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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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10 Cardiac CTA in the Evaluation of CABG
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10.1.4 Clinical CTA Review
Postsurgical Coronary
of
Revascularization
The CTA review of the surgical revascularized
heart consists of evaluation of the native coronary
anatomy, the grafts, and the extracoronary structures. The CTA is reviewed on a workstation multiplanar (MPR), curved MPR (MPRc), and 3D
volume rendered. A typical approach is commencing with a review of the extracoronary structures followed by the native coronary anatomy.
The purpose of reviewing the native coronary
arteries first is to understand which arteries are
diseased and deserve a bypass. It helps to mentally calculate how many grafts are expected and
then proceed to look for them. This systematic
approach allows formulation of conclusions that
make anatomic sense and are clinically relevant.
As an example, in a patient with an intact left ventricle, right dominant anatomy where the left main
coronary artery and RCA have high- grade
obstruction, one would expect to encounter a minimum of three grafts. In a similar case but with an
old large myocardial infarct in the territory of the
LAD, there may be only two grafts present, since
the infarcted myocardium may not have required
revascularization. Thus, a minimum of two grafts
would be expected (Fig. 10.1j).
Unfortunately, many times it is not this simple
since the surgical technique may have variables
such as adequate native distal coronary artery targets, coronary anatomic variants, diseased aorta,
combined percutaneous coronary intervention,
and previous surgery. Regardless, it is important
to attempt to understand anatomically how the
myocardium is receiving blood flow, whether it is
compromised, correlates with the other noninvasive testing, and the patient symptoms.
The native coronary artery proximal to a patent graft is commonly irrelevant since the graft
has taken its place in supplying the distal flow.
Also, the proximal native segments typically
develop accelerated disease and commonly have
a heavily calcified and atretic appearance. The
grafts are reported individually as to their origin,
targeted coronary artery, and whether they are
patent or diseased. The description of graft stenosis may be quantified by a percentage or degree
of obstruction.
Disease in the wall of the graft that does not
cause obstruction may be termed nonobstructive.
High-grade obstruction refers to greater than
70% stenosis. Moderate obstruction refers to
50–70% stenosis and mild obstruction less than
50% stenosis. It is also important to report
whether disease is present in the distal anastomosis and distal coronary artery runoff.
Grafts are counted by the number of distal
anastomosis. As an example, a LIMA to the distal LAD is considered a CABG ×1. A sequential
LIMA to the second diagonal and distal LAD is
considered a CABG ×2. Adding a sequential vein
graft to three obtuse marginal branches would
add to CABG ×5 although there are only two surgical vascular conduits.
Both the terms, SVG and VG, are used to refer
to the saphenous vein graft.
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10.2 Case 1
10.2.1 History
A 78-year-old, asymptomatic male with a history
of questionable ischemia in the anterior wall on a
nuclear perfusion scintigram presented, with status post prior coronary artery bypass graft
(CABG) ×3, 5 years previously.
10.2.2 Findings
There is a patent left internal mammary artery
(LIMA) graft to the distal LAD. There are also
two patent vein grafts to the second obtuse marginal (SVG–OM2) and to the posterior descending arteries (SVG–PDA) (Fig. 10.2a–e).
10.2.3 Diagnosis
The diagnosis is multiple patent grafts.
10.2.4 Discussion
CT is an excellent noninvasive study for the evaluation of coronary postsurgical revascularization.
Analysis of the grafts consists of the evaluation
of the proximal anastomosis, the body of the
graft, the distal anastomosis, and runoff. The
grafts generally have an equal luminal diameter
throughout. It is common for the grafts to have
adjacent surgical clips that may cause significant
metal artifact and render a segment of the graft
nonevaluable. Grafts are evaluated in the axial
plane (source images), curved reformatted reconstruction (cMPR), and volume rendered (VR).
