Antiplatelet And Anticoagulant Flashcards
Define thrombosis
Pathological formation of intravascular blood clot
In vein or artery
Characterised by lines of Zahn (if large vessel) and attachment to vessel wall
Describe Virchows triad
Things that cause thrombosis
1. Disruption of blood flow (stasis)
2. Endothelial cell damage
3. Hypercoaguable states
Example of
1. Disruption of blood flow
Immobilisation (bed rest)
Cardiac wall dysfunction
Aneurysm
Atrial fibrillation
Left atrial dilation due to mitral stenosis
Example of
2. Endothelial cell damage
Atherosclerosis - ruptured plaque
Vasculitis
Oxidised LDL
Cigarette smoke
Cytokines
Example of
3. Hypercoagulable states
Excessive procoagulant factors
Inherited (AT3 deficiency)
Classics presentation is recurrent DVTs or DVTs at young age
Drug to treat ischaemic stroke
Alteplase - administered 4.5 hours of symptom onset
Treatment with aspirin initiated 24 hours after thrombolysis
Describe venous thrombus
Most common cause is stasis of blood
Most common site of deep veins of lower limb
Red, swollen, painful leg
Can dislodge to the lungs causing a pulmonary embolism
Treatment of venous thrombus
Rivaroxaban
Warfarin or other anticoagulant
Describe arterial thrombosis
Due to endothelial damage related to turbulent blood flow at bifurcation or over atherosclerotic plaques in high velocity vessels
Treatment for arterial thrombosis
Inhibitors of platelet aggregation - aspirin
Describe pulmonary embolism and most likely cause
Intravascular mass that travels and occluded pulmonary blood vessels
- cause is a dislodged thrombus
3 stages of platelet activation
Adhesion
Release reaction
Aggregation
When platelets undergo shape changes they degranulate …
Release mediators ADP
Thromboxane A2 - from platelet cyclooxygenase
Calcium
What does ADP do
Induced expression of GP2b/3a (essential receptor for aggregation of platelets) and fibrinogen which acts as linker molecule in the developing clot
What is TXA2
A vasoconstrictor that also promotes platelet aggregation
Thrombin functions
Act on fibrinogen to produce fibrin monomers
Activates fibrin stabilising factor 13 (strengthens blood clot)
What switches off thrombin
Natural anticoagulant antithrombin3
- limits clot formation
Functions of plasmin
Breaks down clot
Cleaves fibrin and fibrinogen into degradation products
Degrades some clotting factors
Blocks platelet aggregation
3 main classes of thrombus treatments
Anticoagulants - factor Xa inhibitors
Antiplatelets - aspirin
Fibrinolytic agents - Alteplase
4 classes of anticoagulant drug
- Selective factor Xa inhibitor - apixaban
- Direct thrombin inhibitors - dabigatran
- Heparin and low MW heparins
- Vitamin K antagonists - Warfarin
Treatments for venous thromboembolism
Apixaban
If contraindicated - low MW heparin
Or
LMWH with vitamin K antagonist for at least 5 days until INR achieved
DOACs: dabigatran etexilate mechanism of action
Reversible inhibitor of thrombin
DOACs: apixaban mechanism of action
Reversible inhibitor of activated factor X
Prevents thrombin generation
Prevents thrombus development
Indications of apixaban, dabigatran etexilate, edoxaban and rivaroxaban
Prevention of stroke
Secondary prevention of DVT
