METHOD FOR MANUFACTURING AN ACTIVE FIXATION ELECTRODE
The present invention relates to methods for manufacturing active fixation helices for the stimulation and/or sensing of organs. A first embodiment of a method in accordance with the present invention for making a helix comprises a first step of producing an elongated helix precursor body comprising one or more electrical conductors surrounded by an insulating material. This helix precursor body is then shaped into a helix, material removed in predetermined places in order to expose the areas of the conductors which will be used as electrodes in the final product. The body is coated with an electrically conducting biocompatible coating which is subsequently partly removed in continuous loops from around the electrodes in order to electrically insulate them from each other and to ensure that the electrically active areas of the electrodes are of the correct dimensions.
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This application is a division of U.S. patent application Ser. No. 12/522,001, filed Jul. 2, 2009, which claims priority from International App. No. PCT/SE2007/000084, filed Jan. 31, 2007.
FIELD OF THE INVENTIONThe present invention relates to methods for manufacturing active fixation electrodes for electrical medical leads, in particularly helix electrodes intended to be screwed into body tissue.
BACKGROUND OF THE INVENTIONImplantable medical electrical stimulation and/or sensing leads (also called “leads” or “electrode leads”) are well known in the fields of tissue and organ stimulation and monitoring. Such fields include cardiac pacing. Leads may be attached to an organ by an active fixation means which is designed to penetrate the surface of the organ that is to be stimulated or sensed. A common active fixation means employs a helix which has a sharpened tip and is mounted at the end of the electrode lead. The fixation helix typically has an outside helix diameter which is slightly less than that of the lead body and extends in axial alignment with the lead body. The sharpened tip of the helix can be screwed into the organ by being rotated. Typically the helix is electrically connected to one or more conductors in the electrode lead. These conductors can be electrically connected to one or more exposed surfaces of the helix which then can be used as stimulating and/or sensing electrodes. A fixation helix therefore may contain one or a plurality of conductors. Typically the outer surface of the helix, including the exposed surfaces used as electrodes, is partly covered with a biocompatible coating to minimise interference with the tissue to which it is to be attached. Typically the biocompatible coating is electrically conducting and it is arranged in a predetermined pattern with continuous gaps on the insulating material around the exposed electrode surfaces in order to prevent the different electrodes from being in electrical contact with each other. The sizes of the surface areas of the exposed electrodes are set at levels which are compatible with the organ they are attached to. US Patent Application US 2006/0122682 describes an active fixation helix for an electrical medical leads and methods of making such active fixation helixes.
SUMMARY OF THE INVENTIONThe present invention relates methods for manufacturing active helices suitable for use as active fixation electrodes for electrical medical leads, in particularly helix electrodes intended to be screwed into body tissue. Such helices are made of thin electrical conductors, encased in an insulating material—usually treated to be biocompatible, and twisted into the shape of a helix. The portions of the conductors are exposed to form electrically active surfaces which can be used for stimulating or sensing.
A first embodiment of a method in accordance with the present invention for making a helix comprises a first step of producing an elongated helix precursor body comprising one or more electrical conductors surround by an insulating material. This helix precursor body is then shaped into a helix, material removed in predetermined places in order to expose the areas of the conductors which will be used as electrodes in the final product and coated with an electrically conducting biocompatible coating which is subsequently partly removed in continuous loops from around the electrodes in order to electrically insulate them from each other and to ensure that the electrically active areas of the electrodes are of the correct dimensions.
An alternative embodiment of a method in accordance with the present invention for making a helix comprises a first step of producing an elongated helix precursor body comprising one of more electrical conductors surrounded by an insulating material. Material is then removed at predetermined places from the helix precursor body in order to expose the areas of the conductors which will be used as electrodes in the final product. The body is coated with an electrically conducting biocompatible coating which is then removed in continuous loops from around the electrodes in order to electrically insulate them from each other and to ensure that the electrically active areas of the electrodes are of the correct dimensions. The body is then formed in to the shape of a helix.
While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. As will be realized, the invention is capable of modifications in various aspects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.
