WO2002049716A1

WO2002049716A1 - An electrically conductive lead and a method of producing such a lead

Info

Publication number: WO2002049716A1
Application number: PCT/SE2001/002821
Authority: WO
Inventors: Rolf Hill; Eva Micski; Sven Kalling; Henrik Djurling; Martin Obel; Gunnar Magnusson; Maria Wargelius
Original assignee: St. Jude Medical Ab
Priority date: 2000-12-21
Filing date: 2001-12-18
Publication date: 2002-06-27
Also published as: SE0004812D0

Abstract

The invention concerns an electrically conductive lead suitable to be implanted in a human or animal body. The lead comprises a proximal end portion designed to be attached to a device and a distal end portion comprising at least one electrode member (12) for emitting and/or sensing electrical signals. The lead also has an elongated body extending between said proximal end portion and said distal end portion. The distal end portion comprises at least one cavity (26) having an opening (28) arranged such that the cavity (26) is open to the exterior of the distal end portion. A drug dispensing member (30) is located in the cavity (26). The drug dispensing member (30) constitutes or comprises a gel that includes a drug, which is adapted to be released into said human or animal body. The invention also concerns a method of producing such a lead.

Description

An electrically conductive lead and a method of producing such a lead

BACKGROUND OF THE INVENTION

1 . Field of the invention

The present invention relates to leads which are electrically conductive and which are suitable to be implanted in a human or animal body. Such leads may for example be used to conduct electrical stimulation pulses from an implanted heart stimulating device to the heart of said human or animal body. Leads may, however, also be used in connection with other kinds of medical devices. Preferably the heart electrode leads are adapted to be insertable via the vascular system into the human or animal heart. Such heart electrode leads are particularly suitable for intracardial stimulation of the heart with the help of an implantable pacemaker or defibrillator. The invention concerns both a lead as such and a method of producing a lead.

1. Description of the prior art

A large number of different leads are known in the art. A lead normally has a proximal end portion to be connected to a device, for example a heart-stimulating device, and a distal end portion that is to be positioned at a predetermined position in the body, usually in or at the heart. A heart electrode lead may be unipolar or bipolar. A unipolar lead has only one single electrode member usually arranged at the tip of the distal end portion of the lead. A bipolar lead has two electric poles. Also this kind of electrode lead usually has one electrode member located at the tip at the distal end portion of the lead. The lead has at least one electric conductor, which extends from the proximal end portion to the electrode member at the distal end portion.

For example in case of a lead for a heart stimulating device, it is known that when a lead has been implanted into or at the heart, the stimulation threshold is higher during a certain time after the implantation and then becomes lower. It is also known that this stimulation threshold may be lowered by providing a drug, such as a steroid, at the distal end portion of the lead. The drug is arranged such that it will be dispensed to the surrounding body tissue over a period of time.

US-A-5 103 837 describes that a coating including a drug is provided on an electrode member of titanium nitride.

US-A-4 819 661 describes different leads with helical fixation members. A drug impregnated matrix, preferably of a biocompatible silicon adhesive, is positioned in a cavity at the distal end portion of the lead. The document describes that a drug impregnated matrix in a viscous or malleable state may be injected into a cavity whereafter the matrix cures and solidifies.

US-A-5 003 992 also describes a lead with a helical fixation member. A plug made of a polymer with a drug is located in a cavity at the distal end portion of the lead.

US-A-5 002 067 discloses a lead with a helical fixation member. A cylindrical plug fabricated of a silicon-based polymer incorporating an anti-inflammatory drug is positioned in a cavity at the distal end portion of the lead. The fixation helix may also be provided with a groove along which the drug may be released.

US-A-4 972 848 describes a lead with a helical fixation means. A monolithic controlled release device made of a polymer and incorporating a drug is provided in a cavity at the distal end portion of the lead. US-A-4 506 680 describes a sintered metal electrode member located at the distal end of the lead. In a cavity inside of this electrode member a polymer impregnated with a drug is positioned.

US-A-4 577 642 describes a lead with a porous sintered metal electrode member located at the distal end portion of the lead. In a cavity inside of the electrode member, a drug is retained in a solid plug or a powder wherein the drug is compounded with an appropriate molecular sieve material.

