Transposition of the Great Arteries (TGA)

What happens in transposition of the great arteries

In a normal heart, blood flows in a figure-of-eight:

• The right ventricle pumps oxygen-poor blood to the lungs through the pulmonary artery.
• The left ventricle pumps oxygen-rich blood to the body through the aorta.

In TGA, these two arteries are swapped. This creates two separate, parallel circuits:

• Oxygen-poor blood from the body returns to the right side and is pumped straight back out to the body.
• Oxygen-rich blood from the lungs returns to the left side and is pumped straight back to the lungs.

Survival after birth depends on mixing between the two circuits through openings that are normal before birth: the foramen ovale (a gap between the upper chambers, like a small atrial septal defect) and the ductus arteriosus (between the aorta and pulmonary artery; see patent ductus arteriosus). These start to close in the first hours to days of life, which is when the baby becomes severely blue.

Some babies also have a ventricular septal defect (a hole between the pumping chambers), which improves mixing, or pulmonary stenosis.

Types

The rest of this page is about d-TGA.

Symptoms

• Cyanosis: blue lips, tongue and skin, usually within the first hours to days, not improved by oxygen
• Fast breathing without much distress at first
• Poor feeding and sleepiness
• Signs of shock if the ductus closes: cold, mottled skin, weak pulses
• A heart murmur only if there are associated defects

Causes and risk factors

The cause is usually unknown. TGA develops in the first 8 weeks of pregnancy when the large vessels of the heart form. Associated factors include:

• Diabetes in pregnancy, especially if poorly controlled
• Male sex
• Older maternal age and some medicines or exposures in early pregnancy
• Unlike many congenital heart defects, TGA is less often linked to chromosome abnormalities

How TGA is diagnosed

• Prenatal ultrasound and fetal echocardiogram: many cases are detected during the mid-pregnancy anatomy scan. Prenatal diagnosis allows delivery at a cardiac center and improves outcomes.
• Newborn pulse oximetry screening: a painless sensor on the hand and foot measures oxygen levels before discharge. Low readings prompt further testing.
• Echocardiogram (heart ultrasound): distinguishes TGA from other causes of a blue newborn, such as tetralogy of Fallot and hypoplastic left heart syndrome, confirms the diagnosis and shows associated defects and the coronary artery pattern, which matters for surgery.
• Chest X-ray: may show an "egg on a string" heart shape.
• Cardiac catheterization: occasionally, for complex anatomy or during septostomy.

Treatment

Immediate care

• Prostaglandin E1 (alprostadil) infusion keeps the ductus arteriosus open to allow mixing.
• Balloon atrial septostomy: if oxygen levels remain low, a catheter with a balloon is passed through a vein into the heart and the balloon is pulled through the foramen ovale to enlarge it. This can be done at the bedside with ultrasound guidance.
• Breathing support and intensive care monitoring.

Arterial switch operation

The definitive treatment for d-TGA is the arterial switch operation, usually performed in the first 1 to 2 weeks of life:

1. The aorta and pulmonary artery are cut above the valves and switched to their correct ventricles.
2. The coronary arteries, which supply the heart muscle, are moved with a small button of tissue to the new aorta. This is the most delicate step.
3. Associated holes such as a VSD are closed.

Surgery is done early because the left ventricle, which pumps to the lungs before surgery, loses strength within weeks if it does not have to pump against body pressure.

Other operations

• Rastelli procedure: for TGA with a VSD and narrowing below the pulmonary valve.
• Atrial switch (Mustard or Senning): the older approach, redirecting blood at the level of the upper chambers. Adults who had this operation need close follow-up for heart rhythm problems and weakening of the right ventricle.

Long-term follow-up and complications

Lifelong care with a congenital heart specialist is recommended. Possible late issues after the arterial switch include:

• Narrowing of the pulmonary arteries or the new connections, sometimes needing catheter balloon treatment or surgery
• Widening of the new aortic root and leakage of the aortic valve
• Coronary artery narrowing, which can cause heart muscle strain
• Heart rhythm problems (less common than after atrial switch)
• Learning, attention or motor difficulties in some children, so developmental follow-up is advised

Endocarditis prevention with dental hygiene, and antibiotic prophylaxis when advised, is part of care.

Outlook

Before surgery existed, most babies with TGA died within the first year. Today, survival after the arterial switch operation is well over 90%, and most children lead active lives, attend school and take part in sports, with guidance from their cardiologist. Women who have had an arterial switch can usually have pregnancies with specialist care.

Frequently asked questions

What is transposition of the great arteries?

It is a congenital heart defect in which the aorta and pulmonary artery are attached to the wrong pumping chambers. Oxygen-poor blood circulates to the body instead of the lungs, so babies become blue soon after birth. It needs urgent treatment and surgery in the first weeks of life.

How is TGA treated in newborns?

Newborns receive prostaglandin E1 to keep a natural blood vessel open so blood can mix. Some need a balloon atrial septostomy to enlarge a hole between the upper chambers. The arterial switch operation, usually in the first 1 to 2 weeks, corrects the circulation permanently.

What is the life expectancy after an arterial switch?

Long-term survival after a successful arterial switch is excellent, and most patients are now living well into adulthood. Because the first patients are only now in their 40s, the full lifespan is still being studied. Lifelong cardiology follow-up helps detect and treat later problems early.

Can TGA be detected before birth?

Yes. Many cases are found on the mid-pregnancy anatomy ultrasound and confirmed with a fetal echocardiogram. Prenatal diagnosis allows the baby to be born at a hospital with pediatric heart surgery, which improves early safety.

What causes transposition of the great arteries?

The exact cause is usually unknown. It happens when the major arteries develop abnormally in the first 8 weeks of pregnancy. Diabetes in the mother and male sex of the baby are associated factors. It is usually not caused by anything the parents did.