ATHEROSCLEROSIS, THROMBOSIS AND EMBOLISM Flashcards
How many people fie each year due to hospital acquired Venous thrombone embolism?
32,000
we need to do VTE risk assessment on inpatients
Name the three layers of vessels
- Intima (Endothelial cell layer)
- Media (Smooth muscle layer)
- Adventitia (Fibrous connective tissue)
Describe the intima layer of blood vessels
It is made up of endothelial cells
Describe the media layer of blood vessels
It is a smooth muscle layer
Describe the adventitia layer of blood vessels
It is made up of fibrous connective tissue
Describe differences in the layers or arteries and veins
- In arteries media is much bigger than in veins
- Veins have a bigger lumen
- Veins have a larger adventitia than arteries
Where are endothelial cells found?
They are found don the interior surfaces of blood vessels and lymphatics and on the heart
What are endothelial cells on the heart called?
endocardium cells
What is the origin of endothelial cells?
Mesodermal origin
What are the functions of endothelial cells
- Barrier funcitons
- Involved in angiogenesis
- Mediation of coagulation
- Control of blood pressure
- Fluid filtration
Describe how endothelial cells carry our their barrier function
They have a semi selective barrier tat allows passage of white blood cells into and out of the blood
What can increase the permeability of endothelial cells?
Prolonged inflammation leads to increased permeability and tissue swelling
How do endothelial cells help mediate coagulation?
They have:
- Heparan sulphate which inactivates clotting cascade
- vWF which binds to stabilise factor VIII, binds to collagen linking platelets
How do endothelial cells help control blood pressure?
Through vasoconstriction and dilation
Name some disease where endothelial cell dysfunction is seen
- Diabetes
- Septic shock
- Hypertension
- Behcet’s
Other than disease what can cause endothelial cell dysfunction?
- Tobacco
- Air pollution
- Trans fat consumption
How can endothelial cell dysfunction be improved?
- Improved by smoking cessation
- Weight loss
- Improved diet
- Exercise
What is atheroma
It is the accumulation of intracellular and extra cellular lipid in the intimate of large and medium sized arteries
What is Atherosclerosis?
The thickening and hardening of arterial walls as a consequence of atheroma
Why do atheromas forms?
They form in repose to chronic endothelial cell damage
Why do atheromas mainly occur in arteries?
As blood is under much greater pressure in the arteries
Go through the steps of atheroma/ Atherosclerosis development
- Chronic endothelial cell injury
- Endothelial dysfunction
- Entrance of cholesterol rich LDLs in to intima
- Lipid engulfed by intima macrophages
- Formation of a flat yellow fat streak later forming raised yellow lipid plaques
- Extra cellular lipid deposits and collagen deposition leading to a fibrous cap over the lipids core (HARD yellow fatty plaque)
7 Ulceration of plaque - Predisposition of thrombus formation (Advanced complicated plaque formation)
Give some risk factors for atheroma/atherosclerosis
- High LDL / Low HDL diet
- Hypertension
- Diabetes
- Smoking
- Obesity
- Sedentary lifesyle
What is primary prevention of for atheroma/atherosclerosis?
It is aimed at delaying atheromatous formation or causing regression of established lesion in people who have never suffered serious complications
What is secondary prevention of for atheroma/atherosclerosis?
It is intended to precent recurrence of events such as myocardial infarction and stroke in patients who have already suffering a significant event
What does primary prevention of atheroma/atherosclerosis involve?
Essentially involved risk factor modification
What does secondary prevention of atheroma/atherosclerosis include?
Includes regular medication such as aspirin
When do early lesions of atheromas usually form?
Early lesion begin in 20s and 30s
Are atheromas reversible?
No they can’t be reversed and the disease is progressive
What can be used to stabilise plaque and prevent plaque rupturing blood vessels?
We can use drugs like lipid modifying agents such as statins
What can be used in cases where blood vessel rupture has occurred?
Antithromobtic agents may be used in case of rupture, leading to exposure of subendothelial extra-cellular
How do calcium antagonists affect atheromas?
They may reduce foam cell production
Name the 4 main sites atheromas occur
- Aorta
- Coronary arteries
- lilac and popliteal arteries
- Internal carotis arteries
How is the aorta affected by atheromas?
- Can weakening of the walls
- This leads to aortic aneurysms (due to dilation of aorta)
- Risk of aorta rupturing increases
How are the coronary arteries affected by atheromas?
- Artery lumen narrows leading to reduced blood flow causing ischaemia (angina)
OR - Thrombus fors over plaque leading to occlusion of lumen causing infarction
How are lliac and popliteal arteries
affected by atheromas?
Lumen of the arteries narrow reducing blood flow causing ischaemia (intermittent claudication, gangrene)
How are the interns carrots arteries affected by atheromas?
An emboli can throw off and travel to the brain
This emboli blocks blood flow to the brain and can cause ischaemia (if transient) or infarction (or stroke)
What is thrombus?
It is a structured solid mass or plug of blood constituent formed within the heart of blood vessels during life
What is thrombosis ?
The process of thrombus formation
This can be considered to the inappropriate activation of the normal ischaemia (if transient) or infarction (TIA or stroke)
Where can thrombus happen?
It can occur anywhere waiting the cardiovascular system
Name the 3 types of thrombus
- Arterial
- Cardiac
- Venous
Where does arterial thrombus occur?
Usually at sits of endothelial injury or turbulence
Name some common sites where arterial thrombus occurs
- Coronary arteries
- Cerebral arteries
- Femoral arteries
What is cardiac thrombus sometimes called?
Mural thrombi
Where does cardiac thrombus occur?
Over areas of endomyocardial injury
Can also occur with arrhythmias and cardiomyopathy
What are the potential outcomes of thrombus ?
Propagation
Embolism
Dissolution
Organisation/ recanalisation
Where does venous thrombus occur?
Usually occurs at sites of vascular stasis
Vast majority occur in the veins of the lower limbs
What are the potential outcomes of thrombus ?
Propagation
Embolism
Dissolution
Organisation/ recanalisation
What are predisposing conditions to thrombus called?
Hyper coagulable conditions
Name some genetic Hyper coagulable conditions
- Protein C or S deficiency
- Antithrombin III deficiency
- Factor V mutations
- Prothrombin mutations
What do genetic Hyper coagulable conditions affect?
They prevent the bodies ability to carry out the clotting cascade
Name some environmental Hyper coagulable conditions
- Stasis eg Prolonged bed rest and long haul flights
- Atherosclerosis
- Smoking
- Atrial fibrillation
- Prosthetic heart valves
- Myocardial infarction
- vasculitis
- Neoplasia
- Oral contraceptives
- Disseminated intravascular coagulation