David Tso, BSc

Nima Kashani, BSc

Arash Eftekhari, MD

Anja Reimann, MD

Chris Davison, MBChB

Ahmed Albuali, MD

Savvas Nicolaou, MDVancouver General Hospital

University of British Columbia

Advances in Imaging in Acute Coronary Syndromes

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 causesAnginaPulmonary embolismAortic dissection 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.

Christenson J, et al. CMAJ 2004 Jun 8;170(12):1803-7

Definition of ACS

Constellation of clinical symptoms that are compatible with acute myocardial ischemiaSTEMI & NSTEMIUnstable 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 STEMISuggestive clinical history & examST-elevation on ECGPositive Cardiac biomarkersConsider 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/ SPECTStress echocardiographyMRIMDCT

J Am Coll Cardiol. 2007 Aug 14;50(7)White CS, Kuo D. Radiology. 2007 Dec;245(3):672-81.

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

White CS, Kuo D. Radiology. 2007 Dec;245(3):672-81.

Reza Fazel et al. N Engl J Med, 27 Aug 2009, 361(9):849.

Echo: Benefits vs. LimitationsBENEFITS 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 non-structural 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 diseaseGreat vesselsAcquired myocardial & pericardial diseaseCAD

Role in ACS less well established CMR may be useful in the acute setting as a problem

solving toolPatients with suspect ACS but no angiographic evidence of

coronary artery stenosisUtility in negative or equivocal findings on CTEstablish degree of myocardial necrosis after establishing

MILockie et al, Circulation. 2009;119:1671-1681

Scirica BM. J Am Coll Cardiol. 2010 Apr 6;55(14):1403-15.

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 techniquesI.e. coronary angiography

Introduction of Multi-detector CT (MDCT) in non-invasive evaluation of CAD has become possible

MDCT performs well in detection of significant coronary stenosisSensitivity = 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 rateRequires premedication with β-blockers

Arrhythmias, ectopy, or ECG artifacts result in degradation of image qualityECG-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

Chinnaiyan et al.

AHA 2009

749 $3,458 $2137 $1,321 P<0.001

Time to diagnosis

6.2 hours 2.9 hours 3.3 hours P<0.0001

Goldstein et al. JACC

2007

197 $1,872 $1,586 $286 P<0.001

Time to diagnosis

15.0 hours 3.4 hours 11.6 hours P<0.001

May et al. AJR 2009; 193:150–154Goldstein et al. J Am Coll Cardiol 2007;49:863–71

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 tests from a negative CCTA exam

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 painCADAcute aortic dissectionPulmonary 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

Dedicated CTA 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

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 poolPerfused 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

Heart perfused volume imaging

Ruzsics et al. Eur Radiol. 2008 Nov;18(11):2414-24. Rocha-Filho et al. Radiology: Volume 254: Number 2—February 2010

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

100% iodine overlay

anteriorLAD

lateralLCx

posteriorRCA

100 kV (Stress) 50:50 heart perfused volume (Stress)

Heart perfused blood volume at rest

100% iodine overlay50:50

DE – Heart blood perfused volume

Rest PerfusionStress Perfusion

Quantification of Iodine

Acute Chest Pain

AlgorithmChinnaiyan KM, et al. Cardiol Clin. 2009 Nov;27(4):587-96.

Acute chest pain

1. High Risk (positive EKG ±

cardiac enzymes)

2. Known CAD

Guidelines-based Standard of care

Low-to-intermediate risk

No known CAD

MDCT/

DECT

Abnormal

Invasive Angiography

Intermediate/

Non-diagnostic

Stress testing

Abnormal Normal

Normal Scan

Discharge

Strong clinical suspicion for CAD

± PE or AD

Triple

Rule-Out

Very low risk

Outpatient

follow-upMDCT =

One Stop Shop

TripleRule-Out

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

ProtocolmAs

(Tube A) kV 120

Kernel B Kernel B Kernel BKernel B

for Multiphasic

Collimation Pitch Rot Time CTDI vol

Triple Rule Out FLASH GATED 

350B26(Cardiac

)0.6mm x0.4mm

B36 3mm x 1.5mm

 

B70 3.0mm x1.5mm

 

  

128 mm x 0.6mm

3.2 0.28 6.05

Spiral Triple Rule Out Gated 

370B26(Cardiac

)0.6mm x0.4mm

B36 3mm x 1.5mm

 

B70 3.0mm x 1.5mm

 

B35 1.5mm x 1.0mm

 

128 mm x 0.6mm

0.23 0.28 32.84

FLASH Cardiac 65 BPM  

450B26(Cardiac

)0.6mm x0.4mm

B36 3mm x 1.5mm

 

B70 3.0mm x 1.5mm

 

  

128 mm x 0.6mm

3.4 0.28 7.42

DS SPIRAL Cardiac  

400

B26(Cardiac

)0.6mm x0.4mm

B363mm x 1.5mm

 

B25 1mm x 0.7mm

 

B35 1.5mm x 1.0mm

 

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