Pathophysiology of ischaemia and infarction (part 2) Flashcards
how does infacrts appear to the naked eye in the fiorst 24 hours?
not much to see upon visual inspection
What can be seen (infarction) form a few hours to 24hours?
see swollen mitochondria on electron microscopy
what is the visual appearance of infarction from 24-48 hours?
pale infarct
red infarct
What tissues/organs have a pale infarct?
myocardium, spleen, kidney, solid tiossues
What tissues/organs have a red infarct?
lung, liver, loose tissues, previously congested tissues; second/continuing blood supply, venous occlusion
What occurs microscopically (24-48 hours infarction) at the edge of infarct?
loss of specialized cell features
Does the red infarct change ~72 hours onwards?
little change
Does the pale infarct change ~72 hours onwards?
yellow/white and red periphery
How do the infarcts apppear microscopically ~72 hours onwards?
chronic inflammation; macrophages remove debris; granulation tissue; fibrosis
What is the end result of infarction?
scar replaces area of tissue damage
shape depends on territory of occluded vessel
repurfusion injury
What is reperfusion injury?
return of oxygen supply to an area after ischaemia - not ideal - inflammation to area
What is the reoparative processs of MI?
cell death
acute inflammation
macrophage phagocytosis of dead cells
granulation tissue
collagen deposition (fibrosis)
scar formation
What occurs 4-12 hours MI?
early coagulation necrosis, oedema, haemorrhage
What happens 12-14 hours MI?
ongoing coagulation necrosis, myocyte changes, early neutrophilic infiltrate
What happens 1-3 days MI?
coagulate necrosis, loss of nuclei and striations, brisk (lots) neutrophilic infiltrate
What happens 3-7 days MI?
disintegration of dead myofibres, dying neutrophils, early phagocytosis
What happens 7-10 days MI?
well developed phagocytosis, granulation tissue at margins
What happens 10-14 days MI?
well established granulation tissue with new blood vessels and collagen depositionW
What happens 2-8 weeks MI?
increased collagen deposition, decreased cellularity
What happens >2 months MI?
dense collagenous scar
What is transmural infarction?
ischaemia necrosis affects full thickness of the myocardium
Whatis subendocardial infarction?
ischaemic necrosis mostly limited to a zone oof myocardium under the endocardial lining of the heart
Compare the length of time for granulation tissue stage followed by fibrosis for transmural infarction vs subendocardial infarction?
in subendocardial infarct possibly slightly shortened compared to transmural infarct
What are the acute myocardial infarcts classified according to?
whether there is elevation of the ST segment on the ECG
What happens if there is no ST segment elevation but significantly elevated serum troponin level?
non-STEMI
What is non-STMI, in relation to ST segment and troponin levels?
no ST segment elevation
significantly elevated serum troponin level
What does non-STEMI correlate with?
subendocardial infarct
What are factors effecting the effects of infarction?
site dependent - within body and organ
size of infarct
(may cause) death, dysfunction (pain)
contribution of previous disease/infarction - there will be decreased reserve in the person to cope with infarction
What are the time categories of MI?
immediate
early
late
