DISTAL END DEVICE FOR AN IMPLANTABLE ELECTRICAL CONDUCTOR AND AN ELECTRICAL CONDUCTOR EQUIPPED WITH SUCH AN END DEVICE

Abstract: The invention relates to a device for preventing an anchoring means (26) on the distal end (10) of an implantable electrode cable from coming into contact, during introduction of the latter into a body cavity, with and damaging the cavity wall and to be compressible, while the anchoring means (26) is being screwed into a wall of the body cavity, in order to deliver medication to body tissue. For this purpose, the device is equipped with a body (30) made of a porous, resilient, spongy material, arranged coaxial to the helical anchoring means (26), the distal end of the body (30) projecting beyond the distal end (28) of the anchoring means and being at least partially filled with medication.

Description: Distal end device for an implantable electrical conductor and an electrical conductor equipped with such an end device Field of the invention The present invention relates to a device intended for use on the distal end of an actively implantable electrical conductor to prevent a helical anchoring means, projecting from the distal end of the conductor, from damaging the walls of the cavities during implantation of the conductor into body cavities, such as veins and the heart. The prior art Implantable electrical conductors, i.e. electrode cables, intended for connection at their proximal end to a medical device, such as a pacemaker, and whose distal end is to be affixed in a ventricle or atrium of the heart, can, after intravenous introduction into the heart, be passively or actively affixed to the heart wall in order to deliver electrical impulses to heart muscle, thereby causing it to contract, or sense the heart's intrinsic activity in order to control the pacemaker's operating cycle. In passive fixation of the electrode cable, the distal end is usually equipped with small fins or tines to facilitate anchoring this end in the heart wall without penetrating same. In order to achieve rapid and positive fixation of the distal end of the electrode to the heart wall in implantation of the electrode cable, e.g. when the end of the cable is to have a J shape and press against an atrial wall, active fixation of the cable end to the atrial wall is preferred. For this purpose, the end of the electrode is provided with an anchoring means which can be screwed into wall tissue during implantation. The procedure can be monitored with fluoroscopy to ensure that the cable end is correctly positioned. A commonly used anchoring means for this purpose has a helical means with a pointed tip. Electrode ends of this kind require active screwing of the anchoring means into the heart wall. In instances in which the helical anchoring means can freely rotate on the end of the electrode cable, the helical screw can be rotated with the aid of a stylet inserted from the proximal end of the electrode cable and engage a polygonal recess in the proximal end of the helical means, thereby enabling said means to be rotated and affixed to the heart wall with the end of the electrode pressing against that wall. In order to prevent the pointed end of the helical means from coming into contact with and damaging the walls of veins and the heart during the electrode cable's implantation, the aforementioned freely rotating helical means can be initially retracted into a protective recess at the end of the electrode cable and deployed, with the aid of the stylet, only after the end of the cable has reached the desired fixation site and just before the helical means is screwed in. In another type of anchoring means for active fixation of the end of the electrode to the heart wall, a non-rotating helical means is attached to the distal end of the electrode and projects freely from same. In this instance the helical means must be provided with some kind of protector to keep the tip of the helical means from damaging the wall of veins and the heart during the electrode cable's implantation. The entire electrode cable, including its sheath, must then be rotated in order to drive the helical means into the heart wall. Different solutions have previously been proposed for preventing such fixed, projecting helical means from causing damage during their introduction. For example, US-A-4 876 109 describes a body, covering the helical means, which dissolves in body fluid within a few minutes, whereupon the helical means can be screwed into the heart wall. Another proposal is shown in US-A-3 974 834 in which a compressible, bellows-like sleeve on the distal end of the electrode cable protects the helical means during the electrode cable's intravenous introduction into the heart and is compressed when pressed against the heart wall, enabling the tip of the helical means to gain a footing before being screwed into the heart wall. US-A-5 447 533 shows an active electrode fixation in which a helical means is kept protectively retracted inside a recess in the distal end of the electrode cable to keep the tip of the helical means from damaging the venous wall during the electrode cable's intravenous introduction into the heart. A medication-dispensing means is arranged to slide coaxially inside the helical means, after the helical means has been screwed into the heart wall, towards the heart wall in order to deliver medication to same, e.g. an anti-inflammatory agent. Summary of the invention One object of the present invention is to achieve a simplified end protector, for an anchoring means on the distal end of the electrode cable, which can keep the anchoring means on the distal end of the electrode cable from damaging veins and the heart during introduction as well as deliver medication