A 55-year-old man dies 4 days after an anterior STEMI. Autopsy shows a transmural infarct with abundant neutrophilic infiltration, wavy fiber change, and beginning coagulation necrosis. At this stage, which complication is most feared due to enzymatic digestion of the myocardial wall?

• A Ventricular aneurysm formation
• B Papillary muscle rupture causing acute MR
• C Pericarditis (Dressler syndrome)
• D Free wall rupture and hemopericardium (cardiac tamponade) ✓

Explanation

Free wall rupture with hemopericardium and cardiac tamponade is the classic complication of the 3–5 day post-MI period. During this phase, neutrophils invade the infarct and release lysosomal proteases, metalloproteinases, and reactive oxygen species that digest the necrotic myocardial wall. This 'softening' of the infarct makes it susceptible to rupture at the weakest point, causing acute tamponade — a sudden catastrophic complication. Ventricular aneurysm forms later (weeks) from fibrous replacement. Dressler syndrome occurs at 2–10 weeks.

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

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