Morphology of Myocardial Infarction

The term myocardial infarction indicates the development of area of myocardial necrosis caused by local ischemia.


                    For the 1st 24 hrs, no changes are evident on cross examination. During next 12 – 18 hrs coagulation necrosis becomes evident on microscope examination. Heavy neutrophilic infiltrate with complete coagulation necrosis of myofibrils is evident during next 24  – 72 hrs. By day 4 – 5 infarct appears grossly as a pale, firm, fairly well defined region with a hyperemic border. Macrophages, fibroblasts and capillaries first appear at margin then slowly migrate towards centre of the lesion over next several weeks. By day 10, necrotic area is yellow, soft and sunken with periphery being replaced by granulation tissue. By 7-8 week, dense, collagenous grey scar can be seen.

MI microscopical

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