Anticoagulation Therapy in Atrial Fibrillation: A Review of the RE-LY Trial

The Randomized Evaluation of Long-Term Anticoagulant Therapy (RE-LY) trial marked a significant milestone in our approach to anticoagulation therapy in atrial fibrillation (AF). This groundbreaking study compared the efficacy and safety of dabigatran, a novel oral anticoagulant (NOAC), with the traditional warfarin. This article reviews the RE-LY trial and its transformative impact on the management of AF.

Overview and Objectives of the RE-LY Trial

Launched in 2006, the RE-LY trial emerged as a pioneering multinational randomized study. Sponsored by Boehringer Ingelheim, the trial included over 18,000 patients across 44 countries. It aimed to evaluate dabigatran’s performance against warfarin for stroke prevention in patients with non-valvular AF.

The primary objective of the RE-LY trial was to compare the rates of stroke and systemic embolism between patients receiving dabigatran and those receiving warfarin. Additionally, the study aimed to assess the rates of major bleeding, a critical consideration when prescribing anticoagulant therapy.

Dabigatran: A New Option for Anticoagulation

Dabigatran represented a significant advancement in the field of anticoagulation at the time of the RE-LY trial. As a direct thrombin inhibitor, it works by blocking thrombin, a protein crucial in the blood clotting process.

One key advantage of dabigatran is that it does not require routine blood monitoring, a necessary but burdensome requirement with warfarin. Additionally, it has fewer food and drug interactions, making it a more convenient option for many patients. The RE-LY trial aimed to test these benefits in a large, real-world population of AF patients.

RE-LY Trial Design and Methodology

The RE-LY trial adopted an open-label, randomized design. Patients with non-valvular AF and at least one risk factor for stroke were randomized to receive either warfarin or one of two doses of dabigatran (110 mg or 150 mg) twice daily.

The choice of an open-label design, while potentially introducing bias, reflected the practical difficulties of mimicking warfarin’s dosing and monitoring requirements in a double-blind trial. The researchers made concerted efforts to minimize bias, including the use of an independent committee for outcome adjudication.

Primary Findings: Stroke and Systemic Embolism

The primary outcome of the RE-LY trial was the occurrence of stroke or systemic embolism. In terms of this primary outcome, dabigatran performed impressively. The higher dose of dabigatran (150 mg twice daily) significantly reduced the risk of stroke and systemic embolism compared to warfarin, positioning it as an effective alternative for stroke prevention in AF patients.

Meanwhile, the lower dose of dabigatran (110 mg twice daily) showed similar efficacy to warfarin but had the advantage of significantly lower rates of major bleeding. These findings demonstrated that dabigatran could provide a balance between effective anticoagulation and bleeding risk, depending on the chosen dose.

Safety Outcomes: Bleeding and Other Adverse Events

Safety, especially the risk of bleeding, is a vital consideration in anticoagulant therapy. In the RE-LY trial, the rates of major bleeding were similar between warfarin and the higher dose of dabigatran, but significantly lower with the lower dabigatran dose.

Importantly, both doses of dabigatran were associated with lower rates of life-threatening and intracranial bleeding compared to warfarin. However, they also showed a higher incidence of gastrointestinal bleeding. Overall, the safety profile of dabigatran demonstrated in the RE-LY trial supported its use as a viable alternative to warfarin.

Impact on Clinical Practice and Guidelines RE-LY Trial

The RE-LY trial’s findings had a transformative impact on the management of AF. The demonstrated efficacy and safety of dabigatran led to its approval by the Food and Drug Administration (FDA) in 2010 as the first NOAC for stroke prevention in AF patients.

The results of the RE-LY trial also influenced several clinical guidelines. For example, the American Heart Association and the American Stroke Association updated their guidelines to include dabigatran as an alternative to warfarin for stroke prevention in AF.

Future Research Directions and the Era of NOACs

The RE-LY trial spurred further research into NOACs, paving the way for subsequent trials of other NOACs such as rivaroxaban, apixaban, and edoxaban. These trials have generally confirmed the benefits of NOACs over warfarin, including similar or superior efficacy and a lower risk of intracranial bleeding.

The RE-LY trial also opened the door to ongoing investigations into optimizing the use of NOACs. Future research directions include exploring the ideal doses for various patient subgroups, examining the long-term safety of these drugs, and developing strategies to manage bleeding complications.

Beyond Stroke Prevention: Other Implications of the RE-LY Trial

The implications of the RE-LY trial extend beyond stroke prevention. By showcasing the benefits of a novel anticoagulant, the trial has stimulated the development of new anticoagulants and antiplatelet drugs for other indications, such as venous thromboembolism and acute coronary syndromes.

Moreover, the trial’s impact on clinical practice has implications for patient quality of life. The convenience of dabigatran compared to warfarin, such as the lack of need for routine blood monitoring and fewer food and drug interactions, can enhance treatment adherence and patient satisfaction.

Effect on Health Economics

The RE-LY trial not only brought about a change in the therapeutic landscape but also had significant implications for health economics. The costs associated with the use of anticoagulants involve not just the price of the drugs but also the costs of monitoring, managing complications, and treating the outcomes of stroke.

Dabigatran, despite being more expensive than warfarin at face value, demonstrated potential cost-effectiveness when these factors were taken into account. By eliminating the need for routine monitoring and by reducing the rate of strokes and systemic embolisms, dabigatran proved to be an economically viable option in long-term anticoagulant therapy.

However, the affordability of NOACs like dabigatran in different regions and health systems remains a concern. Further research is needed to fully understand the economic impact of NOACs across various global health contexts.

Patients’ Perspective and Quality of Life RE-LY Trail

One of the notable aspects of the RE-LY trial was the impact on patients’ quality of life. For patients, the convenience of dabigatran was a significant advantage. Dabigatran’s fixed-dose regimen eliminated the need for constant monitoring and dose adjustments, which are necessary with warfarin.

In addition, patients did not have to worry about dietary restrictions or numerous drug interactions that are common with warfarin therapy. This benefit greatly simplified their treatment and improved adherence to the medication, significantly improving their quality of life.

Further studies have supported these findings, with patients reporting higher satisfaction with dabigatran compared to warfarin. The introduction of dabigatran and other NOACs represents a shift towards patient-centric care in the management of AF.


In conclusion, the RE-LY trial has had far-reaching impacts on the landscape of anticoagulation therapy in atrial fibrillation. It validated the use of dabigatran, a novel oral anticoagulant, demonstrating its efficacy and safety profile in comparison to warfarin.

These findings have shifted clinical practice guidelines, prompted further exploration of NOACs, and improved patients’ quality of life. As the medical community continues to optimize the management of AF, the RE-LY trial stands as a watershed moment in our understanding of anticoagulant therapy.

This article underscores the significance of the RE-LY trial and its findings. However, the ever-evolving landscape of AF management necessitates ongoing research to refine our understanding and to continue improving patient outcomes. As we move forward, the lessons from the RE-LY trial will continue to guide our path.




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