Truncus Arteriosus 

Updated: Dec 31, 2019
Author: Doff B McElhinney, MD; Chief Editor: Howard S Weber, MD, FSCAI 

Overview

Background

Truncus arteriosus (TA) is an uncommon congenital cardiovascular anomaly that is characterized by a single arterial trunk arising from the normally formed ventricles by means of a single semilunar valve (ie, truncal valve). In the most common type, the pulmonary arteries originate from the common arterial trunk distal to the coronary arteries and proximal to the first brachiocephalic branch of the aortic arch. The common trunk typically straddles a defect in the outlet portion of the interventricular septum (ie, conal septum); however, in rare cases, it may originate almost completely from the right or left ventricle. In patients with a patent and normal caliber aortic arch, the ductus arteriosus is either absent or diminutive.

Embryology

The anomaly is thought to result from incomplete or failed septation of the embryonic truncus arteriosus, hence the persistence of the Latin term truncus arteriosus and its variants. Aortopulmonary and interventricular defects are believed to represent an abnormality of conotruncal septation. Because the common trunk originates from both the left and right ventricles, and pulmonary arteries arise directly from the common trunk, a ductus arteriosus is not required to support the fetal circulation.

Accordingly, an inverse relationship between the caliber of the ductus arteriosus (derived from the sixth branchial arch) and that of the distal portion of the aortic arch (derived from the fourth branchial arch) is typically present. Although the hemodynamic consequences of a common arterial outflow may predispose to the development of the fourth or the sixth arch (but not both), anomalous development of the arch system is likely a fundamental aspect of the morphogenetic anomalies that produce truncus arteriosus.

Anatomy

Pulmonary arteries may arise from the common trunk in one of several patterns, which are often used to classify subtypes of truncus arteriosus. Several classification schemes have been proposed, none of which is ideal.

The earliest classification, developed by Collett and Edwards in 1949, includes truncus arteriosus types I-IV, as follows[1] :

  • Truncus arteriosus type I is characterized by origin of a single pulmonary trunk from the left lateral aspect of the common trunk, with branching of the left and right pulmonary arteries from the pulmonary trunk.

  • Truncus arteriosus type II is characterized by separate but proximate origins of the left and right pulmonary arterial branches from the posterolateral aspect of the common arterial trunk.

  • In truncus arteriosus type III, the branch pulmonary arteries originate independently from the common arterial trunk or aortic arch, most often from the left and right lateral aspects of the trunk. This occasionally occurs with origin of one pulmonary artery from the underside of the aortic arch, usually from a ductus arteriosus.

  • Type IV truncus arteriosus, originally proposed by Collett and Edwards as a form of the lesion with neither pulmonary arterial branch arising from the common trunk, is now recognized to be a form of pulmonary atresia with ventricular septal defect rather than truncus arteriosus.

Collett and Edwards describe variations of each of these types.

In 1965, Van Praaghs proposed the other commonly cited classification scheme that also includes 4 primary types, as follows[2] :

  • Type A1 is identical to the type I of Collett and Edwards.

  • Type A2 includes Collett and Edwards type II and most cases of type III, namely those with separate origin of the branch pulmonary arteries from the left and right lateral aspects of the common trunk.

  • Type A3 includes cases with origin of one branch pulmonary artery (usually the right) from the common trunk, with pulmonary blood supply to the other lung provided either by a pulmonary artery arising from the aortic arch (a subtype of Collett and Edwards type III) or by systemic to pulmonary arterial collaterals.

  • Type A4 is defined not by the pattern of origin of branch pulmonary arteries, but rather by the coexistence of an interrupted aortic arch. In the vast majority of cases of type A4, which fall into the type I of Collett and Edwards, the pulmonary arteries arise as a single pulmonary trunk that then branches. In any of these patterns, intrinsic stenosis, hypoplasia, or both may be present in one or both branch pulmonary arteries, which may have an effect on management and outcome.

The Van Praagh scheme is combined with Collett and Edwards types in the image below.

Anatomic subtypes of truncus arteriosus (TA), acco Anatomic subtypes of truncus arteriosus (TA), according to the classification systems of both Collett and Edwards (I, II, III) and the Van Praaghs (A1, A2, A3, A4).

Associated cardiovascular anomalies

Various abnormalities may be associated with truncus arteriosus, some of which may have an impact on management and outcome.

Structural abnormalities of the truncal valve, including dysplastic and supernumerary leaflets, are frequently observed, and significant stenosis or regurgitation (moderate or severe) through the truncal valve may be present in 20% or more patients.

Similarly, proximal coronary arteries are abnormal in many patients, with a single coronary artery and an intramural course as the most important variations.

The other major anomaly associated with truncus arteriosus in a substantial portion of cases is interruption of the aortic arch, which almost always occurs between the left common carotid and subclavian arteries.

Other relatively common but minor associations include right aortic arch, left superior caval vein, aberrant subclavian artery, and atrial septal defect. In addition to these defects found in the usual spectrum of truncus arteriosus, several other major but rare associated anomalies are reported, including complete atrioventricular septal defect, double aortic arch, and various forms of functionally univentricular heart.

Sepsis is probably the most important noncardiac problem in the differential diagnosis of neonates with truncus arteriosus, as well as other forms of complex congenital heart disease. Young infants with truncus arteriosus frequently present in shock because of high output heart failure with significant pulmonary overcirculation. This scenario may resemble the presentation of neonatal sepsis, especially when the ratio of pulmonary-to-systemic blood flow is sufficiently high that the patient is not cyanotic.

Pathophysiology

Pathophysiology of truncus arteriosus is typified by pulmonary overcirculation and systemic ventricular volume overload. Outflow from both ventricles is directed into the common arterial trunk. Pulmonary blood flow is derived from this combined ventricular output, and its magnitude depends on the ratio of resistances to flow in the pulmonary and systemic vascular beds. Because of the mixing (although not complete) of left and right ventricular output that occurs primarily during systole and at the level of the common arterial trunk, subnormal systemic arterial oxygen saturation may occur, although it usually is not significant enough to result in clinical cyanosis. Similarly, because the systemic and pulmonary circulations are essentially in parallel, pulmonary blood flow typically is at least 3-fold higher than systemic blood flow, with pulmonary overcirculation and increased myocardial work that results in increased resting oxygen demand and decreased metabolic reserve.

Etiology

As with most forms of congenital heart disease, the causes of truncus arteriosus are unknown. In experimental animal models, truncus arteriosus has been linked to abnormal development of cells from the neural crest that normally inhabit the outflow region of the developing heart. This is thought to be an important etiologic factor in at least some cases of human truncus arteriosus also.

As with various other congenital cardiac anomalies of the conotruncal region, a substantial number of patients with truncus arteriosus (approximately 30-40%) have microdeletions within chromosome band 22q11.2, which contains a number of characterized genes. This particular type of chromosomal deletion is thought to affect migration or development of cardiac neural crest cells and may contribute to the pathogenesis of truncus arteriosus in certain cases.

Patients with truncus arteriosus and anomalies of the branch pulmonary arteries, such as stenosis or separate origin from the undersurface of the aortic arch, may have a higher incidence of association with band 22q11 deletion. Other specific features of truncus arteriosus that may be related to chromosomal deletion have yet to be characterized.[3]

The specific gene product or products responsible for cardiovascular anomalies in individuals with a 22q11 deletion has not been identified definitively in humans, although one of the genes in the 22q11.2 band, TBX1, has been shown to be involved in pharyngeal arch and conotruncal development. Extensive research regarding truncus arteriosus and band 22q11 association is being conducted.

For the most part, other factors that may cause truncus arteriosus in humans have not been clearly identified, although potential associations have been suggested, such as the following:

  • Other sporadic chromosomal and genetic abnormalities have been reported in humans with truncus arteriosus, including duplication of chromosome arm 8q and mutation of the NKX2.6 and GATA6 genes.[4]

  • Several other genes have been associated with truncus arteriosus in transgenic mouse models, including Tbx20, ALK2, Cited2, and Semaphorin 3c, but so far these genes have not been implicated in human truncus arteriosus.

