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Great Debates in Cardiac Imaging Imaging Acute Chest Pain in The ER Feb. 15,2013

Functional Imaging is the test of choice of Acute Chest Pain in the ER Ahmed Fathala, MD KFSH&RC, Riyadh, KSA


Objectives • To Review ischemia cascade and how to utilize functional imaging • To discuss different functional imaging techniques in the ER – SPECT myocardial perfusion imaging – Echocardiography (resting, stress echocardiography) – Cardiac MRI ( Stress CMR perfusion and function)

• To highlight some of the most important limitations of anatomical imaging • Conclusion

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Imaging in Acute Chest Pain • Functional Imaging – Nuclear • MPI-SPECT • MPI-PET – Echocardiography • Resting and Stress Echocardiography – MRI • Stress MR perfusion • Stress MR wall motion

• Anatomical Imaging – CTA – MRA – Conventional Angiography 3


Functional Imaging • Functional Imaging reliably detects myocardial ischemia – – – –

Diagnosis of CAD Functional significance of a coronary stenosis Viability of the territory subtended by the stenotic artery Global and regional ventricular function

• The importance of noninvasive quantitative assessment of myocardial ischemia is well established from several randomized trails

• Anatomical imaging stenosis does not reliably predict ischemia or hemodynamic significance 4

N England J medicine 2007;356:1503-1561


The Ischemic Cascade Higher specificity

Higher sensitivity

The ischaemic cascade represents the sequence of pathophysiological events following ischaemia N Engl J Med. 1994;330:1782–1788 Circulation 2002;105: 987–992.

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Acute SPECT Myocardial Perfusion Imaging • Acute MPI is an optimal tool for identifying ischemia in low risk patients • 99TC based agents allow imaging several hours after injection • SPECT imaging is widely available in most NM department

• Recent development of SPECT – High quality imaging • Attenuation correction

– Simultaneous assessment of perfusion and function – Shorter imaging time: 2 to 3 mins

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Role of AC

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Resting SPECT Myocardial Perfusion Imaging • Patient selection – Low risk population with symptoms suggestive of ACS – Nondiagnostic EKG – Negative cardiac enzymes

• Most appreciate in – No prior MI – Ongoing chest pain – Chest pain within past 2 hours

• CP admission can be safely reduced by 57% • Validated extensively (class1)

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Myocardial Perfusion Imaging in the ER

Normal: safely discharge home

Abnormal: admission and coronary angiogram

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Diagnostic accuracy of SPECT imaging in ER

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Clinical Nuclear Cardiology: State of the Art and Future Directions (Fourth Edition (2010)


INCREMENTAL DIAGNOSTIC VALUE • Studies found that in a multivariate analysis, abnormal MPI was the most important independent predictor of MI or revascularization • Acute MPI added significant incremental diagnostic value after consideration of demographic, clinical, and ECG variables

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J Am Coll Cardiol 31:1011 –1017, 1998.)


Issues related to MPI imaging in the ER • Prior history of CAD • Limitation of imaging resolution – At least 3 % to 4 % LV ischemia for detection – In one study , 12 of 35 patients had normal REST MPI, and ultimately diagnosed wit CAD

• Logistic in operation – Isotopes availability , experience, technical issue to offer 24h/day service

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Prior history of CAD

Rest SPECT in the ER

Previous SPECT

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Guidelines for the Use of Acute Rest Myocardial Perfusion Imaging in the Emergency Department

Indication

Test

Class

Level of Evidence

Assessment of myocardial risk in possible ACS patients

Rest MPI

I

A

Same-day rest/stress perfusion imaging

I

B

Rest MPI

III

C

Nondiagnostic ECG and initial serum markers, if available

Diagnosis of CAD in possible ACS

Nondiagnostic ECG and negative serum markers or normal resting scan

Routine imaging of patients with myocardial ischemia/necrosis already documented clinically, by ECG and serum markers

Nucl Cardiol, 9 (2002), pp. 246–250


Stress MPI • Normal rest MPI confers an excellent short-term prognosis • Rest MPI only is inadequate – Normal MPI may still have unstable angina or critical CAD

• Patients with chest pain and negative rest MPI can safely undergo stress MPI in ED or can be discharge home. •

The accuracy of stress MPI has been established over last 2 decades

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•Diagnosis

Role of MPI in CAD

 Chest pain

•Risk stratification

 Post MI or before major vascular surgery

•Assessment of Therapy  Post PCI or CABG

•Assessment of myocardial viability  Before revascularization

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Pooled diagnostic accuracy of (SPECT and PET) to detect coronary artery disease

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Eur J Nucl Med Mol Imaging 2006;33:93–104


Resting Echocardiography • Regional wall motion abnormalities detected by echo Excellent evidence of CAD in patient with chest pain • In high risk patients with chest pain abnormal wall motion by resting echo – Sensitivity : 94% – Specificity:57% • PPV – High risk patients: 98% – Low risk patients: only 31%

