Cardiac-specific troponins provide high specificity for detecting injury to cardiac myocytes. These molecules are also more sensitive than CK-MB for myocardial necrosis and therefore improve early detection of small myocardial infarctions. Although blood troponin levels increase simultaneously with CK-MB levels (about 6 hours after the onset of infarction), they remain elevated for as long as 2 weeks. As a result, troponin values cannot be used to diagnose reinfarction. New methods of detecting troponins in the blood can measure levels as low as 0.1-0.2 ng/mL.
Myoglobin is not cardiac specific, but it may be detected as early as 2 hours after myocardial necrosis starts. However, myoglobin results should be supplemented with other, more specific cardiac biomarkers, such as CK-MB or troponin.
According to the American College of Cardiology and American Heart Association guidelines, echocardiography is not routinely indicated as a first-line test for diagnosis.
Normal ECG findings or ECG results that remain unchanged from the baseline do not exclude the possibility that chest pain is ischemic in origin. Changes that may be seen during anginal episodes include the following:
Transient ST-segment elevations
Dynamic T-wave changes: inversions, normalizations, or hyperacute changes
ST depressions: may be junctional, downsloping, or horizontal
For more on the workup of ACS, read here.
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Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.
Cite this: Yasmine S. Ali. Fast Five Quiz: Test Your Knowledge of Acute Coronary Syndrome - Medscape - Apr 26, 2017.
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