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Paediatric Cardiothoracic Surgery: Answers
329
Precise vascular anatomy may be demonstrated with echocardiography, CT, or MR
imaging. Arteriography may occasionally be required for clarification or preoperative
demonstration of vascular anatomy.
The most common and serious complete type of vascular ring is the double aortic arch,
which consists of anterior and posterior arches encircling the trachea and oesophagus in a
tight ring, joining distally to form a common descending aorta. The right portion and left
portion of the double arch each gives rise to its own carotid and subclavian arteries. Patients
with this anomaly usually have severe respiratory symptoms and some swallowing difficulty.
The chest radiograph is rarely diagnostic in infants, but in older children bilateral indentation
of the trachea may be visible. Posterior indentation of the trachea may be visible in the lateral
view. Barium swallow is often diagnostic, showing a horizontal defect in the posterior wall of
the oesophagus at the level of the third or fourth thoracic vertebra. This defect is caused by
the posterior arch, usually the larger of the two, as it passes behind the oesophagus. In the
anteroposterior view, the oesophagogram shows bilateral compressions of the oesophagus.
This results in a reverse S-shaped indentation of the oesophagus due to the higher and larger
right aortic arch relative to the lower and smaller left aortic arch.
A right aortic arch with a left ligamentum arising from the descending aorta is another
type of vascular ring, considerably less common than the double aortic arch. The left
ligamentum arteriosum passes from the left pulmonary artery to the descending aorta or to the
left subclavian artery, coursing to the left of the trachea and esophagus. The ring formed by
the aorta, pulmonary artery, and ligament may compress these structures. In this anomaly, the
origin of the left subclavian artery frequently is dilated (Kommerell diverticulum).
Symptoms and plain radiographic findings are identical with those of double aortic arch.
After administration of contrast material, the right aortic arch is identified by the indentation
it makes on the right lateral wall of the oesophagus, and the ligamentum arteriosum is
identified by its impression on the anterolateral wall of the oesophagus. This anomaly may be
well demonstrated at CT or MR imaging, although angiography may be required to
investigate associated intracardiac defects and for planning surgery.
The most common of the aortic arch anomalies, occurring in nearly 1% of the population,
is an aberrant right subclavian artery originating from an otherwise normal left aortic arch.
The anomalous vessel arises from the left side of the aortic arch and crosses the mediastinum
obliquely from left to right behind the oesophagus and trachea on its cephalad course,
producing a characteristic and actually pathognomonic indentation on the oesophagus. In
oesophagograms, this indentation is seen as an oblique filling defect extending from the left
to right. This condition rarely causes symptoms, except for occasional mild dysphagia, so
generally no other radiographic study is needed.
References
Berrocal T, Madrid C, Novo S, et al. Congenital anomalies of the tracheobronchial tree, lung,
and mediastinum: embryology, radiology, and pathology. Radiographics. 2004;24:e17.
Kanne JP, Godwin JD. Right aortic arch and its variants. J Cardiovasc Comput Tomogr.
2010;4:293-300.
4.32 Answer: B
Congenital bronchial atresia is a rare anomaly that results from focal obliteration of a
proximal segmental or subsegmental bronchus that lacks connection with the central airways.
Shahzad G. Raja
330
The development of distal structures is normal. Bronchial atresia most often affects segmental
bronchi at or near their origin; however, lobar or subsegmental bronchi may also be involved.
The bronchi distal to the stenosis become filled with mucus and form a bronchocele. The
alveoli supplied by these bronchi are ventilated by collateral pathways and show features of
air-trapping, resulting in a region of hyperinflation around the dilated bronchi. In some cases,
bronchial atresia may be acquired after birth due to traumatic or postinflammatory insult to
the bronchus. The upper-lobe bronchi are more frequently affected; middle and lower lobes
are rarely affected. The abnormality is an incidental finding in approximately 50% of cases,
mostly in young men, and generally produces no symptoms or signs.
