What cardiac marker is typically used to indicate a myocardial infarction?

Troponin I is the preferred cardiac marker for indicating a myocardial infarction because it is highly specific to cardiac tissue. When there is damage to the heart muscle, such as during a myocardial infarction, troponin I is released into the bloodstream. Elevated levels of troponin I can be detected as early as 3 to 4 hours after the onset of chest pain and can remain elevated for up to two weeks, making it a reliable marker for diagnosing recent myocardial injury.

In contrast, while Creatine Kinase (CK) is also a marker for cardiac injury, it is not as specific as troponin I, as it can be elevated with other muscle injuries as well. B-type Natriuretic Peptide (BNP) is primarily used to assess heart failure rather than myocardial infarction. Myoglobin may rise early after myocardial injury but is not specific for cardiac events, as it can also be released due to skeletal muscle injury. Therefore, the specificity and sensitivity of troponin I make it the most reliable choice among the cardiac markers for diagnosing myocardial infarction.