Lect 13 - Atheroma, Thrombosis & Embolism Flashcards
what is Atherosclerosis
“Degeneration of arterial walls characterised by fibrosis, lipid deposition and inflammation which limits blood circulation and predisposes to thrombosis”
what vessels are commonly affected by Atherosclerosis
Bifurcations (sites of turbulent flow) Abdominal aorta Coronary arteries Popliteal arteries Carotid vessels Circle of Willis
What are the common nonmodifiable risk factors for Atherosclerosis
Age
Male
FH
Genetic
what are the modifiable risk factors for atherosclerosis?
Hyperlipidaemia (LDL:HDL)
Hypertension
Smoking
Diabetes
talk though the Pathophysiology of Atherosclerosis formation, up to the point of fatty streak formation.
endothelial injury -> lipid accumulates in intima ->Monocytes come and ingest the lipid becoming foam cells
FORMS FATTY STREAK
what do foam cells do?
secrete chemokines attracting more monocytes/macrophages, lymphocytes and smooth muscle cells
CONSTITUENTS OF THE ATHEROSCLEROTIC PLAQUE
What different zones within the plaque form?
the edges = “shoulders”
the top = “fibrous cap”
the middle = “necrotic core”
what tends to happen after atherosclerosis formation?
Occlusion
Weakening of vessel walls
Aneurysm formation
Erosion
Thrombosis formation?
what is a Thrombosis
Solidification of blood contents formed in the vessel during life.
it is different to a clot in pathogenesis and morphology.
what factors make up virchow’s triad
The intimal surface of the vessel
The pattern of blood flow
Blood constituents
what are platelets fragments of?
Fragments of megakaryocytes in the bone marrow
what do Platelets release?
Alpha granules: fibrinogen, fibronectin, PDGF
Dense granules: chemotactic chemicals
why would plaque rupture lead to arterial thrombus?
causes turbulent flow and intimal change. also Hyperlipidaemia – change in blood constituents
Platelets bind and fibrin is produced entrapping RBC
what is Venous thrombosis caused by?
Intimal change: valves
Change in blood flow: Immobile
Change in blood constituents:
Inflammatory mediators (infection, malignancy)
factor V leiden
Oestrogen
what is a thrombi in the heart known as?
mural thrombi
where do mural thrombi form?
over areas of endomyocardial injury:
MI
Myocarditis
NOTE : Can also occur with arrhythmias and cardiomyopathy
what is the major risk of thrombosis?
Embolisation
what is an Embolus
A mass of material in the vascular system able to lodge in a vessel and block it
what is the most common type of emboli?
PE.
Very common cause of hospital morbidity and mortality
what are the clinical effects of a small PE
initially asymptomatic, if multiple may result in pulmonary hypertension
what are the clinical effects of a medium PE
Cause acute respiratory and cardiac failure (V/Q mismatch, RV strain)
what are the clinical effects of a large (saddle) PE
Death
what are the types of emboli? (6)
infective tumour gas Amniotic fluid embolism Fat embolism Foreign body embolism
where do Infective emboli come from?
Usually from the vegetations on infected heart valves
Effects compounded by the infective nature – may lead to mycotic aneurysm formation
where do Tumour emboli come from?
Bits may break off as tumours penetrate vessels
Do not usually cause immediate physical problems
where do Gas emboli come from?
Air (vessel opened into the air)
Nitrogen Decompression sickness (“the bends”)
where do Amniotic fluid emboli come from?
Increased uterine pressure during labour may force AF into maternal uterine veins (1:50,000 deliveries)
where do fat emboli come from?
Microscopic fat emboli found in 80% patients with significant trauma at PM
Sudden onset of respiratory distress
where do foreign body emboli come from?
Particles injected intravenously
E.g. talc in IVDU’s
Leads to a granulomatous reaction
