Ischaemia & Infarction 2 Flashcards
Describe the appearance of infarcts within the first 24 hours.
There is not much visible to the naked eye, but swollen mitochondria can be seen on electron microscopy.
What is the macroscopic appearance of infarcts in solid tissues like the heart, spleen, and kidney after 24 to 48 hours?
They appear pale.
How do infarcts in tissues like the lung and liver appear macroscopically?
They may have a red appearance.
Define the microscopic changes seen in infarcts under a light microscope.
Acute inflammation at the edge of the infarct followed by loss of specialized cell features.
Describe the changes that occur in infarcts around 72 hours post-insult.
Pale infarcts start to look yellow and white, with a red periphery. Chronic inflammation, granulation tissue, and fibrosis begin to develop.
What cellular changes are observed in infarcts under a microscope during chronic inflammation?
Macrophages remove debris, new vessel formation occurs, and fibrosis with deposition of collagen takes place.
Describe granulation tissue.
Granulation tissue is a type of healing tissue characterized by chronic inflammatory cells, red blood cell lines, new vessel formation, collagen, and myocytes.
What is the end result of tissue damage in infarction?
The end result of tissue damage in infarction is the formation of a scar, which varies in shape depending on the territory of the occluded vessel.
Define reperfusion injury.
Reperfusion injury is the damage to tissue that occurs when blood supply returns after a period of ischemia, leading to inflammation and oxidative damage.
How does reperfusion injury occur?
Reperfusion injury occurs due to the absence of oxygen and nutrients during ischemia, causing inflammation and oxidative damage when blood supply is restored.
Describe the appearance of renal infarcts.
Renal infarcts appear as pale areas in the kidney, often resembling a white shape when the organ is partly opened.
What is the characteristic feature of a chronic myocardial infarction?
A chronic myocardial infarction is characterized by dense scar tissue and may show signs of cystic, softer areas due to chro-lipids of necrosis.
Describe the process of myocardial infarction from cell death to scar formation.
Cell death, acute inflammation, macrophage phagocytosis, granulation tissue formation, collagen deposition, scar formation.
What are the different timescales and changes observed in myocardial infarction progression?
Includes early coagulation necrosis, oedema, haemorrhage, myocyte changes, neutrophilic infiltration, granulation tissue formation, collagen deposition, and scar formation.
Define transmural myocardial infarction.
It affects the full thickness of the myocardium, leading to haemo-necrosis throughout the wall.
How does the appearance of an infarct change over time under the microscope?
From dense white scarred areas to lighter yellow and white areas initially, then collagenous tissue replacing myocytes.
Describe the role of macrophages in myocardial infarction.
They phagocytose dead cells, leading to granulation tissue formation and collagen deposition.
What are the reparative processes that occur in myocardial infarction?
Cell death, acute inflammation, macrophage phagocytosis, granulation tissue formation, collagen deposition, scar formation.
Describe the histological features of a subendocardial infarct.
Ischaemic necrosis mostly limited to a zone just under the endocardial lining of the heart, followed by granulation tissue stage and fibrosis.
What is a non-ST Elevation MI and how is it related to subendocardial infarct?
It is when there is no ST-segment elevation but significantly elevated troponin levels, thought to correlate with subendocardial infarct.
Define acute infarcts classification based on ECG changes.
Acute infarcts are classified based on whether there is elevation of the ST segment on the ECG.
How are the effects of infarction site-dependent?
Effects can vary within the body and organ, affecting different parts like the conducting system or myocardium.
Describe the complications of myocardial infarction.
Complications can be immediate, early, or late, including sudden death, arrhythmia, angina, and cardiac failure.
What factors influence the repair time of a subendocardial infarct compared to a transmural infarct?
The repair time may be slightly shortened due to less thick damage in a subendocardial infarct.
