WO2013037005A4

WO2013037005A4 - Prosthetic valve

Info

Publication number: WO2013037005A4
Application number: PCT/AU2012/001104
Authority: WO
Inventors: Robert Walter Vowles
Original assignee: Prosthexis Pty Ltd
Current assignee: Prosthexis Pty Ltd
Priority date: 2011-09-16
Filing date: 2012-09-14
Publication date: 2013-06-06
Anticipated expiration: 2014-03-16
Also published as: WO2013037005A1

Abstract

A prosthesis to replace a venous or cardiac valve comprising a valving element in the form of a plurality of spirally-arranged, partially overlapping and facially abutting layers, said valving element being made in a single piece from a thin, elastic material, the end of its outer turn being fixed to an annular supporting ring and the end of its final turn terminating in a capping piece which acts as a central closure of said layers; in their collapsed, abutting state, said partially overlapping layers acting to provide a complete obstruction to flow in one direction but, when pressure is applied to them from the counter direction, lifting and elastically separating in a mode similar to that of the coils of a very light spring; opening of said valve involving only a small torsional distortion distributed more or less equally throughout the whole length of said valving element.

Claims

AMENDED CLAIMS received by the International Bureau on 12 January 2013 (12.01.13)CLAIMS

1. A prosthetic valve to replace a cardiac valve comprising a valving element in the form of a plurality of spirally-arranged, partially overlapping and facially abutting turns, an annular supporting ring to which the end of its initial (outer) turn of said valving element is fixed and a capping piece formed at the end of its final turn, said capping piece acting as a central closure of said valving element; said valving element being made in a single piece from one or more thin, elastic materials; in their collapsed and abutting state, said partially overlapping valving element turns acting to provide a complete obstruction to flow in one direction but, when pressure is applied to them from the counter direction, lifting and elastically separating in a mode similar to that of the coils of a very light spring; said prosthetic valve being specifically characterised by the arrangement of the turns of said valving element in the form of a shallow cone or dome, by the deflection and shaping of the leading (upstream) and trailing (downstream) edges of said valving element, by the elongation and shaping of said capping piece, and by the making of said annular supporting ring with a spirally-tapered step; said deflection and shaping of said valving element and elongation and shaping of said capping piece being such as to maintain a streamlined flow through said prosthetic valve, and said spirally-tapered step of said annular supporting ring ensuring that superincumbent turns of said valving element sit sealingly upon it and, successively, upon themselves when said turns of said valving element are in their said collapsed state.

2. The prosthetic valve of Claim 1 in which the turns of said valving element overlap by between 20 per cent and 80 per cent of their width.

3. The prosthetic valve of Claim 1 in which said valving element leading edges are deflected into alignment with the localised flow and are rounded or tapered to a knife-edge and said valving element trailing edges are deflected into alignment with the desired localised flow and are tapered to a knife-edge.

4. Deleted.

5. Deleted.

6. The prosthetic valve of Claim 1 in which said annular supporting ring is fixed to and supported in a tubular stent.

7. Deleted.

8. Deleted.

9. The prosthetic valve of Claim 1 in which said valving element is made from any suitable metal, metal alloy, metalloid, organic material or inorganic material.

10. The prosthetic valve of Claim 1 in which said valving element is made solid and 5 homogenous, solid and laminated in a single or two or more different materials, hollow, or solid with a tough, hard or elastic outer material encapsulating a softer, lighter or more flexible inner material.

11. The prosthetic valve of Claim 1 in which said valving element is reinforced internally with wires, strips of metal or other elastic material or fabric of various

10 kinds, said reinforcements being elastic or non-elastic.

12. The prosthetic valve of Claim 1 in which all surface parts of said valving element, said supporting ring and said stent are suitably treated to minimise thrombogenic tendencies.

13. The prosthetic valve of Claim 1 in which said annular supporting ring is made from 15 a soft, rubbery polymer material.