  • Several studies found that children of mothers with significant diabetes mellitus during pregnancy had an increased incidence of truncus arteriosus (as well as other conotruncal malformations)[5] ; however, this is not widely recognized as a significant risk factor.[6]

  • Although certain teratogens (eg, retinoic acid, bis-diamine) have been found to predispose to truncus arteriosus in animal models, no evidence suggests that these or others contribute importantly to this anomaly in humans.

DiGeorge syndrome or velocardiofacial syndrome, often included together as variations of CATCH-22 syndrome, are present in approximately 30-35% of patients with truncus arteriosus; most of these patients have deletions in band 22q11.

The most common noncardiac anomalies in patients with truncus arteriosus are those typically found in association with CATCH-22 syndrome, such as velopharyngeal insufficiency, cleft palate, and thymic and parathyroid dysfunction.

Other noncardiac anomalies found sporadically in patients with truncus arteriosus include renal abnormalities, vertebral and rib anomalies, and anomalies of the alimentary tract.

Epidemiology

United States data

Truncus arteriosus represents 1-2% of congenital heart defects in liveborn infants. Based on an estimated incidence of congenital heart disease of 6-8 per 1,000 liveborn children, truncus arteriosus occurs in approximately 5-15 of 100,000 live births. Among aborted fetuses and stillborn infants with cardiovascular anomalies, truncus arteriosus represents almost 5% of defects.

A population-based review of all cases of live births from 1999 to 2008 identified as having severe congenital heart disease from the Nationwide Inpatient Sample (NIS) database indicated a decrease of the conditions over the study period.[7] There was a significant decreased incidence of truncus arteriosus as well as tetralogy of Fallot, pulmonary atresia, and hypoplastic left heart syndrome; however, these trends varied with sociodemographic factors. The investigators suggested a possible reason for the decreasing prevalence trend was the increased numbers of terminated fetuses with prenatally diagnosed congenital heart disease.[7]

International data

No significant difference in the incidence of truncus arteriosus is noted among those born in the United States compared with other countries.

However, a Canadian longitudinal study (1983-2010) of all individual with congenital heart disease noted a more than 50% increase of severe and other congenital heart disease after the year 2000, with adults comprising two thirds of the cases by 2010.[8] The prevalence of congenital heart disease in the first year of life between 1998 and 2005 was 8.21 per 1000 live births; in 2010, the overall prevalence was 13.11 per 1000 in children and 6.12 per 1000 in adults. A temporal increase in prevalence of congenital heart disease and severe congenital heart disease was noted for children and adults.[8]

Race-, sex-, and age-related demographics

Based on limited data, no racial predilection is apparent.

Although many series report a slight male predominance, no significant predilection based on sex is apparent.

Truncus arteriosus is a congenital anomaly that is present from early in embryonic gestation. Currently, truncus arteriosus is diagnosed using prenatal ultrasonography in a small percentage of patients. Among patients diagnosed after birth, the median age at presentation is generally a few days, which is significantly earlier than was the case 20 or more years ago. Occasionally, patients are not diagnosed until later in infancy, childhood, or even adulthood, although such cases are exceedingly rare in the United States and Europe.

Prognosis

Among patients surviving the early postoperative period, prognosis is generally very good. Few published long-term follow-up data are available on patients undergoing repair in the neonatal and early infant periods because this management strategy came into widespread application in the mid to late 1980s. Moreover, techniques of myocardial protection and perioperative management have changed dramatically even within this period; thus, existing data, limited as they may be, are still likely to underestimate outcome in contemporary patients.

Although late mortality among patients undergoing early repair is minimal, a substantial proportion of premature deaths among such patients are likely to be related to reinterventions. Because the right ventricular outflow tract is usually reconstructed with a nonviable conduit, which does not grow along with the patient, reinterventions for conduit replacement, revision, or dilation are essentially inevitable. In a series following infants younger than 4 months with surgically repaired truncus arteriosus, freedom from conduit-related reintervention was less than 50% at 5 years and less than 10% at 10 years.

