This single heart leaflet or cusp was used to replace or supplement a compromised natural leaflet. One, two or three leaflets could be surgically implanted. The leaflets were made of polypropylene mesh and impregnated with silicone rubber. Charles A. Hufnagel, MD, the inventor believed polypropylene leaflets would be a better design solution than the ball and cage model because it provided better dynamics. He acknowledged that only a few of these leaflets worked well, "those leaflets were the only leaflets, I think, that really lasted for any significant length of time." The single leaflets were later used to develop a trileaflet valve which looked similar to a natural human valve.
Dr. Charles Hufnagel, (1916-1989) graduated in 1941 from Harvard Medical School. While a resident at Boston’ Children’s Hospital he worked with pioneer cardiac surgeon Dr. Robert Gross. In 1950 he left the Peter Bent Brigham Hospital in Boston to becoame the Director of Georgetown University Medical Research laboratory. In September 1952, he implanted the first artificial heart valve which consisted of a ball of plastic inside a chambered tube. Hufnagel also made significant contributions to the development of the modern heart-lung machine.