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size, shape and course of the duct as well as its diameter at
the pulmonary and aortic ends. These factors help determine
the type of occluder device chosen at the time of intervention
(See Fig. 23.8 ).
Aortopulmonary Window
The aortopulmonary (AP) window is a rare congenital defect
defi ned as a direct communication between the pulmonary
artery and the ascending aorta. While physiologically similar
to a large PDA, most cases of AP window have a defect in
the proximal portion of the AP septum, between the semilunar valves and the pulmonary bifurcation. Nearly half of
affected patients have associated defects including aortic origin of the right pulmonary artery, interrupted aortic arch,
tetralogy of Fallot or coronary anomalies [ 46 – 49 ].
Surgical closure is indicated for nearly all patients with
AP window. A small AP window may present in adulthood
with a continuous murmur and left heart enlargement. If the
AP window is large and nonrestrictive, however, the patient
will present with pulmonary hypertension, cyanosis and
Eisenmenger physiology. In the patient with an unoperated
AP window, CCTA should inspect and confi rm not only the
presence of a window but also associated lesions. For those
with repaired AP windows, serial late CCTA should evaluate
the aortic and pulmonary artery architecture.
Coarctation of the Aorta/Interrupted Aortic Arch
Coarctation of the aorta (CoA) is defi ned as a focal narrowing
of the aorta. Most commonly the area of narrowing is just
distal to the origin of the left subclavian artery at the insertion
of the ductus arteriosus. This “juxtaductal” tissue of the aorta
has characteristics similar to ductal tissue leading to further
constriction in the post-natal period. This single theory does
not fully explain the pathophysiology since there also exists
a diffuse form of CoA characterized by hypoplasia of the
transverse arch.
This malformation may occur in isolation (simple CoA)
or in conjunction with other abnormalities (complex CoA).
Complex CoA is often associated with a bicuspid aortic
valve, subaortic stenosis, VSDs, mitral valve abnormalities
such as parachute mitral valve, intracranial aneurysms or
Turner syndrome.
When discovered in infancy, CoA is most often repaired
surgically. Current surgical techniques include resection of
the CoA with end-to-end anastomosis, subclavian fl ap
aortoplasty, patch aortoplasty and interposition jump graft.
Each technique has specifi c advantages, disadvantages and
associated long-term complications. Native lesions identifi ed
in the adolescent or young adult are sometimes treated with
balloon angioplasty but there may be residual stenosis,
restenosis or aneurysm formation at the intervention site
[ 50 ]. Stent implantation is a favorable approach for select
patients with both native CoA and recoarctation and there are
long-term studies demonstrating acceptable safety and effi cacy [ 36 , 51 – 55 ].
Complications in the patient with unoperated CoA are
numerous and include systemic arterial hypertension,
accelerated coronary artery disease, stroke, aortic dissection
or rupture, congestive heart failure or intracranial hemorrhage
[ 56 ]. Late complications in operated CoA include
recoarctation, aortic dilation and aortic dissection. Thus, lifelong followup and late postoperative imaging via CCTA or
CMR are imperative for the patient with CoA, even in the
setting of an acceptable surgical or percutaneous result.
CCTA offers signifi cant advantages in the assessment
of the patient with CoA who has previously undergone
transcatheter therapy, particularly stenting. Many transcatheter devices including stents create signifi cant signal
void artifact precluding an accurate assessment of the
anatomy of interest on CMR. In contrast, CCTA provides
an accurate assessment of the lumen of the stented segment and surrounding anatomic structures without signifi cant artifact.
The CCTA exam in a patient with native CoA or recoarctation should include the dimensions and anatomy (such as
aneurysm and dissection) of the CoA segment, precise measurements of the entire aortic arch (which may be hypoplastic) and description of collateral vessels bypassing the region
of stenosis [ 57 ]. Because of the risk of accelerated coronary
artery disease, special attention should be paid to the coronary arteries. Finally, associated congenital cardiac lesions
including other forms of left ventricular outfl ow tract
Fig. 23.8 Oblique sagittal view demonstrates a small patent ductus
ateriosus ( arrow ). Ao Aorta, MPA main pulmonary artery
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obstruction (bicuspid aortic valve, subaortic stenosis) and
mitral valve anomalies should be excluded.
Interruption of the aorta is defi ned as a complete separation
between the ascending and descending aorta. There are
multiple branching patterns but the morphology can be
generally classifi ed as Type A (interruption distal to the left
subclavian artery), Type B (between the carotid and
subclavian arteries) or Type C (between the carotid arteries)
[ 58 ]. Aortic interruptions may be associated with other
congenital anomalies including transposition of the great
arteries, conotruncal anomalies with a VSD or subaortic
stenosis. Surgical therapy is required to restore continuity of
the aorta and concomitant defects. Late complications
primarily involve restenosis at the site of prior surgical repair.
