atherosclerosis

Question 1

what is a vulnerable plaque

Answer 1

characterized by a THIN, FIBROUS CAP with a large soft lipid cholesterol pool underneath it

these characteristics + normal stress on artery walls due to contraction and relaxation of vessels contribute to a high mechanical stress zone on the fibrous cap

prone to rupture

Question 2

what is the usual cause for sudden onset MI symptoms

Answer 2

embolism secondary to plaque rupture and thrombus formation

Question 3

what % of infarcts are caused by coronary artery atherosclerotic plaque erosion/thrombosis

Answer 3

90%

Question 4

what is the lethal cellular even in MI

Answer 4

cell membrane ion pumps fail

Question 5

which layer of the heart is most susceptible, comparatively, to infarction

Answer 5

subendocardium

infarction spreads from subendocardium to subepicardium in a WAVEFRONT phenomenon

Question 6

changes seen in cardiac tissue in early MI/ischemic injury phase of MI

Answer 6

microscopic–>

1. EM changes in myocytes and their membranes within first 15-20 min
2. wary fibers–> intracellular edema
3. coagulation necrosis–> hypereisonophilic myocytes
4. contraction band necrosis–> compaction of Z lines of sarcomeres

macroscopic–>

1. if no reperfusion of infarcted area, then pallor due to extrusion of erythrocytes from capillary bed
2. if reperfused then hemorrhagic from blood vessel bursting

Question 7

changes seen in cardiac tissue during the inflammatory stage of an MI

Answer 7

occurs from about 12 hours-5 days post MI

microscopic–>

1. influx of PMNs (if there is no reperfusion then they collect at the borders of the infarct, and if there is reperfusion then they are distributed throughout the infarct)
2. macrophages are seen after about 5 days
3. myocyte nuclei start to disappear and myocytes become attenuated and separated as phagocytosis of myocytes occurs

macroscopic–>
1. yellow center with hyperemic border (not reperfused) or prominent hemorrhage (reperfused)

Question 8

changes seen in cardiac tissue during the granulation tissue formation phase of an MI

Answer 8

occurs from about 1-3 weeks post MI

microscopic–>

1. residual macrophages
2. revascularization
3. fibroblasts and early collagen formation

macroscopic–>
infarct turns from yellow to grey

Question 9

changes seen in cardiac tissue during scar formation stage of MI

Answer 9

occurs from about 2-8 weeks post MI

microscopic–>
1. decrease in inflammatory cells with increasing collagen deposition and prominent capillary vessels

macroscopic–>
1. infarct changing from gray to white as collagenization becomes complete

Question 10

what are some complications from infarctions

Answer 10

1. death
2. arrhythmias
3. ventricular dysfunction
4. cardiogenic shock
5. recurrent infarction
6. infarct expansion
7. myocardial rupture
8. RV infarction
9. pericarditis
10. mural thrombus
11. ventricular aneurysm

Question 11

what usually causes death from MI

Answer 11

ventricular arrhythmia (vent tachy or vent fib)

50% of people die from their MI

Question 12

how do MIs lead to arrhythmias

Answer 12

arises from ischemic but non-infarcted tissue at the MI border zone

major determinant of post discharge mortality

Question 13

when does cardiogenic shock occur as a result of MI

Answer 13

when infarction of over 40% of myocardium occurs

causes low CO and BP which exacerbates the ischemia

Question 14

what is a transmural infarct

Answer 14

death of myocardium that extends from the endocardium to the epicardium as a result of MI