Truncus arteriosus

Definition

Truncus arteriosus (common arterial trunk, persistent truncus arteriosus, truncus arteriosus communis, common aorticopulmonary trunk) is a congenital cardiovascular malformation in which one great artery arising from the base of the heart by way of a single semilunar (truncal) valve gives origin to the coronary arteries, systemic arterial circulation, and one or two pulmonary arteries proximal to the origin of the brachiocephalic branches. It is one of several diagnoses within the phylum of common arterial trunk (see

International Paediatric and Congenital Cardiac Code

). A ventricular septal defect (VSD) is almost always present beneath the truncal valve.

This definition excludes those hearts in which there are no true pulmonary arteries and in which the lungs are supplied only by large aortopulmonary arteries (Collett and Edwards type IV ), characteristic of tetralogy of Fallot and pulmonary atresia with absence of the pulmonary trunk and the central and hilar portions of the right and left pulmonary arteries (see “ Morphology ” in Chapter 35 ). Common arterial trunk with an intact ventricular septum is exceedingly rare. Whether hearts in which there is a VSD but no interventricular communication during diastole (because the semilunar cusps close against the crest of the ventricular septum) should be considered to have an intact septum is controversial.

Historical note

The first well-documented case of truncus arteriosus was reported by Wilson in 1798, and existence of the entity was confirmed by accurate clinical and autopsy reports of a 6-month-old infant by Buchanan in 1864. In the early literature, there was frequent confusion with a single arterial trunk and, although Vievordt clarified this aspect in 1898 (quoted by Victoria and colleagues ), confusion existed as late as 1930 when Shapiro distinguished it from hearts with aortic and pulmonary atresia. Lev and Saphir proposed the basic morphologic criteria defining the anomaly in 1943, and in 1949, Collett and Edwards reviewed previously published cases and proposed a classification ( Box 43.1 ). An alternative classification was suggested by the Van Praaghs in 1965 ( Box 43.2 ).

• BOX 43.1

From Collett RW, Edwards JE. Persistent truncus arteriosus: a classification according to anatomic types. Surg Clin North Am . 1949;29:1245.

Classification Truncus Arteriosus

I.
Single pulmonary trunk
II.
Separate left and right pulmonary arteries arising close together
III.
Separate left and right pulmonary arteries arising from lateral aspect of truncus
IV.
Absent central pulmonary arteries; Aortopulmonary collaterals

• BOX 43.2

From Van Praagh R, Van Praagh S. The anatomy of common aorticopulmonary trunk (truncus arteriosus communis) and its embryonic implications. A study of 57 necropsy cases. Am J Cardiol . 1965;16:406.

Classification Truncus Arteriosus

Type A: With ventricular septal defect
Type B: Without ventricular septal defect
- 1.
  Partially separate main pulmonary artery
  - (Aorticopulmonary septum partially formed)
2.
Both pulmonary arteries arising directly from common trunk
- (No main pulmonary artery; Absent aorticopulmonary septum)
3.
Absence of either one pulmonary arterial branch
4.
Coarctation or interrupted aortic arch with a large patent ductus arteriosus

Surgical treatment was initially confined to banding of one or both pulmonary arteries. ^,

Intracardiac repair was first successfully accomplished in 1962 at the University of Michigan using a nonvalved Teflon conduit; the patient was alive and well 11 years later. Experimental work using ascending aortic allografts including the aortic valve was reported from Japan by Arai and colleagues in 1965 and by Rastelli and colleagues at the Mayo Clinic in 1967. Before this, in 1966, Ross and Somerville had successfully used an ascending aortic allograft in reconstructing tetralogy of Fallot with pulmonary atresia.

McGoon and colleagues were the first to successfully repair truncus arteriosus using an ascending aortic allograft and valve conduit (cylinder) in September 1967. ^, Bowman and colleagues used a glutaraldehyde-treated porcine aortic valve in a polyester cylinder in 1971, and Binet described a xenograft valve incorporated within a polyester cylinder in 1976 (see discussion of paper by Moore and colleagues ).

The first successful conduit repair in infancy was carried out in a 6-week-old infant by Barratt-Boyes in 1971, as reported by Girinath. In 1984, Ebert and colleagues at the University of California, San Francisco, reported complete repair in a series of 100 infants operated before the age of 6 months. Routine repair in neonates was reported at the 1992 Annual Meeting of the American Association for Thoracic Surgery by Hanley and Colleagues at Children’s Hospital of Boston and by Bove and colleagues at the University of Michigan. ^,

Morphogenesis and morphology

Morphogenesis

Deletion of chromosome 22q11 is present in a substantial number of patients with conotruncal abnormalities. About one-third of subjects with truncus arteriosus have been found to have 22q11 deletion, ^, and many of these have additional characteristic features of DiGeorge syndrome, velocardiofacial syndrome, or conotruncal face syndrome. As such, their natural history and also their course following operation may be complicated by hypocalcemia, palatal abnormalities, learning disability, and other noncardiac problems. Other chromosome abnormalities can be associated with truncus arteriosus, such as microdeletions of 8p23.1 and 18q11.2. Deletion of 8p23.1 harbors the gene GATA4 and 18q11.2, the gene GATA6. These transcription factors play important roles in cardiac development.

Morphology

Truncus arteriosus is traditionally classified based on origins of the pulmonary arteries from the truncal artery ( Box 43.1 ) and also on degree of development of the ascending aorta and ductus arteriosus in cases with a single pulmonary artery ( Box 43.2 ). A more recent categorization based on examination of 28 autopsy specimens classifies hearts as having either aortic or pulmonary dominance of the common arterial trunk. Hearts with aortic dominance have an unobstructed aortic arch; those with pulmonary dominance have aortic arch obstruction, either coarctation or interruption of the aortic arch. ^,

Arterial trunk.

The arterial trunk (truncal artery) is larger than a normal aorta and is the only vessel arising from the base of the heart. It originates in part from both ventricles, but usually is more over the right than left ventricle. In an autopsy series of 56 cases, the trunk was equally balanced over both ventricles in 50%. In the remainder, it was either exclusively or predominantly over the right ventricle in 40% and over the left ventricle in 10%. In the unbalanced cases, the VSD was much more likely to be smaller (both shallower and narrower). From the truncal artery arise the coronary arteries and one or both pulmonary arteries.

Pulmonary arteries.

The pulmonary arteries usually originate just downstream from the truncal valve on the left posterolateral aspect of the truncus artery, although their origin may lie truly laterally, truly posteriorly, or (rarely) anterolaterally ( Table 43.1 ). There is frequently a single orifice leading into a short pulmonary trunk (type I of Collett and Edwards), which then divides into left and right pulmonary arteries that follow a normal course ( Figs. 43.1 and 43.2 ). Alternatively and less commonly, the orifice is double, the left and right branches arising separately side by side ( Fig. 43.3 ) or occasionally with the orifice of the left pulmonary artery superior (anterior) to the right rather than to the left of it (type II of Collett and Edwards). Types I and II merge into each other and are best considered together, often being referred to in practice as “type 11/2.” They comprise the majority of cases ^, ^, ^, (89% of the Toronto surgical series, Table 43.1 ).

TABLE 43.1

Site of Origin of Pulmonary Arteries in Truncus Arteriosus ( n = 202)

Data from Williams JM, de Leeuw M, Black MD, Freedom RM, Williams WG, McCrindle BW. Factors associated with outcomes of persistent truncus arteriosus. J Am Coll Cardiol . 1999;34:545.

Site	No.	%
Single pulmonary trunk (I)	140	69
Separate left and right pulmonary artery orifices close together (II)	41	20
Separate orifices at lateral aspects of truncus (III)	14	7
Common pulmonary orifice without a common trunk	4	2
Other arrangement	3	1.5

A specimen from a neonate with truncus arteriosus shows labeled cardiac structures. The specimen shows an opened right ventricle with a thick muscular wall visible along the cut edges. The truncal region is seen above, with the label R P A on a vessel to the upper left and the label L P A on a vessel to the upper right. The label T r V is positioned above a central opening, and the label V S D marks an opening immediately below it. A ridge labeled R P D extends between the V S D and the area labeled T V, which is positioned lower and to the left. The label R V is placed on the ventricular chamber at the bottom of the specimen. — • Figure 43.1

A specimen shows truncus arteriosus with a widely opened truncal artery and labeled pulmonary artery branches. The specimen shows an opened arterial trunk with two circular branch openings, with the right pulmonary artery labeled R P A on the left side of the image and the left pulmonary artery labeled L P A on the right side. A ridge-like structure forming a carina is visible between the two pulmonary artery openings along the inner wall of the truncal artery. In the lower central region, a valve structure labeled T r V is visible within the truncal artery, with multiple leaflet margins apparent. Surrounding myocardial and vascular tissue contours frame the opened arterial structure and labeled features. — • Figure 43.3

Rarely, the ostia of left and right pulmonary arteries may be widely separated and arise from opposite lateral walls of the truncal artery at either the same or different levels above the valve (type III of Collett and Edwards). This arrangement poses special problems for repair.

Occasionally, only one pulmonary artery originates from the truncal artery. The arterial vascular supply to the opposite lung arises either from a patent ductus arteriosus as a complete branch pulmonary artery or from large aortopulmonary collateral arteries, as in tetralogy of Fallot with pulmonary atresia. When the left pulmonary artery is the one that does not originate from the truncus (or is absent), the right often continues to arise from the left posterolateral surface of the proximal truncal artery. ^, The term hemitruncus has been used to describe the condition of the common arterial trunk giving rise to only one branch pulmonary artery, but the term is more commonly used to describe the slightly more common “origin of right (or left) pulmonary artery from the aorta.” In the latter, of course, there are two separate semilunar valves (see Chapter 42 ).

Stenosis of the origin of one or both branch pulmonary arteries is more frequent than absence of the origin; it is probably underestimated in autopsy compared with cineangiographic studies. It was noted in five clinical cases (10%) in one series.

Ascending aorta and ductus arteriosus.

In truncus arteriosus, there is reciprocal development between ascending and transverse aortic arches (arising from fourth aortic arch) and ductus arteriosus (arising from sixth aortic arch). Thus, in the majority of cases the ascending aorta is a direct continuation of the truncus artery and of about the same diameter (see Fig. 43.1 ), whereas the ductus arteriosus is usually entirely absent. Rarely a ductus is present with a well-developed arch.

