Cardiac biomarkers are proteins or enzymes released into the bloodstream when heart muscle cells are damaged or stressed. They are measured by blood tests and used to diagnose heart attacks, monitor heart failure and assess cardiac risk.
When a doctor suspects a cardiac event, they will typically order a panel of blood tests alongside an ECG. Understanding what each marker measures helps you make sense of results and have a more informed conversation with your care team.
Troponin (troponin I and troponin T)
Troponin is the most important cardiac biomarker in use today. It is a protein found in heart muscle cells — when those cells are damaged (as in a heart attack), troponin leaks into the bloodstream and levels rise sharply within 3–6 hours of the event.
Highly sensitive troponin (hs-cTnI or hs-cTnT) assays can detect tiny elevations earlier — often within 1–2 hours. A normal troponin at 0 and 3 hours after chest pain onset makes a heart attack very unlikely.
Importantly, troponin can also rise in conditions other than heart attacks — pulmonary embolism, myocarditis, severe infections and kidney failure can all cause modest elevations. Context and trend matter: a rising and falling troponin strongly suggests an acute cardiac event; a mildly elevated but stable level may reflect a different cause.
BNP and NT-proBNP (brain natriuretic peptide)
BNP and its precursor NT-proBNP are hormones produced by the heart in response to wall stress — when the heart is stretched by increased volume or pressure, as happens in heart failure.
Elevated BNP/NT-proBNP is the primary blood marker for heart failure diagnosis and is also used to monitor response to treatment. Very high levels correlate with more severe disease. They can also rise in atrial fibrillation, pulmonary hypertension and kidney disease.
| NT-proBNP level | Interpretation |
|---|---|
| Below 125 pg/mL (under 75) | Heart failure unlikely |
| 125–900 pg/mL | Heart failure possible — requires clinical assessment |
| Above 900 pg/mL | Heart failure likely in the right clinical context |
CK and CK-MB (creatine kinase)
Creatine kinase (CK) is an enzyme found in muscle cells throughout the body — not just the heart. When muscle cells are damaged, CK rises. CK-MB is the cardiac-specific fraction of creatine kinase.
CK-MB was the standard cardiac marker before troponin assays became widely available. It is still used in some centres, particularly to time a heart attack (CK-MB rises and falls faster than troponin, so a peak CK-MB can indicate roughly when the event occurred) and to detect re-infarction.
D-dimer (a vascular, not cardiac, marker)
D-dimer is often ordered alongside cardiac markers when breathlessness or chest pain could indicate a pulmonary embolism (PE). It is a fibrin degradation product — raised when there is abnormal clotting. A normal D-dimer makes PE very unlikely; a raised result doesn't confirm it (false positives are common) but prompts further imaging.
Keeping cardiac results over time
For patients with established heart disease, markers like BNP/NT-proBNP are followed serially. Storing these results in Looms gives you and your cardiologist a clear trend, making it easier to identify whether treatment is reducing cardiac stress or whether disease is progressing. If you've also had an ECG as part of your cardiac workup, our guide to reading an ECG report explains the key values. Cholesterol is usually tracked alongside cardiac markers — see our cholesterol and lipid panel guide for a full breakdown.