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Key Questions in CONGENITAL CARDIAC SURGERY
In tetralogy of Fallot, Doppler assessment of the right ventricular
•
outflow tract demonstrates a dual-profile waveform (Figure 27). The
smooth ellipse represents the fixed obstruction at the pulmonary
valve level, whereas the triangular dagger-shape trace represents the
dynamic obstruction from the muscular infundibulum.
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Figure 27. Continuous wave Doppler across the right
ventricular outflow tract demonstrating a peak gradient
>100mmHg with a dual-profile waveform, consisting of a
fixed parabolic-shaped and dynamic dagger-shaped
obstruction.
One of the most important features to check on echocardiography is
•
evidence of a coronary artery crossing the right ventricular outflow
tract, as this will alter the surgical approach. A key abnormality is the
left anterior descending artery arising from the right coronary artery
in 3% of cases. This is best imaged in the parasternal short-axis view
but in cases where the coronary artery anatomy is not clear, a CT
scan may be indicated.
Postoperatively, assessment of the blood flow within the RVOT will
•
differ depending on the type of repair, including:
a) valve-sparing technique — unobstructed forward flow with
limited pulmonary valve regurgitation;
b) transannular patch — unobstructed forward flow and free
pulmonary regurgitation;
c) RV to PA conduit — unobstructed forward flow and good flow
into the branch pulmonary arteries. Over time, obstruction may
develop and can be assessed by increased flow velocity on
Doppler echocardiography.
4 Congenital echocardiography
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16 What are the principles of assessing pulmonary atresia
with an intact septum on echocardiography?
There are two distinct types of pulmonary atresia with intact
•
ventricular septum (PA-IVS), including with a:
a) hypoplastic right ventricle;
b) dilated right ventricle (less common).
Assessment of PA-IVS with a hypoplastic right ventricle includes:
•
a) tricuspid valve annulus size — which is measured in the apical
view with a Z-score quantification against body surface area;
b) tricuspid regurgitation — which is assessed by colour Doppler
on the same view;
c) right ventricle size — which is assessed from the apical and
parasternal short-axis views, and compared to left ventricular
size. These views are also used to identify evidence of RV
hypertrophy or endocardial fibroelastosis, which is suggested
by a bright myocardial appearance on echocardiography;
d) RV sinusoids — which are communications between the RV
cavity and the coronary arteries, found in 50% of cases, and
best assessed in the apical and short-axis windows, with
colour flow Doppler;
e) luminal discontinuity between the RV and main pulmonary
artery — which is demonstrated by a lack of forward flow on
colour flow Doppler assessment of the RVOT, and can be
assessed from a number of echocardiographic windows,
including the subcostal short-axis and oblique views, and the
parasternal long- and short-axis views;
f) pulmonary valve atresia — which is seen in almost all patients;
g) main and branch pulmonary arteries size — which are usually
normal in size, and visualised in the parasternal short-axis and
high parasternal views.
151
Assessment of PA-IVS with a dilated right ventricle includes:
•
a) severity of tricuspid valve regurgitation — which is best
assessed from the apical view utilising colour flow Doppler;
b) severity of right atrial and RV dilatation — which requires
multiple views including apical, long- and short-axis;
c) membranous atresia of the pulmonary valve — which is usually
seen;
d) main and branch pulmonary arteries size — which are usually
normal in size.
152
Key Questions in CONGENITAL CARDIAC SURGERY
17 What are the principles of assessing pulmonary atresia
with ventricular septal defect on echocardiography?
In pulmonary atresia with VSD, the branch pulmonary arteries are
•
commonly hypoplastic, as compared to the normal calibre branch
pulmonary arteries found in pulmonary atresia with intact ventricular
septum.
These branch pulmonary arteries are usually supplied by multiple
•
major aortopulmonary collateral arteries (MAPCAs) rather than a
single duct.
To assess this by echocardiography, high parasternal short-axis and
•
suprasternal notch views should be used (Figure 28).
When multiple collaterals are present, assessment by CT is useful to
•
clearly delineate the course of the vessels and guide surgical
planning.
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Figure 28. A) High parasternal short-axis view; and B) corresponding
colour flow Doppler image demonstrating pulmonary atresia,
characterised by pulmonary artery branches without a connection to the
main pulmonary artery. Ao = aorta; RPA = right pulmonary artery; LPA =
left pulmonary artery.
18 What are the principles of assessing transposition of the
great arteries on echocardiography?
A number of views and sweeps are used to determine ventriculo-
•
arterial discordance and the presence or absence of the common
associated features.
4 Congenital echocardiography
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The pulmonary artery is seen to arise from the left ventricle and
•
bifurcates into the right and left pulmonary arteries, whilst the aorta
arises from the right ventricle with branching of the head and neck
vessels.
