David Tso, BSc
Nima Kashani, BSc
Arash Eftekhari, MD
Anja Reimann, MD
Chris Davison, MBChB
Ahmed Albuali, MD
Savvas Nicolaou, MD
Vancouver General Hospital
University of British Columbia
Objectives




To review the imaging modalities available in
assessing patients with acute coronary
syndrome (ACS)
To summarize the clinical trials investigating
Multi-detector CT (MDCT) in diagnosing ACS
To discuss the benefits of MDCT in assessing
ACS with regards to cost, time to diagnosis,
outcomes
To discuss the role of a Triple-Rule-Out
Protocol in evaluation of chest pain syndromes
Cause for concern

ACS is associated with increase in cardiac
death and subsequent MI

2-8% of patients with ACS are misdiagnosed
and inappropriately discharged home, which is
associated with doubling mortality rate

Important to differentiate serious causes of
chest pain from less serious causes
 Angina
 Pulmonary embolism
 Aortic dissection
Christenson J, et al. CMAJ 2004 Jun 8;170(12):1803-7
Chinnaiyan KM, Raff GL, Goldstein JA. Cardiol Clin. 2009 Nov;27(4):587-96.
White CS, Kuo D. Radiology. 2007 Dec;245(3):672-81.
Definition of ACS

Constellation of clinical symptoms that
are compatible with acute myocardial
ischemia
 STEMI & NSTEMI
 Unstable Angina (UA)

UA/NSTEMI
 ECG ST-segment depression or prominent
T-wave inversion
 +/- Positive biomarkers of myocardial
necrosis
J Am Coll Cardiol. 2007 Aug 14;50(7)
Standard of Care

Clear evidence of STEMI
 Suggestive clinical history & exam
 ST-elevation on ECG
 Positive Cardiac biomarkers
 Consider immediate reperfusion therapy
○ Fibrinolysis
○ Percuntaneous coronary intervention

Extremely low probability of ACS
 Discharge
J Am Coll Cardiol. 2007 Aug 14;50(7)
Management based on work-up

Chest pain indeterminate at initial work-up
 Atypical clinical history & exam
 ECG showing only non-specific T-wave changes
 Normal biomarkers

Further diagnostic evaluation required




Rest myocardial perfusion imaging w/ SPECT
Stress echocardiography
MRI
MDCT
White CS, Kuo D. Radiology. 2007 Dec;245(3):672-81.
J Am Coll Cardiol. 2007 Aug 14;50(7)
SPECT Benefits vs. Limitations
BENEFITS
 Highly sensitive
 90-100%

Moderate specificity
 60-78%

High negative
predictive value
 97-100%

Good prognostic
value
LIMITATIONS
 High radiation exposure
 Nuclear medicine near
ED
 Only assesses CAD and
not other causes
 Time intensive
 Potential for false
negatives
 Provides no anatomical
information
Reza Fazel et al. N Engl J Med, 27 Aug 2009, 361(9):849.
White CS, Kuo D. Radiology. 2007 Dec;245(3):672-81.
Echo: Benefits vs. Limitations
BENEFITS
 No radiation exposure
 Similar sensitivity and
specificity as
radionuclide perfusion
imaging
 Portability
LIMITATIONS
 Off hours availability
 False-negative results in
patients with small
myocardial infarctions or
unstable angina
 May fail to identify nonstructural infarcts
 Might have ischemia but no
wall abnormality
 Limited anatomical
information
White CS, Kuo D. Radiology. 2007 Dec;245(3):672-81.
Cardiovascular Magnetic Resonance

Accepted indications for assessment by CMR






Congenital heart disease
Great vessels
Acquired myocardial & pericardial disease
CAD
Role in ACS less well established
CMR may be useful in the acute setting as a
problem solving tool
 Patients with suspect ACS but no angiographic
evidence of coronary artery stenosis
 Utility in negative or equivocal findings on CT
 Establish degree of myocardial necrosis after
establishing MI
Scirica BM. J Am Coll Cardiol. 2010 Apr 6;55(14):1403-15.
Lockie et al, Circulation. 2009;119:1671-1681
MDCT in the Acute Care Setting





Provides excellent spatial resolution provides
superior information of anatomy
Provides functional information through blood
perfused volume and stress protocols
Ability for plaque analysis
Appropriate use of Triple-Rule-Out Protocol
can explore other differential diagnoses for
chest pain
MDCT imaging protocols incorporated into
ACS workup demonstrates savings in time to
diagnosis, costs while providing good patient
outcomes
CT Angiography