In the newborn period, bronchial atresia is seen as a water-density mass. The mass is
foetal lung liquid trapped behind the atresia. Later in childhood, the foetal lung liquid escapes
and bronchial atresia is found because of focal air trapping. The short atretic segment leads to
accumulation of mucus within the distal bronchi to form a bronchocele, and underventilation
of the affected part of the lung occurs. In adults, bronchial atresia characteristically is seen as
a solitary pulmonary nodule due to a mucus plug and less frequently as congenital lobar
emphysema. Bronchial atresia is usually asymptomatic and is found incidentally in chest
radiographs; however, dyspnoea, pneumonia, and bronchial asthma have been reported. The
characteristic chest radiographic finding consists of a bronchocele, seen as rounded,
branching opacities radiating from the hilum. The bronchocele may contain an air-fluid level.
The distal lung is emphysematous and produces an area of hyperlucency around the affected
bronchi. In newborns, the affected segment may be seen as a fluid-filled mass. CT is a
sensitive modality for demonstrating the typical features of bronchial atresia. It shows a round
opacity at the site of the atresia, medial to the air trapping, which can be clearly depicted by
performing expiratory CT.
References
Williams AJ, Schuster SR. Bronchial atresia associated with a bronchogenic cyst: evidence of
early appearance of atretic segments. Chest. 1985;87:396-398.
Berrocal T, Madrid C, Novo S, et al. Congenital anomalies of the tracheobronchial tree, lung,
and mediastinum: embryology, radiology, and pathology. Radiographics. 2004;24:e17.
4.33 Answer: E
Complement activation occurs through both the alternative (stimulated
by foreign surface
contact, endotoxin, and kallikrein) and classical
(protamine) pathways. The exposure of blood
to extracorporeal
circuits activates the alternative pathway, leading to the formation
of C3a
and C5a, whereas reversal of heparin with protamine activates
the classical pathway with an
associated rise in C4a levels
and further rise in C3a levels. The anaphylatoxins
C3a and C5a
cause activation, degranulation, and adhesion of
neutrophils, and activation of basophils and
mast cells with
histamine release, as well as platelet aggregation.
Kinin peptides are potent vasodilators that also participate
in inflammation, leading to
increased vascular permeability
and neutrophil chemotaxis. The contact activation system
is
composed of kinin–kallikrein, fibrinolytic-coagulation,
and complement systems. During
CPB, factor XII is activated
by contact with artificial surfaces, producing factor XIIa,
which
then converts prekallikrein to kallikrein in the presence
of high-molecular-weight kininogen.
Kallikrein then enters a
positive feedback loop with factor XIIa to activate additional
factor
XII; it also cleaves surface-bound high-molecular-weight
kininogen to produce bradykinin. In
Paediatric Cardiothoracic Surgery: Answers
331
addition to the response
to the CPB circuit, plasma kallikrein levels have been found
to
significantly increase after the administration of heparin. The biologic effects of kinins are
mediated through B
1
and B
2
receptors. B
2
receptors are expressed in many cell types
and have
a high specific affinity for bradykinin. Activation
of B
2
receptors leads to the release of
calcium, nitric oxide,
eicosanoids, free radicals, and cytokines. Bradykinin can
also bind to
receptors on endothelial cells, which then produce
vasoactive prostaglandins and nitric oxide,
leading to vasodilatation
and increased capillary permeability. Bradykinin has also been
found
in the brain parenchyma, with increased levels seen in
the brain interstitial space during
cerebral ischemia.
Mediated by activation of the B
2
receptor, bradykinin can increase
the
permeability of the blood–brain barrier after ischemia–reperfusion,
resulting in plasma
extravasation with edema formation and perturbation
of the cerebral blood flow.
