Journals Club - Atrial fibrillation and antithrombotic treatment

Contributed by Dr Louise Newson, a GP in the West Midlands

AF:assess stroke risk
AF:assess stroke risk

Curriculum statement 15.1 Cardiovascular Problems

Key trials

  • The AFFIRM trial studied rate versus rhythm control and showed that beta-blockers were the most effective drugs for slowing heart rate in patients with AF (J Am Coll Cardiol 2004; 43: 1201-8).
  • Aspirin reduces the risk of stroke by about 22 per cent (Ann Intern Med 2007; 146: 857-67).
  • One large randomised trial found that elderly patients obtain greater net benefit from warfarin, even despite their higher risk of haemorrhage (Lancet 2007; 370: 493-503).
  • In the ACTIVE trial, the relative risk of primary events was significantly decreased in patients given clopidogrel and aspirin compared with patients receiving aspirin alone. However, the relative risk of major bleeding was also significantly increased (Lancet 2006; 367: 1903-12).
  • Despite the well-known benefit of oral anticoagulation in high-risk AF patients, anticoagulation is still underused (Semin Thromb Hemost 2009; 35: 554).
  • Patients with AF should not be given dual antiplatelet treatment for stroke prevention because of the associated increased risk of major bleeding (Int J Stoke 2010; 5: 28-9).

Evidence base

  • Clinical Knowledge Summaries on AF state that all patients with AF (paroxysmal, persistent, or permanent) should be offered antithrombotic treatment to reduce their risk of stroke (www.cks.nhs.uk/atrial_fibrillation).
  • Warfarin has been shown to reduce the risk of stroke by 32-47 per cent compared with aspirin, although at the expense of increasing the risk of haemorrhages (Cochrane Database Syst Rev 2007; 3: CD006186).
  • Publication of several randomised controlled trials and meta-analyses in recent years has improved understanding of the advantages and inconveniences of rate and rhythm control strategies (BMJ 2009; 339: b5216).
  • Aspirin is adequate for those at low risk of stroke and when warfarin is contraindicated (Chest 2008; 133: S546-92).
  • New oral anticoagulants are being developed that will not require blood monitoring. Dabigatran, a direct thrombin inhibitor, has been shown to be as good as warfarin at reducing risk of stroke, with comparable rates of haemorrhage (N Engl J Med 2009; 361; 1139-51).
  • The CHADS-2 tool has been shown to be best at estimating the risk of stroke in patients with AF (Thromb Haemost 2010; 103(3) - Epub).

Guidelines

  • NICE guidance has recommended that patients with AF should be assessed for their stroke/thromboembolic risk and anticoagulation or aspirin should be considered according to this risk (www.nice.org.uk/Guidance/CG36)
  • Atrial Fibrillation: National Clinical Guideline for Management in Primary and Secondary Care recommends antithrombotic treatment should begin as soon as possible in patients with newly diagnosed AF, unless contraindicated (www.rcplondon.ac.uk).

Contributed by Dr Louise Newson, a GP in the West Midlands

Key Points
  • AF is very common.
  • All patients with AF should receive antithrombotic treatment.
  • Most people with AF need warfarin.
  • Dual antiplatelet therapy should not be prescribed.
  • Newer anticoagulants may be introduced in the near future.

 

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