What are cardiac biomarkers?
Cardiac biomarkers are substances that are released into the bloodstream when heart muscle is damaged or stressed. Measurement of these biomarkers is used to help diagnose, assess risk and manage people with the acute coronary syndrome (ACS), a potentially life-threatening condition characterised by the sudden onset of persistent pain in the chest, one or both arms, shoulders, stomach or jaw, shortness of breath, nausea, sweating and dizziness. The commonest cause of the syndrome is a heart attack (also called a myocardial infarction or MI) in which heart muscle cells die from insufficient blood flow caused by the narrowing or blockage of one of the heart's coronary arteries. However, similar symptoms may be caused by unstable angina and by other cardiac and non-cardiac conditions. Between 60% and 80% of patients taken to hospital with chest pain are found not to have had a heart attack.
Cardiac biomarker tests are requested immediately when a patient with symptoms of ACS is admitted to hospital as an emergency. Together with evidence from an electrocardiogram (ECG) and/or imaging investigations, increasing levels over time of a cardiac biomarker can help to identify those who have had a heart attack, allowing early treatment of their condition. Biomarker measurements have been studied in other roles such as monitoring the success of coronary angioplasty or ‘clot-busting’ drugs but have not been adopted in standard care.
The current cardiac biomarker test of choice is troponin. A diagnosis of myocardial infarction can be made when raised and increasing troponin levels are found together with clinical evidence of ACS and ECG or imaging evidence of reduced blood supply to heart muscle (ischaemia). Without evidence of ischaemia, possible causes of rising troponin concentrations include myocarditis (inflammation of the heart muscle), acute heart failure, an arrhythmia (abnormal heart rhythm) or pulmonary embolism (blood clot lodged in the lung). Other biomarkers are being discovered and studied but as yet none are used in standard clinical care outside of research trials.
Other biomarker tests:
- BNP (or NT-proBNP) - released from heart muscle that is stretched, so is usually used to recognise heart failure. An increased level after a heart attack implies heart muscle strain and an increased risk of recurrent events but is not measured routinely during heart attack management.
Phased out biomarkers - these tests are no longer recommended for evaluating people with suspected heart attack: