Truncus arteriosus is a complex congenital heart defect involving a common channel for the LVOT and RVOT. The cases below show a parasternal long axis with a common outflow tract in 2D and in colour for the ventricular output. More information on truncus arteriosus here.

Truncus arteriosus, often considered a conotruncal cardiopathy par excellence (think of DiGeorge syndrome), represents a severe form of congenital heart disease that stems from anomalies in the development of the conotruncal region of the heart. These cardiopathies, including truncus arteriosus, are fundamentally linked to a defect in the migration of neural crest cells. In the spectrum of conotruncal malformations, truncus arteriosus sits at the most severe end, characterized by the complete absence of separate great arteries. 

Definition and Anatomical Characteristics 

Truncus arteriosus is defined by the presence of: 

• An obligatory ventricular septal defect (VSD) in the outflow tract.

• A single arterial valve. This valve is frequently tricuspid or quadricuspid - but can be bicuspid or unicuspid (very rare).

• A single common vessel (trunk) that overrides the VSD and is the sole arterial outlet from the heart. This common trunk gives rise in that specific order to: 

  1. the coronary arteries, 

  2. the pulmonary arteries, and 

  3. the systemic vessels.

• A lack of conus muscle (infundibulum) beneath the common valve.

The common valve typically overrides the VSD, connecting to both ventricles. A right aortic arch is frequently observed. 

Embryological Origin 

The underlying cause of truncus arteriosus, like other conotruncal defects, is a failure in the migration of neural crest cells, which are crucial for the septation of the great arteries and the formation of the outflow tracts. This developmental arrest results in a single, unseparated outflow vessel from the heart.

Frequency and Physiology 

Truncus arteriosus accounts for approximately 2% of all congenital heart defects. Physiologically, it produces a left-to-right shunt through a pulmonary “steal” effect, leading to pulmonary overcirculation. Clinical features include bounding pulses and rapid progression toward fixed pulmonary vascular resistance if untreated. Early surgical repair is required. 

Prognostic Considerations 

The prognosis is strongly influenced by the truncal valve, which functions as the systemic valve. The truncal valve may have 1 to 6 cusps and can be stenotic, regurgitant, or both, with valve dysfunction significantly affecting outcomes. 

Pathophysiology 

As pulmonary vascular resistance falls after birth, pulmonary overcirculation develops, causing vascular congestion, pulmonary edema, tachypnea, and increased work of breathing. Chest radiographs often show congestion. Progressive diastolic steal from the systemic circulation can lead to end-organ ischemia and poor perfusion. These infants are at increased risk of necrotizing enterocolitis (NEC). Oxygen saturation may be normal or only mildly reduced, as mixing occurs in a common arterial trunk. Despite systemic desaturation, the marked left-to-right shunt (high Qp:Qs) can mask hypoxemia. A saturation of 90% represents often a Qp:Qs of about 3:1.  The main preoperative risks include: Coronary steal, due to systemic runoff into the pulmonary circulation at due to truncal valve insufficiency. Systemic hypoperfusion, contributing to mesenteric ischemia and increased risk of NEC, as well as fixation of the PVR.

Clinical Examination 

Auscultation may reveal a benign systolic ejection murmur along the left sternal border, often from flow across the pulmonary arteries. A single second heart sound and an ejection click may be present. Truncal valve stenosis produces a systolic ejection murmur. Truncal valve regurgitation produces a diastolic murmur. 

Associated Anomalies 

Truncus arteriosus is frequently associated with other cardiac and extracardiac anomalies: 

• Coronary Artery Anomalies: These are very common, occurring in 50% to 80% of cases. Anomalies in the position and form of the coronary ostia are often observed, such as a posterior pulmonary artery origin or small coronary ostia.

• Aortic Arch Anomalies: A right aortic arch is frequently present. Double aortic arch is also not an uncommon association. 

• Coarctation or Interrupted Aortic Arch: Occurs in approximately 10% of cases. Type 4 of the Van Praagh classification specifically addresses this.

