HIGH IMPEDANCE ACTIVE FIXATION ELECTRODE OF AN ELECTRICAL MEDICAL LEAD

• US 20100292768A1
• Filed: 05/18/2010
• Published: 11/18/2010
• Est. Priority Date: 12/03/2004
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Coles, James A. JR., Sommer, John L., Sigg, Daniel C.
• Granted Patent: US 8,332,051 B2
• Time in Patent Office: Days
• US Class Current: 607/116
• 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 a plurality of coil turns wound about a helix lumen, the fixation helix 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,

the plurality of coil turns each having a coil outer diameter defining a helix outer diameter and a coil inner diameter defining a helix lumen diameter; and

a continuous layer of insulation extending without interruption from the helix attachment end to the helix tip covering only an inner helical surface of each of the coil turns and disposed to face inward toward the helix lumen;

wherein at least a portion of an outer helical surface extending along the helix outer diameter each coil turn is uninsulated and facing opposite the inner helical surface covered by the layer of insulation.

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 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.

10. 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 a conductive wire formed into a coil comprising a plurality of coil turns wound about a helix lumen, the fixation helix 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,

the conductive wire having a circumferential surface and each coil turn formed by the conductive wire having a coil outer diameter defining a helix outer diameter and a coil inner diameter defining a helix lumen diameter;

a layer of insulation applied to the circumferential surface of the conductive wire, the insulating layer extending only part way around the circumferential surface of the conductive wire to cover the coil inner diameter without covering the coil outer diameter directly opposite the covered coil inner diameter of each coil turn,

wherein the insulating layer covers an inner helical surface disposed toward the helix lumen of each coil turn and an outer helical surface opposite the insulated inner helical surface extending along the helix outer diameter 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.

11. The electrical medical lead of claim 10, 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.

12. The electrical medical lead of claim 10, 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

13. The electrical medical lead of claim 10, wherein the uninsulated helical outer surface is in a continuous band extending substantially between the point of attachment to the helix tip.

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

15. 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 a plurality of coil turns wound about a helix lumen, the fixation helix 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,

the fixation helix having an outer surface and an inner surface forming a helix lumen;

each coil turn of the fixation helix being formed from a substantially circular wire having a circumferential surface area; and

a layer of insulation extending without interruption from the helix attachment end to the helix tip, the insulation layer covering a substantial portion of the circumferential surface area of the wire forming each coil turn to define a portion of the circumferential surface area of the wire that is uninsulated so as to cover only the helix inner surface and leave an exposed helix outer surface, wherein only the exposed helix outer surface functions as an electrode disposed toward body tissue away from the helix lumen.

16. The electrical medical lead of claim 15, 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.

17. The electrical medical lead of claim 15, 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

18. The electrical medical lead of claim 15, wherein the uninsulated helical outer surface is in a continuous band extending substantially between the point of attachment to the helix tip.

19. The electrical medical lead of claim 15, wherein the uninsulated helical outer surface has a surface area in the range of about 10% to about 50% of the total surface area.