Histo: Vascular and Cardiac Pathology Flashcards
(43 cards)
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
What is reperfusion injury?
- Consequence of letting blood go back into the area of myocardial necrosis
- Oxidative stress, calcium ovrload and inflammation caus further injury
- Arrhythmias are common
- It can cause stunned myocardium - reversible cardiac failure lasting several days
What is hybernating myocardium?
- Chronic sublethal ischaemia leads to lower metabolism in myocytes which can be reversed with vascularisation
List some complications of MI.
DARTH VADER
Death
Arrythmia
Rupture
Tamponade
Heart failure
Valve disease
Aneurysm
Dressler’s
Embolism
Recurrence
following an MI, if a patient develops ventricular anneurysm what do you expect to see on an ECG
Asymptomatic persistent ST elevation in certian leads.
What is the 1-year mortality after an MI?
30%
What is chronic ischaemic heart disease?
Progressive heart failure due to ischaemic myocardial damage
NOTE: there may be no prior infarction, usually due to atherosclerosis
What is sudden cardiac death?
Unexpected death from cardiac causes in individuals without symptomatic heart disease or early after the onset of symptoms (e.g. 1 hour)
Usually due to lethal arrhythmia (ischaemi-induced electrical instability)
