Within weeks, Edwards was sending to Starr prototypes he had constructed in his home workshop, which was now located at the family’s summer home in Brightwood, Oregon. Edwards’s first valve had a circle frame of solid Teflon that held two Silastic flaps that functioned as leaflets.
Starr sutured the first valve using ring of Teflon cloth attached to the prosthesis. It functioned for several hours before a clot formed and blocked the Silastic flaps and the animal died. Starr and Edwards developed a method for fabricating a Teflon tube of cloth material that provided a superior means of suturing the prosthesis into the mitral annulus.
After several prototypes with Silastic flaps, Edwards and Starr decided to work on valve design that had an oscillating ball inside a cage.
In the first dog, Starr inserted a ball-in-cage valve prosthesis into the mitral position. It was a spectacular success and the dog survived vigorously for months, with normal cardiovascular physiology. However, the inventors achieved long-term success with the ball-in-cage valve only after they developed a method of covering the suture line with a Silastic shield.