Study Advocates Earlier Anticoagulant Use to Prevent Repeat Strokes in Atrial Fibrillation Patients

A recent study conducted by researchers at University College London (UCL) has unveiled critical insights regarding the timing of anticoagulant treatment for patients suffering from atrial fibrillation who have experienced a stroke. The findings, published in *The Lancet* on June 26, 2025, suggest that early initiation of direct oral anticoagulants (DOACs) within four days post-stroke could significantly reduce the risk of subsequent strokes, compared to the current UK guidelines which recommend a delay of at least five days.

The research, known as the CATALYST study, encompassed data from four randomized trials involving a total of 5,441 participants across the UK, Switzerland, Sweden, and the United States. All participants had recently endured a stroke due to arterial blockage, related to their atrial fibrillation, a condition characterized by an irregular heartbeat. The study concluded that those who commenced anticoagulant therapy earlier did not experience a higher incidence of intracranial hemorrhage, a common concern with blood-thinning medications. In fact, early treatment resulted in a 30% reduction in the risk of a subsequent stroke when compared to delayed treatment.

Atrial fibrillation affects more than 1.6 million individuals in the UK, rendering them five times more susceptible to strokes than those without the condition. Current recommendations vary, but they often advocate a conservative approach due to the potential for severe complications, such as bleeding. Dr. Hakim-Moulay Dehbi, the first author of the study from the UCL Comprehensive Clinical Trials Unit, emphasized the significance of these findings: "By systematically combining the data from four clinical trials, we have identified with increased confidence that early DOAC initiation is effective."

Professor David Werring, Chief Investigator and a leading figure at UCL's Queen Square Institute of Neurology, reinforced the necessity of revising clinical guidelines based on this study. He stated, "Our new study supports the early initiation of DOACs in clinical practice, offering better protection against further strokes for a wide range of patients."

The implications of these findings extend beyond the immediate treatment of individuals with atrial fibrillation. According to Professor Bryan Williams OBE, Chief Scientific and Medical Officer at the British Heart Foundation, this study could lead to transformative changes in clinical practice, allowing for earlier and safer treatment of patients afflicted by this condition.

However, the study is not without its limitations. The timing for the initiation of anticoagulants was based on previous trial designs, which might not encompass all clinical scenarios. Furthermore, the study did not include a large cohort of patients with severe strokes, raising questions about the generalizability of the results.

The CATALYST collaboration received funding from the British Heart Foundation and a Swiss National Science Foundation grant, and it was supported by the National Institute for Health and Care Research UCLH Biomedical Research Centre.

In summary, the CATALYST study presents compelling evidence advocating for an early initiation of anticoagulant therapy in patients with atrial fibrillation who have suffered a stroke. As healthcare professionals review these findings, there is optimism that they will lead to enhanced treatment protocols that prioritize patient safety and stroke prevention.