Load-carrying body for reducing torsional and tensile loading on electronic components in an implantable medical electrical lead

Abstract

A load-carrying body for reducing torsional and tensile loading on electrical components in an implantable medical electrical lead includes an electronic component disposed in-line with the implantable medical electrical lead, and a casing for the electronic component. The electronic component has a proximal end conductively coupled to a lead conductor and a distal end conductively coupled to a lead electrode. The casing is mechanically coupled to the lead so as to isolate the electrical component from torque or tensile loads applied to the lead, the lead electrode, or both.

Description

rotates, it rotate, helix electrode engages a guide 62 which causes the helix 36 to extend and screw into body tissue. The guide 62 may be formed as part of the collar 50 and engages the tip electrode 36 when the tip conductor 42 is rotated. The rotation causes the helical tip electrode 36 to rotate within the collar 50 and thereby translate in a forward manner. At the same time the tip electrode 36 is advancing relative to the collar 50, it is engaging with body tissue by being screwed directly into the tissue to thereby form an attachment. The tip electrode 36 can be rotated in the opposite direction by rotating the tip conductor 42 and thereby disengaged from the tissue for removal and/or reattachment at a different location. This is a method of active affixation which is well known in the art.

An O-ring 64 is disposed on the proximal end of and subassembly 58. In this case, the seal 64 is only to prevent the intrusion of ionic containing body fluids into the interior of lead body 46. In this case, a conformal coating 66 is disposed over the exterior of the casing 52 and all the way over the pin 54 and even over a portion of a conductive drive shaft 60. The conformal coating 66 may be a material for electrical isolation and/or also aid in reducing friction. The conformal coating 66 may also be a dielectric ceramic coating that can be applied in a multitude of ways, such as by sputtering, chemical vapor deposition, physical vapor deposition, or dipping in a chemical solution. The conformal coating 66 may also be made of a variety of materials sufficient to provide insulation, such as alumina. In another exemplary embodiment and to provide further electrical isolation, the casing 52 can also be manufactured as a ceramic tube, and also from materials such as alumina. It is to be understood that such a ceramic tube casing 52 can be used with or without the conformal coating 66.

The lead tip conductor 42, the casing sub-assembly 58 and the distal helix 36 are shown in the retracted position. As the helix is extended, the conformal coating 66 on the inside diameter of seal 64 will slide back and forth as it is part of the drive shaft 60. This provides a high degree of electrical resistance or isolation between the terminal pins 54 and 56 such that undesirable currents do not flow through body fluids from end to end outside of the electronic component casing 52. Seal supports 68 abut the seal 64 on both ends and fix the seal 64 in place. The seal supports 68 can be made from a range of materials, including but not limited to a polymer, polyurethane, metal, elastomer, ceramic, composite or any other suitable material.

FIG. 11 is generally taken from section 11-11 of FIG. 10. Shown is the interior of the translatable casing 52 illustrating bandstop filter components L and C. Terminal pins 54 and 56 extend in non-conductive relationship with the translatable casing 52. Hermetic seals 70 and 72 are shown which form a hermetic seal between the pins 54 and 56 and the translatable casing 52. This protects the inductor L and capacitor C (or other electronic components) from intrusion of body fluids. It is well known in the art that intrusion of moisture, body fluids or other contaminants can cause electronic circuits to short out. It is not an absolute requirement that the translatable casing 52 be hermetically sealed. Electronic components, such as inductor L and capacitor C components, could be utilized that are inherently non-toxic and biocompatible. Components for direct body fluid exposure are described in U.S. Pat. No. 7,535,693 the contents of which are hereby incorporated by reference. However, in the case where there are hermetic seals 70, 72, it is important that the hermetic seals be protected from damage due to excessive torque or tensile loads. In the case where there are no hermetic seals, it's even more important that delicate electronic components be protected from damaging torque or tensile stresses.

The present invention is applicable to any type of active or electronic circuits that may be disposed in or adjacent to a translatable electronic casing 52. The flexible seal 64 of FIG. 10 prevents the entrance of ionic body fluids into the inside of the lead body 46. The seal 64 can be formed in a multitude of ways appreciated by those skilled in the art, such as multiple wipers, o-rings, thin disks or sheets, and various molded profiles. See, for example, U.S. application Ser. No. 12/873,862, the contents of which are incorporated herein.

