In acute myocardial infarction, which biomarker is typically positive in both STEMI and NSTEMI?

In acute myocardial infarction, which biomarker is typically positive in both STEMI and NSTEMI?

• A. CK-MB
• B. Myoglobin
• C. Troponin
• D. AST

Answer: (C)

Elevated cardiac troponin signals myocardial injury from infarction in both STEMI and NSTEMI. The troponin I and T proteins are highly specific to cardiac muscle, so when heart cells die, they leak into the bloodstream. This makes troponin positive regardless of whether the ECG shows ST elevation or not. Troponin rises within about 3–4 hours after onset, peaks around 24–48 hours, and remains elevated for several days (often 7–14 days or longer). This persistence helps capture both early and later presentations of myocardial infarction. Other markers are less ideal. CK-MB can be elevated in MI but is not as specific to the heart and can be influenced by skeletal muscle injury. Myoglobin rises early but is not specific to cardiac muscle, and AST is nonspecific. Because of its cardiac specificity and longer elevation window, troponin is the preferred biomarker for diagnosing MI in both STEMI and NSTEMI.

Elevated cardiac troponin signals myocardial injury from infarction in both STEMI and NSTEMI. The troponin I and T proteins are highly specific to cardiac muscle, so when heart cells die, they leak into the bloodstream. This makes troponin positive regardless of whether the ECG shows ST elevation or not.

Troponin rises within about 3–4 hours after onset, peaks around 24–48 hours, and remains elevated for several days (often 7–14 days or longer). This persistence helps capture both early and later presentations of myocardial infarction.

Other markers are less ideal. CK-MB can be elevated in MI but is not as specific to the heart and can be influenced by skeletal muscle injury. Myoglobin rises early but is not specific to cardiac muscle, and AST is nonspecific. Because of its cardiac specificity and longer elevation window, troponin is the preferred biomarker for diagnosing MI in both STEMI and NSTEMI.