to the heart wall during and after the anchoring means has been affixed. According to the invention, this is achieved in its broadest and simplest form by a device of the aforementioned kind when a body made of a porous, resilient, spongy material is arranged coaxial to the helical anchoring means and whose distal end projects beyond the distal end of the anchoring means, the body being at least partially filled or impregnated with medication and designed to deliver same to endocardium when the means is pressed against the tissue while the anchoring means is being screwed in. The body can be coaxially arranged inside the helical anchoring means or the latter can be at least partially embedded in the material. The body is preferably made of an elastically deformable material, such as silicone or the like, and can be impregnated with a medication, e.g. an anti-inflammatory agent such as a steroid. In order to reduce the pressure of the elastic, porous body against the heart wall after anchoring, the body's material can also be plastically deformable to some extent. The invention also relates to an implantable electrode cable provided with an end protector according to the above. Additional features and details of the invention will be described in greater detail below, referring to the attached drawing. Description of the drawing FIG. 1 is a sectioned, longitudinal view of a distal end section of an actively affixable electrode cable provided with a combined end protector and medication-dispensing means, according to a first preferred embodiment of the present invention, in a relaxed state; FIG. 2 is an end view of the end section in FIG. 1; FIG. 3 is a view, similar to FIG. 1, of a second embodiment of the present invention; FIG. 4 is an end view of the end section in FIG. 3; and FIG. 5 shows the distal end section in FIGS. 1 and 3 in an actively affixed position in a heart wall. Preferred embodiments FIG. 1 shows a distal end section 10 of en electrode cable, with an external diameter of about 2 mm, intended for active fixation to the wall of a cavity in a patient's heart, according to a first embodiment of the invention. The end section 10 comprises an electrode sleeve 12, which has a distal blind hole 14 to accommodate a fixation part 16 of an anchoring means 18 and a proximal blind hole 20 for receiving a preferably helically wound electrical conductor (not shown) , The sleeve 12 and the conductor are surrounded by an insulating outer sheath 22. The anchoring means 18 also has a fixation part 26, which axially projects about 1.5 mm from the sleeve's 12 distal electrode end 24, with a helical shape and pointed tip 28 and a diameter of about 0.25 mm. To keep the tip 28 of the fixation part 26 of the anchoring means 18 from damaging the walls of the vein and heart during intravenous introduction of such an electrode cable, intended for active fixation to the wall of a heart, the fixation part 26 is equipped with a body 30, which projects axially beyond the tip end 28 so this end does not come into hazardous contact with vascular walls. According to the invention, the body 30 is made of a porous, resilient, spongy material which both protects the tip section 28 during introduction of the electrode cable and makes possible local delivery of medication during and after the fixation part 26 is screwed into the heart wall. The body's 30 material must accordingly be stiff enough to resist the small pressure loading sustained by the body 30 when it impacts with vascular walls during its introductory phase while still being sufficiently resilient and elastic to compress between the heart wall and the distal end of the electrode cable while the fixation part 26 is being screwed into endocardium, as shown in FIG. 5. The helical fixation part 26 can have an outer diameter of about 2.35 mm and an inner diameter of about 1.85 mm. The body 30 can be held in place by friction against the interior of the anchoring means, and its proximal end could possibly be mounted on the distal end 24 of the electrode sleeve 12 with some adhesive means. As shown in FIG. 2, the tip 28 is beveled radially inward so it points in towards the spongy body 30. The material of the body 30 must also be so porous or spongy that it is capable of impregnation with an appropriate medication for the intended purpose, e.g. an anti-inflammatory agent such as a steroid or some other therapeutic drug. Silicone is an example of material of the aforementioned kind which meets these specifications and is also biocompatible. Elastic polymer materials, such as Gore-Tex , could also be used. Such porous, elastic materials can be compressed to about 5-10% of their original thickness. It is not necessary to fill the entire body 30 with medication. In most instances, only part of the body needs to hold medication e.g. the outermost, distal end section. The amount of medication can be about 1 mg. FIGS. 3 and 4 show a second embodiment of the distal end section of an electrode cable according to the invention. In this embodiment, the fixation part 26 of the anchoring means 18 which projects from the distal end surface 24 is embedded in the porous, spongy body 30' whose external diameter is accordingly equal to or larger than the external diameter of the fixation part 26. After fixation, the body 30' acquires a shape like the one shown in FIG. 5. It would be advantageous if the material were devised in a way enabling it to be plastically deformed, at least in part, i.e. so it does not strive to completely resume its original shape after being deformed by compression. Pressure exerted by the elastic material on the heart wall after the body has been compressed could accordingly be reduced, as shown in FIG. 5.

