Histo: Vascular and Cardiac Pathology Flashcards
What is atherosclerosis?
A disease characterised by atheromatous deposits and fibrosis of the inner layer (tunica intima) of arteries
List some risk factors for atherosclerosis.
- Age
- Sex
- Genetics (familial hypercholesterolaemia)
- Hyperlipidaemia
- Hypertension
- Smoking
- Diabetes mellitus
- Obesity
RFs have multiplicative effect
Outline the pathogenesis of atherosclerosis.
What is a fatty streak?
- Earliest change in atherosclerosis
- Lipid-filled foamy macrophages deposit in the intima
- No flow disturbance
NOTE: presence in pretty much everyone > 10 years old
What is an atherosclerotic plaque?
- Lesion composed of cells, lipid, matrix
- Causes local flow disturbance
What is critical stenosis?
- Point at which oxygen demand is greater than supply
- Occurs at around 70% occlusion
- Causes stable angina
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.
- Large lipid core
- Thin fibrous cap
What is the leading cause of death worldwide for both sexes?
Ischaemic heart disease
List the possible presentations of ischaemic heart disease.
- Angina pectoris
- MI
- Chronic ischaemic heart disease with heart failure
- Sudden cardiac death
What degree of stenosis is required for:
- Chest pain precipitated by exercise
- Chest pain at rest
- 75% stenosis
- 90% stenosis
Where are the most clinically significant 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
- Types: stable, unstable, prinzmetal (due to artery spasm)
What are the characteristics of stable angina?
- Precipated by exertion
- Relieved by rest
- No plaque disruption
What are the characteristics of unstable angina?
- Onset with less exertion or at rest
- Disruption of plaque
- May have superimposed thrombus
- Warning of impending infarction
What is a myocardial infarction?
Death of cardiac muscle due to prolonged ischaemia.
Outline the pathogenesis of myocardial infarction.
- Sudden change in plaque
- Platelet aggregation
- Vasospasm
- Coagulation
- Thrombus evolves
Outline the myocardial response to plaque rupture.
- Loss of contractility occurs within 60 seconds
- Therefore heart failure may precede myocyte death (i.e. patients could get an arrhythmia and die before any histological changes take place)
- Irreversible after 20-30 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 + striations, homogenous cytoplasm, necrotic cell death
- 1-4 days - infiltration of PMNs then macrophages
- 5-10 days - removal of debris
- 1-2 weeks - granulation tissue, new blood vessels, myofibroblasts, collagen synthesis
- Weeks to months - strengthening and decellularising the scar
What percentage of MI are asymptomatic, and in which patient groups are these more common?
- 10-15%
- Common in elderly and diabetics
What is reperfusion injury?
- Restoring blood flow to hypoxic tissue increases supply of oxygen which leads to increased production of ROS
- Oxidative stress, calcium overload and inflammation can cause further injury
- Arrhythmias are common
- It can cause stunned myocardium - reversible cardiac failure lasting several days
What is hibernating myocardium?
- Chronic sublethal ischaemia leads to lower metabolism in myocytes which can be reversed with vascularisation