US-A-6 038 482 discloses a lead with an electrode member positioned at the distal end portion of the lead. The electrode member has an interior cavity and a bore extending between the interior cavity and the exterior surface of the electrode member. A matrix member with a drug is positioned in the interior cavity. The exterior surface of the electrode member is coated with a wetting agent with the same drug as in the matrix. The bore is filled with a wetting agent with the same drug as in the matrix.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a lead that is easy to produce and that includes a drug located in a cavity at the distal end portion of the lead. A second object is to provide a method of producing such a lead.

The first object is achieved by an electrically conductive lead suitable to be implanted in a human or animal body, the lead comprising: a proximal end portion designed to be attached to a device, a distal end portion comprising at least one electrode member for emitting and/or sensing electrical signals, an elongated body extending between said proximal end portion and said distal end portion, said distal end portion comprising at least one cavity having an opening arranged such that the cavity is open to the exterior of the distal end portion, a drug dispensing member located in said cavity, wherein said drug dispensing member constitutes or comprises a gel that includes a drug, which is adapted to be released into said human or animal body.

It is easy to apply the gel into to the drug dispensing member or into the cavity. Furthermore, a drug included in the gel can be released into the body. It should be noted that the drug dispensing member may consist only of the gel with the drug, but may also comprise another member, as will be explained below, in which the gel is located.

According to a preferred embodiment, said drug comprises an anti- inflammatory agent. Such an agent may for example be a steroid. It should however be noted that the invention is not limited to this kind of drug. Also other kinds of drugs may be used, for example drugs intended to counter thrombus formation or arrhythmias etc. The drug dispensing member could of course include a combination of different drugs.

According to a further embodiment, said drug dispensing member comprises a plastic foam material member in which said gel is provided. It is easy to hold the gel in such a member, and such a member is easy to position in the cavity.

According to another embodiment, said drug dispensing member includes a first part formed by said plastic foam material member in which the gel is provided and a second part which comprises said gel but not any substantial amount of said a plastic foam material, wherein said second part is provided on that side of said first part which is facing towards the exterior of said distal end portion. The drug in this second part will be released relatively quickly after the implantation of the lead into the body. It is advantageous that more drug is released during this first time period after implantation. The drug in the first part will be released more slowly over a longer time period. According to another embodiment, said drug dispensing member comprises an enclosure in which said gel is provided, which enclosure comprises holes through which said drug may be released into said human or animal body. This enclosure may safely hold the gel in position and may be easily positioned in the cavity.

According to a preferred embodiment, said enclosure is formed by a net structure. The net structure may thus have the form of a small net basket that may be positioned in the cavity.

According to another embodiment, said cavity and said drug dispensing member are designed such that the drug dispensing member is fixed by a snap-in closure in said cavity. This design makes it easy to position the drug dispensing member and the member is safely held in position.

According to another embodiment, said at least one electrode member comprises a first surface portion facing the exterior of the distal end portion of the lead and a second surface portion facing the interior of the lead, wherein said cavity is located such that said opening is located in said first surface portion. Preferably this first surface portion is positioned at the end tip of the distal end portion. The first surface portion preferably has a smooth curvature.

According to a preferred embodiment, said cavity is located such that the cavity does not extend to the second surface portion, such that it does not extend all the way through the electrode member, wherein the cavity does not have any opening towards the interior of the lead. There is therefore no risk that the drug or the gel will be released towards the interior of the lead. Instead, the drug can only be released out through the opening into the surrounding body tissue.

According to another embodiment, said cavity extends from said first surface portion and has a cross-sectional dimension at an intermediate position of said cavity which is smaller than the cross- sectional dimension of the cavity at a position located proximal of said intermediate position. By cross-sectional dimension is here meant the area of the cross-section perpendicular to the main direction in which the elongated lead extends. Since the cavity has a larger cross-sectional dimension towards the interior, a larger interior cavity is formed. This larger interior cavity may comprise a larger quantity of the gel and the drug for long term release into the body.

According to another embodiment said cavity extends from said first surface portion and has a cross-sectional dimension at an intermediate position of said cavity which is smaller than the cross- sectional dimension of the cavity at said first surface portion. This means that more gel with the drug can be located close to the first surface area. This has as a consequence that that more drug will be released during the initial time period after implantation.

