High impedance active fixation electrode of an electrical medical lead

• US 20060122682A1
• Filed: 12/03/2004
• Published: 06/08/2006
• Est. Priority Date: 12/03/2004
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Sommer, John L., Coles, James A. Jr., Sigg, Daniel C.
• Granted Patent: US 7,720,550 B2
• Time in Patent Office: Days
• US Class Current: 607/127
• CPC Class Codes: A61N 1/0573 chacterised by means penetrating the heart tissue, e.g. helix needle or hook
• CPC Class Codes: A61P 29/00 Non-central analgesic, antipyretic or antiinflammatory agents, e.g. antirheumatic agents; Non-steroidal antiinflammatory drugs [NSAID]
• CPC Class Codes: A61P 9/00 Drugs for disorders of the cardiovascular system

Abstract

Electrical medical leads having active fixation electrodes, particularly helix electrodes intended to be screwed into body tissue, e.g., the heart, are disclosed having selectively applied insulation to optimize exposed electrode surface area and dispose the exposed electrode surface area toward tissue that is less traumatized by injury caused by screwing in the fixation helix. In a preferred fabrication method, an outer helical surface is masked by contact with a masking tube while a dielectric coating is applied to the inner helical surface of the coil turns of the helix, and the masking tube is removed when the dielectric coating has set. In one variation, at least one aperture is formed through the masking tube sidewall exposing an area of the outer helical surface thereby interrupting the uninsulated outer helical electrode.

Claims

1. An electrical medical lead adapted to be implanted within the body at an implantation site to conduct electrical stimulation from an implantable stimulator to the site and to conduct electrical signals of the body from the site to the implantable or external stimulator comprising:

an elongated lead body extending from a lead body proximal end to a lead body distal end;

a lead connector element at the lead body proximal end;

a lead conductor enclosed within the lead body and electrically coupled to the first lead connector element

an active fixation helix attached to the lead body distal end electrically coupled to the lead conductor, the fixation helix comprising at least one coil turn wound about a helix lumen and extending distally from a helix attachment end to a helix tip shaped to penetrate body tissue when the helix is screwed into body tissue to secure fixation to the implantation site; and

a layer of insulation covering at least a portion of an inner helical surface of each coil turn disposed toward the helix lumen,

whereby at least a portion of an outer helical surface of each coil turn is uninsulated, and the uninsulated outer helical surface functions as an outer helical electrode disposed toward body tissue away from the helix lumen.

2. The electrical medical lead of claim 1, wherein the fixation helix comprises a plurality of coil turns wound with a constant pitch and inner and outer diameter from the helix attachment end to the helix tip thereby defining a space between facing surfaces of adjacent coil turns, and the layer of insulation covers at least portions of the facing surfaces.

3. The electrical medical lead of claim 2, wherein the helix is formed of platinum metal or a platinum alloy and the uninsulated helical outer surface is coated with a coating selected from the group consisting of titanium nitride, iridium oxide, platinum black, and carbon nanotubes

4. The electrical medical lead of claim 2, wherein the uninsulated helical outer surface is in a continuous band extending substantially between the point of attachment to the helix tip.

5. The electrical medical lead of claim 4, wherein the uninsulated helical outer surface has a surface area in the range of about 10% to about 50% of the total surface area.

6. The electrical medical lead of claim 2, wherein the uninsulated helical outer surface is interrupted by the insulating layer applied along the helical outer surface between the point of attachment and the helix tip.

7. The electrical medical lead of claim 6, wherein the uninsulated helical outer surface has a surface area in the range of about 10% to about 50% of the total surface area.

8. The electrical medical lead of claim 1, wherein the helix is formed of platinum metal or a platinum alloy and the uninsulated helical outer surface is coated with a coating selected from the group consisting of titanium nitride, iridium oxide, platinum black, and carbon nanotubes

9. The electrical medical lead of claim 1, wherein the uninsulated helical outer surface is in a continuous band extending substantially between the point of attachment to the helix tip.

10. The electrical medical lead of claim 4, wherein the uninsulated helical outer surface has a surface area in the range of about 10% to about 50% of the total surface area.

11. The electrical medical lead of claim 1, wherein the uninsulated helical outer surface is interrupted by the insulating layer applied along the helical outer surface between the point of attachment and the helix tip.

12. The electrical medical lead of claim 11, wherein the uninsulated helical outer surface has a surface area in the range of about 10% to about 50% of the total surface area.

13. The electrical medical lead of claim 1, wherein the uninsulated helical outer surface has a surface area in the range of about 10% to about 50% of the total surface area.

14. The electrical medical lead of claim 13, wherein the helix is formed of platinum metal or a platinum alloy the uninsulated helical outer surface is coated with a coating selected from the group consisting of titanium nitride, iridium oxide, platinum black, and carbon nanotubes.

16. The electrical medical lead of claim 1, wherein the insulating layer is selected from the group consisting of silicone rubber, parylene, polyurethane, polyacrylate, polymethacrylate, polyester, polyamide, polyether, polysiloxane, and polyepoxide.

17. The electrical medical lead of claim 1, wherein a steroid selected from the group consisting of derivatives of dexamethasone, dexamethasone sodium phosphate, beclomethasone diproprionate, and dexamethasone acetate is applied onto or incorporated into at least a portion of the insulating layer.

