Transposition of the Great Arteries

Heart With Transposition of the Great Arteries

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The aorta normally originates from the left ventricle and is the main artery that carries oxygen-rich blood to the body. The pulmonary artery is the main artery that carries deoxygenated blood from the right ventricle to the lungs. In a case of transposition of the great arteries, these two main arteries are inverted. In other words, the aorta originates from the right ventricle and the pulmonary artery originates from the left ventricle.

Therefore, the pulmonary artery carries oxygenated blood from the left ventricle back to the lungs and the aorta carries deoxygenated blood from the right ventricle to the body causing the baby to appear cyanotic, or blue. Without a way for the oxygenated blood of the left ventricle to reach the aorta and, in turn, the rest of the body, the child will not survive. Often, an associated ASD or VSD is present allowing blood to flow between the right and left sides of the heart.

In other cases, a PDA is present allowing blood flow between the pulmonary artery and aorta. Early surgical correction is essential. The procedure, known as the Arterial Switch operation, involves transposing the two great arteries as well as the coronary arteries (the small blood vessels that supply oxygenated blood to the heart muscle itself).

What Is Normal Cardiac Anatomy?

When your child has a congenital heart defect, there's usually something wrong with the structure of his or her heart's structure.

Learn More About Normal Cardiac Anatomy

Heart With Normal Cardiac Anatomy

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When your child has a congenital heart defect, there's usually something wrong with the structure of his or her heart's structure.

The heart is composed of four chambers. The two upper chambers, known as atria, collect blood as it flows back to the heart. The two lower chambers, known as ventricles, pump blood with each heartbeat to the two main arteries (the pulmonary artery and the aorta). The septum is the wall that divides the heart into right and left sides. The atrial septum separates the right and left atria; likewise, the ventricular septum separates the two ventricles.

There are four valves that control the flow of blood through the heart. These flap-like structures allow blood to flow in only one direction. The tricuspid and mitral valves, also known as the atrioventricular valves, separate the upper and lower chambers of the heart. The aortic and pulmonary valves, also known as the arterial valves, separate the ventricles from the main arteries. Oxygen-depleted blood returns from the body and drains into the right atrium via the superior and inferior vena cavas. The blood in the right atrium then passes through the tricuspid valve and enters the right ventricle.

Next, the blood passes through the pulmonary valve, enters the pulmonary artery, and travels to the lungs where it is replenished with oxygen. The oxygen-rich blood returns to the heart via the pulmonary veins, draining into the left atrium. The blood in the left atrium passes through the bicuspid, or mitral, valve and enters the left ventricle.

Finally, the oxygen-rich blood flows through the aortic valve into the aorta and out to the rest of the body.

Congenital Heart Defects

A congenital heart defect is a problem in the heart's structure that is there when a baby is born. About 1 in every 100 newborns have congenital heart defects, which can range from mild to severe.

Congenital heart defects happen because of incomplete or abnormal development of the fetus' heart during the very early weeks of pregnancy. Some are known to be associated with genetic disorders, such as Down syndrome. But the cause of most congenital heart defects is unknown. While they can't be prevented, there are many treatments for the defects and related health problems.

How a Healthy Heart Works

To know more about congenital heart defects, it helps to understand how a healthy heart works.

The heart, lungs, and blood vessels make up the circulatory system. The heart is the central pump of this system, and consists of four chambers — the left atrium and left ventricle and the right atrium and right ventricle.

The heart also has four valves that direct the flow of blood through the heart:

  1. The left atrium of the heart receives oxygen-rich blood from the lungs and then empties into the left ventricle through the mitral valve.
  2. The left ventricle pumps oxygen-rich blood out to the rest of the body. Blood leaves the left ventricle through the aortic valve and enters the aorta, the largest artery (a blood vessel that carries oxygenated blood) in the body. Blood then flows from the aorta into the branches of many smaller arteries, providing the body's organs and tissues with the oxygen and nutrients they need.
  3. After oxygen in the blood is released to the tissues, the now deoxygenated (oxygen-poor) blood returns to the heart through veins, the blood vessels that carry deoxygenated blood. This blood, which looks blue, enters the right atrium of the heart and then travels across the tricuspid valve into the right ventricle.
  4. The right ventricle then pumps deoxygenated blood through the pulmonic valve into the lungs. The oxygen in the air we breathe binds to cells within this blood that is being pumped through the lungs. The oxygen-rich blood, which appears red, then returns to the left atrium and enters the left ventricle, where it is pumped out to the body once again.

This is the normal pathway that blood travels through the heart and the body. However, abnormalities in the heart's structure — such as congenital heart defects — can affect its ability to work as it should.

Common Heart Defects

Common types of congenital heart defects, which can affect any part of the heart or its surrounding structures, include:

Aortic Stenosis

In aortic stenosis, the aortic valve is stiffened and has a narrowed opening. It does not open properly, which strains the heart because the left ventricle has to pump harder to send blood out to the body. Sometimes the aortic valve also does not close properly, causing it to leak, a condition called aortic regurgitation.