There is a secondary optional O-ring seal 74 as shown in FIG. 10. The O-ring seal 74 is disposed between the inside diameter of the lead collar 50 and the outside diameter of the electronic component casing 52. The purpose of seal 64 and the O-ring seal 74 is to ensure that ionic body fluids cannot be disposed across the important electrical path between pins 54 and 56. Ionic body fluids could represent a parallel path as low as 80 ohms. Over time, due to bulk permeability, body fluids will penetrate into the interior of the lead body 46. However, this is an osmotic type of action. The resulting fluids that would occur over long periods of time inside the lead body 46 would be distilled and free of ionic contaminants (de-ionized). This means that they would be less conductive of high frequency electrical signals from one end to the other of the electronic component casing 52. The presence of optional O-ring 74 is desirable in that it also presents a high impedance to such a parallel circuit path. The casing 52 may also have a conformal insulative coating 66 for further electrically isolating terminals 54 and 56 such that a parallel path through body fluid is further impeded. The insulative coating may be formed from any suitable material, such as a dielectric material, including, but not limited to parylene, ETFE, PTFE, polyamide, polyurethane and silicone. It will be understood that the exemplary embodiment of FIG. 10 may work with or without such coatings.

FIG. 12 is an electrical schematic illustration of the bandstop filter illustrated in FIG. 11.

FIG. 13 is a perspective illustration of an exemplary unitary torque coupler 76 embodying the present invention. The torque coupler 76 is made of a rigid and non-conductive material. The form of the torque coupler 76 may vary and be formed to match the medical electrical lead's 46 collar 50. A helical electrode tip 36 is attached to the distal torque coupler pin 78. A proximal torque coupler pin 80 is attached to drive shaft 60. Torque and tensile loads applied to the lead 46 are transmitted through the unitary torque coupler 76 while not being transmitted within the electronic components 44 located inside. The torque coupler 76 also protects the mechanically sensitive hermetic seals 70 and 72.

FIG. 14 is a sectional view taken from section 14-14 of FIG. 13. As was previously mentioned, the torque coupler 76 is of a rigid and insulative material. It has sufficient strength properties to transmit torque and tensile loads thereby protecting the casing 52 of the electronic module 44. There is a unique coupling mechanism provided by the proximal torque coupler pin 80, which is generally electrically and mechanically attached to proximal pin 54 either by laser welding, brazing of the like. In order to mechanically grasp and adhere to the material of the torque coupler 76, it may have one or more disc-like rings 82 in order to increase its surface area. The rings may have sprocket spokes to lock it to the unitary torque coupler. In general, there is more torque on the proximal side than on the distal side. Accordingly, in the preferred embodiment as shown in FIG. 14, there would be two friction rings 82 on the proximal side and only one on the distal side. The casing 52 is hermetically sealed by hermetic seals 70 and 72. The unitary torque coupler 76 not only protects the delicate electronics 44 inside of the casing 52, but it also protects the delicate hermetic seals 70 and 72. An optional overall insulative coating 66 may be applied. The torque coupler 76 may be formed by a mold into which a biocompatible epoxy is poured and then later cured into a hard state.

During implantation by a physician, the lead body 46 is held in place while the center conductor 42 is rotated using a physician torque tool. As the entire assembly rotates, it is pushed forward by guide 62 which causes the distal helix end 36 to protrude and screw into body tissue. The torque that is applied to the lead conductor 42 is transmitted to drive shaft 60 and in turn to the proximal torque coupler pin 80. The torque is then transmitted mostly into the rigid body of the torque coupler 76 itself thereby bypassing pins 54 and 56. The torque that is transmitted by the torque coupler 76 is further transmitted to the distal torque coupler pin 78. This arrangement, importantly, protects the casing 52, the electronics 44 and the sensitive hermetic seals 70 and 72.

FIG. 15 shows an alternate torque coupler arrangement. In this case, the torque coupler is divided into two discrete torque couplers, one consisting of a proximal torque coupler 84 and the other consisting of a distal torque coupler 86. In this case, the torque couplers 84, 86 are also of a rigid insulative material. They could be poured in place, such as a non-conductive thermal-setting epoxy or polyimide. They could also be pre-machined from hard plastics, ceramics or the like. In addition, ceramic powders could be pressed into a fixture and then sintered at high temperature in order to make a rigid non-conductive torque coupler.

Each of the distal and proximal torque coupler pins 78 and 80 includes a locking sprocket 88. Similarly, each of the proximal and distal torque couplers 84 and 86 include a locking sprocket-receiving recess 90 configured for receiving a respective locking sprocket 88 therein. These features are better illustrated in FIG. 16, which also shows that the proximal and distal torque couplers 84 and 86 also have a castle parapet configuration 92 on one side for mating reception with a similar castle parapet structure 94 provided on respective ends of the casing 52. In this case, the casing 52 is of a strong and rigid material such that it will not deform during application of torsional loads. These gear/sprocket-like features of the torque couplers 84, 86, torque coupler pins 78, 80 and the casing 52 prevent the torque couplers 84 and 86 from slipping relative to the casing 52 and the respective pins 78 and 80 while under load. In a preferred embodiment, an adhesive (not shown) would be applied to the sprocket 86 engagement surfaces 90 and 92 so that the entire system would be also resistant to tensile loads. In other words, tensile and torque loads applied to the pins 78 and 80 are transmitted through the torque couplers 84 and 86 directly to the casing 52, thereby isolating the electrical components 44 from such torque or tensile loads.

