Dextro-transposition of the great arteries (d-TGA)
Dextro-transposition of the great arteries, or d-TGA, is a congenital heart disease in which the two main arteries that carry blood from the heart, the main pulmonary artery and the aorta, are inverted or "transposed." Because a child with this defect may require surgery or other procedures shortly after birth, d-TGA is considered a critical congenital heart disease.
In TGA, the aorta is anterior to the pulmonary artery and is mostly either to the right (dextro) or to the left (levo). Levo-TGA is less common than dextro-TGA.
In a child without congenital heart disease, the right side of the heart pumps oxygen-poor blood from the heart to the lungs via the pulmonary artery. The left side of the heart pumps oxygen-rich blood to the rest of the body through the aorta. The aorta is usually located behind the pulmonary artery.
In children with d-TGA, the oxygen-poor blood from the body goes to the right side of the heart. But instead of going to the lungs, the blood returns directly to the rest of the body through the aorta. Oxygenated blood from the lungs to the heart is pumped directly to the lungs through the main pulmonary artery.
Often, children with d-TGA have other heart defects, such as a hole between the lower chambers of the heart (ventricular septal defect) or the upper chambers of the heart (atrial septal defect), which allow blood to mix so that some oxygen-rich blood can be pumped to the rest of the body . The permanence of the ductus arteriosus also allows it to pump oxygen-rich blood to the rest of the body.
Causes and risk factors
The causes of congenital heart defects such as d-TGA are unknown in most children. Some children have congenital heart defects due to changes in their genes or chromosomes. It is also believed that heart defects are caused by a combination of genes and other risk factors, such as objects that the mother comes into contact with in her environment, or what the mother eats or drinks, or certain medications She takes.
Diagnosis
This defect can be diagnosed during pregnancy or shortly after the baby is born.
During pregnancy
During pregnancy, the mother may have screening tests (also called prenatal tests) to check for birth defects and other conditions. d-TGA can be diagnosed during pregnancy with an ultrasound. Some ultrasound results may lead the doctor to suspect that the baby may have d-TGA. If so, the doctor may order a fetal echocardiogram to confirm the diagnosis. A fetal echocardiogram is a more detailed ultrasound of the baby's heart. This test can show problems with the structure of the heart and how the heart works with this defect.
After the birth of a child
Symptoms occur at birth or shortly thereafter. The severity of the symptoms will depend on whether the blood can mix and the oxygen-rich blood gets to the rest of the body. For example, if an infant with d-TGA has another defect, such as an atrial septal defect (ASD), the atrial septal defect forms a passage to pump oxygen-rich blood to the rest of the body. In this infant with both d-TGA and an atrial septal defect, symptoms may not be as severe as in infants whose hearts do not have mixed blood. Infants with d-TGA may have a bluish skin color called cyanosis because their blood does not contain enough oxygen. Infants with d-TGA or other conditions that cause cyanosis may have symptoms such as:
- Problems breathing
- Pounding heart
- Weak pulse
- Ashen or bluish skin color
- Poor feeding
Because the infant may be bluish in color and have difficulty breathing, d-TGA is usually diagnosed in the first week of life. The doctor may order one or more tests to confirm the diagnosis. The most common test is an echocardiogram. An echocardiogram is an ultrasound of the heart that can show problems with the structure of the heart, such as misalignment of two large arteries and any irregular blood flow. An electrocardiogram, which measures the electrical activity of the heart, a chest x-ray, and other medical tests can also be used to make a diagnosis.
d-TGA can also be detected on neonatal pulse oximetry screening. Pulse oximetry is a simple bedside test to measure the amount of oxygen in a baby's blood. Low blood oxygen levels can be a sign of critical congenital heart disease. Newborn screening with pulse oximetry can detect some infants with critical congenital heart defects such as d-TGA before they develop symptoms.
Treatment
Surgery is required for all children born with d-TGA. Other procedures may be performed prior to surgery to preserve, enlarge, or create holes that allow oxygen-rich blood to flow into the body.
There are two types of d-TGA repair operations:
- Arterial Switch Operation: This is the most common procedure, usually performed in the first month of life. It restores normal blood flow through the heart and to the rest of the body. During this operation, the arteries are switched to their normal position - the pulmonary artery coming from the right ventricle and the aorta coming from the left ventricle. The coronary arteries (small arteries that supply blood to the heart muscle) also need to be moved and reattached to the aorta.
- Atrial Switch Operation: This procedure is less common. During this operation, the arteries are left in place, but a tunnel is created between the upper chambers (atria) of the heart. This tunnel allows oxygen-poor blood to pass from the right atrium to the left ventricle and from the pulmonary artery to the lungs. Returned oxygen-rich blood travels through a tunnel from the left atrium to the right ventricle and from the aorta to the body. While this repair helps blood get to the lungs and then to the body, the right ventricle also needs extra work to pump blood around the body. Therefore, this repair can lead to difficulties later in life.
After surgery, medication may be needed to help the heart work better, control blood pressure, help flush excess fluid from the body, and slow down the heart if it beats too fast. If the heart beats too slowly, a pacemaker may be used.
Babies who have these operations are not cured; they may have lifelong complications. A child or adult with d-TGA will need regular follow-up visits with a cardiologist to monitor their progress and avoid complications or other health problems. With the right treatment, most children with d-TGV grow up to be healthy and productive.