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Paediatric Cardiothoracic Surgery: Answers
319
4.20 Answer: D
A mechanical prosthesis has been the prosthesis of choice for mitral valve replacement
(MVR) in children because durability of allograft and xenograft prostheses in children is
poor. Mitral valve replacement in small children is difficult when compared with MVR in
older children and adults, both initially and at the time of reoperation. Re-replacement is
inevitable when small children undergo MVR because of patient somatic growth.
Cage-ball mechanical prostheses were used exclusively in the 1960s and early 1970s. The
bioprosthetic valves were introduced in the early to middle 1970s and were initially
considered better suited for children because of their lower profile when compared with
caged-ball prostheses. The durability of xenograft valves in children was and continues to be
short (limited). The new or mechanical prosthesis, while undergoing rare structural
degeneration, are susceptible to other complications including hemolysis, infection, and
thromboembolism. The use of anticoagulation in children presents its own risks and
problems. The difficulties presented by prosthetic and bioprosthetic valves in pediatric
patients have motivated a few institutions to consider human valve substitutes. One approach
to MVR makes use of the pulmonary valve autograft (Ross II). The free-hand mitral valve
homograft in children has not been durable.
The incidence of heart block ranges between 8% and 30% in several recent reports.
Insertion of a large prosthesis into a relatively small mitral annulus most likely contributes to
the majority of conduction blocks. Insertion of the prosthesis into a supraannular position
may obviate heart block, acquired subaortic stenosis, or circumflex coronary compression.
The incidence of prosthetic valve thrombosis, thromboemboli, and anticoagulation-related
bleeding necessitating transfusion ranges between 20% to 40%.
References
Sim HT, Lee SC, Shin HJ, Park JJ, et al. Mitral valve replacement using mechanical
prostheses in children: early and long-term outcomes. Pediatr Cardiol. 2012;33:639-45.
Brown JW, Fiore AC, Ruzmetov M, et al. Evolution of mitral valve replacement in children:
a 40-year experience. Ann Thorac Surg. 2012;93:626-33.
Alsoufi B, Manlhiot C, McCrindle BW, et al. Results after mitral valve replacement with
mechanical prostheses in young children. J Thorac Cardiovasc Surg. 2010;139:1189-96.
4.21 Answer: C
Ebstein‘s anomaly is a malformation of the tricuspid valve and right ventricle
characterized by (1) adherence of the septal and posterior leaflets to the underlying
myocardium (failure of delamination, namely splitting of the tissue by detachment of the
inner layer during embryologic development); (2) downward (apical) displacement of the
functional annulus (septal>posterior>anterior); (3) dilation of the ―atrialized‖ portion of the
right ventricle, with various degrees of hypertrophy and thinning of the wall; (4) redundancy,
fenestrations, and tethering of the anterior leaflet; and (5) dilation of the right atrioventricular
junction (true tricuspid annulus).
References
Edwards WD. Embryology and pathologic features of Ebstein‘s anomaly. Prog Pediatr
Cardiol. 1993;2:5-15.
Shahzad G. Raja
320
Attenhofer Jost CH, Connolly HM, Dearani JA, Edwards WD, Danielson GK. Ebstein's
anomaly. Circulation. 2007;115:277-85.
4.22 Answer: D
A microdeletion of chromosome 22q11.2 is found in most patients with velocardiofacial
syndrome, DiGeorge syndrome, and conotruncal anomaly face syndrome, and in some
patients with Cayler cardiofacial and autosomal dominant Opitz-G/BBB syndromes. A wide
spectrum of clinical findings accompanies the 22q11.2 deletion, without genotype or
phenotype correlation even among affected family members. Dysmorphic facies, conotruncal
cardiac defects, hypocalcaemic hypoparathyroidism, T-cell mediated immune deficiency, and
palate abnormalities are classic features. Less well recognized are learning, speech, feeding,
and psychiatric disorders, and renal and musculoskeletal defects. Parathyroid and immune
deficiencies in the same individual can progress or resolve with time. The structures primarily
affected in patients with 22q11DS are derivatives of the embryonic pharyngeal arches and
pouches. The 22q11.2 deletion can be inherited as an autosomal dominant or arise as a de
novo deletion or translocation. Fluorescent in situ hybridization using cosmid probes mapping
to the DiGeorge chromosomal region is a widely available method to detect the 22q11.2
deletion in metaphase chromosomes from cultured lymphocytes, amniocytes, or chorionic
villi. The ubiquitin-fusion-degradation-1-like gene, expressed in embryonic branchial arches
and in the conotruncus, appears to play a prominent role in the pathogenesis of the 22q11.2
deletion syndrome.
