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Cardio > Ischemic Heart Disease > Flashcards

Ischemic Heart Disease Flashcards

1
Q

How long does it take cardiac myocytes deprived of their blood supply to die?

A

around 20 minutes

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2
Q

Describe the spread of death of the myocytes in a transmural (full thickness) myocardial infarction?

A

starts in the subendocardial zone, spreads in a wavefront to the subepicardial zone

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3
Q

How long does a transmural (full thickness) myocardial infarction take? What is the implication of this on therapy?

A

usually complete after around 3 hours (on handout he says 6 which is why thrombolytic therapy or angioplasty is still worth doing between 20 minutes and 6 hours after the onset of ischemia)

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4
Q

Electrocardiographic evidence of ischemia includes what two signs?

A

ST-segment depression and T-wave inversion

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5
Q

How long does it take dead myocytes to show microscopic manifestations of their death?

A

around 4 hours

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6
Q

What microscopic sign may be visible as early as a half hour after infarction?

A

dead, thin, wavy myocytes at the PERIPHERY of an infarct

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7
Q

Dead myocytes in a classic (unreperfused) myocardial infarction usually show what type of necrosis? When is this evident?

A

coagulative necrosis

Coagulation necrosis first becomes visible at 4-12 hours.

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8
Q

List the 3 components of classical MI coagulative necrosis.

A

(1) Loss of normal cytoplasmic striations
(2) Cytoplasmic hypereosinophilia
(4) Nuclear changes (pyknosis, karyorrhexis, karyolysis, loss)

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9
Q

What occurs after hypereosinophilia and coagulative necrosis? When?

A

neutrophil response to the necrosis- 6-12 hours after.

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10
Q

When does the neutrophil response peak after an acute MI?

A

around 2 days after an acute MI

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11
Q

What is a characteristic feature of 3-6 day old infarcts? Why?

A

Nuclear dust (karyorrhexic debris) due to the breakdown of neutrophils

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12
Q

What is myocytolysis?

A

the light microscopic appearance of hibernating myocytes: cytoplasmic clearing of contractile proteins that occurs in subendocardial myocytes that receive just enough blood from the lumen of the heart to survive (but not prosper)

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13
Q

What is another term for myocytolysis?

A

hibernating myocardium chronically ischemic myocytes, which have cleared cytoplasm due to catabolism of their contractile proteins and need time to regenerate their contractile proteins before they work normally again

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14
Q

Why are there lower levels of neutrophils in the subendocardial region of the infarct after an MI?

A

because the neutrophils com in from the edges (usually not including the subendocardial edge)

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15
Q

After nuclear infiltraiton, what occurs int he early subacute phase of an MI?

A

Infiltration of lymphocytes (starting at day 2), macrophages (day 3), fibroblasts (day 4) and perhaps eosinophils and plasma cells beginning at the periphery

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16
Q

What occurs in the healing phase of an MI?

A

numerous fibroblasts are present and neovascularizaiton is occurring to generate granulation tissue that is eventually changed into a fibrous scar

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17
Q

What leads of the EKG correspond to the anterior wall and LAD?

A

V1-V4

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18
Q

What leads of the EKG correspond to the inferior wall and the right coronary artery?

A

II, III, and aVF

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19
Q

What leads of the EKG correspond to the lateral wall and the left coronary artery?

A

I, aVL, V5-V6

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20
Q

How long does it take for dead cardiac muscle to show macroscopic (gross) manifestations of death?

A

about 12 hours

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21
Q

True or False: the bigger the infarct, the longer the healing time and conversion time for scar formation.

A

True!

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22
Q

What color is an acute MI during autopsy (hours old)?

A

light brown to tan

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23
Q

What color is an subacute MI during autopsy (days old)?

A

yellow

24
Q

What color is a healed MI during autopsy (weeks-years old)?

A

white

25
Q

90% of transmural infarctions are associated with what?

A

occlusive thrombosis superimposed on atherosclerotic plaque with an acute change (disruption of unstable plaque by rupture/erosion)

26
Q

What types of infarcts are becoming more common than transmural ones?

A

subendocardial infarction

27
Q

What does a subendocardial infarction involve? What does it look like?

