Unreperfused MI...Characteristic Microscopic Pathology Findings Flashcards
earliest finding (not always present)
thin wavy myocytes (first visible at 1-3 hours)
Thin wavy myocytes…
…ARE DEAD!!!
persist at periphery of infarct
THE characteristic finding
coagulation necrosis
3 components of coagulation necrosis
- hypereosinophilia
- loss of striations
- nuclear changes
(pyknosis–>karyorrhexis–>karyolysis–>disappearance)
When does coagulation necrosis first become visible?
4-12 hours
What follows myocyte necrosis?
neutrophilic infiltration (acute inflammation)
when does neutrophilic infiltration become visible?
6-12 hours
What is neutrophilic infiltration associated with?
edema and sometimes hemorrhage
when does neutrophilic infiltration peak?
third day
What has dense hypereosinophilic transverse bands of hypercontracted sarcomeres in dead myocytes?
contraction band necrosis
Where can contraction band necrosis be seen?
periphery of infarct
what causes contraction band necrosis?
influx of calcium through damaged cell membranes of irreversibly injured myocytes…causes exaggerated contraction of myofibrils
what can sometimes be seen in viable myocytes around infarct?
myocytolysis
Acute phase
(days 1-3)
thin wavy myocytes coagulation necrosis neutrophilic infiltration contraction band necrosis myoctolysis sometimes
what is the early subacute phase characterized by?
infiltration of infarct by lymphocytes (boss), macrophages (garbage collectors), and fibroblasts (collagen engineers)
When do the first lymphocytes arrive?
day 2
when do the first macrophages arrive?
day 3
when do the first fibroblasts arrive?
day 4
What other cells may be present during early subacute phase?
eosinophils and plasma cells
where does the infiltration process begin?
periphery of the unreperfused infarct, then spreads into the infarct
Early subacute phase
days 4-10
Infiltration
Late subacute phase
day 11-week 12
ingrowth of capillaries (angiogenesis)
proliferation of fibroblasts
what do angiogenesis and proliferation of fibroblasts do?
convert tissue cleared of dead myocytes into granulation tissue
what eventually happens to granulation tissue?
replaced by acellular fibrous collagen scar from fibroblasts
