Atheroma, Thrombosis, Embolism and Infarction Flashcards
What are atheromas
Fibro-fatty plaques.
What are the main locations of atherosclerosis
Elastic and medium to large muscular arteries. Common in the aorta and its branches. Not common in the pulmonary circulation.
What are some genetic conditions that increase the risk of atherosclerosis
Hypercholesterolaemia or genetic hyperlipodaemia.
Name the risk factors for atheroma
Age, male sex, genetics, hyperlipidaemia, hypertension, smoking, diabetes.
What is the first step in the parthenogenesis of atherosclerosis
Endothelial injury or dysfunction
What substances accumulate in the tunica intima during atheroma formation
Low density lipoproteins and foam cells.
Describe the process of the parthenogenesis of atheroma formation.
- Endothelial injury or dysfunction
- accumulation of LDL and foam cells in the intimal layer of the blood vessel wall
- smooth muscle proliferation from the medial layer
- fibrosis which forms a fibro-lipid plaque.
- Plaque injury to make the atheroma complicated such as thrombosis or haemorrhage.
At what stage does the fatty plaque become irreversible
When it gets to the point of forming an early atheroma in which the medial layer of the blood vessel becomes involved.
What are the components of an uncomplicated athermatous plaque
Foam cells (fat containing macrophages), smooth muscle cells from the medial layer, lymphocytes, fibrosis and a fibrous cap.
What is the difference between an early and late atheromatous plaque
In the early stages there is no involvement of the tunica media. In the late stages smooth muscle cells from the medial layer become involved, however it is still uncomplicated.
What can make a plaque “complicated”
Ulceration, haemorrhage, thrombosis.
Why is atherosclerosis more likely to be an issue in coronary arteries compared to the aorta
Because coronary arteries are narrower so less obstruction is required.
What are the local complications of atheroma
- calcification
- ulceration
- plaque rupture
- haemorrhage
- thrombosis
- aneurysmal dilatation (which can rupture)
- blood vessel obstruction and downstream ischaemia
What are the systemic complications of atheroma
Infarction, stroke, ischaemia, gangrene.
What is a thrombus
A solidification of blood constituents that forms within the vascular system during life.
What is thrombosis
A pathological process. It is the formation of a thrombus in an uninterrupted vascular system.
When is it normal for thrombus formation to occur
In an interrupted vascular system when it is associated with injury.
When is a blood clot not termed a thrombus
If it forms outside the vascular system or after dear
What are the risk factors for thrombosis
Endothelial injury, abnormal blood flow and hypercoagulability
What is the name given to the three risk factors for thrombosis - endothelial injury, abnormal blood flow and hypercoagulability
Virchow’s triad
What is the most common cause of endothelial injury
Atheroma
What is a cause of hypercoagulability
Increased clotting factors and platelets present after surgery.
Give examples of things which cause endothelial injury leading to thrombosis and when this may occur.
1) Ulcerated atheromatous plaques - occurs in the aorta, carotid arteries, iliac and femoral arteries, coronary arteries.
2) Left ventricular endocardium injury - occurs after MI
3) Abnormal cardiac valves - occurs in rheumatic fever, infective endocarditis, prosthetic valves.
How does abnormal blood flow result in thrombus formation
It prevents the dilution of clotting factors, prevents the inflow of inhibitors of clotting factors and promotes endothelial cell activation.
What can be the result of turbulent blood flow
The development of arterial and cardiac thrombi.
What can be the result of stasis
The formation of venous thrombi.
What are come genetic predispositions to hypercoagulability
Protein S or protein C deficiency
What is a mural thrombus
A mural thrombus is present on the wall of the structure.
Where do mural thrombi often form
The cardiac chambers
What is an occlusive thrombus
Occlusive thrombi obstruct the vessel completely.
What is the name given to thrombosis in a vein
Phlebothrombosis
What is thrombophlebitis
Inflammation in a vein with subsequent thrombosis.
What is shown in histology of thrombi
Alternating pale and dark “lines of Zahn”.
What is shown by the pale lines of Zahn
Fibrin and platelets.
What is shown by the dark lines of Zahn
Red blood cells.
What are the complications of thrombosis
Occlusion of an artery or vein, embolism - arterial (in the legs or brain) or venous (to the heart and lungs).
What is the end result of arterial occlusion
Loss of pulse distal to the thrombus, the area will become cold, pale and painful and eventually the tissue will die and gangrene will result.
What is the end result of thrombosis in the superficial veins of the leg
Congestion, swelling, pain and tenderness
What is the result of thrombosis in the deep veins of the leg
There can be foot and ankle oedema however it may also be asymptomatic and only recognised when it embolises.
What is an embolus
A detached intravascular liquid or gaseous mass that is carried by the blood to a site distant from its origin.
What is a thromboembolus
An embolus arising from a thrombus (99% of cases)
What are some rare forms of emboli
Bone or bone marrow fragments, atheromatous debris, fat droplets, tumour cells, foreign bodies, bubbles of air or nitrogen.
What is the origin of most pulmonary emboli
Thrombi in the deep veins of the lower leg, and second most commonly from the pelvis.
How can you tell after death that what is present in the blood vessel is an embolus
The calibre of an embolus is different from that of the vessel it becomes lodged in.
What is the name given to an embolus that lodges at the bifurcation of an artery
A saddle embolus
What is the outcome associated with saddle emboli
Collapse and sudden death
What is a paradoxical embolism
A pulmonary embolism that gains access to the systemic circulation as a result of an interatrial or interventricular defect.
What is often a feature of pulmonary infarction
They are often haemorrhagic.
What is an infarct
An area of ischaemic necrosis
What causes an infarct
Occlusion of arterial supply or venous drainage in a particular tissue.
What are the factors which influence the development of an infarct
- The nature of the vascular supply (single or dual)
- The rate of development of the occlusion
- The vulnerability of the affected tissue to hypoxia
- The oxygen content of the blood
How does the nature of the vascular supply affect the development of an infarct
A lot of organs have a single blood supply however some such as the lung and the small bowel have a dual blood supply. In these organs when one blood vessel is obstructed, the other will still be supplying blood so infarct will not happen as quickly.
Which type of tissues are more vulnerable to hypoxia as a result of infarct
Those which are more metabolically active such as the heart.
What are the three types of infarct
Red (haemorrhagic), white (anaemic) and septic.
In what situations does a red (haemorrhagic) infarct form
When there is venous occlusion (so blood cannot be returned through the venous system and pressure builds), in loose tissues and in tissue with a dual blood supply.
In what situations does a white (anaemic) infarct form
When there is arterial occlusion and in solid organs such as the heart and the spleen.
In what situations does a septic infarct form
In infected infarcts.
What can be seen in histology of an infarct
Ischaemic coagulative necrosis (minutes to days), an inflammatory response (hours - 7 days), reparative response (1-2 weeks) and scarring (2 weeks-2 months)
What is the repair process in infarction
Inflammation and scarring as infarct is irreparable.
