Which enzyme elevates first during an acute myocardial infarction?

Myoglobin is a small heme protein that is found in heart and skeletal muscles. During an acute myocardial infarction (AMI), myoglobin is one of the first markers to rise in the bloodstream. This is due to its rapid release from damaged muscle cells, making it a sensitive early indicator of myocardial injury.

Unlike other biomarkers such as CK-MB, total CK, and troponins, which may have delayed increases and can vary based on muscle mass or the timing post-infarction, myoglobin typically exhibits an elevation within 1 to 4 hours after the onset of chest pain. Therefore, it is particularly useful in the early detection of an AMI, even though it lacks the specificity of troponin for cardiac injury.

CK-MB and total CK levels rise following myoglobin, but at a slightly later time frame. Troponin, while it is very specific to cardiac muscle injury and gradually increases, also takes longer to elevate compared to myoglobin. Thus, myoglobin serves as a crucial initial biomarker in the early hours following a myocardial infarction.