• Common Atrioventricular Valve: This anomaly is often seen in conjunction with truncus arteriosus.

• Ventricular Hypoplasia: Hypoplasia of one of the ventricles can also be an associated finding. 

Differential Diagnosis 

An aortopulmonary window can be considered in the differential diagnosis, though it has a different embryological origin than truncus arteriosus. The key difference is that an aortopulmonary window involves two arterial valves (aortic and pulmonary) with a communication between the aorta and pulmonary artery above these valves, whereas truncus arteriosus has only a single arterial valve. Similarly, an anomalous pulmonary artery from the Aorta has been called "hemitruncus", although this is wrong as it has a pulmonary and an aortic valve.

Collett and Edwards classification

Historically, truncus arteriosus was classified by Collett and Edwards - 1945. However, this classification is largely abandoned, particularly because its Type IV designation (absence of central pulmonary arteries with lung vascularization by major aortopulmonary collateral arteries or MAPCAs) does not fit the definition of a common trunk. Type IV is anatomically closer to pulmonary atresia with VSD and MAPCAs (TOF-PA Type C) rather than a true common truncus.

Type I: Main pulmonary artery from common arterial trunk. It then divides in the branch pulmonary arteries (RPA and LPA).

Type II: RPA and LPA arise from posterior part of the common arterial trunk. 

Type III: RPA and LPA arise from lateral part of truncal root. 

Type IV: RPA and LPA supplied by collaterals from descending aorta. (Tetralogy of Fallot with pulmonary atresia). Type 4 is not considered a truncus arteriosus but rather now classified as TOF-PA. 

Van Praagh classification

The Van Praagh modified classification is now the prevailing system for describing truncus arteriosus: 

The original Van Praagh classification (1965) was as such:

• Type A (truncus arteriosus with ventricular septal defect) 

  • A1: MPA from truncal vessel and divides into RPA and LPA

  • A2: RPA and LPA arise separately from posterior part of truncal vessel 

  • A3: One lung supplied by branch PA from the truncal vessel. The other lung (commonly the left) supplied by a ductus-like collateral. There is absence of a PA branch from truncal vessel supplying that other lung.  

  • A4: Truncal vessel is a large PA. There is interruption of the aortic arch or presence of a coarctation.

• Type B (truncus arteriosus without ventricular septal defect). 

The modified Van Praagh classification (2000):

• Type 1: A main pulmonary artery originates from the common trunk, which then branches into the right and left pulmonary arteries. 

• Type 2: The right and left pulmonary arteries originate directly and separately from the posterior aspect of the common trunk. Distinguishing between Type 1 and Type 2 can sometimes be challenging. 

• Type 3: One pulmonary artery (e.g., the right pulmonary artery) arises from the common trunk, while the other pulmonary artery (e.g., the left pulmonary artery) originates from the ductus arteriosus or another source. This type is sometimes referred to as "aortic dominance". 

• Type 4: Characterized by an interrupted aortic arch, where a large pulmonary artery arises from the common trunk, and the descending aorta is small or absent and supplied by the ductus arteriosus. This is also known as "pulmonary dominance". This type often involves a coarctation that is extremely severe.

Truncus Arteriosus

Common arterial trunk, or Truncus arteriosus (TA) (also referred to as persistent truncus arteriosus or truncus arteriosus communis), is a rare but severe congenital heart anomaly. It is characterized by a single arterial trunk arising from the heart that gives origin to the systemic, pulmonary, and coronary arteries. Typically, a large subtruncal ventricular septal defect (VSD) is also present, allowing both ventricles to eject blood into this common truncal vessel and provide the combined ventricular output. It was first described in 1798.

Incidence

TA is found in less than 1% to 4% of all congenital heart defects (CHD). The estimated incidence is approximately 9–11 cases per 100,000 live births. Without surgical intervention, TA is usually fatal, with a mean age of death around 2.5 months, and 80% of affected children dying within the first year of life, primarily due to congestive heart failure, intercurrent infections, or pulmonary vascular disease.