CCTA may be used in this population for characterization of
the aorta, arch anatomy and other cardiac defects as well as
evaluation of post-operative complications and/or to assess
the effi cacy of prior interventions.
Congenital Valvar Disease
Bicuspid Aortic Valve/Valvar Aortic Stenosis
A bicuspid aortic valve (BAV) is one of the most common
congenital heart abnormalities, affecting slightly more than
1 % of the general population [ 4 ]. The term “bicuspid” is a
misnomer. The valve apparatus is typically composed of
three cusps but two of the cusps are fused. The resulting
valve is functionally bicuspid. Most commonly this fusion is
along the left and right coronary cusps. Most congenitally
malformed aortic valves are bicuspid but the aortic valve can
be unicuspid, quadricuspid or simply dysplastic. The aortic
annulus may be hypoplastic. Rheumatic heart disease
accounts for a signifi cant proportion of acquired aortic valve
stenosis in the pediatric population.
BAV can lead to aortic stenosis, aortic regurgitation or
mixed valvar disease with both stenosis and regurgitation.
Importantly, BAV is associated with abnormalities in the
aortic media which can cause dilation of the proximal
ascending aorta and which are unrelated to the severity of
valve disease [ 59 ]. Thus, BAV is a disease both of the aortic
valve and of the aorta. BAV is also associated with an
increased risk of coarctation, interrupted aortic arch [ 60 ] and
coronary artery anomalies [ 61 ].
Transthoracic echocardiography is the primary noninvasive modality in the evaluation of aortic valvar disease.
This technique provides an assessment of the valve (degree
of stenosis/regurgitation), ventricular size/function and the
proximal ascending aorta and arch. In patients with poor
acoustic windows (e.g., obesity, pulmonary disease, chest
wall deformities), CCTA provides an alternate method to
assess valve morphology and dimensions. CCTA estimates
of valve area correlate highly with TEE dimensions [ 62 ].
Importantly, particularly in the patient with BAV, CCTA
permits for comprehensive imaging of the aorta in addition
to the aortic valve. Complementary three-dimensional
volume-rendered reconstructions performed with off-line
analysis may provide important information about aortic
dimensions that can guide management.
Subvalvar Aortic Stenosis
Subvalvar aortic stenosis (subAS) is most frequently caused
by a fi brous membrane or ring of tissue although it can also
assume a diffusely hypoplastic or focal tunnel-type obstruction. Although it can occur in isolation, more than half of cases
are associated with another congenital defect such as VSD,
CoA, Shone’s complex, PDA, persistent left SVC or valvar
aortic stenosis [ 63 , 64 ]. There is also an association with mitral
valve abnormalities [ 65 , 66 ]. The degree of stenosis may
remain stable but most tend progress over time. Additionally,
subAS may be associated with aortic regurgitation. In contrast
to valvar aortic stenosis, this lesion is not amenable to catheter-based interventions and the management is surgical when
indicated. Unfortunately, there is a signifi cant risk of recurrence despite surgical intervention. Thus, a history of subAS
or associated defects should prompt close inspection of the left
ventricular outfl ow tract in patients undergoing CCTA examinations (See Fig. 23.9 ).
Supravalvar Aortic Stenosis
Supravalvar aortic stenosis (supraAS) is defi ned as stenosis
immediately above the sinuses of Valsalva. This is an uncommon occurrence in the general population but affects 30–50 %
of individuals with Williams Syndrome (7q11.23 deletion
syndrome) [ 67 , 68 ]. Features of Williams syndrome include
supraAS, peripheral pulmonary stenosis, a characteristic
facial appearance, developmental delay and often a particularly cheerful and outgoing personality. Associated lesions
include aortic valve abnormalities, Shone’s complex and coronary artery abnormalities. Individuals with supraAS are
thought to be at risk of premature atherosclerosis due to continuous exposure of the coronary arteries to supranormal
pressures. The treatment of choice, due to the proximity to the
coronary arteries, is surgical. CCTA may assist in the initial
diagnosis of this defect and may furthermore provide insight
into the coronary artery anatomy and late outcomes in this
population that have not yet been well established.
