Expansible bioprosthetic valve stent

• US 6,458,156 B1
• Filed: 09/08/1999
• Issued: 10/01/2002
• Est. Priority Date: 05/31/1996
• Status: Expired due to Fees

• Current Assignee: University of Western Ontario
• Original Assignee: University of Western Ontario
• Inventors: Boughner, Derek, Duncan, Anthony, Campbell, Gordon, Wan, Wan-Kei
• Primary Examiner(s): McDermott, Corrine
• Assistant Examiner(s): PHAN, HIEU
• Application Number:
  US09/194,634
• Time in Patent Office: 1,119 Days
• Field of Search: 623/2.1, 623/2.11, 623/2.12, 623/2.13, 623/2.14, 623/2.15, 623/2.16, 623/2.17, 623/2.18, 623/2.19, 623/1.49, 623/1.44, 623/1.45, 623/1.46, 623/1.38, 128/898
• US Class Current: 623/2.14
• CPC Class Codes: A61F 2/2412 with soft flexible valve members, e.g. tissue valves shaped like natural valves check valves with flexible valve members in general F16K15/14
• CPC Class Codes: A61F 2/2415 Manufacturing methods
• CPC Class Codes: A61F 2/2418 Scaffolds therefor, e.g. support stents
• CPC Class Codes: A61L 27/52 Hydrogels or hydrocolloids
• CPC Class Codes: A61L 31/145 Hydrogels or hydrocolloids

Abstract

A bioprosthetic valve stent is fabricated from a hydrogel, and a bioprosthetic heart valve comprises such a stent. A method for fabricating a hydrogel bioprosthetic valve stent comprises filling a mold cavity with a solution of a hydrogel, allowing the hydrogel to solidity, removing the solidified hydrogel from the mold cavity and hydrating the hydrogel.

Claims

1. A bioprosthetic valve stent fabricated from a hydrogel, wherein the hydrogel, when hydrated, has

(a) a strain value at ultimate tensile stress (UTS) greater than the maximum strain occurring in a human aortic root under physiological conditions;

(b) an elastic modulus similar to that of the aortic root; and

(c) a relaxation rate similar to that of the aortic root.

2. The valve stent of claim 1 wherein the hydrogel has

(a) a strain at UTS of at least 20%;

(b) an elastic modulus in the range of about 0.01 to about 10 Mpa; and

(c) a relaxation rate in the range of about 3 to about 9 kPa/sec.

3. The stent of claim 2 wherein the hydrogel is a polyvinyl alcohol hydrogel.

5. The stent of claim 1 wherein the hydrogel is selected from the group consisting of poly(vinyl alcohol), polyacrylamide, poly(N-vinylpyrolidone), poly(hydroxyethyl methacrylate), poly(ethylene oxide), poly(ethylene glycol), poly(ethylene glycol) monomethyl ether, cellulose, poly(acrylate), polymethacrylate, poly(methylacrylate), poly(methyl methacrylate) and poly(lactic acid).

6. A bioprosthetic heart valve comprising

a) a stent in accordance with claim 1,

(b) leaflet valve means having three generally triangular leaflets defining respective cusps which are adapted to open and close during heart systole and diastole respectively;

and

(c) means for attaching the leaflet valve means to the stent.

7. The valve of claim 6 wherein the leaflet valve means is selected from the group consisting of glutaraldehyde-pretreated bovine pericardial tissue or glutaraldehyde-pretreated porcine aortic valve cusps.

4. The stent of claim 4 wherein the stent is an aortic valve stent.

8. A method of fabricating a bioprosthetic valve stent comprising the steps of:

(a) preparing a mold cavity corresponding in shape to the stent to be fabricated;

(b) filling said mold cavity with a solution of a selected hydrogel;

(c) allowing the hydrogel to solidify; and

(d) directly after step (c) removing the solidified hydrogel from the mold cavity and hydrating the solidified hydrogel for a suitable period of time.

9. The method of claim 8 wherein the selected hydrogel is PVA and wherein step (c) comprises subjecting the filled mold cavity to at least one freeze-thaw temperature cycle and wherein the method further comprises step (e) subjecting the hydrated hydrogel to at least three freeze-thaw temperature cycles.

10. The method of claim 9 wherein each freeze-thaw temperature cycle employs a freezing temperature in the range of about −

70°

C. to −

30°

C. and a thaw temperature in the range of about 15°

C. to 30°

C.

11. An aortic valve stent fabricated from a hydrogel by a process in accordance with claim 9.

12. The method of claim 8 wherein the selected hydrogel is PVA and wherein step (c) comprises subjecting the filled mold cavity to at least four freeze-thaw temperature cycles.

13. The method of claim 12 wherein each freeze-thaw temperature cycle employs a freezing temperature in the range of about −

70°

C. to −

30°

C. and a thaw temperature in the range of about 15°

C. to 30°

C.

14. An aortic valve stent fabricated from a hydrogel by a process in accordance with claim 12.

15. A bioprosthetic valve stent fabricated from a hydrogel by a process in accordance with claim 8.