Atrial Septal Defect (ASD)

ASD is a hole in the wall (called the septum) that separates the left atrium and the right atrium. This wall is called the atrial septum. This hole allows extra blood flow to travel from the left atrium into the right heart and out to the lungs.

Atrioventricular Canal Defect

This defect — also known as endocardial cushion defect or atrioventricular septal defect — is caused by a poorly formed central area of the heart. Typically, there is a large hole between the upper chambers of the heart (the atria) and, often, an additional hole between the lower chambers of the heart (the ventricles). Instead of two separate valves allowing flow into the heart (tricuspid on the right and mitral valve on the left), there is one large common valve, which may be quite malformed. Atrioventricular canal defect is commonly seen in children with Down syndrome.

Coarctation of the Aorta

Coarctation of the aorta is a narrowing of a portion of the aorta, and often seriously decreases the blood flow from the heart out to the lower portion of the body.

Hypoplastic Left Heart Syndrome

When the structures of the left side of the heart (the left ventricle, the mitral valve, and the aortic valve) are underdeveloped, they can't pump blood adequately to the entire body. This condition is usually diagnosed within the first few days of life, at which point the baby may be critically ill. Fortunately, many of these problems are found before birth on ultrasound tests. A fetal echocardiogram is a specialized ultrasound that lets doctors see the baby's heart in great detail and plan the best care for the baby.

Patent Ductus Arteriosus (PDA)

The ductus arteriosus is a normal blood vessel in the developing fetus that diverts blood away from the lungs and sends it directly to the body. (The lungs are not used while the unborn fetus is in amniotic fluid — the fetus gets oxygen directly from the mother's placenta.) The ductus usually closes on its own shortly after birth; it is no longer needed once a newborn breathes independently. Patent ductus arteriosus (PDA) is when the ductus doesn't close, which can cause too much blood flow to a newborn's lungs. PDA is common in premature babies.

Patent Foramen Ovale (PFO)

The patent foramen ovale is a normal hole between the upper chambers of the heart. It usually closes in the first few months of life. In about 25% of people, this hole never fully closes. Usually, it does not cause problems and does not require treatment.

Pulmonary Atresia

In this defect, the pulmonic valve does not open at all and might even be completely absent, so that no blood can flow from the right ventricle to the lungs. The pulmonary artery, the main blood vessel that runs between the right ventricle and the lungs, also might be malformed, and the right ventricle may be too small. These babies usually appear blue (cyanotic) after birth and need immediate specialized care.

Pulmonary Stenosis

In pulmonary stenosis, the pulmonic valve is stiffened and has a narrowed opening. It does not open properly, which may strain the heart because the right ventricle has to pump harder to send blood out to the lungs. If mild, pulmonary stenosis may never require any treatment.

Tetralogy of Fallot (TOF)

Tetralogy of Fallot is actually a combination of four heart defects: pulmonary stenosis; a thickened right ventricle (ventricular hypertrophy); a hole between the lower chambers (ventricular septal defect); and an aorta that can receive blood from both the left and right ventricles, instead of draining just the left. Because oxygen-poor (blue) blood can flow out to the body, children with this defect often appear bluish.

Total Anomalous Pulmonary Venous Connection

The pulmonary veins normally are the blood vessels that deliver oxygen-rich blood from the lungs to the left atrium. Sometimes these vessels don't join the left atrium during development. Instead they deliver blood to the heart by other pathways, which may be narrowed. Pressure builds up in this pathway and in the pulmonary veins, pushing fluid into the lungs, which decreases the amount of oxygen-rich blood that reaches the body. These infants often have trouble breathing and appear blue.

Transposition of the Great Arteries

In this condition, the pulmonary artery and the aorta (the major blood vessels leaving the heart) are switched so that the aorta arises from the right side of the heart and receives blue blood, which is sent right back out to the body without becoming oxygen-rich. The pulmonary artery arises from the left side of the heart, receives red blood and sends it back to the lungs again. As a result, babies with this condition often appear very blue and have low oxygen levels in the bloodstream. They usually come to medical attention within the first days after birth.

Tricuspid Atresia

Blood normally flows from the right atrium to the right ventricle through the tricuspid valve. In tricuspid atresia, the valve is replaced by a plate or membrane that does not open. The right ventricle therefore does not receive blood normally and is often small. Babies with this defect often appear bluish after birth and may need specialized care early in life.

Truncus Arteriosus

In an embryo, the aorta and the pulmonary artery are initially a single vessel. During normal development, that vessel splits to form the two major arteries, the aorta and the pulmonary artery. If that split does not happen, the child is born with a single common great blood vessel called the truncus arteriosus. There usually is a hole between the ventricles associated with this defect. The valve leading into the truncus arteriosus may be very abnormal.