Pulmonary Stenosis
Congenital pulmonary valvar stenosis (PS) is most often an
isolated defect, but it may also occur in combination with
subvalvar stenosis. A wide variety of malformations of the
valve can be present including the classical form (a domeshaped valve), a hypoplastic valve annulus, thickened or
fused leafl ets or even a dysplastic, myxomatous valve [ 69 ].
In cases of signifi cant PS, the right ventricle and right ventricular outfl ow tract become hypertrophied and there is
often dynamic subvalvar obstruction. Additionally, severe PS
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is typically accompanied by poststenotic dilation of the main
pulmonary artery. Valvar PS is encountered more frequently
in individuals with Noonan syndrome [ 70 – 72 ].
Severe or critical PS diagnosed at any age is generally
treated with balloon valvuloplasty. However, in complex
cases (such as those with a hypoplastic pulmonary valve
annulus, severe pulmonary insuffi ciency or subvalvar/supravalvar PS), surgery is usually the treatment of choice. Surgery
is also reserved for patients with dysplastic valves that often
do not respond to transcatheter therapy. An important late
complication following either balloon valvuloplasty or surgical valvotomy is pulmonary regurgitation.
The anterior position of the pulmonary valve and the right
ventricular outfl ow tract may preclude complete evaluation
with echocardiography, particularly in the patient with prior
surgery. CCTA is well suited to image this patient population
for delineation of the right ventricular outfl ow tract, pulmonary valve annulus and distal structures including the branch
pulmonary arteries. Pre-interventional assessment of pulmonary valve anatomy and dimensions may help predict suitability for balloon valvuloplasty. Lastly, CCTA can provide
quantifi cation of right ventricular size and function in
patients following transcatheter or surgical intervention who
have residual PS or regurgitation.
Other Lesions
Tetralogy of Fallot
Tetralogy of Fallot (TOF) is the most common cause of cyanotic CHD. It is comprised of the following: malalignment
VSD, right ventricular outfl ow tract obstruction (RVOTO),
overriding aorta and right ventricular hypertrophy secondary
to RVOTO. Anterior and superior displacement of the outlet
(infundibular) septum is the defi ning feature and accounts
for the fi rst three components of this defect. Right ventricular
hypertrophy is a consequence of RVOTO. The degree of
RVOTO varies and may include dysplastic pulmonary valve
leafl ets as well as subpulmonary or pulmonary arterial
involvement.
TOF can be “syndromic” (associated with additional noncardiac congenital anomalies) or “nonsyndromic.” Important
syndromes associated with TOF include DiGeorge syndrome
(22q11.2 microdeletion), Down syndrome (Trisomy 21),
Edward syndrome (Trisomy 18) and Patau syndrome
(Trisomy 13). TOF may be associated with other congenital
cardiac abnormalities including ASDs, left SVC to coronary
sinus or a right aortic arch. Approximately 5–10 % will have
coronary anomalies [ 73 – 75 ] including the left anterior
descending artery arising from the right coronary artery, circumfl ex artery arising from the right coronary artery, a large
conus branch or a single coronary artery system.
The complete intracardiac repair of TOF includes relief of
RVOTO and patch closure of the VSD. Operative repair of
RVOTO may occur via a variety of techniques. Patients with
a restrictive pulmonary valve annulus may require a longitudinal incision of the pulmonary valve with subsequent patch
augmentation (transannular patch) and augmentation of the
pulmonary arteries when indicated. In more severe forms
(pulmonary atresia), a right ventricular-to-pulmonary artery
conduit is performed to establish continuity between the
right ventricle and pulmonary arteries.
ab
Fig. 23.9 Oblique axial ( a ) and sagittal ( b ) views demonstrating a discrete subaortic membrane ( arrowhead ) in a patient with a bicuspid aortic
valve and coarctation of the aorta. Note the calcifi cation of the anterior mitral valve leafl et ( arrow ). Ao aorta, LV left ventricle
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Following these repairs, there may be signifi cant residual
pulmonary regurgitation. This is often well tolerated until adolescence and young adulthood, when progressive right ventricular enlargement and systolic dysfunction may cause
dyspnea on exertion, chest pain, ventricular arrhythmias or
even sudden cardiac death. Therefore, symptomatic patients
with these fi ndings should be considered for surgical pulmonary valve replacement. Novel transcatheter pulmonary valve
implantation techniques are currently being used (such as the
Melody® Transcatheter Pulmonary Valve, Medtronic, Fridley,
MN and Edwards SAPIEN Pulmonic Transcatheter Heart
Valve, Edwards LifeSciences LLC, Irvine, CA) to address pulmonary valve disease while avoiding the risks associated with
multiple re-operations in this complex group of patients [ 76 ].
