Arterial Thrombosis & Anti-platelets Flashcards
How does a atherosclerosis plaque form?
Cholesterol is pushed into the vessel walls leading to recruitment of foamy macrophages producing plaques which narrow the artery
Describe stable plaques
Hyalinised and calcified plaques cause stable angina and intermittent claudication
What is the risk of unstable plaques?
Rupture leading to thrombosis
What happens when a plaque ruptures?
Damage to endothelium exposes collagen and releases vWF and glycoprotein
Platelets adhere to the site of injury and release granules to activate coagulation and recruit further platelets
What chemicals do platelets secrete?
ADP
Thromboxane A2
Name the risk factors for artherosclerosis
Hypertension
Smoking
High cholesterol
Diabetes mellitus
What is the mechanism of action of aspirin?
Inhibits enzyme cyclo-oxygenase which is necessary to produce thromboxane A2
Describe how thromboxane A2 is produced
Arachidonic Acid –> Prostaglandin by COX1
Prostaglandin –> Thromboxane A2 by thromboxane synthase
What are the side effects of aspirin?
Bleeding
Blocks production of prostaglandins
- GI ulcers and bronchospasm
Name two ADP receptor antagonists
Clopidogrel
Prasugrel
Stop ADP binding and prevent aggregation
Name a phosphodiesterase inhibitor
Dipyridamide
Reduces cAMP which is a secondary messenger in platelet activation
Name a GP IIb/IIIa inhibitor
Abciximab
Inhibits aggregation by blocking glycoprotein receptors
When are GP IIb/IIIa inhibitors used?
Around cardiac surgery
How long before surgery should anti-platelets be stopped?
7 days
How are anti-platelets reversed?
Platelet transfusion