By contrast, when the ductus arteriosus is present, the transverse arch is usually absent (interrupted aortic arch) and the ascending aorta is underdeveloped. The ductus is a direct continuation of the truncus artery, arching leftward to join the descending aorta ( Fig. 43.4 ). In this situation, left and right pulmonary artery branches usually arise separately from superior and inferior (leftward and rightward) walls of the truncal artery (type III of Collett and Edwards). The ascending aorta now arises from the superior rightward aspect of the truncus artery as the relatively smaller branch. Usually the transverse aorta is interrupted beyond the origin of the left common carotid artery (type B interrupted aortic arch; see “ Types ” under Morphology in Section II of Chapter 40 ), or there is severe coarctation including tubular hypoplasia of the aortic isthmus and arch (see Fig. 43.4 ). This arrangement (Van Praagh type A4) was present in 12% of the cases of Van Praagh and colleagues and 14% (28 of 202) of the Toronto surgical series. ^,

A specimen shows truncus arteriosus with labeled great vessels and branches. The specimen shows an opened truncal artery labeled T r in the lower portion, surrounded by cardiac tissue. Near the upper left, a vessel labeled Brach extends upward. Slightly below and to the left, a vessel is labeled R P A. In the upper central area, a large vertical vessel is labeled A s A. To the right of this, two upward branches are labeled L C C and L S C. Beneath these branches, a tubular structure descending downward is labeled D, representing a large ductus arteriosus. On the far right upper side, a vessel is labeled Desc A o. Toward the lower right, a branching vessel is labeled L P A. — • Figure 43.4

Coronary arteries.

Orifices of the coronary arteries have a variable relationship to the sinuses of Valsalva above the truncal cusps ( Fig. 43.5 ). A minority (≈20%) arise centrally (more or less normally) within the sinuses; about 80% (whether the usual two or a single orifice) are at the margin of the sinus or at the upper margin of a commissure. In at least a third of cases, one coronary orifice (usually the left) is displaced cephalad above the sinutubular ridge and must be differentiated from the pulmonary artery orifices at the time of repair. In about two-thirds of cases, the left coronary artery arises from the left posterior aspect of the truncal artery, and the right coronary artery from the right anterior aspect in a position similar to normal. ^, Deviations from this pattern occur in the remainder of cases and include a single ostium (found in 18% of hearts reported by de la Cruz and colleagues ), closely approximated right and left ostia, and small, slit-like, or stenotic and kinked proximal left coronary artery. ^, ^, ^, ^, ^,

An illustration shows truncus arteriosus with circular schematic representations of trunk position and coronary artery ostial variations. The illustration shows a large central circle labeled P T with the value 296, representing the reference position, surrounded by multiple smaller circles arranged around it. Circles labeled L A with the value 89, D A with the value 148, R A with the value 42, and L L with the value 17 are positioned around the central circle. Each surrounding circle contains internal segment lines and clusters of dots. Additional circles above and to the sides include circles labeled with values 21, 105, 24, 1, 63, 6, 22, 20, 10, 2, 5, and 17. Along the lower portion, circles labeled Bicuspid with the value 38, Tricuspid with the value 194, and Quadricuspid with the value 194 are shown. Closed dots within the circles indicate left or right coronary artery ostial positions, and open dots indicate single coronary artery ostial positions. An orientation marker on the right shows arrows labeled Left and Anterior, indicating viewing direction. — • Figure 43.5

Rarely, a coronary artery may arise from a pulmonary artery rather than the truncal artery; Daskalopoulos and colleagues report the circumflex artery’s origin from the right pulmonary artery in a patient in whom pulmonary artery banding was not tolerated. The proximal part of the left anterior descending coronary artery is frequently displaced to the left of the interventricular sulcus and does not reach it until about halfway down the front of the heart. It tends to be small. Larger-than-normal diagonal branches from the right coronary artery cross the anterior right ventricle inferior to conal branches, contributing to the blood supply of the upper interventricular septum and occasionally part of the left ventricle. ^, Damage to these vessels during surgical repair can seriously compromise the myocardium.

Truncal valve.

The single truncal valve is posterior and inferior in position, similar to the normal aortic valve, although it points more anteriorly. There is fibrous continuity between its posterior cusps and the anterior mitral leaflet, as in the normal heart ( Fig. 43.6 ). It has three cusps in half to two-thirds of cases, and four cusps in most of the remainder. Rarely, the valve is bicuspid. Not infrequently, a raphe is present and partially divides a cusp into two, but it is doubtful whether there are ever more than four well-formed cusps. There may be variations in length and width of individual cusps, but in most patients who survive infancy, the cusps are well formed (see Figs. 43.2 and 43.6 ). However, in all cases, details of the structure of the truncal valve are different from those of the normal aortic valve.

A specimen from a neonate with truncus arteriosus shows labeled cardiac structures. The specimen shows the opened left ventricle labeled L V in the lower portion, with a ventricular septal defect labeled V S D located just above it. In the upper central region, four truncal valve cusps are visible and labeled P, R, N, and L, indicating a quadricuspid truncal valve. The label M V marks the mitral valve tissue positioned adjacent to the truncal valve cusps. Two vessels arise superiorly, with the right pulmonary artery labeled R P A and the left pulmonary artery labeled L P A. The opened cardiac interior, surrounding tissue surfaces, and cut edges are visible around the labeled structures. — • Figure 43.6

A specimen shows truncus arteriosus with labels P A, L, R, V S D, L A D, S, R P D, V I F, and T V. The specimen shows the truncus arteriosus viewed from an opened right ventricle and truncal region. At the top, an arterial opening is marked P A. In the upper central region, cusps of the truncal valve are visible, with the left cusp labeled L and the right cusp labeled R. Below these cusps, an opening along the septal margin is labeled V S D, representing a ventricular septal defect. Toward the upper right, a band-like structure carries the label L A D. In the central portion, a prominent muscular ridge is marked S. On the lower right side, a posteriorly directed division is labeled R P D. On the lower left side, a folded muscular structure is labeled V I F. At the lower left margin, the tricuspid valve region is labeled T V. — • Figure 43.2

