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1. Truncus Arteriosus
Allison K. Cabalka MD
William D. Edwards MD
Joseph A. Dearani MD
Persistent truncus arteriosus is an uncommon congenital cardiovascular
malformation. There is not a striking gender difference in frequency, although most
series contained more male than female subjects. Truncus arteriosus usually occurs as
an isolated cardiovascular malformation, although on occasion it has been reported in
association with anomalies of other systems, particularly the DiGeorge or
velocardiofacial syndrome (microdeletion chromosome 22q11.2). Maternal diabetes has
been implicated as a risk factor for truncus arteriosus. The anomaly has occurred in
dizygotic twins and siblings, and there is an increased incidence of cardiac
malformations in relatives of children with this lesion. Because corrective operation for
this malformation was first performed more than 30 years ago, an ever-increasing
number of postoperative patients is now reaching adolescence and adulthood. Patients
who have had truncus arteriosus corrected need continued follow-up care throughout
life. During the last 25 years, surgical correction of truncus arteriosus during infancy
has become routine.
Embryology
The embryonic truncus arteriosus lies between the conus cordis proximally and
the aortic sac and aortic arch system distally. Partitioning of the truncus arteriosus,
which is intimately associated with conal and aortopulmonary septation, was reviewed
by Van Mierop et al. and more recently by Bartelings and Gittenberger-de Groot.
Truncus swellings, similar in appearance to endocardial cushions, divide the truncal
lumen into two channels: The proximal ascending aorta and the pulmonary trunk. As
the proximal portion of this truncal septum fuses with the developing conal septum
(derived from conal swellings), the right ventricular origin of the pulmonary trunk and
the left ventricular origin of the aorta are established. Valve swellings develop from
truncal tissue at this line of fusion, and the excavation of these swellings leads to
formation of the aortic and pulmonary valves in their respective sinuses. Along the
aortic sac, the paired sixth aortic arches (primitive pulmonary arteries) migrate leftward,
and the paired fourth aortic arches shift rightward. Invagination of the aortic sac roof
thereby forms an aortopulmonary septum that eventually fuses with the distal extent of
the truncal septum. Accordingly, the right and left pulmonary arteries originate from the

2. pulmonary trunk, and the aortic arch emanates from the ascending aorta. The spiral
course of the truncoaortic partition produces the normal intertwinement of the great
arteries.
When conotruncal or truncoaortic septation does not proceed normally, various
congenital ventriculoarterial anomalies may result. One of these anomalies is truncus
arteriosus, in which a single arterial trunk exits from the heart. Also, either deficiency or
absence of the conal (infundibular) septum produces a large ventricular septal defect.
Because the conal septum also contributes to the development of the anterior tricuspid
leaflet and the medial tricuspid papillary muscle, these structures may be malformed.
The single truncal valve may be deformed and functionally insufficient or, less
commonly, stenotic. If vestiges of distal truncoaortic septation develop, the pulmonary
arteries may arise together from a short pulmonary trunk; otherwise, they arise
separately from the truncal root.
Pathology
Truncus arteriosus is characterized by a single arterial vessel that arises from the
base of the heart and gives origin to the coronary, pulmonary, and systemic arteries
(Fig. 44.1). A single semilunar valve is found in truncus arteriosus, and this valve
differentiates truncus arteriosus from aortic and pulmonary valve atresia, conditions in
which a single arterial vessel also receives the entire output of both ventricles but in
which a second atretic semilunar valve is present. Collett and Edwards recognized four
types of truncus arteriosus on the basis of the anatomic origin of the pulmonary arteries.
In type I, a short pulmonary trunk originating from the truncus arteriosus gives rise to
both pulmonary arteries. When both pulmonary arteries separate from the truncus
arteriosus, with no vestige of a main pulmonary artery, they may arise close to one
another (type II) or at some distance from one another (type III). The type IV truncus
arteriosus is now considered to represent a form of pulmonary atresia with ventricular
septal defect and will not be discussed further in this chapter.
Van Praagh and van Praagh have proposed an expanded classification system
that also includes two commonly associated abnormalities of the great arteries. Their
type A1 corresponds to type I of Collett and Edwards, and type A2 encompasses types
II and III (Fig. 44.2). Type A3 includes cases with absence of truncal origin of one
pulmonary artery, with blood supply to that lung from the ductus arteriosus or from a
collateral artery. Last, type A4 is associated with underdevelopment of the aortic arch,
including tubular hypoplasia, discrete coarctation, or complete interruption.

