a frame to be placed as an external support of a biological valved conduit containing three leaflets . this external frame , made of biocompatible metal or plastic is sutured to the outer surface of the valved conduit made of biological or biocompatible membrane or sigmoid valve root in order to maintain its natural geometry . the frame has a general cylindrical configuration , circular as viewed from above and below . from a side view however , both upper and lower ends of the cylinder present three convex curvatures joined at equidistant points of the circumference . these upper and lower curves are joined by three vertical struts , so that three large saddle shaped paraboloid gaps result . the frame is a wire - like structure that follows perfectly the anatomical shape of the three sinuses of valsalva , i . e . it corresponds to the external aspect of the line of implantation of the three sigmoid cusps below and the curved line of the sino - tubular junction above . the three vertical struts correspond to the three commissural areas . the frame is designed to be placed on the external surface of a valved conduit or a sigmoid valve root and therefore does not interfere with the natural movements of the three cusps and does not enter in contact with the circulating blood stream . the valved conduit is made of biological or biologically compatible membrane with three bulges corresponding to the three sinuses of valsalva and three leaflets .