Download Role of cardiac CT in coronary artery diseases

Role of cardiac CT
in coronary artery
diseases
Dr. Ahmed Refaey
MBBCh, MS, FRCR
Format of the lecture
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Normal anatomy of coronary arteries
MSCT coronary angio
Clinical application of CTA
Illustrated cases
Coronary arteries anatomy
LCA “ left coronary artery “
• Normally arises from the
left sinus of Valsalva
• Courses posterior to the
right ventricular outflow
tract (RVOT), and
bifurcates into the left
anterior descending (LAD),
and the left circumflex
(LCX) branches.
Right Coronary Artery (RCA)
• Normally arises from
the right coronary
sinus (CS) and courses
in the right AV groove
toward the crux of the
heart
Diagnosis Of CAD
• Clinical Presentation
• ECG
• Echocardiography
• Stress Test
• Thallium Study
• Coronary cathetrization
• Multislice Coronary CT Scan
Methods of imaging of coronary
arteries
• Coronary catheterization
• Multislice cardiac CT
Coronary catheterization
CORONARY CATHETERIZATION
Advantages
• High resolution
• Option for intervention
Disadvantages
• X-ray exposure
• Hospitalization
• Invasive complications
Figure 21.8d
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Multislice CT coronary angiography
What is Coronary CTA?
• Coronary CTA is a non-invasive minimal risk
procedure to directly visualize the coronary
arteries through administration of IV contrast
• It allows visualization of the coronary arteries
similar to a cardiac catheterization with
additional information about the WALL of the
artery and composition of plaque (calcified or
non-calcified)
Clinical application of CTA
• Diagnosis of CAD
* intermediate liklihood of disease
* after equivocal/discordant stress imaging
* coronary anomalies
* before vascular surgury
* nonischemic vs ischemic cardiomyopathy
* acute chest pain
* bypass graft patency / location
Patient Preparation
• No Caffeine for 12 hours prior to exam
• Everyone gets Beta-Blockers (Verapamil can be substituted)
Goal Heart Rate
• < 60 bpm makes us happy
Contraindications
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Atrial Fibrillation
Tachycardia
Beta Blockade Contraindication
Heart Block
Renal Failure (Creat>1.5)
Contrast Allergy
The Examination
Computed Tomography (CT)
X-ray tube and detector rotate around the patient, transversal
slices are constructed following each rotation by computer
Spiral multislice CT
continuous scanning instead separated slices
• Entire heart imaged in 5-15 seconds
• CT images that are used come from mid to
end diastole due to relative motion free
period
CT Angiography
Timing
CT-Angio Advantage
Excellent for Coronary vessel, bypass vessels,
LV wall thickness and function, cardiac
anatomy and pericardium assessment
Coronary Vessel Analysis
Maximum Intensity Projection
Soft Plaque in Proximal LAD
Curved Planar Image
3-D Volume Rendered Image
Effective Radiation Doses for
Various Tests
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Bone Density
CXR:
Mammogram:
CT of the head:
CT colonoscopy
CT of the abdomen:
Stress Gated Myocardial Perfusion Scan SPECT:
CT chest:
MSCT angiogram:
• Coronary angiography:
• CT chest/abd/pelvis:
• Dose allowed for radiological personnel:
0.01 mSv
0.02 mSv
0.7 mSv
2 mSv
5 mSv
10 mSv
10-11 mSv
13 mSv
15 mSv
30mSv
35 mSv
20 mSv/year
CLINICAL APPLICATION OF CARDIAC CT
ANGIO
1.
2.
3.
4.
Examine plaque components
Evaluate coronary vessels
Evaluate stent patency
Assess cardiac function
Examine plaque components
Plaque Characterization
• Calcified vs. Soft
• Plaque composition rather than the degree of
lumen stenosis determines the risk of plaque
rupture.
• Vulnerable or “high-risk” plaques have thin
fibrous cap with extracellular lipid core.
• Not visible by catheterization, but is being
explored with CT angio.
