METHOD OF LOADING A MEDICAL DEVICE INTO A DELIVERY SYSTEM

• US 20110137398A1
• Filed: 04/23/2009
• Published: 06/09/2011
• Est. Priority Date: 04/23/2008
• Status: Active Grant

• Current Assignee: Cook Medical Incorporated (Cook Group Incorporated)
• Original Assignee: Cook Incorporated (Cook Group Incorporated)
• Inventors: Carlson, James M., Magnuson, Mark A.
• Granted Patent: US 8,888,835 B2
• Time in Patent Office: Days
• US Class Current: 623/1.11
• CPC Class Codes: A61F 2/95 Instruments specially adapted for placement or removal of stents or stent-grafts
• CPC Class Codes: A61F 2/9522 Means for mounting a stent or stent-graft onto or into a placement instrument
• CPC Class Codes: A61F 2/9524 Iris-type crimpers
• CPC Class Codes: A61F 2210/0014 using shape memory or superelastic materials, e.g. nitinol
• CPC Class Codes: A61F 2250/0042 differing in shape-memory transition temperatures, e.g. in martensitic transition temperature, in austenitic transition temperature
• CPC Class Codes: C22F 1/00 Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working apparatus for mechanical working of metal B21, B23, B24
• CPC Class Codes: C22F 1/006 Resulting in heat recoverable alloys with a memory effect
• CPC Class Codes: C22F 1/10 of nickel or cobalt or alloys based thereon
• CPC Class Codes: Y10T 29/49826 Assembling or joining

Abstract

A method of loading a medical device into a delivery system includes providing a two-stage shape memory alloy at a temperature at which at least a portion of the alloy includes austenite. A stress which is sufficient to form R-phase from at least a portion of the austenite is applied to the medical device at the temperature. A delivery configuration of the medical device is obtained, and the medical device is loaded into a restraining member. Preferably, the delivery configuration of the medical device includes stress-induced R-phase.

Claims

1. A method of loading a medical device into a delivery system, the method comprising:

providing a medical device comprising a two-stage shape memory alloy at a temperature at which at least a portion of the alloy is austenite;

applying a stress to the medical device at the temperature, the stress being sufficient to form R-phase from at least a portion of the austenite;

obtaining a delivery configuration of the medical device; and

loading the medical device in the delivery configuration into a restraining member, wherein the delivery configuration comprises stress-induced R-phase.

2. The method of claim 1 wherein the stress applied to the medical device is not sufficient to form martensite from the R-phase.

3. The method of claim 2 wherein the delivery configuration does not include stress-induced martensite.

4. The method of claim 1 wherein the stress-induced R-phase is present in the delivery configuration of the medical device in regions of maximum strain.

5. The method of claim 1 wherein the stress applied to the medical device is sufficient to form martensite from at least a portion of the R-phase.

6. The method of claim 5 wherein the delivery configuration of the medical device further comprises stress-induced martensite.

7. The method of claim 1 wherein the stress applied to the medical device does not exceed 200 MPa.

8. The method of claim 1 wherein the temperature is between about A_s and A_s+10°

C. of the shape memory alloy and preferably between about A_s and A_s+6°

C. of the shape memory alloy.

9. The method of claim 1 wherein the temperature is at or above A_f of the shape memory alloy, the alloy being fully austenitic at the temperature.

10. The method of claim 1 further comprising, prior to applying the stress to the medical device, processing the shape memory alloy to maximize a difference between a martensite start temperature and an R-phase start temperature of the alloy.

11. The method of claim 1 wherein applying the stress to the medical device comprises radially compressing the medical device and wherein the medical device is a self-expanding stent.

12. A delivery system for a medical device comprising:

a restraining member; and

a medical device comprising a two-stage shape memory alloy, the medical device being maintained in a delivery configuration by the restraining member, the delivery configuration including stress-induced R-phase.

13. The method of claim 12, wherein the stress-induced R-phase is present in the delivery configuration of the medical device in regions of maximum strain.

14. The delivery system of claim 12, wherein the delivery configuration does not include stress-induced martensite.

15. A medical device which comprises:

(a) a stent for intraluminal placement within a human body so that the stent is substantially at human body temperature, the stent comprising a two-stage shape memory alloy at least a portion of which comprises austenite at body temperature; and

(b) a restraint holding the stent in a deformed configuration at a temperature less than the body temperature of the human for intraluminal placement of the stent within the human body in its deformed configuration, the deformation occurring through the formation of stress-induced R-phase;

wherein the stent is sufficiently deformed that when the stent is at human body temperature, removal of the restraint from the stent, without change in temperature of the device, releases at least a portion of the stent from its deformed configuration.

16. A method of loading a medical device into a delivery system, the method comprising:

providing a medical device comprising a two-stage shape memory alloy, the alloy being at a temperature at which the alloy includes a parent phase, the parent phase not being R-phase;

stress-inducing the R-phase from the parent phase in at least a portion of the alloy at the temperature;

obtaining a delivery configuration of the medical device; and

loading the medical device in the delivery configuration into a restraining member, wherein the delivery configuration comprises stress-induced R-phase.

17. The method of claim 16, wherein the parent phase is austenite.

18. The method of claim 16, wherein the parent phase is martensite.

19. The method of claim 16, further comprising stress-inducing martensite from at least a portion of the stress-induced R-phase.

20. The method of claim 16, wherein the delivery configuration of the medical device further comprises stress-induced martensite.