According to an alternative embodiment said cavity has a cross- sectional dimension, which is essentially constant throughout said cavity. Such a cavity is easy to make and a drug dispensing member is easy to position in such a cavity.

According to another embodiment, the lead has a helical fixation means at said distal end portion. Normally such a helical fixation means constitutes an electrode member of the lead. This helical fixation means will be safely held in position in that part of the body where the distal end portion of the lead is to be positioned. It should be noted that the cavity may also in connection with such a helical fixation means extend to the distal end portion of the lead. The opening may for example be located in the helix of the helical fixation means. The cavity may also in this case have the different shapes described above in connection with a smooth distal electrode member.

The second object of the invention is achieved by a method of producing a an electrically conductive lead suitable to be implanted in a human or animal body and comprising a drug to be released into said body, the method comprising: providing an electrically conductive lead having a proximal end portion designed to be attached to a device, a distal end portion, which comprises at least one electrode member for emitting and/or sensing electrical signals, an elongated body extending between said proximal end portion and said distal end portion, wherein said lead is provided with at least one cavity in said distal end portion, which cavity has an opening arranged such that the cavity is open to the exterior of the distal end portion, providing a gel which includes said drug, adapted to be released into said human or animal body, and positioning said gel in said cavity.

Through this method, it is easy to produce a lead with a drug to be dispensed to the body. Since the gel is soft, it is easy to position the gel in the cavity or in a drug dispensing member which is then positioned in the cavity.

Different preferred manners of carrying out the method are defined in the claims 15-28. The advantages of many of these manners of carrying out the method are already clear from the above description in connection with the different embodiments of the lead. However, some further remarks are made below.

As an alternative to the preferred manner according to claim 17, it is also possible to first position the plastic foam material member in the cavity and then apply the gel to this member.

Similarly, in connection with the preferred manner according to claim 21 , it is also possible to first position the enclosure in the cavity and then apply the gel into the enclosure.

BRIEF DESCRIPTION OF THE DRAWINGS Fig 1 shows a schematic side view of a distal portion of a lead according to the prior art

Fig 2 shows a schematic side view of a proximal portion of a lead according to the prior art

Fig 3 shows a sectional view of a distal end portion of a lead according to the prior art

Fig 4 shows a schematic sectional view of an electrode member of a distal end portion of a lead according to an embodiment the present invention.

Fig 5 shows a schematic sectional view of a distal end portion of a lead according to another embodiment the present invention.

Fig 6 shows an end view of the distal end portion shown in Fig 5.

Fig 7 shows a schematic sectional view of a distal end portion of a lead according to a further embodiment the present invention.

Fig 8 shows an end view of the distal end portion shown in Fig 7.

Fig 9 shows a schematic sectional view of a distal end portion of a lead according to a still further embodiment the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Fig 1-3 show different views of a lead according to the prior art. However, the general configuration of the lead according to the present invention can be the same as that of the prior art.

The lead has a proximal end portion (Fig 2) with connecting means 10 designed to be attached to a device, for example to a heart stimulating device. Furthermore, the lead has a distal end portion

(Fig 1 ) comprising an electrode member 12 for emitting and/or sensing electrical signals. The shown lead is bipolar and thus has a further electrode member 14. The lead has an elongated body extending between said proximal end portion and said distal end portion, i.e. the elongated body connects the two parts of the lead shown in Fig 1 and Fig 2.

Fig 3 shows a sectional view of the distal end portion of the lead according to the prior art, i.e. without a cavity of the kind provided in the lead according to the present invention. Fig 3 shows that the electrode member 12 has a first surface portion 16 with a smooth curvature facing the exterior of the distal end portion and a second surface portion 18 facing the interior of the lead. The electrode member 12 may for example be made of titanium nitride. The lead has at least one electric conductor 20 extending between the electrode member 12 and the connecting means 10. The lead also has at least one insulating member 22, for example made of silicon rubber, which encloses the electric conductor 20. The distal end portion of the lead may be provided with tines 24 to facilitate the anchoring of the electrode tip at the body tissue.

