Atherosclerosis Flashcards
What is atherosclerosis ?
“Inside of an artery narrows due to the build up of plaque”
Which kinds of vessels does atherosclerosis affect ?
Elastic and medium to large muscular arteries
What are the main components of an atheroma ?
Intimal fibrous cap
Central core rich in lipids (necrotic center)
Patchy and raised white to yellow 0.3-1.5cm
Fatty streaks: may be elongated streaks (1cm or longer) or fatty dots (< 1 mm)
Foam cells + T lymphocytes
Cholesterol crystals in tunica intima
What percentage of all deaths does symptomatic atherosclerosis contribute to ? How so ?
Half
Because atherosclerosis is involved in MI, Stroke, Aneurysms, Peripheral vascular disease
What are a few reasons that mortality rates due to heart attack and stroke are decreasing, wrt atherosclerosis ?
- Prevention of atherosclerosis
- Improved methods of treatment
- Prevention of recurrences
What are some risk factors for atherosclerosis ?
- Age (risk increases with increased age)
- Sex (Men more predisposed, especially when women are in reproductive period. After menopause, slowly starting getting same level as men (partly because oestrogen)
- Genetics
- Hyperlipidaemia
- Hypertension
- Smoking
- Diabetes mellitus
What is the pathogenesis of atherosclerosis ?
- Chronic endothelial injury / dysfunction
- Lipids and macrophages play a role
- Smooth muscle proliferation
- Formation of a fibro-lipid plaque
- Injury to the plaque – thrombus formation
What are possible causes of chronic endothelial injury (step 1 in pathogenesis of atherosclerosis) ?
- Haemodynamic disturbances
- Hypercholesterolemia
- Hypertension
- Smoking
- Toxins
- Viruses
- Immune reactions
What is meant by endothelial dysfunction, following chronic endothelial injury ?
- Increased endothelial permeability
- Leukocyte adhesion
- Monocyte adhesion and migration (to tunica intima, where they change into macrophages)
What is the role of lipids in atherosclerosis ?
Hyperlipidaemia (LDL cholesterol) results in:
– Impairs endothelial function
– Accumulates within intima
– Causes oxidative modification of LDL:
• After oxidation, ingested by macrophages via SCAVANGER receptors = foam cells (hence immobilised)
• Chemotactic for monocytes
• Inhibit the motility of macrophages
• Stimulates release of cytokines
• Cytotoxic to endothelial and smooth muscle cells
What is the role of macrophages in atherosclerosis ?
- Monocytes which have migrated from lumen to tunica intima get activated as macrophages
- Secrete IL1 (Interleukin-1), TNF (Tumor necrosis factor), MCP1 (Monocyte chemotactic protein 1) and growth factors
- Engulf oxidised LDL = foam cells
- Foamy cells accumulate together, start raising lumen of artery (brown yellow line, FATTY STREAK)
What is a fatty streak ? What is it made of ?
Mature fibro-fatty Atheroma ( Foam cells + T lymphocytes), first grossly visible lesion in the development of atherosclerosis
What is the role of smooth muscle cells in atherosclerosis ?
Migrate from tunica media to tunica intima where they may act as phagocytes (engulf lipids which come from lumen to tunica intima)
Proliferate
Once die, rutpture and the cholesterol ingested becomes crystalised
Smooth muscle cells in tunica intima start organising, (depositing collagen and ECM ?)
Which 6 arteries does atherosclerosis most usually occur in ?
In descending order, ACP DIV
Abdominal Arteries Coronary Arteries Popliteal Arteries Descending Thoracic Aorta Internal Carotid Arteries Vessels of the Circle of Willis
What are possible complications of atherosclerosis ?
– Calcification – Rupture or ulceration – Haemorrhage – Thrombosis – Aneurysmal dilatation
