What is the earliest cardiac biomarker for a myocardial infarction, which elevates within 3 hours post-event?

Myoglobin is the earliest cardiac biomarker to elevate in the event of a myocardial infarction, typically within 1 to 3 hours after the onset of myocardial injury. It is a heme protein that is found in cardiac and skeletal muscle, and it serves as an oxygen-binding protein. When muscle tissue is damaged, myoglobin is released into the bloodstream, where it can be detected.

The early elevation of myoglobin makes it useful in the initial assessment of myocardial infarction, though it is important to note that it is not specific to cardiac tissue and can also rise in other conditions involving muscle injury. This characteristic allows for rapid detection following a cardiac event, leading to swift clinical decision-making.

In contrast, while troponin is a more specific marker for cardiac muscle injury and can remain elevated for longer periods, it typically takes longer (up to 4-6 hours) to rise significantly after a myocardial infarction. Creatine kinase (CK), particularly the CK-MB isoform, also provides information about myocardial injury but typically rises after myoglobin and reaches peak levels later. B-type natriuretic peptide (BNP) is primarily associated with heart failure and does not serve as an early marker for myocardial infarction.