Patients who have the conduit replaced earlier in life often require at least one subsequent intervention on the right ventricular outflow tract. Reintervention for truncal valve regurgitation (often within the first year after repair) or for branch pulmonary arterial stenosis is also required in a substantial number of patients.

At major centers in North America, survival to hospital discharge after complete repair of truncus arteriosus is approximately 90-95%. Prognosis appears somewhat less favorable for patients with complicating associated conditions, such as severe truncal valve regurgitation of interruption of the aortic arch. Significant perioperative morbidity is uncommon and includes issues common to many forms of complex congenital heart disease, such as transient arrhythmias, low cardiac output, and sequelae of cardiopulmonary bypass.

Morbidity/mortality

The natural history of truncus arteriosus without surgical intervention is not well characterized. In numerous earlier series, the median age at death without surgery ranged from 2 weeks to 3 months, with almost 100% mortality by age 1 year. Cases of patients surviving into adulthood with unrepaired truncus arteriosus are reported, but they are extremely uncommon. Cause of death in unrepaired patients is usually cardiac arrest or multiple organ failure in the face of systemic perfusion that is inadequate to meet the body's metabolic demands; progressive metabolic acidosis and myocardial dysfunction results.

Currently, for patients undergoing complete repair in the neonatal or early infant periods, early postoperative mortality is generally less than 10%. This represents a substantial improvement from earlier eras; as recently as 20 years ago, the early mortality rate after complete repair was higher than 25% in most series. Among patients surviving the initial postoperative period, the survival rate at a 10- to 20-year follow-up is higher than 80%, with most deaths resulting from sequelae of late repair (pulmonary vascular obstructive disease), reinterventions, or residual/recurrent physiologic abnormalities.

Although rarely used today, surgical palliation by banding of the pulmonary artery to protect the pulmonary vascular bed was a frequently used strategy until the 1970s and early 1980s. This practice resulted in only minor improvement in the natural history of the disease, with substantial early and intermediate mortality rates.

 

Presentation

History

Historical presentation of patients with truncus arteriosus (TA) who are not diagnosed before the onset of symptoms typically consists of the following:

  • Poor feeding/inadequate weight gain

  • Diaphoresis

  • Tachypnea

Symptoms vary and may be more or less pronounced, depending on specific anatomic features and age at presentation. For example, patients with significant truncal valve regurgitation tend to present earlier with more profound symptoms of congestive heart failure.

Physical Examination

Patients with truncus arteriosus rarely present with cyanosis but it may occur in very young neonates in whom pulmonary vascular resistance remains elevated. Even in slightly older neonates and young infants, pulmonary overcirculation and streaming of left and right ventricular outflow into the aorta and pulmonary arteries, respectively, may occasionally result in systemic oxyhemoglobin saturation well above 90%.

Symptoms and signs of congestive heart failure are more common findings than cyanosis in patients presenting early in life. Symptoms of failure typically manifest as pulmonary vascular resistance falls and pulmonary overcirculation increases. With progressively increasing pulmonary blood flow and, consequently, myocardial work, the initial symptoms of congestive heart failure (eg, poor feeding, diaphoresis, mild lethargy) become more evident as failure to thrive ensues.

Patients occasionally present in extremis, with the usual high output failure exacerbated by significant regurgitation of the truncal valve. Patients with associated interruption of the aortic arch may exhibit a shocklike picture of cardiovascular collapse during ductal closure, although the arterial duct frequently remains patent in patients with truncus and interrupted arch, even without pharmacologic therapy.

 

DDx

Diagnostic Considerations

Approach considerations

Important considerations include the following:

  • It is important for clinicians to properly diagnose truncus arteriosus.

  • Consider various abnormalities that may be associated with truncus arteriosus, some of which may have an impact on management and outcome.

  • Also consider potential issues that are of particular concern in patients with truncus arteriosus, including pulmonary hypertensive crisis and volume overload in patients with persistent truncal valve regurgitation.

  • Obtain routine laboratory and imaging studies (to include a full complement of echocardiographic views) in the neonate with truncus arteriosus to aid in determining therapeutic strategy and assist diagnosis.

  • Consult with a cardiologist before beginning, changing, or discontinuing cardiac medications in these patients.

