Enhanced chronic lead removal

• US 20030028224A1
• Filed: 04/19/2002
• Published: 02/06/2003
• Est. Priority Date: 04/20/2001
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Anderson, James M., Ebert, Michael J., McVenes, Rick D., Stokes, Kenneth B.
• Granted Patent: US 6,966,322 B2
• Time in Patent Office: Days
• US Class Current: 607/36
• CPC Class Codes: A61L 2400/18 Modification of implant surfaces in order to improve biocompatibility, cell growth, fixation of biomolecules, e.g. plasma treatment
• CPC Class Codes: A61L 31/10 Macromolecular materials
• CPC Class Codes: A61N 1/056 Transvascular endocardial electrode systems
• CPC Class Codes: A61N 1/37512 Pacemakers
• CPC Class Codes: C08L 33/26 Homopolymers or copolymers of acrylamide or methacrylamide

Abstract

An implantable medical device, perhaps a pacemaker lead, has a medical unit and a casing at least partially enclosing the medical unit. The casing is formed of a base polymer having surface modifying pendant groups formed of an acrylamide polymer or an acrylamide copolymer, perhaps polyisopropyl acrylamide. The base polymer may be a polyurethane, polyimide, fluoropolymer or polyolefin, for example.

Claims

1. An implantable medical device, comprising:

a medical unit; and

a casing at least partially enclosing the medical unit, the casing being formed of a base polymer having surface modifying pendant groups, the surface modifying pendant groups being formed of an acrylamide polymer or an acrylamide copolymer.

2. An implantable medical device according to claim 1, wherein polyisopropyl acrylamide is used for the pendant groups.

3. An implantable medical device according to claim 1, wherein the pendant groups are attached to a back bone of the base polymer.

4. An implantable medical device according to claim 1, wherein the pendant groups are attached to the base polymer as surface modifying end groups.

5. An implantable medical device according to claim 4, further comprising an outer layer formed on the casing and covalently bonded to the surface modifying end group, the outer layer being formed of a polymer different from the base polymer forming the casing.

6. An implantable medical device according to claim 1, wherein the acrylamide polymer or acrylamide copolymer is cross linked.

7. An implantable medical device according to claim 1, wherein the medical unit comprises a pacemaker lead.

8. An implantable medical device according to claim 1, wherein the base polymer is selected from the group consisting of polyurethanes, polyimides, fluoropolymers and polyolefin.

9. An implantable medical device according to claim 4, wherein the base polymer having surface modifying end groups formed of the acrylamide polymer or acrylamide copolymer has a surface tension that differs by at least one dyne/cm from the surface tension of an otherwise identical polymer having diethylamino end groups.

10. An implantable medical device according to claim 4, wherein the surface modifying end groups are covalently bonded to the base polymer.

11. An implantable medical device according to claim 1, further comprising a thermally active device to change the temperature of the casing.

12. An implantable medical device according to claim 1, wherein the thermally active device is an electric heating element provided within the implantable medical device.

13. An implantable medical device according to claim 11, wherein the thermally active device comprises lumens located within the implantable medical device for receiving heated or chilled fluids.

14. An implantable medical device according to claim 1, wherein the medical unit contains a shell having an outer surface, and the casing is formed on the outer surface of the shell.

15. A method of implanting a removeable medical device, comprising:

implanting in a patient a medical unit having a casing formed of a base polymer having surface modifying pendant groups; and

allowing the surface modifying pendant groups to form a hydrogel within the patient.

16. A method according to claim 15, wherein the pendant groups are attached to a back bone of the base polymer.

17. A method according to claim 15, wherein the pendant groups are attached to the base polymer as surface modifying end groups.

18. A method according to claim 15, wherein the hydrogel has a water content of at least 10 weight %.

19. An implantable medical device, comprising:

a medical unit; and

a casing at least partially enclosing the medical unit, the casing being formed of a base polymer having surface modifying end groups, the surface modifying end groups being cross-linked.

20. An implantable medical device according to claim 19, wherein the base polymer is a silicone,

the surface modifying end groups are a silica free silicone, and

the surface modifying end groups contain vinyl functionality to promote cross-linking.

21. A method of forming an implantable medical device, comprising:

forming a medical unit;

forming a casing at least partially enclosing the medical unit, the casing being formed of a base polymer having surface modifying pendant groups; and

after forming the casing, forming a polymeric outer layer on the casing by covalently bonding the polymeric material to the surface modifying pendant groups.

22. A method of forming an implantable medical device according to claim 21, wherein the outer layer is formed of a polymeric material different from the base polymer forming the casing.

23. An implantable medical device, comprising:

a medical unit;

a casing at least partially enclosing the medical unit, the casing being formed of a base polymer having surface modifying pendant groups; and

a thermally active device to change the temperature of the polymer material.

24. A method of extracting a chronically implanted medical device, comprising:

changing the temperature of an implanted medical device having a medical unit and a casing at least partially enclosing the medical unit, the casing being formed of a base polymer having surface modifying pendant groups; and

extracting the implanted medical device.

25. A method according to claim 24, wherein the temperature of the implanted medical device is changed through a thermally active device included in the implanted medical device.

26. A method according to claim 24, wherein changing the temperature of the implanted medical device involves heating the implanted medical device to denature collagen surrounding the implanted medical device.

27. A method according to claim 26, wherein the implanted medical device is heated to a temperature of at least 40°

C.

28. A method according to claim 24, wherein the surface modifying end groups of the casing form a hydrogel within a patient.

29. A method according to claim 28, wherein the surface modifying end groups are formed of an acrylamide polymer or an acrylamide copolymer.

30. A method according to claim 28, wherein changing the temperature of the implanted medical device involves cooling the implanted medical device to change the water content of the hydrogel.

31. A method according to claim 30, wherein the implanted medical device is cooled to a temperature of at least 30°

C.