14. The prosthetic valve of Claim 1 in which said annular supporting ring is reinforced internally with wire.

15. The prosthetic valve of Claim 1 in which said annular supporting ring is made from a suitable rigid material coated with a suitable polymer material.

^•20 16. The prosthetic valve of Claim 1 in which said valving element is made in a range of transverse cross-sectional shapes in its collapsed form, said shapes ranging from more or less flat to domed; said doming being a symmetrically curved displacement in the direction of blood flow and provided to render said valve better able to accommodate pressures applied to it.

25 17. The prosthetic valve of Claim 16 in which said doming of said valving element ranges from approximately hemispherical to a height to width ratio of 1 : 12.

18. Deleted.

19. The prosthetic valve of Claim 1 in which the outer surface of said circumferential supporting ring is treated to encourage cell attachment to the wall of the vessel in

30 which it is implanted.

20. The prosthetic valve of Claim 1 in which said annular supporting ring is made with its lower surfaces streamlined to prevent the pooling of blood below said ring.

21. The prosthetic valve of Claim 1 in which said annular supporting ring is made with a streamlined fillet at its upper surface to prevent the pooling of blood above said ring.

22. Deleted.

23. Deleted.

24. The prosthetic valve of Claim 1 in which said valving element is made thicker from a softly elastic, rubbery polymer material and reinforced internally with a thin, stiffly elastic reinforcement material.

25. The prosthetic valve of Claim 24 in which said polymer material is a segmented polyurethane elastomer or segmented polyurethane elastomer coated with a grafted polydimethylsiloxane film.

26. The prosthetic valve of Claim 24 in which said polymer material is any of those well known in the art for the making of biomedical devices.

27. The prosthetic valve of Claim 24 in which said internal reinforcement takes the form of sheet, wires or the like of a carbon fibre composite, polymer or metal, such as Nitinol, copper-beryllium alloy, chrome-silicon spring steel, spring-tempered stainless steel, beta C titanium, Elgiloy, MP35N, Hastelloy or the like.

28. The prosthetic valve of Claim 1 in which said capping piece is shaped to maintain a streamlined flow around it and is optionally made solid, in hollow shell form or in shell form filled with foam or other less dense material.

29. The prosthetic valve of Claim 1 in which said annular supporting ring is deleted and the end of the lower turn of said valving element is fixed to a fixation band or sewing ring of the type incorporated into prosthetic heart valves of conventional arrangement.

30. The prosthetic valve of Claim 1 in which said valving element is made in a domed form created by making the transverse cross-sectional shape of said overlapping turns in the form of upwardly angled steps, the upper and lower surfaces of said turns being more or less fully overlapping.

31. The prosthetic valve of Claim 1 in which said valving element is made in an inverted, domed form created by making the transverse cross-sectional shape of said overlapping turns in the form of downwardly angled steps, the upper and lower surfaces of said turns being more or less fully overlapping.

32. The prosthetic valve of Claim 1 in which said valving element is made in a flat or slightly domed form created by making the transverse cross-sectional shape of said turns flat and partially overlapping; two or more wires fixed to said annular supporting ring projecting inwardly and angled upwardly, by abutting the inner edges of said turns of said valving element in their collapsed state, said wires serve to accurately locate said turns.

33. The prosthetic valve of Claim 1 in which said valving element is made in a shallow, cylindrical form created by making the transverse cross-sectional shape of said turns flat and fully overlapping, the first turn of said valving element having a cranked cross-sectional shape to maintain said valving element turns clear of said stent, two or more downwardly projecting guide wires fixed to the underside of said capping piece, by abutting the inner edges of said turns of said valving element in their collapsed state, said wires serve to accurately locate said turns.

34. The prosthetic valve of Claim 1 in which said valving element is made in a slightly inverted, domed form created by making the transverse cross-sectional shape of said turns slightly downwardly curving, the surfaces of said turns partially overlapping.

