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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3676_Библиотеки_им_академика_М_И_Перельмана
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4 Pediatric Cardiac CTA
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Fig. 4.4 The patient had a previous CT exam, performed
without IV contrast. An axial image at the level of the
carina is all that is needed to know that the intrahepatic
IVC is interrupted. The azygous vein (AZ) and the azygous arch which connects the vein to the superior vena
cava (SVC) are enlarged, similar in caliber to the ascending (AAo) and descending (DAo) aorta. The superior surface of the main pulmonary artery (MPA) is also seen
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4.2.4 Case 4.3
This adult patient has been healthy all her life.
She presents to the emergency room with abdominal pain. See Fig. 4.5.
Fig. 4.5 An axial contrast enhances CT image of the
upper abdomen shows that several splenic structures (dot-
ted ellipse) are in the right upper quadrant along with the
stomach (S). The liver (L) is in the right upper quadrant
and the intrahepatic segment of the IVC (white arrow) is
present and the azygous vein is not enlarged. The abdominal aorta (black arrow) is at the midline. Remember that
polysplenia may be found without interruption of the IVC
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4.3 Persistent Left Superior Vena
Cava
Persistent left superior vena cava (PLSVC) is the
most common congenital venous anomaly in the
thorax. Most individuals with PLSVC are asymptomatic throughout their entire life; the reported
incidence of BSVC in the general population is
less than 0.5%. In patients with congenital heart
disease, PLSVC is known to occur much more
frequently, in up to 12%.
PLSVC may occur with or without the presence of a right SVC, i.e., bilateral SVC (BSVC).
When bilateral, the SVCs may be similar or dissimilar in caliber and the brachiocephalic
(innominate) vein may or may not be patent; as a
bridging vein between the SVCs, but is absent in
most (65%).
Systemic venous drainage via a PLSVC most
often occurs via the coronary sinus to the right
atrium (80–92%). If the coronary sinus is
unroofed, deoxygenated blood from the PLSVC
drains to the right and left atria. A PLSVC may
drain entirely to the left atrium through a direct
connection to the roof of the atrium.
Of course, a PLSVC is also found in situs
inversus and when the right SVC is absent. In this
situation venous drainage of the upper body is to
the anatomic right atrium which also lies on the
left.
4.3.2 Case 4.4
4.3.2.1 Patient 1
See Fig. 4.6.
4.3.3 Clinical Presentation
Two newborn patients with congenital heart disease underwent CTA to define intracardiac and
great vessel anatomy; the underlying CHD lesions
will not be discussed. In the course of diagnosis,
in each patient PLSVC was discovered.
4.3.1 Clinical Presentation
An asymptomatic adolescent underwent chest
CT for an unrelated indication.
Fig. 4.6 A coronal oblique view of the thorax shows both
a right (R SVC) and left (L SVC) superior vena cava. The
L SVC drains to the coronary sinus (CS). There was not a
patent bridging vein
4 Pediatric Cardiac CTA
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4.3.4 Case 4.5
4.3.4.1 Patient 2
See Figs. 4.7, 4.8, and 4.9.
Fig. 4.7 A large defect in the intra-atrial septum results
in what is effectively a single atrial chamber. A right (R
SVC) and left (L SVC) drain to the superior aspect of the
right (RA) and left (LA) side of the atria, respectively. The
main pulmonary artery (Asterisk) and aortic arch (AA) are
seen in the midline
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Fig. 4.9 The right (R SVC) and left (L SVC) superior
venae cavae are seen in a 3D surface rendered reconstruction. The wispy, small caliber bridging brachiocephalic
vein (arrows) is anterior to the ascending aorta (AAo) at
the level of the aortic arch
Fig. 4.8 An axial image at the level of the aortic arch
(AA) shows the right SVC (R SVC), the smaller caliber
left SVC (S SVC), and the very small caliber bridging
vein (arrows)
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4.3.4.2 Patient 3
See Figs. 4.10, 4.11, and 4.12.
Fig. 4.10 A less common form of PLSVC is seen, with
persistence of the left SVC (L SVC) and absence of the
right SVC in this patient with normal situs. The L SVC
drains to the coronary sinus (arrow); the roof of the coronary sinus is intact (proved by the difference in density of
contrast in the left atrium (LA) and the coronary sinus).
