Arterial and Venous thrombosis Flashcards
What is the difference between a clot in a living and a dead person + why
Living - one layer
Dead - red cells tend to settle out before clot forms so we have two layers: Lower deep-red and upper clearer with platelets
What does the clot in a dead person take the shape of
The shape of the vessel in which they have formed
How does the clot formed in a dead person break down
Hydrolysis by enzymes released by cells of the vessel wall and RBCs
What is a thrombus
Solidification of blood contents that form within the vascular system during life
What is the role of a platelet
Closing small gaps in vessel walls through trauma
What are platelets derived from
Megakaryocytes
What structures can be found in platelets
- Mitochondria
- Cytoskeleton
- Alpha granules
- Dense granules
What do alpha granules in platelets contain
Fibrinogen, Fibronectin, Platelet growth factor and anti heparin
What are found in dense granules of platelets
ATP and ADP
Role of ATP and ADP in clotting
Platelet aggregation
What is the result of the platelet cascade forming in an intact non-damaged vessel
Thrombus
What three ways can a thrombus form
- Changes in intimal surface of vessel
- Changes in pattern of blood flow
- Changes in blood constituents
What three ways can a thrombus form
- Changes in intimal surface of vessel
- Changes in pattern of blood flow
- Changes in blood constituents
^ Virchow’s triad
How does an atheromatous plaque cause arterial thrombosis
- Plaque enlarges
- Plaque protrudes into lumen
- Disrupts blood flow.
- Causes loss of intimal cells
- Denuded plaque surface is presented to platelets
- Causes fibrin deposition and platelet clumping
- Bare luminal surface of vessel will have exposed collagen and platelets
How does an atheromatous plaque cause arterial thrombosis
- Plaque enlarges
- Plaque protrudes into lumen
- Disrupts blood flow.
- Causes loss of intimal cells
- Denuded plaque surface is presented to platelets
- Causes fibrin deposition and platelet clumping
- Bare luminal surface of vessel will have exposed as endothelial cells lining vessel are damaged to collagen and platelets
What two of the three Virchow’s triad can apply to arterial thrombosis and under what conditions
- 3rd - Plaque is in aorta of the smoker or someone with high cholesterol / LPL as there is a change in blood constituents
(book didn’t mention the other one lol)
Why is arterial thrombosis in the aorta of a smoker / high LPL self-perpetuating
Platelet growth factor contained in alpha granules causes proliferation of arterial smooth muscle cells
What do atheromatous plaque mostly consist of
Arterial smooth muscle cells
What is the first layer of a thrombus made of
Platelets
What is and how does the second layer of a thrombus develop
- Red blood cells
2. Precipitation of fibrin meshwork traps red blood cells above platelet layer
What is the alternating layer of a thrombus called
Lines of Zahn
In which direction will the thrombus grow in
Direction of the blood flow - propagation
Why does an atheroma not occur in veins
Low pressure
How does venous thrombosis occur
- Presence of valves causing disturbances or exposed to trauma
2
How do venous thrombosis occur
- Blood pressure falls during surgery or heart attack slowing blood flow
- Venous return slows down due to lack of calf muscle contractions (DEEP VEIN THROMBOSIS)
What symptoms would I be looking for in people with arterial thrombosis
- Loss of pulse distal to thrombus
2. Signs of impaired blood supply (cold, ,pain and pale in area)
What symptoms would I be looking for in individuals with venous thromboses
Area becomes swollen, tender and red as blood is still being taken to site but not drained by veins.
Why is the site tender during vein thromboses
Because ischaemia is developing in vein wall
How do myocardial infarctions result in a death
Thrombus formation in coronary arteries
How does a thrombus lead to a stroke
Forms in cerebral vessel
What three things can happen to a thrombus
- Resolve
- Organised into scar by macrophages (clear thrombus) and fibroblasts (collagen)
- Intimal cells of vessel proliferate and capillaries grow into thrombus, recanalising the occlusion
- Death (occludes vital organ)
- Embolism
What is an embolism
Mass material in circulatory system that can get lodged in vessel and block lumen
How are most embolisms caused
By thrombus
Where do most venous thromboses form
Leg veins (95%) / pelvic veins / Intracranial sinuses
How does a pulmonary embolism form
Thromboses from areas where a venous thromboses has occurred will enter pulmonary system
Can an organised thrombus cause a pulmonary embolism
Yes but it is not severe if the thrombus is small but these are permanent and may cause small respiratory deficiency
Can an organised thrombus become severe
Yes, due to an accumulation of small, organised thrombus forming in long-term
What is an accumulation of tiny embolic events in the pulmonary system going to lead to
Damage - idiopathic pulmonary hypertension
What is the result of 2nd class embolisms in the pulmonary system
Acute respiratory and cardiac problems
What are the symptoms of 2nd class pulmonary embolisms
Chest pain
Shortness of breath
Why can a pulmonary embolism cause shortness of breath
Occluded vessel supplying lung infarcting the area
What is the long-term effect of 2nd class pulmonary embolisms
Recurrent episodes even if most people recover and lung function is impaired
What do 3rd class pulmonary embolisms result in
death
Where do 3rd class pulmonary embolisms come from
Leg veins (have same shape as the vessels they arose from)
Where are thrombi in 3rd class embolisms found
At bifurcation of a major pulmonary artery
Where do systemic embolisms arise from
Arterial system (heart or atheromatous plaque)
Where may a thrombi form in the heart
Areas of cardiac muscle that have died due to myocardial infarction
How would a thrombi form in the heart
Loss of normal endothelial lining and exposure of underlying collagen to platelets
Dead myocardium disrupts blood flow
What condition may cause thrombosis within the heart
fibrillation
How does atrial fibrillation cause a thrombi to form
stagnates blood in atrial appendages, when heart rhythm normalises, fragment breaks off
In what chamber of the heart to emboli originate from
left atrium or left ventricle
What is the consequence of the emboli originating from the left ventricle and atrium
Can travel to anywhere in the systemic circulation (e.g. brain vessels)
Where may a large emboli from the heart lodge at
bifurcation of aorta cutting supply to lower or upper limbs (needs quick diagnosis before it can’t be reversed)
What is the effect of smaller emboli
- lodge in peripheral vessels
2. Cause gangrene in fingers
What drug stops platelet aggregation
Aspirin
Define infarction
reduction in blood flow and subsequent death of cells
What is the impact of a small emboli travelling to the kidney
It asymptomatic
Causes death in area distal to site of impaction
What is the result of an emboli travelling to the intestines
Death of whole sections of bowel due to superior mesenteric artery block
What is an embolic atheroma
Fragments of atheromatic plaque embossing in the lower limbs (e.g. causing ischaemic toes)
What is a platelet emboli
Platelet deposition in early stages of atheroma formation can break off
Are platelet emboli dangerous
No unless they enter the brain vessels = TIA
What are fat embolisms
Severe trauma to long bones causes fat from marrow to release into circulatory systems.
What are gas embolisms
When we go from high-to-low pressure environments
Nitrogen bubbles form during decompression and enter bones/joints (pain)
What is an amniotic embolism
During labour, increased pressures in the uterus causes amniotic fluid to travel into the circulation and LODGE into the lungs (pulmonary embolism)
What is a tumour embolism
Tumour fragments break off (not a big deal)