Sabia et al two D- Ecocardiography in the ER, Circulation 1991;84:185-192 19


ACCF/ASE/ACEP appropriateness criteria for TTE in ACP • ACP with suspected ischemia Nondiagnostic laboratory markers or ECG • Evaluation of suspected complications of myocardial ischemia or MI – – – – –

MR VSD Free wall ruptured /tamponade RV involvement Thrombus

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ACCF/ASE/ACEP/.. Appropriateness criteria for TTE and TEE ,J am coll cardiol. 207


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Stress Echocardiography • Stress echo depends upon imaging endocardial borders and wall motion and thickening • Decreased wall motion and thickness is highly suggestive of CAD • Diagnostic Accuracy: – Sensitivity: 79% t0 85% – Specificity 72%and 87% • Normal exercise and normal stress confers excellent prognosis 22


Resting and Stress Echocardiography • Advantages – Convenience, availability, portability – Rest and stress echo can be used to asses CP patients and

identifying low and high risk patients • Limitations

– Need experienced technicians and cardiologists – Poor image quality – In patients with CAD with wall motion abnormalities, it may be very difficult to determine the age of WMA

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Stress CMR • Patients presented with ACS and no angiographic evidence of CAD • In low risk patients with suspected ACS, as alternative test for early discharge the patients • Patients with established Acute MI to assess viability • After Acute MI for risk stratification – EF – Extent of scar – LV thrombus – RV involvement 24


Adenosine Stress Cardiac MR Normal Myocardium contrast injection

Infarcted Myocardium

Ischemic Myocardium < 1 min First-Pass

> 5 min Delayed Enhancement

time 25


Positive Adenosine CMR Stress

Rest 26


Dobutamine Stress MRI Rest

Stress 27


Comprehensive MRI Assessment of The CAD

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CMR After Acute MI for risk stratification

Kim RJ et al. CMR in Patients With Chest Pain, Elevated Cardiac Enzymes, and Non-Obstructed Coronary Arteries, Rev Esp Cardiol 2009;62: 976-83

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Normal Invasive Coronary angiogram 80 Patients with acute chest pain, abnormal cardiac enzymes, and abnormal wall motion

Acute myocarditis (63%)

Acute MI (15%

Takotsubo CMP (11%)

4% pericarditis 4% no Diagnosis

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Rev Esp Cardiol 2009;62: 976-83


Coronary CTA  Coronary CTA is the fastest evolving technology  High spatial resolution, fast acquisition, and widespread availability  CTA assess anatomy, function and possible perfusion  Several meta-analysis studies , the NPV of CTA is 97% close to 100 %  Normal CTA excludes obstructive CAD  CTA has several important limitations

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CTA Limitations

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Frequency of Ischemia in vessels with 50% stenosis by CTA

Very poor negative predictive value

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23 year-old male with chest pain, elevated cardiac enzymes, and abnormal wall motion

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Coronary CTA Reporting

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Conclusion • Functional imaging modalities predict myocardial ischemia and its hemodynamic significance. • Acute MPI is likely to continue to have a significant role in the acute evaluation of ED chest pain patients. • Resting and stress echocardiography assess the LV function, functional significance of CAD, and predict prognosis • CMR imaging is emerging as a versatile diagnostic tool for the management of the patient with suspected or established ACS. • Anatomical imaging does not reliably predict ischemia or hemodynamic significance.


Thank You 37


Comparison between CTA and acute rest myocardial perfusion imaging

Availability

++++

++++

Imaging time

Seconds

Minutes

Total patient preparation

10–20 min

5 min

Processing /interpretation

10–30 min

10–20 min

Radiation

1–20 mSv

4 mSv

Ancillary data obtained

Lungs, aorta

LVEF

Incidental findings

Common

AHA/ACC recommendations Class

IIA

IA

AHA/ACC appropriateness criteria

7

7

Rare

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Suggested Diagnostic Strategy for acute chest pain ER • Acute coronary syndrome – Cath lab, in less than 90 min

• Unstable angina – Cath lab within 24 hours

• Suspected ACS ( TIMI score more than 2) – Nuclear Imaging , R/O ischemia

• Suspected CAD (TIMI Score less than 2) – Coronary CTA

• Non-Cardiac chest pain – CXR,VQ scan, other test to established Diagnosis

Cardiac CT in the emergency department: Convincing evidence, but cautious Implementation. J Nucl Cardiol 2011;18:331–41.

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Cardiac CT in the emergency department: Convincing evidence, but cautious Implementation. J Nucl Cardiol 2011;18:331â&#x20AC;&#x201C;41.

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Coronary CTA Degree of coronary stenosis 0

40%

MILD Discharge from ED and OP consult with Cardiologist

70%

Moderate Stress MPI Or Cath withFFR

70%- 100%

Severe Cath Lab

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False negative SPECT 42


Nondiagnostic SPECT

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Summary • Anatomical and functional imaging are very accurate and should guide the patient management accurately • In many situation both functional and anatomical imaging are complementary • Every patient should be evaluated for pretest probability • Selection of the test should be based upon – Patients factors – Recognizing each test strength and limitations – Availability

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SHA24/061006  

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