Direct visualization of coronary arteries was
previously limited to invasive techniques
 I.e. coronary angiography


Introduction of Multi-detector CT (MDCT) in noninvasive evaluation of CAD has become possible
MDCT performs well in detection of significant
coronary stenosis
 Sensitivity = 82-95%
 Specificity = 82-98%

Presence of coronary calcifications in patients with
ACS shown to be predictive of future cardiac events
J Am Coll Radiol. 2006 Oct;3(10):751-71.
MDCT: Occluded RCA
Benefits of MDCT

Performs well in ruling out CAD for low to
intermediate probability of CAD
 High negative predictive values
 Patients with normal scan may be discharged safely

CCTA may not provide additional relevant
diagnostic information in patients with a high
pretest probability for CAD
 May need further investigations because of low
positive predictive value
 Test of choice = Conventional coronary angiography
MDCT Limitations

Image quality suffers from fast heart rate
 Requires premedication with β-blockers

Arrhythmias, ectopy, or ECG artifacts result
in degradation of image quality
 ECG-gating critical to coronary imaging
Radiation dose to patient
 Provides anatomic information, but not
physiologic data

Chinnaiyan KM, et al. Cardiol Clin. 2009 Nov;27(4):587-96.
MDCT: Cost & time to diagnosis
Study
n
SOC
MDCT
Difference
P-value
May et al.
AJR 2009
53
$7,597
$6,153
$1,444
P<0.001
Time to
discharge
25.4 hours
14.3 hours
11.1 hours
P<0.001
749
$3,458
$2137
$1,321
P<0.001
Time to
diagnosis
6.2 hours
2.9 hours
3.3 hours
P<0.0001
197
$1,872
$1,586
$286
P<0.001
Time to
diagnosis
15.0 hours
3.4 hours
11.6 hours
P<0.001
Chinnaiyan
et al.
AHA 2009
Goldstein et
al. JACC
2007
1. Using CCTA vs. standard of care protocols (i.e. myocardial perfusion imaging) can
diagnosis patients faster
2. Cost savings come from reduce time in hospital and reduced need for additional
Goldstein et al. J Am Coll Cardiol 2007;49:863–71
tests from a negative CCTA exam
May et al. AJR 2009; 193:150–154
Ruling out Non-cardiac Causes

Routine CT acquisition has ability to examine other
non-cardiac structures
 e.g. Aorta, pulmonary arteries

Possible modality to rule out potentially fatal
causes of chest pain
 CAD
 Acute aortic dissection
 Pulmonary embolism

Triple rule out (TRO) protocol can allow in rapid
discharge of patients with low to moderate ACS risk
Chinnaiyan KM, et al. Cardiol Clin. 2009 Nov;27(4):587-96.
Triple rule out: atypical chest pain
Diagnosis = pulmonary embolism
TRO – Pericardial Effusion
 40 yo female
 Atypical chest pain
 SOB
Diagnosis = Lymphoma resulting in
pericardial effusion
TRO – Pulmonary edema
Diagnosis = Mitral Valve Prolapse
Whole Body Rule-out
Diagnosis = Aortic Dissection
Dedicated CTA vs. Triple-Rule-Out

Investigates coronary
arteries only
 Greater spatial resolution
of coronary arteries
 Less radiation
 Less contrast
 Time = 8 secs
 Craniocaudal

Investigates CAD, PE,
Aortic dissection
 Lesser spatial resolution
of coronary arteries
 More radiation
 More contrast
 Time = 15 secs
 Caudalcranial
Dedicated CTA
Triple-Rule-Out
Heart perfused volume imaging

Myocardial blood pool analyzed by
assessing iodine content within myocardium
 Using unique X-ray absorption characteristics of
iodine at different kV levels
 Color-coded “iodine maps” represent myocardial
blood pool
 Perfused myocardium contains iodine vs. an
infarct which will not have iodine uptake

Single cardiac CTA exam that examines
both coronary anatomy and myocardial
perfusion is promising
Rocha-Filho et al. Radiology: Volume 254: Number 2—February 2010
Ruzsics et al. Eur Radiol. 2008 Nov;18(11):2414-24.
Dual energy CT + adenosine stress

