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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3612_Библиотеки_им_академика_М_И_Перельмана
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170
Key Questions in CONGENITAL CARDIAC SURGERY
9. Ho S, McCarthy KP, Josen M, Rigby ML. Anatomic-echocardiographic correlates: an
introduction to normal and congenitally malformed hearts.
11.
10. Van Praagh R, Papagiannis J, Grunenfelder J, Bartram U, Martanovic P. Pathologic
anatomy of corrected transposition of the great arteries: medical and surgical
implications.
11. Anderson RH, Cook AC. Morphology of the functionally univentricular heart.
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12. Khairy P, Poirier N, Mercier LA. Univentricular heart.
12.
13. Backer CL, Mavroudis C. Surgical management of aortopulmonary window: a 40-year
experience.
14. Dodge-Khatami A, Mavroudis C, Backer CL. Anomalous origin of the left coronary
artery from the pulmonary artery: collective review of surgical therapy.
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15. Martinez RM, O’Leary PW, Anderson RH. Anatomy and echocardiography of the
normal and abnormal tricuspid valve.
16. Celermajer DS, Dodd SM, Greenwald SE, Wyse RK, Deanfield JE. Morbid anatomy
in neonates with Ebstein’s anomaly of the tricuspid valve: pathophysiologic and clinical
implications.
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Chapter 5
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Congenital cardiac imaging
Saeed Mirsadraee, Golnaz Houshmand
1 Describe the principles of computed tomography
A computed tomography (CT) scan combines a series of X-ray
•
images taken from different projections and the attenuation data are
used to reconstruct cross-sectional images.
Different tissues and organs are differentiated by their inherent
•
variation in attenuation; bone has high attenuation, air has the lowest
attenuation and water has intermediate attenuation.
Iodinated contrast agents are used to enhance visualisation of the
•
blood pool, such as vessels and body organs.
CT plays an important role in the characterisation of congenital
•
cardiovascular anomalies and complications post-corrective surgery.
CT exposes patients to potentially harmful ionising radiation,
•
especially the potential risk of cancer. The Ionising Radiation Medical
Exposure Regulations (IRMER) has set out responsibilities for
practitioners and operators to ensure that the benefits of the
exposure to ionising radiation outweigh the risks, and that the
radiation dose is kept ‘as low as reasonably practicable’ for their
intended use.
The main risks of exposure to iodinated contrast medium are:
•
171
a) allergic reaction, with anaphylactic reaction reported in 2 4 per
1000;
b) renal impairment, which occurs in <2% of patients. In view of
this, screening of renal function should take place prior to CT
scanning, especially in patients with a history of kidney disease
or diabetes, and older patients. Adequate hydration is helpful
to reduce the risk from contrast-induced renal impairment.
172
Key Questions in CONGENITAL CARDIAC SURGERY
2 Describe the principles of magnetic resonance
imaging
Magnetic resonance imaging (MRI) uses a strong magnetic field and
•
radiofrequency waves to produce images of body tissues.
The signal detected by MRI is generated from the magnetisation of
•
atoms with odd numbers of protons or neutrons within tissues
(mainly protons).
Cardiac magnetic resonance (CMR) plays an important role in the
•
detection of congenital anomalies and associated lesions. CMR
allows non-invasive assessment of the ventricular function and shunt
flow. CMR is widely used for the follow-up of left or right ventricular
function, size and shunt studies in repaired and unrepaired
congenital lesions and planning the timing of surgery.
Although MRI is regarded as a safe investigation, there is a potential
•
risk of the magnetic field in patients with metal and non-conditional
implantable devices.
The risk of anaphylactic reaction to contrast (gadolinium) injections is
•
present but rare (1:10,000).
Patients with renal failure are at increased risk of developing
•
nephrogenic systemic fibrosis (NSF) following contrast injection.
This condition involves fibrosis of the skin, joints, eyes, and internal
organs. The reported cases of NSF have significantly declined in
recent years and patients with reduced renal function are often
offered alternative contrast agents.
3 What are the principles of assessing coronary
anomalies with radiological imaging?
ECG-gated CT angiography is the non-invasive modality of choice
•
for the detection of the origin and assessing the course and
termination of coronary artery anomalies (Figures 1 and 2), with the
ability to define related structures and coronary artery fistulae (Figure
3).
CT is also a reliable technique for detecting myocardial bridges
•
(Figure 4).
