CT coronary angiography (CTA) is indicated for evaluating stable chest pain when CAD is unknown or known, and after nonconclusive functional tests. It can assess plaque characteristics like vulnerability features. CTA guides treatment by identifying obstructive CAD needing revascularization versus non-obstructive CAD managed medically. Interpretation considers stenosis severity per CAD-RADS, and plaque features like low attenuation or positive remodeling indicate high risk. Motion artifacts must be distinguished from noncalcified plaque. CTA accurately rules out flow-limiting CAD and guides appropriate medical versus invasive management.

1. CT Coronary Angiography :
Indication & Interpretation
Dr Awadhesh Sharma

2. Indications of CTA in
current scenario

5. Stable chest pain
1. No Known CAD:
 Appropriate as the first line test in stable typical or atypical chest pain, or other symptoms
which are thought to represent a possible anginal equivalent (e.g. dyspnoea on exertion,
jaw pain).
 After a nonconclusive functional test, in order to obtain more precision regarding diagnosis
and prognosis, if such information will influence subsequent patient management.
 May be appropriate in some asymptomatic high-risk individuals, such as those with a
higher likelihood of non-calcified plaque.
 Rarely appropriate in very low-risk symptomatic patients – those under age 40 with non-
cardiac symptoms – or those with low- to intermediate-risk asymptomatic patients.

6. Indications..
2. Known CAD:
 It is appropriate to perform CTA as a first line test for evaluating patients with known CAD
who present with stable typical or atypical chest pain, or other symptoms which are
thought to represent a possible anginal equivalent (e.g. dyspnea on exertion, jaw pain).
3. Functional imaging:
 It may be appropriate to perform CT derived FFR and CT myocardial perfusion Imaging to
evaluate the functional significance of intermediate stenoses on CTA (30-70% diameter
stenosis).
 Add FFRCT and stress-CTP to CTA to increase specificity, positive predictive value, and
diagnostic accuracy.
 CTP can be a valuable alternative when CT-FFR is technically difficult.

7. Indications..
4. Stable Coronary Artery Disease: CCTA Post-Revascularization
 In intra-coronary stent ≥ 3.0 mm, implementing measures to improve stent imaging
accuracy, such as heart-rate control, iterative, sharp kernel, and mono-energetic
reconstruction.
 CCTA is appropriate to evaluate patients with prior CABG, particularly for graft patency,
and to visualize grafts and other structures prior to cardiac surgery re-do.
 Protocols to optimize stent imaging should be developed and followed. It may also be
appropriate to perform coronary CTA in symptomatic patients with stents <3.0 mm,
especially those known to have thin stent struts (<100 mm) in proximal, non-bifurcation
locations.

8. Indications..
5. Stable Coronary Artery Disease: CCTA in Other Conditions
Asymptomatic high risk subjects:
 may be appropriate in selected asymptomatic high risk individuals, especially in those who
have a higher likelihood of having a large amount of non-calcified plaque.
 Asymptomatic low or intermediate risk : rarely appropriate.
 Coronary artery bypass grafts : It is appropriate to perform CTA for evaluation of
patients with prior CABG, particularly if graft patency is the primary objective.

9. Other Indications:
 CTA is appropriate for coronary artery evaluation before non-coronary cardiac
surgery as an equivalent alternative to invasive angiography in patients with low-
to-intermediate probability of CAD and younger patients with primarily non-
degenerative valvular conditions.
 CTA is appropriate to exclude coronary artery disease in patients with suspected
non-ischemic cardiomyopathy.
 Late enhancement CT imaging may be appropriate to pinpoint infiltrative heart
disease or scar in some patients who have non-ischemic or ischemic
cardiomyopathy who cannot undergo cardiac MRI.

10.  CTA is appropriate for the evaluation of coronary anomalies.
 Limited delay image CTA (60 seconds-to-90 seconds) is appropriate alternative to TEE
to exclude LA/LAA thrombus, as well as in patients where TEE-associated risks
outweigh the benefits.
 Late enhancement CT imaging may be appropriate to evaluate myocardial viability in
some patients who cannot undergo cardiac MRI if it has the potential to impact
diagnosis and treatment.

