Transposition of the Great Arteries (TGA)

What is Transposition of the Great Arteries?

Transposition of the great arteries (TGA) is a serious congenital heart defect in which the aorta and pulmonary artery are switched in position. This leads to a condition where oxygen-poor blood circulates throughout the body, while oxygen-rich blood remains trapped in the lungs.

TGA is considered a cyanotic heart defect, meaning it causes low oxygen levels in the body, leading to symptoms like bluish skin (cyanosis).

Types of Transposition of the Great Arteries

1. D-Transposition of the Great Arteries (D-TGA)

The most common and severe form. The aorta arises from the right ventricle, and the pulmonary artery arises from the left ventricle, causing a complete separation of oxygenated and deoxygenated blood.

2. L-Transposition of the Great Arteries (L-TGA)

A rarer form in which the ventricles are also switched, allowing blood flow to remain functional but leading to long-term complications such as heart failure or arrhythmias.

Causes and Risk Factors

TGA occurs during fetal development and is typically caused by abnormal heart formation. Possible risk factors include:

• Genetic mutations or family history of congenital heart defects
• Maternal conditions such as diabetes or viral infections (e.g., rubella)
• Poor maternal nutrition or lack of prenatal care
• Maternal alcohol, drug, or toxin exposure during pregnancy
• Chromosomal disorders (e.g., DiGeorge syndrome, Down syndrome)

Symptoms of Transposition of the Great Arteries

Symptoms usually appear immediately after birth and require urgent medical attention:

• Cyanosis (bluish skin, lips, or nails)
• Shortness of breath (dyspnea) or rapid breathing
• Weak or absent pulse in extremities
• Poor feeding or failure to gain weight
• Low oxygen levels that do not improve with oxygen therapy

If left untreated, TGA is life-threatening and requires immediate intervention.

Diagnosis of TGA

Doctors diagnose TGA using advanced imaging tests:

• Echocardiogram (ECHO): The most accurate test to visualize heart structure and function.
• Pulse Oximetry: Measures oxygen levels in newborns.
• Chest X-ray: Shows the egg-on-a-string sign, a characteristic finding in TGA.
• Cardiac MRI or CT scan: Provides detailed imaging if surgery is required.

Treatment and Management

Most newborns with TGA require immediate medical treatment after birth. The standard treatment plan includes:

1. Emergency Stabilization

• Prostaglandin Infusion: A medication to keep the ductus arteriosus open, allowing some mixing of oxygenated and deoxygenated blood.
• Balloon Atrial Septostomy (BAS): A catheter-based procedure to create an opening between the atria, improving oxygenation.

2. Corrective Surgery (Arterial Switch Procedure)

The arterial switch operation is the gold standard treatment and is typically performed within the first two weeks of life. During this procedure, the aorta and pulmonary artery are surgically switched to their correct positions.

3. Long-Term Follow-Up

Even after successful surgery, children with TGA require lifelong cardiac monitoring to detect potential complications, such as:

• Arrhythmias (irregular heart rhythms)
• Coronary artery complications
• Heart valve issues
• Exercise restrictions in some cases