Non-invasive imaging studies obtained routinely or in
anticipation of pulmonary valve replacement should assess
right and left ventricular volumes and function, anatomy and
size of the right ventricular outfl ow tract, presence/absence
of residual VSD and anatomy of the proximal and distal
branch pulmonary arteries (See Fig. 23.10 ). The distance
between the coronary arteries and the sternum should be
examined and, care should be taken to examine the course of
the left anterior descending artery as it may cross over the
right ventricular outfl ow tract. Finally, CCTA plays an
important role in pre-procedure planning for transcatheter
interventions. Particular attention should be paid to conduit
or right ventricular outfl ow tract dimensions and the distance
between the coronary arteries and the RVOT as cases of catastrophic coronary artery compression during transcatheter
valve implantation have been reported [ 77 , 78 ].
Lastly, progressive aortic root dilation is frequently
demonstrated in the adult tetralogy of Fallot population
despite adequate surgical repair [ 79 ]. This process may be
due to an inherent aortopathy rather than a sequelae of the
intracardiac defects [ 80 ]. Therefore, CCTA assessment of
the adolescent or adult patient with TOF should include
close inspection of the aortic anatomy at the time of
examination. It can be helpful to index the aortic root size
to body surface area and age using standard nomograms
[ 81 , 82 ] .
Congenital Heart Defects of Great
Complexity
Double Outlet Right Ventricle
Double outlet right ventricle (DORV) is a type of ventriculoarterial discordance in which both great arteries arise 50 %
or more from the right ventricle. DORV is not a single congenital defect, but rather a continuum of defects best understood by the relationship by the relationship between the
great vessels and the position of the VSD. The location of the
VSD further corresponds with each specifi c physiologic
subtype [ 83 ].
The location of the VSD may be subaortic, subpulmonic,
doubly-committed (a single defect lying inferior to both the
aorta and pulmonary artery) or remote from the great arteries
(in other words noncommitted). The relationship of the great
arteries is defi ned by the position of the aorta relative to the
ab
Fig. 23.10 The oblique coronal ( a ) and sagittal ( b ) views demonstrate
the long-term complications associated with tetralogy of Fallot.
Lifelong pulmonary insuffi ciency is a consequence associated with
prior surgical palliations ( arrowhead ) that results in a dilated right ven-
tricle ( RV ) when compared to the size of the left ventricle ( LV ). Prior
palliative procedures often result in branch pulmonary artery stenosis
often requiring transcatheter therapy ( arrows ). RA right atrium
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pulmonary artery. Although normal relationships may exist,
typically the aorta lies rightward and posterior to the pulmo-
nary artery. Alternatively, the aorta may lie side by side or
rightward and anterior to the pulmonary artery with the sub-
pulmonic variant (d-TGA physiology) of DORV.
PS is commonly observed in DORV, occurring in over
50 % of cases [ 84 – 86 ]. Other associated anomalies include
secundum ASDs, relative hypoplasia of the left ventricle,
mitral valve anomalies (atrioventricular attachments to the
septum), a persistent left SVC, and coronary artery anomalies. CoA or arch hypoplasia commonly occurs in the subpulmonary variant of DORV (Taussig-Bing anomaly). Although
these associated defects are relatively uncommon, when present, they create a signifi cant impact on the physiology of the
underlying defect as well as surgical management options.
Given the variety of anatomic relationships and associated features, surgical palliative approaches to repair of
DORV are diverse. Repairs often include closure of the VSD
such that blood fl ow is routed (“tunneled”) to restore continuity between the left ventricle and the aorta (subaortic
DORV). An arterial switch procedure may be performed to
restore left ventricular-aortic continuity in patients with
DORV with subpulmonary VSD. Associated features such
as ASDs and atrioventricular valve chordae are addressed
simultaneously. In some cases, biventricular repair is not
always possible, and a single ventricle palliation is performed (e.g., staged Fontan procedure). Occasionally a “one
and one-half ventricle” repair may be chosen. In this scenario, a cavopulmonary anastomosis (usually a bidirectional
Glenn shunt) partially unloads the right ventricle. Systemic
venous return from the SVC will be via the Glenn to the
pulmonary artery; the right ventricle will pump only IVC
systemic venous return to the lungs.
Late outcomes of DORV are variable and are chiefl y determined by the underlying anatomy and type of surgical palliation. Complications include obstruction of the right
ventricular-to-pulmonary artery conduit, stenosis of interventricular tunnels, subaortic stenosis, and neo-aortic valve regurgitation or neo-aortic root dilation (in patients undergoing
arterial switch). CCTA is suitable in the pre- operative assessment of this lesion as it accurately describes the three-dimensional relationship of the VSD to surrounding structures such
as the great arteries and coronary arteries. Furthermore, it provides an accurate assessment of post- operative anatomic
changes particularly to conduits and the neo-aorta.