11. Coronary anomalies  (A) Three-dimensional multi-detector row
computed tomography reconstruction of a
right-sided single coronary artery with a pre-
pulmonary course of the left main stem in a
42-year-old man. The left main coronary
artery (black arrows) is originating from the
proximal part of the right coronary artery
(black arrowheads; left panel) than following
a pre-pulmonary course to the anterior
interventricular groove, where the left main
coronary artery splits in the left anterior
descending coronary angiography (LAD), an
intermediate branch (RIM), and the
circumflex coronary artery (RCX, right panel).
Ao, ascending aorta; PA, pulmonary artery.
 (B) Transaxial multi-detector row computed
tomography image of a right-sided single
coronary artery with an interarterial path of
the left main stem in a 64-year-old man. The
left main coronary artery (white arrowheads)
originates from the proximal part of the right
coronary artery (black arrow) than following
an interarterial path between the ascending
aorta and the pulmonary trunk. The white
arrows indicate the mid part of the circumflex
coronary artery. Ao, ascending aorta; LA, left
atrium; LV, left ventricle.

12. Implementation In Clinical Practice

13. 1. Medical versus Invasive Treatment
 A central aim of evaluation for CAD is to identify patients who need appropriate
revascularization to improve prognosis or symptoms not responding to medical
therapy, as well as those that can be managed with medical therapy alone.
 Stenosis severity still remains the primary arbiter of therapeutic decisions, but more
and more data now suggest that anatomy coupled with a physiologic correlate is a
better or even possibly, a necessary way for optimal decision-making.

14. 2. Role of CTA for guiding further non-invasive evaluation:
 CTA facilitates decision making by dividing patients into multiple informative categories.
 Those with a negative CTA or demonstration of non-obstructive CAD would generally
exclude flow limiting CAD with high certainty and avoid downstream testing.
 CTA seems to allow for more appropriate use of statins and anti-platelet therapies better
than when using non CTA methods for CAD diagnosis.
 CTA and FFRCT may allow for even more uniform down-stream interventions and
narrow the differences between revascularization rates between men and women unlike
what happens after usual stress testing imaging.

15. How to Interpret CTA

17. Anterior projection:
Left Main or left coronary artery
(LCA)
Left anterior descending (LAD)
diagonal branches (D1, D2)
septal branches
Circumflex (Cx)
Marginal branches (M1,M2)
Right coronary artery
Acute marginal branch (AM)
AV node branch
Posterior descending artery
(PDA)

19. RAO projection:

20. Lateral Projection.

25. CAD-RADS:
 Cad-Rads is the Coronary Artery Disease-Reporting and Data System.
 It was published in 2016 by the Society of Cardiovascular Computed Tomography
(SCCT), the American College of Radiology (ACR) and the North American Society
for Cardiovascular Imaging (NASCI) and it has been endorsed by the American
College of Cardiology (ACC) .
 Cad-Rads is developed to standardize reporting of coronary CTA, to improve
communication and to guide therapy.

28. Post CABG ..

29. Vulnerable plaque…
Vulnerable plaque features include:
Low-attenuation plaque
Positive remodeling
Spotty calcification
Napkin-ring sign
If two or more of these features are present modifier “V” should
be added to the CAD-RADS category.

30. Plaque Characteristics..
 There are three plaque types on coronary CTA:
 Calcified- Atherosclerotic plaque in which the entire plaque appears as calcium density
(>130 HU on non-enhanced CT).
 Partially calcified- Atherosclerotic lesion with 2 components of which one is
calcification.
 Non-calcified- Plaque with no calcium content

31. Low-attenuation plaque- Lesions associated with plaque rupture frequently have a large lipid
rich core. Lipid on CT appears as low attenuation. Plaques with <30 HU on CTA were found to
be present significantly more often in patients with acute coronary syndrome

32. Positive remodelling- is defined as a compensatory outward enlargement of the vessel wall at
the site of the atherosclerotic lesion with preservation of the coronary lumen.
Higher lipid content and abundance of macrophages.
Can present with an acute coronary syndrome without any prior cardiac history.

33. Spotty calcification- usually defined as calcifications < 3 mm .
Small (< 1 mm), intermediate (1-3 mm) and large (> 3 mm) calcifications.
Small spotty calcifications on CTA are associated with high-risk plaques.

34. Napkin-ring sign- high-risk plaque feature on CTA.
It is defined as a central low-attenuation area adjacent to the coronary lumen and a higher “ring-
like” attenuation tissue surrounding this central area..
On histology the area of low-attenuation corresponds to the large necrotic core, while the “ring-
like” outer area correlates with fibrous plaque tissue.
The Napkin-ring sign is strongly associated with major adverse cardiovascular events.

