Pediatric Cardiology

Transposition of the Great Arteries (TGA): Symptoms, Diagnosis and Treatment

Posted on by Prof. Dr. İbrahim Cansaran TANIDIR

Transposition of the Great Arteries (TGA) is a cyanotic congenital heart disease in which the aorta and pulmonary artery emerging from the heart are switched, requiring urgent intervention from the very first moments of life. In this anatomical abnormality, oxygen-poor blood returning from the body re-enters the systemic circulation without passing through the lungs, while oxygenated blood from the lungs remains trapped within the circulation between the heart and lungs without reaching the body. This condition, which manifests as severe bluish discoloration during the neonatal period, is treated through surgical procedures that correct the abnormal vascular connections of the heart. Managed by pediatric cardiology specialists, the treatment process aims to restore the baby’s heart to normal function and ensure healthy development; rapid diagnosis is the most important factor directly affecting life expectancy and quality of life.

What Is Transposition of the Great Arteries (TGA)?

To understand this condition more clearly, we can imagine the circulatory system as two separate but interconnected journeys. In a healthy structure, blood continuously traces a “figure eight” between the body and lungs. In other words, oxygen-poor blood travels to the lungs, becomes oxygenated, returns to the heart, and is pumped back into the body. This is an integrated system that operates in series. In transposition of the great arteries, however, this interconnected structure disappears. As the vessels connect to the wrong chambers of the heart, circulation becomes two separate closed circuits that do not communicate with each other.

In the first circuit, oxygen-poor blood returning from the body to the right side of the heart is pumped directly back into the body through the incorrectly connected aorta. In this situation, the body’s tissues attempt to function with blood that lacks the oxygen they need. In the second circuit, oxygenated blood returning from the lungs to the left side of the heart is sent back to the lungs through the pulmonary artery connected to that side. In other words, oxygenated blood remains trapped between the heart and lungs and cannot reach the body. If there are no natural or medically created pathways allowing blood to mix between these two independent circulatory systems, oxygen deprivation in the body becomes inevitable.

How Does a Baby with Transposition of the Great Arteries (TGA) Survive in the Womb?

How a baby with such a challenging anatomical difference can develop in the mother’s womb is one of the most remarkable aspects of human physiology. While the baby is still in the womb, the lungs are not used for breathing; during this period, they remain unexpanded and filled with fluid. The oxygen required by the baby is supplied directly through the placenta connected to the mother. Oxygen-rich blood from the placenta enters the baby’s body through the umbilical cord.

During this period, the baby’s heart contains very special natural passageways, known as shunts, which are expected to close some time after birth. The first is a small opening between the right and left upper chambers of the heart called the foramen ovale. The second is a vascular bridge called the ductus arteriosus, which connects the pulmonary artery to the aorta. Thanks to these shortcuts, oxygenated blood arriving from the placenta can circulate freely between the baby’s heart chambers and major vessels. Since the lungs are not yet functioning for breathing and oxygenated blood comes directly from the mother, the reversed connections of the vessels generally do not adversely affect life in the womb. Through these natural connections, the baby receives the oxygen needed and continues developing until birth.

What Are the Types of Transposition of the Great Arteries (TGA)?

In medical evaluations, this anatomical condition is divided into different subgroups according to its relationship with the other structures of the heart. The main types of the disease are:

  • Classic transposition (TGA or BAT)
  • Congenitally corrected transposition (ccTGA)
  • Transposition with a ventricular septal defect (TGA+VSD)
  • Transposition with pulmonary outflow tract obstruction (TGA+LVOTO)
  • Transposition with aortic outflow tract obstruction (TGA+RVOTO)
  • Transposition with pulmonary outflow tract obstruction and a ventricular septal defect (TGA+VSD+LVOTO)
  • Transposition with pulmonary outflow tract obstruction and a ventricular septal defect (TGA+VSD+RVOTO)

Classic transposition is the most common type, in which the upper and lower chambers of the heart are connected correctly, but the major arteries are switched. In the rare type known as corrected transposition, nature appears to balance one error with another. In this condition, not only the vessels but also the lower chambers of the heart are reversed. This double reversal physiologically corrects the route that blood must follow through the body. Oxygen-poor blood travels to the lungs, while oxygenated blood reaches the body. Therefore, individuals with this type may continue their lives for a long time without noticeable symptoms; however, in later years, the heart muscle may struggle to bear this anatomical burden, and signs of fatigue may develop.

