shunt and chronic cyanosis.

Current hospital survival for the arterial switch operation ranges from approximately 90% to

98%.51,59–62 In earlier eras, d-TGA/IVS had a lower operative mortality than d-TGA/VSD; however,

recent studies have neutralized this difference.59,60 Complex d-TGA including d-TGA/VSD/PS and dTGA/VSD with aortic arch hypoplasia are independent predictors of increased operative mortality.63,64

Coronary artery anatomy does not affect mortality.59 Long-term survival at 5 to 10 years and 15 years

ranges from 87% to 93% and 86% to 88%, respectively.60–62 The most common cause for reintervention

is supravalvar PS, occurring in 3.9% to 16%.61,62 Late follow-up of arterial switch operation patients has

led to increased concern regarding coronary artery patency and neoaortic root dilation.65

Figure 81-6. Arterial switch procedure for transposition of the great arteries. A: Division of aorta and pulmonary artery. B:

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LeCompte maneuver; posterior translocation of the aorta. C: Mobilization of the coronary arteries. D: Placement of pantaloonshaped pericardial patch. E: Proper alignment of the coronary arteries on the neoaorta. F: Completed repair.

Figure 81-7. The Rastelli procedure for transposition of the great arteries with ventricular septal defect and pulmonary stenosis. A

prosthetic patch placed within the right ventricle directs left ventricular blood through the defect to the aorta. The main pulmonary

artery is ligated, and right ventricular blood then passes through a conduit to the distal pulmonary arteries.

TRUNCUS ARTERIOSUS

Truncus arteriosus is a rare anomaly that accounts for 0.4% to 4% of all cases of congenital heart

disease.66–68 A single arterial vessel arises from the heart, overriding the ventricular septum and giving

rise to the systemic, coronary, and pulmonary circulations. Two classification schemes have been

proposed: one by Collett and Edwards

69 in 1949 and the other by Van Praagh and Van Praagh70 in 1965

(Fig. 81-8). The Collett and Edwards classification focused on the origin of the pulmonary arteries from

the common arterial trunk (Table 81-2). The system offered by Van Praagh and Van Praagh, a

somewhat more surgically oriented scheme, is based on the presence or absence of a VSD, the degree of

formation of the aorticopulmonary septum, and the status of the aortic arch (Table 81-3).

Persistent truncus arteriosus is the result of failed development of the aorticopulmonary septum and

subpulmonary infundibulum (conal septum). Normal septation leads to the development of both

pulmonary and systemic outflow tracts, division of the semilunar valves, and formation of the aorta and

pulmonary arteries. Failure of septation results in a VSD (absence of the infundibular septum), a single

semilunar valve, and a single arterial trunk. Most cases are associated with a VSD reminiscent of the

VSD associated with TOF. However, in this anomaly, the superior margin of the defect is formed by the

truncal valve. The truncal valve leaflets are generally dysmorphic, and their motion may be restricted.

Leaflet number is highly variable, with about 65% tricuspid, 22% quadricuspid, 9% bicuspid, and rarely

unicuspid or pentacuspid.71 As a result of these abnormally developed valve leaflets, a moderate or

greater degree of truncal insufficiency is present in 20% to 26% of patients.72,73 Mild stenosis is

common; however, significant stenosis is present in only 4% to 7%.72,73 Significant obstruction is

predicted by gradients of more than 30 mm Hg in the presence of a normal cardiac output.74 The PAs

are usually of normal size and most often arise from the left posterolateral aspect of the truncal artery,

often in close proximity to the truncal valve and ostium of the left coronary artery.

Other cardiac anomalies are common, with a PFO usually present. A true ASD is found in 9% to 20%,

a persistent left superior vena cava in 4% to 9%, and mild tricuspid valve stenosis in 6%.28,75 An

interrupted aortic arch, most commonly type B, is present in association with truncus arteriosus (Van

Praagh type A4/B4) in approximately 10% to 20%.76,77 The arch is rightward, generally with mirrorimage branching, in 21% to 36%.75,77 Aberrant origins of the brachiocephalic vessels are reported, most

commonly an aberrant right subclavian artery in 4% to 10%.75,78 Coronary ostial abnormalities are of

particular surgical significance and occur in 37% to 49% of cases.79 The left coronary artery is

frequently noted to have a high origin, not uncommonly near the takeoff of the pulmonary arteries.