In autopsy material, obvious severe myxomatous thickening of the cusps is present in a third of cases and is much more common in those dying as neonates ( Fig. 43.7 ) ( Fig. 43.8 ). Less severe myxomatous changes are present in two-thirds of older infants, and microscopic increase in thickness of the distal portions of the cusps is apparent in many. Severe myxomatous changes often are associated with severe truncal valve regurgitation, and their frequency in autopsy specimens from neonates and young infants corresponds to the high prevalence of truncal valve regurgitation in neonates and young infants who develop severe heart failure or die. These morphologic changes are also reminiscent of those seen in congenital valvar aortic stenosis in the neonate (see Chapter 50 ) and may make the valve stenotic. Rarely, stenosis is contributed to by commissural fusion. A redundant truncal valve leaflet may obstruct the pulmonary trunk ostium during ventricular ejection when the ostium is proximally placed.

A specimen shows truncus arteriosus with labels C i r c and R C A. The specimen shows the truncal valve viewed from above, with four markedly irregular cusp surfaces arranged around a central opening. The cusps appear thickened, bulky, and uneven, forming a crowded valve orifice. At the upper central edge, a label marks C i r c above a vessel segment, and at the lower left side, a label marks R C A adjacent to a branching structure. The interior valve surfaces show nodular, lobulated tissue contours, and the surrounding margins show cut and folded tissue. — • Figure 43.7

A specimen shows truncus arteriosus with the truncal artery and right ventricle opened and multiple labeled internal structures visible. The specimen shows the opened truncal outflow and right ventricular cavity, with the upper central vessel labeled A o and the pulmonary artery origin labeled P A to the right. Within the truncal valve region, two cusps are labeled R and L, with the cusps appearing thickened and irregular. Below the cusps, a narrow muscular ridge is visible between the truncal valve region and the tricuspid valve, labeled T V. A band-like structure labeled S extends across the ventricular cavity, with its divisions labeled L A D and R P D. A broad fold on the left side is labeled V I F. The right ventricle is labeled R V at the lower margin, and surrounding myocardial surfaces and trabeculations are exposed across the opened specimen. — • Figure 43.8

Ventricular septal defect.

The VSD is high, anterior, usually large, and juxtatruncal in position. It is typically stated that the truncal valve forms its superior margin (see Figs. 43.2 and 43.6 ). Consistent with this observation is the fact that the infundibular septum is absent in truncus arteriosus, so there is no infundibular structure to form the superior margin of the VSD, leaving the superior margin to be formed by the valve itself. Another way to characterize the VSD is to describe it as U-shaped , that is, with no superior margin. This perspective can be best appreciated if one examines a specimen with the truncal valve leaflets opened to the position they occupy during systole. Inferiorly and anteriorly, the VSD is bounded by the two divisions of the trabecula septomarginalis (septal band) and posteriorly by the free wall muscle band that separates the semilunar from the tricuspid valve (the ventriculoinfundibular fold) (see Fig. 43.2 ).

Usually the junction of the right posterior division of the trabecula septomarginalis and the ventriculoinfundibular fold form a muscle bridge that separates the defect from the tricuspid valve and right trigone (see Fig. 43.1 ) and therefore from the bundle of His. ^, ^, ^, Occasionally, this muscle bridge is absent (see Fig. 43.2 ) or poorly formed (see Fig. 43.8 ); the lower margin of the defect then approaches the tricuspid anulus, or the VSD becomes juxtatricuspid in position, in which case the His bundle is at risk of damage during repair. In these hearts, there may be fibrous truncal-tricuspid-mitral valve continuity. Part of the membranous ventricular septum may still be present at the posteroinferior margin of the VSD.

Right ventricle.

The infundibular (conal) septum is absent from the right ventricular outflow tract. ^, Contrariwise, it has been asserted that the infundibular septum can be recognized fused to the distal anterior (free) right ventricular wall; rarely, there is a persistent blind right ventricular outflow pouch in front of it. The right ventricle is nearly always hypertrophied and enlarged.

Left ventricle.

In contrast to the right ventricular outflow tract, the left ventricular outflow tract is relatively normal in hearts with truncus arteriosus (see Fig. 43.6 ), and flow from this chamber into the truncal artery is restricted only in the unusual situation when the truncal artery originates mainly from the right ventricle and the VSD is small. A pressure gradient from left ventricle to aorta in such rare instances will lie at the VSD level rather than at the truncal valve. Although a moderate-sized VSD is not restrictive before surgical repair, it may prove so afterward and thus may need to be enlarged at operation, although this situation is rare (see “ Technique of Operation ” later).

Associated anomalies.

A VSD is almost always present. The most common associated cardiac and noncardiac anomalies are shown in Tables 43.2 and 43.3 . About 10% to 20% of patients with truncus arteriosus have coexisting interrupted aortic arch or coarctation with patency of the ductus arteriosus. ^, Truncus arteriosus is rarely associated with atrioventricular discordant connection, situs inversus, asplenia or polysplenia, or dextrocardia. Double inlet ventricle is also rare, although mitral stenosis or atresia with left ventricular hypoplasia occurs.

TABLE 43.2

Associated Congenital Anomalies in Truncus Arteriosus Communis Patients

Adapted from Kalavrouziotis G, Purohit M, Ciotti G, Corno AF, Pozzi M. Truncus arteriosus communis: early and midterm results of early primary repair. Ann Thorac Surg . 2006;82:2200-2206.