3. The ventricular septal defect in truncus arteriosus is generally large and results
from either absence or pronounced deficiency of the infundibular septum. The defect is
cradled between the two limbs of the septal band and is roofed by the truncal valve
cusps (Fig, 44.1). In most instances, fusion of the inferior limb and the parietal band
causes muscular discontinuity between the tricuspid valve and the truncal valve.
Accordingly, the membranous septum is intact and the defect is of the infundibular type.
When such fusion fails to occur, tricuspid-truncal valvular continuity is present, and the
defect (which now involves the membranous septum) is of combined membranous and
infundibular types. Rarely, the ventricular septal defect in truncus arteriosus may be
small and restrictive or even absent.
Among 400 cases of truncus arteriosus from four publications reviewed by
Fuglestad et al., the truncal valve was tricuspid in 277 (69%), quadricuspid in 86 (22%),
bicuspid in 35 (9%), pentacuspid in 1 (0.3%), and unicommissural in 1 (0.3%). The
semilunar valve is in fibrous continuity with the mitral valve in all patients but is
continuous with the tricuspid valve in only a minority. By overriding the ventricular
septum, the truncus arteriosus has a biventricular origin in 68% to 83% of patients
(15,18). In 11% to 29% of patients, the truncal valve arises entirely from the right
ventricle, whereas in 4% to 6% of patients, it emanates entirely from the left ventricle.
The anatomic cause for truncal valve insufficiency is variable and includes
thickened and nodular dysplastic cusps, prolapse of unsupported cusps or of conjoined
cusps with only a shallow raphe, inequality of cusp size, minor commissural
abnormalities, and annular dilation. Truncal valve stenosis, when present, usually is
associated with nodular and dysplastic cusps. The truncal root frequently is dilated, and
the truncal sinuses often are poorly developed.
A right aortic arch with mirror-image brachiocephalic branching is associated
more commonly with truncus arteriosus, occurring in 21% to 36% of patients, than with
any other congenital cardiac malformation except pulmonary atresia with ventricular
septal defect. Rarely, a double aortic arch persists. Hypoplasia of the arch, either with or
without coarctation of the aorta, occurs in 3% of patients. Interrupted aortic arch occurs
relatively frequently (11% to 19% of patients) and is accompanied by ductal continuity
of the descending thoracic aorta. It is frequently associated with the DiGeorge
syndrome.
The ductus arteriosus is absent in approximately half of patients with truncus
arteriosus, but it remains patent postnatally in nearly two thirds of patients in whom it is
present. The relative sizes of the aorta and the ductus arteriosus tend to vary inversely,

4. such that the ductus arteriosus is particularly large in patients with underdevelopment of
the aortic arch (type A4 truncus).
The pulmonary arteries most commonly arise from the left posterolateral aspect
of the truncus arteriosus, a small distance above the truncal valve. Type I truncus
arteriosus is observed in 48% to 68% of patients, type II in 29% to 48%, and type III in
6% to 10%. In type II, the left pulmonary artery ostium is generally somewhat higher
than that of the right pulmonary artery. Rarely, in the setting of interrupted aortic arch,
this ostium may arise to the right of the right pulmonary artery ostium and cause
crossing of the pulmonary arteries posterior to the truncus arteriosus.
Stenosis of the pulmonary artery ostia or arteries is uncommon. In rare
instances, deformed truncal valvular tissue may obstruct the pulmonary ostia during
ventricular systole. In general, however, unless pulmonary arterial banding is
performed, the pulmonary vascular bed will be exposed to systemic arterial pressure. In
rare instances, deformed truncal valvular tissue may obstruct the pulmonary ostia during
ventricular systole.
In truncus arteriosus, one pulmonary artery may be absent. Of the Mayo Clinic's
previously published series of patients with truncus arteriosus, 16% (11 of 70) had only
a single pulmonary artery. In 9 of the 11 patients, the pulmonary artery was absent on
the side of the aortic arch. Thus, in truncus arteriosus, the pulmonary artery is most
frequently absent on the side of the aortic arch, in contrast to tetralogy of Fallot, in
which the pulmonary artery is more frequently absent on the side opposite the aortic
arch.
This chapter does not consider either so-called pseudotruncus arteriosus, which
is actually a form of pulmonary valve atresia with ventricular septal defect, or
hemitruncus, in which one pulmonary artery arises from the ascending aorta and the
other emanates from the right ventricle and clearly has a well-developed pulmonary
valve at its origin. The embryologic basis for these deformities appears to be different
from that for true persistent truncus arteriosus.
Knowledge of variations in coronary arterial origin and distribution, which are
common in truncus arteriosus, is important to the surgeon. Because the left anterior
descending coronary artery frequently is relatively small and displaced leftward, the
conus branch of the right coronary artery, in a compensatory manner, is usually
prominent and supplies several large branches to the right ventricular outflow tract. The
posterior descending coronary artery arises from the left circumflex artery (left coronary
dominance) in 27% of truncus arteriosus patients, which is about three times the
frequency of this variation in the normal population. Anomalies of coronary ostial