10.2.5 Pearls and Pitfalls
A graft cannot be considered patent unless the full
extent of the graft has been evaluated. An exception, in our experience, is surgical clip artifacts in
the body of an internal mammary graft since a diseased internal mammary artery graft is different
from that of a vein graft. For further information,
refer to the introduction of this chapter.
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Fig. 10.2 (a, b) Volume rendering: Patent left internal
mammary artery (LIMA) to the distal LAD, vein graft
(SVG) to OM2, vein graft to the PDA (arrows). (c) cMPR,
SVG–OM2, proximal, body, and distal anastomosis
(arrows). Adjacent metal surgical clips do not cause sig-
nificant artifact. (d) cMPR, patent LIMA to the distal
LAD. Adjacent metal surgical clips do not cause significant artifact. (e) cMPR, patent SVG–PDA. Adjacent
metal surgical clips do not cause significant artifact
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10.3 Case 2
10.3.1 History
A 77-year-old male presented with a history of
mitral regurgitation, a chronic inferior wall MI,
and status post CABG ×4 in the previous 10 years.
The patient complained of increasing shortness
of breath. No reversible ischemia was identified
on the nuclear stress test.
10.3.2 Findings
There is a sequential vein graft (VG) to OM1 and
OM2. The mid-body of the graft is diseased and
is subtotally occluded. More distally in the body
of the graft, there is also high-grade obstruction
(Fig. 10.3a–c). There is a mildly diseased SVG to
the posterior descending artery, without flowlimiting stenosis (Fig. 10.3d). There is a patent
LIMA graft to the first diagonal artery
(Fig. 10.3e). The LAD is short and occluded.
There is a large chronic transmural myocardial
infarction involving the inferolateral and posterior walls of the left ventricle. There is also
chronic ischemic changes of the posterior papillary muscle (Fig. 10.3e).
10.3.4 Discussion
The CTA clearly demonstrates a subtotally
occluded SVG to obtuse marginal arteries. The
patient underwent coronary angiography
(Fig. 10.3g), with subsequent successful PCI and
stenting of the subtotally occluded segment and
also the more distal area of high-grade obstruction in the graft (Fig. 10.3h). The initial angiogram images demonstrated extremely poor flow
beyond the subtotally occluded graft segment and
nonvisualization of the first anastomosis.
Following stenting, there was brisk flow through
the graft with good visualization of OM1 and the
distal graft anastomosis (Fig. 10.3i, j).
10.3.5 Pearls and Pitfalls
Although contrast density was not well identified
on the CTA in the area of critical stenosis in the
SVG, it was concluded that it was subtotally
occluded since the rest of the graft opacified. When
vein grafts thrombose, the most common finding on
CTA and coronary angiography is a proximal short
stump in the ascending aorta with no distal flow.
10.4 Case 3
10.3.3 Diagnosis
The diagnosis is critically diseased sequential
SVG to obtuse marginal arteries.
10.4.1 History
A 50-year-old male presented with a history of
atypical chest pain and CABG in the previous
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Fig. 10.3 (a) Volume rendering: Subtotal occlusion in
the mid-body of the VG–OM (arrow). (b, c) cMPR,
stretch cMPR: SVG–OM, mid-body graft subtotal occlusion (proximal arrow). High-grade obstruction in the graft
more distally (lower arrow). Proximal to the first stenosis,
there is calcification in the wall of the graft. (d) cMPR,
VG–PDA. Minimally diseased SVG to the posterior
descending artery. The proximal anastomosis has an adjacent surgical clip artifact (upper arrow). The mid-body of
the graft has mild nonobstructive disease (mid-arrow).
The distal anastomosis is well identified and free of disease (lower arrow). (e) cMPR, LIMA-D1. Patent internal
mammary artery graft to the first diagonal artery. Ostium
of the graft (upper arrow) and distal anastomosis (lower
arrow). (f) Axial: Chronic transmural inferolateral and
posterior wall MI, with involvement of the posterior papillary muscle (arrows), causing dysfunction of the mitral
valve apparatus and mitral regurgitation. (g) Coronary
angiogram (CA) of the SVG stenosis (arrows). There was
sluggish flow with very diminished opacification of the
graft beyond the subtotally occluded segment. (h) CA,
shortly after stenting demonstrates marked improvement
of flow in the graft. (i, j) CA, subsequent good opacification of OM1 and the distal anastomosis (arrows)
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5 years. The nuclear medicine stress test was
equivocal.