Embryological Origins and Pathophysiology

The primary cause of truncus arteriosus is the failure of septation of the embryologic truncus arteriosus. This involves the lack of development of the conotruncal ridges, which normally fuse to form the arterial valves and the distal infundibulum, and are responsible for conotruncal septation. Neural crest cells, which migrate through pharyngeal arches, are critical in forming the endocardial cushions in the truncus arteriosus and conus cordis and extending the outflow tracts. Disruption of their normal migration can lead to conotruncal anomalies like TA. 

The development of a four-chambered heart with two separate outflow tracts (aorta and pulmonary artery) from an initial single tube involves several complex embryological events. These include looping, the formation of extracardiac mesenchyme, and the remodeling of myocardial epithelium. Crucially, around the ninth to eleventh week of gestation, the common arterial trunk typically undergoes septation, forming the aorta and pulmonary artery with their respective semilunar valves. This process involves:

• Levoposition: Movement towards the central portion of the trunk, shifting leftward.

• Rotation: The aorta rotates around the pulmonary artery.

• Axial Rotation: The aorta rotates on its own axis, leading to the normal positioning of coronary ostia.

Truncus arteriosus arises from an interruption in these critical phases of embryogenesis, specifically due to the absence of septation of this common trunk, resulting from the lack of the truncoseptum and aortopulmonary septum. This absence also prevents the development of the conal or infundibular septum. Consequently, TA is always associated with a large, non-restrictive interventricular septal defect, typically described as a malalignment defect. This allows for a mixing of oxygen-rich and oxygen-poor blood. The common trunk receives both venous and arterial blood, or blood rich in carbon dioxide and oxygen. Genetically, TA is linked to anomalies of mesenchymal tissue and neural crest cell migration. Neural crest cells are known to influence the fourth brachial arch, and their ablation in vitro can lead to a high incidence of persistent truncus arteriosus. TA can occur as an isolated defect. It is also associated with mutations on chromosome 22q11.2, seen in conditions like DiGeorge syndrome, which involves alterations in neural crest cell development. This deletion affects the aortopulmonary septum, a structure derived from the neural crest. Other associated genetic syndromes include Trisomy 21 (Down syndrome) and CHARGE syndrome.

Anatomy, Morphology and Classifications

TA presents with variable anatomical features, most notably regarding the origin and configuration of the pulmonary arteries, the ventricular septal defect, and the truncal valve.

• Classifications:

  • The Collett and Edwards classification recognizes four types based on the pulmonary artery origin. This classification is now less used:

    • Type I: A short common pulmonary artery segment arises from the side of the truncus arteriosus and then bifurcates into the right and left pulmonary arteries. This is the most common type, observed in about 48% to 60% of patients.

    • Type II: Both branch pulmonary arteries arise separately from the posterior aspect of the common arterial trunk, close to each other from two distinct orifices. This accounts for about 29% to 30% of cases.

    • Type III: The branch pulmonary arteries arise separately and more widely separated from the lateral aspects of the common trunk. This is less common, about 6% to 11% of cases.

    • Type IV (Pseudotruncus): No pulmonary artery arises from the ascending part of the truncus. Instead, the pulmonary circulation is supplied entirely by major aortopulmonary collateral arteries (MAPCAs) arising from the descending aorta. This type is now generally considered an extreme form of tetralogy of Fallot with pulmonary atresia rather than a true truncus arteriosus.

  • Van Praagh's classification divides TA into types A (VSD present) and B (VSD absent, extremely rare). Type A is further subdivided: A1 is similar to Collett and Edwards Type I; A2 encompasses Types II and III; A3 involves the absence of one pulmonary artery; and A4 is associated with an underdeveloped or interrupted aortic arch. Nowadays, we use the modified Van Praagh classification.