FIG. 16 is an exploded view of various components disposed within the lead body 46 and the collar 50, from FIG. 15. Beginning on the left hand or proximal side one can see the lead tip conductor 42 which attaches to the conductive drive shaft 60. The conductive drive shaft 60 (which is optional) is secured by welding, brazing or the like, to the proximal torque coupler pin 80. The torque coupler pin 80 includes a locking sprocket 88 configured for locking reception within the locking sprocket recess 90 of the proximal torque coupler 84. The proximal pin 54 is fixed within a pin receiving recess 96 provided within the proximal torque coupler pin 80 (see FIG. 15). The distal end of the pin 54 includes a head 98 to which the electronic component (bandstop filter 44) is conductively coupled. Similarly, the distal pin 56 is disposed within a pin receiving recess 100 (FIG. 15) provided within the distal torque coupler pin 78 and is fixed in place by means of a weld or the like. A distal pin 56 extends through the distal hermetic seal 72, and includes a head 102 which is conductively coupled to the electronic components (bandstop filter 44) disposed within the casing 52. A sprocket 88 is configured for locking reception within the locking sprocket recess 90 provided in the distal torque coupler 86. The tip electrode 36 is fixed to the distal torque coupler pin 78. Importantly, the proximal and distal torque couplers 84 and 86 each include a castle parapet structure 92 that mates with a corresponding castle parapet structure 94 provided on respective ends of the casing 52. As described previously, this structure ensures that the electrical components within the casing 52 are isolated from torque or tensile loads applied to the lead 14, the lead electrode 36, or both.

FIG. 17 is a sectional view similar to FIGS. 14 and 15. In this case, the pin 54 has a unique cup shape to receive a conductive shaft 104. This shaft 104 is attached to a ferrule 106 which is in turn connected to the lead conductor 42. Since it is very important that torque not be transmitted from lead conductor 42 through the shaft 104 to the pin 54, hermetic terminals this small generally consist of a single sapphire ceramic or an alumina ceramic. Metallization is attached to these pins by first sputtering and then gold brazing. An elongated torque coupler 108 is connected to the ferrule 106 and is in turn connected to the parapet structure 94 that is located on the end of the casing 52 in order to lock it in place. The elongated torque coupler 108 operates in accordance with the present invention so that torque or tensile loads that are transmitted via the lead conductor 42 bypass the conductive shaft 104 and the hermetic seal 70.

From the foregoing, it will be appreciated that the present invention relates to a lead body adapted for in-vivo implantation in a living subject, said lead body comprising a proximal end configured for electrical and mechanical connection to a therapy delivery or monitoring device, and a distal end which is connected to a translatable active fixation electrode in contact with body tissues. The distal end of the lead body encompasses a collar in which a casing is enclosed. The casing includes electronic components which can either be active or passive. One or both ends of the casing 52 (or alternatively the entire casing), is protected by a novel torque coupler. The torque coupler protects either the sensitive hermetic seals of casing 52 or the internal electronic components 44 from damage due to torque applied to torque or tensile loads applied to lead conductor 42, the tip electrode 36, or both. In a preferred embodiment, the casing includes a passive inductor and capacitor element configured to form a parallel resonant L-C bandstop filter. The casing is translatable within the collar, which causes a distal helix electrode to rotate and literally be screwed into body tissue. The helix electrode is also known as an active fixation electrode. The casing is part of a casing assembly which includes a seal which is disposed between the casing assembly and the collar whereby the seal prevents passage of ionic body fluids in the living subject into the lead body fluid distal end. Conformal coatings can be placed over the translatable casing so that high resistance path is provided from one end of the active or passive electronic circuit to the other. The active or passive electronic circuit can include L-C bandstop filters, L-C trap filters, low pass filters, electronic sensors, passive or active electronic switches, MEMS switches, pin diode switches, non-linear circuit elements, such as diodes and the like. The conformal coating may be a dielectric material for electrical isolation and/or also aid in reducing friction.

Although several embodiments have been described in detail for purposes of illustration, various modifications may be made to each without departing from the scope and spirit of the invention.