10.4.2 Findings
There is a surgical Y graft consisting of a patent
LIMA graft to the distal LAD and a patent radial
artery graft arising from the LIMA. The radial
graft is sequential to obtuse marginal arteries
(Fig. 10.4a–d). The RCA is a dominant artery
with localized high-grade obstructing calcified
plaque in the proximal segment (Fig. 10.4e).
10.4.3 Diagnosis
The diagnosis is patent arterial grafts, with highgrade obstruction in the proximal RCA.
10.4.4 Discussion
The case demonstrates the sole use of arterial
grafts and surgically creating a Y anastomosis of
a radial artery from the left internal mammary.
The selection of the LIMA to the LAD is preferred since the 10-year patency rate is greater
than 95%. The radial arteries are occasionally
used as grafts and can be surgically grafted from
the ascending aorta, a vein graft, or, as in this
case, from the internal mammary artery. Some
surgeons elect not to perform this type of Y procedure since it is technically challenging and
may compromise the mammary artery at the time
of surgery.
10.4.5 Pearls and Pitfalls
It may be difficult to identify the arterial graft
anastomosis on the axial view, for which the volume rendered images can prove helpful. The
LIMA should not be confused as a single sequential graft to the LAD and obtuse marginal arteries
since it does not have the required length.
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Fig. 10.4 (a, b) Volume rendering: Surgical Y graft of
the left internal mammary artery (LIMA) and a radial
artery. (c) cMPR: LIMA-radial artery anastomosis (A).
(d) cMPR: upper arrow: LIMA; middle arrow: radial
artery anastomosis; lower arrow: distal LIMA–LAD
anastomosis. (e) cMPR, RCA: High-grade obstruction in
the proximal RCA by calcified plaque (arrow). (f)
Angiogram: Surgical arterial Y graft and anastomosis
(A). (g) Angiogram, RCA: High-grade obstruction in the
proximal RCA (arrow)
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10.5 Case 4
10.5.1 History
A 72-year-old male presented with a history of
atypical chest pain and CABG ×2 in the previous
15 years. The nuclear medicine stress test result
was negative.
10.5.2 Findings
There is a patent LIMA graft to the distal
LAD. There is a diffusely diseased SVG (VG–
OM) to the first obtuse marginal artery. The graft
has three distinct focal areas of high-grade and
critical obstruction (Fig. 10.5a–d).
10.5.3 Diagnosis
The diagnosis is diffusely diseased vein graft
(SVG), with high-grade obstruction.
10.5.4 Discussion
The SVG to the obtuse marginal artery has diffuse
disease in the walls consisting of mixed mostly
calcified plaque. In the body of the graft, there are
three distinct areas of high-grade and critical
obstruction. There was no obstruction in the proximal and distal anastomoses (Fig. 10.5a–c).
The patient underwent coronary angiography
with stenting of the stenotic segments of the graft
(Fig. 10.5e, f) and with good results.
The 10-year patency rate of a vein graft is estimated at 50–60%. These develop disease in the
wall similar in appearance to that in a native artery
and eventually may thrombose and occlude. CTA
may easily demonstrate areas of flow-limiting stenosis which are amenable to stenting.
10.5.5 Pearls and Pitfalls
The vein grafts usually (not always) have similar
caliber from the proximal to distal anastomosis.
Fig. 10.5 (a–c) Volume rendering, cMPR and stretched
SVG–OM: Diffusely diseased vein graft with three focal
areas of high-grade obstruction (arrows). (d) cMPR:
Patent LIMA–LAD. (e, f) Angiogram: Pre- and poststenting with good results
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10.6 Case 5
10.6.1 History
A 70-year-old male presented with a history of
atrial fibrillation, prostate CA, shortness of
breath, previous myocardial infarction (MI), and
status post CABG ×3.