Fig 4 shows an electrode member 12 of a distal end portion of a lead according to an embodiment the present invention. The lead is preferably of a dimension such that it is adapted to be insertable via the vascular system into a human or animal heart. The electrode member 12 comprises a cavity 26 that has at least one opening 28 arranged such that the cavity 24 is open to the exterior of the distal end portion of the lead. A drug dispensing member 30 is located in the cavity 26. The drug dispensing member 30 is formed by or at least comprises a gel. The gel may be degradable or non- degradable. As examples of degradable gel materials, the following can be mentioned: PLA (polylactic acid), PGA (polyglycollic acid) and PDS (polydioxanone). Examples of non-degradable gel materials are PEG (polyethylene glycol) and PVP (polyvinylpyrrolidone). The gel may also be formed by a combination of materials. The gel includes a drug, which is adapted to be released into said human or animal body. The drug may be an anti- inflammatory drug, such as a steroid, for example dexamethasone sodium phosphate.

In the shown embodiment, the cavity 26 extends from the first surface portion 16 and does not reach all the way through the electrode member 12, which means that the cavity 26 does not have any opening towards the interior of the lead. However, in an alternative embodiment the cavity 26 may extend all the way through the electrode member 12.

The cavity 26 may have a cross-sectional dimension, which is essentially constant throughout said cavity 26. However, according to the shown embodiment the cavity 26 has a cross-sectional dimension at an intermediate position 32 of said cavity 26 which is smaller than the cross-sectional dimension of the cavity 26 at a position 34 located proximal of said intermediate position 32. An inner portion 36 of the cavity 26 in this way forms a reservoir for holding a relatively large quantity of gel with the drug. Since this inner portion 36 is located at a distance from the opening 28, the drug will only slowly, over a longer time, be released from the inner portion 36 of the cavity 26 to the surrounding body tissue.

Furthermore, in the shown embodiment, the cavity 26 has a cross- sectional dimension at an intermediate position 34 which is smaller than the cross-sectional dimension of the cavity 26 at the first surface portion 16, i.e. at the opening 28. This means that more gel with the drug is located close to the first surface portion 16. Consequently, more drug will be released during the initial time period after implantation of the lead.

The lead of the invention may be produced as follows.

Providing an electrically conductive lead having a proximal end portion designed to be attached to a device, a distal end portion, which comprises at least one electrode member 12 for emitting and/or sensing electrical signals, an elongated body extending between said proximal end portion and said distal end portion. Providing at least one cavity 26 in said distal end portion, which cavity 26 has an opening 28 arranged such that the cavity 26 is open to the exterior of the distal end portion. The cavity 26 can for example be formed before the lead is assembled. The cavity 26 may for example be formed by drilling a hole in the electrode member 12. The method also includes the step of providing a gel that includes the drug, and positioning said gel in said cavity 26. Since the gel is not solidified, the gel, including the drug, may for example be injected into the cavity 26 through a thin hollow member, for example in the form of a needle.

Preferably, the gel maintains its gel-like property even after it has been positioned in the cavity 26. However, it is also within the scope of the invention that the gel becomes solidified after it has been positioned in the cavity 26.

The remaining figures have several features in common with the above described embodiments. These common features will not be described again below.

Fig 5 and 6 show schematic views of a distal end portion of a lead according to another embodiment the present invention. The drug dispensing member 30 here comprises a plastic foam material member 38 in which said gel is provided. The drug dispensing member 30 may include a first part formed by said plastic foam material member 38 in which the gel is provided and a second part 40, which only comprises the gel together with the drug. The second part 40 is provided on top of the first part 38. The drug in this second part 40 will be released quicker after the implantation of the lead into the body than the drug in the first part 38. The plastic foam material may consist of any suitable biocompatible polymeric foam.

The plastic foam material member is prefabricated in a size suited to fit into the cavity 26. Preferably, the gel is provided in said plastic foam material member 38 before the plastic foam material member

38 is positioned in the cavity 26. Alternatively the gel may be injected into the plastic foam material member 38 after the member 38 has been positioned in the cavity 26.

Fig 7 and 8 show a similar view to Fig 5 and 6, respectively, of another embodiment of the invention. According to this embodiment The drug dispensing member 30 comprises an enclosure 42 in which the gel is provided. The enclosure 42 comprises holes 44 through which said drug may be released. The enclosure 42 may be formed by a net structure.

The enclosure may for example be fabricated in a suitable biocompatible polymeric material. The gel may be positioned in the enclosure 42 either before or after the enclosure 42 has been positioned in the cavity 26.

