• All people with atrial fibrillation (whether paroxysmal, persistent, or permanent) should be offered antithrombotic treatment to reduce their risk of stroke.
• Offer either aspirin or warfarin, without delay, after confirming a diagnosis of atrial fibrillation.
• The choice of either aspirin or warfarin should be based on the person's risk of stroke — see Which antithrombotic treatment.

These recommendations are based on the National Institute for Health and Clinical Excellence (NICE) guideline Atrial fibrillation: national clinical guideline for management in primary and secondary care [National Collaborating Centre for Chronic Conditions, 2006].

Antithrombotic treatment for all people with atrial fibrillation (AF)

• AF is an independent risk factor of stroke; the annual risk for stroke is five to six times higher in people with AF than in people in sinus rhythm.
• Strokes that occur in association with AF are more likely to result in greater mortality, morbidity, and disability and longer hospital stays than strokes that occur in people without AF.
• Good evidence indicates that antithrombotic treatment reduces the risk of stroke in all people with AF.

Starting antithrombotic treatment after a diagnosis of AF

• Provided that the person has no contraindications to antithrombotic treatment (such as uncontrolled hypertension), NICE states that treatment should be started as soon as possible after a diagnosis of AF to minimize the risk of stroke.
• Stroke risk stratification can be easily performed in primary care on the basis of clinical criteria; therefore, a primary healthcare professional should not delay antithrombotic treatment by waiting for a cardiology opinion.

Antithrombotic treatment compared with placebo or no treatment

• After reviewing the evidence, NICE concluded that treatment with warfarin or an antiplatelet drug is more effective than placebo or no treatment in the prevention of cardioembolic stroke in people with AF.
• Two systematic reviews found evidence that aspirin was associated with a statistically non-significant reduction in stroke risk. However, a statistically significant risk reduction in a combined outcome of stroke, myocardial infarction, or vascular death was seen.
• Three systematic reviews found evidence that compared with placebo, warfarin significantly reduced the risk of stroke by two-thirds in people with AF. Compared with placebo, warfarin was associated with an increased risk of extracranial bleeding, but there was no increased incidence of intracranial bleeding.