Rarely, the left coronary can originate from the main pulmonary trunk or a branch PA.78 Extracardiac

anomalies are reported in approximately 28% of patients with truncus arteriosus.72 Described

abnormalities include skeletal, genitourinary, and gastrointestinal deformities. As mentioned earlier,

monoallelic microdeletion of chromosome 22q11 is common, with DiGeorge syndrome diagnosed in at

least 11%.72

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Figure 81-8. Truncus arteriosus: classification schemes as described by Collett and Edwards

69 and by Van Praagh and Van Praagh.70

(Adapted from Hernanz-Schulman M, Fellows KE. Persistent truncus arteriosus: pathologic, diagnostic, and therapeutic

considerations. Semin Roentgenol 1985;20:121.)

Table 81-2 Collett and Edwards Classification of Truncus Arteriosus

The anatomy of truncus arteriosus results in the obligatory mixing of systemic and pulmonary venous

blood at the level of the VSD and truncal valve, which produces arterial saturations of 85% to 90%. The

systemic arterial saturation depends on the volume of PBF, which in turn is determined by the PVR. As

the PVR begins to fall, excessive pulmonary circulation ensues and leads to pulmonary congestion and

signs and symptoms of CHF. This nonrestrictive left-to-right shunt may cause early development of

irreversible pulmonary vascular obstructive disease.

The presence of truncal valve abnormalities poses further hemodynamic burdens. Truncal valve

regurgitation leads to ventricular dilatation and low diastolic coronary perfusion pressures that can

result in myocardial ischemia. Truncal valve stenosis promotes ventricular hypertrophy, increases the

myocardial oxygen demand, and limits coronary and systemic perfusion, especially with the large

volume of runoff into the pulmonary vascular bed.

Table 81-3 Van Praagh and Van Praagh Classification of Truncus Arteriosus

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Neonates with truncus arteriosus present with signs of CHF and collapsing peripheral pulses. Chest

radiography shows marked cardiomegaly; pulmonary plethora, often with minimal thymus shadow; and

a right aortic arch. The ECG most often depicts biventricular hypertrophy. Echocardiography is the

diagnostic procedure of choice and can demonstrate the truncal vessel, the structure and function of the

truncal valve, associated lesions such as interrupted aortic arch, and often the pulmonary arterial

anatomy. Cardiac catheterization is not performed unless the anatomy is unclear, further information is

needed about the status of the truncal valve, or the status of the pulmonary vasculature is unclear (i.e.,

infants older than 3 months at diagnosis).

The natural history of patients born with truncus arteriosus is early demise. Approximately 40% of

infants are dead within 1 month, 70% by 3 months, and 90% by 1 year.80 Early death is caused by CHF.

Survivors may do well for a period of time until the development of pulmonary vascular obstructive

disease and Eisenmenger syndrome. The ultimate treatment of truncus arteriosus is surgical correction

in the neonatal period. Medical treatment is palliative and directed toward controlling CHF with fluid

restriction, diuretics, digitalis, and afterload reduction. Complete repair entails separating the

pulmonary arteries from the truncus, repairing the resulting defect in the aorta, closing the VSD, and

restoring the continuity of the right ventricular outflow tract with an extracardiac conduit. Severe

truncal valve regurgitation requires truncal valve repair81 or replacement, which is best done with a

cryopreserved allograft. An associated interrupted aortic arch is repaired by constructing a primary endto-end anastomosis of the distal ascending aorta with proximal augmentation if necessary.

The results of truncus arteriosus repair have improved greatly during the last two decades. Before the

importance of early operation to avoid irreversible PVR was appreciated, patients underwent repair at

most institutions at an average age of 2 to 5 years with high mortality rates. Ebert et al. showed that

repair in the first 6 months of life is not only possible, but also preferable, reporting a mortality rate of

9%.82 Current hospital mortality for the neonatal repair of truncus arteriosus ranges between 4.3% and

17%, with the majority of deaths occurring in complex truncus arteriosus or in truncus arteriosus with

associated severe truncal valve regurgitation.72–74,83–85 Risk factors for poor outcome identified in

various studies include significant truncal regurgitation, need for truncal valve replacement, birth

weight less than 2.5 kg, presence of interrupted aortic arch or coronary artery anomalies, pulmonary

reconstruction with a technique other than valved heterograft or allograft, and age older than 100

days.72–74,83–87 Other recent studies have demonstrated that interrupted aortic arch has been neutralized

as a risk factor.74,84

AORTIC STENOSIS

AS refers to a form of left ventricular outflow tract obstruction that may occur at the valvar (70%),

subvalvar (25%), or supravalvar (5%) level (Fig. 81-9). AS occurs in about 4% of patients with

congenital heart disease.7 The severity of AS may be graded by echocardiography or catheterization.