D-Transposition of the Great Arteries
D-Transposition of the great arteries (TGA) is one of the
most common severe congenital cardiac anomalies and is
often lethal to affected infants if intervention is not performed. Although TGA may accompany other complex
CHD (for example DORV), this term is most commonly
used to describe isolated ventriculoarterial discordance. In
other words, the right ventricle gives rise to the aorta and
coronary arteries and the left ventricle gives rise to the pulmonary artery (See Fig. 23.11 ).
ab
Fig. 23.11 An oblique saggital view ( a ) and oblique axial view ( b )
demonstrate the the key anatomic fi ndings in d-transposition of the
great arteries. The oblique saggital view demonstrates ventriculoarterial
discordance between the right ventricle ( RV ) and the aorta ( AO ). The
oblique axial view displays the anterior-posterior relationship of the
great arteries. MPA main pulmonary artery, AoV aortic valve
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The name d-TGA arises from the most common anatomic
relationship of the aortic and pulmonary valves resulting in
this anatomic relationship. The aorta is transposed with pulmonary artery such that the aorta is anterior and rightward of
the pulmonary artery. Recall that, the prefi xes d- and l-
describe only the anatomic position of the aortic and pulmonary valves and not the arrangement of the remaining
segmental cardiac anatomy. Associated defects include
VSD, left ventricular outfl ow tract obstruction, CoA and
coronary artery abnormalities.
The physiology of d-TGA is often described as two circulations “in parallel” in contrast to the normal circulation, which
occurs “in series.” The systemic venous return passes from the
right atrium into the right ventricle, then to the aorta and systemic arterial circulation without ever reaching the lungs.
Similarly, the pulmonary venous return enters the left atrium
and left ventricle only to return to the pulmonary arterial bed.
Without a substantial mixing lesion, this parallel circulation is not sustainable and can quickly result in death.
Continuous prostaglandin infusion can maintain patency of
the ductus arteriosus and facilitate mixing. In the absence of
a signifi cant ASD or VSD, a balloon atrial septostomy may
be necessary to stabilize an infant until defi nitive surgical
repair can be performed. Prior to the availability of balloon
septostomy, a surgical excision of atrial tissue without cardio-pulmonary bypass was performed (the Blalock- Hanlon
procedure).
Before the advent of improved coronary artery surgical
techniques, redirecting blood at the atrial level was associated with lower mortality than attempting to switch the aorta
and pulmonary arteries to their typical anatomic positions.
The Mustard and the Senning procedures “baffl e” pulmonary venous return to the right ventricle and systemic venous
return to the left ventricle. This allows oxygen-rich blood to
reach the systemic circulation via the morphologic right ventricle and oxygen-poor blood to reach the lungs via the morphologic left ventricle.
While the redirection of atrial blood fl ow restores a normal circulation, there are negative late sequelae. The superior and inferior systemic venous baffl es that redirect venous
return from the SVC and IVC (respectively) to the morphologic left ventricle can develop baffl e leaks or stenosis.
Similarly, the pulmonary venous baffl e may develop stenosis
as well. Finally, the morphologic right ventricle is not well
suited to tolerate lifelong systemic blood pressure. This ultimately leads to hypertrophy, dilation and failure.
In the patient with a Mustard or Senning palliation, CCTA
is valuable to assess not only the complex anatomy and associated post-operative changes encountered with this population, but also the late onset complications such as baffl e
obstruction and residual hemodynamic lesions (See
Fig. 23.12 ). Although CMR is frequently performed to assess
quantifi cation of RV volumes and function, CCTA may be
utilized to quantify this data in this population as well.
ab
Fig. 23.12 An oblique saggital view ( a ) demonstrates the anatomic
appearance of the pulmonary venous baffl e ( arrows ) in this patient with
d-transposition of the great arteries and an atrial switch (Mustard procedure). The coronal view ( b ) reveals the systemic venous baffl e.
