In a transmural myocardial infarction, the first histological change detectable on light microscopy after 4-6 hours is:
- A Coagulation necrosis with ghost cell outlines and loss of nuclei
- B Wavy myofibre change with contraction band necrosis ✓
- C Neutrophilic infiltration between cardiomyocytes
- D Granulation tissue with capillary proliferation
Correct answer: B. Wavy myofibre change with contraction band necrosis
Explanation
The earliest histological change detectable after approximately 4-6 hours of ischemia is waviness of myocyte fibres at the border of the infarct, caused by stretching of dead cells by adjacent contracting viable fibres. Contraction bands (eosinophilic transverse bands) from hypercontracted sarcomeres appear in reperfused areas or at the border zones. Coagulation necrosis with ghost cell outlines becomes evident at 12-24 hours. Neutrophilic infiltration (pyknotic nuclei, karyorrhexis) begins at 18-24 hours. Granulation tissue appears at 7-10 days.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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