TRUNCUS ARTERIOSUS

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 addition, 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 termtruncus 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 IIV, 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), 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 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 cyanosis 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 is common. 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.

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

Mortality/Morbidity
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.

Race
Based on limited data, no racial predilection is apparent.

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

Age
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.

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
Diaphoresis
Tachypnea
Cyanosis
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

Patients with truncus arteriosus often present with cyanosis and are typically found to have
decreased systemic arterial oxygen saturation.
Cyanosis may not be evident, especially 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 probably 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.

Causes

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.
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 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.
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 gene.
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.
One report found that children of mothers with significant diabetes mellitus during
pregnancy had an increased incidence of truncus arteriosus; however, this is not widely recognized as a
significant risk factor.[3]
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.

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.

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.
Echocardiography
Echocardiography with cross-sectional and Doppler flow analysis is sufficient to confirm
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.
An echocardiographic image of truncus arteriosus is shown in the image below.

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.

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.

Other Tests

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 rightaxis 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.

Procedures

Cardiac catheterization
Standard angiographic images from the truncal root can aid in the assessment of
coronary arterial anatomy, 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.[4]
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.

Histologic Findings
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.

Medical Care

Medical care before surgical repair depends on clinical presentation.

Most neonates with truncus arteriosus display some evidence of congestive heart failure; they 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.[5]
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.

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.

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.

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.