Which cardiac enzyme is most likely to be elevated in a patient with an MI?

The elevation of troponin levels is the hallmark indicator for myocardial infarction (MI) in clinical settings. Troponin is a protein complex found in cardiac muscle fibers that regulates muscle contraction. When damage occurs to the heart muscle, such as during an MI, troponin is released into the bloodstream. It is highly sensitive and specific to cardiac injury, making it a reliable biomarker for the diagnosis of MI.

In the context of detecting an MI, troponin I and troponin T are the most commonly measured forms, with their levels typically rising within a few hours after the onset of chest pain and remaining elevated for several days, which helps in assessing both the timing of the myocardial injury and the degree of myocardial damage.

Other cardiac enzymes, such as creatine kinase, particularly its MB isoform, may also rise after an MI but are not as specific to cardiac injury and can be elevated in other conditions affecting muscle. B-type natriuretic peptide is more closely associated with heart failure than with acute myocardial infarction, and lactic acid levels may elevate in cases of inadequate oxygen supply, but it is not a specific marker for myocardial injury. Therefore, troponin is the preferred and most definitive enzyme for diagnosing an MI