Pathophysiology of ischaemia and infarction Flashcards
What is ischaemia?
Ischaemia is reduced blood flow to a tissue, leading to a shortage of oxygen and nutrients.
What is hypoxia?
Hypoxia is a lack of oxygen in tissues, which can occur with or without ischaemia.
What is infarction?
Infarction is tissue death (necrosis) due to prolonged ischaemia.
How does atheroma cause ischaemia?
Atheromatous plaques narrow arteries, reducing blood flow.
Plaques may rupture, leading to thrombosis and complete occlusion.
This can result in ischaemic heart disease (IHD), stroke, or peripheral vascular disease.
What are the main consequences of ischaemia?
Reversible effects → Cell dysfunction, pain (e.g., angina).
Irreversible effects → Cell death (infarction), organ failure.
Which organs are most affected by ischaemia?
Heart → Angina, myocardial infarction (MI).
Brain → Transient ischaemic attack (TIA), stroke.
Kidneys → Acute kidney injury (AKI).
Legs → Peripheral arterial disease (PAD), gangrene.
What factors affect oxygen supply to the heart?
- Coronary blood flow, oxygen content of blood, hemoglobin levels.
What factors affect oxygen demand in the heart?
- Heart rate, contractility, afterload (pressure the heart pumps against).
How does an imbalance between supply and demand lead to ischaemia?
If oxygen demand exceeds supply, myocardial ischaemia occurs, leading to angina or myocardial infarction.
What is the process of infarction?
Arterial occlusion → Blockage stops blood flow.
Oxygen deprivation → Cells switch to anaerobic metabolism.
Cell injury and necrosis → Irreversible damage occurs.
Inflammation & healing → Dead cells are replaced by scar tissue.
What is the difference between subendocardial and transmural infarction?
Subendocardial infarction → Partial thickness of heart wall affected, due to partial occlusion.
Transmural infarction → Full thickness of heart wall affected, due to total occlusion.
Why is transmural infarction more severe?
It leads to greater loss of contractile function, higher risk of ventricular rupture and heart failure.
What are the short-term and long-term effects of myocardial infarction?
Short-term → Arrhythmias, cardiogenic shock, acute heart failure.
Long-term → Heart failure, aneurysm, risk of further infarction.
How does the heart heal after an infarction?
0-24 hours → Coagulative necrosis, arrhythmias may occur.
1-3 days → Acute inflammation, neutrophil infiltration.
3-7 days → Macrophages remove dead tissue, risk of rupture.
1-2 weeks → Granulation tissue forms.
2-8 weeks → Collagen deposition, fibrosis replaces dead tissue.
