Four days after an anterior STEMI treated with primary PCI, a 60-year-old man develops recurrent chest pain. Cardiac troponin I is elevated at 6 ng/mL, similar to the peak value measured 20 hours after admission. Which biomarker is most useful to distinguish acute reinfarction from the persistently elevated troponin of the recent index event?

• A Myoglobin
• B Repeat cardiac troponin T
• C Lactate dehydrogenase isoenzymes
• D CK-MB fraction ✓

Explanation

Cardiac troponins remain elevated for 7 to 14 days after myocardial injury, so a rising value cannot be interpreted reliably this early. CK-MB normalises within about 48 to 72 hours, making it the preferred marker for diagnosing perioperative infarction and early reinfarction. Myoglobin rises too quickly and lacks cardiac specificity, and LDH isoenzyme analysis is obsolete in this setting.

Reference: Braunwald's Heart Disease, 12th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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