A 62-year-old man had a large inferior myocardial infarction 8 months ago. He now has exertional dyspnea, and ECG shows persistent ST segment elevation in the inferior leads. Chest imaging shows an abnormal bulge of the left ventricle that moves paradoxically. The most feared complication of this lesion differs from early free wall rupture because the aneurysmal wall:
- A Is composed of dense fibrous scar resistant to rupture ✓
- B Contains viable stunned myocytes
- C Is covered by intact pericardium preventing hemorrhage
- D Has hypertrophied smooth muscle providing tensile strength
Correct answer: A. Is composed of dense fibrous scar resistant to rupture
Explanation
By 8 months the aneurysm wall consists of dense collagenous scar, so although it bulges paradoxically and predisposes to mural thrombus, arrhythmia, and heart failure, it rarely ruptures. Free wall rupture occurs days after infarction when softened coagulation necrotic muscle is weakened by neutrophil enzymes before scar formation. Pericardial coverage alone does not explain the difference; the fibrous wall does.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
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