35. Deleted.

36. The prosthetic valve of Claim 1 in which said valving element is supported from an annular supporting ring supplanting the aortic valve at the base of the ascending aorta, said supporting ring being provided at its upper, outer circumference with an upwardly and outwardly curving fillet which acts to maintain streamlined flow and prevent the pooling of blood in that zone; said supporting ring having formed on its lower edge a downward and outwardly curving collar which passes beneath and effectively encloses the aortic annulus, said collar acting to maintain a streamlined flow and prevent the pooling of blood in that zone; radially arranged sutures being inserted through said supporting ring to secure it permanently in place, suitably positioned pairs of apertures being provided in said supporting ring to accommodate said sutures, said pairs of apertures being joined at their inner ends by narrow, shallow channels which accommodate suture loops passing between said pairs of apertures and maintain said loops flush with the inner surface of said supporting ring.

37. The prosthetic valve of Claim 36 in which, in order to provide a more streamlined flow of blood through said valve, said edges of said valving element are deflected towards the axis of the aorta and said deflected edges are locally modified to generate a three-dimensional, helical blood flow pattern within said ascending aorta similar in character to that of the natural flow pattern.

38. The prosthetic valve of Claim 36 in which, in order to better encourage a streamlined flow around said capping piece, said downstream edges of said valving element closest to said capping piece are more acutely deflected.

39. The prosthetic valve of Claim 36 in which, in order to better sustain forces applied by transvalvular pressure, the degree of overlap of said turns of said valving element is adjusted to make the lines or zones of contact of said turns conform more or less to the shape of a conical or part-spherical body.

40. The prosthetic valve of Claim 36 which is installed in the supra-annular position using a sewing ring of more or less conventional arrangement incorporated into said annular supporting ring.

41. The prosthetic valve of Claim 36 which is installed in the ascending aorta.

42. The prosthetic valve of Claim 1 which is implanted in a vessel via a longitudinal incision, said valve and its said annular supporting ring being inserted through said incision, positioned and secured by a plurality of circumferentially arranged sutures; said sutures being passed through pairs of suitable, radially arranged apertures and tied against an external restraining band of suitable, non-elastic material, shallow channels being provided in the inner surface of said supporting ring joining each said pair of apertures, said channels accommodating said sutures and maintaining them more or less flush with the internal surface of said supporting ring.

43. The prosthetic valve of Claim 42 in which said restraining band is made from a suitable biocompatible material, such as woven or braided Nitinol wire, or woven, knitted or braided polymer filament or textile material such as Dacron or expanded PTFE.

44. The prosthetic valve of Claim 42 in which said restraining band takes the form of a proprietary product of the type normally employed to prevent dilatation of a vessel in the zone adjacent a valve.

45. The prosthetic valve of Claim 1 in which said valving element is made by moulding a preform in a suitable polymer material in the form of a stepped spiral comprising spirally arranged levels, an attachment peg being provided to fix said valving element to said supporting ring; said valving element being created by using a sharp knife, saw or blade heated above the fusion temperature of the material to spirally separate each said level from the one above.

46. The prosthetic valve of Claim 45 in which, where said valving element is internally reinforced by means of wire or metal strip of a suitable elastic material, before moulding of said preform, said internal reinforcement is kinked or otherwise provided with projections which act to locate said reinforcement in a mould, said mould being filled with a suitable thermoplastic or thermosetting material to create said preform; said preform, in turn, being made with projections which locate it within a second larger mould, said second mould then being filled with the same or another material to create a final form or, if appropriate, a second preform, which is completed in a similar manner in a third mould in a third phase of said moulding process.

47. The prosthetic valve of Claim 45 in which said valving element is made from a suitable metal or metal alloy material and said levels are separated by means of chemical milling using a suitable wire as the cutting tool.

48. The prosthetic valve of Claim 1 in which said valving element is fabricated by microwelding from separate pieces of a thin, suitable metal or metal alloy material joined to create said partially overlapping spiral form, said components of said valving element being positionally supported during said fabrication process by rniniature robotic positioning means.