Although pacing leads and contrast opacifi cation in the systemic right
ventricle impair image quality, systemic venous baffl e obstruction can
still be seen ( arrowhead ). Secondary fi ndings such as a prominent azy-
gous vein may suggest the presence of this anomaly
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Contemporary surgical repair of d-TGA is the arterial
switch procedure, in which the aorta and pulmonary
arteries are switched to restore ventriculoarterial
concordance. This requires excision and mobilization of
the proximal coronary arteries and surrounding “buttons”
of aortic tissue along with the Lecompte maneuver to bring
the pulmonary artery to the anterior position. Late sequelae
following the arterial switch include coronary artery
abnormalities, myocardial ischemia, stenosis at the great
artery anastomoses or arrhythmias. There may also be neoaortic root dilation and neo-aortic valve regurgitation
[ 87 – 90 ].
In the patient who has undergone an arterial switch procedure, CCTA is an ideal modality for assessment of the coronary arteries [ 91 ]. It also is extremely useful for examining
the great artery anastomoses and neoaorta. In particular, one
should carefully inspect the pulmonary arteries to exclude
the presence of branch pulmonary artery stenosis as a result
of the Lecompte maneuver.
Congenitally Corrected Transposition
of the Great Arteries
In congenitally corrected transposition of the great arteries
(CCTGA), both atrioventricular and ventriculoarterial discordance are present. Systemic venous return courses from
the right atrium through the mitral valve and morphologic
left ventricle, ultimately reaching the pulmonary arterial bed
via the pulmonary valve. Similarly, pulmonary venous return
courses from the left atrium through the tricuspid valve into
a morphologic right ventricle and ultimately the systemic
circulation via the aortic valve. In other words, “two wrongs
make a right.” Other terms for this condition include “l-TGA”
or ventricular inversion.
Patients with CCTGA usually have a normal (levocardia)
or midline (mesocardia) position of the heart within the
chest. However, 20 % of patients have dextrocardia, in which
the heart is on the right side of the chest and 5 % will have
situs inversus [ 92 – 95 ].
Over 90 % have associated lesions, most commonly VSD,
left ventricular outfl ow tract obstruction or abnormalities of
the systemic atrioventricular valve (morphologic tricuspid
valve) such as Ebstein-type malformations.
The most common late complications associated with
this condition are systemic atrioventricular valve regurgitation and systemic (morphologic right) ventricular dysfunction and arrhythmias third degree atrioventricular
(AV) block is particularly frequent [ 96 , 97 ]. CCTA is
helpful for defi ning the underlying anatomy and associated defects for patients with CCTGA (See Fig. 23.13 ). It
also is an ideal tool for assessment of coronary venous
anatomy to facilitate lead placement at the time of pacemaker implantation.
ab
Fig. 23.13 The oblique saggital ( a ) and coronal ( b ) images display the
underlying anatomy and demonstrate ventriculoarterial discordance in
this patient with congenitally corrected transposition of the great arteries (CCTGA). Here, the systemic right ventricle ( RV ) is in communica-
tion with the aorta ( Ao ). Further, there is dilation of the main pulmonary
artery ( MPA ) segment, suggesting right ventricular outfl ow tract
(RVOT) obstruction. RVOT obstruction is often associated with a large
ventricular septal defect. LV left ventricle, SVC superior vena cava
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Truncus Arteriosus
In truncus arteriosus, a single great artery (rather than two,
aorta and pulmonary artery) arises from the base of the heart.
This single artery then gives rise to the coronary arteries, pulmonary arteries and aorta. The truncal valve is usually
trileafl et (69 %) but regurgitation is not uncommon. The
classifi cation scheme presented here, Collett and Edwards,
defi nes truncus arteriosus by the relationship of the pulmonary arteries [ 98 ]. A Type I truncus has a short common pul-
monary arterial trunk which gives rise to both pulmonary
arteries. Type II is defi ned by the absence of a main pulmonary artery segment. The left and right branch pulmonary
arteries arise in close proximity to one another from the
ascending truncal artery. In type III, there is no main pulmonary artery segment, and the left and right pulmonary arteries
arise separately at a distance from one another. Type IV is
defi ned by the absence of pulmonary arteries. Here, the lungs
are supplied by aortopulmonary collateral vessels. This type
is more accurately classifi ed as pulmonary atresia and is no
longer considered within the spectrum of truncus arteriosus.
Truncus arteriosus is usually an isolated phenomenon but
has been reported in patients with DiGeorge syndrome
(22q.11.2 microdeletion). Associated conditions include aortic arch anomalies including right aortic arch, coarctation of
the aorta and interruption of the aorta. Other commonly
associated defects include PDA, absence of a pulmonary
artery and persistent left SVC.
