Introduction
Cardiac markers play a crucial role as diagnostic and prognostic tools in cases of acute coronary syndrome (ACS) and central chest pain. These markers are released into the bloodstream when heart muscle tissue is either damaged or subjected to significant stress.
Cardiac markers are classified into the following categories:
1. CK-MB
2. Myoglobin
3. Cardiac Troponins
According to the guidelines issued by the European Society of Cardiology (ESC) and the American College of Cardiology (ACC), cardiac troponins are central to the diagnosis of acute myocardial infarction (AMI), surpassing CK-MB and myoglobin in clinical relevance.
Let us now explore each marker in detail and discuss their clinical applications.
Cardiac Troponins
Troponins are proteins found in both skeletal and cardiac muscles. They are composed of three subunits: Troponin C (Trop C), Troponin I (Trop I), and Troponin T (Trop T).
– Troponin C is identical in both skeletal and cardiac muscles.
– Troponin I is specific to cardiac muscles. – Troponin T is specific to skeletal muscles.
Troponin I levels
Elevated 2–4 hours after myocardial injury
Peaks at 12 hours
Returns to baseline within 7 days.
CK-MB
Before the advent of troponins, CK-MB was the primary biomarker for myocardial injury. Its diagnostic criteria include:
1. Two consecutive elevated CK-MB readings.
2. A single CK-MB value that is twice the upper normal limit.
CK-MB levels
Rise 4–6 hours after the onset of symptoms
Peak at 24 hours
Return to baseline within 48–72 hours. Due to its early normalization, CK-MB is particularly useful in diagnosing reinfarctions.
Myoglobin
Although myoglobin lacks the specificity required for cardiac-related events, it has garnered interest due to its rapid release.
Myoglobin levels
Rise within 2–4 hours of myocardial injury.
Peak levels occur at 6–12 hours.
Myoglobin returns to normal within 24–36 hours.
Conclusion
Cardiac markers, especially troponins, have revolutionized the diagnosis and management of acute coronary syndromes. While CK-MB and myoglobin provide additional insight, their roles have become more adjunctive with the widespread adoption of troponins in clinical practice. A thorough understanding of the timing and specificity of these markers allows clinicians to optimize diagnosis and tailor patient care effectively.