Differential Diagnoses

 

Workup

Laboratory Studies

Routine laboratory studies in the neonate with truncus arteriosus generally aid in determining therapeutic strategy rather than diagnosis.

An important exception in some cases is an arterial blood gas measurement, which helps to evaluate the degree of acidosis on presentation and may aid in differentiating cardiac disease from primary pulmonary pathology when performed before and after administration of 100% inspired oxygen (hyperoxia test).

Note that a hyperoxia test may be misleading in patients with truncus arteriosus and torrential pulmonary blood flow, both because of severe mismatch between pulmonary and systemic blood flow and, in some cases, because of streaming of left and right ventricular outflow into the systemic and pulmonary arterial systems, respectively.

Measurement of serum electrolytes, including total and ionized calcium, is important in patients with truncus arteriosus, given the common association with DiGeorge syndrome, which frequently may include hypoparathyroidism and hypocalcemia.

Electrocardiography

Electrocardiographic (ECG) findings in young infants with truncus arteriosus do not distinguish this lesion from others on the differential diagnosis.

A normal sinus rhythm, normal intervals, and either a normal QRS axis or minimal right-axis deviation are generally observed. Biventricular hypertrophy is a characteristic finding.

In patients with substantial pulmonary overcirculation, left ventricular forces are especially prominent with evidence of left atrial enlargement.

Imaging Studies

Chest radiography

Upon presentation, obtain a chest radiograph in most patients with truncus arteriosus. Cardiomegaly and increased pulmonary vascular markings are typically present, and fullness in the region of the truncal root may possibly be discerned. In patients with a right aortic arch, this radiographic finding in association with increased pulmonary vascular markings suggests truncus arteriosus. A narrowed mediastinal shadow may indicate an absent thymus gland which can be associated with DiGeorge syndrome complex.

Echocardiography

Echocardiography with cross-sectional and Doppler flow analysis is sufficient to confirm the diagnosis of truncus arteriosus and fully characterize the various anatomic features in most patients. A full complement of echocardiographic views is necessary to ensure complete and accurate definition of the anatomy and potential associated anomalies.

Using subcostal coronal and parasternal long-axis images is the best way to demonstrate the single arterial trunk arising from the ventricles, with variable override of the ventricular septum. These views also demonstrate the thickness and mobility of the truncal valve leaflets. In general, the subcostal coronal view allows delineation of the pulmonary arterial origin(s) from the common trunk, although additional views are helpful to more completely characterize the pulmonary arterial anatomy. Morphology of the truncal valve and origins and course of the proximal coronary arteries are best observed from the parasternal short-axis window.

Doppler color imaging from these windows is critical to evaluate pulmonary arterial flow and regurgitation or stenosis of the truncal valve. Imaging from the high parasternal and suprasternal notch views is necessary to define the aortic arch and provide additional perspective on the anatomy of the central pulmonary arteries. Standard approaches to imaging of the ventricular masses, atrioventricular valves, and atriums are important for full characterization of their structure and function.

Increasingly, diagnosis of truncus arteriosus and other complex heart defects is made by prenatal echocardiography. Prenatal echocardiography is generally accurate and sensitive for the diagnosis of truncus arteriosus, although the precise diagnosis may be difficult to distinguish from similar anomalies, such as tetralogy of Fallot or double-outlet right ventricle with pulmonary atresia, or aortic atresia with a ventricular septal defect.[9]

An echocardiographic image of truncus arteriosus is shown in the image below.

Echocardiographic images of truncus arteriosus (TA Echocardiographic images of truncus arteriosus (TA). The top image is from the subcostal coronal window (SC COR) and shows the common trunk (TR) arising from the left ventricle (LV), overriding the interventricular septum. The common trunk branches into the pulmonary trunk and the ascending aorta (AO). The left pulmonary artery (LPA) may be seen branching from the pulmonary trunk. RA=right atrium; RPA=right pulmonary artery. In the bottom image, which is from the suprasternal notch sagittal window, the truncal origin and course of the pulmonary trunk and left pulmonary artery can be appreciated. DAO=descending aorta; IV=innominate vein; LA=left atrium.

