Anticoagulants and atrial fibrillation

Question 1

three stages of haemostasis

Answer 1

Haemostasis: the stopping of bleeding – 3 stages:

1. Vascular spasm – vessels that have been cut, spasm to stop blood coming out
2. Platelet aggregation and plug formation – platelets clump together to plug the hole
3. Coagulation (thrombus, clot) – clot forms on top

Question 2

Explain how low dose aspirin exerts its antiplatelet effect

Answer 2

inhibits cox 1 production thrombaxane a 2 and reduces platelet aggregation

Question 3

Understand the difference between a thrombus and an embolus

Answer 3

Thrombus: clot which forms in a vessel and remains there
Embolus: clot which forms in one location and travels to another location in the CVS

Question 4

Heparin:

Answer 4

• Inactivates clotting factors IIa (thrombin) and Xa by binding to antithrombin III
• Heparin, Heparin sodium (inj)

Question 5

Warfarin

Answer 5

Vitamin K antagonist
• Coumarin anticoagulant which inhibits the synthesis of vitamin K dependent clotting factors (II, V, VII, X)
• Coumadin, Marevan (tab

Question 6

Dabigatran

Answer 6

Direct thrombin inhibitor
• Reversibly inhibits thrombin, preventing conversion of fibrinogen to fibrin (preventing thrombus formation)
• DOAC/NOAC
• Pradaxa (cap)

Question 7

Apixaban

Answer 7

Factor Xa inhibitor
• Selectively inhibits factor Xa
• DOAC/NOAC
• Eliquis (tab)

Question 8

Rivaroxaban:

Answer 8

Factor Xa inhibitor
• Selectively inhibits factor Xa
• DOAC/NOAC
• Xarelto (tab)

Question 9

warfarin monitoring

Answer 9

• Monitor INR (International Normalised Ratio): target 2-3
• Monitor it every 2nd dose in the beginning, then every 4 weeks once stable
• Warning signs of bleeding/INR too high: gum bleeding, nose bleeds, red/dark brown urine, unexplained bruising

Question 10

Rivaroxaban, Apixaban monitoring

Answer 10

no monitoring of INR required. Watch for signs of bleeding though. No antidote available

Question 11

Dabigatran monitoring

Answer 11

no monitoring of INR required. Watch for signs of bleeding. Antidote available

Question 12

Warfarin drug interactions:

Answer 12

• Aspirin: increases bleeding risk
• NSAIDS e.g. Ibuprofen
• Paracetamol
• SSRIs
• Statins
• St John’s wart
• Thyroid hormones
• Gingko Biloba
• Garlic, ginger, celery, cranberry juice, green tea, aniseed

o Antidote is available: Vitamin K, fresh frozen plasma, Prothrombinex-VF
o Avoid a low vitamin K diet – eat a normal, balanced diet

Question 13

what is AF

Answer 13

• Cardiac dysrhythmia
• Irregular, rapid heart rhythm
• Disorganised electrical activity in the atria
• Atria quiver/fibrillate/beat chaotically/irregularly (faster than 300x/minute)
• No effective atrial contraction
• Ventricular rate ~150-180bpm and irregular
• Can lead to blood clots
• Can be asymptomatic or cause palpitations, SOB, weakness

Question 14

Rhythm control

Answer 14

with reversion to/maintainance of sinus rhythm with cardioversion, catheter ablation and antiarrhythmic therapy. Doesn’t deal with cause of AF though so it may return

Question 15

Rate control

Answer 15

control of ventricular rate by slowing conduction rate of the AV node and increasing refractory period of the AV node with antiarrhythmic drugs e.g. atenolol, digoxin, verapamil

Question 16

CHADS2 score

Answer 16

stroke risk assessment in people with non-valvular AF
•	Congestive Heart Failure (1)
•	Hypertension (1)
•	Age >75 (1)
•	Diabetes mellitus (1)
•	Stroke or TIA (2)