Atheroma Flashcards
What is atherosclerosis?
The thickening and hardening of arterial walls as a consequence of atheroma
What is atheroma?
The accumulation of intracellular and extracellular lipid in the intima and media of large and medium sized arteries.
What is arteriosclerosis?
The thickening of the walls of arteries and arterioles as a result of hypertension or diabetes mellitus
List some macroscopic features of atheroma
Fatty streak
Simple plaque
Complicated plaque
What is a fatty streak?
A raised, yellow structure where lipid has deposited in the intima. Thought to be a precursor to atheroma
What is a simple plaque?
A raised, slightly yellow plaque. Can enlarge and coalesce
What is complicated plaque?
When pressure of the blood in the artery causes haemorrhage into the plaque. Leads to thrombosis, calcification and then aneurysm.
Have a rich lipid core and thin fibrous cap
List some common sites for atheroma
Aorta
Coronary arteries
Carotid artery
Leg arteries
What is contained within the intima, media and adventitia of arteries?
Intima - endothelium and sub endothelial connective tissue
Media - smooth muscle and elastic tissue
Tunica adventitia - external elastic lamina and adventitia
Pathology of atheroma?
Endothelial injury
Platelet adhesion and PDGF released - affects SMCs
Macrophages, lymphocytes, smooth muscle cells and LDLs accumulate
Macrophages phagocytose LDLs and become foam cells
Foam cells can die and release their contents, producing a lipid core
Macrophages release cytokines and growth factors, leading to proliferation of the smooth muscle layer towards the lipid core and into the media through the elastic lamina
Inflammatory response - collagen and other matrix proteins are laid down - fibrosis
Small blood vessels grow into the plaque
List some clinical effects of atheroma
Ischaemic heart disease
Cerebral ischaemia
Mesentric ischaemia
Peripheral vascular disease
Symptoms of ischaemic heart disease?
Myocardial infarction due to thrombus on a coronary artery
Angina
Cardiac arrhythmia
Cardiac failure
Symptoms of cerebral ischaemia
Transient ischaemic attack
Cerebral infarction (stroke)
Multi-infarct dementia
What do patients present with in mesentric ischaemia?
Ischaemic colitis - abdominal pain and bleeding
Malabsorption
Intestinal infarction - acute
What do pateints present with in peripheral vascular disease?
Intermittent claudication - calf pain on exercise
Gangrene
List the modifiable risk factors for atherosclerosis
Diabetes Hyperlipidaemia Hypertension Cigarette smoking Exercise
List the non-modifiable risk factors
Age and gender
What is lipid in the blood carried by?
Lipoproteins
Where and what do chylomicrons transport?
Triglycerides
Intestine to tissues
What and to where do VLDLs transport lipids?
Cholesterol and triglycerides
From the intestine to the liver
What and where do LDLs transport?
Cholesterol to non liver cells
Where and what do HDLs transport?
Cholesterol
From peripheries back to liver
Physical signs of familial hyperlipidaemia?
Corneal arcus
Tendon xanthomas
Xanthalasma
How does smoking increase risk of atheroma?
Affects coagulation system
Increases platelet stickiness
Decreases prostaglandins
Increases fibrinogen levels
How many units a day increase risk of IHD?
More than 5
What role do endothelial cells have in atheroma?
Pro and anti-coagulant effects
Altered permeability to allow lipoproteins in
Secrete collage
Stimulate proliferation and migration of smooth muscle cells
Role of platelets in atheroma?
Haemostasis
Stimulate proliferation and migration of smooth muscle cells by platelet derived growth factor
Role of smooth muscle cells?
Respond to stimuli and migrate.
Take up LDL and become foam cells
Produce collagen and proteoglycans
Role of macrophages?
Oxidise LDL
Take up lipids to become foam cells
Secrete proteases which modify the matrix and affects plaque stability
Proliferation and migration of SMCs
Role of lymphocytes?
Produce tumour necrosis factor which may affect lipoprotein metabolism
Proliferation/migration of smooth muscle cells
Role of neutrophils?
Secrete proteases leading to local damage and inflammation
Produce cytokines which modify extracellular matrix, affecting at ikith of the plaque
What can endothelial injury be caused by?
Raised LDL
Hypertension
Haemodynamic stress
