TO STRESS OR NOT TO STRESS ?

Karam Paul MS, MD, MBA, FACCCommunity Heart and Vascular

Cardiac stress testing - learning objectives

►Know why to undertake a stress test ►Know who should have one ►Know how it is performed ►Understand the limitations ►Understand which to choose ►Know what to do with the result

Cardiac stress testing

Why do a stress test?

Aims of stress testing ►Elicit abnormalities not present at rest

►Estimate functional capacity

►Estimate prognosis

►Likelihood of coronary artery disease ►Extent of coronary artery disease

►Effect of treatment

Cardiac stress testing

Who should have one?

Diagnostic test

►Bayes’ Theorem

►Consider the ‘pre-test risk’

►Sensitivity & specificity of the test

►Post-test probability of CAD ►Diagnostic power of EST is maximal when the pre-test probability is intermediate.

Risk assessment ►Pre-existing coronary artery disease

►Diabetes

►Hypertension

►Smoking history

►Family history ►Renal disease

Consider other risk factors

Pre-existing coronary artery disease ►Diabetes ►Hypertension ►Hyperlipidemia ►Smoking history ►Family history ►Renal disease

Consider other risk factors

►Pre-existing coronary artery disease

►Diabetes ►Hypertension ►Hyperlipidemia ►Smoking history ►Family history ►Renal disease

Valvular heart disease

Rhythm disorders

Contraindications

Cardiac Stress Testing

How is it done?

Exercise protocol

Positive!

Measurements ►ECG

►Exercise capacity (METS – metabolic equivalent)

►Symptoms

►Blood pressure

►Heart rate response & recovery

ECG

1mm planar ST depression

3 consecutive beats

► The normal and rapid upsloping ST segment responses are normal responses to exercise. ► Minor ST depression can occur occasionally at submaximal workloads in patients with coronary disease. ► The slow upsloping ST segment pattern often demonstrates an ischemic response in patients with known coronary disease or those with a high pretest clinical risk of coronary disease. ► Downsloping ST segment depression represents a severe ischemic response. ► ST segment elevation in an infarct territory (Q wave lead) indicates a severe wall motion abnormality and, in most cases, is not considered an ischemic response.

(From Chaitman BR: Exercise electrocardiographic stress testing. In Beller GA [ed]: Chronic Ischemic Heart Disease. In Braunwald E [series ed]: Atlas of Heart Diseases. Vol 5. Chronic Ischemic Heart Disease. Philadelphia, Current Medicine, 1995, pp 2.1-2.30

T wave changes

► Influenced by: Body position Respiration Hyperventilation Drug Rx Myocardial ischemia Necrosis

► Pseudonormalisation: Usually non-diagnostic Consider ancillary imaging

METs

Heart rate response

►Peak HR > 85% of maximal predicted for age

►HR recovery >12 bpm (erect)

►HR recovery >18 bpm (supine)

Heart rate response

Prognostic value of stress testing

Parameters associated with adverse prognosis or multi-vessel disease

► Duration of symptom-limiting exercise <5 METs ► Failure to increase sBP ≥120mmHg, or a sustained decreased ≥ 10mmHg, or below rest levels, during progressive exercise ► ST segment depression ≥2mm, downsloping ST segment, starting at <5 METs, involving ≥5 leads, persisting ≥5 min into recovery ► Exercise-induced ST segment elevation (aVR excluded) ► Angina pectoris at low exercise workloads ► Reproducible sustained (>30 sec) or symptomatic ventricular tachycardia

Limitations of treadmill stress test

► Non-diagnostic ECG changes ► False positives/false negatives ► Women – false positives ► Elderly – more sensitive/less specific ► Diabetics – autonomic dysfunction ► Hypertension ► Inability to exercise ► Drugs – digoxin; anti-anginals

Non-coronary causes of ST segment depression

► Anemia ► Cardiomyopathy ► Digoxin ► Glucose load ► Hyperventilation ► Hypokalemia ► Intraventricular conduction disturbance ► Mitral valve prolapse ► Pre-excitation syndrome ► Severe aortic stenosis ► Severe hypertension ► Severe hypoxia ► Severe volume overload (aortic or mitral regurgitation) ► Sudden excessive exercise ► Supraventricular tachycardia's

Limitations of treadmill stress test

Sensitivity 68% Specificity 77%

Ancillary techniques to enhance content

Echocardiography Radionuclide imaging

Stress echocardiography

Stress echocardiography Compares pre & post: Regional contractility Overall systolic function Volumes Pressure gradients Filling pressures Pulmonary pressures Valvular function

Dobutamine stress echo

Stress echo - limitations

Factors which effect image quality:

Body habitus Lung disease Breast implants

Normal stress echocardiogram

Case 1

►54 year old bank project manager ►Exertional chest pain & dyspnea ►Ex-smoker ►TC = 6.7mmol/L ►Stress ECG – 2mm ST segment depression in 5 leads