10.6.2 Findings
There is a patent sequential LIMA graft to D1
and the distal LAD. There is a patent but mildly
atretic RIMA graft to OM1 (Fig. 10.6a–d). There
is mild enlargement of the left atrium and left
ventricle. There is a large chronic left ventricular
transmural anteroseptal and apical myocardial
Fig. 10.6 (a, b) Volume rendering, cMPR: Patent sequen-
tial LIMA to D1 and to the distal LAD. Left ventricular
anteroseptal and apical MI (arrows). (c, d) Axial and
cMPR: Patent mildly atretic RIMA graft to OM1. The
RIMA courses posterior to the aortic annulus. There is a
filling defect in the left atrial appendage suggesting a
thrombus (arrows). (e) Atrial fibrillation. (f) Anteroseptal
and apical LV myocardial infarct (long arrow). Bilateral
pleural effusions (PE). Widespread bony blastic metastatic
disease from known prostate carcinoma (short arrows)
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infarct. There is a filling defect in the left atrial
appendage that is consistent with a thrombus.
Additionally, there are large bilateral pleural
effusions and widespread blastic metastatic disease to the thoracic spine, rib cage, and sternum
(Fig. 10.6f).
10.6.3 Diagnosis
The diagnosis is patent internal mammary arterial grafts. Left ventricular failure and widespread bony metastatic disease from prostate
carcinoma.
10.6.4 Discussion
LIMA jump grafts are usually placed in the
territory of the LAD. The right internal mammary artery (RIMA) can be grafted to the territory of the left circumflex by passing it
posterior to the aorta (i.e., through the transverse sinus), as in this case. The RIMA is
placed posterior to the aorta since it is the
shortest distance to the territory of the circumflex and to avoid injury to the artery during a
reoperation. Since the patient had atrial fibrillation (Fig. 10.6e), the study was reconstructed
in the 40% phase (end-systole) and obtaining
diagnostic images and segmentation of the
grafts.
10.6.5 Pearls and Pitfalls
The native position of the internal mammary
arteries in the chest wall should be inspected.
The absence of an IMA in the expected location is a clue that the artery may have been surgically grafted. Atrial fibrillation is not a
contraindication for CTA in our laboratory
since we use an adaptive multicycle reconstruction algorithm that corrects for beat-tobeat variability.
10.7 Case 6
10.7.1 History
An 84-year-old male presented with a history of
atypical chest pain, LV apical ischemia on a
nuclear stress perfusion scintigram, and status
post CABG ×4 in the prior 2 years.
10.7.2 Findings
There is a patent LIMA graft to the distal LAD
and a vein graft (SVG) to the posterior descending artery. There is a sequential SVG to D1 and
OM2 that has high-grade obstruction in the proximal segment (Fig. 10.7a–e).
10.7.3 Diagnosis
The diagnosis is high-grade obstruction in the
proximal segment of an SVG.
10.7.4 Discussion
Over time, vein grafts become diseased and can
develop obstruction. The unusual finding in this
case is that the obstruction was present within the
first 2 years of the surgery. Note that the CTA demonstrates no disease in the wall of the rest of the
graft, and the area of stenosis has no calcification or
other disease other than the focal luminal narrowing, which may suggest an operative complication.
When a vein is harvested for grafting, it is important
to appropriately handle the graft so as not to cause
injury that could later develop stenosis. Pressure
injuries, poorly ligated side branches, and kinking
or twisting of the vein may cause stenosis. The
patient underwent coronary angiography, which
confirmed the findings on CTA and was subsequently stented with excellent results (Fig. 10.7f–h).
10.7.5 Pearls and Pitfalls
A perioperative complication should be considered when a vein graft has focal stenosis without
disease in the wall, particularly in the first 5 years
of revascularization.
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