The ascending aorta (AAo) and main pulmonary artery
(MPA) have a normal relationship
D.M.E. Bardo
Fig. 4.12 A 3D surface rendered reconstruction shows
the position of the brachiocephalic vein (arrow) which
courses anterior to the ascending aorta (AAo) and main
pulmonary artery (MPA) and drains to the left SVC (L
SVC)
Fig. 4.11 The brachiocephalic vein (arrows) courses
from right to left, anterior to the brachiocephalic arteries
(bracket), to the left superior vena cava (L SVC). The
right SVC is absent
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4.4 Coarctation of the Aorta
Coarctation of the aorta refers to focal stenosis of
the aorta. The most common location of coarctation is at the aortic isthmus (also referred to as the
aortic infundibulum), at the insertion of the ductus arteriosus.
The ductus arteriosus is an in utero structure
which allows blood flow from the right side of
the heart to the descending aorta. Histologically,
the ductus arteriosus is composed of loosely
arranged muscular fibers and connective tissue
matrix surrounded by an adventitial layer of
fibrous connective tissue which is contiguous
with the adventitia of the aorta and pulmonary
artery. The regularly spaced internal elastic
lamellae seen in the wall of the muscular wall of
the aorta or pulmonary artery are absent in the
ductus arteriosus [4]. Ductal intima is composed
of a thick irregular cell layer with mucoid material. It was found several years ago that the intima
of the ductus arteriosus which has not closed normally contains a subendothelial internal elastic
lamina [5, 6]. The tissues of the aorta and ductus
arteriosus behave differently after birth when
changes in oxygen tension occur in the blood,
resulting in closure of the ductus arteriosus
within a few days after birth [5, 7].
In the 1979 paper by Ho and Anderson, histological findings showed evidence of extension of
ductal media tissue into the isthmus and proximal
descending aorta (DAo), resulting in varied degrees
of coarctation. The differences in the response of
each tissue type are thereby responsible for coarctation; ductal tissue, infiltrated, or misplaced into the
aorta responding normally, constricts resulting in
narrowing of the aorta. Occasionally, ductal tissue is
suspected to be present in the origin and proximal
left subclavian artery as stenosis of this vessel may
be found in coarctation patients.
Concurrent with coarctation of the aorta, tubular hypoplasia of the aortic arch, and bicuspid
aortic valve are not uncommon. These associations raise concern that a generalized aortopathy
is present in patients so affected.
The classification of coarctation into pre-ductal
and post-ductal lesions has long been known to be
ineffectual. Terminology has changed, for the past
few decades the term juxtaductal is used to describe
the typical location and etiology of aortic coarcta-
tion; for all practical purposes simply using the
word coarctation is adequate. Further, descriptions
of a “shelf” of aortic and ductal intimal tissue which
have been described are also probably not accurate
and the partial or completely circumferential narrowing of the aorta is due to extension of ductal tissue into the media of the aorta.
4.4.1 Clinical Presentation
4.4.1.1 Fetus
The diagnosis of coarctation in the fetus is difficult, perhaps due to challenges in obtaining
acoustic window and the small size of cardiac
structures. Prenatal diagnosis may be suspected if
there is right/left asymmetry of the heart.
4.4.1.2 Infants
It is most common that coarctation of the aorta is
diagnosed in utero or in the newborn period. In
utero, a routine fetal anatomic examination
includes visualization of the aortic arch and
direction of blood flow in the ductus arteriosus
which should be patent.
A murmur that persists beyond the time of
expected closure of the ductus arteriosus suggests a shunt lesion or perhaps coarctation.
Echocardiography is indicated as the first
examination.
The caliber of the aortic arch, brachiocephalic
artery branching, and the presence of ductal
patency, coarctation, atrial or ventricular septal
defect, or lack thereof should be documented.
4.4.1.3 Older Children and Adults
Diagnosis of coarctation of the aorta may escape
clinical awareness either because it is clinically
inconsequential or due to a lack of concern on the
part of the primary physician, even if a murmur
or other signs are present. Bilateral upper and
lower extremity pulse and blood pressure may
not be routinely performed as part of a physical
exam unless the diagnosis is first suspected.
Depending upon the severity of the coarctation development of compensatory collateral
blood flow around the coarctation will be well
developed, with large caliber intercostal, internal
mammary, axillary, and vertebral collateral arteries which supply the descending aorta.
