Introduction

Truncus arteriosus, abbreviated to TA, is a congenital heart defect, which means it is present from birth. TA occurs when there is only one main blood vessel instead of two. Therefore, meaning that the deoxygenated blood coming back from and the oxygenated blood leaving the heart are combined.¹ Although TA itself is a rare defect, it can be fatal if left untreated, hence the need for surgical intervention. Surgical intervention is needed to separate the blood flow from the lungs from the blood flow to the body to prevent any circulatory issues, as well as high blood pressure.^1,2

This article aims to give you an overview of truncus arteriosus as well as the surgical procedures used to treat it. 

Overview of truncus arteriosus

As previously stated, truncus arteriosus (TA) is a congenital heart condition, which there is only one main blood vessel. This arises as the aorta (responsible for carrying oxygenated blood to the body) and pulmonary artery (responsible for carrying deoxygenated blood to the lungs) do not separate during fetal development. This part is commonly referred to as a trunk. TA commonly occurs alongside another congenital heart defect known as a ventricular septal defect (VSD). VSD is when there is a hole in the wall between the left and right ventricles (lower part of the heart chamber).¹ 

There are four different types of TA. These are: 

• Type one: This is where the left and right pulmonary arteries branch off the main pulmonary artery after separating from the common trunk. This is the most common type of TA
• Type two: This is where the left and right pulmonary artery branch off from different sites, but they branch off the common trunk
• Type three: This is where the left and right pulmonary arteries arise opposite from each other
• Type four: This is where the pulmonary artery branches off the descending aorta (the part of the aorta that moves downward). Although this is no longer considered a type of TA, it is still worth noting^1,3,4

Due to this, those with truncus arteriosus have a high amount of blood flow into the lungs, making the heart work harder. This, therefore, means that the body gets an inadequate amount of oxygen due to it being mixed. This may result in symptoms such as: 

• Cyanosis - this is characterised by having blue-tinged lips, nails and/or skin
• Extreme fatigue
• A heart murmur or pounding heart
• Breathing problems 
• A weak pulse
• Feeding difficulty 
• Difficulty gaining weight¹

The diagnosis of truncus arteriosus can occur during pregnancy or after birth. If done before birth, TA can be diagnosed via a prenatal ultrasound, which creates images of the baby. If it's suspected, then a fetal echocardiogram may be carried out to produce a more detailed image of the baby's heart.  However, if symptoms are noticed after birth, clinicians could carry out an echocardiogram (ultrasound of the heart) to confirm the diagnosis.⁵ Due to the symptoms faced, infants may need some medications to aid in strengthening the heart, lowering their blood pressure, as well as reducing any excess fluid buildup. They may also be put on a high-calorie diet in order to have a healthy weight gain due to many having feeding difficulty. Eventually,  surgery is needed in order to repair the heart and blood vessels.⁵ 

The most common surgery method is known as the Rastelli repair; however, there are also others.⁶ These approaches shall be discussed next. 

The rastelli procedure 

The Rastelli procedure is a type of open-heart surgery carried out in infancy. The procedure involves using a synthetic patch to close the VSD so that blood flow and circulation are improved. The surgeon then adds a conduit (an artificial tube) with a valve to connect the right ventricle to the arteries, allowing for deoxygenated blood to flow to the lungs. If the tube is artificial, it is usually made of Dacron, which is a synthetic polyester with a valve taken from a pig. However, it can also be a homograft made from a donated human valve and artery. The single blood vessel that is already present will be used to create the aorta to allow for oxygenated blood to flow to the rest of the body.^{5, 6, 7, 8}

The procedure is largely successful as it can improve the lifestyle of the child, although it varies from patient to patient; there may be limitations in the amount of exercise the child can do. It is also worth mentioning that, as the child grows, another surgery will likely be needed to replace the conduit, as it may wear out over time.⁹

Other treatments

Modified van praagh repair

This treatment method is a variation of the Rastelli procedure based upon the specific anatomy of the truncus arteriosus, named after Dr. Van Praagh. Van Praagh is a different type of classification used to describe the features of truncus arteriosus.¹⁰ The modified Van Praagh classification of truncus arteriosus is broken down into 3 main categories: 