What Symptoms Are Seen in Babies with Transposition of the Great Arteries (TGA)?

When birth occurs and the baby’s umbilical cord is clamped, the oxygen supply from the mother ends. When the baby takes the first breath, the lungs fill with air, and blood begins flowing toward the lungs. Along with this change, the natural passageways that were lifesaving in the womb gradually begin to close. As these pathways close, the possibility of oxygenated and oxygen-poor blood mixing decreases. The main symptoms observed in these babies after birth include:

  • Bluish discoloration of the skin
  • Darkening of the lips
  • Bluish discoloration around the nail beds
  • Rapid breathing
  • Rapid fatigue during feeding
  • General restlessness
  • Increased heart rate

Although babies with this condition may not appear to be experiencing significant respiratory distress during the first hours, their skin color clearly indicates the lack of oxygen in their bodies. Depending on how quickly the natural connections close, this bluish discoloration may become much more pronounced within hours or days.

How Is Transposition of the Great Arteries (TGA) Diagnosed After Birth?

Although advances in technology have made it largely possible to diagnose the condition through ultrasound examinations performed during pregnancy, in some cases the findings may only be recognized after birth. Changes in skin color and persistently low blood oxygen levels provide the most important clues for physicians. Measurements obtained from devices that use light to measure oxygen levels through a fingertip or heel are considerably lower than those of a healthy newborn.

During the physical examination, listening to the heart may not reveal any obvious abnormal sounds in the first hours, so advanced imaging examinations are used. Chest X-rays may show a characteristic appearance resembling an egg hanging from a string within the chest cavity due to the unusual positioning of the heart and vessels. However, echocardiography is the most reliable method for confirming the diagnosis. By using sound waves to display the internal structure of the heart in real time, this method allows clear observation of which vessel originates from which chamber, the condition of the natural openings between the chambers, and the direction of blood flow.

Why Does Cyanosis Develop in Transposition of the Great Arteries (TGA)?

The underlying cause of bluish discoloration, medically known as cyanosis, is related to the condition of structures called hemoglobin, which are responsible for carrying oxygen in the blood. Hemoglobin can be thought of as small transport vehicles floating in the blood and delivering oxygen molecules to the organs. When these carriers are loaded with oxygen, they give blood a bright, vivid red color. When they lack oxygen, their color becomes darker and takes on a more bluish or purplish shade.

When the major arteries are switched, oxygen-poor blood returning from the body to the heart is pumped directly back into the body without passing through the lungs. Consequently, a very large proportion of circulating hemoglobin remains without oxygen, or “empty.” As the concentration of this oxygen-poor hemoglobin circulating in the body increases, the skin begins to take on a purple appearance. Increases in body temperature, changes in acid-base balance, and increased respiratory rate may also affect hemoglobin’s affinity for oxygen, periodically increasing the severity of cyanosis. When the body senses oxygen deprivation, it attempts to compensate by breathing faster, but because the blood vessels are connected incorrectly, this only results in greater exertion.

What Initial Interventions Are Performed for a Baby Diagnosed with Transposition of the Great Arteries (TGA)?

