Which biomarker rises earliest after myocardial infarction?

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

Answer: (D)

The earliest biomarker to rise after a myocardial infarction is myoglobin. It is released quickly from damaged muscle tissue, including the heart, into the bloodstream within about 1 to 3 hours after injury and peaks around 6 to 9 hours, then returns to baseline within roughly a day. This makes it the first detectable marker among the options.

Troponin begins to rise a few hours later (roughly 3 to 4 hours) and remains elevated for days, while CK-MB also rises after a few hours (about 4 to 6 hours) and returns to baseline within 2 to 3 days. BNP is a marker of ventricular strain and heart failure rather than an acute injury marker, so it does not reflect the earliest onset of myocardial injury.

Keep in mind that myoglobin’s lack of cardiac specificity means it’s not used alone to diagnose MI, but its rapid rise explains why it’s the earliest marker to appear.