19. Thrombosis and Embolism Flashcards
What are the components of a thrombus?
Platelets
Fibrin
RBCs
What factors do endothelial cells normally produce?
Prostacyclin
Thrombomodulin
Plasminogen activator
NO
What is the function of prostacyclin?
Platelet inhibitor
What factors do endothelial cells produced when damaged?
Platelet Aggregating Factor
Plasminogen Activator Inhibitors
What factor do platelets release when they aggregate?
Thromboxane
What factors can cause endothelial damage?
Plaque in atherosclerosis Vasculitis Hypertension Turbulent flow Cigarette smoke
Why can abnormal flow predispose to thrombosis?
Platelets in contact with endothelium
Clotting factors aren’t diluted by flowing blood
Slows clotting inhibitors getting to the site
Allows build up of thrombi
Promotes endothelial cell activation
What is the most common form of abnormal flow in arteries?
Turbulence
What is the most common form of abnormal flow in veins?
Stasis
What factors can cause venous stasis?
Immobility heart failure Shock External pressure Aneurysms
Give 2 causes of primary hypercoaguability
Mutation in factor V gene
Prothrombin gene
Give 2 reasons of secondary hypercoaguability
Cancer
DIC
What are the consequences of thrombi in an artery?
Ischaemia, infarction and emboli
What consequence can a thrombus have in veins?
PE
What are the possible fates of a thrombus?
Propagation (leading to vessel obstruction)
Embolisation
Dissolution
Scarring and recanalisation of blood vessel
What are the consequences of thrombi in capillaries?
Frost bite
Necrosis and ulceration
How does COVID-19 cause vasoconstriction and thrombosis?
Uses ACE-2 enzyme to get into the cell, which inactivates the enzyme
High ACE and angiotensin 2 cause vasoconstriction and thrombosis
What things can cause thrombi to form in the heart?
Post MI
Valves in infective endocarditis
LA in atrial fibrillation
What effect does a massive pulmonary embolus have?
Wedges in pulmonary artery and causes sudden death
What effect does an intermediate pulmonary embolus have?
May cause infarction
Necrosis will only happen if circulation is already compromised as lungs have dual circulation
What effect can pulmonary microemboli have?
Block small pulmonary arterioles
Cause right heart failure
Where are the most common places for systemic emboli to arise?
Left heart
Aorta
Carotids
How are air emboli created?
If the veins of head or neck are cut, air is sucked in during inspiration
What effect can an air embolus have?
Reduces heart pump function as when ventricles contract they only serve to compress air
What causes decompression sickness?
High pressure (eg. divers) cause an increase of nitrogen in body fluids Rapidly decreasing pressure cause nitrogen bubbles to form
What is the bends?
Bubbles form in muscles and joints
What is the chokes?
Oedema and haemorrhage in lungs
Ischaemia
How are fat emboli created?
Fracture of long bones
What are the symptoms of a fat embolus?
Dyspnoea and cyanosis
CNS symptoms
Petechial haemorrhages