• Plaques initially grow extrinsic and bulge
adventitia, then grow into the lumen resulting
in stenosis
Coronary Artery Plaque:
approximate amounts of lipid rich, fibrotic and calcified plaque
Fibrotic &
Calcified
20%
66%
Fibroti
c
33%
Lipid Rich
The “Tip of the
Atherosclerotic
80%
Iceberg”
What does coronary calcification mean?
• Calcium score correlates extremely well
with coronary event risk
• If multi-vessel CAC, then risk increases
• Zero calcification suggests a very low
probability of obstructive disease
Curved MPR reformatted
image of Right Coronary
Calcium Scoring
“ Agatston score”
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The Calcium Scale
The calcium scale is a linear scale with 4 calcium
score categories:
0
1–99
100–400
>400
none
mild
moderate
severe
*Calcium score correlates directly with risk of events
and likelihood of obstructive CAD*
Agatston-90
Examples of Coronary Artery Scans
NO
CALCIFICATION
MODERATE
SIGNIFICANT
CALCIFICATION
CALCIFICATION
Images courtesy of HeartScan San Frasco
Coronary Artery Calcium Scans
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Task: Detect Calcium in Coronary Artery
130 kVp
625 mA
.1 sec
3 mm
Coronary Artery Calcium Scans
Coronary Artery Calcium Scans
Coronary Artery Calcium Scans
Coronary Artery Calcium Scans
Coronary Artery Calcium Scans
Coronary Artery Calcium Scans
Coronary Artery Calcium Scans
Coronary Artery Calcium Scans
Coronary Artery Calcium Scans
Calcification in LAD
Calcification in RCA
EVALUATING CORONARY VESSELS
It can look even better than a
conventional angiogram
Left Main Coronary Artery
Left Main, LAD, & Circumflex
LAD
Circumflex
Obtuse Marginal
Diagonal Branch off LAD
Diagonal Branch
Right Coronary Artery
Acute Marginal
Right Coronary Artery
Sinoatrial
Right Coronary Artery
Evaluate stent patency
LAD Stent from Top to Bottom (1 mm)
LAD Stent from Front to Back (1 mm)
Cardiac function
• Recent studies show good correlation
between function parameters derived from
MDCT and levocardiography.
• DETERMINING EJECTION FRACTION
FUTURE OF CARDIAC CT
• One-stop shopping—
( cardiac function, coronary artery evaluation,
plaque analysis, calcium quantification.)
• Non-invasive
Illustrated cases
High-resolution Imaging
1
LAD
1
2
3
4
2
3
RCA
LM
4
DSCT
LCx
LM
Significant stenosis of the left anterior
descending artery
Soft Plaque Visualization
stent in LAD,LCx & RCA I
Aortic Coarctation Visualized
Fröhlich, G et al. Circulation. 2005;112:e81.
Pericardial Calcification
Multi-Slice CT Scanning Superior to MRI
Hoffmann et al. Circulation 108 (7): 48e Figure IG1
Mild CAD, and…
Pulmonary Emboli
Teaching Points
• Cardiac Cath: Lumen only-no wall information. Evaluate
stenosis. Cannot characterize plaque. Better delineates small
vessels
• What is needed is a non-invasive, minimal-risk,
outpatient procedure to detect early signs of CAD
Coronary CTA- Strengths
• Noninvasive.
• Can measure HU of plaques and characterize them as
fatty, atheroma, fibrosis, calcium.
• Can evaluate status of bypass grafts.
• Can determine stent patency.
• Evaluates portions of mediastinum and lungs.
Coronary CTA- Weaknesses
• Cannot accurately measure stenosis with heavy,
calcified plaque burden.
• Occlusions can be missed by brisk collateral flow.
What do I do with this information?
• Reports will be classified in one of four
categories of severity:
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Normal
Mild Plaque with No stenosis
Moderate Plaque with mild/Mod stenosis
Severe Plaque and stenosis: Cardiac Cath