Multi-stranded heat set annuloplasty rings
An annuloplasty repair segment for heart valve annulus repair. In one embodiment a multi-stranded cable replaces solid core wire for both the tricuspid and mitral valves. Cable allows for greater deployment flexibility for minimally-invasive surgical (MIS) implant, while still maintaining the required strength and similar tensile properties of solid-core wire. Stranded cable provides a MIS annuloplasty ring with sufficient flexibility in the x-y plane to allow a surgeon to squeeze the ring into a small incision, such as being able to pass through an 18 Fr or smaller catheter, while maintaining structural rigidity under forces exerted on the implanted ring by the cardiac cycle. The particular shape of the annuloplasty ring is fixed using a heat setting process.
1. A method for forming an annuloplasty ring, comprising:
providing a flexible core member comprising a braided metal cable made of a metal having an austenite start temperature of at least 500° C.;
providing a holding fixture having a base member and at least one clamping member, wherein the base member and clamping member have complementary channels therein that together provide a three-dimensional mold for the desired peripheral shape of the annuloplasty ring;
holding the core member in a desired peripheral shape of the annuloplasty ring by placing the core member between the base member and the at least one clamping member;
while being held in the desired peripheral shape, heating the core member above its austenitic final temperature and maintaining that temperature for a period of time to cause a crystalline structure alteration from martensitic to austenitic;
cooling the core member with a quench; and
adding a suture-permeable outer covering around the flexible core member.
2. The method of claim 1 , wherein the core member comprises a multi-stranded braided cable formed of multiple wire strands wound into multi-strand braids with the multi-strand braids being braided into the multi-stranded braided cable.
3. The method of claim 2 , wherein the multi-stranded braided cable has at least seven multi-strand braids in cross-section.
4. The method of claim 1 , wherein the braided cable has sufficient flexibility to enable it to be manipulated into an elongated shape to fit within a tubular access device.
5. The method of claim 1 , wherein the peripheral shape is closed.
6. The method of claim 1 , wherein the peripheral shape is open with two free ends.
7. The method of claim 6 , wherein the method includes capping or welding the two free ends to cover individual strand ends.
8. The method of claim 1 , wherein the metal is MP35N LT.
9. The method of claim 1 , wherein the metal is Nitinol.
10. The method of claim 1 , further comprising providing a holding fixture having a base member and at least one clamping member, wherein the base member and clamping member have complementary channels therein that together provide a three-dimensional mold for the desired peripheral shape of the annuloplasty ring, and wherein the step of holding the core member comprises placing the core member between the base member and the at least one clamping member.
11. The method of claim 10 , wherein the desired peripheral shape is open with two free ends, and the holding fixture has three clamping members: a first one for a closed side of the core member and two others for the two free ends, and wherein the method includes placing the clamping members sequentially over the core member with the first clamping member first and the two others second and third.
12. The method of claim 11 , wherein the desired peripheral shape is three-dimensional, and the base member and three clamping members have raised areas such that the channel defines the three-dimensional peripheral shape.
13. The method of claim 11 , wherein clamping members bolt to the base member to hold the core member firmly in the channel.