Cardiac markers

Cardiac markers, often referred to as heart biomarkers, are substances in the blood that are released when the heart is damaged or stressed. These markers play a crucial role in the diagnosis, management, and prognostication of various heart diseases, most notably myocardial infarction (heart attack). Though historically many of these markers were enzymes, leading to the term "cardiac enzymes," modern medicine recognizes a broader array of non-enzyme markers, making the term "cardiac markers" more appropriate.

Overview

The heart, like other organs, contains proteins and other substances specific to it. When cardiac cells are injured, these substances can leak into the bloodstream, serving as indicators or markers of cardiac injury. The nature and concentration of these markers can give clinicians valuable insights into the type, severity, and timing of the heart event.

Types of Cardiac Markers

The following are some of the key cardiac markers and their significance:

• Troponins (cTnI and cTnT): Considered the gold standard for diagnosing myocardial infarction, troponins are proteins found in cardiac muscle cells. Their levels rise within hours of a heart attack and can remain elevated for up to two weeks. Notably, troponins are specific to the heart, unlike other markers which can be elevated in muscle injuries elsewhere in the body.
• Creatine Kinase (CK): An enzyme found in the heart, brain, and skeletal muscles. Its cardiac-specific form, CK-MB, was previously the standard for MI diagnosis before the adoption of troponins.
• Myoglobin: A protein that helps store oxygen in muscle cells, including those of the heart. It is released faster than troponin following a heart injury but is less specific, as it is also found in skeletal muscles.
• Brain Natriuretic Peptide (BNP): Released by the heart in response to stress and stretching. It is primarily used to diagnose, assess the severity, and determine the prognosis of heart failure.

Clinical Significance

Myocardial Infarction

Cardiac markers are indispensable in the diagnosis of myocardial infarction. Elevated levels of markers, especially troponins, combined with clinical symptoms and electrocardiogram (ECG) changes, can confirm the diagnosis.

Other Heart Conditions

While myocardial infarction is the most common context in which cardiac markers are discussed, other conditions can also cause elevated levels. These include:

• Heart failure
• Myocarditis (inflammation of the heart muscle)
• Cardiomyopathy (diseases of the heart muscle)
• Pericarditis (inflammation of the lining outside the heart)

Limitations and Considerations

While cardiac markers are invaluable diagnostic tools, they are not without limitations:

• Timing: Many markers take time to rise after an event. A negative result immediately after chest pain onset does not rule out a heart attack.
• Specificity: Some markers, like myoglobin, can be elevated due to non-cardiac muscle injuries.
• Interpretation: Elevated levels should be interpreted in conjunction with clinical symptoms, patient history, and other diagnostic tests.

Conclusion

Cardiac markers provide crucial information about heart health and are indispensable in the diagnosis and management of various heart conditions. Advances in medicine continue to refine our understanding of these markers and their roles in patient care.

See Also

• Electrocardiogram (ECG)
• Cardiac catheterization
• Coronary artery disease

Cardiac markers Resources
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