A first embodiment of a method for producing an active fixation means in the form of a multi-conductor electrically active helix will now be described in connection with
An example of such a helix body precursor 51 is shown in
In the next step of the method a predetermined length of second core 39 and the insulating material surrounding it are removed from distal end 55, leaving a shoulder 58 in the helix body precursor 51, said shoulder extending over a portion of the first core 37 which is still surrounded by insulating material 42 as shown in
In a third step, as shown in
Subsequently, as shown in
Finally, as shown in
Subsequently, as shown in
Finally, as shown in
In a second embodiment of a method for producing an active fixation means in the form of an electrically active helix, the helix body precursor is formed into a helical shape before the surfaces of the conducting core or cores are exposed. Thus this method is similar to the first embodiment of the invention except that the forming of the helix is performed before the application of coatings. In more detail an example of a second embodiment of the present invention comprises the steps of:
a) forming a helix body having a proximal end and a distal end connected by a plurality of helical revolutions, said body comprising at least one electrically conducting core partially surrounded by an insulating sheath whereby a continuous portion of the surface of each electrically conducting core extending from said distal end towards said proximal end and facing in a predetermined direction is exposed;
b) applying a continuous electrically conducting, biocompatible coating to surface of said insulating sheath and each exposed surface of each electrically conducting core;
c) removing a portion of said electrically conducting biocompatible coating on the insulating sheath surrounding each continuous portion of the surface of each electrically conducting core such that the electrically conducting coating on the exposed surface of each electrically conducting core is not in electrical contact with the remaining electrically conducting coating on said insulating sheath.
In the above examples, the exposed surfaces 43-45′″ and 45-45″′ which are to act as sensing or stimulating electrodes are quadratic when seen from a view perpendicular to the exposed surface and extend longitudinally, but it conceivable for them to made in any shape.
There are several possible ways of forming an elongated helix body precursor. For example, as shown in
Such an elongated helix body precursor can be formed into a helix 89 as shown in
The above suggested cross-sections are merely examples of conceivable cross-sections—the skilled person would understand that in the event that a lead, precursor body or helix has a plurality of conductors it is always possible to remove selectively insulating material in predetermined positions so that when in use in a patient conductors can come into contact with tissue and thereby be used as a stimulating and/or sensing electrode.
Claims
1. A method of fabricating an electrically active helix for an electrical medical lead comprising:
- a) forming a helix body having a proximal end and a distal end connected by a plurality of helical revolutions, the helix body comprising at least one electrically conducting core partially surrounded by an insulating sheath, wherein a portion of a surface of each electrically conducting core extending from the distal end towards the proximal end and facing in a predetermined direction is exposed;
- b) applying a continuous electrically conducting, biocompatible coating to a surface of the insulating sheath and each exposed surface of each electrically conducting core; and
- c) removing a portion of the electrically conducting biocompatible coating on the insulating sheath surrounding each continuous portion of the surface of each electrically conducting core such that the electrically conducting coating on the exposed surface of each electrically conducting core is not in electrical contact with the remaining electrically conducting coating on the insulating sheath.
2. The method of claim 1, wherein step a) comprises:
- i) forming an elongated helix body precursor having a proximal end and a distal end, the helix body precursor comprising at least one electrically conducting core and a surrounding insulating sheath in which there is at least one longitudinally extending slit in the insulating sheath which exposes a portion of each electrically conducting core; and
- ii) forming the elongated helix body precursor in a helix body in which a plurality of helical revolutions are formed between the proximal end and the distal end of the helix body precursor, and wherein the exposed surface of each electrically conducting core faces in a predetermined direction.
3. The method of claim 2, wherein step i) comprises the step of forming at least one electrically conducting core surrounded by an insulating sheath which leaves at least one portion of each electrically conducting core exposed.
4. The method of claim 2 wherein, in step c) the removal of the portion of electrically conducting biocompatible coating is achieved by polishing or cutting or grinding or a combination thereof.
5. The method of claim 1, wherein the biocompatible coating is TiN or TiSiC or platinum black or a metal oxide or other electrically conducting material.
Type: Application
Filed: Jul 13, 2012
Publication Date: Jun 20, 2013
Applicant: ST. JUDE MEDICAL AB (Jarfalla)
Inventors: Anna Norlin Weissenrieder (Lidingo), Rolf Hill (Jarfalla), Olof Stegfeldt (Alta), Marie Herstedt (Uppsala), Mikael Forslund (Bromma), Susanne Nilsson (Huddinge)
Application Number: 13/549,087
International Classification: H01B 13/00 (20060101);