Final answer:
Cardiac troponin shows the longest elevation after a myocardial infarction (MI), staying elevated for up to 7-14 days or more, making it a more specific indicator of cardiac damage over time compared to CK-MB and myoglobin.
Step-by-step explanation:
After a Myocardial Infarction (MI), the enzyme that exhibits the longest elevation is cardiac troponin. While other biomarkers like creatine kinase MB (CK-MB) and myoglobin rise and fall relatively quickly after an MI, cardiac troponin levels can remain elevated for a considerably longer period, which can be up to 7-14 days or more. CK-MB typically maintains higher concentrations in the plasma for 1-2 days post-MI, and myoglobin, though it rises very early after an MI, also declines rapidly.
In contrast, lactate dehydrogenase (LDH) is another enzyme that does show prolonged elevation post-MI, with peak levels lasting for about 6 days. However, troponin is the more specific and reliable marker for cardiac damage over an extended period post-MI.