DIrect Oral Anticoagulation and Bioprothesis Aortic Valve

Early antithrombotic management of patients who have undergone aortic valve replacement using a bioprosthesis remains a source of medical concern. The optimal antithrombotic strategy early after surgery remains controversial due to lack of high-quality evidence. Some observational studies support the use of vitamin K antagonists (VKAs) compared to aspirin (ASA) to significantly reduce the risk of thromboembolism but suffer from major source of bias inherent to retrospective analyses of observational data. A small, randomized trial found that VKA for 3 months significantly increased major bleeding compared with ASA, without reducing the rate of deaths or thromboembolic events but this study was underpowered for ischemic events. There is therefore a lack of evidence demonstrating the superiority of anticoagulant treatment compared to aspirin early after bioprosthetic aortic valve surgery. Current ESC guidelines recommend that ASA or VKA should be considered for 3 months after surgical implantation of an aortic bioprosthesis. At the opposite, current AHA/ACC guidelines recommend that anticoagulation with VKA to achieve an INR of 2.5 is reasonable for at least 3 months and for as long as 6 months for patients at low risk of bleeding (IIa, level B). However, anticoagulation by VKAs is currently underused and guideline recommendations are not followed by most clinicians as VKAs have major drawbacks: narrow therapeutic window, variable dose-response in individuals, interaction with several foods and drugs.

Despite their superiority to reduce bleeding in patients with non-valvular atrial fibrillation compared to VKAs, direct oral anticoagulants (DOACs) including apixaban have not been well evaluated in the first 3 months after surgical bioprosthetic valve implantation. A small, randomized trial found that edoxaban was non-inferior to warfarin for preventing thromboembolism and the occurrence of major bleeding in the first 3 months after aortic or mitral surgical bioprosthetic valve implantation. DOAC(s) are effective in patients with atrial fibrillation and bioprosthetic valve implanted after 3 months.

Finally, there is an unmet clinical need for an alternative to ASA or VKAs, such as an anti-Xa DOAC like apixaban, as anticoagulation in patients in the first 3 months after surgical bioprosthetic valve implantation.

The purpose of this study is to compare the efficacy of apixaban and aspirin on ischemic endpoints during the first 3 months after aortic surgical bioprosthetic valve implantation excluding TAVI.