49. The prosthetic valve of Claim 48 in which, following its assembly by microwelding, said valving element is trimmed as required by laser or electrochemical means and electrochemically smoothed or electropolished before passivation, coating, or other treatment, as required.

50. The prosthetic valve of Claim 48 in which said component pieces of said valving element are given three-dimensional shaping individually prior to said fabrication process or as a complete assembly upon completion of said fabrication process.

51. The prosthetic valve of Claim 1 in which said valving element is formed by plasma spraying of material into a suitable mould, a parting agent being progressively applied over each surface as forming proceeds.

52. The prosthetic valve of Claim 51 in which, following completion of its formation, said valving element is trimmed as required by laser or electrochemical means and electrochemically smoothed or electropolished before passivation, coating, or other treatment, as required.

53. The prosthetic valve of Claim 51 in which said valving element is given three- dimensional shaping upon completion of said forming process.

54. The prosthetic valve of Claim 1 in which said valving element is formed by electroless or electrodeposition of material onto a suitable mould, an electrically conductive parting agent being progressively applied over each surface as fonning proceeds, said mould being made to steadily rotate in relation to the anode.

55. The prosthetic valve of Claim 54 in which, following completion of its formation, said valving element is trimmed as required by laser or electrochemical means and electrochemically smoothed or electropolished before passivation, coating, or other treatment, as required.

56. The prosthetic valve of Claim 54 in which said valving element is given three- dimensional shaping upon completion of said forming process.

57. The prosthetic valve of Claim 1 in which said valving element is formed by inkjet printing and sintering, a suitable heat-tolerant parting medium being deposited between each layer as it is deposited onto a steadily rotating mould; pressureless sintering in a controlled atmosphere furnace being employed with temperatures and sintering times being adjusted to provide the desired degree of densification.

58. The prosthetic valve of Claim 57 in which materials employed to form said valving element include glasses, metals, metal alloys, other non-metals and polymers, said parting media including graphite, alumina, zirconia and magnesia applied as a coating on a sacrificial film; to provide increased density following the initial sintering process, said valving element being reheated in a controlled atmosphere and then subjected to high pressure in a suitable die.

59. The prosthetic valve of Claim 1 in which said valving element is formed by electron beam melting of metal powder stock, by electron beam free-form fabrication from wire feedstock, by fused deposition modelling from liquid thermoplastic material, or by laser engineered net shaping from metal powder, said forming taking place in a steadily rotating die and a suitable, heat-tolerant parting medium being deposited between each layer; to provide increased density following the initial sintering process, said valving element is reheated in a controlled atmosphere and then subjected to high pressure in a suitable die.

60. The prosthetic valve of Claim 59 in which, where said metal material is Nitinol created by the sintering of Ni and Ti powders and subsequently hot compressed in a suitable die in controlled atmosphere and at a suitable temperature, the characteristic shape-memory and superelasticity effects of Nitinol are achieved.

61. The prosthetic valve of Claim 1 in which said valving element is formed by extrusion of a continuous thin strip of a suitable polymer material from a shaped die onto a steadily rotating mould, a suitable parting medium being applied to each layer.

62. The prosthetic valve of Claim 1 in which said valving element is formed by a pultrusion process using a suitable filamentary reinforcement material in a suitable thermosetting or thermoplastic polymer, said material being extruded from a shaped die onto a steadily rotating mould, a suitable parting medium being applied to each layer.

63. The prosthetic valve of Claim 1 in which said valving element is formed in layers by spray coating or plasma polymerization, PTFE being spray coated and cured at temperatures above 300 degrees C, PTFE, polyurethane, parylene or the like being deposited by plasma polymerization onto a steadily rotating mould, a suitable parting medium being applied to each layer.

64. The prosthetic valve of Claim 1 in which said valving element is formed in layers by plasma spraying, physical vapour deposition, ion plating, plasma-based plating or sputter deposition from suitable materials, said materials being deposited onto a steadily rotating mould, a suitable parting medium being applied to each layer.

65. The prosthetic valve of Claim 1 in which said valving element is formed by laser heating of a progressively advancing stretching zone of a thin, continuous strip of glass or polymer material, said heating being above the glass transition temperature of the material to permit said strip to be locally stretched as said stretching zone passes along it and be spirally wound over a continuously rotating suitable mould or former; said strip optionally being made with a tapering cross-sectional form such that, when said strip is stretched into said spiral arrangement, it assumes a parallel or other cross-sectional form; a suitable parting medium being continuously applied to the formed strip to prevent adhesion of a superincumbent layer.

66. The prosthetic valve of Claim 1 in which said valving element is formed by laser heating of a progressively advancing zone of an array of glass or polymer filaments above the glass transition temperature of the material, said array first being deformed and spirally wound over a continuously rotating suitable mould or former before being fused together to form a strip; if necessary, a suitable parting medium being continuously applied to the formed strip to prevent adhesion of a superincumbent layer.

67. The prosthetic valve of Claim 1 in which said valving element is formed by laser heating of a progressively advancing zone of an array of abutting, parallel glass or metal filaments coated with a thermoplastic or thermosetting polymer, said array first being deformed and spirally wound over a continuously rotating suitable mould or former before said polymer is heated above its glass transition temperature, thereby fusing said coated filaments together to form a strip; if necessary, a suitable parting medium being continuously applied to the formed strip to prevent adhesion of a superincumbent layer.

68. The prosthetic valve of Claim 1 in which said valving element is formed by UV or other irradiation of a progressively advancing zone of an array of abutting, parallel glass or metal filaments coated with a radiation-curing polymer, said array first being deformed and spirally wound over a continuously rotating suitable mould or former before said polymer is irradiated to set said polymer and fuse said coated filaments together to form a strip; if necessary, a suitable parting medium being continuously applied to the formed strip to prevent adhesion of a superincumbent layer.

69. The prosthetic valve of Claim 1 in which, to encourage endothelialisation or to minimise thromogenetic effects, said valving element is coated with any of or any combination of polytetrafluoroethylene; polyurethane (PU); segmented polyurethane; polymethylsiloxane; non-porous silicone polymer coating on PTFE; self-assembling silane monolayer; silyl-heparin coating using PEG as a cross-linking agent; pyrolytic carbon; amorphous diamond-like carbon (DLC); turbostratic carbon; silicon; silicon dioxide; silicon nitride; silicon carbide; synthesised mussel adhesive polypeptide; heparin attached via amine functional groups; gelatin-glutaraldehyde cross-linked on silicone rubber; type 1 collagen attached via ion beam surface modification; polypeptide multilayer or polymer, enzyme or nanoparticle film generated electrostatically layer-by-layer; adhesive polypeptide and anti-CD34 antibody; heparin-collagen multilayer with anti-CD34 antibody; glycosaminglycans and antithrombin ΠΙ; monomeric conjugate containing benzamidine modified with PEG spacer; photocured gelatin or microporous thin segmented polyurethane seeded with endothelial progenitor cells; plasma polymerized n-butyl methacrylate; dextran-40 in photocured gelatin or gelatin/alginate hydrogel; forskolin or forskolin agarose; heparin stabilized ionically bonded to polyurethane or covalently bonded to PTFE; Rapamycin-coated PTFE; heparin/collagen multilayer; heparin covalently bonded by end-point attachment to polyethylene; waxes, including candelilla, spermaceti, bees, carnauba, carbowax and paraffin; bacterial cellulose in hydroxyethylcellulose or other matrix; alkanethiol self-assembling monolayer with -OH OR -COOH surface groups optionally with plasma albumen absorbed onto the surface; self-assembling monolayers of bromoethylphosphorate-, phosphorylcholine-, phosphorylethanol- amine-, hydroxyl-terminated polymers or self-assembling monolayers, poly(carboxybetaine methacrylate) polymer, or polystyrene coated with a copolymer of L-histidine, a zwitterion, w-butyl methacrylate and hydrophobic moiety; polymer brushes containing sulfated carbohydrate repeat units resembling surface-tethered heparin; polysaccharide-based glycocalyx-mimicking polymer coating; free ε-amino surface groups incorporated using PEG-lysine conjugates; polyurethane coated with a lysine-derivatized acrylamide polymer; nanocomposite fibrinolytic coatings comprising proteolytic enzymes tethered to the surfaces of carbon nanotubes and dispersed in poly (methyl methacrylate), enzymes such as serine protease, subtilisin Carlsberg and trypsin, the enzymes being loaded onto the carbon nanotubes by physisorption and a fibrinolytic enzyme being optionally incorporated into the coatings; a low-leaching, NO-generating polyelectrolyte multilayer thin film comprising sodium alginate and organoselemum-modified rwlyemyleneimine prepared by layer-by-layer assembly on a silicone rubber or polyurethane substrate; polyelectrolyte multilayer coatings of chitosan and dextran sulfate on poly (tetramethylene adipate-co-terephthalate, L-arginine being optionally incorporated; polyurethane coatings incorporating hyaluronic acid as a chain extender during polyurethane synthesis; poly (ester urethane) dip-coated with an amphiphilic conjugate of stearyl poly (ethylene oxide) with 4,4'-methylene diphenyl diisocynate, a film-building additive in the form of a polytetramethylene glycol-based polyurethane elastomer being incorporated; polymer coatings of paracyclophane derivatives co-deposited in controlled ratios by chemical vapour deposition as functionalized coatings polymerized into poly (p-xylenes) during the deposition process; heparin immobilized on silicone via a heterobifunctional PEG spacer; treatments of said valving element including doping (fluorine doped DLC) or the provision of functionalized endgroups (PU) for attachment of a variety of compounds; said coatings and said treatments or any combination of them also being applied as required to said supporting ring and to said stent.

70. The prosthetic valve of Claim 1 in which said valving element is collapsed into compact form for endovascular implantation by restraining said annular supporting ring while rotational tension is applied to said valving element via said capping piece such that the coils of said valving element assume a compact, tightly-nested, conical form; a force then being applied to said annular supporting ring at a point diametrically opposed to the point of attachment of said valving element such that said supporting ring is completely collapsed inwardly against the opposing side allowing the ends of the collapsed form to be overlapped, said collapsed form of said valve being less than half its normal diameter; said collapsed valve then being fixed in correct directional orientation within the distal end of a suitable expandable stent which is, itself, collapsed into compact form; said stent and said valve then being drawn into a thin metal sleeve supported on the distal end of a catheter with a deflated balloon within said stent.

71. The prosthetic valve of Claim 1 in which said valving element is fixed to said annular supporting ring by means of a peg formed on the end of said valving element, said peg being permanently accommodated within a complementary bore in a boss formed on said annular supporting ring.

72. The prosthetic valve of Claim 1 which is elasticaliy compliant, radial pressure applied to the closed said valving element being accommodated by sliding displacement of its said turns one to another without their being unseated.

73. The prosthetic valve of Claim 1 in which, depending upon the elastic characteristics of the particular material from which said valving element is made, said turns of said valving element are made with a thickness in the range 0.01 millimetre to 4.0 millimetres.

74. The prosthetic valve of Claim 1 in which said valving element is made in composite or laminated form with one or more layers of a soft flexible material laminated with one or more layers of a stiffly flexible material, the thickness and width of said layers being varied to provide desired physical characteristics.

75. The prosthetic valve of Claim 1 in which said valving element is made from a thin, superelastic metal, such as nitinol, the superelastic characteristics of said material being exploited to permit said valve to be collapsed into compact form to facilitate implantation.

76. The prosthetic valve of Claim 1 in which the local width and thickness of said turns of said valving element are adjusted to ensure a consistent elastic response to pressure-generated forces throughout all parts of said valving element.

77. The prosthetic valve of Claim 1 in which said valving element is made with a greater or lesser number of turns to suit the needs of a particular application, the number of turns varying between 1 and 10.

78. Deleted.

79. The prosthetic valve of Claim 1 in which, in order to manipulate flow characteristics through a said valve and in zones adjacent it, the cross-sectional shaping of said valving element is locally varied.

80. The prosthetic valve of Claim 1 in which the first turn of said valving element and said annular supporting ring to which it is attached are made thicker and narrower than other turns of said valving element and shaped to facilitate flow past them.

81. The prosthetic valve of Claim 1 in which the degree of overlap of said turns of said valving element is varied at different parts of said valving element, a consistent seating force being achieved throughout said valving element by increasing overlap in turns of larger diameter and decreasing overlap in turns of smaller diameter, reduced overlap being acceptable in turns of smaller diameter owing to their greater positional stability.

82. The prosthetic valve of Claim 1 in which deflected leading and trailing edges of successive said turns of said valving element are made to nest closely.

83. The prosthetic valve of Claim 1 in which the end of the first turn of said valving element is supported from said annular supporting ring by one or more thin, narrow elastic elements, the ends of which are embedded securely in said valving element and in said annular supporting ring, said elastic elements being accommodated in complementary channels formed in the upper surface of said supporting ring; said elastic elements being free to rise upwardly from said channels and their free length being such as to permit the fixed end of said valving ring to rise clear of said annular supporting ring, thereby ensuring that the attachment zone of said valving element and said supporting ring is continuously swept by blood and that stagnation does not occur; in the closed position of said valve, the end of said valving element just contacting the slightly angled end surface of a rebate provided in said annular supporting ring.

84. The prosthetic valve of Claim 83 in which said elastic elements take the form of highly polished, elastic, round metal wire.

85. The prosthetic valve of Claim 1 in which, to minimise thrombogenetic effects, said valving element is made with its surfaces covered in a biological material, such as fibrous pericardium.

86. The prosthetic valve of Claim 1 in which said capping piece is made hollow from a suitable softly flexible material and is able to be collapsed for endovascular implantation, said capping piece being inflated after implantation by a slow chemical reaction generating a settable polymer foam.

87. The prosthetic valve of Claim 1 in which a narrow, slightly raised, annular sealing surface is provided along the surfaces of said valving element, said raised sealing surface being situated medially on both surfaces of said turns or at the outer edge of the lower surfaces of said turns or the inner edge of the upper surfaces of said turns.

88. The prosthetic valve of Claim 1 in which said valving element and said annular supporting ring are formed in a single piece, said combined components being formed using a suitable 3D forming process and subsequently heated or subjected to another densification process.

89. A method of replacing a venous or cardiac valve by implantation of a prosthetic valve, said prosthetic valve comprising a valving element in the form of a plurality of spirally-arranged, partially overlapping and facially abutting turns, an annular supporting ring to which the end of its initial (outer) turn of said valving element is fixed and a capping piece formed at the end of its final turn, said capping piece acting as a central closure of said valving element; said valving element being made in a single piece from one or more thin, elastic materials; in their collapsed and abutting state, said partially overlapping valving element turns acting to provide a complete obstruction to flow in one direction but, when pressure is applied to them from the counter direction, lifting and elastically separating in a mode similar to that of the coils of a very light spring; said prosthetic valve being specifically characterised by the arrangement of the turns of said valving element in the form of a shallow cone or dome, by the deflection -and shaping of the leading (upstream) and trailing (downstream) edges of said valving element, by the elongation and shaping of said capping piece, and by the making of said annular supporting ring with a spirally-tapered step; said deflection and shaping of said valving element and elongation and shaping of said capping piece being such as to maintain a streamlined flow through said prosthetic valve, and said spirally-tapered step of said annular supporting ring ensuring that superincumbent turns of said valving element sit sealingly upon it and, successively, upon themselves when said turns of said valving element are in their said collapsed state.

90. The method of Claim 89 in which said valving element leading edges are deflected into alignment with the localised flow and are rounded or tapered to a knife-edge and said valving element trailing edges are deflected into alignment with the desired localised flow and are tapered to a knife-edge.

91. Deleted.

92. Deleted.

93. The method of Claim 89 in which said annular supporting ring is deleted and the end of the lower turn of said valving element is fixed to a fixation band or sewing ring as incorporated into prosthetic heart valves of conventional arrangement.

94. The method of Claim 89 in which said valving element is supported from an annular supporting ring supplanting the aortic valve at the base of the ascending aorta, said supporting ring being provided at its upper, outer circumference with an upwardly and outwardly curving fillet which acts to maintain streamlined flow and prevent the pooling of blood in that zone; said supporting ring having formed on its lower edge a downward and outwardly curving collar which passes beneath and effectively encloses the aortic annulus, said collar acting to maintain a streamlined flow and prevent the pooling of blood in that zone; radially arranged sutures being inserted through said supporting ring to secure it permanently in place, suitably positioned pairs of apertures being provided in said supporting ring to accommodate said sutures, said pairs of apertures being joined at their inner ends by narrow, shallow channels which accommodate suture loops passing between said pairs of apertures and maintain said loops flush with the inner surface of said supporting ring.

95. The method of Claim 89 in which, in order to provide a more streamlined flow of blood through said valve, said edges of said valving element are deflected towards the axis of the aorta and said deflected edges are locally modified to generate a three- dimensional, helical blood flow pattern within said ascending aorta similar in character to that of the natural flow pattern.

96. The method of Claim 94 in which said prosthetic valve is installed in the supra- annular position using a sewing ring of more or less conventional arrangement incorporated into said annular supporting ring.

97. The method of Claim 94 in which said valve is installed in the ascending aorta.

98. The method of Claim 89 in which said valve is implanted in a vessel via a longitudinal incision, said valve and its said annular supporting ring being inserted through said incision, positioned and secured by a plurality of circumferentially arranged sutures; said sutures being passed through pairs of suitable, radially arranged apertures and tied against an external restraining band of suitable, non- elastic material, shallow channels being provided in the inner surface of said supporting ring joining each said pair of apertures, said channels accommodating said sutures and maintaining them more or less flush with the internal surface of said supporting ring.

99. The method of Claim 89 in which said valving element is collapsed into compact form for endovascular implantation by restraining said annular supporting ring while rotational tension is applied to said valving element via said capping piece such that the coils of said valving element assume a compact, tightly-nested, conical form; a force then being applied to said annular supporting ring at a point diametrically opposed to the point of attachment of said valving element such that said supporting ring is completely collapsed inwardly against the opposing side, allowing the ends of the collapsed form to be overlapped, said collapsed form of said valve being less than half its normal diameter; said collapsed valve then being fixed in correct directional orientation within the distal end of a suitable expandable stent which is, itself, collapsed into compact form; said stent and said valve then being drawn into a thin metal sleeve supported on the distal end of a catheter with a deflated balloon within said stent.

100. The method of Claim 89 in which the end of the first turn of said valving element is supported from said annular supporting ring by one or more thin, narrow elastic elements, the ends of which are embedded securely in said valving element and in said annular supporting ring, said elastic elements being accommodated in complementary channels formed in the upper surface of said supporting ring; said elastic elements being free to rise upwardly from said channels and their free length being such as to permit the fixed end of said valving ring to rise clear of said annular supporting ring, thereby ensuring that the attachment zone of said valving element and said supporting ring is continuously swept by blood and that stagnation does not occur; in the closed position of said valve, the end of said valving element just contacting the slightly angled end surface of a rebate provided in said annular supporting ring.