Unreperfused MI...Characteristic Microscopic Pathology Findings

Question 1

earliest finding (not always present)

Answer 1

thin wavy myocytes (first visible at 1-3 hours)

Question 2

Thin wavy myocytes…

Answer 2

…ARE DEAD!!!

persist at periphery of infarct

Question 3

THE characteristic finding

Answer 3

coagulation necrosis

Question 4

3 components of coagulation necrosis

Answer 4

1. hypereosinophilia
2. loss of striations
3. nuclear changes
   (pyknosis–>karyorrhexis–>karyolysis–>disappearance)

Question 5

When does coagulation necrosis first become visible?

Answer 5

4-12 hours

Question 6

What follows myocyte necrosis?

Answer 6

neutrophilic infiltration (acute inflammation)

Question 7

when does neutrophilic infiltration become visible?

Answer 7

6-12 hours

Question 8

What is neutrophilic infiltration associated with?

Answer 8

edema and sometimes hemorrhage

Question 9

when does neutrophilic infiltration peak?

Answer 9

third day

Question 10

What has dense hypereosinophilic transverse bands of hypercontracted sarcomeres in dead myocytes?

Answer 10

contraction band necrosis

Question 11

Where can contraction band necrosis be seen?

Answer 11

periphery of infarct

Question 12

what causes contraction band necrosis?

Answer 12

influx of calcium through damaged cell membranes of irreversibly injured myocytes…causes exaggerated contraction of myofibrils

Question 13

what can sometimes be seen in viable myocytes around infarct?

Answer 13

myocytolysis

Question 14

Acute phase

Answer 14

(days 1-3)

thin wavy myocytes
coagulation necrosis
neutrophilic infiltration
contraction band necrosis
myoctolysis sometimes

Question 15

what is the early subacute phase characterized by?

Answer 15

infiltration of infarct by lymphocytes (boss), macrophages (garbage collectors), and fibroblasts (collagen engineers)

Question 16

When do the first lymphocytes arrive?

Answer 16

day 2

Question 17

when do the first macrophages arrive?

Answer 17

day 3

Question 18

when do the first fibroblasts arrive?

Answer 18

day 4

Question 19

What other cells may be present during early subacute phase?

Answer 19

eosinophils and plasma cells

Question 20

where does the infiltration process begin?

Answer 20

periphery of the unreperfused infarct, then spreads into the infarct

Question 21

Early subacute phase

Answer 21

days 4-10

Infiltration

Question 22

Late subacute phase

Answer 22

day 11-week 12

ingrowth of capillaries (angiogenesis)
proliferation of fibroblasts

Question 23

what do angiogenesis and proliferation of fibroblasts do?

Answer 23

convert tissue cleared of dead myocytes into granulation tissue

Question 24

what eventually happens to granulation tissue?

Answer 24

replaced by acellular fibrous collagen scar from fibroblasts