The advent of four-dimensional (4-D) fetal echocardiography using spatiotemporal image correlation, tomographic ultrasound imaging display (STIC-TUI echo) and color Doppler has the potential for identifying complex fetal cardiac anomalies in high-risk mothers in the first trimester.[10] The major factor in successful volume acquisition appears to be optimal imaging of the four-chamber view with 2-D ultrasonography.

MRI

MRI is rarely necessary in patients with truncus arteriosus. MRI modality provides excellent imaging for characterizing anatomy, and may be especially useful in reconstructing complex pulmonary arterial anatomy in older patients with truncus arteriosus.

Procedures

Cardiac Catheterization

Standard angiographic images from the truncal root can aid in the assessment of the coronary arterial anatomy and complex pulmonary artery anatomy arising from the thoracic aorta, if echocardiography is inadequate, and in the assessment of regurgitation through the truncal valve.

Cardiac catheterization is generally not required prior to repair in neonates and young infants with truncus arteriosus.[11]

Catheterization is an important tool for evaluating some of the most common anatomic problems in patients with repaired truncus arteriosus, such as obstruction of the surgical reconstructed right ventricular outflow tract, branch pulmonary arterial stenosis, truncal valve regurgitation, and, in patients repaired later in life, pulmonary vascular obstructive disease.

Transcatheter Balloon Dilation

Treatment of pulmonary outflow tract or pulmonary arterial obstruction with transcatheter balloon dilation or stenting is an effective therapy for these problems in many patients who have undergone complex surgical repair.

Biopsy

Histologic examination is not generally indicated in the evaluation of patients with truncus arteriosus. In the rare older patient with evidence of elevated pulmonary vascular resistance, pulmonary biopsy is occasionally performed as a means of assessing the extent of pulmonary vascular obstructive disease.

 

Treatment

Medical Care

Medical care before surgical repair depends on the neonate's clinical presentation.

Most neonates with truncus arteriosus display evidence of congestive heart failure and are usually treated with digitalis and diuretic medicines.

Intravenous prostaglandin is often administered in patients with truncus arteriosus upon presentation because the differential diagnosis includes numerous anomalies with duct-dependent systemic or pulmonary blood flow. However, it is beneficial only in patients with associated interruption of the aortic arch or aortic coarctation.

Other preoperative medications are not generally indicated, although specific circumstances may dictate afterload reducing agents, inotropic medications, or antiarrhythmics.

Full-term and premature newborns with truncus arteriosus may be at increased risk for necrotizing enterocolitis, either preoperatively or postoperatively, and appropriate evaluation should be undertaken in any newborn exhibiting signs or symptoms of necrotizing enterocolitis.

Surgical Care

Indications

Truncus arteriosus invariably requires operative repair.[12] Symptoms typically develop in the early neonatal period, indicating that complete repair is required at this point.

Techniques

Surgical management of truncus arteriosus has undergone significant evolution over the past 30 years. Complete repair was first performed in 1967, but until neonatal and early infant repair became routine in the 1980s, palliative pulmonary artery banding was common, with complete repair performed at an older age. At most centers, primary complete repair in the neonate and young infant has become the accepted standard.

Currently, surgical management consists of complete primary repair, with closure of the ventricular septal defect, committing the common arterial trunk to the left ventricle, and reconstruction of the right ventricular outflow tract.

In patients with both branch pulmonary arteries arising from the common trunk, the standard method of right ventricular outflow tract reconstruction entails removing the central pulmonary arteries from the common trunk en bloc and placing a valved conduit from the right ventricle proximally to the central pulmonary arteries distally. Also, the most common type of conduit used is a cryopreserved valved aortic or pulmonary allograft. Before allograft conduits became widely available, other forms of pulmonary outflow reconstruction were used. These alternative forms remain in use in areas where the cost and availability of conduits prohibit routine use of modern techniques. Such alternatives include xenograft valves housed in synthetic tube grafts, direct anastomosis of the pulmonary arteries to the right ventriculotomy, or autologous flaps of pulmonary or aortic tissue augmented with synthetic patch material.

