Investigations For Suspected Cardiac Chest Pain

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Investigations For Suspected Cardiac Chest Pain

• Dr Rajan Sharma
• Consultant Cardiologist
• Ealing Hospital

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Diagnostic Tools

• Functional
• Exercise ECG
• Stress Echo
• Myocardial Perfusion Scanning
• Stress CMR

• Anatomy
• Coronary Angiography
• Cardiac CT
• CMR Angiography
• Carotid Ultrasound

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General Principles

• The interpretation of any cardiac investigation
  very heavily dependent on history and clinical
  status
• All of the available tests are cost effective if
  selected properly
• In NW London all of these tests are available
• For all investigations, the operator is as
  important as the test itself

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Indications For Functional Test

• Diagnosis of CAD in pts with CP
• Functional significance of coronary stenosis
  targeted revascularisation
• Risk stratification
• before non-cardiac Surgery
• early after MI
• in pts with stable angina
• prior to ICD
• Detection of viability
• Valve Disease

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The Ischaemic Cascade
Chest pain
ECG Changes
Systolic Dysfunction
Regional Wall Motion Abnormality
Temporal sequence of ischaemic events
Diastolic Dysfunction
Metabolic alteration
Perfusion defect
Rest
Stress
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Accuracy of Cardiac Imaging Techniques for
Ischaemia Dx
Bax JJ et al. JACC 2002301451-60
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Exercise Testing

• Cardiac workload gradually increased by walking
  up an incline
• ECG, heart rate and blood pressure monitored
• Development of symptoms, new ECG changes or
  abnormal BP response at a low workload indicates
  coronary disease
• Cheap and safe and many nurse led RACP clinics
  now set up
• Limitations if resting ECG abnormal or patient
  has poor exercise tolerance

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Interpretation

• Normal Exercise gt 6 minutes with no symptoms or
  significant ECG changes and good haemodynamic
  response (gt 85 THR)
• Positive Chest pain, significant ECG changes or
  drop in BP at early change
• Inconclusive Inability to achieve at least 85
  THR, short exercise time, non specific ECG
  changes at high workload

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41 year old male with sharp pains in chest at
rest. Father had MI aged 72.
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12 mins 2 secs of Full Bruce Protocol. 94 THR
achieved.
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46 male with chest tightness on effort. Diabetic
with raised cholesterol.
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Test stopped at 1 minute 30 secs with chest
tightness.
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Stress Echocardiography

• Safe with few contraindications
• Procedure takes 40-60 minutes
• Dobutamine, dipyridamole, exercise, pacing can be
  used as stress agent
• Deterioration in wall motion signifies ischaemia
• Accuracy from research studies not always
  reproduced clinically
• Reproducibility improved with better frame rates,
  digital acquisition and recognised need for
  specialist training

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Procedure
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Semi Quantitative Assessment

• 1 normal
• 2 hypokinetic
• 3 akinetic
• 4 dyskinetic
• WMSI total score/
• total no. segments analysed

The test is considered positive if there is a
deterioration of wall motion in normal or
hypokinetic segments at rest compared with stress.
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Low
Rest
Peak
Recovery
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LIMITATIONS

Poor endocardial border definition
Complex fibre architecture


Semi quantitative technique

• Dobutamine non physiological
• Limited scan planes with echo

Streeter DD 1979
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Contrast Agents
Improved endocardial border definition improves
accuracy and reproducibility of technique. Should
be used when 2 or more LV segments not visualised
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Myocardial Viability
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Motion of scar tissue and TDI
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Myocardial Contrast Echo
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Myocardial Perfusion Imaging

• Intravenous administration of radioisotope
  followed by imaging of radioactivity with gamma
  camera
• Thallium 201, technetium-99m-sestamibi,
  technetium-99m-tetrofosmin, commonly used
  isotopes
• Stress induced by exercise, dipyridamole,
  adenosine or dobutamine
• Comparison of rest and stress images allows
  detection of ischaemia or infarction

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Interpretation

• A normal MPI very good prognostic sign
• Poor prognostic markers are gt 10 myocardium
  ischaemic, dilatation of LV cavity with stress,
  increased lung uptake of tracer during stress
• Accuracy maintained in women

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Cardiac MRI (CMR)

• Rapidly developing technique with increasing
  availability and indications
• 1 unable to tolerate scan due to claustrophobia
• No limitation with imaging planes allowing
  complete anatomical assessment of complex disease

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Cardiac MRI
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CMR for CAD

• Stress CMR
• Gadolinium enhancement for viability
• Perfusion CMR
• CMR Angiography