Ventricular Septal Defect (VSD)

One of the most common congenital heart defects, VSD is a hole in the wall (septum) between the heart's left and right ventricles. These can happen in different areas and vary in size from very small to very large. Some of the smaller defects may gradually close on their own.

Signs and Symptoms of Heart Defects

Because congenital defects often compromise the heart's ability to pump blood and to deliver oxygen to the tissues of the body, they often produce telltale signs such as:

  • a bluish tinge or color (cyanosis) to the lips, tongue, and/or nailbeds
  • an increased rate of breathing or difficulty breathing
  • poor appetite or difficulty feeding (which may be associated with color change)
  • failure to thrive (weight loss or failure to gain weight)
  • abnormal heart murmur
  • sweating, especially during feedings
  • lowered strength of the baby's pulse

If you notice any of these signs in your baby or child, call your doctor right away. If your doctor notices these signs, you may be referred to a pediatric cardiologist.

Diagnosing a Heart Defect

Some congenital heart defects cause serious symptoms right at birth, requiring newborn intensive care in the hospital and immediate evaluation by a cardiologist. Other defects, like atrial septal defects, may go undiagnosed until the teen years — or even adulthood.

Newborns in the U.S. are screened at least 24 hours after birth to look for serious congenital heart disease that can lower oxygen levels. This screen is a simple, painless test using a machine called a pulse oximeter. The oximeter uses a sensor put on a baby's skin that estimates how much oxygen is in the baby's blood. This test can help spot heart problems early on so that they can be treated right away. The screening will find most serious heart defects, but some babies who test normal could still have heart disease, especially coarctation or other defects on the left side of the heart. 

If a congenital heart defect is suspected, your doctor will likely refer you to a pediatric cardiologist. After a complete physical examination, including evaluation of the baby's heart rate and blood pressure, the cardiologist will order an electrocardiogram (EKG). EKGs are performed by placing small pads (called leads) on the child's chest, which are wired to a monitor that records and prints out the electrical signals of the heart.

The cardiologist will often order an echocardiogram, which provides detailed images of the heart by using ultrasound. Specialized ultrasound waves can demonstrate all of the heart chambers and valves, the great arteries arising from the heart, and the direction and speed of blood flow in various areas of the heart. Echocardiograms also can evaluate whether the heart is squeezing and relaxing normally. Echocardiograms are the primary tool for diagnosing congenital heart defects.

A fetal echocardiogram is a specialized type of ultrasound that allows diagnosis of heart problems in utero. This can be done as early as 16–18 weeks into the pregnancy. These tests are ordered when an obstetrician suspects a heart abnormality on a level II ultrasound. They're also done if another close family member has a congenital heart defect or if the mother has a condition, such as diabetes, that might make a heart problem in the fetus more likely.

In some children, a chest X-ray is done to evaluate the size and shape of the heart. It can also help show the amount of blood the heart is pumping to the lungs.

Cardiac catheterization is sometimes done as well. In this procedure, a long, thin tube (a catheter) is threaded through blood vessels in the navel (in a newborn) or the groin and up into the heart. Once in place, the catheter can measure the oxygen levels and pressures within the heart's chambers. Dye may be injected through the catheter to better show the heart's inner structures and see the direction of blood flow through the heart.

Many congenital heart defects can be fixed in a cardiac catheterization. For instance, devices can close holes in the heart or open up tight valves or narrowed blood vessels.

A pediatric cardiologist is the doctor most qualified to diagnose a congenital heart defect and give treatment. This is true even before a baby is born. If you are an expectant parent and your baby has been diagnosed with a congenital heart defect via a fetal ultrasound, your obstetrician probably will have you see a pediatric cardiologist.

If You Suspect a Problem

If you think your child may have a congenital heart defect or you notice any signs (such as difficulty breathing or feeding, or blue lips or tongue) that concern you, call your doctor. In more urgent cases, such as if your baby suddenly turns very blue or loses consciousness, call 911.

More treatments than ever are available for congenital heart defects, and most defects are treated successfully. Children with heart disease are best cared for by a team of specialists, which will usually include:

  • pediatric cardiologists
  • pediatric heart surgeons
  • pediatric cardiac anesthesiologists
  • doctors specialized in the intensive care of children with heart disease and specialized nurses, nurse practitioners, physician assistants, and many others

Many children will benefit from having their hearts fixed surgically or through a cardiac catheterization procedure.

If you suspect that your child has a heart defect, the sooner you get medical attention, the better chance your child will have of making the fullest recovery possible.

With all the medical resources available, a congenital heart defect won't necessarily prevent a child from leading a normal life. By working with the health care team, you'll get the best care possible for your child.

Reviewed by: Gina Baffa, MD
Date reviewed: December 02, 2016