In patients with one pulmonary artery arising from the common trunk and one from the underside of the aortic arch, the pulmonary arteries are disconnected separately; they are then anastomosed together before being anastomosed to the conduit or are anastomosed to the conduit independently.

Coexisting anomalies are repaired as appropriate with cardiopulmonary bypass, cardioplegia, and sometimes deep hypothermic arrest, depending on anatomic features and the preference of the surgeon.

When the truncal valve is abnormal and repaired at the time of the initial truncus repair, outcomes appear to be significantly worse that when early truncal valve repair is not necessary.[13, 14]

Postoperative Care

Administer routine postoperative care, initially in the cardiac intensive care unit, following correction of truncus arteriosus. Support patients with mechanical ventilation, inotropic medications, and sedation as necessary. Restore fluid balance with diuretic therapy and continue tube thoracostomy until pleural and pericardial effusions have resolved.

Focus the remainder of the inpatient stay on providing sufficient enteral nutrition, parental education, and elucidation of the maintenance pharmacologic regimen (if any) that is adopted.

Postoperative care after repair of truncus arteriosus requires attention to issues that are common to patients with complex congenital heart disease (eg, support of cardiac output) and prevention or management of arrhythmias and end-organ dysfunction.

Management issues include maintenance of intravascular volume and ventricular filling, inotropic support, and acid-base and electrolyte homeostasis. In addition, potential issues that are of particular concern in patients with truncus arteriosus include pulmonary hypertensive crisis and volume overload in patients with persistent truncal valve regurgitation. Because of the lability of the pulmonary resistance vessels that may occur with and following elimination of elevated pulmonary blood flow at high pressures, pulmonary hypertensive crisis currently is less of an issue in early neonatal repair than it was with later repair. Nevertheless, patients may experience episodes of paroxysmal elevation of pulmonary vascular resistance.

Management with extended periods of anesthesia, including neuromuscular blockade and continuous fentanyl infusion, often is helpful. Ventilatory strategies aimed at minimizing pulmonary vascular resistance with supplemental oxygen and avoiding hypercarbia also may be effective. In refractory cases, inhaled nitric oxide or extracorporeal membrane oxygenation may be indicated.

After stabilization in the intensive care unit, removal from mechanical ventilatory and inotropic support, and discontinuation of intracardiac monitoring catheters, transfer the patient to the regular inpatient care area for advancement of feedings and additional postoperative care, depending on the experience and comfort level of the nursing staff on the ward.

Consultations

Unless specific associated anomalies or problems are identified, consultations are not generally necessary.

Band 22q11 deletion is present in approximately one third of patients with truncus arteriosus, and consultation with a geneticist may be appropriate in some of these patients. Although patients with this chromosomal anomaly may have subtle associated abnormalities that are more likely to be identified if an experienced clinical geneticist is consulted, no evidence suggests that outcomes or management considerations differ in patients with or without chromosomal deletion.

When a chromosome 22q11 deletion is identified, comprehensive evaluation for associated conditions is indicated, including an otolaryngologist to evaluate for submucosal cleft palate, an immunologist to evaluate for immunodeficiency, and early intervention services for evaluation of learning and speech.

Consult a cardiologist before beginning, changing, or discontinuing cardiac medications in these patients.

Diet

No special dietary considerations are indicated in patients with truncus arteriosus, other than a diet that might be dictated by associated conditions.

Resume enteral feeding once the patient is hemodynamically stable.

Resume oral feedings when the patient has been removed from mechanical ventilatory support and is adequately alert to take oral feedings safely. In patients with deletion in band 22q11, velopharyngeal insufficiency or cleft palate is frequently present, and oral feedings should be resumed with the aid of feeding specialists.

Activity

Specific restrictions on activity are not indicated in patients with truncus arteriosus. Patients with repaired truncus arteriosus and either residual defects or regurgitation of the right ventricle to pulmonary artery conduit may have limited exercise capacity best addressed on an individual basis.