As soon as the diagnosis is established, a critical period begins in which time is of the essence. To maintain the baby’s vital signs at a safe level, it is necessary to prevent the closure of the bridging vessel that allows the blood to mix. This is where medication treatment comes into play. The main steps taken to stabilize the baby in an emergency include:

  • Establishing intravenous access
  • Prostaglandin infusion
  • Monitoring blood oxygen levels
  • Maintaining body temperature
  • Blood gas analysis

The medication called prostaglandin, administered intravenously, sends relaxation signals to the bridging vessel that has begun to constrict and close. Under the influence of this medication, the vessel reopens, restoring the vital connection between the pulmonary and systemic circulations. As oxygenated and oxygen-poor blood begin to pass between the circulations through this vessel and mix, the amount of oxygen reaching the body gradually increases, providing support to the baby’s organs.

How Is Balloon Atrial Septostomy Performed in the Treatment of Transposition of the Great Arteries (TGA)?

When medication treatment alone is insufficient, meaning blood cannot mix adequately because the natural opening between the heart’s upper chambers is too narrow, a more mechanical approach is required. The procedure performed at this critical stage represents a major step toward improving the baby’s circulation. Usually, a very thin, flexible tube with a deflated balloon at its tip is advanced toward the heart through a vein in the groin region or umbilical cord.

With the assistance of an echocardiography device, this tube is advanced into the right atrium and then passed through the opening between the atria into the left atrium. Once inside the left atrium, the balloon is inflated with fluid. The physician performing the procedure then pulls the inflated balloon back toward the right atrium with a rapid and controlled movement. This pulling motion creates a large tear in the thin membrane between the two atria. As a result, the previously restricted area where blood can mix inside the heart suddenly becomes wider. Oxygenated blood on the left side passes into the right side in a large volume, rapidly increasing the oxygen level of the blood that will be pumped into the body. After the procedure, the baby’s bluish skin color can be observed beginning to turn pink within minutes.

What Are the Surgical Solutions for Transposition of the Great Arteries (TGA)?

The balance achieved through medications or the balloon procedure does not represent the final steps that resolve the underlying problem; these are merely bridges that provide time for the definitive treatment, which is surgery. The main objective of treatment is to restore the heart to its natural structure by switching the positions of the vessels emerging from the wrong locations. This operation, known in medical literature as the arterial switch operation (ASO or Jatene procedure), requires extraordinarily delicate surgical precision. Not only are the aorta and pulmonary artery switched, but the main challenge is also transferring the coronary vessels that supply the heart muscle itself, which are only a few millimeters in diameter, to their new positions, namely the new aorta, with millimeter-level precision.

One of the most important factors determining the success of this surgical intervention is timing. The heart’s left ventricle is capable of pumping blood against high pressure while the baby is in the womb. However, in this disease, because the left ventricle is connected to the low-pressure pulmonary circulation after birth, it begins to lose muscle strength with each passing day. The aim is generally to perform surgery within the first fifteen days of life, before this muscle becomes deconditioned and loses its strength. Following these early operations, the left ventricle rapidly adapts to its new function.

How Is the Heart Prepared for Surgery in Delayed Cases of Transposition of the Great Arteries (TGA)?

If the baby has passed the first weeks of life due to delays in diagnosis, the left ventricle may have lost a significant portion of its ability to work against high pressure. In such a situation, directly switching the major arteries resembles asking an unprepared muscle to suddenly lift a very heavy weight and may lead to heart failure. Therefore, a special muscle-strengthening program is initiated to prepare the heart for the main surgery. The preparatory steps include:

  • Echocardiographic monitoring of heart muscle contraction
  • Determination of heart muscle mass using MRI
  • Hemodynamic evaluation through angiography

And subsequently:

  • Pulmonary artery banding
  • Increasing left ventricular pressure
  • Shunt operations
  • Stent placement in the PDA
  • Balloon atrial septostomy

After the procedure most appropriate for the patient has been performed, the second stage of surgery can be planned.

A band placed around the pulmonary artery narrows the vessel. This narrowing causes the left ventricle to encounter resistance while pumping blood. As the ventricle works against this resistance, it increases its muscle mass and thickens, just like an athlete undergoing training. After this training period, which may last several months, the muscle structure is reassessed using echocardiography. When the left ventricle reaches sufficient thickness, the main major operation can be performed safely.