In patients following repair of coronary anomalies, CT allows the
•
evaluation of the anastomoses and can detect the presence of any
restenosis of the grafts.
Cardiac magnetic resonance imaging enables assessment of
•
ventricular function and myocardial viability, and valvular function in
patients with coronary anomalies.
5 Congenital cardiac imaging
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AB
CD
Figure 1. Gated computed tomography coronary angiography curved
multiplanar reconstruction demonstrating: A) an anomalous origin of the
left main coronary artery (arrow) from the non-coronary sinus, with
proximal luminal attenuation; B) anomalous origin of the left circumflex
artery (arrow) from the right coronary sinus, adjacent to the origin of the
right coronary artery, with a retro-aortic course and calcified atheroma in
its mid segment; C) anomalous origin of a non-dominant right coronary
artery (arrow head) from the left coronary sinus with an obstructive noncalcified plaque (arrow); and D) anomalous origin of a dominant right
coronary artery (arrow head) from the left coronary sinus, with a nonobstructive calcified plaque (arrow).
The assessment of the coronary anomalies themselves by cardiac
•
MRI is challenging due to limited spatial resolution and data
acquisition time. Techniques, such as navigated 3D whole heart
magnetic resonance angiography, may allow adequate visualisation
of coronary anomalies. Nonetheless, it can be difficult to comment on
ostial narrowing due to less spatial resolution.
Simple steady-state free precision (SSFP) or black blood imaging in
•
a routine MRI is usually able to show the origin and proximal course
of the artery.
173
174
Key Questions in CONGENITAL CARDIAC SURGERY
AB
CD
Figure 2. Anomalous left coronary artery from the pulmonary artery
(ALCAPA): A) and B) computed tomography angiography volume-rendered
reconstructions demonstrating a tortuous dilated right coronary artery (white
arrow) and dilated collateral, which feeds the anomalous left anterior
descending artery (LAD) retrogradely (black arrow); C) computed
tomography short-axis double oblique multiplanar reconstruction
demonstrating dilated coronary arteries and subendocardial calcification
(arrow), indicating previous infarction in the LAD territory; D) cardiac
magnetic resonance imaging scan demonstrating late gadolinium
enhancement indicating subendocardial infarction in the anterior wall due to
ischaemia related to steal phenomena.
MRI is also useful as a follow-up after repair of anomalous left
•
coronary artery from the pulmonary artery (ALCAPA) for evaluation of
baffles used in the Takeuchi technique or direct reimplantation
procedures in assessing the baffle confluency and checking the
anastomotic site and reimplantation to the aortic root.
Stress MRI with adenosine is helpful in the detection of ischaemia in
•
coronary anomalies and in a postoperative patient.
5 Congenital cardiac imaging
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AB
PA
Figure 3. Computed tomography angiography in a patient with a
coronary-pulmonary artery fistula, with the: A) 3D reconstruction
demonstrating the conus branch (arrow) leading to a network of dilated
tortuous vessels communicating with the pulmonary artery (PA); and B)
axial image demonstrating a non-dilated pulmonary artery (25mm).
AB
175
Figure 4. Computed tomography coronary angiography demonstrating
bridging of the mid-left anterior descending coronary artery (arrow) on: A)
3D reconstruction; and B) coronal section. The bridged segment is 5mm at
maximum depth and 3cm in length.
4 What are the principles of assessing an atrial septal
defect with radiological imaging?
Chest radiography in adults with a haemodynamically significant
•
atrial septal defect (ASD) usually reveals cardiac enlargement, right
atrial dilatation, prominent central pulmonary arteries and pulmonary
vascular markings.
176
Key Questions in CONGENITAL CARDIAC SURGERY
MRI is indicated in patients with poor echocardiographic acoustic
•
windows, for anatomical assessment of surrounding structures and
associated anomalies, and where there is a need for non-invasive
quantification of the shunt.
MRI also allows accurate assessment of ventricular volumes and
•
function, with phase-contrast MRI allowing non-invasive calculation
of systemic and pulmonary blood flow.
CT scanning (Figure 5) plays a complementary diagnostic role in the
•
management of an ASD, including:
a) assessment of associated anomalies, such as anomalous
pulmonary venous return;
b) pre-operative planning, such as assessment of vascular
access; characterisation of the size, location and the shape of
the defect that can be used for device selection; and
assessment of coronary arteries in older patients;
c) assessment of the coronary arteries.