References
Cuneo BF. 22q11.2 deletion syndrome: DiGeorge, velocardiofacial, and conotruncal anomaly
face syndromes. Curr Opin Pediatr. 2001;13:465-72.
Perez E, Sullivan KE. Chromosome 22q11.2 deletion syndrome (DiGeorge and
velocardiofacial syndromes). Curr Opin Pediatr. 2002;14:678-83.
4.23 Answer: B
The hypercyanotic spell is characterised by a sudden and striking decrease in the
saturation of oxygen due to acute and complete, or near complete, obstruction of the
subpulmonary outflow tract. Not all patients with tetralogy of Fallot will have hypercyanotic
spells. The spells typically begin to occur at approximately a couple months of age at times of
agitation or decreased hydration, both of which exacerbate the dynamic infundibular
obstruction. The murmur produced by the muscular obstruction is absent during a true spell,
due to nearly absent antegrade flow across the right ventricular outflow tract. Patients become
severely cyanotic, hyperpnoeic, and lethargic. With the development of metabolic acidosis,
there is an increase in pulmonary vascular resistance, with a decrease in systemic vascular
resistance. Cardiac output becomes compromised due to myocardial ischaemia. Impending
collapse and death can ensue.
Overcoming a hypercyanotic spell requires maneuvers to re-establish adequate balance
between the systemic and pulmonary flows. Treatment must focus on decreasing pulmonary,
and increasing systemic, vascular resistance, hence promoting left to right flow across the
ventricular septal defect and into the subpulmonary outlet.
Parents at home with a child suffering such spells are taught to place their child in the
knee-to-chest position in an effort to increase systemic vascular resistance and promote
Paediatric Cardiothoracic Surgery: Answers
321
systemic venous return to the right heart. This will theoretically increase intracardiac shunting
from left-to-right across the interventricular communication, as well as increase the preload of
the right ventricle. Emergency services should be contacted immediately.
Medical management will consist of establishing immediate intravenous access to allow
prompt administration of fluids, which will improve right ventricular preload. Oxygen should
be initiated to decrease peripheral pulmonary vasoconstriction, and improve oxygenation
once flow of blood to the lungs is re-established. Subcutaneous morphine should be
administered to decrease the release of catecholamines. This will increase the period of right
ventricular filling by decreasing the heart rate, and promote relaxation of the infundibular
spasm. If the patient remains hypercyanotic after these measures, he or she should be
paralysed and intubated, with phenylephrine administered intravenously to increase systemic
vascular resistance.
The long half-life, and potential side effects, such as hypotension and cardiac
dysfunction, of beta blockers precludes their routine use in the emergency situation.
Propranolol has been used in small doses in the chronic care of patients deemed to be at risk
for spells in an effort to minimise the infundibular spasm responsible for the episodes. Once a
patient requires prophylaxis by beta-blockade, surgical referral should occur to prevent the
potential tragic and unpredictable outcome of a hypercyanotic spell.
References
Bailliard F, Anderson RH. Tetralogy of Fallot. Orphanet J Rare Dis. 2009;4:2.
Roekens CN, Zuckerber AL. Emergency management of hypercyanotic crises in tetralogy of
Fallot. Annals of Emergency Medicine. 1995;25:256-258.
4.24 Answer: C
Extracorporeal membrane oxygenation (ECMO) support is only useful in cases where the
primary lung injury is accompanied by the absence of oxygen toxicity and barotrauma caused
by mechanical ventilatory support, or the primary underlying cardiac insult is reversible. The
fundamental problem accompanying the treatment modality which relies on the injured lung
to maintain gas exchange is that the modality becomes gradually ineffective as the lung
disease becomes more severe. The mortality increases from 33% with moderate lung injury to
more than 82% with severe injury, secondary to continued barotrauma, volutrauma and
oxygen toxicity, all combining to produce ventilator-induced lung injury. Criteria often cited
for qualifying a patient for ECMO treatment are with pretreatment predicted mortality
threshold reaching above 80-90%, shown by fulfilment of any of the criteria shown below.
