Which statement best describes CK-MB levels in the context of myocardial injury?

• A. They rise after myocardial injury but are less specific than troponins.
• B. They are more specific than troponins.
• C. They rise only with liver injury.
• D. They are not used in myocardial injury assessment.

Answer: (C)

CK-MB is released into the blood when cardiac muscle is damaged, so its levels rise after myocardial injury. It typically starts to rise within a few hours, peaks around 24 hours, and returns to baseline in about 2–3 days. However, because CK-MB is also present in skeletal muscle, its elevation is less specific for heart injury than troponins, which are more selectively cardiac. Troponin I and T are considered more sensitive and specific for myocardial damage and stay elevated longer, which is why they’re preferred in modern practice. So the best way to describe CK-MB in this context is that it rises after myocardial injury but is less specific than troponins. It is not limited to liver injury, it is not more specific than troponins, and it is still used in myocardial injury assessment, albeit less prominently now.