Reference: Truncus Arteriosus by Christian J. Kellenberger - https://radiologykey.com/truncus-arteriosus-2/

• Ventricular Septal Defect (VSD): A large VSD is almost always present and is typically subtruncal or perimembranous infundibular, directly beneath the truncal valve. The truncal valve often overrides the VSD, similar to Tetralogy of Fallot. Rarely, the ventricular septum may be intact.

• Truncal Valve: The truncal valve morphology is rarely normal and is abnormal in most cases.

  • It most commonly has three cusps (approximately 66% to 69% of patients), but can also be quadricuspid (22% to 25%) or bicuspid (9% to 10%). Rarer forms with five or six cusps exist.

  • The leaflets are often thickened, dysplastic, and may have limited mobility.

  • Truncal valve regurgitation (insufficiency) is common, seen in almost 50% of patients, and can be moderate to severe, significantly impacting hemodynamics and prognosis.

  • Truncal valve stenosis occurs less often (25%) than regurgitation, but severe stenosis is poorly tolerated as it increases afterload on both ventricles.

  • In summary, this valve, located at the origin of the common trunk, can have three cusps, but frequently has more (e.g., quadricuspid) or fewer (e.g., bicuspid, monocuspid). It is often dysplastic (abnormally formed), which can lead to stenosis (narrowing) or insufficiency (leakage). The truncal valve is always in fibrous continuity with the mitral valve. On the right side, there is often a rudimentary muscular conus (infundibulum) separating the tricuspid valve from the truncal valve, mimicking the normal right ventricular outflow tract.

• Pulmonary Arteries:

  • Their origin from the truncus defines the anatomical types, as described above. They usually arise from the left posterolateral aspect of the truncus, a small distance above the truncal valve.

  • Stenosis at the origin of the pulmonary arteries or hypoplasia can occur, and may develop progressively after birth. This stenosis can protect the downstream pulmonary arterioles from developing pulmonary vascular obstructive disease.

  • In some cases, only one pulmonary artery may originate from the truncus, with the other being hypoplastic and supplied by a patent ductus arteriosus (PDA) or MAPCAs.

  • Type 1 (Collet & Edwards) / A1 (Van Praagh): A short common pulmonary artery trunk originates from the truncus, before bifurcating into the right and left pulmonary arteries.

  • Type 2 (Collet & Edwards) / A2 (Van Praagh): The right and left pulmonary arteries arise directly from the common truncus, often close together.

  • Type 3 (Collet & Edwards) / A3 (Van Praagh): One pulmonary artery branch originates from the truncus, while the other arises extra-pericardially, often resembling pulmonary atresia with pulmonary collaterals.

  • Type 4 (Collet & Edwards): No main pulmonary artery or branches are seen, with the pulmonary circulation supplied by major aortopulmonary collateral arteries (MAPCAs). This is functionally distinct from TA Type 3 in Van Praagh's classification.

• Coronary Arteries: The coronary artery pattern in TA is variable, and ostial origins are frequently abnormally located. These anomalies are generally not significant for surgical repair unless a coronary artery arises high in the sinus of Valsalva near the pulmonary artery origin, where it can be injured during repair, or if an accessory descending branch crosses the right ventricle where a ventriculotomy is performed.
  
  

• Associated Cardiac Anomalies: TA frequently presents as an isolated defect, but can be associated with other significant cardiac anomalies, including:

  • Aortic Arch Anomalies: These are the most frequent associated lesions. A right aortic arch is present in approximately 25% to 33% of patients. Interrupted aortic arch (IAA) occurs in about 10% to 21% of TA cases (Van Praagh Type A4), typically as a Type B interruption (between the left common carotid and left subclavian arteries). In IAA with TA, the descending aorta is supplied by a large patent ductus arteriosus, which can be mistaken for the aortic arch.

    • Interrupted aortic arch (especially Type B).

    • Aortic coarctation.

    • Right or double aortic arch.

    • Partial anomalous pulmonary venous return.

    • Persistent left superior vena cava.

    • Atrioventricular valve anomalies (e.g., discordance).

    • Hearts with physiologically univentricular physiology.