More frequently, indices to assess refractory hypoxemia are used. The arterial oxygen to
alveolar oxygen ratio (a:A ratio ≤ 0.15 at 12-72 hours) or alveolar-arterial oxygen tension
gradient (A-a gradient > 450 for over 24 hours) can be used, but the oxygenation index (OI) is
currently more commonly used. Mortality predictors are unfortunately derived by looking at
retrospective data and tend to undermine the prediction of prospective results. However, due
to the high technical demands, cost, and risk of complications (such as bleeding under
anticoagulant medication), ECMO is usually only considered as a last resort therapy. It is
imperative from the present evidence that the patient should be considered for the benefits
from ECMO before the terminal ventilator lung injury, which occurs in 7-9 days depending
on the patient's age, coupled with the failure of conventional treatment.
Shahzad G. Raja
322
Extracorporeal membrane oxygenation indication indices for >80% predicted mortality
Oxygenation Index (OI) > 40 or > 35 for 4 hours
OI = (MAP x FiO
2
x 100) / PaO
2
Ventilation Index (VI) > 90 for 4 hours
VI = RR x PIP – PEEP/1000
Alveolar – arterial oxygen difference [(A-a)DO
2
] > 600 – 624 mmHg (at sea level)
despite
4–12 hours of medical management
(A-a)DO
2
= [atmospheric pressure - 47] – (PaCO
2
– PaO
2
) / FiO
2
47 being vapour pressure at sea level
PaO
2
< 50 mmHg for 2-12 hours (FiO
2
of 100%)
Acute deterioration PaO
2
< 30 - 40 mmHg (FiO
2
of 100%)
pH < 7.25 for 2 hours
Intractable hypotension
Physiological goals of ECMO are: (1) Remove CO
2
and oxygenate the blood; (2)
Improve tissue oxygen delivery; (3) Allow normal physiologic metabolic milieu at tissue
level; and (4) Provide lung rest and/or cardiac offloading.
Systolic and diastolic pressures decrease with decrease in aortic pulse pressure. Preload
and afterload parameters are the most affected. Peak and mean blood flow velocities decrease
by 30-50% after ECMO. They return to normal after 72 hours of ECMO run, concurrent with
the reduction in pump flows. Blood pressure abnormalities occur frequently following the
initiation of ECMO. Systemic hypertension is more frequent than hypotension. Initial
management on ECMO requires the weaning of inotropes with aggressive treatment for
hypertension, as there is a risk of intracranial hypertension and bleed (especially in neonates).
Hypotension is less frequent, but is secondary to decrease in systemic vascular resistance and
the most common cause is hypocalcemia. Arrhythmias are commonly encountered during
cannulation for ECMO, particularly bradyarrythmias secondary to vagal stimulation, hypoxia
or acidosis. Other arrhythmias include atrial and ventricular ectopics from mechanical
irritation. Atrial fibrillation and supraventricular tachycardia are less common but are usually
responsive to cannulae repositioning. Electrolyte abnormalities of calcium and potassium can
occur during the first hour of ECMO support and can contribute to rhythm abnormalities.
Cardiac Stun, complete or near-complete absence of ventricular contractions in response to
ECMO support (predominantly seen in VA ECMO), may spontaneously resolve, but carries a
high mortality. Seen as pulse pressure becoming <5 mmHg with a marked increase in PaO
2
which almost equals membrane lung PaO
2
and is hypothesized as reperfusion injury or
mismatch of preload or afterload or contractility. This can also result from incorrect
positioning of cannulae. In such scenarios, cannulae repositioning usually solves the issue.
Paediatric Cardiothoracic Surgery: Answers
323
References
Chauhan S, Subin S. Extracorporeal membrane oxygenation, an anesthesiologist's
perspective: physiology and principles. Part 1. Ann Card Anaesth. 2011;14:218-29.
Alpard SK, Zwischenberger JB. Extracorporeal membrane oxygenation for severe respiratory
failure. Chest Surg Clin N Am. 2002;12:355-78.
Wolfson PJ. The development and use of extracorporeal membrane oxygenation in neonates.
Ann Thorac Surg. 2003;76:S2224-9.