This defect usually presents in the newborn period and,
when diagnosed suffi ciently early (before the development
of severe pulmonary vascular disease), is treated by surgical
palliation. Surgical repair of truncus typically utilizes a
conduit from the right ventricle to either the main pulmonary
artery segment (Type I) or the branch pulmonary arteries
(Types II and III). The long-term survival following initial
successful repair continues to improve and therefore the
number of adolescents and adults with this complex lesion
will continue to grow. For this reason, it is imperative to
recognize late complications associated with this defect.
CCTA evaluation should include close inspection of the right
ventricle-pulmonary artery conduit to determine the
presence/absence of stenosis or calcifi cation, anatomy of the
proximal and distal branch pulmonary arteries, neo-aortic
root dilatation, and ventricular volumes and function.
Single Ventricle Lesions
Among the most complex congenital heart lesions are those
with severe hypoplasia or atresia of the left or right ventricle.
Consequently, these patients are reliant on a single ventricle
to perfuse both the pulmonary and systemic vascular beds.
The full spectrum of single ventricle lesions is beyond the
scope of this text. Nonetheless, the most important variations
are tricuspid atresia and hypoplastic left heart syndrome.
Despite the wide variation in single ventricle pathology, the
types of surgical palliations ultimately share a similar
physiologic goal.
As its name suggests, tricuspid atresia is defi ned by the
absence of a tricuspid valve. Initially, blood returning to the
right atrium passes through an ASD to the left heart and
mixes with pulmonary venous return. The right ventricle is
usually atretic or hypoplastic; it receives blood from the left
ventricle via a VSD. If there is ventriculoarterial concordance,
the pulmonary arteries are often small and rely upon the duct
for pulmonary blood fl ow. Alternatively, if there is
ventriculoarterial discordance, the aorta arises from the
rudimentary right ventricle, and, upon occasion, there may
be aortic obstruction requiring ductal patency.
Hypoplastic left heart syndrome (HLHS) describes a
spectrum of left-sided abnormalities that are insuffi cient to
meet the demands of the systemic circulation. They are
further qualifi ed by stenosis or atresia of mitral and aortic
valves. In other words: there may be mitral stenosis and
aortic stenosis (MS/AS), mitral stenosis and aortic atresia
(MS/AA) or mitral atresia and aortic atresia (MA/AA) [ 99 ].
If the ascending aorta is severely atretic, the carotid and
coronary arteries rely upon retrograde ductal blood fl ow for
adequate perfusion.
In most cases of single ventricle physiology, either the
systemic or pulmonary bed relies upon patency of the ductal
artery. If the ductal artery constricts or becomes stenotic, the
results can be catastrophic. Ductal patency can be maintained
with a continuous infusion of prostaglandin and more
recently stents may be delivered via cardiac catheterization.
Often a surgical shunt must be created to maintain a more
stable blood supply.
Modern congenital heart surgery can be traced to 1944
with the creation of a systemic to pulmonary shunt conceived
of by Helen Taussig and performed by Alfred Blalock with
assistance from Vivian Thomas [ 100 ]. The original or classic
Blalock-Taussig shunt (BT shunt) is a direct anastomosis of
the subclavian artery to the ipsilateral pulmonary artery.
Adaptations in this surgical technique led to the development
of the modifi ed BT shunt in which an artifi cial (e.g., Gore-
Tex) graft connects the subclavian artery to the pulmonary
artery without disrupting the integrity of the subclavian
artery from the affected arm (See Fig. 23.14 ) [ 101 ]. Other
systemic to pulmonary arterial shunts include the Waterston
shunt (ascending aorta to right pulmonary artery), the Potts
shunt (descending aorta to left pulmonary artery), and the
Cooley shunt (proximal ascending aorta to right pulmonary
artery within the pericardium). An alternative strategy used
sometimes for the palliation of hypoplastic left heart
syndrome is the Sano shunt , a conduit located between the
right ventricle and the pulmonary artery. Contemporary
central shunts utilize an artifi cial graft between the ascend-
ing aorta and the main pulmonary artery.
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Although they are stable sources of pulmonary blood
fl ow, systemic to pulmonary arterial shunts often lead to distortion of the pulmonary artery architecture because blood
fl ow is often directed towards one pulmonary artery. As pulmonary vascular resistance decreases with age, congestive
heart failure may develop as a result of excessive pulmonary
blood fl ow. Pulmonary hypertension may develop. Most
importantly, these shunts can become kinked, occluded, narrowed or thrombosed, compromising pulmonary blood
supply.