Anomaly	No. of Patients	Percent
Cardiac
VSD	29	100
Truncal valve, regurgitation (mild/moderate)	15 (9/5)	52
Truncal valve, stenosis (mild/moderate)	8 (6/2)	28
Secundum ASD/PFO	11	38
Right aortic arch	7	24
Coronary anomalies	4	14
Persistent LSVC	3	10
IAA:	2	7
Type A	1
Type B	1
PDA	2	7
Noncardiac
DiGeorge syndrome	9	31
Hypocalcemia	3	10
von Willebrand disease	2	7
Hypothyroidism	1	3
Esophageal atresia + tracheoesophageal fistula	1	3
Anovestibular fistula	1	3
Other	4	14

Total patients = 29.

ASD, Atrial septal defect; IAA, interrupted aortic arch; LSVC, left superior vena cava; PDA, patent ductus arteriosus; PFO, patent foramen ovale; VSD, ventricular septal defect.

TABLE 43.3

Associated Congenital Cardiovascular Anomalies

From Brown JW, Ruzmetov M, Okada Y, Vijay P, Turrentine MW. Truncus arteriosus repair: outcomes, risk factors, reoperation and management. Eur J Cardiothorac Surg . 2001;20:221-227.

	PATIENTS
Anomaly	Number	Percentage
Major
Truncal stenosis/regurgitation (severe)	7	12
IAA	6	10
Non-confluent pulmonary arteries	4	7
TAPVR	1	2
Minor
Secundum ASD/PFO	15	25
Other (right aortic arch, coarctation, anomalous systemic-venous connection, DiGeorge syndrome	13	22
Other than three truncal leaflets	15	25
Coronary anomaly	6	10

Total patients = 60.

ASD, Atrial septal defect; IAA, interrupted aortic arch; PFO, patent foramen ovale; TAPVR, total anomalous pulmonary venous return.

Frequent total absence of the ductus arteriosus has already been mentioned together with association of a widely patent ductus arteriosus in patients in whom there is also aortic arch interruption or, less often, aortic coarctation or atresia. When hearts with aortic arch interruption are excluded, right aortic arch is as common in truncus arteriosus as in tetralogy of Fallot (25%–35%). ^, Anomalous aortic branch origins occur frequently, usually of the subclavian arteries (10%). A persistent left superior vena cava drains to the coronary sinus in about 10% of patients, and occasionally there is partial anomalous pulmonary venous connection. Patent foramen ovale is common, and atrial septal defect of moderate or large size is found in 10% to 20% of patients. Mitral valve anomalies of various types are present with similar frequency. Other rare lesions include atrioventricular septal defect, double aortic arch, and according to Bharati and colleagues, tricuspid stenosis and (rarely) atresia.

Extracardiac congenital defects are not uncommon and may occasionally contribute to death. DiGeorge syndrome (thymic and parathyroid aplasia or hypoplasia) is known to be associated with truncus arteriosus.

Clinical features and diagnostic criteria

Symptoms

Presenting symptoms are almost always tachypnea, tachycardia, irritability, and unwillingness to take either breast or bottle feedings during the early weeks of life, all manifestations of heart failure. Rarely, respiratory distress is aggravated by compression of the left upper lobe bronchus between an anteriorly placed left pulmonary artery and the posterior aortic arch. ^, Mild cyanosis accompanies these symptoms in about one third of cases but rarely is the presenting feature. Rapid progression of heart failure after birth may occasionally result in either necrotizing enterocolitis or cardiovascular collapse. By contrast, in those infants who survive for longer periods, recurrent respiratory infections, dyspnea, and failure to thrive are usually present, and cyanosis is more apparent secondary to rising pulmonary vascular resistance. Older children may occasionally present with increasing cyanosis (Eisenmenger syndrome) and fail to give a history of heart failure in infancy.

Physical examination

On examination, signs of heart failure are accompanied by a jerky to collapsing arterial pulse produced by rapid runoff from the truncal artery into the pulmonary arteries. The heart is overactive, and a prominent left parasternal systolic murmur and often thrill are appreciated. There is frequently an ejection click coinciding with full opening of the truncal valve, and an apical gallop rhythm may be present, although it is surprisingly rare in neonates. An aortic early diastolic murmur (from truncal valve regurgitation) is highly suggestive of truncus arteriosus, particularly when it is accompanied by pulmonary plethora on chest radiograph and right aortic arch. A continuous murmur is noted occasionally and is most often due to stenosis at the origin of one or both pulmonary arteries. Important truncal valve stenosis is a confusing feature and usually results in diminished peripheral pulses accompanied by a harsh ejection systolic murmur and thrill, maximal in the right upper intercostal spaces. ^,

Chest radiography

Chest radiography shows marked cardiomegaly as well as plethoric lung fields in neonates and infants. The pulmonary trunk segment is deficient (as in transposition), but a high origin or arching of the left pulmonary artery may be evident in older children as a “comma” sign on the left upper mediastinal border. A solitary right pulmonary artery arising from the left side of the truncus artery may give a similar appearance. The hemithorax may be smaller and vascularity less on the side of the “absent” branch pulmonary artery (when this lung is supplied by bronchial collaterals or by a relatively small patent ductus arteriosus). In truncus arteriosus with aortic arch interruption, the descending aorta is often prominent in the chest radiograph. In those few infants who survive without treatment, pulmonary plethora subsides, as does cardiomegaly, from increasing pulmonary vascular disease.

