A 60-year-old man dies 4 days after an anteroseptal MI. Autopsy shows a soft, yellow-tan area in the anterior wall with neutrophilic infiltrate and early granulation tissue at the margins. The risk of free wall rupture is highest at which time window post-MI?
- A Within the first 6 hours (reversible injury phase)
- B 2–3 weeks post-MI (early scar formation)
- C 3–7 days post-MI (during neutrophil-mediated softening) ✓
- D 6 weeks post-MI (mature dense scar)
Correct answer: C. 3–7 days post-MI (during neutrophil-mediated softening)
Explanation
Free wall rupture is most common 3–7 days after MI when neutrophil-derived proteases and macrophage digestion maximally soften the necrotic myocardium before adequate fibrous scar replacement. This window corresponds to yellow softening (coagulative necrosis with neutrophilic infiltrate), during which the structural integrity of the ventricular wall is at its lowest. A mature fibrous scar by 6 weeks provides mechanical stability.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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