    • The presence or absence of a ductus arteriosus is variable, but often present with interrupted aortic arch.

  • Patent Ductus Arteriosus (PDA): A PDA is almost uniformly absent in patients with truncus arteriosus, except when an interrupted aortic arch is present.

  • Anomalies of the coronary arteries are common and important for surgical planning. A common variant is a single coronary ostium. The proximity of the left coronary artery to the pulmonary artery origins is a critical consideration for surgeons.

  • Other Rare Anomalies: These include secundum atrial septal defect, partial and complete atrioventricular canal defects, mitral hypoplasia, mitral atresia, mitral stenosis, tricuspid atresia, straddling tricuspid valve, Ebstein malformation, aortic atresia, hypoplastic left ventricle, double-inlet left ventricle, heterotaxy syndrome, and left pulmonary artery sling. A persistent left superior vena cava draining into the coronary sinus is found in 10% to 15% of patients.

Pathophysiology

The primary hemodynamic effect of truncus arteriosus is the mixing of systemic and pulmonary venous blood in the single arterial trunk, leading to variable degrees of cyanosis. The clinical presentation is largely determined by the magnitude of pulmonary blood flow and pulmonary vascular resistance, as well as the presence and severity of truncal valve abnormalities.

• High Pulmonary Blood Flow: If pulmonary vascular resistance is low and the pulmonary arteries are large and unobstructed, there will be a rapid runoff from the truncus into the pulmonary circulation. This leads to significantly increased pulmonary blood flow, often causing severe congestive heart failure in early infancy. In such cases, cyanosis may be minimal or not apparent due to high arterial oxygen saturation.

• Low Pulmonary Blood Flow: If there is significant pulmonary artery stenosis or rising pulmonary vascular resistance, pulmonary blood flow is restricted, resulting in marked cyanosis.

• Pulse Pressure: Due to low pulmonary vascular resistance and rapid runoff, a wide pulse pressure with bounding peripheral pulses might be expected. However, if pulmonary blood flow is very high, a large proportion of blood may preferentially enter the pulmonary circulation during systole, leading to lower systolic pressure and a less prominent wide pulse pressure in the systemic circulation.

• Truncal Valve Anomalies: Truncal valve regurgitation significantly increases the volume load on the ventricles, often leading to cardiac failure. Severe truncal valve stenosis can cause biventricular outflow obstruction.

Clinical Features

The clinical presentation of truncus arteriosus varies based on the pulmonary to systemic flow ratio.

• Types I and II: Infants typically present with mild cyanosis shortly after birth, which may decrease as pulmonary blood flow increases. However, large increases in flow commonly lead to cardiac failure, manifested by increased respiratory effort, tachypnea, sweating, and poor weight gain. Peripheral pulses may be bounding, and the precordium hyperactive. A loud ejection click and a single loud second heart sound are common. A loud ejection systolic murmur is heard at the base, and a mid-diastolic apical rumble may be present. Truncal regurgitation can cause a high-pitched, early diastolic murmur at the lower-left sternal border.

• Type III: Clinical features depend on the severity of pulmonary artery stenosis. If obstruction is present, cardiac failure symptoms are usually less severe, and a moderate degree of cyanosis is evident. Continuous murmurs due to flow across stenotic pulmonary artery ostia may be heard.

• Type IV: Clinical features are similar to those of Tetralogy of Fallot with pulmonary atresia, characterized by marked cyanosis.

Several classification systems exist for truncus arteriosus, primarily for anatomical definition and surgical planning:

• Collet & Edwards (1949): Categorizes TA based on the origin of the pulmonary arteries from the common trunk (Types 1-4). This is widely used by cardiologists due to its anatomical precision.

• Van Praagh (later modified): Similar in many respects to Collet & Edwards (Types A1, A2, A3). A modified Van Praag classification was simplified by the STS (Society of Thoracic Surgeons) and EACTS (European Association for Cardio-Thoracic Surgery) in 2000, categorizing TA by pulmonary artery confluence, absence of one pulmonary artery, or association with interrupted aortic arch/severe coarctation.

