What is the sequence of enzyme elevation following acute myocardial infarction from earliest to latest?

• A. CK-MB -- Troponin -- Myoglobin
• B. Myoglobin -- CK-MB -- Troponin
• C. Troponin -- CK-MB -- Myoglobin
• D. CK -- Myoglobin -- Troponin

Answer: (B)

Following an acute myocardial infarction (AMI), biomarkers are released into the bloodstream reflecting the damage to cardiac tissue. The correct sequence of enzyme elevation from earliest to latest involves myoglobin, CK-MB, and then troponin.

Myoglobin is the first marker to rise following an AMI. This occurs as myoglobin is a small, oxygen-binding protein that can be found in both skeletal muscle and cardiac muscle. Within a few hours after the onset of chest pain, myoglobin levels can increase, making it a quick indicator of muscle injury. However, myoglobin is not specific to cardiac tissue, so while it may rise first, it is often not sufficient alone for a definitive diagnosis of myocardial infarction.

Following myoglobin, CK-MB (Creatine Kinase-MB) levels rise. CK-MB is more specific to cardiac tissue compared to myoglobin and typically starts elevating within 4 to 6 hours post-infarction. The rise in CK-MB levels is also useful for diagnosing reinfarction, as it returns to baseline after a period of time.

Finally, troponin, which includes troponin T and troponin I, is the most specific marker for myocardial injury and begins to elevate approximately 3