4.25 Answer: A
Kawasaki Disease is a vasculitis of young childhood that particularly affects the coronary
arteries. Molecular analysis of the oligoclonal IgA response in acute KD led to production of
synthetic KD antibodies. These antibodies identify intracytoplasmic inclusion bodies in acute
KD tissues. Light and electron microscopic studies indicate that the inclusion bodies are
consistent with aggregates of viral proteins and RNA. Advances in molecular genetic analysis
and completion of the human genome project have sparked a worldwide effort to identify
genes associated with KD. A polymorphism of one such gene, ITPKC, a negative regulator of
T cell activation, confers susceptibility to KD in Japanese populations and increases the risk
of developing coronary artery abnormalities in both Japanese and U.S children.
Without treatment, approximately 25% of children with KD develop coronary artery
abnormalities. Therapy with intravenous gammaglobulin and aspirin within the first ten days
of fever onset reduces the prevalence of coronary artery abnormalities from about 25% in
untreated patients to about 5%. KD is unusual among serious vasculitis disorders in that
steroids are not indicated for primary therapy. The leading theory of KD causation is that a
ubiquitous infectious causative agent that usually results in asymptomatic infection causes
KD in a small subset of genetically predisposed children.
Although the immune response to KD likely plays a role in the pathology, as it does in
most infectious diseases, a primary autoimmune aetiology seems unlikely given the self-
limited febrile phase of illness, the generally non-recurring nature of KD and the lack of
indication for corticosteroids in primary therapy of KD. Despite being detected in serum of
KD patients 2–3 weeks after fever onset, immune complexes do not appear to play a role in
the development of coronary artery disease as immune complex deposits are not observed in
inflamed KD arterial tissue.
References
Rowley AH. Kawasaki disease: novel insights into etiology and genetic susceptibility. Annu
Rev Med. 2011;62:69-77.
Gerding R. Kawasaki disease: a review. J Pediatr Health Care. 2011;25:379-87.
Kuo HC, Yang KD, Chang WC, et al. Kawasaki disease: an update on diagnosis and
treatment. Pediatr Neonatol. 2012;53:4-11.
4.26 Answer: D
Atrial septal defects (ASDs) can be classified as morphologic defects of the interatrial
septum that produce a direct communication between the right and left atria (ostium primum
ASD, endocardial cushion defects, ostium secundum ASD) and as defects that do not involve
the interatrial septum but physiologically behave like interatrial septal defects (sinus venosus
ASD, unroofed coronary sinus).
Shahzad G. Raja
324
Ostium primum ASDs are regarded as the mildest form in the spectrum of endocardial
cushion defects. They represent 2–3% of the ASDs. They are commonly associated with
Down syndrome. The endocardial cushions form the medial aspects of the mitral and
tricuspid valves, the portion of the atrial septum adjacent to the atrioventricular valves, and
the inlet portion of the ventricular septum during embryologic development,. When the defect
is isolated because of the failure of fusion between the free edge of the septum primum and
the endocardial cushion, it is termed ―ostium primum ASD.‖ If this defect is associated with
abnormal development of the atrioventricular valves or ventricular septum, it is known as
endocardial cushion defects.
Ostium secundum ASDs represent 80– 90% of ASDs. Ostium secundum ASDs are a
direct communication between the two atria, whereas a PFO defect is a tunnel of variable
width and length between the two atria. The patent foramen ovale (PFO) flow is usually left
to right but can be bidirectional. Under normal physiologic conditions, the left atrial pressure
is slightly higher than the right atrial pressure, pushing the flap valve against the septum
secundum narrowing the PFO tunnel. Conditions that increase right atrial pressures such as
coughing, the Valsalva manoeuvre, or pathologic conditions (e.g., severe tricuspid or
pulmonary regurgitation) can cause the flap valve to open, thereby allowing right-to-left
shunting.
Sinus venosus defects represent approximately 2–10% of all ASDs. Although the exact
embryology of sinus venosus defects is controversial, they are thought to result from the lack
of septation between the pulmonary veins and the superior vena cava (SVC) or right atrium.
There are two types of sinus venosus defects: the superior and inferior sinus venosus
ASDs. The superior sinus venosus ASD is a defect connecting the right atrium–SVC junction
with the left atrium. It is commonly associated with partial anomalous pulmonary venous
return (PAPVR) of the right upper lobe into the SVC. The inferior sinus venosus ASD
connects the right atrium–inferior vena cava (IVC) junction with the left atrium. It can be
associated with PAPVR of the right lower lobe pulmonary vein into the intrapericardial
segment of the IVC or right atrium.
Unroofed coronary sinus is a rare type of ASD. It develops due to a lack of septation
between the inferior left atrium and the roof of the coronary sinus, allowing communication
between the left and right atria. ASDs are the most common congenital heart defect to present
in adulthood. ASDs, which are often clinically silent for years to decades, produce a left-to-
right shunt. Longstanding left-to-right shunting from ASDs leads to dilatation of the right-
sided chamber and enlargement of the pulmonary arteries. The left atrium is not dilated unless
the ASD is accompanied by another anomaly. Eisenmenger physiology may result over time
because of chronic overload of the right-sided chambers that produces permanent pulmonary
hypertension and right-to-left shunting through the ASD. A pulmonary-to-systemic blood
flow ratio (Qp:Qs ratio) of greater than 1.5:1 will cause a patient to be symptomatic with the
development of arrhythmias, fatigue, dyspnoea, or heart failure.
References
Rojas CA, El-Sherief A, Medina HM, et al. Embryology and developmental defects of the
interatrial septum. AJR Am J Roentgenol. 2010;195:1100-4.
Blom NA, Ottenkamp J, Jongeneel TH, et al. Morphogenetic differences of secundum atrial
septal defects. Morphogenetic differences of secundum atrial septal defects. Pediatr
Cardiol. 2005;26:338-43.
Paediatric Cardiothoracic Surgery: Answers
325
4.27 Answer: A
The hearts with atrioventricular concordance and ventriculoarterial discordance represent
5–7% of all congenital heart defects. This corresponds to an incidence of 20 to 30 per 100 000
live births. There is a male predominance with a male/female sex ratio that varies from 1.5:1
to 3.2:1 as reported in literature. This cardiac defect is associated with other noncardiac
malformations in 10% of the cases.
Ventricular septal defects of variable location and size are particularly common. They
may be associated with a certain degree of malalignement between the outlet and trabecular
septum. Concomitant pulmonary overriding and subaortic stenosis can be expected when
anterior and rightward deviation of the outlet septum is present. In these cases, hypoplasia,
coarctation, or even interruption of the aortic arch may be present. On the other hand,
posterior and leftward deviation of the outlet septum may lead to subpulmonary stenosis.
Left ventricular outflow tract obstruction is present in one-eighth to one-third of cases. It
is far more common in the presence of a ventricular septal defect than when the ventricular
septum is intact. This obstruction to the flow of blood can be caused by a wide spectrum of
lesions, either at valvar or subvalvar level, and deviation of the muscular outlet septum is but
one of them. Bulging of the septum, a fibrous shelf or fibromuscular tunnel, tissue tags, and
abnormal attachment of the atrioventricular valvar tension apparatus can also be substrates for
stenosis.
The systemic and pulmonary circulations run in parallel, rather than in series in the
presence of concordant atrioventricular and discordant ventriculoarterial connections,. As
such oxygenated blood flows through a closed circuit that involves the lungs and the left
cardiac chambers. On the other hand, systemic blood flow is supplied by another closed
circuit that begins and ends in the right cardiac chambers. In this setting, survival is only
possible, if there is adequate mixing between the two circulations, be it between the septums
or through the arterial duct.
Intravenous prostaglandin E1 infusion is used to maintain arterial duct patency leading to
an increase in pulmonary blood flow, which increments pulmonary venous return and left
atrial pressure, thus encouraging left to right flow at atrial level. Early and late side effects
may be observed, namely apnoeas, bradycardia, systemic hypotension, fluid-electrolyte
disturbances, fever and cutaneous flushing. Long-term use is associated with cortical
hyperostosis, an effect that does not seem to be dose-related. Monitoring in an intensive care
unit is therefore advised.
References
Martins P, Castela E. Transposition of the great arteries. Orphanet J Rare Dis. 2008;3:27.
Raja SG, Kostolny M, Oswal N, et al. Midterm follow-up of arterial switch operation for
transposition of the great arteries with intact ventricular septum and left-ventricular
outflow tract obstruction. Eur J Cardiothorac Surg. 2011;40:994-9.
Raja SG, Shauq A, Kaarne M. Outcomes after arterial switch operation for simple
transposition. Asian Cardiovasc Thorac Ann. 2005;13:190-8.