RV
Figure 5. ECG-gated computed tomography
(CT) angiography demonstrating a large
secundum atrial septal defect (arrow), with
shunting from the left to right atrium causing
mixing of contrast, and a dilated hypertrophied
right ventricle with flattening of the interventricular
septum. Unless technically intended, shunts
should be suspected when dense contrast is seen
in all heart chambers on CT angiography.
5 Congenital cardiac imaging
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CT scanning may also incidentally diagnose an ASD or patent
•
foramen ovale (PFO).
Equal opacification of the right and left heart chambers on CT may
•
hinder the diagnosis of a significant shunt.
5 What are the principles of assessing a ventricular
septal defect with radiological imaging?
Chest radiograph usually demonstrates dilatation of the central
•
pulmonary arteries, increased pulmonary vascularity and an
increased cardiothoracic ratio.
MRI is the modality of choice in the assessment of pulmonary and
•
systemic blood flow measurement, with the ratio providing an insight
into the haemodynamic significance of the septal defects.
MRI is also the gold standard for assessing LV function and size and
•
therefore can help in the decision making for VSD closure.
In patients who develop arrhythmias following VSD repair, late
•
gadolinium MRI can localise the scar, which can be subsequently
ablated.
Although CT scanning (Figure 6) is not the primary imaging modality
•
for VSDs, it can provide a complementary assessment of the type,
location, size and number of the VSD(s), as well as the chamber
sizes, right or left ventricular outflow tract obstruction, and coexisting
cardiac abnormalities, such as tetralogy of Fallot.
177
AB
RV
PA
Figure 6. ECG-gated computed tomography angiography
demonstrating: A) a membranous ventricular septal defect (VSD), with
contrast entering from the left ventricle to a relatively normal sized right
ventricle (RV); despite B) significant pulmonary artery dilatation.
178
Key Questions in CONGENITAL CARDIAC SURGERY
CT can be helpful in the assessment of coronary arteries and for
•
surgical planning (Figure 7), as it allows assessment of the proximity
of the VSD to the surrounding valves and the atrioventricular
conduction axis.
AB
Figure 7. ECG-gated computed tomography angiography demonstrating
a membranous ventricular septal defect (arrow): A) pre-operatively; and
B) following implantation of a closure device.
A VSD is sometimes identified incidentally on CT.
•
6 What are the principles of assessing an atrioventricular
septal defect (AVSD) with radiological imaging?
Chest radiography usually shows cardiomegaly, as well as large
•
proximal and small peripheral pulmonary arteries (peripheral
pruning). Pulmonary venous markings are more prominent in patients
with significant common AV valve regurgitation.
CT may provide further anatomical information (Figure 8), especially
•
when echocardiography is inconclusive. It is also helpful in assessing
outflow tract obstruction and defining coexisting anomalies, such as
coarctation.
In unbalanced AVSD and heterotaxy syndrome, CT scanning can be
•
useful in defining associated anomalies.
Similar to CT, MRI may also allow further anatomical evaluation and
•
can be used to follow up operated patients, as it is helpful in the
quantification of mitral regurgitation, LV size and function, and
haemodynamic evaluation of any residual shunt.
5 Congenital cardiac imaging
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Figure 8. ECG-gated computed tomography
axial image demonstrating a complete
atrioventricular septal defect, associated with
significant right ventricular enlargement and
Eisenmenger syndrome.
179
7 What are the principles of assessing tetralogy of Fallot
with radiological imaging?
CT is a fast and convenient method in both the paediatric and adult
•
populations for assessing the morphology of the right ventricular
outflow tract, pulmonary arteries and aorta (Figure 9).
Other coexisting anomalies, such as an ASD, patent ductus
•
arteriosus and aortopulmonary collaterals, can also be detected
(Figure 10).
CT is particularly useful in planning for re-do surgery, to evaluate the
•
patency of coronary arteries, and to note the relation of the heart and
large vessels to the sternum (Figure 11).
MRI is used to delineate anatomy, function and haemodynamic
•
status. It can be used in neonates with tetralogy of Fallot where there
is a facility for adequate sedation, but it is particularly helpful in the
follow-up of older children and adults with total correction of tetralogy
of Fallot. CMR allows assessment of ventricular size and function,
and quantification of pulmonary regurgitation. CMR and flow velocity
mapping can also detect and quantify any residual VSD, if present.
Phase contrast and cine MRI are the preferred modalities to quantify
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