Electrocardiography

Electrocardiography (ECG) usually shows combined ventricular hypertrophy and a normal or slightly rightward axis, although left ventricular hypertrophy is usually dominant in the tracing (occasionally it is absent). P pulmonale can occur.

Echocardiography

Transthoracic echocardiography is the diagnostic modality of choice. It is usually definitive, with infrequent occurrence of only minor errors ( Fig. 43.9 ). The primary echocardiographic findings are a single vessel overriding the ventricular septum and a large outlet VSD. ^, ^, Echocardiography can also accurately demonstrate the origins of the pulmonary arteries, the morphology and function of the truncal valve, the presence of abnormalities of the aortic arch, including interrupted aortic arch, as well as other associated abnormalities. The origins and early courses of the coronary arteries are often seen. Intracardiac findings on echocardiography may be similar to those in tetralogy of Fallot with pulmonary atresia; the anatomic details, in particular the morphology of the truncal valve and the origins of the pulmonary arteries, allow the two diagnoses to be distinguished. In current practice, more than 90% of cases can be detected by prenatal echocardiography.

A scan shows truncus arteriosus in a parasternal long-axis echocardiographic view with multiple labeled structures. The scan shows the upper portion labeled Thymus, beneath which a chamber is labeled R V. Small arrows point to a thickened truncal valve labeled T r located above a crest labeled S. Above the septal crest and below the truncal valve, a defect is visible. To the right of the truncal valve, vessels are labeled A and A o, with a curved structure on the far right labeled A R C H, and large arrows pointing toward the arch branches. In the lower portion, the left ventricle is labeled L V with the left atrium labeled L A adjacent to it. A branching vessel exiting from the trunk is labeled L P A. The scan includes multiple directional arrows, grayscale cardiac structures, and an electrocardiographic trace along the bottom edge. — • Figure 43.9

Computed tomography angiography and magnetic resonance imaging

In the majority of cases, echocardiography alone is sufficient for diagnosis and preoperative planning. CT angiography (CTA) and MRI are not routinely indicated, but these imaging modalities may be useful in specific circumstances in both neonates and older children. CTA provides excellent spatial resolution ( Figs. 43.10 and 43.11 ). When echocardiography provides inadequate information on pulmonary artery, aortic arch, or coronary artery anatomy, CTA can define the morphologic details. MRI can quantify the regurgitant fraction of an abnormal truncal valve, providing objective data for longitudinal follow-up and decision-making ( Fig. 43.12 ).

A set of panels shows truncus arteriosus in volume-rendered computed tomography images with multiple labeled vessels and orientation markers. The set of panels shows three volume-rendered C T views, with panel A on the upper left presenting an anterior view marked with orientation letters P, R, L, and A around the margins. In panel A, the right pulmonary artery, labeled R P A, and the left pulmonary artery, labeled L P A, are seen arising above a rounded central opening labeled T R, with a vessel labeled M P A extending inferiorly. Panel B on the upper right shows a similar anterior view with R P A and L P A labeled on either side of the central opening labeled T R, and orientation letters P, R, L, and A placed around the image. Panel C below shows a different view with the ascending aorta labeled A A near the upper region, the right pulmonary artery labeled R P A, the truncal root labeled T R, a branching vessel labeled P D A, and the left pulmonary artery labeled L P A below, with orientation letters H, A, F, and P positioned around the outer edges. — • Figure 43.10

A computed tomography volume-rendered angiogram shows the truncal root and great vessels in a heart with truncus. The computed tomography volume-rendered angiogram shows a tall central vessel labeled A o rising superiorly, with a branch labeled R P A arising from the truncal root and extending toward the right side. An arrow points to the left side of the truncal root where no comparable branching vessel is seen. The R P A is positioned posterior to the ascending aorta, and the surrounding three-dimensional surface anatomy of the heart and great vessels is visible. — • Figure 43.11

A scan shows a rounded cardiac chamber with a valve region at the top and an arrow pointing to a narrow jet extending downward into the chamber. — • Figure 43.12

Cardiac catheterization and angiography

In current practice, echocardiography and cross-sectional imaging completely define the anatomic details, and cardiac catheterization is rarely performed in neonates and young infants. In the occasional patient, cardiac catheterization with angiography may still be useful to define the hemodynamic state when there is an atypical physiologic presentation, such as severe cyanosis, or when there is suspicion that the pulmonary artery morphology is complex (e.g., unilateral aortopulmonary collaterals). Should one pulmonary artery fail to outline after routine contrast injections, the origin and distribution of the blood supply to the other lung must be identified. This is usually possible by injections into the upper descending thoracic aorta and its branches, defining either a ductus or large collaterals. In addition, a pulmonary vein wedge injection can be used to retrogradely fill true pulmonary arteries that fill either inadequately or not at all from an aortic injection.

Cardiac catheterization remains important in patients who present after 6 months of life to define the status of the pulmonary microvasculature. In neonates and young infants with typical physiology, there is left-to-right shunting at both the ventricular and great vessel level with diastolic runoff into the pulmonary arteries, a high pulmonary-to-systemic blood flow ratio (Qp/Qs), and systemic pressures in the right ventricle and pulmonary arteries. The high pulmonary blood flow keeps aortic oxygen saturation at 85% or more. Pulmonary vascular resistance is mildly elevated (2-4 units · m ²). The progressive rise in pulmonary vascular resistance that occurs in virtually all children who survive infancy is associated with a fall in Qp and therefore in arterial oxygen saturation. Arterial oxygen saturations less than 85% may be an indication that pulmonary vascular resistance is beyond the operable range.