The arachidonic acid cascade is activated by a number of inflammatory
stimuli that result
in activation of cyclooxygenase and phospholipase
A
2
. Arachidonic acid pathway activation
results in production
of thromboxanes, leukotrienes, and prostaglandins. The
neutrophil cell
membrane is the primary source of arachidonic
acid, but the lung is also a major site of the
synthesis, release,
and degradation of the eicosanoids. Thromboxane A
2
, a strong
vasoconstrictor and promoter of platelet aggregation, comes
primarily from platelets and
release occurs to a great extent
in the lungs. Prostaglandin E
1
, prostaglandin E
2
, and
prostacyclin
are also released during CPB. These substances have vasodilating
and platelet
antiaggregant effects that counterbalance the effects
of thromboxane A
2
. Leukotriene B
4
, a
strong chemoattractant
that promotes plasma leakage and leukocyte adhesion, is also
increased during and for a short time after CPB. The magnitude
of eicosanoid production
during CPB is greatest in the very
young.
References
Brix-Christensen V. The systemic inflammatory response after cardiac surgery with
cardiopulmonary bypass in children. Acta Anaesthesiol Scand. 2001;45:671-679.
Kozik DJ, Tweddell JS. Characterizing the inflammatory response to cardiopulmonary bypass
in children. Ann Thorac Surg. 2006;81:S2347-54.
4.34 Answer: B
Congenitally corrected transposition is a rare cardiac condition accounting for
approximately 0.05% of congenital cardiac defects. It has a reported incidence of 1/33,000
live births. This lesion is characterised by the combination of discordant atrioventricular and
ventriculo-arterial connections. Thus, the morphologically right atrium is connected to a
morphologically left ventricle across the mitral valve, with the left ventricle then connected to
the pulmonary trunk. The morphologically left atrium is connected to the morphologically
right ventricle across the tricuspid valve, with the morphologically right ventricle connected
to the aorta. When the atrial chambers are arranged in their usual fashion, the morphologically
left ventricle is usually positioned to the right, and the aorta, arising from the right ventricle,
is left-sided. The malformed heart can also be found with the atrial chambers in mirror-image
arrangement. In this setting, the morphologically left ventricle is left-sided, and the aorta is
typically positioned to the right. Hence, such patients do not have "L-transposition", but do
have congenitally corrected transposition.
Congenitally corrected transposition is also described as "double discordance". As the
name implies, the discordant connections at both the atrioventricular and ventriculo-arterial
Shahzad G. Raja
332
junctions results in normal physiology - hence the congenital correction of the transposition.
Because of the double discordance, the systemic venous return is pumped to the lungs, while
the pulmonary venous return is directed to the body. Symptoms are produced not by the
segmental arrangement of the cardiac components, but by the presence of associated
anomalies. A triad of malformations, made up of an interventricular communication,
obstruction of the outlet from the morphologically left ventricle, and anomalies of the
morphologically tricuspid valve, are sufficiently constant to be considered as part of the
malformation. Abnormalities of atrioventricular conduction are also frequent, but any other
malformation that might co-exist should be anticipated to be present at some time or in some
place.
The aetiology of congenitally corrected transposition is not currently known. Based on
geographic incidence, studies have suggested an association with environmental factors, such
as hair dye and air pollutants. Recently studies have shown an increase in incidence among
families with previous cases of congenitally corrected transposition, with a recurrence risk in
siblings of between 2.6% to 5.2%.
Symptomatology, if present in the newborn, infant, and child, is related to the associated
malformations. If there are no associated defects, which is uncommon, the patient will
typically be asymptomatic early in life. Cyanosis will be present if there is pulmonary
stenosis and a ventricular septal defect, while heart failure will develop earlier in life if there
is a haemodynamically significant ventricular septal defect, evidenced in children by easy
fatigability, poor weight gain, feeding intolerance, and so on.
References
Wallis GA, Debich-Spicer D, Anderson RH. Congenitally corrected transposition. Orphanet J
Rare Dis. 2011;6:22.
Dyer K, Graham TP. Congenitally corrected transposition of the great arteries: current
treatment options. Curr Treat Options Cardiovasc Med. 2003;5:399-407.
4.35 Answer: C
Complete atrioventricular canal (CAVC), also referred to as complete atrioventricular
septal defect, accounts for about 3% of all cardiac malformations. Atrioventricular canal has
an incidence of 2/10,000 live births. Both sexes are equally affected, with a slightly higher
frequency in female (female/male ratio 1.3/1). CAVC has a strong association with Down
syndrome.
