The surgical results of bioprosthetic aortic valve replacement in the 1960s and 1970s were not very satisfactory. The search for the ideal substitute for the diseased aortic valve led Donald Ross to develop the concept of the aortic allograft in 1962 and the pulmonary autograft in 1967 for subcoronary implantation, and later, in 1972, as a full root for replacing the aortic root in the infected aortic valve with a root abscess.