18. A method of fabricating an electrical medical lead adapted to be implanted within the body at an implantation site to conduct electrical stimulation from an implantable stimulator to the site and to conduct electrical signals of the body from the site to the implantable or external stimulator comprising:

forming an elongated lead body extending from a lead body proximal end to a lead body distal end enclosing a lead conductor;

forming a lead connector element at the lead body proximal end;

electrically coupling the lead conductor to the first lead connector element fabricating an active fixation helix by;

forming a conductive wire into a helix comprising at least one coil turn wound about a helix lumen, the helix extending from a helix attachment end to a distal end terminating in a helix tip shaped to penetrate body tissue when the helix is screwed into body tissue to secure fixation to the implantation site; and

applying a layer of insulation over at least a portion of an inner helical surface of each coil turn disposed toward the helix lumen, whereby at least a portion of an outer helical surface of each coil turn is uninsulated;

attaching the fixation end of the fixation helix to the lead body distal end; and

electrically coupling the fixation helix to the lead conductor,

whereby the uninsulated outer helical surface is disposed toward body tissue away from the helix lumen to function as an outer helical electrode.

19. The method of claim 18, wherein:

the helix forming step comprises forming a plurality of coil turns wound in a constant pitch and coil diameter defining a helix lumen diameter and a helix outer diameter and a space between facing surfaces of adjacent turns; and

the applying step comprises;

providing a masking tube having a tube wall, a tube lumen, a tube length, and a tube lumen diameter correlated with the helix outer diameter;

fitting the helix turns into the tube lumen with the outer helical surface of each coil turn in contact with the tube wall and masked by the masking tube; and

applying the insulating material into the tube lumen to cover the inner helical surface of each coil turn within the tube lumen.

20. The method of claim 19, wherein the applying step comprises depositing a polymer selected from the group consisting of silicone rubber, parylene, polyurethane, polyacrylate, polymethacrylate, polyester, polyamide, polyether, polysiloxane, and polyepoxide upon the inner helical surface of each coil turn within the tube lumen.

21. The method of claim 19, wherein the applying step comprises applying a steroid selected from the group consisting of derivatives of dexamethasone, dexamethasone sodium phosphate, beclomethasone diproprionate, and dexamethasone acetate onto or incorporated into at least a portion of the insulating layer.

22. The method of claim 18, wherein:

the helix forming step comprises forming a plurality of coil turns wound in a constant pitch and coil diameter defining a helix lumen diameter and a helix outer diameter and a space between facing surfaces of adjacent turns; and

the applying step comprises;

providing a masking tube having a tube wall, a tube lumen, a tube length, a tube lumen diameter correlated with the helix outer diameter, and at least one tube wall aperture through the tube wall to the tube lumen;

fitting the helix turns into the tube lumen with the outer helical surface of each coil turn in contact with the tube wall and masked by the masking tube and at least one portion of the outer helical surface exposed through the tube wall aperture; and

applying the insulating material into the tube lumen to cover the inner helical surface of each coil turn within the tube lumen and through the tube wall aperture,

whereby the uninsulated helical outer surface is interrupted by the insulating layer applied through the tube wall aperture onto the helical outer surface.

23. The method of claim 22, wherein the applying step comprises depositing a polymer selected from the group consisting of silicone rubber, parylene, polyurethane, polyacrylate, polymethacrylate, polyester, polyamide, polyether, polysiloxane, and polyepoxide upon the inner helical surface of each coil turn within the tube lumen.

24. The method of claim 22, wherein the applying step comprises applying a steroid selected from the group consisting of derivatives of dexamethasone, dexamethasone sodium phosphate, beclomethasone diproprionate, and dexamethasone acetate onto or incorporated into at least a portion of the insulating layer.

25. The method of claim 18, wherein the applying step comprises depositing a polymer selected from the group consisting of silicone rubber, parylene, polyurethane, polyacrylate, polymethacrylate, polyester, polyamide, polyether, polysiloxane, and polyepoxide upon the inner helical surface of each coil turn within the tube lumen.

26. The method of claim 18, further comprising applying a steroid selected from the group consisting of derivatives of dexamethasone, dexamethasone sodium phosphate, beclomethasone diproprionate, and dexamethasone acetate onto or incorporated into at least a portion of the insulating layer.

27. The method of claim 18, wherein the step of fabricating an active fixation helix comprises

forming a wire of platinum metal or a platinum alloy into the coil and coating the coil outer surface with a coating selected from the group consisting of titanium nitride, iridium oxide, platinum black, and carbon nanotubes

28. The method of claim 18, wherein the applying step comprises applying the layer of insulation over at least a portion of an inner helical surface of each coil turn disposed toward the helix lumen, the uninsulated helical outer surface is in a continuous band extending substantially between the point of attachment to the helix tip.

29. The method of claim 28, wherein the applying step comprises applying the layer of insulation such that the uninsulated helical outer surface has a surface area in the range of about 10% to about 50% of the total surface area of the helix.

30. The method of claim 18, wherein the applying step comprises applying the layer of insulation over at least a portion of an inner helical surface of each coil turn disposed toward the helix lumen such that the uninsulated helical outer surface has a surface area in the range of about 10% to about 50% of the total surface area of the helix.

31. The method of claim 30, wherein the applying step comprises applying the layer of insulation over at least a portion of the helical outer surface.

32. The method of claim 18, wherein the applying step comprises applying the layer of insulation over at least a portion of the helical outer surface.