A 52-year-old diabetic man dies 5 days after an anterior myocardial infarction. Autopsy shows a yellow-white necrotic center with a red-brown hyperemic border, and softening of the myocardium. Histologically, the infarcted area contains ghost cardiomyocytes, polymorphonuclear infiltrate being replaced by mononuclear cells, and early granulation tissue at the margins. At this time point (day 5), which is the most dangerous mechanical complication that can occur?
- A Ventricular free wall rupture with cardiac tamponade ✓
- B Right bundle branch block
- C Mural thrombus formation
- D True ventricular aneurysm formation
Explanation
Free wall rupture most commonly occurs between days 3-7 post-MI when the necrotic myocardium is at its weakest — PMNs have lysed structural proteins but fibroblastic repair (collagen deposition) has not yet provided tensile strength. Rupture causes haemopericardium and acute cardiac tamponade (Beck's triad: hypotension, muffled heart sounds, elevated JVP), which is rapidly fatal. Papillary muscle rupture (→ acute MR, days 2-7) and interventricular septum rupture (→ VSD, days 3-5) also occur in this window. True aneurysm and mural thrombus develop later (weeks). Diabetes mellitus increases free wall rupture risk.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.