Classification by echocardiography peak instantaneous pressure gradient is mild (<40 mm Hg),

moderate (40 to 70 mm Hg), and severe (>70 mm Hg). Classification by catheterization peak-to-peak

pressure gradient is mild (<30 mm Hg), moderate (30 to 50 mm Hg), and severe (>50 mm Hg).

Valvar AS occurs secondary to maldevelopment of the aortic valve. Most commonly, a bicuspid valve

is present, although tricuspid and unicuspid valves are also represented. In valvar AS, the leaflets are

thickened and frequently dysmorphic, and there is a variable degree of leaflet fusion along the

commissures. The aortic annulus may be hypoplastic. In 20% of cases, valvar AS is associated with other

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cardiac defects, most commonly coarctation of the aorta, PDA, VSD, or mitral stenosis. Males with

valvar AS outnumber females by a ratio of 4:1. There is a wide spectrum of clinical presentation of

valvar AS, but patients tend to present in one of two groups: younger patients (neonates and infants)

with severe AS develop symptoms of rapidly progressive CHF, whereas older patients, with less severe

obstruction at birth, have a more indolent course.

Figure 81-9. Anatomy of the types of congenital aortic stenosis. A: Valvar aortic stenosis. B: Supravalvar aortic stenosis and its

repair (inset). C: Diffuse (tunnel) subvalvar aortic stenosis. D: Discrete subvalvar aortic stenosis.

Severe AS is usually well tolerated during fetal development. Although left ventricular output and

antegrade flow across the aortic valve are decreased, the right ventricle compensates with increased

output, and systemic perfusion is maintained by flow across the ductus. After birth, there is increased

venous return to the left heart, and this exacerbates the pressure load created by the stenotic aortic

valve, leading to left ventricular dysfunction. As the ductus closes during postnatal life, systemic

malperfusion may develop with resulting hypotension, acidosis, and oliguria. Coronary perfusion is also

impaired due to the combination of systemic hypotension and elevated left ventricular end-diastolic

pressure. Patients with critical AS typically exhibit severe left ventricular dysfunction. These patients

show signs of distress soon after birth. On examination, there is impaired distal perfusion with poor

capillary refill and diminished, thready pulses. A systolic ejection murmur may be absent if the cardiac

output is severely diminished. Differential cyanosis may be observed due to perfusion of the lower body

with desaturated blood shunting through the ductus. The ECG shows left ventricular hypertrophy, and

the chest radiograph displays cardiomegaly and pulmonary congestion. Echocardiography establishes

the diagnosis.

Fetal echocardiography has allowed for early diagnosis of critical AS. For some, this may predict the

progression to hypoplastic left heart syndrome or may result in irreversible left ventricular dysfunction.

A few centers in the United States have been able to successfully balloon dilate the aortic valve in utero

to promote left ventricular growth and preserve function in select cases.88–90

The neonate or infant with critical AS represents a true emergency. Endotracheal intubation and

inotropic support are routine. Ductal patency is maintained with prostaglandins, and acidosis is

corrected. All patients with critical AS require some form of urgent intervention. The approach is

determined by the valve morphology and by the presence of associated defects. In its most extreme

form, critical AS may be associated with underdeveloped left-sided cardiac chambers and therefore may

represent a form of hypoplastic left heart syndrome. In these cases, single-ventricle palliation must be

undertaken. For patients with adequate left-sided chambers, relief of AS may be achieved by one of the

following three approaches: percutaneous balloon valvuloplasty, surgical valvotomy, or aortic valve

replacement. Balloon valvuloplasty is generally considered the procedure of choice when the aortic

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valve annulus is adequate and there are no associated cardiac defects. Alternatively, surgical valvotomy

may be accomplished by closed or open techniques. The closed approach is performed using

cardiopulmonary bypass, but without aortic cross-clamping. Dilators of increasing size are passed

through a ventriculotomy in the left ventricular apex and advanced across the aortic valve. Some

centers prefer open surgical valvotomy, which allows a precise valvotomy under direct vision, although

aortic cross-clamping with cardioplegia is necessary and results are similar to transventricular dilation.