Natural history

Truncus arteriosus is rare, occurring in 2.8% of cases of congenital heart disease in the cardiac registry report by Calder and colleagues and in 1.7% of the autopsy series of Tandon and colleagues. The natural history of patients with truncus arteriosus is unfavorable. No series has followed a cohort of patients from birth, so exact data are not available. However, several studies when taken in aggregate provide an accurate estimate of survival without surgical treatment. Marcelletti and colleagues reported in 1976 on 23 cases prior to the era of corrective operations. All ten patients presenting before the age of 1 year died. ( Table 43.4 ). Eight patients presented between 1 and 7 years of age and all were living except one. Five patients were older than 7 years and all had severe pulmonary vascular obstructive disease. In total, 14 of 23 patients have died. At the time of the study, the survivors had congestive heart failure polycythemia, and/or pulmonary hypertension. Additional reports of autopsy cases by Calder and the Van Praaghs, ^, Collett, Edwards, and colleagues, ^, and Bharati, Lev, and colleagues imply similar mortality to the Marcelletti report. In two reports, the median age of death was 5 weeks, ^, and in another, two-thirds were dead before reaching age 6 months. Bharati and colleagues report a mean age of death of 6 months in 177 cases. Other isolated case reports confirm that some subjects, perhaps 10%, survive into adolescence or young adult life but usually with severe pulmonary vascular disease.

TABLE 43.4

Natural History of Truncus Arteriosus for Patients Presenting before Age 1 Year

Adapted from Marcelletti C, McGoon DC, Mair DD. The natural history of truncus arteriosus. Circulation . 1976;54:108.

							DEATH
Case	Sex, Age at Diagnosis	Symptoms	Systemic O ₂ Sat., %	Systemic Arterial Pressure, mm Hg	Rp, U m ²	Associated Defects	Time after 1st Exam	Cause
1	F, 8 days	HF, C	89	—		—	10 days	HF
2	F, 2 mo	HF	90	85		—	Few days	HF
3	F, 2 mo	HF	—	—		—	Few days	HF
4	F, 3 mo	HF	—	—		—	Few days	HF
5	F, 5 mo	HF	80	80		Mild TVR	1 ¹ ⁄ ₁₂ yr	HF
6	F, 6 mo	HF	82	84		—	8 ¹ ⁄ ₂ yr	HF
7	F, 6 mo	HF	92	73	1.4	PDA, ASD	2 mo	Ventricular and tachyarrhythmias
8	M, 8 mo	HF	90	—		—	Few days	HF
9	F, 1 yr	HF, C	86	80		PDA, tricuspid regurg., LPA absent	1 mo	HF
10	M, 1 yr	Asymp.	91	88	7.0	—	12 yr	ARI

ARI, Acute respiratory infection; ASD, atrial septal defect; Asymp., asymptomatic; C, cyanosis; HF, heart failure; LPA, left pulmonary artery; PDA, patent ductus arteriosus; Rp, pulmonary resistance; Sat., saturation; TVR, truncal valve regurgitation.

Based on all these reports, about 50% of those born with this condition survive beyond the first month of life, 30% beyond 3 months, 15% beyond 6 months, and 10% beyond 1 year. There is little further mortality beyond this age until pulmonary vascular disease becomes severe and death occurs with Eisenmenger syndrome in about the third decade of life. Death in infancy is invariably due to heart failure, and when it occurs in the neonatal period, severe truncal valve regurgitation and large left-to-right shunt play contributing roles. The situation may be compounded by severe respiratory infection, as in other malformations with large left-to-right shunts in early life.

Longer-term survivors may occasionally succumb from infective endocarditis or cerebral abscess, but most eventually die from consequences of severe pulmonary vascular disease (see “ Pulmonary Vascular Disease ” under Natural History in Section I of Chapter 33 ). When pulmonary vascular disease develops during the first year of life or later (and it typically develops more rapidly than in patients with isolated VSD ), the patient has a good chance of surviving at least into the teens, as is usually the case with Eisenmenger syndrome. Thus 7 of 10 Mayo Clinic patients with pulmonary vascular resistance greater than 8 units · m ² at diagnosis before 1 year of age were alive (without treatment) 1 to 15 years (average 8.3 years) later.

Rather remarkably, a few patients survive infancy and early childhood without developing severe pulmonary vascular disease despite large left-to-right shunts. These patients probably represent less than half of those surviving beyond 1 year of age and less than 5% of all those born with truncus arteriosus.

Survival is adversely affected by severe truncal valve regurgitation, as noted earlier, or by truncal valve stenosis. Even in older patients, truncal valve regurgitation is present in 60% to 70% of cases. Regurgitation may be predominantly into the right ventricle. Survival is also adversely affected by coexisting interrupted aortic arch or coarctation. Survival is also less favorable when there are other associated severe lesions such as left ventricular hypoplasia and a small or atretic mitral valve, complete atrioventricular septal defect, or serious extracardiac anomalies.

Survival is favorably affected by pulmonary stenosis (narrowing at the origins of the pulmonary trunk or right or left pulmonary arteries). Four of the first 28 (14%) truncus patients repaired beyond infancy at the Mayo Clinic had naturally occurring pulmonary artery stenosis.