The classic diagnostic view is the parasternal long-axis view, which
•
shows parallel great vessels (‘gun-barrel appearance’, Figure 29).
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Figure 29. Parasternal long-axis view demonstrating
transposition of the great arteries, characterised by
parallel great vessels with the pulmonary artery (PA)
arising from the left ventricle (LV) and the aorta (Ao)
arising from the right ventricle (RV). LA = left atrium.
In the parasternal short-axis view, both the aortic and pulmonary
•
valves are viewed ‘en face’, compared to the usual view of the aortic
valve ‘en face’ and length of the main pulmonary artery. From this, the
relationship of the aorta and pulmonary artery can be determined
with the aorta typically anterior and to the right, although a side-byside arrangement can also occur.
Pulmonary artery flow from the patent ductus arteriosus, which can
•
be seen on the subcostal and apical views, also helps to distinguish
it from the aorta.
153
154
Key Questions in CONGENITAL CARDIAC SURGERY
Pre-operatively, a number of other echocardiographic features
•
should also be assessed, including:
a) interatrial communication — size and flow velocity;
b) presence and location of a VSD;
c) position of the aorta relative to the pulmonary artery;
d) coronary artery anatomy — which can be assessed using the
parasternal short-axis view, as well as the apical and subcostal
views. The most common coronary artery pattern is the left
coronary artery arising from sinus 1 and the right coronary
artery from sinus 2, using the Leiden convention for naming
sinuses. The presence of an intramural course of a coronary
artery is also important to rule out or to highlight to the
surgeon, as this is associated with a higher intra-operative risk
when the arterial switch is performed;
e) presence of any outflow tract obstruction;
f) evidence, size and flow pattern of the PDA.
Following an arterial switch operation, postoperative
•
echocardiographic imaging shoud include assessment of:
a) myocardial function — as a key indicator of coronary artery
function;
b) neo-aortic root — for evidence of dilatation and neo-aortic
valve regurgitation;
c) right ventricular outflow tract and branch pulmonary arteries —
for evidence of stenosis. The branch pulmonary arteries can be
seen in the suprasternal view following the Le Compte
manoeuvre.
19 What are the principles of assessing coarctation of the
aorta on echocardiography?
Coarctation of the aorta can be assessed on several different
•
echocardiographic views, including:
a) suprasternal long-axis view (Figure 30) with ductal cuts —
which typically demonstrate a:
i) localised discrete juxtaductal narrowing, with a thin
fibrous membrane shelf protruding from the posterior
wall, just distal to the origin of the left subclavian artery.
In some cases, the narrowing may be a long segment or
associated with hypoplasia of the transverse arch;
4 Congenital echocardiography
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155
Figure 30. Suprasternal long-axis view of coarctation
of the aorta demonstrating: A) a localised discrete
juxtaductal narrowing, with a shelf (arrow) protruding
from the posterior wall, just distal to the origin of the left
subclavian artery; B) aliasing (yellow colour) at the
coarctation site on the corresponding colour flow
Doppler image; and C) lower-velocity Doppler with a
characterstic diastolic tail on continuous wave
Doppler.
ii) high-velocity turbulence at the coarctation site on colour
flow Doppler;
iii) characteristic diastolic tail pattern with continuous wave
(CW) Doppler at the coarctation site (high peak systolic
velocity with diastolic run-off);
b) situs view — which reveals reduced pulsatility of the abdominal
aorta;
156
Key Questions in CONGENITAL CARDIAC SURGERY
c) abdominal aortic pulsed wave (PW) Doppler image — which
shows the characteristic continuous low-velocity anterograde
flow with a prolonged time to peak velocity (Figure 31).
Figure 31. Abdominal aortic pulsed wave Doppler
image in a patient with coarctation of the aorta
demonstrating a low-velocity and diastolic continuation.
In addition, there are some echocardiographic clues that are
•
suggestive of neonatal coarctation, including:
a) high left atrial pressure;
b) disproportionate ventricles, with a smaller left ventricle and
right heart dilatation;
c) mitral stenosis, aortic stenosis or left ventricular hypertrophy;
d) impaired left ventricular systolic function;
e) increased distance between the left subclavian and the left
common carotid arteries (50% greater than the distance
between the innominate and the left common carotid arteries)
in the arch view.
20 What are the principles of assessing truncus arteriosus
on echocardiography?
Truncus arteriosus arises as a solitary arterial vessel from the base of
•
the heart, giving rise to the aorta, pulmonary and coronary arterial
supply. It is best seen in the subcostal and apical five-chamber views
(Figure 32).
