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Transposition of the Great Arteries

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What is TGA or transposition of the great arteries? It’s a congenital heart defect that occurs when the positions of the pulmonary artery and aorta are swapped (it’s “transposed”).

Notes on TGA:

  • Known as “transposition of the great vessels, TGA, or TGV”
  • There is no connection between the right and left sides of the heart. The right and the left side of the heart have different movements in terms of circulation
  • Deoxygenated blood travels through the left side of the heart rather than the right; and oxygenated blood travels through the right part of the heart rather than the left
  • Oxygenated blood does not go through the body tissues resulting in death if not dealt with immediately
  • Signs and symptoms are the same as Tetralogy of Fallot
  • An update from CDC: 1 in 3,413 babies is affected by this condition in the United States.
  • TGA is diagnosed during pregnancy or soon after birth

Normal Circulation

Fetal Circulation 

  • The placenta is the main support of the fetus throughout pregnancy 
  • Deoxygenated blood passes from the fetus to the mother through the placenta by the umbilical cord. When blood enters the fetus through the placenta, the blood gets oxygen from the placenta and travels through the umbilical cord vessels, the third vessel to be exact.
  • Oxygenated blood will now pass through the umbilical vein passing through the liver of the fetus and then will go in via the right side of the heart. 

Fetal Heart Anatomy

Newborn Circulation – After birth, there is a major transition of how the blood circulation flows. That means the foramen ovale and ductus arteriosus close.

  • 4 chambers of the heart: Left and right Atrium; and left and right ventricle
  • 2 shunts: 
    • Foramen Ovale – opening that connects the left and right side of the heart
    • Ductus arteriosus – opening from the right ventricle to the aorta but blood doesn’t pass through the lungs yet;instead, it will pass through the umbilical cord to the placenta

Two Types of TGA:

Complete transposition of the great arteries (D-TGA)

  • Also called dextro-transposition of the great arteries
  • The aorta and pulmonary artery have exchanged positions
  • The pulmonary artery is connected to the left ventricle while the aorta is connected to the right ventricle

What happens here?

Deoxygenated blood doesn’t pass through the lungs before circulating to the body; while oxygenated blood from the left side of the heart goes right into the lungs and doesn’t get pumped to the body. 

Congenitally corrected transposition (L-TGA)

  • Also called levo-transposition of the great arteries (L-TGA)
  • Less common type
  • The two heart ventricles are switched

What happens here?

The left ventricle that’s transposed to the right side connects to the pulmonary artery, which carries deoxygenated blood to the lungs, while the right ventricle that’s transposed to the left side connects to the aorta, which carries oxygenated blood to the body. Because the upper and lower heart chambers aren’t alike, the heart can have problems pumping blood. People with this condition can also have tricuspid heart valve problems.

Diagnostic Tests

  1. Pulse oximetry – In 2011, this test looks like a band-aid that is taped on the newborn’s wrist. This test is normally 5 minutes long. This is mandated by law in New Jersey and Maryland
  2. Echocardiogram (ECG)
  3. Chest X-ray
  4. Cardiac catheterization

Signs and Symptoms (present shortly after birth):

  1. Cyanosis – signs show bluish discoloration of the body due to lack of oxygen supply to the tissues. 
  2. Increased respiratory rate – due to the body compensating for low oxygenation of the body tissues
  3. Increased heart rate
  4. Cool to touch extremities with long capillary refill
  5. Poor feeding
  6. Worst case scenario is heart failure then death

Treatment

Medication – Prostaglandin E1 (alprostadil) is administered intravenously as prescribed by doctors. Prostaglandin E1 hinders the closure of the ductus arteriosus thus enabling the newborn’s body to have an alternate passageway for the blood to flow while waiting for the surgical procedure. 

Cardiac Catheterization – this procedure is done before the surgery. This is also known as the balloon atrial septostomy. Doctors use a special catheter to make the pathway larger or make an opening to the atrial wall in between the left and right atria.

Surgery – the surgical procedure for TGA is called “arterial switch”. The lungs and the heart arteries are disconnected and switched back and reconnected to the respective ventricles. In this procedure, the holes in the chambers of the heart are properly closed.

Nursing Interventions and Treatment

  1. Assessment of the heart rate and blood pressure
  2. Take note of the temperature, color, and moisture of the skin
  3. Check for capillary refill and peripheral pulses
  4. Monitor the rhythm of the heart, heart rate, and the ectopy
  5. Position child on the semi fowler’s position
  6. Administer medications that are prescribed by the doctors
  7. Educate the family about TGA and other underlying defects that are detected after birth with the same signs such as cyanosis, increased respiratory rate, increased heart rate, with an Apgar score of below 7.