A method and device for treating mitral regurgitation includes providing a treatment device comprising an expandable frame, and a leaflet assembly housed inside the frame. The frame has a tenting element. The treatment device is delivered to the aortic position in a patient's aortic valve, and the frame is expanded at the location of the native aortic valve, with the tenting element pushing the aortic curtain and/or anterior leaflet and/or mitral annulus of the mitral valve towards the mitral valve direction. The leaflet assembly replaces the valve function of the patient's native aortic valve.