Histo: Vascular and Cardiac Pathology Flashcards
What is atherosclerosis?
A disease characterised by fatty deposits and fibrosis of the inner layer (tunica intima) of arteries
List some risk factors for atherosclerosis.
- Age (40-60)
- Gender
- Genetics
- Hyperlipidaemia
- Hypertension
- Smoking
- Diabetes mellitus
Outline the pathogenesis of atherosclerosis.
- Endothelial injury causes accumulation of LDL
- LDL enters intima and is trapped
- LDL is converted into modified and oxidised LDL causing inflammation
- Macrophages take up oxiLDL via scavenger receptors and become foam cells
- Apoptosis of foam cells causes inflammation and cholesterol core of laque
- Increase in adhesion molecules in endothelium due to inflammation results in more macrophages and T cells entering plaque as well as platelet aggregation.
- Vascular smooth muscle cells are also recruited from tunica media forming fibrous cap
What is a fatty streak?
- Earliest change in atherosclerosis
- Lipid filled foamy macrophages deposit in the intima but they do not disturb flow
NOTE: presence in pretty much everyone < 10 years old
What is critical stenosis?
When oxygen demand is greater than supply
This occurs at around 70% occlusion and causes stable angina at first
List three types of acute plaque change.
- Rupture - exposes prothrombogenic plaque contents
- Erosion - exposes prothrombogenic subendothelial basement membrane
- Haemorrhage into plaque - increases size
In which patients does acute plaque change tend to happen?
Patients with mild-to-moderate atheroma (large plaques tend to be very stable)
List some features of vulnerable plaques.
- Lots of foam cells and extracellular lipids
- Thin fibrous cap
- Few smooth muscle cells
- Adrenaline increases BP and causes vasoconstriction
- Circadian rhythm (more likely to have an infarct in the morning)
List the possible presentations of ischaemic heart disease.
- Angina pectoris
- MI
- Chronic ischaemic heart disease with heart failure
- Sudden cardiac death
What are the most common sites for atheromatous plaques within the coronary circulation?
- First few centimetres of the LAD and left circumflex
- Entire length of right coronary artery
What is angina pectoris?
Transient ischaemia that does not produce myocyte necrosis
What is a myocardial infarction?
Death of cardiac muscle due to prolonged ischaemia.
Outline the pathogenesis of myocardial infarction.
- Coronary arthersclerosis
- Rupture of plaque resulting in platelet activation + thrombosis OR vasospasm OR emboli occluding vessel further down
- Decreased blood supply resulting in ischaemia, infarction that is irreversible past 20-40mins and results in myocardial necrosis
What is the most common cause of death in post-menopausal women?
Myocardial infarction
Outline the myocardial response to plaque rupture and subsequent ischaemia and infarction.
- Loss of contractility occurs within 60 seconds
- So, heart failure may precede myocyte death (so patients could get an arrhythmia and die before any histological changes take place)
- Irreversible after 20-40 mins
Which arteries tend to be involved in myocardial infarction (in order of most to least frequent)?
- LAD - 50%
- RCA - 40%
- LCX - 10%
Describe the microscopic changes that take place in myocardial infarction.
- Under 6 hours - normal histology
- 6-24 hours - loss of nuclei, homogenous cytoplasm, necrotic cell death
- 1-4 days - infiltration of polymorphs then macrophages
- 5-10 days - removal of debris
- 1-2 weeks - granulation tissue, new blood vessels, myofibroblasts, collagen synthesis
- Weeks to months - strengthening and decllularising resulting in scar tissue