5. origin, involving 37% to 49% of patients with truncus arteriosus, are common,
regardless of the number of truncal valve cusps. In general, however, the left coronary
artery tends to arise from the left posterolateral truncal surface and the right coronary
artery from the right anterolateral surface.
In the setting of a single coronary ostium, frequently associated with left
coronary dominance, all three major epicardial branches originate from this common
site, or the right coronary artery may be absent. When two ostia exist, both may arise
from the same truncal sinus; one may take origin from the expected site of the
noncoronary sinus, or both may arise normally. High ostial origin, above the truncal
sinotubular junction, occurs often; but when the origin is at or slightly above a truncal
valve commissure, the involved ostium (most commonly the left) may be slitlike and
functionally stenotic. Conceivably, dysplastic valvular tissue also could obstruct an
otherwise normal coronary ostium. Rarely, the left coronary artery originates from the
pulmonary trunk. Combinations of the aforementioned coronary anomalies frequently
are observed.
The location of the conduction tissue in truncus arteriosus is also of surgical
importance. The sinus node and the atrio-ventricular node are normal in location and
structure. The atrioventricular bundle courses to the left of the central fibrous body, and
the left bundle branch emanates along the left ventricular septal subendocardium, just
beneath the membranous septum. The right bundle branch travels within the
myocardium of the ventricular septal summit, attaining a subendocardial course at the
level of the moderator band. In most instances in which the ventricular septal defect is
truly infundibular and the membranous septum is intact, the atrio-ventricular conduction
tissue is somewhat distant from the rim of the defect. In patients with combined
membranous-infundibular ventricular septal defect, however, the conduction tissue
passes along the left aspect of the posterior–inferior rim of the defect.
The anomalies most commonly associated with truncus arteriosus (discussed
above) are right aortic arch, interrupted aortic arch, absent ductus arteriosus, patent
ductus arteriosus, unilateral absence of a pulmonary artery, coronary ostial anomalies,
and an incompetent truncal valve. A secundum atrial septal defect has been noted in 9%
to 20% of patients, an aberrant subclavian artery in 4% to 10%, a persistent left superior
vena cava draining into the coronary sinus in 4% to 9%, and mild tricuspid stenosis in
6%. Total or partial anomalous pulmonary venous connection in association with
truncus arteriosus also has been described. Rare associated anomalies that have been
reported include tricuspid atresia, mitral atresia, ventricular inversion, and association
with the asplenia complex. We have encountered one patient with both truncus

6. arteriosus and complete atrioventricular septal defect. Extracardiac anomalies, present
in 21% to 30% of autopsy cases of truncus arteriosus, include skeletal deformities,
hydroureter, bowel malrotation, and multiple complex anomalies.
Among the secondary complications of truncus arteriosus, biventricular
hypertrophy is frequent, and dilation of ventricular chambers is prominent when truncal
valve insufficiency exists. If there is massive cardiac hypertrophy, chronic
subendocardial myocardial ischemia may develop (even with normal epicardial
coronary arteries). As a result of chronic exposure of the pulmonary vasculature to
systemic arterial pressure, hypertensive pulmonary vascular disease (plexogenic
pulmonary arteriopathy) may develop. The arteriolar lesions often develop more rapidly
and to a more severe extent in truncus arteriosus than in isolated ventricular septal
defect. With chronic truncal valve insufficiency, pulmonary venous hypertension also
may develop.
As patients with surgical repair survive into adulthood, progressive dilation of
their aorta (original truncal artery) often occurs and may be associated with the
development of ascending “aortic” aneurysms and an increased risk for “aortic”
dissection or rupture, as well as “aortic” valve regurgitation.
Manifestations
Clinical Features
In most patients with truncus arteriosus, congenital heart disease is recognized
during early infancy, often during the neonatal period. During the 1990s, intrauterine
diagnosis became possible with fetal echocardiography. The clinical features depend
largely on the volume of pulmonary blood flow and whether associated significant
truncal valve insufficiency is present.
During the first weeks of life, persistence of increased pulmonary arteriolar
resistance present during fetal life may cause mild cyanosis with little evidence of
cardiac decompensation, unless severe truncal valve insufficiency is also present. As
pulmonary resistance gradually decreases and flow through the lungs increases, the
cyanosis may disappear. However, tachy-pnea, tachycardia, excessive sweating, poor
feeding, and other signs of pulmonary overcirculation may appear. If truncal valve
insufficiency is severe, the signs and symptoms of heart failure may appear shortly after
birth. The additional volume load produced by this associated problem always adds to
the increasing demands placed on the heart as pulmonary flow increases.

