Cardiac Biomarkers

Cardiac biomarkers are blood analytes that signal myocardial injury or strain. The most important is cardiac troponin, the preferred marker of myocardial injury, complemented by the natriuretic peptides (BNP and NT-proBNP) that reflect cardiac wall stress and are used in the evaluation of heart failure.

Definition

Cardiac biomarkers are circulating proteins or peptides released by injured or stressed myocardium whose measurement is used to detect and characterise myocardial injury and cardiac dysfunction.

Scope

The topic covers cardiac troponins (including high-sensitivity assays), the natriuretic peptides, and the principle that biomarker elevation indicates injury or strain without specifying its cause. It is framed as a laboratory-medicine reference, describing what the markers represent and how they are interpreted as patterns over time, and it does not provide diagnostic thresholds or treatment guidance.

Core questions

• Why is cardiac troponin the preferred marker of myocardial injury?
• What do high-sensitivity troponin assays add, and what is the role of serial measurement?
• How do natriuretic peptides reflect cardiac wall stress?
• Why does a raised biomarker indicate injury without identifying its cause?

Key concepts

• Cardiac troponin I and T
• High-sensitivity troponin assays
• Serial sampling and rising/falling pattern
• 99th percentile upper reference limit
• Natriuretic peptides (BNP, NT-proBNP)
• Myocardial injury versus myocardial infarction
• Analytical interference (e.g., heterophile antibodies, biotin)

Mechanisms

Cardiac troponins are structural proteins of the cardiac myocyte contractile apparatus; when myocytes are injured, troponin is released into the circulation, making it a sensitive and cardiac-specific marker of myocardial injury (thygesen-2019). High-sensitivity assays detect low concentrations and resolve a rising or falling pattern on serial sampling, which helps distinguish acute from chronic injury, with the 99th-percentile upper reference limit serving as the decision reference (wu-2018). Natriuretic peptides are secreted by cardiomyocytes in response to wall stress and volume overload, so BNP and NT-proBNP rise with cardiac strain and are used in evaluating heart failure (braunwald-2008). Because many processes can injure or stress the myocardium, an elevated biomarker indicates injury or strain but not its specific cause (libby-2013).

Clinical relevance

Cardiac biomarkers are central to evaluating suspected myocardial infarction and heart failure and are interpreted together with the clinical context and serial changes. This entry explains what the markers represent and how their kinetics inform interpretation; it is a reference resource and does not provide diagnostic cut-offs or treatment guidance for any individual.

Evidence & guidelines

The use of cardiac troponin in defining myocardial injury and infarction is set out in the Fourth Universal Definition of Myocardial Infarction (thygesen-2019) and in laboratory practice recommendations (wu-2018); the role of natriuretic peptides in heart failure assessment is reviewed in the cardiology literature (braunwald-2008).

Debates

How should high-sensitivity troponin results be interpreted at very low concentrations?

High-sensitivity assays detect troponin in many people without acute events, so distinguishing chronic from acute injury relies on serial change and defined reference limits rather than a single value, and the optimal interpretive strategy remains an active methodological topic.

Seminal works

• thygesen-2019
• wu-2018

Frequently asked questions

Does a raised troponin always mean a heart attack?

No; troponin indicates myocardial injury, which has many possible causes. Diagnosing myocardial infarction requires a rising or falling pattern in an appropriate clinical context, not an isolated elevation.

What do natriuretic peptides tell us?

BNP and NT-proBNP rise with cardiac wall stress and volume overload, so they are used to support the assessment of heart failure rather than to mark cell injury.