Comparison of Anti-Thrombotic Treatments Between Aspirin and Warfarin During Initial Six Months After Bioprosthetic Heart Valve Replacement

Inclusion Criteria: 1. Aged ≥ 19 years with successful surgical bioprosthetic valve replacement 2. Bioprosthetic heart valve in aortic or mitral valve positions, for a day postoperatively 3. The patient or guardian agrees to the study protocol and the schedule of clinical follow-up, and provides informed, written consent, as approved by the appropriate Institutional Review Board/Ethical Committee of the respective clinical site. Exclusion Criteria: 1. Mechanical valve in any heart valve position 2. Previous hemorrhagic stroke within the last 3 months 3. Clinically overt stroke within the last 3 months 4. Current need for anticoagulation (i.e. atrial fibrillation, deep vein thrombosis) 5. Unstable postoperative conditions at index point (i.e. requirement mechanical hemodynamic support, disabling complications, stroke \[ischemic, embolic\], hemorrhagic stroke) 6. Hypersensitivity to the main component or constituents of aspirin or vitamin K antagonist 7. Pregnant or lactating women