35. Fig. 2
(A1) Presence of positive
remodeling (yellow arrows) and
low attenuation plaques (LAP,
red arrow) are the most
important determinants of
plaque vulnerability.
(A2) Stable plaques lack both
these features.
(A3) Major adverse cardiac
events by the presence of 1 or
both features in a follow up of --
- patients for 2 years, and 300
patients for up to 10 years.
(A4) Patients with HRP had 45
and 10 folds higher likelihood
of adverse outcomes,
respectively.

36. Presence of significant
stenosis over and above
HRP features (A5) and
interval progression in
plaque magnitude (A6)
increased the likelihood of
adverse events further.
Greater number of adverse
plaque characteristics
were associated with
greater of adverse
outcomes (A7) and the
HRP characteristics were
associated with abnormal
fractional flow reserve
regardless of luminal
stenosis (A8).

37. Imaging of coronary atherosclerotic plaque by
multidetector row computed tomography. The contrast-
enhanced multi-detector row computed tomography
data set shows a noncalcified plaque in the proximal
right coronary artery with substantial positive
remodelling and only a mild associated reduction of the
coronary lumen.

38. Case 1-

40.  (a) Sixty-one year old man with
vague chest pain, not typical for
angina with normal treadmill. 3D-
VR images clearly shows segment
of significant stenosis in large
diagonal branch.
 (b) The segment of stenosis, which
was missed on initial reading of
axial images as it is difficult to
visualise well, until 3D-VR images
were reviewed.
 (c) Segment of stenosis also clearly
visible on a reconstructed 3D-MIP
reconstructed to simulate LAO
cranial angio view.
 (d) Lesion seen on corresponding
angiogram view. Segment of
stenosis was subsequently treated
by PCI. Note the stenosis appears
more severe on the 3D images,
due to parameters used to create
the images

41.  (a) 58 year old man.16 MSCT scan.
In this CPR image, a short segment
of significant stenosis in the distal
RCA, is clearly visible and there is
associated non calcified plaque
seen surrounding the contrast
filled lumen (arrow).
 (b) The fibrous plaque in the lumen
of the RCA is also well visualised
on the axial image surrounding the
contrast filled narrowed lumen
(arrow).
 (c) At coronary angiography, the
segment of stenosis is seen and
corresponds to the CTCA findings

42. (a) 53 year old man with CTCA showing soft and
calcified plaque in left main extending to
bifurcation and proximal LAD. Could be easily
misread as associated with significant
stenosis by inexperienced reader.
(b) Conventional angiography recommended
because of segment of significant stenosis in
mid LAD (not shown here). Coronary
angiogram shows slight narrowing and
tapering of lumen of distal left main segment
but no significant segment of stenosis is
identified (arrow).
(c) Cross sectional image at orthogonal plane of
contrast filled normal lumen of left main
proximal to lesion in Fig. a (arrow).
(d) Cross sectional image of lumen of distal left
main at level of lesion in Fig. a showing soft
and calcified plaques (arrowhead) and
contrast filled lumen (arrow) with narrowing
of less than 20% of its diameter.

43.  A potential pitfall in the
assessment of coronary artery
stenosis is to mistake a motion
artefact for a noncalcified
plaque.
 This might particularly occur in
coronary CTA datasets of
reduced image quality. One
should always check a second
reconstruction time-point for the
presence of any noncalcified
plaque.
 If the plaque is seen only on one
of the reconstruction time
points, a motion artefact has to
be expected mimicking the
finding.
Curved-planar reformations of the right coronary artery
(RCA) at two different reconstruction time-points: At 75%
of the R-R interval a noncalcified plaque in the distal RCA
is suspected. Reviewing this area at 45% of the R-R
interval shows no evidence of plaque, proving the “lesion”
in diastole to be a motion artefact
Motion Artifact

44. summary
 In general, CTA has the advantage of visualizing the stenosis and the atheromatous
plaque as opposed to making an educated guess about its presence, as with
physiologic testing.
 CTA has excellent sensitivity for identifying flow limiting disease and has very high
negative predictive value, making it the strongest test to rule out flow limiting CAD,
especially in patients with low to intermediate risk.

45. This Photo by Unknown Author is licensed under CC BY-SA