In a patient with acute myocardial infarction, coagulation necrosis is the predominant early histological pattern. The transition from reversible to irreversible injury occurs at approximately what time threshold in experimental models?

• A 4–6 hours of ischemia
• B 2 minutes of ischemia
• C 12–24 hours of ischemia
• D 20–40 minutes of severe ischemia ✓

Explanation

Experimental coronary ligation studies (Jennings and Reimer) established that irreversible myocardial injury (cell death) begins after approximately 20–40 minutes of severe ischemia (complete occlusion). The subendocardial zone is most vulnerable as it is the last to be perfused and most oxygen-demanding. Histological evidence of coagulation necrosis (eosinophilic cytoplasm, pyknotic or lost nuclei) is not visible on H&E until 4–12 hours after infarction, though irreversibility occurs much earlier.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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