• Anderson: Provides a detailed anatomical description. Surgeons prefer an "Andersonian" descriptive approach, focusing on the precise origin and distance of pulmonary vessels from the main trunk, as well as the position and origin of coronary arteries and the nature of the IVSD.

It is important to differentiate TA from an aortopulmonary window (APW). While both involve a communication between the aorta and pulmonary artery, APW features two normally separated great vessels because the truncoseptum is present, allowing for the formation of two distinct valvar annuli. The defect in APW is the absence of the aortopulmonary septum, occurring above the valvar annuli. APW does not typically involve an IVSD and is generally easier to treat surgically.

Investigations

• Electrocardiography (ECG): Often shows right atrial hypertrophy, with right axis deviation and combined ventricular hypertrophy being most common. Prominent left ventricular forces and left atrial enlargement can also occur.

• Chest Radiography (X-ray): Cardiomegaly is frequent in Types I and II, involving both ventricles, often with dominant left ventricular enlargement if aortic insufficiency is associated. Pulmonary vascularity is increased. A characteristic feature is a narrow superior mediastinum due to the absence of a main pulmonary artery shadow, though this may not be evident in Type I due to the common pulmonary trunk. A right-sided aortic arch, present in about one-third of patients, combined with increased pulmonary vascularity and cardiomegaly, is highly suggestive of TA. In Types III and IV, the heart size is typically not as large, and pulmonary arterial markings are less prominent.

• Echocardiography: This is the diagnostic test of choice and is usually sufficient for a complete preoperative assessment.

  • It clearly demonstrates a single arterial trunk overriding a subaortic VSD.

  • The truncal valve (number of cusps, thickening, dysplasia) can be examined, and the severity of regurgitation and/or stenosis assessed using color Doppler.

  • Crucially, it allows identification of the origin and branching patterns of the pulmonary arteries from the common trunk (differentiating types I, II, and III), and their size and any stenoses.

  • Evaluation of aortic arch anatomy (e.g., right aortic arch, interrupted aortic arch) and associated anomalies is essential. A large ductus arteriosus supplying the descending aorta in IAA can be differentiated from the true aortic arch by characteristic imaging sweeps.

  • Transesophageal echocardiography (TEE) can be used intraoperatively or postoperatively to assess the adequacy of repair, including residual VSDs, right ventricle-to-pulmonary artery conduit obstruction, and truncal valve competency.

• Cardiac Catheterization and Angiography: May be necessary when echocardiography findings are unclear or to assess pulmonary vascular resistance, especially if there is suspicion of severe pulmonary vascular disease or to delineate complex coronary anatomy or anomalous pulmonary artery origins. Injections into the truncal root and left ventricle provide crucial anatomical details. It is important to differentiate TA from other conditions like aortopulmonary fenestration or Tetralogy of Fallot with pulmonary atresia, as the catheter course can be misleading.

Management

The definitive management for truncus arteriosus is early neonatal surgical repair, typically performed within the first week of life, to prevent intractable cardiac failure and the development of irreversible pulmonary vascular disease.

The principles of surgical correction involve:

• Closing the VSD to ensure the left ventricle communicates with the newly formed aorta.

• Establishing right ventricle (RV) to pulmonary artery (PA) continuity by detaching the pulmonary arteries from the truncus and connecting the RV to the pulmonary arteries, often using a valved conduit (homograft or heterograft).

• Arch reconstruction if an interrupted aortic arch is present. Repair of TA associated with interrupted aortic arch carries a higher mortality risk, but complete repair in the first month of life has shown improved outcomes.

Key considerations and risk factors for surgical mortality include:

• Prematurity and low birth weight.

• Aortic arch interruption.

• Significant truncal valve regurgitation or dysplasia.

• Coronary artery anomalies.

• Elevated pulmonary vascular resistance.

• Age at repair greater than 3–6 months.

