Dextro-transposition, or d-transposition, of the great arteries is a life-threatening heart birth defect that arises when the two “great” (or main) arteries within the heart are switched, or transposed, so that each one carries blood to the wrong location. This severely limits the heart’s ability to provide the body with oxygen-rich blood.

In a normal heart, one of two great arteries, known as the main pulmonary artery, brings oxygen-poor blood (blood that’s low in oxygen) to the lungs, where it becomes oxygenated (oxygen-rich). Another great artery, the aorta, carries oxygen-rich blood from the heart to the rest of the body.

In an individual with d-transposition of the great arteries, the placement of the arteries is reversed, so that oxygen-poor blood, which should go through the main pulmonary artery to pick up oxygen, goes through the aorta instead. Similarly, oxygen-rich blood that is supposed to travel through the aorta instead enters the main pulmonary artery.

About 1,200 babies in the United States are born with d-transposition of the great arteries each year, accounting for about 3% of all congenital heart conditions.

Babies born with this condition are typically diagnosed before birth, during an ultrasound in mid-pregnancy to assess fetal cardiac anatomy. This diagnosis can also occur within the first hours or days of life if a baby’s skin appears bluish and they have difficulty breathing and/or feeding, among other signs that they aren’t getting the oxygen that they need.

Babies with d-transposition of the great arteries require surgery within the first weeks of life so that oxygen-rich blood can be delivered to the body. Without treatment, most patients will not survive beyond a year. Most patients who undergo surgery as infants live into adulthood.

D-transposition of the great arteries is a congenital (present at birth) heart condition that interferes with blood flow through the heart in the expected fashion because the heart’s two great arteries—the main pulmonary artery and the aorta—are transposed, or switched. This prohibits oxygen-poor blood from getting to the lung and oxygen-rich blood from getting to the body.

This transposition creates two unhelpful loops, with the baby’s oxygen-rich blood remaining within the left half of the heart and lungs, and the baby’s oxygen-poor blood bypassing the lungs and being circulated from the right half of the heart throughout the body.

A baby born with d-transposition of the great arteries may also have some common associated heart defects. These include a ventricular septal defect or VSD (a hole in the heart wall that separates the ventricles) or an atrial septal defect or ASD (a hole in the wall between the atria). Such a hole allows oxygen-rich and oxygen-poor blood to mix slightly, which enables some oxygenated blood to get to the aorta and therefore to the rest of the body.

Oxygen may also reach the aorta through the ductus arteriosus. This is a special blood vessel in a fetus that connects the main pulmonary artery to the aorta. It typically closes spontaneously within the first few days of life after a baby is born because it is no longer needed. In a baby with d-transposition of the great arteries, this blood vessel may help oxygen-rich blood reach the aorta, where it will then travel to the rest of the body. Medication can be given to newborns to help keep the ductus arteriosus open until the condition can be surgically corrected.

Doctors aren’t sure what causes d-transposition of the great arteries. There are some rare genes associated with this condition, which are still being investigated by researchers. But as far as scientists know, the condition doesn’t run in families. If a baby’s mother has uncontrolled diabetes during pregnancy, it may increase the risk of d-transposition of the great arteries or other forms of congenital heart disease.

Newborns experience the following signs and symptoms within the first days of life, including:

• Bluish skin
• Difficulty breathing
• Poor feeding habits
• A pounding heart
• A weak pulse

D-transposition of the great arteries is often discovered during pregnancy with a routine ultrasound, then confirmed with a fetal echocardiogram (an ultrasound of the heart), but the condition is sometimes found in newborns. Doctors can diagnose d-transposition of the great arteries after learning about the newborn’s medical history, performing a physical exam, and giving diagnostic tests.

When learning about a newborn’s medical history, doctors may ask if the baby was diagnosed with a genetic or chromosomal abnormality, or if there is a family history of congenital heart disease. The answers to these questions may help doctors determine that the newborn may have a different type of congenital heart disease, rather than d-transposition of the great arteries.

During a physical exam, doctors will look at the newborn’s bluish skin, note their breathing difficulties, and listen to their heart with a stethoscope. They may give supplemental oxygen to see if that improves the baby’s condition. (If a patient has d-transposition of the great arteries, oxygen won’t help reduce the bluish appearance of the skin because oxygen in the lungs is unable to reach the blood circulating throughout the body.)