7. In the uncommon situation in which the infant has naturally occurring stenosis
of the pulmonary arteries, obvious cyanosis may be present at birth and may intensify
with increasing age. However, such stenosis protects the child from pulmonary
overcirculation that would otherwise occur with falling pulmonary resistance. Severe
cyanosis, in addition to the signs of heart failure, may be present early if the child has
both naturally occurring stenosis of the pulmonary artery and severe insufficiency of the
truncal valve.
Physical Examination
Physical findings are related primarily to the volume of pulmonary blood flow
and the presence or absence of truncal valve insufficiency. Patients with increased
pulmonary blood flow have little or no cyanosis. The peripheral pulses are accentuated
and may be bounding. The pulse pressure usually is increased owing to runoff into the
pulmonary vascular bed during diastole. A left precordial bulge may be noted, and a
systolic thrill often is palpable along the left sternal border. The heart usually is
overactive. The first heart sound is normal and frequently followed by an ejection click,
which echocardiographic studies have shown to coincide with maximal opening of the
truncal valve. The second heart sound usually is loud and single. The occasional
auscultatory or phonocardiographic observation of a split second sound in these patients
with a single semilunar valve may be caused by delayed closure of some of the cusps of
the abnormal truncal valve. An apical third heart sound often is present. A loud
pansystolic murmur maximal at the lower left sternal border and radiating to the entire
precordium most often is heard. An apical diastolic low-pitched murmur caused by
increased flow across the normal mitral valve frequently is audible.
The patient with truncal valve insufficiency usually has a diastolic high-pitched
murmur that is heard best along the left sternal border. A truly continuous murmur is
uncommon in truncus arteriosus and, when present, is usually suggestive of pulmonary
artery ostial stenosis. Continuous murmurs are common in patients with pulmonary
valve atresia/ventricular septal defect, however, where either a patent ductus arteriosus
or systemic collateral arteries provide pulmonary blood flow. Because the differential
diagnosis of truncus arteriosus includes this lesion, a continuous murmur is strongly
suggestive of pulmonary atresia rather than of truncus arteriosus. Patients in heart
failure may exhibit the additional signs of tachypnea, crepitant rales, hepatomegaly, and
neck-vein distension.
Cyanosis is present, and clubbing of the fingers and toes may be seen in patients
with decreased pulmonary blood flow caused by naturally occurring pulmonary artery

