Exercise ECG in suspected angina: interpretation and limitations
THE CONTEXT
Exercise testing and non-invasive imaging help confirm suspected angina and stratify risk, but an exercise electrocardiogram (ECG) alone cannot reliably diagnose coronary artery disease (CAD).
Test performance and purpose
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An exercise ECG commonly uses a standard treadmill or bicycle ergometer protocol while monitoring pulse, blood pressure and the patient's general condition.
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Its principal roles are to confirm the history of exertional angina and provide an objective measure of exercise tolerance.
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The test may indicate underlying disease severity and, alongside other clinical features, identify high-risk individuals with severe coronary disease.
ST segment interpretation
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Planar or down-sloping ST segment depression of at least 1 mm is indicative of myocardial ischaemia.
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Up-sloping ST depression is less specific and may occur in normal individuals.
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False-positive exercise ECG results can occur with digoxin therapy, left ventricular hypertrophy, bundle branch block and Wolff–Parkinson–White syndrome.
Diagnostic limitations
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Exercise testing may be normal in a substantial proportion of patients with CAD.
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Reduced mobility or other non-cardiac problems may prevent adequate exercise and make the result inconclusive.
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Because of these limitations, exercise testing cannot be relied upon to diagnose CAD.