Abstract:
An electrode head of an implantable electrode line, including an elongate housing which has a longitudinal axis and includes at least two housing parts, which are cylinder-segment-shaped at least in portions and are fixedly joined together.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application is a continuation-in-part of co-pending U.S. patent application Ser. No. 14/520,859, filed Oct. 22, 2014, which claims the benefit of U.S. Provisional Patent Application No. 61/910,442, filed on Dec. 2, 2013, the entire disclosures of which are hereby incorporated by reference in their entireties. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to an electrode head of an implantable electrode line, comprising a head housing. The present invention also relates to an electrode line. 
       BACKGROUND 
       [0003]    Implantable electrode lines and respective electrode heads are a component of various electronic medical arrangements, specifically of cardiac pacemaker systems and implantable defibrillator systems, but also of arrangements for nerve or brain stimulation and also of arrangements for detecting action potentials and other electrical signals from a patient&#39;s body, for example, and are essential to the function of said arrangements. The reliable functioning of said arrangements, which in any case should also be safe for the patient, is therefore an indispensable prerequisite for their clinical use. Aspects such as sterilizability, easy handling and reasonable costs also play a key role in the development and the use of electrode lines and electrode heads. 
         [0004]    For many applications, many electrode lines have to be designed such that their distal end can be securely fixed at the destination to, or in, a hollow organ (for example, the heart) or vessel of the patient. To meet this requirement, under consideration of the above-mentioned general requirements of electrode lines, comprehensive development efforts have been made over decades and a wide range of technical solutions proposed. 
         [0005]    Among these, what are known as “screw heads” have achieved particular significance in practice, in which a helical coil is housed in the electrode head and, when the electrode line is implanted at the destination, is rotated out from the electrode head in a distal direction by the surgeon, and in doing so is simultaneously screwed into the tissue portion of the patient against which the electrode head abuts distally. Known screw heads consist of a plurality of interconnected cylindrical sleeves, usually made of a metal compatible with the body, and occasionally made of thermoplastics, such as PU (polyurethane) or PEEK (polyetheretherketone). 
         [0006]    The present invention is directed toward overcoming one or more of the above-mentioned problems. 
       SUMMARY 
       [0007]    With the present invention, an electrode head is provided which has the features of independent claim  1 . Furthermore, an electrode line comprising an electrode head of this type is proposed. Expedient developments of the concept forming the basis of the present invention are disclosed in the dependent claims. 
         [0008]    The present invention proceeds from the consideration of developing an electrode head (in particular, a screw head) which consists of few individual parts, which are also economical. The mechanism is to be designed here such that a fixing mechanism, in particular, (specifically a screw) can be produced in suitable geometric configuration and easily in terms of technology. The stringing together of individual parts produced by injection molding or machining, as is currently practiced, always leads to a large cumulative tolerance. 
         [0009]    A key aspect of the solution according to the present invention lies in dividing the housing length-wise. Two cylinder-segment-shaped housing parts (individual shells) are thus produced and are shaped in such a way that all stops, centering means and advancing elements are formed by the tool. Due to the tool technology, it is ensured that there are no significant deviations in terms of dimension. Once the inner module has been inserted, the individual shells have to be fixedly interconnected. 
         [0010]    The manufacturing aspect that all stops, centering means and advancing elements are formed by the tool together with the individual shells has the significant advantage that the parts can also be manufactured in large quantities and with maximum repeat accuracy. A further great advantage of this solution is that these elements are always arranged at the same distance from one another because these dimensions are predefined by the injection mold. The edge of the individual shells is designed here such that the shells are centered both in the longitudinal direction and in the transverse direction. 
         [0011]    Insofar as reference is made here to the fact that the head housing comprises cylinder-segment-shaped housing parts, at least in portions, this is to include expressly housing parts of which the basic shape is that of a cylinder segment, but which on their inner and/or outer surface have molded or shaped portions which on the whole produce an inner or outer shape deviating from the cylinder-segment-shape. The distal end of the electrode head may additionally be conical or spherical or otherwise tapered, and in this respect may likewise deviate from a cylinder shape. In principle, such housing parts that have no dividing plane parallel to the longitudinal axis of the head housing, but a dividing plane inclined relative to the longitudinal axis or, for example, also a dividing plane that is turned in a spiraled manner, are also to be considered as belonging to the present invention. 
         [0012]    An embodiment that is presently preferred, however, is that in which the head housing is joined from two shell parts having a semi-cylindrical outer contour and a dividing plane parallel to the longitudinal axis. 
         [0013]    Furthermore, the housing parts, in particular, the semi-cylindrical shell parts, of the head housing are expediently welded or adhesively bonded together. 
