Within the second half of the 20th century, there have been massive advancements in the medical and surgical procedures offered to patients, enabling many patients to survive many previously thought “incurable” illnesses. With this in mind, a growing population of adults have undergone successful surgical procedures as infants or young children. 

One of these surgical procedures includes truncus arteriosus repair, which is the focus of this article. However, despite a successful truncus arteriosus repair in childhood, long-term complications can arise in adulthood, which can include: conduit failure, truncal valve regurgitation, arrhythmias, heart failure, and more issues that can lead to reduced quality of life and, in some cases, life-threatening conditions. However, there may be many management strategies for these long-term complications that may help alleviate these complications. 

Understanding Truncus Arteriosus

Truncus arteriosus (TA) is a congenital heart disorder (CHD) which presents with a significantly impairing structural malformation at birth.¹ This is a rare and severe condition necessitating surgery, as survival beyond infancy is unlikely without it.²  

Truncus Arteriosus is characterised by the presence of a single arterial trunk that fails to separate and branch into the typical two systemic and pulmonary circulatory branches during early embryonic development.³ This condition is typically accompanied by a ventricular septal defect (VSD), which is a hole in the septum (the muscular wall dividing the heart’s left and right ventricles).⁴ This VSD results in the mixing of deoxygenated and oxygenated blood, reducing the efficiency of oxygen delivery. 

Anatomical Features and Classification 

Truncus arteriosus is classified into several types based on the branching patterns of the pulmonary arteries (which supply blood to the lungs) from the common arterial trunk. The normal branching pattern involves the pulmonary trunk branching off the heart and then dividing into the right and left pulmonary arteries, delivering blood to each lung. Simultaneously, the aorta exits the heart separately to deliver oxygen-rich blood to the rest of the body. However, in truncus arteriosus, the aorta and the pulmonary arteries do not separate properly, leading to anatomical differences in how the aorta and pulmonary arteries leave the heart. 

The commonly used Collett and Edwards classification divides truncus arteriosus into four types, based on the splitting of the pulmonary arteries from the common trunk:^4,5

• Type I: The most common form, where a single main pulmonary artery arises from the common trunk (with both the aorta and the pulmonary arteries) and then divides into the left and right pulmonary arteries.
• Type II: The left and right pulmonary arteries both branch off directly from the common trunk 
• Type III: The pulmonary arteries arise separately and from widely spaced locations on the lateral aspects of the truncus. One pulmonary artery branches off the common trunk, and the other branches off the aorta. 
• Type IV (now considered part of pulmonary atresia with VSD): No pulmonary arteries arise from the common trunk to supply the lungs, with blood flow to the lungs instead supplied by collateral vessels.

Surgical Repair of Truncus Arteriosus 

As previously mentioned, truncus arteriosus is a serious condition and therefore necessitates surgical intervention to correct the improper separation of the pulmonary arteries from the aorta. This surgery usually occurs in the first few weeks of life, however, the baby may need special treatments for a few weeks until they are ready for the rigours of surgery. Some of these pre-operative interventions may include taking:⁴

• Medication: To help the heart pump more effectively
• Nutritional Therapy: To enable weight gain for surgical readiness 
• Tube feeding: To ensure adequate nutrition

There are various types of truncus arteriosus, as delineated previously by Collett and Edwards, hence, it follows that there are several different types of surgical approaches, each varying based on the specific branching pattern of the pulmonary arteries and aorta. However, the usual surgical procedure for truncus arteriosus repair typically involves the following key steps:^1,4,6

• Separation of the Pulmonary Arteries from the Aorta
• Repairing the common trunk by reconstructing it using an existing blood vessel to make a functional aorta 
• Closing the ventricular septal defect (VSD) using a patch to close the hole in the septum
• Reconstruction of the pulmonary artery and valve using an artificial tube and valves (homograft or conduits), hence connecting the pulmonary arteries to the right ventricle

Through truncus arteriosus repair, the aim is to restore normal blood flow to the body as well as the lungs, through improving the flow of blood out of the heart by increasing the delivery of an oxygen-rich supply. 

Long-Term Complications of Truncus Arteriosus

Post-surgery, patients with truncus arteriosus repair typically require regular follow-up and consultations with a cardiologist (a heart doctor). These consultations typically continue until adulthood, where the cardiologist may use many tests, all to ensure early detection of long-term complications and to ensure optimal heart functioning. Some of these diagnostic tests can include:⁷

• Electrocardiograms (ECG): To detect arrhythmias or conduction abnormalities
• Echocardiograms: To assess heart structure, valve function, and overall performance
• Holter Monitors: For continuous rhythm monitoring over 24–48 hours
• Exercise Stress Tests: To evaluate the heart’s response to physical activity

In accordance with the test results, some patients may require medication or additional procedures.

