Cardiac Markers

Cardiac Markers

Definition: Cardiac markers are biochemical substances released into the bloodstream when the heart is damaged or stressed. They are essential for diagnosing and assessing the severity of cardiac events, particularly myocardial infarction (heart attack).

Common Cardiac Markers

• Troponin:

• Types: Troponin I (TnI) and Troponin T (TnT).
• Function: These proteins are crucial for muscle contraction in cardiac muscle. Elevated levels indicate myocardial injury and are highly specific for heart damage.
• Clinical Use: Troponin is the preferred marker for diagnosing acute coronary syndrome (ACS) due to its high sensitivity and specificity.

• Creatine Kinase-MB (CK-MB):

• Function: An isoenzyme of creatine kinase primarily found in heart muscle. Elevated levels suggest myocardial injury.
• Clinical Use: CK-MB levels rise within 4-6 hours after a heart attack, peak at 24 hours, and return to normal within 48-72 hours, making it useful for diagnosing reinfarction.

• Myoglobin:

• Function: A heme protein that carries oxygen in muscle tissues, including the heart. It is one of the first markers to rise after myocardial injury.
• Clinical Use: Myoglobin levels increase within 1-4 hours after injury but lack specificity for cardiac events since it is also released from skeletal muscle.

• B-type Natriuretic Peptide (BNP):

• Function: A hormone produced by the ventricles of the heart in response to excessive stretching of heart muscle cells. Elevated levels indicate heart failure.
• Clinical Use: BNP is used to differentiate between cardiac and non-cardiac causes of dyspnea (shortness of breath).

• C-reactive Protein (CRP):

• Function: An inflammatory marker that can indicate systemic inflammation, which may be associated with cardiovascular risk.
• Clinical Use: While not specific to cardiac events, high-sensitivity CRP (hs-CRP) can help assess risk for cardiovascular disease.

Clinical Relevance

• Diagnosis of Myocardial Infarction: Cardiac markers are essential for diagnosing heart attacks and assessing their severity.
• Risk Stratification: Levels of these markers can help determine prognosis and guide treatment decisions in patients with suspected cardiac events.
• Monitoring Treatment Efficacy: Serial measurements can be used to monitor response to therapy and detect reinfarction.

Conclusion

Cardiac markers are critical tools in the diagnosis and management of cardiovascular diseases, particularly myocardial infarction. Understanding their roles, timing of elevation, and clinical applications is essential for effective patient care.

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References

1. Thygesen K, et al. “Fourth Universal Definition of Myocardial Infarction (2018).” Journal of the American College of Cardiology. 2018; 72(18): 2231-2264. DOI: 10.1016/j.jacc.2018.08.1038
2. O’Connor JF, et al. “Creatine Kinase: A Review.” Clinical Chemistry. 1997; 43(5): 1284-1289.
3. Lentz SR. “Lactate Dehydrogenase.” Clinical Chemistry. 1996; 42(8): 1284-1289.