8. stenosis, pulmonary artery banding, or pulmonary vascular disease. If there is no
associated truncal valve insufficiency, the peripheral pulses and pulse pressure are
nearly normal. The apical diastolic murmur often is not present. These patients are less
likely to have signs and symptoms of cardiac decompensation.
Electrocardiographic Features
The electrocardiogram normally shows a normal frontal plane QRS axis or
minimal right-axis deviation. Generally, normal sinus rhythm is present, and the
conduction times are not prolonged. Combined ventricular hypertrophy occurs
frequently. Left ventricular forces are particularly prominent in patients with increased
pulmonary blood flow. Left atrial enlargement also is common in this group. Patients
with normal or decreased pulmonary flow may exhibit right ventricular hypertrophy
only.
Radiologic Features
Typically, radiography of the chest shows moderate cardiomegaly and increased
pulmonary vascular markings. The aortic arch is right-sided in approximately one third
of patients, and the combination of a right aortic arch and increased pulmonary
vascularity is strongly suggestive of truncus arteriosus. Type I truncus arteriosus
frequently is associated with a relatively superiorly located proximal left pulmonary
artery, which usually can be distinguished on a frontal chest radiograph (Fig, 44.3). A
dilated truncal root is common.
Although the pulmonary vascular markings typically are increased, variation in
the pulmonary vascular pattern can be seen. In truncus arteriosus with absent pulmonary
artery, the pulmonary vascular markings are markedly diminished on the side without
the pulmonary artery (usually the left side). In addition, pulmonary vascular obstructive
disease is common in patients with truncus arteriosus and is reflected in the chest
radiograph by disproportionate enlargement of the central pulmonary arteries associated
with accentuated tapering of the distal pulmonary arterial tree.
Echocardiographic Features
The use of two-dimensional, Doppler, and color Doppler echocardiography, has
greatly increased the ability to determine accurately the cardiac anatomy and, in most
cases, the hemodynamics in truncus arteriosus. Subcostal windows are used to
document abdominal visceral situs and atrial situs, in addition to the position of the
cardiac apex. A single great vessel arising from the heart is typically seen subcostally

9. (Fig. 44.4A), and assessment of the atrial septum is best performed from this location.
Subcostal windows provide additional views for evaluation of the truncal valve
function, truncal root and pulmonary artery branch anatomy. The parasternal long-axis
view demonstrates the deficiency in the ventricular septum and the overriding great
artery, with continuity between the truncal valve and the mitral valve. Slightly higher
position in the parasternal long-axis view can be used to visualize the origin of the
pulmonary trunk or branches (Fig. 44.4B). Further imaging is required to document the
presence of a single arterial trunk and lack of a pulmonary outflow tract from the
ventricle. High parasternal short-axis views will provide visualization of the pulmonary
arteries arising directly from the posterolateral aspect of the truncal root, typically
bifurcating into the right and left pulmonary arteries. Persistence of a short main
pulmonary artery segment is seen in truncus arteriosus type I (Van Praagh type A1, Fig.
44.5), with separate origins of the pulmonary branches seen in type II (type A2). When
only one pulmonary artery is present, as in type III truncus (type A3), the remaining
pulmonary artery origin must be documented, typically originating from the aortic arch
or ductus arteriosus. The short-axis view is also useful in evaluating the anatomy of the
truncal valve leaflets (number and morphology), as well as visualization of the coronary
arteries and their origins, and the location and extension of the ventricular septal defect.
Suprasternal notch imaging is critical for evaluation of the aortic arch anatomy, as
interruption of the aortic arch may be associated with truncus arteriosus (type A4).
Right-sided aortic arch also is common in truncus arteriosus and can be determined
from short axis imaging of the arch branching pattern. In addition, the pulmonary artery
branches can also be visualized from the suprasternal notch, excluding any important
branch stenoses.
Aortopulmonary window is in the differential diagnosis of truncus arteriosus and
angiocardiographically may be confused with truncus arteriosus. Echocardiographically,
however, these two entities can be differentiated easily. Aortopulmonary window
usually is not associated with a ventricular septal defect, and the right ventricular
outflow tract and pulmonary valve are in the expected positions. These features usually
are recognized easily by two-dimensional echocardiography. Moreover, in
aortopulmonary window, use of a high parasternal short-axis view usually allows its
direct visualization. In patients with truncal valve stenosis, Doppler echocardiography
usually enables an estimation of this gradient. In patients with significant truncal valve
insufficiency, the systolic Doppler gradient may overestimate the degree of valve
stenosis owing to the volume of flow across the valve (two-dimensional morphology
must be correlated with the Doppler findings). Truncal valve incompetence also can be

10. delineated and quantitated by Doppler technique; the color flow Doppler examination
has been particularly helpful in this assessment.
Doppler flow reversal in the abdominal descending aorta may be due to either
pulmonary artery runoff, truncal valve insufficiency, or both. In the rare patient with a
pulmonary artery band(s) in place, Doppler evaluation also permits assessment of the
pressure gradient between the truncal root and the pulmonary arteries beyond the band.
Truncus arteriosus also may be diagnosed in utero with fetal echocardiography.
The echocardiographer must be certain to identify the central main pulmonary artery
(MPA) origin or proximal branch origin from the ascending truncal root to differentiate
this condition from pulmonary atresia/ ventricular septal defect. Severe truncal valve
dysfunction (stenosis typically in combination with regurgitation) in utero may lead to
fetal hydrops.
Cardiac Catheterization and Angiocardiography
With the introduction and advancement of accurate echo-Doppler techniques
and the advent of surgical correction during early infancy before irreversible pulmonary
vascular disease is a concern, diagnostic cardiac catheterization and angiography are
now infrequently necessary in the patient with truncus arteriosus. Occasionally, the
patient with truncus arteriosus with associated interruption at the aortic arch or single
pulmonary artery will still need angiography to delineate aortic arch anatomy or the
anatomy of the pulmonary arterial tree precisely. Even more uncommonly in this era, a
patient with truncus arteriosus will still present initially beyond early infancy for
consideration of surgical correction, and cardiac catheterization may be necessary to
assess the status of the pulmonary vascular bed. An example of a truncal root angiogram
is seen in Fig. 44.6.
Patients with truncus arteriosus are at risk of having pulmonary vascular
obstructive disease develop at an early age, and this has provided the major impetus for
early surgical correction. For the occasional patient presenting beyond infancy,
pulmonary vascular resistance must be assessed accurately to select the best treatment.
Although direct measurement of pulmonary resistance is not possible, the calculated
indirect value, obtained by dividing the mean driving pressure across the pulmonary bed
(in mm Hg) by the total pulmonary flow index (in liters per minute per square meter),
provides a reliable estimation of the status of the pulmonary arterioles.
Patients with truncus arteriosus who have two pulmonary arteries and a
pulmonary arteriolar resistance >8 units m2 are at higher operative risk than patients
with resistances below that level. Among the group with resistances >8 units m2, late

11. deaths were due to progression of pulmonary vascular obstructive disease with
secondary severe pulmonary hypertension and right ventricular failure. Among the
survivors of operation in the group with preoperative resistance <8 units per m2, no late
deaths occurred secondary to progressive pulmonary hypertension.
Fortunately, the trend toward early corrective surgery has reduced the number of
patients who are inoperable because of pulmonary vascular obstructive disease. Patients
with truncus arteriosus who have significant elevation of pulmonary vascular resistance
still occasionally are seen, however, and our current policy is not to offer corrective
surgery to patients with truncus arteriosus who have two pulmonary arteries and whose
pulmonary arteriolar resistance is >8 units m2. The exceptions are children younger
than 2 years of age whose resistance decreases <8 units m2, when 100% oxygen is
breathed or after administration of a pharmacologic vasodilator such as inhaled nitric
oxide. In such young patients, surgery still may be offered if the parents are willing to
accept a higher surgical risk because it is possible that the increased resistances may
result from arteriolar or medial smooth muscle hypertrophy and vasoconstriction rather
than advanced intimal occlusive disease. These changes, potentially, may be reversible.
Different criteria must be used to assess the feasibility of operation in patients
with unilateral absence of a pulmonary artery. Severe pulmonary vascular disease is
particularly likely to develop at an early age in patients with a single pulmonary artery.
To achieve good surgical results in this subgroup, corrective surgery should be
performed in the neonatal period. Even in such patients who survive corrective
operation, however, pulmonary vascular disease tends to progress postoperatively more
often than it does in patients with corrected truncus arteriosus who have two pulmonary
arteries. This difference may be related to the fact that the entire cardiac output still
must pass through one lung so that the rate of flow through each arteriole remains
approximately double. This may be a potential stimulus for the progression of
pulmonary vascular changes.
An accurate preoperative catheterization laboratory assessment of truncal valve
insufficiency may be difficult because of contrast runoff into the pulmonary artery bed.
Magnetic Resonance Imaging
Cardiac magnetic resonance imaging (MRI) and angiography (MRA) can
provide additional noninvasive anatomic and hemodynamic information in the patient
with truncus arteriosus. Visualization of the conotruncus and pulmonary artery anatomy
is accomplished by multiple techniques, including black blood and white blood imaging
techniques with gating, and with the use of gadolinium contrast-enhanced MRA.

