A patient treated for STEMI develops recurrent chest pain 14 hours later. Troponin I was 40 ng/mL at peak and is now being repeated. Which cardiac biomarker is most useful for diagnosing reinfarction in this setting?
- A LDH isoenzymes
- B Total creatine kinase
- C CK-MB mass ✓
- D Myoglobin
Correct answer: C. CK-MB mass
Explanation
Troponins remain elevated for 7 to 10 days after infarction, so a rising value cannot be distinguished from the index event. CK-MB returns to normal within about 48 to 72 hours, making a fresh rise of CK-MB of more than 20 percent above the previous value the standard marker for perioperative or early reinfarction. Myoglobin rises too early and lacks specificity, total CK is less specific than its MB fraction, and LDH peaks too late to be practical.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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