Stress echocardiogram

Coronary angiogram

Case 2

►62 year old female

►Chest pain & dyspnea

►Treadmill exercise test – non-diagnostic sub-maximal Hypertension No ECG changes

Case 2

►Exercised 7½ minutes (9.4 METS)

►No chest pain

►ECG changes

Case 2

Case 2

Case 3

►24 year old female engineer ►Exertional dyspnea

►Palpitations

Case 3

Inducible dyspnea ►ECG partial right bundle branch block no ischemic changes

Case 3

Case 3

Case 3

Case 4

►43 year old male - airline catering ►Chest pain

►Dyspnea

Case 4

►Inducible dyspnea ►Non-specific T wave changes ►No ST segment shift ►Global deterioration in left ventricular function

Case 4

Case 4

Case 4

Nuclear SPECT imaging ►Radio-tracer injection ►Isotopes: Thallium-201 Technetium 99m (sestamibi)

►Myocardial uptake ►Photon emission captured by gamma camera ►Rest & redistribution phases ►Pharmacologic protocols available ►Digital presentation

Nuclear SPECT imaging

Nuclear SPECT imaging

Nuclear SPECT imaging

Nuclear SPECT imaging

Reversible inferior wall defect

Milder reversible inferior wall defect

Limitations of nuclear SPECT imaging

►Time-consuming

►Artifacts ►Balanced ischemia ►Radiation

Limitations of nuclear SPECT imaging

Normal apical thinning.

Limitations of nuclear SPECT imaging

A. Breast attenuation B. Anterior ischemia

Limitations of nuclear SPECT imaging

Limitations of nuclear SPECT imaging

►Risk of iatrogenic malignancy

►Linear no-threshold model ►Consider: age gender background

Limitations of nuclear SPECT imaging

Einstein, A. J. et al. Circulation 2007;116:1290-1305

MRI cardiac stress test

Useful for: ►Patients unable to exercise ►ECG uninterpretable ►Unsuitable for DSE

And…. ►No radiation

But… ►Not currently available

Question ►45 year old diabetic man

►Anterior chest discomfort with exertion ►Exercised for 2 mins 30 secs (4.6 METs) ►95% maximal predicted heart rate

►Mild chest pain

►BP increased from baseline to 180/80mmHg

►1mm ST depression in leads II, III, aVF, V4-6

Which is true?

1. Pre-test risk is intermediate 2. Post-test probability for cardiac events is high 3. The ECG changes are non-diagnostic 4. The ECG changes are false-positive in the setting of hypertension 5. Chest pain is not a useful symptom in diabetics

Answer

1. Pre-test risk is intermediate 2. Post-test probability for cardiac events is high 3. The ECG changes are non-diagnostic 4. The ECG changes are false-positive in the setting of hypertension 5. Chest pain is not a useful symptom in diabetics

Remember…

Remember…

Parameters associated with adverse prognosis or multi-vessel disease

► Duration of symptom-limiting exercise <5 METs ► Failure to increase sBP ≥120mmHg, or a sustained decreased ≥ 10mmHg, or below rest levels, during progressive exercise ► ST segment depression ≥2mm, downsloping ST segment, starting at <5 METs, involving ≥5 leads, persisting ≥5 min into recovery ► Exercise-induced ST segment elevation (aVR excluded) ► Angina pectoris at low exercise workloads ► Reproducible sustained (>30 sec) or symptomatic ventricular tachycardia

When ordering a stress test consider…

►Pre-test risk of disease

►Sensitivity & specificity of the test

►Value of supplementary data

►AND JUST ONE MORE TIP……..

MRI cardiac stress test

Cardiac stress testing

So….which one to choose?

What to do with the result?

►Remember Bayes’ theorem

►Consider the pre-test risk

►Be aware of the sensitivity & specificity of the test

►Apply the post test probability

CT Calcium score

►Correlates with presence & extent of CAD ►Strong negative predictive value

►Cannot predict functional significance

►Higher scores can predict events

►Recommended for asymptomatic with intermediate risk

CT Calcium score

Calcification of the left anterior descending coronary artery (large arrow) and left circumflex coronary artery (small arrow).

CT Calcium score

Score description RR 0 nil 1 – 99 mild 1.9 100 – 399 moderate 4.3 400 – 999 severe 7.2 >1000 extensive 10.8

CT Calcium score

► Indicated – asymptomatic with intermediate risk

► Not for low risk/population screening ► High risk – use current guidelines

► Do not reduce Rx if intermediate risk & ‘0’ score

CT coronary angiography

►2-dimensional & 3-dimensional reconstructions

►Relies on slow, regular heart rate

►High negative predictive value (‘rule out’ ability)

CT coronary angiography - limitations

►Lower positive predictive value (over-estimation tendency)

►Grading of stenosis limited

►Does not evaluate functional significance

►Radiation exposure

CT coronary angiography

►Role not yet clearly defined

►Potential for those with intermediate likelihood of disease: Where stress testing not possible Stress test equivocal/uninterpretable Acute chest pain/no ECG changes/normal enzymes

►Role in anomalous anatomy

CT coronary angiography