Prevention

No known methods to prevent the development of truncus arteriosus in the fetus are known. On screening obstetric ultrasonography findings, 4-chamber and great vessel views are sufficient to identify that cardiac anomalies are present. In such an event, the parents should be referred for fetal echocardiography, with which the anatomy of truncus arteriosus can be more fully defined. Diagnosis in utero allows for greater parental choice, and may facilitate planned delivery at a tertiary care center and immediate neonatal stabilization, thus preventing the potential hemodynamic sequelae that can result from the natural history of the lesion.

Long-Term Monitoring

For the early posthospital period, educate parents about the signs and symptoms of congestive heart failure, proper administration and potential adverse effects of any maintenance medications, and management of the sternotomy incision. For patient education resources, see the Heart Health Center.

Maintain close follow-up care in young children after repair of truncus arteriosus. Young infants are often discharged on cardiac medications and may usually be weaned over the following months.

Frequently, a mild degree of regurgitation occurs through the right ventricle–to–pulmonary arterial conduit but, in most cases, does not pose a significant load on the heart.

In most patients, conduit regurgitation and obstruction becomes an important issue after early repair; small conduits are utilized and become relatively stenotic with somatic growth or simple degeneration.

Truncal valve regurgitation, which may progress even if it was not severe before repair, may become an important cause of persistent failure to thrive, and repair or replacement of the valve may be indicated.[15]

In patients with associated interruption of the aortic arch, pay particular attention to potential recurrent arch obstruction and compression of the bronchi, both of which may manifest within weeks or months of the initial repair.

Routine clinical and echocardiographic follow-up care is sufficient to monitor most patients. Cardiac catheterization may be performed for the purpose of balloon dilation, stenting, or both of the pulmonary arteries or pulmonary outflow conduit, for evaluation of the pulmonary vascular bed in patients who are older and have evidence of pulmonary hypertension, or for other diagnostic indications according to the preference of the physicians.

 

Medication

Medication Summary

Pharmacologic therapy in patients with truncus arteriosus depends on various factors, including clinical status, associated lesions, and where in the course of management (eg, preoperative, early postoperative) the patient is when drug therapy is provided. The major classes of cardiac drugs administered to patients with truncus arteriosus include diuretics, digoxin, afterload reducing agents, inotropic medications, and antiarrhythmics if necessary. Consultation with a cardiologist is imperative before beginning, changing, or discontinuing cardiac medications in these patients.

Inotropic agents

Class Summary

These agents provide inotropic and chronotropic support in the early postoperative period, when postoperative myocardial edema and ischemia-reperfusion injury may result in varying degrees of residual ventricular dysfunction. Also used at low doses to optimize renal perfusion to facilitate diuresis.

Dopamine (Intropin)

Stimulates adrenergic and dopaminergic receptors, with a predominant dopaminergic effect at low doses, beta-adrenergic and dopaminergic effects at intermediate doses, and primarily alpha-adrenergic effects at high doses.

Diuretic agents

Class Summary

These medications are used to mobilize edema in the early postoperative period and facilitate fluid homeostasis. They are also used for treatment of hypertension.

Furosemide (Lasix)

Increases excretion of water by interfering with chloride-binding cotransport system, which, in turn, inhibits sodium and chloride reabsorption in ascending loop of Henle and distal renal tubule.

Cardiac glycoside, antiarrhythmic

Class Summary

These agents are used to increase myocardial contractility, to slow atrioventricular node conduction time, and to potentiate the effects of furosemide.

Digoxin (Lanoxin, Lanoxicaps)

Acts directly on cardiac muscle, increasing myocardial systolic contractions. Its indirect actions result in increased carotid sinus nerve activity and enhanced sympathetic withdrawal for any given increase in mean arterial pressure.

ACE inhibitor, afterload reducing agent

Class Summary

These agents are used to decrease systemic vascular resistance, which is beneficial in patients with hypertension, impaired ventricular function, or aortic/truncal valve regurgitation.

Captopril (Capoten)

Inhibits activity of the angiotensin-converting enzyme, preventing conversion of angiotensin I to angiotensin II, which is a potent vasoconstrictor. Decreased levels of angiotensin II lead to increased plasma renin activity and decreased circulating aldosterone.