Arrangement for delivering medications in an implantable medical device
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed to an arrangement for delivering medication in an implantable medical device. 
     2. Description of the Prior Art 
     A heart pacemaker electrode is described in U.S. Pat. No. 4,577,642 having components therein for delivering medication to tissue surrounding the electrode. At its distal end, the electrode has an electrode head with an internal cavity therein filled with medication. The cavity has an open end covered by an electrode tip consisting of sintered material, through which the medication can migrate to the surface of the electrode tip for delivery to tissue in contact therewith. The medication is intended to prevent the formation of both thromboses and inflammations in the region of the electrode head. In the heart pacemaker electrode of this type, the medication is not distributed over the surface in a controllable fashion, and only one type of medication can be delivered at a time. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an arrangement for delivering medications in an implantable medical device which permits the medication to be delivered in a controllable fashion in defined tissue regions. 
     It is a further object of the present invention to provide such an arrangement which permits more than one medication to be delivered at a time. 
     The above object is achieved in accordance with the principles of the present invention in an implantable medical device having at least two containers for storing medication, each of the containers being in communication with at least one opening in a surface of the device having the size of a pore. An arbitrary number of containers or receptacles, which can contain respectively different medications, can be arranged at defined surface regions of the device. In one embodiment, the containers form slight depressions in the surface region of the device at which the containers are disposed, which permit tissue ingrowth. 
     The structure disclosed herein is particularly suitable for use in heart pacemaker systems. The arrangement may be disposed at one or more selected surface regions of the heart pacemaker system. The arrangement may be disposed, for example, in a heart pacemaker electrode, wherein the containers can be arranged both in the electrode head and at tissue-fastening structures such as collars or bristles attached in the region of the electrode head. The containers can be filled with different medications such as, for example, cortisone and/or penicillin. Other portions of the heart pacemaker system such as the electrode ring (if a bipolar electrode is used) a fastening clamp for anchoring the electrode at a vein, and the connector portion of the heart pacemaker housing may also be provided with containers filled with medication. 
     In a further embodiment of the invention, the containers have respective longitudinal axes which reside at respectively different angles with the surface region of the implanted device. The angle at which tissue ingrowth occurs in each container can thus be defined. 
     In a further embodiment of the invention, the containers are conical, tapering to a smallest portion in communication with the surrounding tissue via the pore-sized hole in the surface of the implanted device. This form of container can be manufactured in a relatively simple manner by a laser beam. 
     In another embodiment of the invention, the containers consist of at least two intersecting blind holes. A relatively large container having at least two openings, each having the size of a pore in the surface of the implanted device, is thereby achieved. Tissue growing into the containers can meet at the intersecting interior of the container through these openings. A reliable anchoring of the portion of the implanted device at which such intersecting containers are disposed is thereby established. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a heart pacemaker system employing a medication delivery arrangement constructed in accordance with the principles of the present invention. 
     FIG. 2 is an enlarged side view, partly in section, of an electrode head embodying a medication delivery arrangement constructed in accordance with the principles of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 1, an implanted medical device such as a heart pacemaker system includes a pacemaker housing 1 having a connector 2 for an electrode 3 which has a distal end provided with an electrode head 4 and tissue-fastening structure 8. The electrode 3 may be anchored at a vein 6 of a patient with a fastening clamp 5, and may be provided with a ring electrode 7 to form a bipolar electrode. The different components of the heart pacemaker system are respectively provided with medication delivery structure 9, 10, 11, 12, 13 and 14. The pacemaker housing 1 may be provided with a plastic coating or covering 22 in which the medication delivery structure 10 is disposed. The connector 9 may also include such medication delivery structure 9. The medication delivery structures 9 and 10 can delivery medications which prevent inflammation which may arise around the implanted pacemaker. 
     The fastening clamp 5 may also deliver anti-inflammation medication with a medication delivery structure 11. The ring electrode 7 may be provided with a medication delivery structure 12 for delivering a mediation against thrombosis which may otherwise form in the region of the ring electrode 7. 
     FIG. 2 shows the electrode head 4 with tissue-fastening structure 8 thereon, provided with respective medication delivery structure 13 and 14. The structure 13 and 14 consists of conically fashioned containers or receptacles 15 and 18, each of which is in communication with an opening 16 having the size of a pore in the surface region 17 of the electrode head 4, or the surface region of the fastening structure 8. The containers 15 and 18 can be disposed arbitrarily close to each other, and in different regions may contain different medications. Thus, for example, the container 15 may hold medication for preventing thromboses from arising, and the container 18 may be filled with a medication for preventing inflammation. 
     FIG. 2 also shows a further embodiment wherein containers 19 are provided consisting of two intersecting blind holes 20 and 21. Such containers 19 are relatively large and thus hold more medication. The medication emerging from the openings spread in the tissue region of the heart pacemaker system at which the respective structure 9 through 14 is disposed. 
     Each of the containers 15, 18 and 19 form slight depressions in the relevant region which permit tissue ingrowth, so as to anchor certain portions of the implanted device. For this purpose, the respective longitudinal axes 23, 24 and 25 of the containers 15, 18 and 19 are disposed at respectively different angles with respect to the surface of the implanted device, so that the angle at which tissue ingrowth occurs can be prescribed. The containers 19 formed by the intersecting blind holes have an advantageous shape for anchoring a portion of the implanted device, because the tissue meets in the interior of such a container 19, coming from the respective openings, and con grow together. 
     Although the arrangement has been described above in connection with a heart pacemaker system, the structure disclosed herein can be used in any type of implantable medical device wherein delivery of medication is desired. 
     Although modifications and changes may be suggested by those skilled in the art it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.