Antithrombotic therapy for atrial fibrillationBMJ 2002; 325 doi: https://doi.org/10.1136/bmj.325.7371.1022 (Published 02 November 2002) Cite this as: BMJ 2002;325:1022
- Gregory Y H Lip,
- Robert G Hart,
- Dwayne S G Conway
Atrial fibrillation is the commonest sustained disorder of cardiac rhythm. Although patients often present with symptoms caused by haemodynamic disturbance associated with the rhythm itself, the condition carries an increased risk of arterial thromboembolism and ischaemic stroke due to embolisation of thrombi that form within the left atrium of the heart. Presence of the arrhythmia confers about a fivefold increase in stroke risk, an absolute risk of about 4.5% a year, although the precise annual stroke risk ranges from <1% to >12%, according to the presence or absence of certain clinical and echocardiographically identifiable risk factors.
From trial data, patients with paroxysmal atrial fibrillation seem to carry the same risk as those with persistent atrial fibrillation. The same criteria can be used to identify high risk patients, although it is unclear whether the risk is dependent on the frequency and duration of the paroxysms.
Randomised controlled trials have shown the benefit of warfarin and, to a lesser extent, aspirin in reducing the incidence of stroke in patients with atrial fibrillation without greatly increasing the risk of haemorrhagic stroke and extracranial haemorrhage. However, anticoagulant therapy is still underprescribed in patients with atrial fibrillation, particularly in elderly patients, who stand to benefit most
Evidence from clinical trials
It is well established that antithrombotic therapy confers thromboprophylaxis in patients with atrial fibrillation who are at risk of thromboembolism. A recent meta-analysis of antithrombotic therapy in atrial fibrillation showed that adjusted dose warfarin reduced stroke by about 60%, with absolute risk reductions of 3% a year for primary prevention and 8% a year for secondary prevention (numbers needed to treat for one year to prevent one stroke of 33 and 13, respectively). In contrast, aspirin reduced stroke by …