12. Differential Diagnosis
In infants with truncus arteriosus and increased pulmonary blood flow, the
differential diagnosis includes the other congenital cardiac conditions that cause early
heart failure and are associated with either mild or no cyanosis. Such malformations
include ventricular septal defect, patent ductus arteriosus, aorticopulmonary window,
pulmonary atresia with ventricular septal defect, and patent ductus arteriosus, or large
collateral arteries, double-outlet right ventricle, univentricular heart, and total
anomalous pulmonary venous connection. In truncus arteriosus with decreased
pulmonary flow, other conditions to be considered include pulmonary atresia, tricuspid
atresia, tetralogy of Fallot, univentricular heart with pulmonary stenosis, and double-
outlet right ventricle with pulmonary stenosis. Although certain physical findings, chest
radiographic evidence, and electrocardiographic features may suggest the increased
likelihood of a particular lesion, echocardiography is necessary to establish the
diagnosis definitively.
Natural History
Although patients with truncus arteriosus occasionally survive to adulthood
without surgery, the natural history of this condition is generally dismal. In one autopsy
series, the mean age of death was 5 weeks. Another series reported a survival of only
15% beyond the age of 1 year. Death in infancy most commonly is caused by heart
failure. In patients who survived the first 4 years, death may occur from heart failure,
but more frequently it results from the complications of hypertensive pulmonary
vascular disease and infective endocarditis.
Once severe pulmonary vascular disease is present, deterioration often is rapid,
with severe morbidity and death frequently occurring in late childhood or early
adolescence. This dismal natural history was the main factor that gave rise to the
approach of early surgical intervention that is now advocated for these patients.
Treatment
The diagnosis of truncus arteriosus in itself is an
indication for operation. Diagnosis ideally is made prenatally or soon after
birth. Medical stabilization is performed in the intensive care unit, and operation with
complete repair is preferred in the first weeks of life. Delay of operation results in
chronic ischemia of the hypertrophied ventricle, which is perfused by desaturated blood
at a low diastolic perfusion pressure caused by runoff through the pulmonary arteries,

13. and, when present, “aortic” insufficiency. This hazard of ventricular dysfunction may
explain in part the observation that repair of truncus at 6 to 12 months of age is
associated with a mortality twice that for repair between 6 weeks and 6 months of age.
Pulmonary vascular obstructive disease also can develop early, which provides
additional impetus for correction in the first few months of life. Pulmonary vascular
obstructive disease, no doubt, also is partly responsible for the increased surgical
mortality in infants who undergo repair after 6 months of age.
The preferred operation is complete repair during the
neonatal period. Although pulmonary artery banding may provide palliation for
young patients with truncus arteriosus, there are well-documented risks and potential
complications of banding for this condition. In addition, successful banding has not
guaranteed that these patients will be good candidates for later correction. During the
past 15 years, improved surgical techniques and postoperative care have made
correction of truncus arteriosus during infancy possible at an operative risk less than
that previously reported for banding.
Surgical Correction
Successful definitive surgical correction in a patient with truncus arteriosus was
first accomplished by McGoon et al. in 1967. In the original operation, based on the
experimental work of Rastelli et al., continuity between the right ventricle and the
pulmonary arteries was established with an aortic homograft. Cryopreserved homograft
tissue continues to be the conduit of choice for repair of this defect in early infancy.
The early and late results experienced by the initial 92 patients who had
correction at the Mayo Clinic were reported in 1977. Although overall hospital
mortality was 25%, the operative mortality decreased to 9% in the 33 patients operated
on during the last 2 1/2 years of this early series. Since that time, an operative mortality
of 5% was achieved in patients without severe associated abnormalities who
subsequently have undergone correction of truncus arteriosus. In 1984, Ebert et al. (10)
reported results of 100 infants repaired prior to 6 months of age, emphasizing the
importance of early repair to prevent the development of pulmonary vascular
obstructive disease. Early mortality was 11%. It also was emphasized at this time the
importance of complete repair in early infancy to prevent the development of pulmonary
vascular obstructive disease.
During the last three decades, there as been great progress in the surgical
management of infants. In the current era, excellent results have been obtained with
corrective operation during infancy. In patients who undergo successful correction