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Contrast Enhancement in Infarction
Ex-vivo comparison of TTC and Gd-enhanced MR
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Subendocardial MI vs Transmural MI
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Cardiac CT

• Coronary calcification usually indicates the
  presence of atherosclerosis
• A calcium score calculated from total area of
  calcium multiplied by density weighting
• Agaston Calcium Score gt 300 is significant with
  high sensitivity but moderate specificity
• Role of CT calcium score in screening
  asymptomatic patients remains controversial
• Contrast enhanced CT highly effective at
  visualising lumen of proximal two thirds of
  coronary arteries
• Requires small but significant radiation dose

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Coronary Calcification

• Although there is a positive correlation between
  the site and the amount of coronary artery
  calcium and the percent of coronary luminal
  narrowing at the same anatomic site, the relation
  is nonlinear and has large confidence limits
• The relation of arterial calcification, like that
  of angiographic coronary artery stenosis, to the
  probability of plaque rupture is unknown
• There is no known relationship between vulnerable
  plaque and coronary artery calcification
• Although radiographically detected coronary
  artery calcium can provide an estimate of total
  coronary plaque burden, due to arterial
  remodeling, calcium does not concentrate
  exclusively at sites with severe coronary artery
  stenoses

2007 ACCF/AHA Expert Consensus Document
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The Procedure

• EBCT and MDCT are fast CT techniques currently
  deployed
• Thirty to 40 adjacent axial scans usually are
  obtained.
• A calcium scoring system has been devised based
  on the X-ray attenuation coefficient, or CT
  number measured in Hounsfield units, and the area
  of calcium deposits
• A fast CT study for coronary artery calcium
  measurement is completed within 10 to 15 min,
  requiring only a few seconds of scanning time
• Coronary Calcium (Agaston) Score calculated by
  automated tracing of each coronary artery

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Coronary Artery Calcium Score And Survival
Budoff M et al. JACC 200749(18)1871-73
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Incremental Benefit of CAC Score vs Framingham
Risk
Budoff M et al. JACC 200749(18)1871-73
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Annual CVS Event Rate According To Coronary
Artery Calcium Score
Greenland P et al. JACC 200749(3)378-402
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CAC, Ethnicity and Cardiac Events
Robert D et al. NEJM 20083581336-45
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2007 ACCF/AHA Expert Consensus Document

• It may be reasonable to consider use of CAC
  measurement in intermediate risk patients (10
  20 10 yr CVS risk). This conclusion is based on
  the possibility that such patients might be
  reclassified to a higher risk status based on
  high CAC score, and subsequent patient management
  may be modified. Patients with a low CAC score
  should still be considered as intermediate risk.
• The Committee does not recommend use of CAC
  measurement in low and high CVS risk patients. In
  particular high risk patients should already be
  considered for intensive risk reduction.
• There is no clear evidence that additional
  non-invasive testing in intermediate risk
  patients with high CAC score (gt 400) will result
  in more appropriate selection of treatments.

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Coronary Angiography

• Still gold standard for coronary anatomy
• Significant side effects rare (1 in 500)
• Smaller sheaths, closure devices and radial
  access now means this is a day case procedure
• Not practical or cost effective for routine
  screening of CAD
• Investigation of choice to plan management in
  patients with high probability of CAD

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Problems

• Underestimates plaque burden
• Gives anatomical information only
• May lead to unnecessary revascularisation in
  minimally symptomatic patients with stable CAD
• In low CAD patients has small risk and not always
  cost effective

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Distribution of CAD According to Angiographic
Severity in Renal Transplant Candidates
29 N 36
36 N 45
14 N 17
21 N 27
R Sharma et al. Nephrol Dial Trans.
200520(10)2207-14
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Functional Assessment of Angiographic Stenosis

• IVUS

Pressure Wire
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Angiography underestimates atherosclerotic burden
Patients (n44) with suspected CAD and normal
angiograms
Atheroma on IVUS
No atheroma on IVUS
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Erbel R et al. Eur Heart J 1996 17 880889
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CONCLUSIONS What I Do

• For ETT if good mobility and baseline ECG normal
• If ETT normal then patient reassured
• If ETT positive for coronary angiogram
• If ETT inconclusive for functional test if
  symptoms atypical and few risk factors if
  history good and multiple risk factors for
  coronary angiogram
• If unable to ETT then for functional test
• Any positive functional test to be considered for
  coronary angiography
• Consider CT angiography if very difficult
  vascular access or unable to selectively engage
  artery

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