Cardiac marker

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Cardiac markers are substances in the blood that help doctors assess heart health. They are used to diagnose and manage heart problems, especially when a patient has chest pain or suspected acute coronary syndrome, and to predict outcomes in conditions like heart failure. In the past these markers were mainly called cardiac enzymes, but not all markers are enzymes (for example, troponin is a protein, not an enzyme).

Measuring these markers helps doctors decide whether further tests, such as imaging or invasive procedures, are needed. Because blood tests are simple and inexpensive, clinicians often use biomarker testing early, especially for patients at low risk of death, to guide care.

Key markers include troponin I and troponin T. Normal values are troponin I below 0.3 ng/mL and troponin T below 0.2 ng/mL. Elevated troponin indicates heart muscle damage and is linked to prognosis. In people with mild, asymptomatic aortic valve stenosis and no obvious coronary disease, troponin T above about 14 pg/mL has been associated with a higher 5-year risk of ischemic heart events.

A newer marker is GPBB (glycogen phosphorylase isoenzyme BB), which comes from heart and brain tissue and rises 1–3 hours after ischemia, with levels increasing over 2–24 hours. It may help with early detection, but lab tests can take time, so the ECG and clinical assessment remain crucial in the acute phase.

CK-MB was used in the past to help diagnose heart attacks, especially with reperfusion therapy, but troponin is now the preferred marker in most guidelines. Research has explored faster testing methods, including saliva-based tests on small diagnostic chips, which in combination with ECG could help quickly indicate a heart attack in some cases.