Special features of preoperative care

A recent consensus document on optimal management of patients with truncus arteriosus covers recommendations for preoperative care. Prenatal diagnosis allows delivery in a tertiary care center and avoidance of long-distance transport. Care should optimally be delivered in a center with comprehensive capabilities in all the areas essential to complex congenital heart surgery. The preoperative period should be limited in extent (see subsequent section on Indications for Operation ). Emphasis should be on obtaining expeditious, complete, and accurate diagnostic studies, appropriate counseling for the family, and stabilization as needed. As in any neonate with parallel systemic and pulmonary circulations, interventions that might promote pulmonary overcirculation (such as inspired O ₂ concentration above room air, or hyperventilation) should be avoided.

Technique of operation

Repair is usually performed during mildly to moderately hypothermic cardiopulmonary bypass (CPB) using a distally placed aortic cannula, one right atrial or two vena caval cannulae, and a left-sided vent placed through the right upper pulmonary vein. Although there is no technical reason to use deep hypothermia with either low-flow CPB or circulatory arrest, some surgeons prefer it, in particular for the closure of the ASD and VSD in low weight neonates. The branch pulmonary arteries are exposed and temporarily occluded with either nontraumatic microvascular clips or snares immediately after CPB is established.

Ideally, myocardial management is accomplished with cold blood cardioplegia using antegrade cardioplegia infused directly into the truncal root (also while the branch pulmonary arteries are occluded). When moderate or severe truncal regurgitation is present, the patient is cooled on CPB to the target temperature (or until ventricular fibrillation occurs spontaneously), the truncal root is clamped and opened, and cardioplegia is delivered directly into the coronary ostia (see “ Methods of Myocardial Management during Cardiac Surgery ” in Chapter 3 ). Alternatively, retrograde cardioplegia may be used in the presence of significant truncal regurgitation. Surgeon preference and morphologic findings may dictate other combinations.

Repair with allograft aortic or pulmonary valved conduit

Following primary median sternotomy, a piece of pericardium may be taken and laid aside in a moist sponge. The proper-sized allograft aortic or pulmonary valved conduit (10–12 mm for a neonate, 12–14 mm for an infant) is selected, and its processing for insertion is begun.

Left and right pulmonary arteries are dissected in preparation for immediate temporary occlusion at the institution of CPB, as described earlier. The usual purse-string sutures are placed (see “ Preparation for Cardiopulmonary Bypass ” in Section III of Chapter 2 ), positioning the one for aortic cannulation as far downstream as possible so that the aortic clamp (placed proximal, or upstream, to the cannula) will be as far distal as possible on the ascending aorta. Alternatively, direct arterial cannulation of either the brachiocephalic artery or proximal aortic arch may be used if the ascending aorta is short, or as a routine.

Once CPB has been established and the pulmonary arteries controlled, cooling to the target core temperature is accomplished. The aorta is clamped and cardioplegia delivered. Snares on the pulmonary arteries are released, and repair is begun. The pulmonary trunk origin is detached from the truncal artery ( Fig. 43.13 A-B); in truncus type II, an appropriate ellipse of truncal wall is included in the excision. The incision for detachment is begun anteriorly, typically only several millimeters distal to the sinutubular junction of the truncal valve. The incision is initially made only large enough so that the interior of the truncal artery and valve, ostia of the coronary arteries, and orifices of right and left pulmonary arteries can be directly visualized. High origin of the left coronary artery should be distinguished from a pulmonary artery orifice. Detachment is then completed while viewing all these structures from within. Complete transection of the truncal root may be used to facilitate branch pulmonary artery detachment in the setting of truncus type II or as a routine. While the truncal root is open, a site for the right ventriculotomy is selected by looking down through the truncal valve, selecting a site inferior to the insertion of the valve, and marking the site externally. This method avoids damage to the truncal valve during subsequent performance of the ventriculotomy. The truncal valve inserts in the right ventricular outflow tract more inferiorly than is obvious from external inspection and is at risk during blind performance of the ventriculotomy. The truncal root is then directly reconstructed with one or two layers of continuous 6-0 or 7-0 polypropylene sutures. When used, the second layer brings adventitia over the first layer. This is done carefully to avoid distorting the coronary arteries or the truncal valve. A patch is often used at the site of pulmonary artery detachment if direct repair risks distortion.

A set of five surgical illustrations shows sequential stages in the repair of truncus arteriosus using an allograft valve cylinder. The set of five surgical illustrations is labeled A to E. In panel A, the great vessels and right ventricle are exposed, with labels identifying the truncus, pulmonary trunk branches including L P A and R P A, the superior vena cava S V C, inferior vena cava I V C, and right ventricle R V. A dashed line is visible on the right ventricular surface indicating a proposed vertical ventriculotomy. In panel B, the pulmonary trunk has been separated from the truncal artery, with a suture line visible on the truncal side and an opening labeled V S D on the ventricular wall adjacent to the pulmonary trunk bifurcation. In panel C, an open right ventriculotomy is shown with a V S D patch sutured into place, and the Bundle of His labeled along a narrow muscular ridge beneath the patch. In panel D, a cylindrical allograft valved conduit is attached to the pulmonary trunk bifurcation, with the V S D patch visible within the ventricular cavity adjacent to the conduit. In panel E, the completed reconstruction is shown, with the pulmonary trunk connected to the conduit, the right ventricle labeled R V, along with the aorta, forming the final repaired configuration.

Tags: Christian Kreutzer, Kirklin/Barratt-Boyes Cardiac Surgery, Scott M. Bradley

Apr 21, 2026 | Posted by drzezo in CARDIAC SURGERY | Comments Off

Thoracic Key

Fastest Thoracic Insight Engine

Truncus arteriosus

Definition

Historical note

Classification Truncus Arteriosus

Classification Truncus Arteriosus