In some circumstances, complete repair is not immediately feasible or must be delayed. Here, surgical banding of
the pulmonary arteries is often utilized as an initial palliation. Restricting the diameter of the pulmonary arteries can
protect the pulmonary vascular bed from excessive blood
fl ow. Surgical bands can be placed around either the main
pulmonary artery (MPA) or the proximal branch left and
right branch pulmonary arteries. Unfortunately, banding can
cause negative sequelae, particularly if the band was placed
on a young patient who later outgrows the size of the band.
Occasionally, the band may migrate distally, occluding one
pulmonary artery and resulting in unopposed pulmonary
arterial fl ow to the opposite branch. Post-stenotic dilation
may result if the band that is placed too tightly. Structures
proximal to this band gradient are also exposed to increased
afterload, and, as a result, pulmonary valve regurgitation,
right ventricular enlargement and dysfunction and tricuspid
valve insuffi ciency may ensue.
As patients grow and pulmonary vascular resistance
drops, BT shunts typically can no longer provide adequate
pulmonary blood fl ow. The Glenn shunt (bidirectional) is an
end-to-side anastomosis of the SVC to the undivided
ab
cd
Fig. 23.14 Aortopulmonary
shunts. ( a ) The classic
Blalock-Taussig shunt, ( b ) a
modifi ed Blalock-Taussig
shunt, ( c ) a Waterston shunt,
and ( d ) the Potts shunt
(Reprinted from Khairy et al.
[ 101 ] with permission of
Wolters Kluwer)
23 Computed Tomographic Angiography in the Assessment of Congenital Heart Disease and Coronary Artery Anomalies
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pulmonary artery. It is most often performed as the second
stage in a series of staged palliations for single ventricle
physiology. The third stage, the Fontan procedure, is the
fi nal palliative procedure which connects the IVC directly to
the pulmonary artery. The Glenn and Fontan shunts cannot
be safely performed in infancy as pulmonary vascular resistance must fi rst fall substantially, allowing a small gradient
between systemic venous pressure and pulmonary arterial
pressure to drive forward fl ow.
The Fontan procedure has undergone signifi cant evolution since its inception in 1971 [ 102 ]. Earlier techniques uti-
lized an atriopulmonary (right atrial appendage-to-pulmonary
artery) anastomosis. Late-onset complications including
atrial arrhythmias, compression of the pulmonary veins and
thrombus (as a result of severe atrial enlargement) prompted
surgical revisions of this technique. Surgical techniques currently in use utilize conduits made of artifi cial or pericardial
tissue to direct systemic venous return directly to the pulmonary arteries via either intracardiac ( lateral tunnel Fontan ) or
extracardiac ( extracardiac Fontan ) routes. Occasionally, a
fenestration is placed within the Fontan itself to serve as a
“pop-off” for elevated systemic venous return (but at the cost
of cyanosis). If pulmonary vascular resistance remains low
post-operatively, such fenestrations can be later closed percutaneously. Collaterals (aortopulmonary or systemic
venous) are frequent in this population [ 103 – 105 ].
CCTA imaging may be promising in the assessment of the
single ventricle patient to assess late-onset complications
including thrombus within the Fontan, fenestrations, collaterals and single ventricle function [ 106 ]. However, there are
important limitations of this technique. The issues of lowcardiac output, frequent collaterals and asymmetric blood
fl ow between the left and right lungs resulting from prior
cavopulmonary anastomoses create technical challenges for
an accurate gated CCTA examination (See Fig. 23.15 ).
Simultaneous contrast injection from both an upper and
lower extremity will allow dense and homogenous opacifi cation of the entire circulation but can be technically challenging [ 107 ]. Due to these limitations, CMR is often the imaging
modality of choice unless otherwise contraindicated.
Summary
Adults with CHD represent a large and diverse group of
patients with both simple and complex disease. Physicians
who care for patients with CHD challenged by the unique
needs of this rapidly growing population, including the need
for frequent non-invasive cardiovascular imaging. Although
CMR has historically been recognized as the non-invasive
imaging tool of choice in this patient population, advances in
CCTA have allowed it to become an extremely powerful
ab
Fig. 23.15 Oblique sagittal ( a ) and axial ( b ) views demonstrate the
challenges of accurately defi ning Fontan anatomy. Despite an accurate
timing bolus, this is a low cardiac output state leading to accumulation
of contrast in the superior vena cava ( SVC ) and poor opacifi cation of
desired anatomic structures. In addition, collaterals ( arrows ) may create
a “steal phenomenon,” resulting in poor contrast opacifi cation. Further,
incomplete opacifi cation of the IVC diminishes diagnostic accuracy to
assess for thombus in this segment of the cavopulmonary anastomosis.
AAo ascending aorta, LPA left pulmonary artery, RPA right pulmonary
artery
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