Acute MI: Coagulative necrosis of myocardial cell
This myocardial infarction is about 3 to 4 days old. There is an extensive acute inflammatory cell infiltrate and the myocardial fibers are so necrotic that the outlines of them are only barely visible. The cytoplasm is rather homogeneous, deeply eosinophilic, devoid of cross striation and there are no nuclei.Nnecrotic muscle fibres of the infarct at higher magnification. The nuclei having disappeared by karyolysis. The fibres are more deeply eosinophilic than normal fibres. The striations are still detectable focally. In the interstitial tissue there are some nuclear fragments, macrophages which have migrated into the dead muscle.
Myocardial Infarction: Coagulative Necrosis
Necrosis
NormalLine of demarcation
Myocardial infarction-line of demarcation
By 10 to 14 days from the onset the infarct is rimmed by a hyperemic zone of highly vascularized granulation tissue (line of demarcation)
This is a myocardial infarction of 1 to 2 weeks in age. Note that there are remaining normal myocardial fibers at the top. Below these fibers are many macrophages along with numerous capillaries and fibroblasts with deposition of collagen.
Myocardial Infarction: Coagulative Necrosis