Claims

1. A load-carrying body for reducing torsional and tensile loading on electronic components in an An implantable medical electrical lead, comprising:

a) a lead conductor extending from a proximal lead conductor end to a distal lead conductor end, wherein the proximal lead conductor end is connectable to an implantable pulse generator;

b) an electrode configured for contact with body tissue;

c) an electronic component disposed in-line with an implantable medical electrical lead, the electronic component having a proximal electronic component end conductively and physically coupled to a the distal lead conductor end, and a distal electronic component end conductively and physically coupled to a lead the electrode; and

d) a casing for rigid, torque bearing member supporting the electronic component, wherein a proximal end of the casing being torque bearing member is mechanically, but not conductively coupled to the distal lead conductor end, and a distal end of the torque bearing member is mechanically, but not conductively coupled to the electrode, and

so as to isolate e) wherein the torque bearing member isolates the electronic component from torque or tensile loads applied to the lead conductor, the lead electrode, or both.

2. The load-carrying body implantable medical electrical lead of claim 1, including wherein a proximal torque coupler disposed is mechanically and conductively coupled between and to the lead conductor and the casing electronic component.

3. The load-carrying body implantable medical electrical lead of claim 2, wherein the casing includes a proximal hermetic a seal isolated by conductively isolates the proximal torque coupler from the torque or tensile loads applied to the lead bearing member.

4. The load-carrying body implantable medical electrical lead of claim 2, wherein the proximal torque coupler includes a proximal pin mechanically attached to the lead conductor and conductively coupled to the lead conductor and the electronic component.

5. The load-carrying body implantable medical electrical lead of claim 4, including wherein a drive shaft is disposed between the proximal pin and the lead conductor.

6. The load-carrying body implantable medical electrical lead of claim 1, including wherein a distal torque coupler disposed mechanically and conductively couples between and to the lead electrode and the casing electronic component.

7. The load-carrying body implantable medical electrical lead of claim 6, wherein the casing includes a distal hermetic a seal isolated by conductively isolates the distal torque coupler from the torque or tensile loads applied to the lead electrode bearing member.

8. The load-carrying body implantable medical electrical lead of any of claims claim 1-6, wherein the electronic component comprises is selected from the group consisting of a bandstop filter, an electronic switch, a MEMs switch, a diode array, a multiplexer, a pin diode, a capacitor, a resistor, an inductor, an electronic sensor, or any combination and combinations thereof.

9. The load-carrying body implantable medical electrical lead of claim 6, wherein the distal torque coupler includes a distal pin mechanically attached to the lead electrode and conductively coupled to the lead electrode and the electronic component.

10. The load-carrying body implantable medical electrical lead of any of claims claim 1-6, including wherein a collar is disposed at a distal end of the implantable medical electrical lead, and wherein the casing torque bearing member is disposed within the collar, and wherein the torque bearing member is translatable along a longitudinal axis of the collar.

11. The load-carrying body implantable medical electrical lead of claim 10, including wherein a seal is disposed between the casing torque bearing member and the collar for preventing, the seal being configured to prevent passage of ionic fluid into the lead through its a distal end of the collar.

12. The load-carrying body implantable medical electrical lead of claim 11, wherein the seal disposed between the torque bearing member and the collar is disposed at a distal end, at a proximal end, or along a middle of the casing torque bearing member.

13. The load-carrying body implantable medical electrical lead of claim 12 6, including wherein a collar is disposed at a distal end of the implantable medical electrical lead, and wherein the distal torque coupler is disposed within the collar, and wherein the distal torque coupler is translatable along a longitudinal axis of the collar.

14. The load-carrying body implantable medical electrical lead of claim 13, including wherein a seal is disposed between the proximal torque coupler and the collar for preventing, the seal being configured to prevent passage of bionic ionic fluid into the lead through its a distal end of the collar.

15. The load-carrying body implantable medical electrical lead of claim 11, wherein the seal disposed between the torque bearing member and the collar is fixed relative to the casing torque bearing member.

16. The load-carrying body implantable medical electrical lead of claim 11, wherein the seal disposed between the torque bearing member and the collar is fixed relative to the collar.

17. The load-carrying body implantable medical electrical lead of claim 10, including wherein an insulative conformal coating is disposed about at least a portion of the casing torque bearing member.

18. The load-carrying body implantable medical electrical lead of claim 17, wherein the conformal coating comprises a dielectric ceramic coating.

19. The load-carrying body implantable medical electrical lead of claim 17, wherein the conformal coating is characterized as having been applied by one of the group consisting of sputtering, chemical vapor deposition, physical vapor deposition, dipping in or a chemical solution and applying a chemical solution.

20. The load-carrying body implantable medical electrical lead of claim 17, wherein the conformal coating comprises alumina or parylene.

21. The load-carrying body implantable medical electrical lead of claim 10 1, wherein the casing torque bearing member comprises a dielectric ceramic coating.

22. The load-carrying body implantable medical electrical lead of claim 10 1, wherein the casing torque bearing member comprises alumina.

23. The load-carrying body implantable medical electrical lead of claim 1, including wherein a unitary torque coupler is disposed over the casing torque bearing member.