ELM13: Acute coronary syndromes Flashcards
What are ACS?
Disorders with chest pain that radiates
Not relived by rest
Caused by coronary artery thrombosis Involve cardiac ischaemia
What are the three main categories of ACS?
Unstable angina
NSTEMI
STEMI
What is the pain treatment for ACS?
Opiods
What is the treatment to reduce cardiac workload and improve blood supply in ACS?
Beta blocker
GTN
What is the treatment to prevent further thrombosis in ACS?
Aspirin
Ticagrelor
Heparins
What are the treatments for reperfusion in ACS?
PCI
CABG
Thrombolysis
What is haemostasis?
Preventing blood loss after vessel damage
Coagulation platelet aggregation and vasoconstriction
What is thombosis?
Pathological
DVT
Embolism
Stroke
Heart attack
What is a thrombus?
A pathogenic blood clot attached to cell wall
Traps platelets and blood cells
What has a major role in venous thrombosis?
Coagulation
What has a major role in arterial thrombosis?
Platelet aggregation
What is an embolus?
Complication of a thrombus
Part or whole detaches from wall and travels through vessels
Causes blockage
What is the main aim of drugs treating thrombus?
Inhibit formation without preventing haemostasis
What are the three main targets of modifying the thrombosis process?
Modify coagulation
Modify platelet aggregation
Modify clot thrombus breakdown
What are heparins in relation to thrombosis?
Modify coagulation to prevent thrombosis
Where are heparins found?
Liver
Lungs
Mast cells
What is the role of heparins?
Inhibit action of thrombin and factors Xa and IXA
Increases rate of formation of antithrombin III thrombin complex
What is required for heparins to work?
Antithrombin III
Factor IIA
What are some other actions of heparins?
Reduce platelet aggregation
Reduces platelet numbers
Influences lipid metabolism
What are some clinical uses of heparins?
Venous thrombosis and embolism
After heart attack or stroke
Reduce DVT risk after orthopaedic surgery
What is thrombin?
Proteolytic enzyme
Converts fibrinogen to fibrin
How is actin thrombin formed?
Cleavage of prothrombin by factor Xa
What is fondaparinux?
Synthetic sulphated mucopentasaccharide
Similar action to LMW heparins with less side effects
What are some issues with heparins?
Not absorbed orally
Allergic reactions
Individualised dose
Haemorrhage risk
How is warfarin administered?
Orally
What is warfarin usually used for?
Venous thrombo embolism
Stroke prevention
How does warfarin work?
Similar structure to vitamin K
Antagonises its role in some clotting factors
What are some problems with warfarin?
Slow onset
Activity influenced by vitamin K
Exists as R S isomers
Haemorrhage risk
Teratogenic
What drug is a direct inhibitor of thrombin?
Dabigatran
What drug is an inhibitor of factor Xa?
Rivaroxaban
What are the benefits of using newer drugs like dabigatran and rivaroxaban as treatment?
Don’t need monitoring ‘Easier to use
What are platelets?
Derived from megakaryocytes
Fragments of cytoplasm with no nucleus
What are some stimuli of platelet aggregation and activation?
ADP
TxA2
Thrombin
What is the role of TxA2 in platelet aggregation and adhesion?
- Synthesised from arachidonic acid by cyclo-oxygenase
- Activated platelets synthesise TxA2
- Released from platelets and increases levels of IIb and IIa receptors
What is the process of inhibition of aggregation?
Endothelium releases prostacyclin
What is the first mechanism of antiplatelet drugs using aspirin?
- Irreversibly blocks platelet COX enzyme
- Reduces TxA2 synthesis
W
hat are some unwanted side effects of aspirin?
Extended bleeding time
Indigestion
Allergy
Asthma attacks
Reyes
What is the second mechanism of antiplatelet drugs?
Modulating expression of glycoprotein IIb/a receptors
What is an example of a drug using the second mechanism?
Clopidogrel Inhibits glycoprotein IIa/b expression on platelets
Blocks ADP receptor irreversibly
What was the PLATO trial?
Compared clopidogrel with ticagrelor
Ticagrelor superior
What are some unwanted side effects of clopidogrel and ticagrelor?
Extended bleeding time GI tract problems
Headaches
Gout T
Breathless ness T
What is the third mechanism of antiplatelet drugs?
Raise cAMP levels
What is an example of a drug using the third mechanism?
Dipyridamole
Phosphodiester inhibitor that prevents cAMP breakdown in platelets
What are some side effects of dipyridamole?
GI tract problems
Headaches
Muscle pain
Flushing
What are some treatments causing reperfusion?
PCI
CABG
Thrombolysis
What are some properties of PCI?
Rapid
Safe
Specialist centre
What are some properties of thrombolysis?
Very rapid
Risky
Little equipment
