Transposition of the Great Arteries NCLEX Review

Transposition of the great arteries (TGA) review for nursing students!

In this review you will learn about the congenital heart defect known as transposition of the great arteries (TGA). This is a topic you will see on your pediatric nursing lecture exams and possibly the NCLEX exam.

After reviewing these notes, don’t forget to take the quiz that contains transposition of the great arteries NCLEX questions and to watch the lecture.

Transposition of the Great Arteries Lecture

Transposition of the Great Arteries NCLEX Review

What is transposition of the great arteries? It’s a congenital heart defect where the pulmonary artery and aorta are in SWITCHED positions (hence transposed).

Quick Facts of TGA

• Also called “transposition of the great vessels, TGA, or TGV”
• No communication exists between the right and left side of the heart
  • Each side of the heart has its own circulation, and it’s the opposite of how circulation should occur in a normal heart.
    • Hence pulmonary circulation will be on the left side (rather than the right) and systemic circulation will be on the right side (rather than the left).
    • These sides are not working together and this leads to no oxygenated blood going to the body and tissues. It’s deadly, if not treated!
  • Some babies may have slight communication between each side if another type of congenital defect is present (many times this is the case). If this is the case, it provides short-term benefits until surgery can be performed to correct the defect.
    • Other types of defects present in TGA:
      • ventricular septal defect: hole in the ventricular septum
      • atrial septal defect: hole in the atrial septum
      • patent ductus arteriosus: this is a vessel connection between the pulmonary artery and aorta that should close after birth. If kept open in TGA, it will allow mixing of unoxygenated blood with oxygenated, so at least SOME oxygenated blood is going to the body via the aorta.
    • It’s a critical congenital heart defect that requires immediate medical intervention after birth and surgery within the first month of life.
  • According to CDC.gov , 1 on 3,330 babies are born with this condition each year in the United States.
  • It’s typically discovered during a prenatal visit during a fetal ultrasound and echocardiogram can be used to diagnose it.

To understand transposition of the great arteries remember this basic anatomy:

• The pulmonary artery comes off the left ventricle, not the right ventricle as in TGA.
• The aorta comes off the right ventricle, no the left ventricle as in TGA.

The pulmonary artery should carry unoxygenated blood RIGHT to the lungs to get oxygenated, while the aorta should carry oxygenated blood that has LEFT the lungs to go to the body. In transposition of the great arteries, the opposite is occurring.

Key concept of anatomy for TGA: The pulmonary artery is carrying oxygenated blood that is just re-circulating over and over to the lungs and NEVER going to the body. The aorta is carrying unoxygenated blood and pumping it all over the body. The is very futile because it won’t meet the body’s oxygen demands.

Normal blood flow in a heart without TGA

Blood flow starts on the RIGHT SIDE of the heart

The goal of the right side is to get the UNOXYGENATED blood to the LUNGS!

The un-oxygenated blood (this is blood that has been “used-up” by your body that needs to be resupplied with oxygen) enters to the heart through the SUPERIOR AND INFERIOR VENA CAVA.

Blood enters into the RIGHT ATRIUM

Then it is squeezed through the TRICUSPID VALVE

Blood then enters into the RIGHT VENTRICLE

Then it is squeezed into the PULMONIC VALVE

Blood is then shot-up through the PULMONARY ARTERY and then enters into the lungs for some oxygen

Left Side of the Heart

The goal of the left side of the heart is to get the richly, oxygenated blood to the body to feed the brain, tissue, muscles, organs etc.

Blood enters from the lungs through the PULMONARY VEIN that has just been refreshed with oxygen to go into the LEFT ATRIUM

Down through the BICUSPID VALVE (also called mitral valve)

Then blood is squeezed into the LEFT VENTRICLE

Up through the AORTIC VALVE

Lastly up through the AORTA, where it pumped throughout the body

In fetal circulation (while a baby is still in the uterus), the placenta is providing the oxygen, and the  blood in the fetus’ heart is flowing a little bit differently than compared to how it will flow after birth.

After birth, pressure will change in the heart and lungs, which will cause certain bypasses in the heart to seal off. The purpose of this “sealing off” of bypasses is to allow the right side of the heart to pump blood to the lungs to become oxygenated (remember the placenta’s role is over). Note: the lungs are non-functional in utero.

One of these bypasses is called the formen ovale (it’s found in between the atria). Another bypass is called the ductus arteriosus (this structure allows blood to flow from the pulmonary artery and aorta).

In a patient who has TGA when these structures normally starts to close (like their supposed to), cyanosis that is already present can become WORST.

This is why treatment may include: keeping the patent ductus arteriosus open with prostaglandin E and enlarging the foramen ovale or an ASD (if present) to allow blood to keep mixing until open heart surgery is performed.

Blood Flow in a Heart with Transposition of the Great Arteries

Blood enters as it normally should through the superior/inferior vena cava and goes to the right side. The right side is pumping blood to the body via the AORTA (normally the aorta should carry oxygenated blood from the left side of the heart) that is unoxygenated rather than to the lungs. The left side is just re-circulating oxygenated blood from the lungs via the pulmonary artery that can NOT get to the systemic circulation.

Signs and Symptoms of Transposition of Great Arteries

Signs and symptoms are noticed after birth…severity depends on if other defects may be present as well, which will help with mixing of blood.

Signs and symptoms are present shortly after birth

CYANOSIS after birth that is mild to severe is present…..a bluish body and extremities and this is due to low oxygen levels!!

These babies are going to be extremely BLUE and will stay that way….depending on if they have other defects will determine the severity…some may have cyanosis that will majorly become worst.

The low oxygen levels in the body will lead to an increased respiratory rate, increased heart rate, cool extremities, poor feeding and growth rate and eventually heart failure can occur.

Nursing Interventions and Treatment for Transposition of the Great Arteries

“SWAP”

Severe Cyanosis at birth that won’t resolve without medical intervention (*degree of cyanosis depends on if any other defects are present that may allow blood to mix and the cyanosis will continue to get worst as the ductus arteriosus and foramen ovale close off)

Watch heart rate, rhythm, respiratory status, oxygen levels, and prepare for intervention (prostaglandin E infusion, balloon atrial septostomy, and then open heart for an arterial switch procedure.

Alprostadil (prostaglandin E)…medication infusion given to keep patient ductus arteriosus open (normally would close at birth) to allow mixing of blood…this is the connection between the aorta and pulmonary artery

Procedures to correct:

• Balloon atrial septostomy…. TEMPORARY UNTIL SURGERY…. Performed during a heart cath: to enlarge a hole in atrial septum….catheter is inserted into the heart through a vessel to enlarge the formen ovale or an atrial septal defect already present
  • WHY? this allows unoxygenated and oxygenated blood to mix and enter systemic circulation….temporary until surgery can be performed.
• Arterial switch procedure: open heart surgery where the pulmonary artery and aorta are switched back to where they should be along with their coronary arteries (performed within the first few weeks of life).

References: