Methods and apparatus for manufacture of valve flaps for cardiac valve prostheses

Claim 2

A process for the manufacture of valve flaps (10) for cardiac valve prostheses (1), in which prostheses the said flaps (10) are anchored to a support frame (2) along respective edges (10a), the process involving starting from sheets of incompletely fixed biological tissue (90), including portions which can define the said valve flaps (10), said process comprising the operations of: -providing forming means (29) for the said sheets of biological tissue (90) capable of separating from each other in a substantially fluid-tight manner the opposite faces of said valve flap defining portions, -applying the said sheets of biological tissue (90) to the said forming means (29), -generating a fluid pressure difference between the opposite separated faces of the said portions to produce the deformation of the portions towards a conformation substantially identical to the conformation of the valve flaps (10) when mounted in the prosthesis (1), and -effecting the final fixation of the biological tissue whilst the said portions are maintained in said conformation substantially identical to the conformation of the valve flaps (10) when mounted in the prosthesis (1), whereby each of the said portions assumes, in a substantially stable manner by virtue of the fluid fixation, said conformation substantially identical to the conformation of the valve flaps (10) when mounted in the prosthesis (1), characterised in that: -said sheets of biological tissue (90) are retained on said forming means (29) leaving said respective edges (10a) free from retention, whereby weakening of the biological tissue close to said edges (10a) is avoided, - the said sheets of biological tissue (90) are removed from the said forming means for subsequent mounting in the support frame (2).

Claim 3

A process according to Claim 1, characterised by the fact that the final fixation of the biological tissue is effected by means of a fixation fluid (L) brought into contact with at least one of the opposite faces of the said portions of biological tissue.

Claim 4

A process according to Claim 2, characterised by the fact that the said pressure difference is generated by pressurising the fixation fluid (L) and bringing the pressurised fixation fluid (L) into contact with one of the opposite faces of the said portions of biological tissue.

Claim 5

A process according to Claim 3, characterised by the fact that the said portions of biological tissue are substantially immersed in the fixation fluid (L) and by the fact that the said pressure difference is established between the bodies of fixation fluid which are in contact with the opposite faces of the said portions.

Claim 6

A process according to Claim 4, characterised by the fact that the magnitude of the said pressure difference and the length of time for fixation of the biological tissue are selected in such a way as to effect a substantial diffusion of the fixation liquid (L) through the said deformed portion of biological tissue.

Claim 7

A process according to Claim 1 for the manufacture of valve flaps for cardiac prostheses (1) which comprise a frame (3-8) capable of being traversed by a flow of blood and a sleeve (9) of biological tissue, with a plurality of valve flaps (10) anchored to the frame (3-8) along respective crescent shaped edges (10a) and provided with free edges (10b) projecting inwardly of the frame (3-8) and able to be separated by blood flowing through the prosthesis (1) in one direction and to prevent the flow of blood in the opposite direction by moving to closely matching positions under the pressure exerted by the blood itself, characterised by the fact that it further comprised the operations of: -providing a substantially tubular forming element (29), the wall (30) of which has angularly adjacent apertures (34) corresponding in number to the number of valve flaps (10) of the sleeve (9) and separated from one another by wall elements (35) extending in an axial direction with respect to the tubular forming element (29); the said apertures (34) having respective crescent-shaped edges (34a) to effect forming of the said crescent shaped edges (10a) of the valve flaps (10), -forming said sheet of incompletely fixed biological tissue into a tubular sheath (90), -sealingly fitting said sheath (90) over the said forming element (29), -generating said fluid pressure difference between the interior and the exterior of the said tubular forming element (29) so that the portions of the sheath (90) of biological tissue facing the said apertures (34) of the tubular forming element (29) are pressed inwardly of the said apertures (34) in an arrangement in which the portions of the sheath (90) deformed by the effect of such pressure difference converge radially into the tubular forming element (29) and each has at least one crescent shaped edge (10a), -separating the finally fixed biological tissue of the sheath (90) along a line (91) joining the ends of the crescent shaped edges (10a) of the said portions of the stably deformed sheath (90) to create, in each of such portions, a free edge defining the free edge (10b) of one of the valve flaps (10) of the sleeve (9).

Claim 8

A process according to Claim 6, characterised by the fact that the said tubular sheath (90) is obtained starting from a sheet of biological tissue wound into a tube by bringing two opposite edges of such sheet together and connecting them by stitching the said edges.

Claim 9

A process according to Claim 6 or Claim 7, characterised by the fact that the-said tubular sheath (90) is fixed to the forming element (29) by means of resilient sealing rings (37) fitted over the forming element (29) on opposite sides of the said apertures (34).

Claim 10

Apparatus for carrying out the process of Claim 6 characterised by the fact that it comprises: -a reservoir (21) which can be filled with a fluid (L) for the fixation of the biological tissue, -at least one said tubular forming element (29), projecting into the said reservoir (21) in a position immersed in the said fixation liquid (L), and -means (26, 27; 129) for generating said fluid pressure difference between the fixation fluid (L) within the reservoir (21) and the interior cavity of the said tubular forming element (29).

Claim 11

Apparatus according to Claim 9, characterised by the fact that said wall elements (35) of said tubular forming element (29) are of generally flattened form, orientated in a radial direction with respect to the forming element (29) and are delimited, on the radially outer side, by a surface (35d) which is substantially free of discontinuities.

Claim 12

Apparatus according to Claim 9, characterised by the fact that the said forming element (29) has, at least in the region in which the said apertures (34) are provided a frusto-conical shape.

Claim 13

Apparatus according to Claim 9, characterised by the fact that the reservoir (21) can receive a partial filling of fixation liquid (L) and by the fact that the reservoir (21) has associated therewith a source (26, 27) of gas under pressure selectively adjustable to introduce gas under controlled pressure into the interior (25) of the reservoir (21) situated above the free surface of the fixation liquid (L).

Claim 14

Apparatus according to Claim 9, characterised by the fact that it includes a vacuum generator (129) which can be connected to the interior cavity of each said tubular forming element (29).

Claim 15

Apparatus according to Claim 9, characterised by the fact that the said reservoir (21) includes a cover (21b) having holes (28) each of which forms a mounting seat for an associated tubular forming element (29), each of said holes (28) being associated with a fluid-tight closure member (32) which is transparent and allows observation of the interior cavity of the said associated tubular forming element (29).

Claim 16

Apparatus according to Claim 13 and Claim 14, characterised by the fact that the said cover (21b) is provided with ducts (28a) opening into the said holes (28) and which can put the said vacuum generator (129) into communication with the interior cavity of each said tubular forming element (29).