What is the most sensitive initial test for diagnosing myocardial infarction?

The most sensitive initial test for diagnosing myocardial infarction is troponin measurement. Troponins are a group of proteins found in cardiac muscle, and when myocardial injury occurs, such as in the case of an infarction, these proteins are released into the bloodstream. Troponin levels begin to rise within a few hours after the onset of myocardial injury and can remain elevated for several days, making them highly sensitive and specific indicators of heart muscle damage.

While other tests like ECG changes can provide immediate information regarding the electrical activity of the heart, they may not always show changes in the very early stages of myocardial infarction. Creatine kinase, particularly the CK-MB isoenzyme, is less sensitive than troponin for detecting myocardial injury. Myoglobin, although it can be one of the earliest markers to rise, is not as specific for cardiac damage as troponin. Therefore, troponin is considered the gold standard for the initial evaluation of suspected myocardial infarction due to its heightened sensitivity and specificity in detecting even small degrees of cardiac injury.