Step 1 Study Topics: Pathological Changes After A Myocardial Infarction


This page is dedicated to compiling Step 1 study notes for the topic of pathological changes after a myocardial infarction. This page is likely disorganized as it was made in haste.


What will be seen on the light microscope depends upon how long after th myocardial infarction tissue is analyzed under the light microscope:

  • 0-4 hours: no visible changes will be obvious
  • 4-12 hours: Wavy fibers and narrow, elongated myocytes
  • 12-24 hours: There will bey myocyte hypereosinophilia with shrunken (pyknotic) nuclei
  • 1-3 days: Coagulation necrosis will be evident (marked by the loss of nuclei and striations). There will be prominent infiltration of neutrophils. 
  • 3-7 days: Dead neutrophils will be disintegrating (as well as dead myofibers). Macrophage infiltration will begin at the borders of the infarction. 
  • 7-10 days: there will be evident and robust phagocytosis of dead cells by the macrophages. The beginning of granulation tissue will be evident at the margins. 
  • 10-14 days: well-developed (and neovascularized) granulation tissue 
  • 2 weeks-2 months: Progressive collagen deposition/scar formation 




Page Updated: 04.26.2017