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Synthetic coumarin derivative oral vitamin K antagonist. Warfarin is an anticoagulant drug, which acts by preventing the synthesis of vitamin K dependent clotting factors (II, VII, IX and X) in the liver. There are four main indications for warfarin:

  1. Non-valvular AF.

  2. Artificial heart valve.

  3. AF associated with diseased heart valve.

  4. Thromboembolic disease (prevention or treatment) e.g. DVT, PE, stroke.

Warfarin risk/benefit analysis for patients with non-rheumatic AF

The use of warfarin must balance the risk (bleeding) with the benefit (prevention of stroke) in non-valvular AF. A useful tool is the CHA2DS2-VASc score, as demonstrated in Tables W1 and W2.1

Table W1CHA2DS2-VASc score
Table W2CHA2DS2-VASc score and annual stroke risk

Annual stroke risk is summarised in Table W2.

A score of zero is possible e.g. a 50-year-old man with non-valvular AF and no other risk factors.

Table W3CHA2DS2-VASc score and recommended action

The risk of bleeding in non-valvular AF can be calculated from the HAS-BLED score, as demonstrated in Table W4.2

Table W4Calculating the HAS-BLED score

The HAS-BLED score signifies a person's approximate annual risk of major bleeding as a percentage, as demonstrated in Table W5.

Table W5HAS-BLED score and annual risk rate of major bleeding

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