Medical lead conductor fracture visualization method and apparatus

• US 6,295,476 B1
• Filed: 11/01/1999
• Issued: 09/25/2001
• Est. Priority Date: 11/01/1999
• Status: Expired due to Fees

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Schaenzer, David G.
• Primary Examiner(s): Getzow, Scott M.
• Application Number:
  US09/430,864
• Time in Patent Office: 694 Days
• Field of Search: 607/122, 607/123, 607/27, 607/28, 600/3, 600/377, 600/374
• US Class Current: 607/122
• CPC Class Codes: A61N 1/056 Transvascular endocardial electrode systems

Abstract

Methods for sensing or electrical stimulation of body organs or tissues are disclosed wherein a lead conductor wire or filament of a stranded lead conductor generates a radioactive emission when it is fractured sufficiently or is completely broken. The conductor wire or filament is formed of an inner core and an outer sheath surrounding the inner core, wherein the inner core is irradiated or is formed of a radioactive isotope in an alloy that provides an enhanced radiopaque aura when the sheath is fractured and the inner core is exposed. When the conductor wire or filament is intact, the radioactive inner core is fully encased within the outer sheath, and the outer sheath blocks or reduces radioactive emission along its length to a constant, relatively low level. In use, the emission is detected externally to the body, and the detection signifies that a fracture or break has occurred. Such leads preferably comprise cardiac leads for delivering electrical stimulation to the heart, e.g., pacing pulses and cardioversion/defibrillation shocks, and/or sensing the cardiac electrogram, having multiple lead conductors encased in a lead body subject to fracture under stress. The lead conductors can comprise mono-filar or multi-filar, parallel wound, coiled wires that arranged in a co-axial manner or in a side-by-side arrangement within the lead body. Or the straight or coiled lead conductors can be formed of a strand comprising a plurality of outer filaments wound helically about a central core filament or of a cable comprising a plurality of such peripheral strands wound helically about a central core strand. At least the outer filaments of a stranded conductor and peripheral strands of a conductor cable are formed with the radioactive core.

Claims

1. In a medical electrical lead for implantation within the body of the type comprising an elongated lead body enclosing at least one lead conductor extending in a lead body lumen between an electrode and a connector element, wherein the lead body and enclosed lead conductor are subject to stress that may cause the lead conductor to be fractured or broken, the improvement in the lead conductor comprising:

a source of radiation incorporated within the lead conductor that emits radiation from a fracture of break in the lead conductor.

2. The medical electrical lead of claim 1, wherein:

the lead conductor further comprises a conductor wire or filament formed of elongated inner core and an outer sheath surrounding the inner core; and

the source of radiation comprises a radioactive isotope forming part of the inner core.

3. The medical electrical lead of claim 2, wherein the elongated inner core is fully encased within the outer sheath, and the outer sheath blocks or reduces radioactive emission along its length to a constant, relatively low level while the conductor wire or filament is intact.

4. The medical electrical lead of claim 3, wherein the lead conductor comprises a mono-filar coiled wire.

5. The medical electrical lead of claim 3, wherein the lead conductor comprises a multi-filar, parallel wound, coiled wire.

6. The medical electrical lead of claim 1, wherein:

the lead conductor comprises a strand comprising a plurality of outer filaments wound helically about a central core filament,

at least one of the filaments is formed of an elongated inner core and an outer sheath surrounding the inner core; and

the source of radiation further comprises a radioactive isotope forming part of the inner core.

7. The medical electrical lead of claim 6, wherein the lead conductor comprises a cable formed of a plurality of said strands arranged such that a central core strand is surrounded by a plurality of peripheral strands wound helically about said central core filament.

8. The medical electrical lead of claim 1, wherein:

the lead conductor comprises a strand comprising a plurality of outer filaments wound helically about a central core filament,

the outer filaments are each formed of an elongated inner core and an outer sheath surrounding the inner core; and

the source of radiation further comprises a radioactive isotope forming part of the inner core of at least one of the filaments.

