Myocardial Infarction

Question 1

Myocardial ischemia

Answer 1

a condition of reversible inadequate blood supply to the heart due to fixed coronary stenosis, coronary vasospasm, increased myocardial demand, intraplaque hemmorhage, etc..

Question 2

Stunned myocyte

Answer 2

myocytes injured by acute ischemia, they look normal microscopically, but need time to repair before they work normally again. Caused by myocytes acumulating calcium, oxygen derived free radicals, and damage to cytoplasmic proteins and organelles. Takes time to reverse.

Question 3

What does chronic ischemia cause myocytes to do?

Answer 3

Causes myocytes to hunker down, catabolize (break down) their contractile proteins and revert to a primitive state limited to survival functions.

Question 4

Myocardial infarction

Answer 4

irreversible necrosis of heart muscles due to prolonged ischemia greater than 20 minutes.

Question 5

What exactly is chronic ischemia

Answer 5

Repeated episodes of ischemia too brief to cause infarction or inadequate perfusion that is low enough to injure but not to kill.

Question 6

90% of MIs due to what

Answer 6

coronary atherosclerosis

Question 7

0-12 hours, what phase and what findings for unreperfused myocardial infarction.

Answer 7

Acute phase, no findings

Question 8

12-24 hours, what phase and what findings

Answer 8

Acute, progressive pallor

Question 9

2-3 days

Answer 9

Acute, Yellow and softened

Question 10

4-7 days

Answer 10

Subacute, Red border

Question 11

1-6 weeks

Answer 11

Gradual replacement of yellow infarct by red granulation tissue

Question 12

6-12 weeks

Answer 12

Gradual white scarring

Question 13

Microscopic pathology of classical unreperfused acute MI

Answer 13

1-3 days: thin wavy myocytes
Coagulation necrosis, contraction band necrosis,
Day 2- lymphocyte proliferation
Day 3- Macrophages
Day 4- fibroblasts
Day 11-12: angiogenesis and fibroblast proliferation.

Question 14

Contraction band necrosis

Answer 14

seen in the periphery of an infarct, results from the influx of calcium through damaged cell membranes.

Question 15

Acute phase of reperfused MI

Answer 15

1-3 days, contraction band necrosis and hemorrhage

Question 16

Earliest subacute phase of Reperfused MI

Answer 16

Lymphocytes presesnt, granulation tissue formed, then collagen

Question 17

No-reflow phenomenon and hemorrhage

Answer 17

Examples of reperfusion injury. Basically in a reperfusion injury, cell membranes that have been rendered permeable by ischemia may allow excess calcium into the cells with reperfusion. Also, oxygen brought in by the restored blood flow may give rise to injurious oxygen free radicals. May also bring in overzealous inflammaotory cells.

Question 18

Ischemic Preconditioning

Answer 18

Brief episodes of ischemia render the myocytes less vulnerable to infarct due to the induction of protective proteins

Question 19

Transmural infarction

Answer 19

Full thickening of the heart wall. Often associated with occlusive thrombosis superimposed on an atherosclerotic plaque.

Question 20

Coagulation necrosis components

Answer 20

hypereosinophilia, loss of striations, nuclear changes (pyknosis etc…) Coag necrosis is the major characteristic of unreperfused MI

Question 21

Contraction band necrosis

Answer 21

hypereosinophilic bands of hypercontracted sarcomeres. A result of calcium influx through damaged cell membranes (hence the contraction band necrosis. Usually seen along the periphery. Seen often with reperfusion injury

Question 22

Reperfusion MI occurs when:

Answer 22

When blood flow to ischemic cardiac myocytes is restored via angioplasty, thrombolytic therapy, coronary bypass, etc… You can save cells if you do it early enough. If not, it alters the appearnace and thats all

Question 23

Reperfusion causes them to be

Answer 23

smaller, patchier, with hemorrhage

Question 24

No-reflow phenomenon

Answer 24

seen in reperfusion when an attempt to restore blood flow to an ischemic area fails because of some obstruction casued by capillary swelling, thrombus, embolisms, etc…

Question 25

DO reperfused MIs look older or younger than unreperfused?

Answer 25

Older. At one day they look like 2 day old unreps, 2 they look 4, 4 they look 6, etc…

Question 26

Late subacute phase of reperfuse MI looks like what>?

Answer 26

Patches of preserved myocardium are interspersed with scar.