Claims: Patent claims 1. A device designed to be arranged on the distal end (10) of an actively implantable electrical conductor to prevent a helical anchoring means (26) , projecting from the distal end of the conductor, from damaging wall parts of the cavities during introduction of the conductor into body cavities, such as veins and the heart, characterized in that a body (30; 30'), made of porous, resilient, spongy material, is arranged coaxial to the helical anchoring means (26) , and its distal end projects beyond the distal end (28) of the anchoring means, the body (30; 30') being filled at least in part with medication and devised to deliver this medication to body tissue when the body is compressed against the tissue when the anchoring means (18) is screwed in. 2. A device according to claim 1, characterized in that the body (30) is coaxially arranged inside the helical anchoring means (26) . 3. A device according to claim 1, characterized in that the anchoring means (26) is at least partially embedded in the body (30) . 4. A device according to any of claims 1-3, characterized in that the body (30; 30') is made of an elastically deformable material such as silicone. 5. A device according to claim 4, characterized in that the body (30; 30') is plastically deformable, at least in part. 6. A device according to claims 4 or 5, characterized in that the body (30; 30') is compressible to 5-10% of its original thickness. 7. A device according to any of claims 1-6, characterized in that the body (30; 30') is impregnated - at least in its distal end section - with anti-inflammatory medication, such as a steroid. 8. An implantable electrode cable with a proximal end, intended for connection to a heart stimulator, and a distal end (10) , intended for active anchoring in endocardium, comprising a helical anchoring means (26) , projecting from the distal end (10) of the electrode cable, for active fixation of the electrode cable in a wall of the heart, characterized in that a body (30) , made of a porous, resilient, spongy material filled at least in part with a dispensable heart medication, is mounted in the helical anchoring means (26) , said body (30) having a distal end section, which projects beyond the free distal end (28) of the anchoring means (26) so as to keep the anchoring means from damaging the walls of veins and heart during introduction of the electrode cable into same, the body (30) further being arranged to be compressed, when the anchoring means (18) is screwed into heart wall, and deliver its medication to same. An implantable electrode cable with a proximal end, intended for connection to a heart stimulator, and a distal end (10) , intended for active anchoring in endocardium, comprising a helical anchoring means (26) , projecting from the distal end (10) of the electrode cable, for active fixation of the electrode cable in a wall of the heart, characterized in that the helical anchoring means (26) is at least partially embedded in a body (30) , made of a porous, resilient, spongy material, at least partially filled with a releasable heart medication, said body (30) having a distal end section which projects beyond the free distal end (28) of the anchoring means (26) so as to keep the anchoring means, during introduction of the electrode cable into veins and the heart, from damaging the walls of same, the body (30) further being arranged to be compressed, when the anchoring means (18) is screwed into the heart wall, and deliver its medication to same.

Inventors: LINDEGREN ULF, NEUBAUER HEINZ, LINDEGREN, ULF, NEUBAUER, HEINZ
Applicants: LINDEGREN ULF, NEUBAUER HEINZ, PACESETTER AB, LINDEGREN, ULF, NEUBAUER, HEINZ
Application year: 1997
Main classification: A61N1
IPC codes: A61N1