A

Involves the inner portion of the heart wall and is more likely to be patchy and have episodic extension

28
Q

A reperfused MI has what three gross differences?

A

smaller and more patchy than it would have been with hemorrhage into the area

29
Q

What does reperfusion do to inflammation and repair?

A

accelerates it and diffuses it
(see fewer neutrophils, more macrophages, and more interstitial fibrosis)
*appears 1 day older at 2 days and 4 days older at 6 days

30
Q

What is the form of irreversible myocyte injury associated with reperfusion?

A

contraction band necrosis

31
Q

What occurs in a subacute repurfused MI?

A

Lymphocytes enter (with possible eosinophils and plasma cells), then granulation tissue and collage

32
Q

How long will it take a large infarct to be healed if it is reperfused?

A

7 weeks (from 12 if non-perfused)

33
Q

What do the patches of preserved myocardium interspersed within scar tissue make more likely?

A

make re-entrant ventricular arrhythmias more common

34
Q

What is a stunned myocyte?

A

myocytes injured by acute ischemia, which look normal microscopically, but need time to repair before they work normally again

35
Q

What is ischemic preconditioning?

A

resistance to mild-moderate ischemia due to induction of protective proteins by brief episodes of ischemia

36
Q

What is contraction band necrosis?

A

dead myocytes with dense hypereosinophilic transverse bands of hypercontracted sarcomeres, associated with reperfusion

37
Q

What is the “no reflow” phenomenon?

A

failure of relieving obstruction at the arterial level to restore blood flow, attributed to microvascular obstruction or edema

38
Q

What is the term for hemorrhage and other injurious phenomena associated with bringing oxygen and calcium to injured tissue, attributed to reactive oxygen species and metabolic effects of calcium?

A

repurfusion injury

39
Q

What is the term for ischemia that has lasted only minutes to hours or, at the most, a few days?

A

acute ischemia

40
Q

What changes occur even 1 minute into ischemia?

A

Loss of glycogen, mitochondrial swelling, cellular swelling and loss of contractility

41
Q

What event can precede irreversible injury to myocytes in an acute MI?

A

fatal arrhythmia

42
Q

True or false: acute MI is easily identifiable under microscope.

A

FALSE: As a general principle, acutely ischemic cardiac myocytes look normal under light microscopy; they are not dead yet, but they do not work.

43
Q

Why does a stunned myocardium need days to weeks to restore its contractile funciton?

A

stunned myocardium has accumulated excess calcium, oxygen-derived free radicals and damage to its cytoplasmic proteins and organelles, which takes time to reverse

44
Q

What is the definition of chronic ischemia?

A

repeated episodes of ischemia (lasting weeks, months, or years) too brief to cause infarction or inadequate perfusion that is low enough to injure the myocytes, but not low enough to kill them.

45
Q

Can myocytes recover from myocytolysis?

A

Yes. If adequate blood flow is restored, the function of these chronically ischemic myocytes can return with regeneration of all the normal cytoplasmic proteins, but this return is gradual.

46
Q

What can happen if the ischemia occurs slow enough?

A

collateral coronary arteries can develop

47
Q

What is the definition of MI?

A

irreversible necrosis of heart muscle due to prolonged ischemia (greater than 20 minutes)

48
Q

90% of MIs are due to what?

A

coronary atherosclerosis

49
Q

How can surgery lead to coronary thrombosis and myocardial infarction?

A

by making a hypercoagulable state

50
Q

When is the acute phase of an MI?

A

days 1-3

51
Q

When is the early, subacute phase of an MI?

A

days 4-10

52
Q

When is the late, subacute phase of an MI?

A

day 11- week 12

53
Q

Overall, reperfusion accelerates healing by about what percentage?

A

40%

54
Q

What is a common complication of anterior wall infarct? When does it happen? To whom?

A

Cardiac rupture, females and patients over 70 with hypertension 5 days after primary MI

55
Q

Why do cardiac ruptures occur at the edge of the infarct?

A

this is where the surviving muscle is contracting and pulling at the necrotic muscle (weakening it until it bursts)

56
Q

How might shock precipitate heart failure?

A

if you have an underlying heart condition and you go into septic shock, you vasodilate (which will increase HR and CO) and this increase demand on the diseased heart can cause it to fail

Cardio (24 decks)

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