Methods of Crimping Expandable Medical Devices

• US 20080021543A1
• Filed: 07/20/2007
• Published: 01/24/2008
• Est. Priority Date: 07/20/2006
• Status: Active Grant

• Current Assignee: Abbott Cardiovascular Systems Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Abbott Cardiovascular Systems Incorporated (Abbott Laboratories Incorporated)
• Inventors: Shrivastava, Sanjay
• Granted Patent: US 7,828,916 B2
• Time in Patent Office: Days
• US Class Current: 623/1.31
• CPC Class Codes: A61F 2/9522 Means for mounting a stent or stent-graft onto or into a placement instrument
• CPC Class Codes: A61F 2/958 Inflatable balloons for placing stents or stent-grafts

Abstract

Disclosed are methods for crimping a medical device, such as a stent, wherein the medical device is formed of a superelastic alloy. A method for crimping a medical device includes cooling the stent until the alloy becomes martensitic, allowing the stent to warm after cooling, crimping the stent with a crimping apparatus.

Claims

1. A method of crimping a medical device, comprising:

selecting a medical device fabricated at least partially from an alloy having shape memory properties, wherein the medical device has an expanded diameter;

cooling the device to a temperature below an Ms temperature of the alloy to form thermally induced martensite;

heating the device to a temperature between an Mf temperature and an As temperature of the alloy;

disposing the device within an aperture of a crimping apparatus; and

activating the crimping apparatus such that the device, while disposed within the aperture, is reduced from the expanded diameter to a crimped diameter, the crimped diameter less than the expanded diameter;

wherein the temperature of the device is maintained between the Mf and the As temperatures during crimping such that the thermally induced martensite is maintained in the alloy.

2. The method according to claim 1, further including disposing the device into a delivery system after reducing the device from the expanded diameter to the crimped diameter.

3. The method according to claim 2, wherein the delivery system includes a sheath capable of covering the device to retain the device in the crimped diameter.

4. The method according to claim 1, further comprising cooling the device below the temperature such that the alloy is completely martensitic.

5. The method according to claim 1 wherein the alloy comprises nickel and titanium.

6. The method according to claim 1, wherein the device is a stent.

7. A method of crimping an implantable device, the method comprising:

obtaining an implantable device comprising an alloy, the device having a first size when the alloy is austenitic;

allowing the device to cool from a first temperature, at which the alloy is austenitic, to a second temperature such that the alloy becomes martensitic;

allowing the device to warm from the second temperature to a third temperature while the alloy remains martensitic; and

deforming the device while the alloy remains martensitic such that the device has a second size smaller than the first size.

8. The method of claim 7, wherein the second temperature greater than an Mf temperature of the alloy.

9. The method of claim 7, wherein the second temperature is less than or equal to an Mf temperature of the alloy.

10. The method of claim 7, wherein the third temperature is greater than or equal to an Ms temperature of the alloy.

11. The method of claim 7, wherein the third temperature is greater than or equal to an As temperature of the alloy

12. The method of claim 7, wherein the alloy has an Ms temperature and an As temperature greater than an Ms temperature, and the third temperature is within from about the Ms temperature to about the As temperature.

13. The method of claim 7 wherein the device is a stent comprising a tubular member, and the first size and second size correspond to a diameter of the tubular member.

14. A method of crimping a medical device, the method comprising:

obtaining a device comprising an alloy, the device having a first size when the alloy is mostly or entirely austenite;

causing thermally induced martensite to form in the alloy;

allowing the stent with thermally induced martensite formed in the alloy to warm to a selected temperature above an Ms temperature of the alloy; and

deforming the device at the selected temperature such that the device has a second size less than the first size.

15. The method of claim 14, further comprising causing thermally induced martensite to form entirely throughout the alloy before allowing the stent to warm to the selected temperature.

16. The method of claim 14, further comprising allowing austenite to remain with the thermally induced martensite formed in the alloy immediately before allowing the stent to warm to the selected temperature.

17. The method of claim 14, further comprising preventing austenite from forming in the alloy prior to deforming the device.

18. The method of claim 14, further comprising allowing austenite to form in the alloy when allowing the stent to warm to the selected temperature, the austenite interdispersed with the thermally induced martensite.