A 55-year-old man receives thrombolytic therapy 90 minutes after the onset of an anterior STEMI. He survives but dies later of another cause. At autopsy, microscopic examination of the previously infarcted anterior wall shows intensely eosinophilic transverse bands crossing hypercontracted myocytes. What does this finding indicate?
- A Coagulation necrosis of unreperfused infarction
- B Contraction band necrosis caused by reperfusion injury ✓
- C Healed scar with replacement fibrosis
- D Normal anisotropic striations of cardiac muscle
Explanation
Reestablishing blood flow into lethally injured myocardium floods the tissue with calcium, triggering hypercontraction of myofibrils and producing dense eosinophilic contraction bands across the sarcolemma. Contraction band necrosis is therefore the microscopic signature of reperfused infarction and is absent in purely occlusive, unreperfused infarcts, which show bland coagulation necrosis with wavy fibers and then neutrophils. Grossly, reperfusion also converts the infarct hemorrhagic. Healed scar would show collagen without myocytes, and normal striations are uniform and parallel, not irregular transverse bands.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
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