Cardiac Marker: _____ is detectable within 1-2 hours after acute MI and has duration <1 day with low specificity.

Cardiac Marker: _____ is detectable within 1-2 hours after acute MI and has duration <1 day with low specificity.

• A. Myoglobin
• B. Troponin I
• C. CK-MB
• D. BNP

Answer: (A)

The question tests knowledge of how cardiac markers rise and fall after myocardial injury. Myoglobin is the earliest marker to appear, detectable within about 1–2 hours after acute MI, and it clears quickly, typically within 24 hours. Its low specificity comes from being present in both cardiac and skeletal muscle, so elevations can occur with skeletal muscle injury or other noncardiac issues. That combination—very early detectability, short duration, but low specificity—fits myoglobin best. By contrast, troponin I is highly specific for cardiac muscle and stays elevated for many days, which is great for confirming injury but not for very early detection. CK-MB rises later (hours after onset) and also persists longer, making it less consistent with the described pattern. BNP is a marker of ventricular strain and heart failure, not an acute MI marker. So the pattern described is characteristic of myoglobin.

The question tests knowledge of how cardiac markers rise and fall after myocardial injury. Myoglobin is the earliest marker to appear, detectable within about 1–2 hours after acute MI, and it clears quickly, typically within 24 hours. Its low specificity comes from being present in both cardiac and skeletal muscle, so elevations can occur with skeletal muscle injury or other noncardiac issues. That combination—very early detectability, short duration, but low specificity—fits myoglobin best.

By contrast, troponin I is highly specific for cardiac muscle and stays elevated for many days, which is great for confirming injury but not for very early detection. CK-MB rises later (hours after onset) and also persists longer, making it less consistent with the described pattern. BNP is a marker of ventricular strain and heart failure, not an acute MI marker. So the pattern described is characteristic of myoglobin.