The cavity 26 and said drug dispensing member 30, 38, 42 can be designed such that the drug dispensing member 30, 38, 42 is fixed by a snap-in closure in said cavity 26. This can for example be done in that the cavity 26 is provided with some protruding portions (not shown in the drawings) arranged such that the upper part of the drug dispensing member 30, 38, 42 will snap in below these protruding portions when the drug dispensing member 30, 38, 42 is positioned in the cavity 26.

In the embodiments of Fig 5-8 the cavity 26 is shown to have a substantially constant cross-sectional dimension over the entire length of the cavity 26. However, it is also possible that the cross- sectional dimension may vary also when drug dispensing members 38, 42 of the kind shown in these embodiments are used.

Fig 9 shows an embodiment where the distal end portion of the lead is provided with a helical fixation means 46. A cavity 26 with a drug dispensing member 30 is provided in the distal end portion of the lead. The drug may also in this case constitute a gel with the drug, which gel may be injected into the cavity 26. The opening 28 is preferably located at the end tip of the lead. The opening 28 may preferably be located inside the helix of the fixation means 46. The cavity 26 may also in this case have different possible shapes like those described above in connection with the previous embodiments. Likewise, also in this embodiment different kinds of drug dispensing members 30, 38, 42 may be used.

The invention is not limited to the above described embodiments, but may be varied within the scope of the following claims. F.or example, when the drug dispensing member is formed by a gel without any net enclosure or plastic foam material, a thin membrane or other cover could be applied on top of the gel to prevent the gel from leaving the cavity 26 before the lead has been implanted into the body. The membrane may for example be formed in a material which will be dissolved by the body fluids it comes into contact with once the lead has been implanted into the body.

Preferably the cavity 26 is positioned symmetrically in the distal end portion of the lead, such that the opening 28 is positioned at the end surface of the lead, such as is shown in Fig 4-9. However, it would also be possible that the opening 28 is located at another position, for example at a side surface of the distal end portion. It is also within the scope of the invention that the cavity 26 has more than one opening 28.

Claims

1. An electrically conductive lead suitable to be implanted in a human or animal body, the lead comprising: a proximal end portion designed to be attached to a device, a distal end portion comprising at least one electrode member (12) for emitting and/or sensing electrical signals, an elongated body extending between said proximal end portion and said distal end portion, said distal end portion comprising at least one cavity (26) having an opening (28) arranged such that the cavity (26) is open to the exterior of the distal end portion, a drug dispensing member (30) located in said cavity (26), wherein said drug dispensing member (30) constitutes or comprises a gel that includes a drug, which is adapted to be released into said human or animal body.

2. An electrically conductive lead according to claim 1 , wherein said drug comprises an anti-inflammatory agent.

3. An electrically conductive lead according to claim 1 or 2, wherein said drug dispensing member (30) comprises a plastic foam material member (38) in which said gel is provided.

4. An electrically conductive lead according to claim 3, wherein said drug dispensing member (30) includes a first part (38) formed by said plastic foam material member (38) in which the gel is provided and a second part (40) which comprises said gel but not any substantial amount of said a plastic foam material, wherein said second part (40) is provided on that side of said first part (38) which is facing towards the exterior of said distal end portion.

5. An electrically conductive lead according to claim 1 or 2, wherein said drug dispensing member (30) comprises an enclosure

(42) in which said gel is provided, which enclosure (42) comprises holes (44) through which said drug may be released into said human or animal body.

6. An electrically conductive lead according to claim 5, wherein said enclosure (42) is formed by a net structure.

7. An electrically conductive lead according to any of the preceding claims, wherein said cavity (26) and said drug dispensing member (30, 38, 42) are designed such that the drug dispensing member (30, 38, 42) is fixed by a snap-in closure in said cavity (26).

8. An electrically conductive lead according to any of the preceding claims, wherein said at least one electrode member (12) comprises a first surface portion (16) facing the exterior of the distal end portion of the lead and a second surface portion (18) facing the interior of the lead, wherein said cavity (26) is located such that said opening (28) is located in said first surface portion (16).

