Stroke patients could benefit from earlier blood thinning treatment

The OPTIMAS study, funded by us, found that giving blood thinning treatments in the first few days after a stroke – rather than delaying treatment – is safe and effective for patients, even for those who had a more severe stroke.

Atrial fibrillation is a heart rhythm disturbance that affects many people as they get older. It results in an irregular heartbeat, which can lead to a clot forming inside the heart. This clot can travel to the brain, blocking its blood supply and causing a stroke.  

More than 1.6 million people in the UK have been diagnosed with AF – and they are five times more likely to have a stroke than people without AF. People with AF who have had a stroke have an increased risk of having another, but this risk can be reduced by taking anticoagulants.

'Rare but dangerous' side effects

However anticoagulants come with the rare but dangerous side effect of bleeding into the brain, and there is a lack of evidence about when is best to start taking them after a stroke. Current UK guidelines are varied, suggesting that those who have had a moderate or severe stroke should wait at least five days before starting blood thinning treatments.

To tackle this question, David Werring, Professor of Clinical Neurology at University College London, and a team of researchers investigated the impact of early compared to delayed anticoagulant treatment.

The team analysed 3,621 AF patients who had had a stroke between 2019 and 2024, across 100 UK hospitals. Half of the participants began anticoagulant treatment within 4 days of their stroke (early), and the other half started treatment 7-14 days after having a stroke (delayed). Patients were followed up after 90 days to assess several outcomes including whether they went on to have another stroke and whether they experienced bleeding in the brain.

Both the early and late groups experienced a similar number of recurrent strokes. Early treatment was found to be effective and did not increase the risk of a bleed into the brain.

The researchers suggest that as many as 20,000 patients each year in the UK could be treated with blood thinning medication at an earlier stage. The team believes that their findings should lead to a rapid change in clinical practice, and treatment should not be delayed for patients who have an AF-related stroke.

Solving a dilemma

David Werring, Professor of Clinical Neurology at University College London, said: “For many years, there has been a dilemma over the optimal time to start anticoagulants in people with a stroke and atrial fibrillation. Doctors typically recommend waiting up to two weeks out of fear that earlier treatment might cause bleeding into the brain. But during this time patients remain at risk of another stroke due to a further blood clot from the heart. 

“The OPTIMAS trial clearly shows that starting an anticoagulant early does not increase the risk of bleeding into the brain, even in patients with more severe strokes. We now plan to combine OPTIMAS data with that from other trials to determine whether offering anticoagulation sooner can prevent early stroke recurrence.”  

Professor Bryan Williams, our Chief Scientific and Medical Officer, said: “When treating strokes in people with atrial fibrillation, clinicians must strike a delicate balance to ensure swift treatment while minimising risk of potentially harmful side effects.

“This important study reveals that taking blood thinning medication within the first few days of a stroke does not come with heightened risk, as previously thought. These results could be transformative, making the case for earlier treatment that could help more people with atrial fibrillation avoid having another stroke, and the associated complications.”

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