The complete form of AVC shows an ostium primum atrial septal defect, a common
atrioventricular valve and a variable deficiency of the interventricular septum inlet. This
anatomic arrangement gives a scooped out appearance to the ventricular inlet and a long and
narrow morphology to the left ventricular outlet. The key finding for the anatomic
classification in type A, B or C of this malformation is the morphology of the common
atrioventricular valve. It is basically built-up of five leaflets (superior, inferior, mural in the
right and left ventricle and antero-superior), embryologically derived from the original
endocardial cushions. The size of the antero-superior leaflet is reciprocal with the extent of
bridging of the superior leaflet. In type A, the superior bridging leaflet is almost completely
adherent to the left ventricle and is firmly attached on the ventricular septum by multiple
chordal insertions. In type B, the superior bridging leaflet is larger and overhangs the
ventricular septum more than in type A, attached over it by an anomalous papillary muscle of
Paediatric Cardiothoracic Surgery: Answers
333
the right ventricle. In type C, the superior bridging leaflet is larger and is not attached to the
ventricular septum (free-floating leaflet), thus provoking an unrestricted interventricular
communication. Type A CAVC is most frequently associated with left-sided obstructions.
Type B is the least common form of atrioventricular canal. Type C is often associated with
other complex cardiac malformations such as tetralogy of Fallot. Other cardiac malformations
are the left ventricular inflow and outflow obstructions, mainly due to anomaly of the left
component of the common atrioventricular valve, and to ventricular imbalance, with right
ventricular dominance. These additional left-sided anomalies are more frequent in children
without Down syndrome.
Surgical management of paediatric patients with the diagnosis of CAVC is accomplished
by using one of three procedures: (1) the classic single-patch, (2) two-patch, or (3) modified
single-patch technique. Of these, the modified single-patch is currently the best technique
available for repair of CAVC.
References
Calabrò R, Limongelli G. Complete atrioventricular canal. Orphanet J Rare Dis. 2006;1:8.
Backer CL, Stewart RD, Mavroudis C. What is the best technique for repair of complete
atrioventricular canal? Semin Thorac Cardiovasc Surg. 2007;19:249-57.
Acknowledgment
Source: American Heart Association, Inc.
Circulation 2008;118:e523-e661.
Index
(The number in bold indicates section and the number in italics indicates question number)
#
18
F-FDG PET scan 3.3, 3.4
22q11 deletion syndrome 4.22
A
Action potential, cardiac myocyte 1.21
Acute haemorrhage, compensatory changes 1.54
Acute ischemic mitral regurgitation,
pathophysiology 2.46
Acute respiratory distress syndrome 1.40
Adenoid cystic carcinoma, trachea 3.19, 3.27
Adrenal mass 3.40
Allograft coronary artery disease 1.26
Alpha-1-antitrypsin deficiency 1.36
Alveolar ventilation & alveolar CO
2
pressure 1.68
Amiodarone 1.14
Anatomic dead space 1.64
Angiotensin II 1.57
Aortic dissection 2.64
Aortic regurgitation, acute 2.21
Aortic regurgitation, aortic valve replacement 2.24,
2.27
Aortic regurgitation, chronic 2.22
Aortic regurgitation, severe 2.25
Aortic regurgitation, vasodilator therapy 2.23
Aortic stenosis, aortic valve replacement 2.19
Aortic stenosis, severe 2.18