9. An electrically conductive lead according to claim 8, wherein said cavity (26) is located such that the cavity (26) does not extend to the second surface portion (18), such that it does not extend all the way through the electrode member (12), wherein the cavity (26) does not have any opening towards the interior of the lead.

10. An electrically conductive lead according to claim 8 or 9, wherein said cavity (26) extends from said first surface portion (16) and has a cross-sectional dimension at an intermediate position (32) of said cavity (26) which is smaller than the cross-sectional dimension of the cavity (26) at a position (34) located proximal of said intermediate position (32).

11. An electrically conductive lead according to any of the claims 8-10, wherein said cavity (26) extends from said first surface portion (16) and has a cross-sectional dimension at an intermediate position (32) of said cavity (26) which is smaller than the cross-sectional dimension of the cavity (26) at said first surface portion (16).

12. An electrically conductive lead according to any of the claims 1-9, wherein said cavity (26) has a cross-sectional dimension, which is essentially constant throughout said cavity (26).

13. An electrically conductive lead according to any of the claims 1-7, comprising helical fixation means (46) at said distal end portion.

14. A method of producing a an electrically conductive lead suitable to be implanted in a human or animal body and comprising a drug to be released into said body, the method comprising: providing an electrically conductive lead having a proximal end portion designed to be attached to a device, a distal end portion, which comprises at least one electrode member (12) for emitting and/or sensing electrical signals, an elongated body extending between said proximal end portion and said distal end portion, wherein said lead is provided with at least one cavity (26) in said distal end portion, which cavity (26) has an opening (28) arranged such that the cavity (26) is open to the exterior of the distal end portion, providing a gel which includes said drug, adapted to be released into said human or animal body, and positioning said gel in said cavity (26).

15. A method according to claim 14, wherein said drug comprises an anti-inflammatory agent.

16. A method according to claim 13 or 14, including the steps of providing a plastic foam material member (38), applying said gel in said plastic foam material member (38), and positioning said plastic foam material member in said cavity (26).

17. A method according to claim 16, wherein said gel is provided in said plastic foam material member (38) before said plastic foam material member is positioned in said cavity (26).

18. A method according to claim 16 or 17, including the step of applying a gel, which includes the drug but not any substantial amount of said plastic foam material, on top of said plastic foam material member (38) after that the plastic foam material member (38) has been positioned in said cavity (26).

19. A method according to claim 14 or 15, including the step of providing an enclosure (42) that comprises holes (44) through which said drug may be released, providing said gel in said enclosure (42) and positioning said enclosure (42) in said cavity.

20. A method according to claim 19, wherein said enclosure (42) is formed by a net structure.

21. A method according to claim 19 or 20, wherein said gel is provided in said enclosure (42) before said enclosure (42) is positioned in said cavity (26).

22. A method according to any of claims 16-21 , wherein said cavity (26) and said plastic foam material member (38) or said enclosure (42) are designed such that said plastic foam material member (38) or said enclosure (42) are fixed by a snap-in closure in said cavity (26).

23. A method according to any of claims 14-22, wherein said at least one electrode member (12) is formed such that it comprises a first surface portion (16) facing the exterior of the distal end portion of the lead and a second surface portion (18) facing the interior of the lead, wherein said cavity (26) is provided such that said opening (28) is located in said first surface portion (16).

24. A method according to claim 23, wherein said cavity is formed such that the cavity (26) does not extend to the second surface portion (18), such that it does not extend all the way through the electrode member (12), wherein the cavity (26) does not have any opening towards the interior of the lead.

25. A method according to claim 23 or 24, wherein said cavity (26) is formed such that it extends from said first surface portion (16) and has a cross-sectional dimension at an intermediate position (32) of said cavity (26) which is smaller than the cross-sectional dimension of the cavity (26) at a position (34) located proximal of said intermediate position (32).

26. A method according to any of claims 23-25, wherein said cavity (26) is formed such that it extends from said first surface portion (16) and has a cross-sectional dimension at an intermediate position (32) of said cavity (26) which is smaller than the cross- sectional dimension of the cavity (26) at said first surface portion (16).

27. A method according to any of claims 14-24, wherein said cavity (26) is formed such that it has a cross-sectional dimension, which is essentially constant throughout said cavity (26).

28. A method according to any of claims 14-22, including the step of providing a helical fixation means (46) at said distal end portion.