         [0014]    In a further embodiment, in particular, some of the housing parts are metal shaped parts, and in particular, metal stamped parts, formed from thin-walled sheet metal. In a further embodiment, in particular, some of the housing parts are plastic parts, and specifically injection molded parts. A head housing formed from a combination of metal and plastic parts also lies within the scope of the present invention. 
         [0015]    In a further embodiment, the electrode head comprises a ring seal and/or an X-ray contrast ring, which, in one embodiment, is/are received in at least one second chamber of the electrode head, which is arranged proximally in relation to the first chamber. The X-ray contrast ring, which is made of metal, may simultaneously serve as a peripheral and closed sealing face for the seal between the shaft and housing. 
         [0016]    In a further embodiment, the housing parts have a stepped outer diameter, in particular, in a proximal portion an outer diameter smaller than in a portion arranged distally in relation hereto. Specifically, this also includes embodiments with a lateral dimension stepped a number of times, for example, with a drug storage region in a portion of the outer surface. Specifically, the drug storage region is annular in this case, and the outer surfaces of the housing parts joined together have a return corresponding to the dimensions of the annular drug storage region. 
         [0017]    In a further embodiment, the electrode head has a plurality of chambers which are delimited by transverse wall pieces and which have a central aperture. In an expedient embodiment of a screw electrode head, three delimited chambers are provided, each of which receives at least one essential functional element of the screw electrode. However, more or less chambers are also contemplated. The inner module, in the normal case consisting of a fixing screw, stop sleeves, shaft, seal and coil, can be completely pre-assembled. Necessary stops on the shaft are visible and could be fixed in position relative to one another with maximum accuracy. The X-ray ring is then fitted on this module. The module thus completed is then inserted into the lower shell, the upper shell is fitted, and both half-shells are then interconnected. 
         [0018]    In an embodiment of the proposed electrode line, the electrode head is joined by means of at least one connection tube piece to the electrode line body. 
         [0019]    In a further embodiment of the proposed electrode line, the electrode head is joined by means of at least one resilient connection tube piece to the electrode line body. 
         [0020]    In further embodiments of particular practical significance, the electrode line comprises an active fixing element, which, in particular, is received in a distally arranged first chamber of the electrode head. Specifically, the fixing element is formed as a rotatable and displaceable helical coil. Alternatively, however, it may also be formed as displaceable claws that can be splayed apart, movable fins or other fixing elements known per se, of which the implementation is compatible with the proposed design of the head housing and requires the provision of an actuation element or force transmission element (for example, a helical coil actuation shaft) within the line body of the electrode line. 
         [0021]    Further features, aspects, objects, advantages, and possible applications of the present invention will become apparent from a study of the exemplary embodiments and examples described below, in combination with the Figures, and the appended claims. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0022]    Advantages and expedient features of the present invention will also emerge from the following description of an exemplary embodiment(s) with reference to the drawings, in which: 
           [0023]      FIG. 1  shows a perspective external view of an electrode head according to an embodiment of the invention; 
           [0024]      FIGS. 2A-2B  show, respectively, a perspective view of the internal design ( FIG. 2A ) and of the inner wall of a half-shell of the electrode head from  FIG. 1 ; and 
           [0025]      FIG. 3  shows a longitudinal section of the design of an electrode line provided with the electrode head according to  FIGS. 1-2B  (distal part). 
           [0026]      FIGS. 4A  (closed shell) and  4 B (open shell) show perspective illustrations of an alternate screw electrode head according to an additional embodiment of the present invention. 
           [0027]      FIG. 5  shows a cross-section view of the alternate screw electrode head shown in  FIG. 4A . 
           [0028]      FIG. 6  shows an interior view of the shell part of the alternate screw electrode head shown in  FIG. 4B . 
           [0029]      FIG. 7  shows a cross-sectional view of the alternate screw electrode head according to  FIG. 5 , with the shell part removed. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]      FIG. 1  shows a perspective illustration of a screw electrode head  1 , which has a basic cylindrical shape, of an implantable pacemaker electrode line (see  FIG. 3 ), of which the construction is shown in greater detail in  FIGS. 2A-2B . At the distal end, the electrode head  1  has a rounded flange portion  1   a  of a first diameter, which is adjoined (in this order) by a first longer cylinder portion  1   b  of smaller diameter, a second longer cylinder portion  1   c  of larger diameter (which can be bigger, smaller or equal to the first diameter), and lastly a third longer cylinder portion  1   d,  again of reduced diameter again and also below the diameter of the first cylinder portion  1   b.  In addition, it can be seen that the electrode head  1  has an open distal end  1   e,  in which the distal end of a helical coil  3  can be seen. Furthermore, a continuous weld seam  1   f  can be seen and fixedly interconnects prefabricated half-shells  1 . 1  and  1 . 2  (not denoted separately here) of the electrode head  1  in an integrally bonded manner. 