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4.4.2 Case 4.6
A 1-day-old newborn male has a prenatal diagnosis
of hypoplasia of the aortic arch and coarctation of
the aorta. He is treated with intravenous prostaglandin to maintain patency of the ductus arteriosus in
order to maintain blood flow to the descending
aorta. In order to better define the severity of arch
hypoplasia and coarctation as well as branching pattern of the brachiocephalic arteries from the arch
prior to surgical intervention, cardiac CTA was
requested. See Figs. 4.13 and 4.14.
In reporting the findings, it is helpful to the
surgeon to measure the diameter of each segment
of the aorta and the length of the hypoplastic
segments.
Fig. 4.13 A sagittal oblique “candy cane” view of the
aortic arch shows hypoplasia of the transverse (short
bracket) and distal (long bracket) segments of the arch
and elongation of the distal segment as well as discrete
narrowing or coarctation (arrow)
Fig. 4.14 A 3D surface rendered view of the aorta shown
from a posterior perspective reveals the hypoplastic aortic
arch and normal branching pattern of the brachiocephalic
arteries; innominant or brachiocephalic artery (B), left
common carotid artery (LCC), and left subclavian artery
(LSc). The elongated segment of the distal aortic arch and
discrete coarctation (arrow) are also shown
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4.4.3 Case 4.7
A 15-year-old boy reported intermittent left arm
pain at his school physical examination. His
pediatrician heard a low pitched murmur throughout systole and the first part of diastole and found
relatively lower blood pressure in the left upper
extremity compared to the right upper extremity
and decreased femoral pulses. Subsequently, an
echocardiogram showed acceleration of blood
flow velocity in the proximal descending aorta
and discrete coarctation of aorta. Cardiac CTA
was requested in order to better reveal the degree
of coarctation and extent of collateral arteries.
See Figs. 4.15, 4.16, and 4.17.
Fig. 4.15 A coronal reformatted maximum intensity projection (MIP) image of the thoracic descending aorta
reveals large caliber intercostal arterial collaterals (arrows)
draining to the aorta distal to the discrete coarctation (oval)
Fig. 4.16 The DAo and intercostal arterial collaterals
(arrows) and the discrete coarctation (oval) are again seen in
this 3D surface rendered cardiac CTA reconstruction. The
left subclavian artery (LSc), proximal to the coarctation is
large caliber; the aortic arch has been cut away (red arrow)
Fig. 4.17 This 3D surface rendered image of the heart and
collateral arteries shows large caliber right and left internal
mammary (IMA), axillary (red arrow), lateral thoracic
(open arrow), and intercostal (white arrow) arteries
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4.5 Interrupted Aortic Arch
Discontinuity of the lumen of the aortic arch, or
interruption of the aortic arch (IAA), is a rare
congenital vascular anomaly (<1.5%), which can
occur in any arch segment. Interruption just distal
to the left subclavian artery (type A) occurs in
nearly 1/3 of cases, when between the left common carotid artery and the left subclavian artery
(type B) interruption is more common, found in
more than 2/3 of patients, and the rarest variety of
arch interruption which is seen in only 3–5%
occurs between the brachiocephalic and the left
common carotid arteries (type C).
The embryologic basis of the segments of the
aorta, pulmonary arteries, and major branch brachiocephalic arteries lies in the development and
regression of a series of paired vessels which
form within the pharyngeal pouches around the
pharynx. Each pharyngeal pouch contains endodermal tissue, including a vascular component
termed a pharyngeal or aortic arch and neural
crest cells which influence development and
migrate to the heart. Six pairs of aortic arches
connect the dorsal aortae to the aortic sac.
As development proceeds the first, second,
and fifth paired arches involute almost entirely;
with only small remnants persisting as the first
pair forms maxillary and partial external carotid
artery segments. The second paired arches persist
as the stapedial arteries of the middle ear; the
fifth pair completely regresses during the fetal
period in about 50%, and forms only transient
rudimentary vessels in the other 50%. The third,
fourth, and sixth pharyngeal arches give rise to
segments of the aorta and major branching arteries. The third pharyngeal arches become the
common and internal carotid arteries. The right
and left fourth arches develop independently. The
left fourth pharyngeal arch, along with the dorsal
aorta and the aortic sac, forms the arch of the
aorta; the right fourth arch, along with the seventh intersegmental artery, contributes to the formation of the right subclavian artery. The right
and left sixth pharyngeal arch arteries also
develop uniquely; the distal right sixth arch
degenerates completely and the proximal persists
as the proximal right pulmonary artery. The left
sixth arch creates left pulmonary artery and the
ductus arteriosus.
