Measurement and distribution of flexibility in cardiac valve support frames

Bioprosthetic heart valve support frames of three basic designs were injection moulded in four sizes using five plastic materials and the flexibility of each individual frame post measured. There was a regular pattern of distribution of flexibility of each individual frame post measured. There was a regular pattern of distribution of flexibility in these frames in spite of the fact that within each group of frames the dimensions of each were identical. Identically produced frames of different size showed an alteration in this pattern of flexibility and even small variations in the design of the frames resulted in marked changes in both the degree and distribution of flexibility. The plastic chosen also affected the degree of flexibility obtained also affected the degree of flexibility obtained. The flexibilities of three commercially-available support frames were also measured. The Carpentier-Edwards bioprosthesis was found to have one post more flexible than the other two in a regular pattern inherent in the design of the frame. The Angell-Shiley valve frame, because of its irregular design, displayed a totally irregular pattern. There was a regular pattern of distribution of flexibility in the Hancock porcine bioprosthesis frame. It is concluded that such differences in flexibility are a consequence of frame design, variations in the crystal structure of the plastic materials during manufacture and the choice of plastic used.