The long-term survival rate of truncus arteriosus is approximately 70-90% when the patient is 30 years old, with the majority of surgical deaths occurring immediately in the short-term after surgery, while long-term complications become a significant concern for survivors.^8,9 

Among these, one of the most significant predictors of long-term complications is truncal valve regurgitation.^9,10 This condition involves a leakage of the truncal valve, which separates the heart and blood vessels, allowing blood to flow backwards into the heart instead of moving forward into the lungs or body. Truncal valve regurgitation often leads to additional surgeries and contributes to the patient’s risk of heart failure and other complications over time. 

​​Additionally, the patient may have slightly reduced exercise tolerance due to impaired heart function. This is quite common, especially in long-term survivors of truncus arteriosus.⁹ However, this can be managed using an individualised exercise program, keeping in mind their abilities, and the patient should self-limit and prevent exhaustion.¹¹

Another long-term concern for patients is the higher risk of developing subacute bacterial endocarditis (SBE), a serious bacterial illness caused by the infection of the inner lining of the heart and heart valves. To reduce this risk, patients are advised to take preventive antibiotics, such as amoxicillin or azithromycin, before undergoing dental or respiratory procedures.^11,12,13 This practice, known as SBE prophylaxis, plays a key role in preventing serious complications.

Despite successful initial surgeries, most truncus arteriosus patients will require additional surgical procedures throughout childhood and adulthood, known as reinterventions, as they age. These are necessitated by several factors, including:

• Homograft Degradation: The tissue graft (homograft) used to reconstruct the pulmonary artery tends to deteriorate over time due to calcification or structural failure. Homograft replacements are common, with most patients requiring their first replacement 10–12 years after the initial surgery. Despite this, homografts were found to be durable and performed well overall for patients.^13,14
• Conduit Dysfunction: The pulmonary conduit used during the initial repair does not grow with the patient, leading to stenosis (narrowing), calcification, or structural degeneration. 
• Valve Leaks or Blockages: Leakage or narrowing of the valves can impair heart function, requiring repair or replacement through surgery or via catheter-based techniques.
• Growth-Related Needs: As the child grows, the initial repairs, including valves, conduits, or grafts, may no longer fit their anatomy and require adjustment. Interestingly, studies have shown that patients with larger valve replacements tend to go longer between surgeries compared to those with smaller valves.⁹

Reinterventional procedures may include replacing homografts, conduits, or truncal valves.⁹ In some cases, catheter-based techniques may suffice, avoiding the need for invasive surgery.

Some more common long-term complications affecting their daily life reported by patients include:⁴

• Dizziness: Resulting from irregular blood flow or arrhythmia
• Heart rhythm abnormalities (arrhythmia): Irregular heartbeat requiring monitoring⁴
• Heart Failure: Inadequate blood supply can lead to fatigue, reduced oxygen levels, and increased strain on the heart⁴
• Conduction abnormalities: Issues with propagating the electrical signal within the heart, disrupting the rhythmic contraction of the heart
• Shortness of Breath: Fluid buildup in the lungs and reduced oxygen levels can make breathing difficult
• Heart Muscle Weakness: Over time, the heart may weaken, impacting its ability to pump effectively.
• Pulmonary Hypertension: High blood pressure in the lungs, as the blood vessels in the lungs narrow to compensate, making it harder for the heart to pump blood into the lungs
• Heart Enlargement: Increased strain on the heart may cause the heart to get larger to compensate for the heart needing to work harder to pump blood 
• Eisenmenger Syndrome: Permanent lung vessel damage resulting in a significant lack of blood flow to the lungs¹⁵
• Swelling of Belly, Lungs and Feet (Oedema): Fluid buildup in the belly, lungs, or feet is a common symptom of heart failure¹⁵

Summary

Truncus arteriosus repair involves post-operative care, which may require long-term management and consultations with a cardiologist to ensure early detection of long-term complications. Whilst surgical interventions and advancements have improved the survival rate significantly, challenges such as valve durability or calcification may necessitate reintervention. Furthermore, several potential lifestyle complications may ensue, such as dizziness, shortness of breath or heart enlargement, and truncus arteriosus repair may also increase the risk of some bacterial infections. 

Through regular cardiology consultations and adhering to prescribed treatments, patients can continue to lead fulfilling lives despite the challenges associated with this truncus arteriosus repair.