4.28 Answer: B
The cardiovascular system is the first organ system to develop and function in the
vertebrate embryo. The heart forms as a linear tube when regions of bilaterally symmetrical
cardiac progenitor cells in the anterior lateral mesoderm fuse at the ventral midline. This tube
Shahzad G. Raja
326
is continuous with the dorsal aorta anteriorly and the cardinal veins posteriorly. The heart
tube at the time of its formation is a bi-layered structure, consisting of an inner endothelial
layer and an outer myocardial layer. The myocardial layer will form the muscular walls of the
heart and the muscular portions of the interventricular septum. The endothelial layer
constitutes the endocardium.
In addition to forming an endothelial layer within the heart that is contiguous with the
rest of the vasculature, the endocardium has several other essential functions during heart
development. For instance, the endocardium plays an important role in signaling to
cardiomyocytes and is required for proper formation of trabecular myocardium. It is also
involved in the signaling required for transdifferentiation of myocytes into the Purkinje fiber
cells that comprise much of the cardiac conduction system. In addition, cells from specific
regions of the endocardium will undergo endocardial-to-mesenchymal transformation to form
the endocardial cushions. The endocardial cushions give rise to several important structures
within the heart, including the valve leaflets, the membranous portion of the interventricular
septum, and the atrial septum. Furthermore, endothelial-derived cells in the cardiac cushions
function, along with cells of neural crest origin, to separate the common outflow tract into the
pulmonary artery and aorta.
Vasculogenesis, the de novo formation of blood vessels, occurs necessarily before the
onset of blood circulation. In amniotes, endothelial and hematopoietic cells first appear at the
same time in the extraembryonic yolk sac and are thought to arise from a common
mesodermal precursor, the hemangioblast. Vasculogenesis begins when hemangioblasts
coalesce to form blood islands. The outer cells in the blood islands flatten as they differentiate
into endothelial cells, while the inner cells differentiate into hematopoietic progenitors.
Ultimately, these cells will form the extraembryonic yolk sac vasculature and the blood cells
contained within it.
De novo vasculogenesis also occurs at multiple discrete sites within the embryo proper,
including the paired dorsal aortae, within the heart tube, in the neural plexus, and in the
primary vascular plexus. In the embryo, mesoderm-derived endothelial precursors called
angioblasts aggregate to form the dorsal and ventral aortae and the vitelline vessels.
Endocardial precursors arise via a similar process of de novo vasculogenesis within the
cardiac crescent and are subsequently arranged into a vascular tube during ventral
morphogenesis. The precise timing of specification of these precursors remains incompletely
understood.
References
Harris IS, Black BL. Development of the endocardium. Pediatr Cardiol. 2010;31:391-9.
Milgrom-Hoffman M, Harrelson Z, et al. The heart endocardium is derived from vascular
endothelial progenitors. Development. 2011;138:4777-87.
4.29 Answer: E
The aortopulmonary window (APW) is a congenital defect characterized by a
communication between the ascending aorta and the pulmonary artery in the presence of
separate semilunar valves. It is a rare malformation accounting for 0.15 to 0.60% of the
congenital heart diseases. It is associated with other cardiac defects in ¼ to ½ of the cases.
The clinical impact depends on the size of the window and the presence of associated defects
Paediatric Cardiothoracic Surgery: Answers
327
and the development of pulmonary arterial hypertension. The most accepted classification is
that by Richardson:
Type I: the defect is located between the origin of the main pulmonary artery and the
ascending aorta immediately above the sinus of Valsalva (embryologically, it is due
to the deficient septation of the aortopulmonary trunk);
Type II: it is more distal, between the ascending aorta and the origin of the right
pulmonary artery (it is due to the abnormal migration of the sixth aortic arch);
Type III: consists in the anomalous origin of the right pulmonary artery of the aorta
(results from the uneven septation of the truncus arteriosus).
APW presents a physiology of left-right shunt. When APW is isolated and large-sized,
the clinical presentation is due to the increased pulmonary flow characterised by congestive
heart failure, pulmonary hypertension and early development of pulmonary obstructive
vascular disease. Smaller defects may not present a clinical manifestation and go undetected
at image assessments. When other defects are associated, the clinical findings are variable and
this can result in atypical clinical presentations, which are more related to the associated
defect.
The prognosis depends, in a large number of cases, on the presence of other associated
congenital heart defects. An incidence of 47 to 77% of other associated cardiac defects is
reported in the published literature. Interruption of the aortic arch (15 to 20%) is the most
common associated defect. Other defects are the anomalous origin of the coronary artery,
right-sided aortic arch, ventricular septal defect, bicuspid aortic valve, tetralogy of Fallot with
or without agenesis of the pulmonary valve, discordant ventricle-arterial connection, double
aortic arch and tricuspid atresia.
