A 55-year-old man dies 4 days after an anterior MI. Autopsy shows a rupture of the interventricular septum. What pathological process at 4 days explains this complication?

• A Macrophage-mediated liquefactive necrosis and granulation tissue weakening the necrotic wall ✓
• B Acute neutrophilic infiltration softening the necrotic myocardium
• C Early collagen deposition causing contracture of the infarct zone
• D Re-entrant arrhythmia causing mechanical disruption of the septum

Explanation

At 4-7 days post-MI, macrophages phagocytose dead cardiomyocytes, maximally softening the necrotic zone ('yellow softening'). This is the period of highest risk for free wall rupture, papillary muscle rupture, or ventricular septal defect. Days 1-3 have neutrophilic infiltration (acute response). Collagen deposition begins after the first week. Arrhythmias cause electrical, not mechanical disruption.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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