4 Congenital echocardiography
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Figure 32. Echocardiography images demonstrating Type I truncus
arteriosus characterised by: A) branching of the truncus into the aorta and
pulmonary artery, and a dysplastic truncal valve (arrow); and B) truncal
valve regurgitation (arrow) and forward flow into the branch pulmonary
arteries. Ao = aorta; PA = pulmonary artery; TA = truncus arteriosus; RV =
right ventricle; LV = left ventricle; RPA = right pulmonary artery; LPA = left
pulmonary artery.
Echocardiographic assessment of a patient with truncus arteriosus
•
should include:
157
a) size and location of the VSD;
b) truncal valve structure, number of leaflets (best seen in the
parasternal short-axis view) and degree of truncal
regurgitation;
c) type of truncus arteriosus — with Type I being the commonest
(50-65%);
d) coronary artery variation — with a single coronary artery
frequently occurring.
Care must be taken on echocardiography to distinguish truncus
•
arteriosus from an aortopulmonary window or aortic atresia with a
hypoplastic ascending aorta.
21 What are the principles of assessing congenitally
corrected transposition of the great arteries on
echocardiography?
Congenitally corrected transposition of the great arteries (ccTGA) is
•
characterised by the combination of atrioventricular (AV) discordance
and ventriculo-arterial (VA) discordance.
Key Questions in CONGENITAL CARDIAC SURGERY
On echocardiography, the only anomaly that may be seen is the
•
ventricles are switched around, with the morphological RV being on
the left and the morphological LV being on the right.
As the ventricles can be identified by their atrioventricular valves,
•
which remain constant, the morphological RV can be recognised as
it is attached to the tricuspid valve, which is offset apically, having a
more inferior attachment on the interventricular septum than the
mitral valve (Figure 33).
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158
Figure 33. Echocardiographic images demonstrating congenitally corrected
transposition of the great arteries (ccTGA): A) pre-operative images with
reverse offsetting of the mitral (green arrow) and tricuspid valves (blue arrow),
with the more inferiorly inserted tricuspid valve being on the left, as well as the
presence of a ventricular septal defect (*); B) postoperative images following a
double-switch procedure, where the baffle of the left atrium (LA, green asterisk)
can be seen towards the right-sided mitral valve and morphological left
ventricle (mLV). The baffle of the venous drainage from the right atrium (RA,
blue asterisk) to the morphological right ventricle (mRV) can be seen on the left;
C) corresponding colour flow Doppler image following a double-switch
procedure illustrating pulmonary venous blood passing through the baffle to the
right side of the heart.
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In ccTGA, the coronary arteries are inverted, with the
•
morphologically left coronary artery (LCA) arising from the patient’s
right-sided sinus and the morphologically right coronary artery (RCA)
from the left-sided sinus.
A variety of coronary arterial patterns, however, can be seen, with the
•
most common being a single sinus origin of the two main coronary
arteries or the LCA arising from RCA.
Although careful pre-operative echocardiographic imaging can
•
delineate the coronary anatomy, a CT, MRI or angiography may also
be required.
4 Congenital echocardiography
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In addition, a number of associated anomalies should be identified,
•
inlcuding:
a) ventricular septal defect — which is commonly a
perimembranous outflow subpulmonary defect. It is important
to note that in the presence of a large VSD with inlet extension,
especially with straddling or overriding of the tricuspid valve,
the normal reverse offsetting clue is not present on
echocardiography;
b) LV outflow tract obstruction — which may be seen as stenosis
at a subpulmonary or pulmonary valve level;
c) abnormalities of the tricuspid valve (frequently Ebstein’s
anomaly) — which is seen on the left-sided morphological right
ventricle in the apical four-chamber view.
In the long-term follow-up of these patients, it is important to assess
•
a number of factors, including:
a) systemic RV function, as most patients will develop
progressive RV dysfunction, and in some cases, as early as the
first decade of life;
b) PA band gradient and careful evaluation of the pulmonary
artery branches for distortion, in patients who have undergone
temporary pulmonary artery banding to train the morphological
LV;
c) biventricular function to guide the need for resynchronisation
therapy;
d) tricuspid valve function and degree of regurgitation — to
determine the need for tricuspid valve replacement.
22 What are the principles of assessing double-outlet right
ventricle on echocardiography?
Double-outlet right ventricle (DORV) is best seen in the parasternal
•
long-axis view, when the aorta overrides the interventricular septum
by >50%. (Figure 34).
The VSD can be subaortic, subpulmonary or doubly committed, and
•
rarely even, non-committed.
DORV can be found in association with tetralogy of Fallot, aortic
•
stenosis or coarctation.
The Taussig-Bing malformation associates a double-outlet right
•
ventricle with a subpulmonary VSD and discordant ventriculo-arterial
connections (Figure 35).
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