Recent studies show results from adenosine-mediated
CT perfusion imaging is comparable to SPECT–
myocardial perfusion in detecting perfusion abnormalities
 Allow for comparison of rest and stress DECT in detecting
perfusion deficits
 Protocol allows for quantification of iodine

DECT adenosine stress protocol enables examination of
anatomy and function in a single investigation
 Radiation exposure equivalent to SPECT

Regadenoson = selective α2a receptor agonist
 Coronary vasodilator
 Less side effects than adenosine
 Easier to use iv bolus 5cc(0.4 mg) with no weight adjustment
CTA + CT Heart Perfused Blood Volume

Combination of cardiac CT angiography and CT
perfusion in a single examination improved
diagnostic accuracy
 Comparable to SPECT–MPI
 For stenosis > 50% luminal narrowing

Combination shown to increase PPV by more than
20% after incorporation of CT perfusion analysis
over CTA alone (66% to 86%)

Myocardial hypoenhancement seen on MDCT has
potential in evaluating CAD without additional cost
in radiation dose or contrast load.
Kachenoura N, et al. Am J Cardiol. 2009 Jun 1;103(11):1487-94.
Rocha-Filho et al. Radiology: Volume 254: Number 2—February 2010
DECT - Coronary artery occlusion
Perfusion defects at rest
anterior
LAD
posterior
RCA
lateral
LCx
100% iodine overlay
100 kV (Stress)
50:50 heart perfused volume (Stress)
Heart perfused blood volume at rest
50:50
100% iodine overlay
DE – Heart blood perfused volume
Stress
Rest
Perfusion
Perfusion
Quantification of Iodine
Acute chest pain
1. High Risk
Low-tointermediate risk
No known CAD
(positive EKG ±
cardiac enzymes)
2. Known CAD
MDCT/ =
MDCT
DECT Shop
One Stop
Strong clinical
suspicion for CAD
± PE or AD
Guidelines-based
Standard of care
Intermediate/
Non-diagnostic
Abnormal
Very low risk
Normal Scan
Outpatient
follow-up
Triple
Triple
Rule-Out
Rule-Out
Stress
testing
Abnormal
Invasive
Angiography
Normal
Discharge
Acute Chest Pain
Algorithm
Chinnaiyan KM, et al. Cardiol Clin. 2009 Nov;27(4):587-96.
Conclusions





MDCT has a role as a multipurpose triaging tool in
assessing patients with atypical chest pain
MDCT has been proven in clinical trials to have great
accuracy in ruling out ACS
MDCT in combination with stress perfusion may yield
better diagnostic accuracy
Appropriate use of Triple-Rule-Out Protocol can
explore other differential diagnoses for chest pain
MDCT imaging protocols incorporated into ACS
workup demonstrates savings in time to diagnosis,
costs while providing good patient outcomes
Protocol
Triple Rule Out
FLASH GATED
Spiral Triple Rule
Out Gated
FLASH Cardiac
65 BPM
DS SPIRAL
Cardiac
mAs
(Tube A)
kV 120
Kernel B
Kernel B Kernel B Kernel B
for
Collimation Pitch Rot Time CTDI vol
Multiphasic
350
B26(Cardiac)
0.6mm x
0.4mm
370
B26(Cardiac)
0.6mm x
0.4mm
450
B26(Cardiac)
0.6mm x
0.4mm
400
B26(Cardiac)
0.6mm x
0.4mm
B36
3mm x
1.5mm
B70
3.0mm x
1.5mm
B36
3mm x
1.5mm
B70
3.0mm x
1.5mm
B36
3mm x
1.5mm
B70
3.0mm x
1.5mm
B36
3mm x
1.5mm
B25
1mm x
0.7mm
B35
1.5mm x
1.0mm
B35
1.5mm x
1.0mm
128 mm x
0.6mm
3.2
0.28
6.05
128 mm x
0.6mm
0.23
0.28
32.84
128 mm x
0.6mm
3.4
0.28
7.42
128 mm x
0.6mm
0.23
0.28
53.5
1. CTA scans use Test Bolus of 6.5cc/sec for 65 cc isovue 370, followed by a 60/40 split
bolus of saline/isovue 370, followed by 40cc of pure saline.
2. Peak HU for contrast is determined at ascending aorta, and 5-6 sec is added for
delay time for scan after contrast flow is started at the R.ACF