Can Transposition of the Great Arteries (TGA) Surgery Be Performed on Babies with Low Birth Weight?

Although performing such extensive surgery on premature or low-weight babies whose development is not yet complete caused serious hesitation in previous years, the situation has changed considerably today. Babies with low birth weight have more delicate tissues and more limited organ capacities. Nevertheless, technological innovations and the adaptation of heart-lung machines to these tiny bodies have made it possible to offer these babies a surgical opportunity as well.

The miniaturization of surgical equipment, the reduction of suture materials to sizes that are difficult to see with the naked eye, and improvements in intensive care standards have made this process easier to manage. In experienced centers, procedures are performed using anesthesia and perfusion protocols specifically prepared according to each baby’s weight and physical resilience. During surgery, body temperature is gradually lowered in a highly controlled manner to reduce the tissues’ oxygen requirements. Through delicate surgical techniques and careful postoperative care, the goal is for babies with low birth weight to recover their health just as babies with standard birth weights do.

How Does the Intensive Care Process Progress After Transposition of the Great Arteries (TGA) Surgery?

Following the demanding surgical procedure, a period of very close monitoring is necessary for the heart and body to adapt to the newly established circulatory system. Every vital function of the baby transferred from the operating room to the intensive care unit is monitored continuously through sensitive devices. The main methods used to monitor the baby’s vital signs in intensive care include:

  • Ventilator monitoring
  • Blood pressure monitoring
  • Heart rhythm monitoring
  • Urine output monitoring
  • Chest tube drainage
  • Inotropic medication support

During the first few days, the heart muscle that has assumed its new function may become fatigued. During this adaptation period, special medications are administered intravenously to support the heart’s contractile strength. At the same time, the ventilator reduces the burden on the heart and helps the baby remain comfortable. As the days pass, if echocardiography examinations show improved heart performance, medication support is gradually reduced. When the baby begins breathing independently, ventilator support is discontinued, and normal feeding stages are initiated.

What Can Children Who Have Undergone Treatment for Transposition of the Great Arteries (TGA) Expect in the Long Term?

Most children who have successfully completed surgery and intensive care can lead active, energetic lives in later years, indistinguishable from those of their peers. Their motor development, cognitive processes, and adjustment to school generally follow a normal course. Children who achieve the desired level of recovery can participate in sporting activities and comfortably adapt to all aspects of daily life.

However, even after this structural abnormality has been corrected, the heart’s development during growth must always remain under observation. For the heart to maintain its function over time, the newly established vascular connections must adapt to the body’s rate of growth. Long-term follow-up may reveal certain structural remodeling and volumetric adaptations in the left ventricles of these children compared with healthy peers. Heart tissue may undergo small structural changes to function as effectively as possible within the newly established system. This generally does not indicate disease, but periodic evaluation of the heart’s new structure is essential.

What Late Complications May Occur During Follow-Up for Transposition of the Great Arteries (TGA)?

Although the aim is lifelong well-being following surgery, certain changes may develop in the heart tissue and blood vessels over the years due to physical growth. Therefore, regular cardiological follow-up is extremely important. Possible medical conditions that may be encountered during long-term monitoring include:

  • Aortic valve stenosis or insufficiency
  • Pulmonary artery stenosis or insufficiency
  • Coronary artery problems
  • Rhythm disorders
  • Heart muscle fatigue

In particular, the aortic valve that was relocated and assigned its new function during surgery may stretch over time because it is exposed to high systemic pressure for years, potentially causing mild backward leakage of blood. In most cases, these leaks remain mild and do not affect daily life. Similarly, narrowing may develop in the pulmonary artery due to tension resulting from the surgical maneuvers performed during the operation. When such narrowing is detected, dilation is generally performed using a balloon or stent through angiographic methods without requiring open surgery. Early detection of possible rhythm changes and valve problems, followed by their management through preventive medical approaches, helps individuals lead safe lives.

Güncellenme Tarihi: 13.10.2026

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