on the age of the patient at presentation, the presence of associated congenital cardiac lesions, and the experience of the cardiothoracic surgeon with a given surgical technique. Most full-term neonates with uncomplicated transposition of the great arteries can undergo an arterial switch procedure in one operation, with minimal mortality.

A surgery called an arterial switch procedure is used to permanently correct the problem within the baby’s first week of life. This surgery switches the great arteries back to the normal position and keeps the coronary arteries attached to the aorta.

Prognosis
The child’s symptoms will improve after surgery to correct the defect. Most infants who undergo arterial switch do not have symptoms after surgery and live normal lives. If corrective surgery is not performed, the life expectancy is only a few months.