by Poppy Tombs, University College London

Time-to-event curves of the primary composite outcome of recurrent ischaemic stroke, symptomatic intracranial haemorrhage, unclassifiable stroke, or systemic embolism at 90 days. Credit: The Lancet (2024). DOI: 10.1016/S0140-6736(24)02197-4

People with atrial fibrillation (AF) who have a stroke could benefit from blood thinning treatments, known as anticoagulants, at an earlier stage than is currently recommended, finds a new study led by UCL researchers.

Results from the OPTIMAS study are published in The Lancet and presented at the World Stroke Congress 2024.

The study found that it is safe and effective to give blood thinning treatments to AF stroke patients within four days of them having a stroke, rather than waiting for up to 14 days as has previously been recommended.

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.

However, anticoagulants come with the rare but dangerous side effect of bleeding into the brain, and there is a lack of evidence about when it 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, the researchers investigated the impact of early treatment compared to delayed anticoagulant treatment.

Chief Investigator, Professor David Werring (UCL Queen Square Institute of Neurology), said, “There are concerns that starting anticoagulants too early might increase the risk of bleeding into the area of the brain damaged by the stroke—especially in people with more severe strokes. However, starting them too late might leave the patient at risk of stroke due to further clots from the heart.”

The team analyzed 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 hope that their findings will enable patients to benefit from treatment in a more timely manner and prevent patients from missing out on them altogether.

Professor Werring added, “People have delayed giving these drugs previously and OPTIMAS provides reassurance that this isn’t necessary, regardless of stroke severity. This should lead to a rapid change in clinical practice, particularly for people with more severe strokes.”

Professor Nick Freemantle, Senior Investigator and Director of the UCL Comprehensive Clinical Trials Unit (CCTU) that coordinated the trial, said, “The benefits are that patients are quickly given the definitive and effective long-term stroke prevention treatment instead of waiting, which could lead to the treatments not being started at all—especially if patients are discharged from hospital.”

Professor Bryan Williams, Chief Scientific and Medical Officer at the British Heart Foundation, who is also based at UCL Institute of Cardiovascular Science, noted, “When treating strokes in people with atrial fibrillation, clinicians must strike a delicate balance to ensure swift treatment while minimizing the 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.”

More information: David J Werring et al, Optimal timing of anticoagulation after acute ischaemic stroke with atrial fibrillation (OPTIMAS): a multicentre, blinded-endpoint, phase 4, randomised controlled trial, The Lancet (2024). DOI: 10.1016/S0140-6736(24)02197-4

Journal information:The Lancet

Provided by University College London