In all cases, the goal of therapy is to relieve stenosis without creating excessive aortic insufficiency.

Dramatic clinical improvement is expected following balloon or surgical valvotomy, and early survivals

of greater than 80% have been reported regardless of approach.91,92 The incidence of aortic

insufficiency is slightly higher following balloon valvotomy. In most cases, however, stenosis will recur

and repeat valvotomy or aortic valve replacement will eventually be required. Aortic valve replacement

is problematic in the neonate due to small patient size. In these cases, many consider the best valve

replacement to be a pulmonary autograft (Ross procedure)93 with enlargement of the aortic annulus

(Konno aortoventriculoplasty).94 The Ross–Konno procedure has been used successfully for neonates

with critical AS in whom the aortic annulus is hypoplastic and for selected patients in whom

valvuloplasty was unsuccessful. Survival following the Ross–Konno procedure in infants has been shown

to be excellent.95 Growth of the pulmonary autograft has been documented, thereby making it an ideal

valve replacement for children. Unfortunately, as part of the Ross procedure, the pulmonary valve must

be replaced using a cryopreserved homograft that does not grow, and homograft replacement must be

anticipated at intervals as the patient grows.

In contrast to infants with critical AS, older children with valvar AS usually present with less severe

stenosis (mild or moderate), and most are asymptomatic. Symptoms of angina, syncope, and CHF are

not commonly reported. Congenital valvar AS is a progressive lesion, however, and survival is

dependent on the severity of stenosis and the rate of its progression. Sudden cardiac death is the most

common cause of mortality. Endocarditis occurs in less than 1% of patients. The diagnosis of valvar AS

in older children can frequently be made on physical examination. There is a classic systolic crescendo–

decrescendo murmur at the upper sternal border, which radiates to the neck. An ejection click is often

present. A visible apical impulse is suggestive of significant left ventricular hypertrophy. In severe

cases, the pulse may be weak and delayed (pulsus tardus et parvus). The ECG shows left ventricular

hypertrophy. The chest radiograph is usually normal. Echocardiography accurately defines the level of

stenosis and its severity. Using Doppler techniques, the pressure gradient across the stenotic valve may

be estimated using a simplified form of Bernoulli’s equation, P = 4V2, where P is the pressure gradient

and V is the peak flow velocity. Cardiac catheterization is generally reserved for therapeutic

intervention.

All patients with severe valvar AS should undergo intervention, as should all symptomatic patients

with moderate stenosis. Asymptomatic patients with mild or moderate stenosis are generally observed.

As described previously for critical AS, the techniques used to relieve AS in older patients include

percutaneous balloon valvuloplasty, surgical valvulotomy, and valve replacement. Balloon valvuloplasty

is usually performed as the primary intervention, and is associated with a success rate of nearly 90%

and a mortality of less than 1%.96 Open surgical valvotomy is an alternative approach with similar

results.97 For valves that are severely dysplastic, develop restenosis after intervention, or become

insufficient as a result of prior intervention, valve replacement may be necessary. For older children,

there are more options for valve replacement. The choices include mechanical prostheses, bioprosthetic

valves, and tissue substitutes, such as porcine xenografts, cryopreserved human allografts, and

pulmonary autografts (Ross procedure). The mechanical valves are the most durable, but require

chronic anticoagulation. The bioprosthetic and tissue valves do not require long-term anticoagulation,

but tend to deteriorate over time (with the exception of the pulmonary autograft). The pulmonary

autograft has the potential advantage of growth but the homograft used to replace the pulmonary valve

will require replacement. Selection of the appropriate replacement valve is a complex decision that

requires input from all involved parties.

Subvalvar AS occurs below the level of the aortic valve and may be discrete (80%) or diffuse (20%).

Discrete (or membranous) subaortic stenosis is rarely seen in infants and tends to progress over time.

This lesion consists of a crescentic or circumferential fibrous or fibromuscular membrane that protrudes

into the left ventricular outflow tract. The pathogenesis of discrete subaortic stenosis is unknown, but it

is thought to be an acquired lesion that develops secondary to a congenital abnormality of the left

ventricular outflow tract in which abnormal flow patterns lead to endocardial injury with resultant

fibrosis. Although the aortic valve leaflets are usually normal in discrete subaortic stenosis, the

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