Medical management with diuretics, and vasodilators can stabilize the patient before surgery, but it is not a definitive treatment and cannot prevent the progression of pulmonary vascular disease. Prostaglandin E1 (PGE1) infusion may be used in cases with interrupted aortic arch to maintain ductal patency and systemic perfusion. However, in other forms of TA, efforts are made to avoid high FiO2 and hyperventilation to prevent reducing pulmonary vascular resistance, which could exacerbate heart failure. Post-repair, follow-up focuses on potential complications such as residual VSDs, truncal valve dysfunction, right ventricle-to-pulmonary artery conduit stenosis or regurgitation, and branch pulmonary artery stenosis. Reinterventions, particularly for conduit replacement, are common, especially if the procedure is performed at a young age.

Medical Management: Initial management in the first few days of life typically involves reducing fluid overload by administering diuretics, along with adequate intravenous nutrition to manage heart failure symptoms.

Surgical Management: Surgical correction of truncus arteriosus, first successfully performed in 1967, is now the definitive treatment.

• Timing of Surgery: The consensus is that correction should be performed in the neonatal period, ideally between two and four to five weeks of life. This "magic window" aims to intervene after pulmonary resistances decrease but before significant pulmonary vascular disease develops from chronic hyperperfusion. Surgery is generally contraindicated if pulmonary vascular resistances are too high.

• Surgical Procedure (Rastelli-type Repair): The standard repair, largely unchanged since it was described by James Kirklin and popularized by Giancarlo Rastelli, involves:

  1. Isolation of Pulmonary Arteries: The pulmonary arteries are separated from the common truncus.

  2. Closure of the IVSD: The interventricular septal defect is closed using a patch, creating a left ventricular outflow to the neoaorta. This defect is typically due to the absence of the infundibular septum, and care must be taken to avoid the conduction system during closure.

  3. Right Ventricle-to-Pulmonary Artery (RV-PA) Conduit: A conduit (tube) is inserted to connect the right ventricle to the newly separated pulmonary artery branches, creating a new right ventricular outflow tract.

  4. Truncal Valve Repair/Replacement: The native truncal valve is repaired if possible to improve competence or reduce stenosis; if severely dysplastic, it may be replaced.

  5. Associated Lesions: If an interrupted aortic arch is present (10-20% of cases), it is repaired, often requiring deep hypothermic circulatory arrest with antegrade cerebral perfusion.

  6. Interatrial Communication: It is considered beneficial to leave a calibrated interatrial communication to allow for a right-to-left shunt in case of pulmonary hypertension crises, which can be life-saving.

Outcomes and Reinterventions

Surgical outcomes for truncus arteriosus are generally good, with acceptable survival rates and quality of life. Early mortality rates have significantly decreased, with modern series showing mortality comparable to that of the late 1970s (around 9%). Long-term follow-up studies show excellent survival even into adulthood, with women successfully carrying pregnancies to term. However, the main long-term challenge in TA patients is the high rate of reinterventions, especially related to the RV-PA conduit. Almost all patients require reoperation within 10-15 years post-primary repair. The primary reasons for reintervention are:

• Conduit Stenosis/Insufficiency: The prosthetic conduits used in neonates or infants do not grow with the child and tend to calcify and degenerate, leading to obstruction or leakage.

• Truncal Valve Dysfunction: Stenosis or insufficiency of the native truncal valve or a prosthetic valve if replaced.

• Pulmonary Artery Stenosis: Often related to the growth of the native pulmonary arteries or issues at their anastomosis with the conduit.

• Myocardial ischemia or ventricular dysfunction.

Factors influencing earlier reintervention include smaller conduit size and the use of ECMO post-operatively. Patients may undergo multiple reoperations before reaching adulthood. Percutaneous interventions (e.g., balloon dilation, stent placement) are also used to manage conduit stenosis, though stent placement near the left coronary artery can be problematic due to potential compression.

Conduit Options: Various materials have been used for RV-PA conduits, each with advantages and disadvantages:

• Autografts: (e.g., pulmonary autograft) are limited by availability.