Doctors who suspect d-transposition of the great arteries should offer diagnostic tests, such as:

• Pulse oximetry, which measures an individual’s blood-oxygen levels. Doctors attach a pulse oximeter to a baby’s hand and/or foot to detect the amount of oxygen in the blood. Babies with d-transposition of the great arteries will have low blood oxygen levels.
• Echocardiogram (or “echo”), which uses sound waves to create images of the heart. A sonographer (a person trained in performing ultrasounds) places a transducer (or wand) on the patient’s chest and torso to create images of the heart. If a patient has d-transposition of the great arteries, this diagnostic test will show that the main pulmonary artery and the aorta are connected to the wrong ventricles and that blood is flowing through the heart abnormally. The ultrasound can also detect a hole in the heart (a ventricular or atrial septal defect) or a patent ductus arteriosus.
• Chest X-ray, which shows the shape and location of the heart. On an X-ray, the heart may look like an egg on a string if a patient has d-transposition of the great arteries.
• Electrocardiogram (ECG or EKG), which measures the heart’s electrical activity. Doctors place sensors on a patient’s chest and torso to get readings from the heart.

Newborns with d-transposition of the great arteries require surgery and usually receive it during the first few weeks of life. Some patients need other interventions before they are ready for surgery. They may receive:

• E1 prostaglandin, a medication that helps keep the ductus arteriosus from closing. This opening may help provide oxygen-rich blood to the body
• Balloon atrial septostomy, a minimally invasive procedure that widens an ASD. Doctors make a small incision in a blood vessel in the baby’s groin and then insert a thin, flexible catheter (tube) with a deflated balloon at its tip. Under ultrasound guidance, the doctors thread the catheter through the blood vessels and into the heart. When they are at the ASD, doctors inflate the balloon to widen the opening. Afterward, they deflate the balloon and remove it from the body. The newly widened opening lets more oxygen-poor and oxygen-rich blood mix, thereby increasing the amount of oxygen-rich blood that travels throughout the body.

When a patient is ready for surgery, they may have one of the following procedures:

• Arterial switch. This is the most commonly performed procedure for d-transposition of the great arteries. Surgeons reroute the patient’s great arteries to connect to their intended locations. They detach them from their current locations and reattach them to the correct ventricles, so that blood traveling through the right ventricle will go to the main pulmonary artery and blood traveling through the left ventricle will go to the aorta. The coronary arteries, which are smaller arteries bringing oxygen-rich blood to the heart muscle, also need to be relocated during surgery. Surgeons also patch any existing hole in the heart (a ventricular or atrial septal defect).
• Atrial switch. For this procedure, doctors leave the patient’s arteries in place. They instead create a tunnel, known as a baffle, between the atria, directing oxygen-rich blood toward the right ventricle so that it enters the aorta. This also helps direct oxygen-poor blood toward the left ventricle and the main pulmonary artery, where it becomes oxygenated. This procedure is less ideal because it makes the right ventricle work harder, which may cause complications over time. This is typically only performed in an older patient if there is a reason they cannot undergo the arterial switch operation.

Without surgical intervention, 90% of babies born with d-transposition of the great arteries will die during their first year of life; half will die within the first month. With surgery, over 95% of patients will live into adulthood

Patients born with d-transposition of the great arteries will need to see a cardiologist for the rest of their lives to monitor their heart health. They may develop complications or need follow-up surgery in the future.

Patients who have an atrial switch procedure are at increased risk of congestive heart failure during adulthood because the procedure makes the right ventricle work harder than it should.

Some patients with d-transposition of the great arteries develop arrhythmias (heart rhythm problems) over time. This is less of a risk in patients with the arterial switch procedure compared to those with an atrial switch procedure. Other patients may develop leaky heart valves, or their great arteries may become narrowed over time, requiring additional intervention.

”Yale Medicine programs care for patients with d-transposition of the great arteries from the time of diagnosis through the rest of their lives,” says Yale Medicine pediatric cardiologist Dina Ferdman, MD. “Physicians at the Yale Fetal Care Center collaborate to provide comprehensive care at the time of diagnosis, which often occurs halfway during pregnancy. After birth, there is a seamless transition to care for the infant within the Yale Congenital Heart Program, which works with our colleagues in Neonatology, Pediatric Intensive Care, and Pediatric Cardiothoracic Surgery.

Care is lifelong, and our Yale Adult Congenital Heart Center program is a referral center for patients transitioning out of pediatric care into adulthood, she adds. “We get to know the families from very early on, and it is a privilege to be part of their lives, from diagnosis through surgery and growing up,” she says.

This article was medically reviewed by Dina Ferdman, MD, a Yale Medicine pediatric cardiologist, and Prinston Varghese, MD, a clinical fellow at Yale.