Which cardiac enzymes are most useful in diagnosing an acute myocardial infarction? (Select all that apply)

A. Myoglobin is a heme protein found in cardiac and skeletal muscle that rises within 1–4 hours after myocardial injury. It is useful for early detection of acute MI due to its rapid release, though it is not specific to cardiac tissue and can increase after skeletal muscle injury. B. AST is an enzyme present in the liver, heart, and skeletal muscle, but it is nonspecific for myocardial injury. While it may elevate after an MI, it cannot reliably confirm the diagnosis. C. CRP is a nonspecific inflammatory marker that rises in response to systemic inflammation or infection, but it is not used to diagnose acute MI. D. Troponin I is highly specific and sensitive for myocardial injury, making it the gold standard biomarker for diagnosing acute MI. Levels rise 3–6 hours after infarction, peak at 12–24 hours, and remain elevated for 7–10 days, allowing for detection even if presentation is delayed. E. LDH is released from damaged cardiac tissue, with levels rising 24–48 hours post-MI and peaking at 2–3 days. While less specific than troponin, LDH can support the diagnosis, especially in late-presenting cases. F. CK-MB is an isoenzyme of creatine kinase found primarily in cardiac muscle. It rises 3–12 hours after myocardial injury, peaks at 24 hours, and returns to baseline within 48–72 hours, making it useful for detecting recurrent infarctions. G. BNP is a marker of ventricular stretch and heart failure, not myocardial necrosis. While it helps evaluate volume overload and cardiac function, it is not diagnostic for acute MI.