Dextro-transposition of the great arteries

Dextro-Transposition of the Great Arteries

Dextro-Transposition of the Great Arteries (d-TGA) is a congenital heart defect characterized by the abnormal spatial arrangement of the two main arteries leaving the heart. In d-TGA, the aorta and the pulmonary artery are transposed, meaning they are connected to the wrong ventricles. This condition results in the circulation of oxygen-poor blood through the body and oxygen-rich blood through the lungs, leading to severe cyanosis and other complications if not corrected.

Anatomy and Pathophysiology

In a normal heart, the right ventricle pumps deoxygenated blood into the pulmonary artery, which carries it to the lungs for oxygenation. The left ventricle pumps oxygenated blood into the aorta, which distributes it to the rest of the body. In d-TGA, the aorta arises from the right ventricle, and the pulmonary artery arises from the left ventricle. This results in two parallel circulations:

• Systemic Circulation:Deoxygenated blood returns to the right atrium, flows into the right ventricle, and is pumped into the aorta, bypassing the lungs.
• Pulmonary Circulation:Oxygenated blood returns to the left atrium, flows into the left ventricle, and is pumped back into the pulmonary artery, returning to the lungs.

This arrangement prevents oxygenated blood from reaching the systemic circulation, causing cyanosis and hypoxia.

Clinical Presentation

Infants with d-TGA typically present with cyanosis shortly after birth. Other symptoms may include:

• Tachypnea (rapid breathing)
• Poor feeding
• Lethargy
• Heart murmur

Without intervention, d-TGA can lead to severe hypoxemia and acidosis, which are life-threatening.

Diagnosis

Diagnosis of d-TGA is often made using echocardiography, which can visualize the transposed great arteries. Other diagnostic tools include:

• Chest X-ray:May show an "egg on a string" appearance due to the narrow mediastinum and enlarged heart.
• Electrocardiogram (ECG):May show right ventricular hypertrophy.
• Cardiac catheterization:Can provide detailed anatomical information and assess the degree of mixing between the circulations.

Treatment

The primary treatment for d-TGA is surgical correction. The most common procedure is the arterial switch operation, which involves:

1. Switching the great arteries:The aorta and pulmonary artery are reconnected to the correct ventricles. 2. Reimplanting the coronary arteries:Ensuring adequate blood supply to the heart muscle.

Before surgery, temporary measures such as prostaglandin E1 infusion may be used to maintain ductal patency and improve oxygenation. Balloon atrial septostomy can also be performed to enhance mixing of oxygenated and deoxygenated blood.

Prognosis

With successful surgical correction, most children with d-TGA can lead normal lives. Long-term follow-up is necessary to monitor for potential complications such as coronary artery problems, arrhythmias, or heart failure.

Also see

• Congenital heart defect
• Cyanotic heart defect
• Arterial switch operation
• Balloon atrial septostomy