A 60-year-old man dies 5 days after acute myocardial infarction. At autopsy, there is a soft, yellow-tan area of myocardial necrosis surrounded by a hyperemic zone. The predominant infiltrating cell type at this stage is:
- A Neutrophils
- B Macrophages ✓
- C Lymphocytes
- D Fibroblasts
Correct answer: B. Macrophages
Explanation
During the subacute phase of MI (days 3-7), neutrophils that initially dominated (days 1-3) are replaced by macrophages that phagocytose necrotic debris and coordinate repair signalling. By day 5, the infarct zone is characteristically infiltrated predominantly by macrophages, and this is the phase of maximum myocardial softening (malacic stage), when free wall rupture and papillary muscle rupture complications are most likely. Fibroblasts and granulation tissue appear later (week 2+). Lymphocytes are not the dominant cell at day 5.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.