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Heart Pathology II
Exam 4
19
Medical
Graduate
10/19/2010

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Cards

Term
In transmural infarction, what is the extent of necrosis?
Definition
There is necrosis that spans the entire thickness of the myocardial wall, but it is laterally limited by the area of distribution of the now-occluded coronary artery.
Term
What are the features of subendocardial infarction?
Definition

1. necrosis limited to inner 1/3 of the ventricular wall

2. damage can extend laterally beyond area of distribution

3. subendocardial zone normally the least perfused area, so more prone to necrosis

Term
With subendocardial infarction, is there an increase or decrease in blood pressure?
Definition
decrease; it's been postulated that the prolonged, severe reduction in systemic blood pressure, as in shock superimposed on chronic coronary stenosis can lead to subendocardial infarct
Term
What are the 3 steps of pathogenesis of the myocardial infarction?
Definition

1. coronary occlusion

2. myocardial response

3. infarct modification by reperfusion

Term
What things modify the effects of coronary artery occlusion?
Definition

1. increased O2 demand

2. decreased blood pressure

Term
In the myocardial response, what two things happen within a minute?
Definition
There is cessation of aerobic glycolysis, and there is
Term
In order for there to be irreversible damage, how long does ischemia have to occur?
Definition
20-40 minutes
Term
When does classic acute myocardial infarction begin?
Definition
2-4 hours after occlusion of the coronary artery
Term
During an MI, what part of the myocardium is preserved (unaffected) and why?
Definition
There is a narrow rim (1cm ) of preserved subendocardium due to direct diffusion of oxygen and nutrients in the lumen
Term
If the patient has died 2-3 hours after an MI, how might it be possible to highlight the area of necrosis?
Definition
We immerse the tissue slices in either triphenyltetrazolium chloride solution or nitroblue tetrazolium.
Term
From 12-24 hours to 10 days, describe the change in the general morphology of the infarct.
Definition
We start with dark, mottling reddish color due to the trapping of blood. Then, there is the development of tannish-yellow core. The area gets softer, and there is surrounding the center reactive hyperemia.
Term
From 10 days to 2 months, describe the change in the general morphology of the infarct.
Definition
We start with red-gray depressed infarct borders, and then we have the formation of a collagen scar starting from the border and heading toward the center of the infarct. Two months later, we have a complete fibrous scar formation.
Term
In an MI, what does the histology look like 4-12 hours out?
Definition
There are "wavy" fibers and myocytolysis- large vacuolar spaces that are within cells and probably contain water
Term
When do we start to see prominent macrophages and then formation of granulation tissue?
Definition
We start to see macrophages 7-10 days out, followed by granulation tissue formation between 10-14 days out
Term
Why is a reperfused infarct usually hemorrhagic?
Definition
When there is ischemia, the vasculature is injured. So, when red cells rush in again, there is leakage.
Term
During microscopic examination, what might be noticed of the myocytes afte rreperfusion?
Definition
The myocytes may be irreversibly damaged, containing contraction bands (eosinophilic stripes of sarcomeres due high exposure of calcium from reperfused red cells)
Term
Cardiogenic shock occurs in what percentage of contractile dysfunction cases, and what is the mortality rate?
Definition
10-15% of cases/ mortality associated with cardiogenic shock is 70%
Term
What percentage of acute MI's involve arrythmias and mural thromboses, respectively?
Definition
90%, 30%
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