Aortic valve endocarditis, predisposing lesions 2.38
Aortic valve replacement 2.28
Aortic valve surgery 2.20
Aortic valve, selection 2.16
Aortopulmonary window 4.29
Aprotinin 1.18
Asbestosis 1.38
Atrial septal defect 1.80
Autonomic ganglionic tumors 3.94
Azathioprine 2.55
B
Baroreceptor reflex 1.56
BART trial 2.5
Bicuspid aortic valve 4.1
Bicuspid aortic valve & dilated ascending aorta
2.26
Blood supply, trachea 3.21
Breathing 100% O
2
, effects 1.69
Bronchial carcionoid 3.29, 1.50
Bronchial mucoepidermoid carcinoma 3.25, 3.26
Bronchoalveolar carcinoma 1.41
Bronchogenic cyst 3.89
Bronchogenic cyst 4.14
Broncholithiasis 3.65
Bronchoplastic procedures 3.54
Bronchovascular fistula 3.55
C
Cancer screening 3.1
Carbohydrate metabolism, heart 1.4
Carcinoid tumors, lung 3.28
Cardiac allograft rejection 2.58
Cardiac allograft vasculopathy 2.59
Cardiac angiosarcoma 2.7
Cardiac lipoma 2.13
Cardiac murmurs 2.17
Cardiac myxoma 2.8, 2.9, 2.10, 2.11, 2.12
Index
338
Cardiac output, calculation 1.58
Cardiac retransplantation 2.60
Cardiac transplantation, donor-recipient matching
2.50
Cardiac transplantation, predictors of survival 2.49
Cardiogenesis 4.28
Cardiopulmonary bypass, inflammation 4.33
Carinal sleeve resection 3.56
Cerebral metabolic rate 1.19
Cervical mediastinoscopy, complications 3.8
Chest computed tomography 3.75
Chest x-ray screening trials 3.2
Chronic fibrosing mediastinal inflammation 3.95
Chylothorax 1.46
Clopidogrel 2.2
Clopidogrel, trials 2.3
Complete atrioventricular canal 4.35
Congenital bronchial atresia 4.32
Congenital diaphragmatic hernia 4.19
Congenital lobar emphysema 4.13
Congenital tracheal stenosis 4.30
Congenital tracheomalacia 4.17
Congenitally corrected transposition 4.34
Coronary artery bypass grafting vs percutaneous
coronary intervention 2.42
Coronary blood flow 1.23
CORONARY trial 2.65
Costodiaphragmatic recess 1.75, 1.83, 1.91, 1.98
Costomediastinal recess 1.92, 1.100
Cupola 1.87, 1.94
Cyclooxygenase-2 3.47
Cyclosporine 2.52, 2.53
Cystic fibrosis 4.9, 4.10, 1.32
Cytokines 1.17
D
Desmopressin 2.4
Development of lung 4.11
Diaphragmatic trauma 3.9
Disseminated intravascular coagulation 1.24
Dobutamine 1.6
Dopamine 1.2
E
Early prosthetic valve endocarditis, microorganisms
2.39
Ebstein’s anomaly 4.21
Echocardiography 1.29
Ectopic ACTH production, 1.43
Eisenmenger's syndrome 1.31
Endothoracic fascia 1.97
Enterogenous cysts 3.90
Esophageal atresia 4.8
Esophageal perforation/rupture 3.14, 3.15
Esophagectomy, atrial arrhythmias after 3.97
Esophagectomy, chylothorax after 3.99
Esophagectomy, pulmonary complications after
3.100
Esophagectomy, recurrent laryngeal nerve injury
after 3.98
Esophagectomy, transthoracic vs transhiatal 3.101
Extracorporeal membrane oxygenation 4.24
Extralobar pulmonary sequestration 4.12
F
Forest plot 1.1
Funnel plot 1.10
H
Haemorrhage, pulmonary vascular changes 1.53
Haemorrhagic shock 1.55
Heparin 2.48, 1.15
Heparin-induced thrombocytopenia 2.1
Hodgkin lymphoma, primary mediastinal 3.88
Hypovolemic shock 1.52
I
Infective endocarditis 2.37
Infective endocarditis, causative agents 1.27
Infective endocarditis, Duke criteria 2.35
Infective endocarditis, prophylaxis 2.36
Inhaled nitric oxide 1.11
Inspiratory reserve volume, calculation 1.71
Interatrial septal defects 4.26
International Registry of Lung Metastases 3.61
Ischemic mitral regurgitation 2.45
K
Kawasaki disease 4.25
L
Left recurrent laryngeal nerve 1.95
Left vagus nerve 1.88
Left ventricular pseudoaneurysm 2.47
Levosimendan 1.9