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MedicineCardiology

Thromboembolism prevention and anticoagulant selection in atrial fibrillation

THE CONTEXT
Loss of atrial contraction and left atrial dilatation promote blood stasis and left atrial appendage thrombus, creating a risk of stroke and systemic embolism in atrial fibrillation (AF).

Anticoagulation around cardioversion

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For cardioversion of AF lasting more than 24 hours, direct oral anticoagulants or warfarin may be used.
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Start anticoagulation at least 3 weeks before cardioversion and maintain it for at least 4 weeks after successful cardioversion.
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Consider long-term anticoagulation according to the CHA₂DS₂-VA score, irrespective of cardioversion success.

Balancing stroke and bleeding risks

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Balance stroke risk against anticoagulant-related bleeding risk. AF secondary to mitral stenosis always requires a vitamin K antagonist because of its high thrombotic risk.
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The CHA₂DS₂-VA score assesses stroke risk, while HAS-BLED identifies higher bleeding risk. Higher bleeding risk requires optimisation of risk factors and closer monitoring during anticoagulation.
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After adjustment for the CHA₂DS₂-VA score, paroxysmal AF carries a stroke risk similar to persistent AF. Embolism risk relates only weakly to episode frequency and duration, so stroke prevention guidance does not distinguish paroxysmal, persistent and permanent AF.

Direct oral anticoagulants

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Rivaroxaban, apixaban and edoxaban inhibit factor Xa; dabigatran directly inhibits thrombin. These direct-acting oral anticoagulants have largely replaced warfarin for stroke prevention in AF.
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They are at least as effective as warfarin in preventing thrombotic stroke and generally have a lower major bleeding risk.
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Additional advantages include no requirement for monitoring and fewer drug and food interactions.
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