9. The medical electrical lead of claim 1, wherein:

the lead conductor comprises a strand comprising a plurality of outer filaments wound helically about a central core filament,

each of the filaments is formed of an elongated inner core and an outer sheath surrounding the inner core; and

the source of radiation comprises a radioactive isotope forming part of each of the inner cores.

10. The medical electrical lead of claim 1, wherein:

the lead conductor comprises a cable formed of a plurality of strands of filaments, each strand comprising a plurality of outer filaments wound helically about a central core filament;

each of the plurality of strands comprises a central core strand and a plurality of peripheral strands wound helically about said central core filament;

at least one of the filaments is formed of elongated inner core and an outer sheath surrounding the inner core; and

the source of radiation further comprises a radioactive alloy forming part of the inner core.

11. The medical electrical lead of claim 1, wherein:

the lead conductor comprises a cable formed of a plurality of strands of filaments, each strand comprising a plurality of outer filaments wound helically about a central core filament;

each of the plurality of strands comprises a central core strand and a plurality of peripheral strands wound helically about said central core strand;

each of the filaments forming the plurality of peripheral strands is formed of an elongated inner core and an outer sheath surrounding the inner core; and

the source of radiation further comprises a radioactive alloy forming part of at least one of the inner cores.

12. The medical electrical lead of claim 1, wherein:

the lead conductor comprises a cable formed of a plurality of strands of filaments, each strand comprising a plurality of outer filaments wound helically about a central core filament;

each of the plurality of strands comprises a central core strand and a plurality of peripheral strands wound helically about said central core strand;

each of the filaments forming the plurality of strands is formed of an elongated inner core and an outer sheath surrounding the inner core; and

the source of radiation further comprises a radioactive alloy forming part of each of the inner cores.

13. A method of determining when a lead conductor of a medical electrical lead, of the type comprising an elongated lead body enclosing at least one lead conductor extending in a lead body lumen between an electrode and a connector element that is implanted within the body, is fractured, the method comprising the steps of:

incorporating a source of radiation within the lead conductor that emits radiation from a fracture of break in the lead conductor;

implanting the lead in the body; and

detecting any such emission of radiation from outside the body.

14. The method of claim 13, wherein the incorporating step further comprises the steps of:

forming the lead conductor of a conductor wire or filament with an elongated inner core and an outer sheath surrounding the inner core; and

incorporating said source of radiation within the inner core.

15. The method of claim 13, wherein the lead conductor forming step further comprises the step of fully encasing the elongated inner core within the outer sheath.

16. The method of claim 13, wherein the incorporating step further comprises the steps of:

forming the lead conductor of a single conductor wire with an elongated inner core surrounded by an outer sheath;

incorporating said source of radiation within the inner core; and

winding the lead conductor into a coil.

17. The method of claim 13, wherein the incorporating step further comprises the steps of:

forming the lead conductor of a plurality of conductor wires with each conductor wire having an elongated inner core surrounded by an outer sheath;

incorporating said source of radiation within the inner cores; and

parallel winding the plurality of lead conductors into a multi-filar, parallel wound, coiled wire.

18. The method of claim 13, wherein the incorporating step further comprises the steps of:

forming at least one filament of an elongated inner core and an outer sheath surrounding the inner core;

incorporating said source of radiation within the inner; and

winding a plurality of outer filaments helically about a central core filament the filament to form a strand of filaments.

19. The method of claim 18, wherein the incorporating step further comprises the step of winding a plurality of peripheral strands helically about a central core strand to form a cable of strands.

20. The method of claim 13, wherein the incorporating step further comprises the steps of:

forming a plurality of filaments each having an elongated inner core and an outer sheath surrounding the inner core;

incorporating said source of radiation within the inner; and

winding a plurality of outer filaments helically about a central core filament the filament to form a strand of filaments.

21. The method of claim 20, wherein the incorporating step further comprises the step of winding a plurality of peripheral strands helically about a central core strand to form a cable of strands.