The site of each type of aortic arch interruption may be based in this embryology. IAA type
A may be the result of abnormal regression of the
left fourth aortic arch just beyond the left subclavian artery origin, at the site of its connection
with the dorsal aorta. IAA type B occurs when a
segment of the left fourth aortic arch regresses
abnormally between the origins of the common
carotid arteries. Type C IAA occurs when the left
ventral third and fourth aortic arches regress,
resulting in a proximal interruption, while the
common carotid arteries form from tissue which
would typically regress if the aortic arch had
formed normally.
IAA is often associated with other cardiovascular abnormalities, most often patent ductus
arteriosus which maintains perfusion to the
descending aorta in utero. Only rarely is IAA an
isolated cardiovascular malformation.
4.5.1 Pearls (•) and Pitfalls (#)
• Clinical suspicion of IAA may not occur until
the ductus arteriosus begins to close.
# Severe coarctation of the aorta may present in a similar manner or have complications
similar to those seen in patients with IAA.
4.5.2 Clinical Presentation
A newborn with suspected aortic arch hypoplasia
and coarctation of the aorta on prenatal US
underwent postnatal echo which raised suspicion
of interruption of the aortic arch; cardiac CTA
was requested for further definition of the aortic
arch.
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4.5.3 Case 4.8 Presentation
See Figs. 4.18, 4.19, 4.20, and 4.21.
Fig. 4.18 An in-and-out view of the left side of the heart
shows the left atrium (LA), left ventricle (LV), the left ventricular outflow tract, and the aortic valve (arrow). The ascend-
ing aorta is normal caliber but the aortic arch is interrupted
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Fig. 4.20 A four-chamber view of the heart confirms the
defect in the interatrial septum (arrow)
Fig. 4.19 A sagittal oblique view which includes the ascending (AAo) and descending (DAo) aorta shows the type A
interruption of the aortic arch (bracket), just distal to the left
subclavian artery origin. The patent ductus arteriosus (PDA)
connects the main pulmonary artery (MPA) to the DAo. A
small volume of contrast spills from the left (LA) to the right
atrium (RA), through the patent foramen ovale (arrow)
Fig. 4.21 The findings of a type A interruption are easily
seen on a 3D surface rendered CTA image. The ascending
aorta (AAo) is normal caliber and the three brachiocephalic arteries branch from the proximal aortic arch. The
aortic arch is interrupted distal to the left subclavian artery
(bracket). The main pulmonary artery (MPA) exits the
right ventricle (RV) and continues as the patent ductus
arteriosus (PDA) to supply blood flow to the descending
aorta (DAo)
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4.5.4 Clinical Presentation
A newborn with diagnosis of right ventricle
hypertrophy and a dysplastic pulmonic valve on
prenatal echocardiogram has an additional diagnosis of suspected interruption of the aortic arch
on a postnatal echo. Cardiac CTA was requested
Fig. 4.22 An axial oblique view of the heart shows the
proximal ascending aorta (AAo) and the pulmonic valve
(PV); thickened soft tissue (arrow) of the dysplastic pulmonic valve leaflets is prominent
to further characterize the aortic arch and anatomy of the brachiocephalic artery origins.
4.5.5 Case 4.9 Presentation
See Figs 4.22, 4.23, 4.24, and 4.25.
Fig. 4.24 The four-chamber view confirms right ventricle (RV) hypertrophy (white bracket), secondary to stenosis of the dysplastic and stenotic pulmonic valve. The left
ventricle (LV) is normal volume
Fig. 4.23 An axial oblique view of the superior mediastinal structures shows the ascending (AAo) and descending
(DAo) aorta and the main (MPA), right (RPA) and left
(LPA) pulmonary arteries as well as the patent ductus
arteriosus (PDA) which supplies blood flow to the DAo
distal to the aortic arch interruption
Fig. 4.25 A 3D surface rendered view of the heart shows the
ascending (AAo) and descending (DAo) aorta, and absence of
a connection between the two segments. The type B interruption in the aortic arch is between the left common carotid (L
CCA) and the left subclavian (L Sc) arteries. The patent ductus arteriosus (PDA) provides blood flow to the descending
aorta (DAo) from the main pulmonary artery (MPA) to the
DAo. The origin of the right subclavian artery (R Sc) is aberrant, from the distal aortic arch
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