A biomarker (biological marker) is a measurable substance, molecule, or characteristic that indicates the presence, severity, or progression of a disease, or the body’s response to a treatment. In cardiac medicine, biomarkers are blood tests that provide objective information about heart function, damage, or risk that would otherwise require more invasive investigation.
Troponin (troponin I and troponin T) is the cornerstone cardiac biomarker: these proteins are released by damaged heart muscle cells and detected in the blood. High-sensitivity troponin assays can detect even very small amounts of myocardial injury, allowing heart attack to be confirmed or excluded within 1 to 3 hours of presentation. NT-proBNP and BNP are natriuretic peptides released by cardiac muscle cells under stretch or pressure overload; elevated levels diagnose and stage heart failure, monitor response to treatment, and make heart failure very unlikely when normal in a breathless patient.
Other important cardiac biomarkers include C-reactive protein (CRP) and other inflammatory markers, which are elevated in pericarditis, myocarditis, and acute coronary artery disease events. D-dimer, a marker of clot breakdown, is used to exclude pulmonary embolism in lower-risk patients: a negative D-dimer effectively rules it out, while a positive result prompts further imaging.
For cardiac arrest survivors, serial troponin measurements confirm whether a heart attack caused the arrest, while NT-proBNP helps characterise heart function during recovery. Emerging biomarkers such as neuron-specific enolase (NSE) and S100B protein are being investigated as prognostic indicators of neurological outcome after cardiac arrest, though neither is used routinely in clinical practice.
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