Clinical Laboratory - Chemical Pathology and Immunology

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Acute Coronary Syndromes

Tests Relevant to the Diagnosis of Acute Coronary Syndromes, CV and stroke risk, and CHF

Acute coronary syndromes: decreased coronary blood flow leads to acute coronary syndromes with myocardial ischemia that can progress to myocardial infarction. The best biomarkers for myocardial injury include:

  • Troponins (most often measured as troponin I or T: TnI or TnT) are the most specific and sensitive for cardiac injury

  • Troponin may begin to increase measurably 3 to 4 hours after the coronary event and may remain elevated for 10 to 14 days.

For acute coronary syndromes, too many tests are often ordered. One troponin test on admission will suffice, combined with the history, in nearly all cases to identify the timing of the event. Combined with symptoms of ischemia, EKG, or echocardiography, the diagnosis can be confirmed or excluded. Subsequent cardiac biomarker testing to document rise and/or fall in values consistent with an acute coronary event requires repeat of just one troponin assay at least one day later.

Cardiac biomarker testing should be used to confirm a diagnosis already suspected from patient history, physical exam, and EKG.

Cardiovascular (CV) and stroke risk: relevant risk factors include patient age (>65 years), presence of systemic hypertension, diabetes mellitus, previous myocardial infarction, other cardiovascular disease, peripheral arterial vascular disease, smoking, and previous transient ischemic attack or ischemic stroke.

Laboratory biomarkers that may aid in identifying increased risk for cardiovascular diseases include elevations in: C-reactive protein (CRP), fibrinogen, homocysteine, and serum amyloid A (SAA). Of those listed, CRP is most often used, measured as high sensitivity CRP, or hsCRP.

Congestive heart failure (CHF): the B-type natriuretic peptide, or BNP, is elevated with heart failure. (Yes, there is atrial natriuretic peptide that increases with left atrial distention from left heart failure, but a variety of such peptides are produced, and the one named brain-type natriuretic peptide is a better measurement. The term brain is confusing in the context of cardiac malfunction, so the term is obfuscated by using "B-type"). An elevated BNP suggests increased risk for congestive heart failure.

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