A method for implanting a prosthesis centrally within a curved lumen includes loading a prosthesis into a delivery sheath, advancing the sheath in a patient towards the curved lumen to place at least the proximal end of the prosthesis within the curved lumen, and centering the proximal end of the prosthesis and/or the distal end of the sheath within the curved lumen. In a first advancing step, the outer catheter containing the inner sheath is advanced together towards the curved lumen to a location proximal of the curved lumen and, in a second advancing step, the inner sheath containing the prosthesis is advanced into the curved lumen to place at least the proximal end within the curved lumen while the outer catheter substantially remains at the location. After centering, the proximal end of the prosthesis is deployed centered within the curved lumen.