The image diagnosis (Doppler echocardiogram with color flow and magnetic
angioresonance) allows the exact assessment of the defect location and size. Occasionally it
may be difficult to differentiate the defect from the common truncus arteriosus, the
anomalous origin of the pulmonary aortic artery (which, according to Richardson,
corresponds to the type III of the APW) and even the short-extension arterial canal. In these
cases, the cardiac catheterisation becomes important in the differential diagnosis as it also
provides additional information on arterial pressure and pulmonary vascular resistance.
The surgical repair involves closure of the APW window using a patch, normally of
bovine pericardium. Since the first repair carried out by Gross in 1952, through a
thoracotomy, several techniques have been described, using the transaortic or the
transpulmonary approaches.
References
Barnes ME, Mitchell ME, Tweddell JS. Aortopulmonary window. Semin Thorac Cardiovasc
Surg Pediatr Card Surg Annu. 2011;14:67-74.
Konstantinov IE, Karamlou T, Williams WG, et al; Congenital Heart Surgeons Society.
Surgical management of aortopulmonary window associated with interrupted aortic arch:
a Congenital Heart Surgeons Society study. J Thorac Cardiovasc Surg. 2006;131:1136-
1141.e2.
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328
Bagtharia R, Trivedi KR, Burkhart HM. Outcomes for patients with an aortopulmonary
window, and the impact of associated cardiovascular lesions. Cardiol Young. 2004; 14:
473-80.
4.30 Answer: C
Congenital tracheal stenosis is a rare disorder characterized by the presence of focal or
diffuse complete tracheal cartilage rings, resulting in a fixed tracheal narrowing. The entity
may be seen in isolation or in association with other anomalies. The most common associated
anomaly is the pulmonary artery sling complex. Pulmonary artery sling is a rare congenital
anomaly in which the left pulmonary artery originates from the right pulmonary artery and
encircles the right mainstem bronchus and distal trachea, causing compression of each. One
must be aware of this anomaly when examining an infant with apparent segmental distal
tracheal stenosis. A variety of congenital stenosis patterns have been described, along with a
variety of different surgical approaches. Approximately 50% of congenital tracheal stenoses
are focal, 30% generalized, and 20% funnel-shaped. Focal congenital tracheal stenosis
consists of a simple local narrowing of the trachea, usually in the lower third. The distal end
of the trachea and bronchi are of normal size. Symptoms are variable, depending on the age of
the child, the degree of stenosis, and the potential presence of associated anomalies. Infants in
whom this disorder is discovered early in life tend to have a worse prognosis. Ninety percent
of children present during the 1st year of life, often with biphasic stridor. Length of stenosis
does not appear to be as critical as degree of stenosis in producing symptoms, as airway
resistance is only linearly proportional to length of stenosis, whereas resistance increases
fourfold relative to luminal radius decrease. Determining the cause of fixed intrinsic tracheal
narrowing in a symptomatic child is crucial.
References
Berrocal T, Madrid C, Novo S, Gutiérrez J, et al. Congenital anomalies of the
tracheobronchial tree, lung, and mediastinum: embryology, radiology, and pathology.
Radiographics. 2004;24:e17.
Zylak CJ, Eyler WR, Spizarny DL, Stone CH. Developmental lung anomalies in the adult:
radiologic-pathologic correlation. Radiographics. 2002;22 Spec No:S25-43.
4.31 Answer: D
Compression and displacement of the trachea and oesophagus as a result of anomalous
development of the aorta and its branches are not uncommon in the paediatric patient. A
majority of patients are asymptomatic, but patients may present with respiratory and
gastrointestinal symptoms. The malformations that most frequently cause stridor are a double
aortic arch, a right aortic arch with a left ligamentum arising from the descending aorta, and
an aberrant right subclavian artery arising on the left and passing posterior to the trachea or
retroesophageal right subclavian artery. The first two aortic arch anomalies are true complete
vascular rings and are frequent causes of dysphagia lusoria. Rarely is a significant
oesophageal dysfunction associated with an aberrant retroesophageal right subclavian artery,
which does not constitutes a true vascular ring and must be considered as representing
persistence of the right-sided aortic elements.