Atheroma Flashcards
What is an atheroma?
Formation of focal elevated lesions (plaques) in intima of large and medium-sized arteries
what are the four stages of atheroma?
fatty streak
early atheromatous plaque
fully developed atheromatous plaque
complicated atheromatous plaque
fatty streak
- who’s affected?
- what is the clinical significance ?
- what is the appearance ?
- what causes it?
young children are affected
no clinical significance
yellow linear elevation
lipid laden macrophages
what is the definition of a fully developed atheromatous plaque?
central lipid core with a fibrous cap, covered by arterial endothelium.
what is the fibrous cap made up of?
collagen (made from smooth muscle) and inflammatory cells
what is the central lipid core made up of?
cellular lipids and debris derived from macrophages
why are some macrophages “foamy”?
due to uptake of oxidised lipoproteins via specialised membrane bound scavenger receptor
what are three characteristics of late stage development of fully developed atheromatous plaques ?
Dystrophic calcification extensive
Confluent
Cover large areas
What three things can make an atheroma complicated?
- Haemorrhage into plaque (calcification)
- Plaque rupture/fissuring
- Thrombosis
what is arteriosclerosis ?
thickening of the media layer of the blood vessel which can compromise blood flow. (NOT atheromatous)
- hypertrophy of the smooth muscle
- duplication of the internal elastic laminae
- intima fibrosis
what is the biggest risk factor for atheromatous plaques?
hypercholestrolaemia
can hyperlipidemia be related to genes?
yes
how many caucasians are heterogeneous for the gene mutation when cell membrane receptors for LDLs are absent?
1/500
how can chronic hyper cholesterol directly damage endothelium?
by increasing the number of reactive oxygen species which creates more foamy macrophages which are toxic to the endothelial cells and release growth factors and cytokines.
state the five main risk factors for hyperlipidemia and other less strong risk factors
- age
- male
- smoking
- hypertension
- diabetes
- obesity
- low birth weight
- low economic status
- lack of exercise
what are the three clinical signs of hyperlipidemia ?
- corneal arcus
- tendon xanthomata
- xanthelasmata
What are the two ways to form an atheroma?
- injury to endothelial lining of artery
2. chronic inflammatory and healing response of vascular wall to agent causing injury
describe the pathophysiology of atheromatous plaques
- Endothelial injury
- Endothelial dysfunction
- Enhanced expression of cell adhesion molecules (ICAM-1, E-selectin)
- High permeability for LDL
- Increased thrombogenicity - Accumulation of lipoproteins (LDL) in vessel wall
- Monocyte adhesion to endothelium → migration into intima and transformation to foamy macrophages (by free radicals)
- Platelet adhesion
- Factor release from activated platelets, macrophages (tissue factors)→ smooth muscle cell recruitment
- Smooth muscle cell proliferation, extracellular matrix production and T-cell recruitment
- Lipid accumulation (extracellular and in foamy macrophages)
What can occur in a blood vessel when an atheroma ruptures and releases many thrombogenic substances into the blood?
the collagen, lipids and debris clot together with platelets and can cause complete occlusion of a vessel which results in reduced blood flow (ischaemia) and may even result in an infarction (necrosis of tissue)
give three examples of vessel occlusion consequences
MI
stroke
lower limb gangrene
what are vulnerable atheromatous plaques?
atheromatous plaques the are likely to rupture/ become complicated
thin fibrous cap, large lipid core, prominent inflammation
what are the three options for management of atheromatous plaques?
prevention
- smoking cessation
- control BP
- weight loss/diet control
- regular exercise
secondary treatment
- statins
- aspirin
surgical options
generally what are the common characteristics of highly stenotic atheromatous plaques ?
large fibrocalcific component
little inflammation
what three substances do plaque inflammatory cells release to increase degradation?
- cytokines
- proteolytic enzymes
- reactive oxygen species
what three ways are endothelial cells altered when they become injured ?
Enhanced expression of cell adhesion molecules (ICAM-1, E-selectin)
High permeability for LDL
Increased thrombogenicity