• Truncus arteriosus that has pulmonary arteries that are either fully or nearly connected
• Truncus arteriosus without one pulmonary artery
• Truncus arteriosus with an interrupted (not fully formed) aortic arch¹¹

The surgery is then conducted in accordance with these distinguishable features. It is mainly used in cases with an interrupted aortic arch where a graft is placed to join the gap between the interrupted segments, allowing for improved blood flow.¹²

Conduit-free techniques

Due to conduits needing replacement as you age, there has been increased research into finding conduit-free techniques. A technique proposed by Barbero-Marcial, where a conduit was not used and instead the pulmonary arteries were reconstructed in patients.¹³ In 2021, a study using the surgery originally conducted by Barbero-Marcial in the 90s was done on 5 patients with a low birth weight. Although this procedure comes with its limitations and complications, follow-ups in 3 patients showed that they had good heart function postoperatively. This is a novel approach as it reduces infection risk and allows for the chance for it to grow with the child.¹⁴

Hybrid approaches

To reduce the invasive nature of the surgery needed for truncus arteriosus, future surgeries that may be required take on a hybrid approach. This can be done through the use of a catheter, where the clinician places a catheter in a blood vessel in the groin, which takes it towards the heart. They can then place a new valve through this route. If there is a blockage in the artery, the catheter may have a balloon at the end, which can be guided to the blockage and inflated at the blockage site. This, therefore, makes the artery wider, allowing for blood to flow more easily, restoring function.¹⁵

Post-surgical considerations

While surgical repair of truncus arteriosus significantly improves survival and quality of life, it is not without long-term challenges. Some post-surgical considerations include potential complications and the need for long-term follow-up care. 

As mentioned previously, as the conduit doesn’t grow with the child, they would need repeat surgery to replace or amend the valve/pulmonary artery. They may also need occasional cardiac catheterisations to look inside the heart to assess the structure and function of the heart. It is also worth mentioning that those with truncus arteriosus are at a higher risk of developing endocarditis (a bacterial heart infection). Hence, the a potential need to have a course of antibiotics before any surgery or before visiting the dentist.^2,6 Furthermore, those who have had a repair have a higher risk of developing an arrhythmia. Due to these factors, long-term follow-up is required, which may include having follow-up tests, including electrocardiograms (measures the electrical activity of the heart), echocardiogram (creates an image of the heart as it is moving) and conducting exercise stress tests.²

Conclusion

Truncus arteriosus (TA) is a rare but serious congenital heart defect. It occurs when there is only one blood vessel instead of two, impacting blood flow and pressure. Therefore, surgery is required to repair the heart and separate the blood vessels. The main surgical method is the Rastelli procedure, but there have since been some advances in surgical approaches, such as the modified Van Praagh repair and conduit-free techniques. All in all, these methods have improved outcomes for patients with truncus arteriosus. However, this also comes with lifelong follow-up care to address any potential complications that may arise. As medical technology continues to advance, there is hope for even less invasive and more durable solutions that improve both the longevity and quality of life for individuals with truncus arteriosus. For example, there has been research into using a partial heart transplant to treat TA through the use of three-dimensional printed heart models, which shows some promise.¹⁶

FAQs

What is truncus arteriosus? 

Truncus arteriosus is a congenital heart condition that occurs when there is one blood vessel instead of two (these being the aorta and pulmonary artery). This, therefore, means that the deoxygenated blood coming back to the heart and the oxygenated blood leaving the heart are mixed, hindering the amount of oxygenated blood reaching the rest of the body.¹

What are the symptoms of truncus arteriosus?

There are a few symptoms associated with truncus arteriosus. These are cyanosis which is characterised by having blue-tinged lips, nails and/or skin (due to the lack of oxygenated blood), extreme fatigue, having a heart murmur or pounding heart, difficulty in breathing, having a weak pulse, having a difficulty in feeding infants and as a result a not gaining weight.¹

What are the treatment options?

Some infants may be given medication to help with the symptoms of truncus arteriosus, but the main treatment method is surgery. This could be done using the Rastelli procedure, which uses a conduit (artificial valve and pulmonary artery) to repair the heart.^6,7