• Homografts: Cryopreserved human aortic or pulmonary homografts were historically favored due to good durability, especially pulmonary homografts in Fallot repair, but their availability is limited, and they can calcify.

• Xenografts: (e.g., bovine jugular vein conduits like Contegra) are widely available, contain a natural valve, and have shown favorable freedom from reintervention compared to some other options, although reoperation rates remain significant.

• Prosthetic Grafts: (e.g., Gore-Tex/PTFE) are available in various sizes and are used, especially in neonates, but also require reintervention.

• Melody Valve: A stent-mounted bovine jugular vein conduit that can be dilated percutaneously, potentially delaying open reoperation.

"Conduitless" Repair Techniques: To reduce the need for repeat conduit replacements, alternative "conduitless" repair strategies have been developed, aiming for direct continuity between the right ventricle and pulmonary arteries without an interposition graft.

• Barbero-Marcial Technique (1990): This technique uses the dilated left atrial appendage as the posterior wall of the RV-PA connection, with a pericardial patch forming the anterior wall. Early variations included a monocusp valve, but later approaches avoided a valve altogether to prevent future stenotic issues.

• Advantages of Conduitless Repair: Reduced need for reintervention, potential for growth of the RVOT, lower cost, and less immunogenicity.

• Limitations: Not suitable for all patients, especially those with severe truncal valve insufficiency/stenosis, significant pulmonary hypertension, or very small/imbalanced ventricles.

Despite advances, there is currently no "ideal" conduit that grows with the patient and lasts indefinitely. The continuous challenge in TA management remains the high reintervention rate, driving ongoing research into better surgical techniques and materials.

References: 

• Truncus Arteriosus by the Congenital Heart Academy - YouTube (Italian)

• Dipchand AI, et al., editors. Manual of Cardiac Care in Children. Cham, Switzerland: Springer Nature Switzerland AG; 2024.

• Rudolph AM. Congenital Diseases of the Heart: Clinical-Physiological Considerations. 3rd ed. Oxford, UK: Blackwell Publishing; 2009.

• Lai WW, Mertens LL, Cohen MS, Geva T, editors. Echocardiography in Pediatric and Congenital Heart Disease: From Fetus to Adult. 2nd ed. Hoboken, NJ: Wiley-Blackwell; 2016.

• Khalid O, Awad S. Pediatric Electrocardiography: An Algorithmic Approach to Interpretation. Cham, Switzerland: Springer International Publishing Switzerland; 2016.

• Park IS, editor. An Illustrated Guide to Congenital Heart Disease: From Diagnosis to Treatment – From Fetus to Adult. Singapore: Springer Nature Singapore Pte Ltd; 2019.

• Butera G, Chessa M, Eicken A, Thomson J, editors. Cardiac Catheterization for Congenital Heart Disease: From Fetal Life to Adulthood. Milan, Italy: Springer-Verlag Italia; 2015.

• Alboliras ET, Hijazi ZM, Lopez L, Hagler DJ, editors. Visual Guide to Neonatal Cardiology. Hoboken, NJ: John Wiley & Sons Ltd; 2018.

• Rigby ML, Anderson RH, Ho SY. Echocardiography in Congenital Heart Disease Made Simple. London, UK: Imperial College Press; 2005.

• Lintermans JP. Two-dimensional echocardiography in infants and children. Dordrecht, Netherlands: Martinus Nijhoff Publishers; 1986.

• Acar P. Échocardiographie pédiatrique et fœtale. 2nd ed. Paris, France: Doin Éditeurs; 2008.

Case 1

Parasternal long axis view showing the common arterial trunk. There is some mild truncal valve insufficiency. 

Case 2

Common arterial trunk (Truncus Arteriosus). Common origin of pulmonary arteries (type 1 - A1). Dysplastic (thick) truncal valve leaflets. The branch pulmonary artery are small / hypoplastic. There is some truncal valve insufficiency. 

Case 3 - Truncus Arterosus with perimembranous VSD