AF and anticoagulants Flashcards
How to low dose aspirins inhibit platelet aggregation
LDA are anti-platelets
Block COX1 from turning arachidonic acid into thromboxane A2 –> stop platelet aggregation and thrombus formation
- effect is irreversible as platelets dont have nuclei (cant regenerate COX1)
- however, vascular tissue cells have nuclei –> can continue to regenerate COX2 –> promotes vasodilation and inhibits platelet aggregation
How do we read INR?
Higher INR, higher bleeding risk
target INR - 2 - 3
Difference between thrombus and embolus?
Thrombus - clot that forms within a vessel and doesn’t move
Embolus - a fragment of a clot that has vessel, but broken off and travelled to another area within the circulation
4 anticoagulants
Warfarin
Apixaban
Dabigatran
Rivaroxaban
What are 3 MOA of anticoagulants?
Warfarin – prevents clotting factor 2, 7, 9, 10 synthesis –> reduced clothing factor availability –> reduced ability to convert prothrombin into thrombin
Dabigatran –> blocks thrombin activity stops conversion of fibrinogen into fibrin reduced clotting ability.
Apixaban and rivaroxaban –> blocks clotting factor activity –> stops prothrombin conversion into thrombin
What anticoagulant has an anecdote and what is it called?
Dabigatran - idarucizumab
- binds to dabigatran and neutralises effects on thrombin
How to switch between NOAC and warfarin
Warfarin –> NOAC
1. Stop warfarin
2. wait till INR is below
3. start NOAC
NOAC –> warfarin
2. Begin warfarin
2. wait till INR is below
3. stop NOAC
How do we treat AF?
Rhythm control - return to sinus rhythm
- antiarrythmic therapy
- cardioversion
- catheter ablation
Rate control - slow conduction rate and increase refractory period of AV node
- Beta-blockers e.g. atenolol
- CCB e.g. verapamil
- cardiotonic glycoside e.g. digoxin - increases sodium retention within cells –> increased calcium intake –> slower conduction rate/increased refractory period
Food-drug interactions with warfarin
Garlic, grapefruit
black licorice
alcohol
Warfarin pt education points
- always take the same brand of tablets
- require regular blood tests (for INR testing)
- eat a normal diet with stable Vitamin K intake
- avoid excessive alcohol or cranberry juice intake
What is AF and what complications can it lead to?
AF is a form of dysrhythmia - abnormal cardiac rhythms within the atria caused by fast and disorganised atrial electrical activity –> fast and irregular pulse
Fast and irregular pulse —> quivering and squirming –> clot formation
AF treatment based on type of AF
Non-valvular - NOAC or warfarin
Valvular - warfarin (due to availability of research)
Do not use low dose aspirins (only affects platlets)