14. during early infancy, the small conduit eventually must be replaced with a larger one,
but reoperation for conduit replacement alone carries a low risk. A 1993 late follow-up
of 137 patients with truncus arteriosus corrected at the Mayo Clinic between 1967 and
May 1992 revealed no perioperative deaths in 39 patients who underwent subsequent
reoperation for isolated conduit replacement. One death occurred in 15 patients who had
isolated conduit replacement performed elsewhere.
Although techniques of repair that do not include an extracardiac conduit have
also been described, most prefer a valved conduit when complete repair is performed
because of the presence of pulmonary hypertension. Techniques for conduit
replacement have evolved over the last two decades. It is our current preference to use
the autologous tissue reconstruction (“peel operation”) to reconstruct the right
ventricular outflow tract when conduit replacement is required (Fig. 44.9). The
technique includes placement of a prosthetic roof (usually bovine pericardium) over the
fibrous bed of the explanted conduit with insertion of a prosthetic valve (usually
bioprosthesis). Early mortality has been low for conduit replacement, in our experience,
even after multiple conduit revisions. Early mortality was 2% but was 0% for isolated
conduit replacement. Overall survivorship free of reoperation for the peel reconstruction
at 10 and 15 years was 90.7% and 82%, respectively.
The presence of a regurgitant truncal valve is almost always amenable to various
repair techniques, and replacement is rarely if ever required in the neonatal period.
Numerous authors have describe various truncal valvuloplasty techniques. Frequently
used techniques include suturing of the prolapsing leaflet to adjacent leaflets; the
prolapsing leaflet is usually thickened and adjacent leaflet edges are also thickened,
which facilitates suture placement. The tops of the commissures often are splayed from
dilation of the sinotubular junction. This can be corrected by wedge excisions of the
aorta. If recurrent truncal valve incompetence occurs, our policy is to repair or replace
the truncal valve at the time of reoperation for conduit replacement.
Late results following complete repair are determined by the degree of truncal
valve regurgitation and the need for conduit replacement. The need for truncal valve
repair at the time of complete repair is low. If reoperation is required for truncal valve
regurgitation, intermediate-term results favor repair of the truncal valve. Serial
echocardiographic examinations are essential during lifelong follow-up. Recurrent
truncal valve regurgitation may require repair or replacement at a subsequent operation
(Fig. 44.10). In our follow-up of 137 patients with truncus arteriosus who were
operative survivors in our initial 25-year experience, no one required truncal valve
replacement when trivial or no truncal valve incompetence was present at the time of

15. correction. In patients who had mild, moderate, or severe truncal incompetence, the
eventual need for truncal valve replacement was high. The difference between the two
groups was highly significant (p <0.001, Fig. 44.11).
The primary late problem related to extracardiac conduit operations is the need
for conduit replacement because of patient somatic growth or progressive deterioration
and calcification of the conduit (Fig. 44.12). Numerous reports have focused on issues
of conduit size, valve degeneration, and conduit degeneration. Late outcome of
homograft and prosthetic conduits has been reported with variable results. Our attempt
to reduce the incidence of late conduit failure was the construction of an autologous
tissue conduit, with or without a valve. Advantages of this technique include an
autogenous floor with a pericardial roof that does not form obstructive peels, and the
diameter of the pathway can be as large as desired, allowing a bioprosthesis to be
inserted. We have examined the freedom from reoperation for conduit failure in an age-
matched group of patients who have received a Hancock conduit, a homograft conduit,
and a valved peel reconstruction (Fig. 44.13). The peel operation had statistically
significant freedom from reoperation compared with the homograft (p = 0.001).
Although the peel operation had more favorable durability than the Hancock conduit,
this did not reach statistical significance (p = 0.19) owing to the small numbers in the
peel operation group at late follow-up.
The search continues for the ideal extracardiac conduit. Although the need for
reoperation is inevitable for most patients, the risk of reoperation is low and most
patients enjoy a good quality of life. At present, the peel operation provides the most
favorable freedom from reoperation and is our procedure of choice when conduit
replacement is required.
Long-Term Issues
In summary, the patient with repaired truncus arteriosus will need lifelong
cardiovascular follow-up. Infective endocarditis precautions are warranted. Primary
issues that will require attention, ongoing evaluation, and potentially further treatment
after neonatal repair include truncal valve dysfunction (stenosis and/or insufficiency),
function of the pulmonary homograft/conduit in the right ventricular outflow tract, and
the development of branch pulmonary artery stenosis. Left and right ventricular
function, both systolic and diastolic, must be evaluated in an ongoing fashion.
Echocardiography and cardiac MRI/MRA are useful tools for ongoing noninvasive
evaluation of the patient with repaired truncus arteriosus. Seamless transition from the

16. pediatric cardiologist to the adult congenital heart disease specialist is clearly warranted
as this patient group ages.