         [0031]      FIG. 2A  shows the inner design of the electrode head  1 , together with the first half-shell  1 . 1  of the head housing, and  FIG. 2B  shows the second half-shell  1 . 2  of the head housing, in each case again in a perspective illustration. For the sake of improved clarity, the above-referenced portions  1   a  to  1   e  of the outer contour of the head housing are not denoted again in  FIGS. 2A-2B . It can be seen, however, that both half-shells  1 . 1 ,  1 . 2  have a division (naturally likewise in a half-shell-like manner) into three chamber segments  1 . 1 A,  1 . 1 B and  1 . 1 C and  1 . 2 A,  1 . 2 B and  1 . 2 C, respectively, adjoining one another in the longitudinal direction. The mentioned chamber segments are separated from one another by partition walls shaped primarily in the form of segments of a circle and having a central aperture, of which merely the more distal partition wall  1 . 1 D of the first half-shell  1 . 1  can be seen in  FIG. 2A , although both partition walls  1 . 2 D and  1 . 2 E can be seen in  FIG. 2B . 
         [0032]    When comparing the two drawings, it can be easily seen that the half-shells  1 . 1 ,  1 . 2  are not identical, but have different projections and returns or stops and centering means, both in the region of the distal flange and of two of the three stepped cylindrical regions and lastly also in the region of the partition walls. Inter alia, it is thus ensured that there are overlap regions of sufficient size in the wall of the head housing between the first and second half-shell so as to ensure high mechanical stability and tightness of the rear region of the head housing. 
         [0033]    It can be seen from  FIG. 2A  how the helical coil  3  fills the distal chamber  1 A of the electrode head  1  in the retracted state in its entire length and surrounds, via its proximal end, a ram  5   a  of a fixing screw actuation shaft  5 , to which it is fastened (not visible here) in an integrally bonded manner (for example, by means of welding). In the second chamber  1 B, the fixing screw actuation shaft  5  is surrounded by a ring seal  7  and an X-ray contrast ring  9  in such a way that the periphery of the chamber  1 B is largely filled. In the third chamber  1 C, a contact sleeve  11  for electrically contacting the conductor coil (not shown here) of the electrode line body with the ram  5 a or the helical coil  3  can be seen. 
         [0034]      FIG. 3  shows a longitudinal sectional illustration of the distal end region of an electrode line  10  provided with the electrode head  1  according to  FIGS. 1-2B . Besides the electrode head  1 , of which the outer shape and design are shown in  FIGS. 1-2B  and are described further above, the electrode line  10  comprises an outer line body (not shown here) or outer tube, an outer conductor coil (likewise not illustrated here) for contacting a ring electrode  13 , and an inner conductor coil  17  arranged within an inner tube  15 . The fixing screw actuation shaft  5 , already mentioned above, is in turn placed in the interior of said coil, and the contact sleeve  11 , likewise already mentioned further above, is attached to the end of said shaft. 
         [0035]    The mechanical connection and simultaneous seal between the electrode head  1  and the line body of the line  10  distally in relation to the ring electrode  13  is produced by an inner PTFE (polyetrafluoroethylene—Teflon) tube  19 . 1  and a substantially likewise tubular outer silicone connection piece  19 . 2 . Whereas the PTFE tube  19 . 1  is arranged within the proximal chamber  1 C of the electrode head  1  and extends beyond a distal region of the inner conductor coil  17 , the silicone connection piece  19 . 2  surrounds a distal end portion of the ring electrode  13  as well as the outer wall of the proximal chamber  1 C (or, on the basis of the external view, the proximal cylinder portion  1   d ) of the electrode head  1  and interconnects these. Suitably shaped fixing ring portions, or locking portions, in the inner wall of the silicone connection piece  19 . 2  or the outer wall of the PTFE tube  19 . 1 , and optionally additional fixing rings or other fixing means, contribute to secure fixing of the interconnected parts in the longitudinal direction of the electrode line in a manner known per se. 
         [0036]    Specific attention should be paid in  FIG. 3  to the complete illustration of the ring seal  7 , of which only a distal end-face portion can be seen in  FIG. 2A . It can be seen that the outer contour of the ring seal  7  is stepped or chamfered a number of times. Furthermore, a hollow-cylindrical drug storage region  21  is illustrated here in the region of the distal cylinder portion  1 B of the electrode head  1  and (again in a manner known per se) serves to store and continuously dispense, in an ongoing manner, an anti-inflammatory steroid when the electrode line is implanted. When the half-shells are already fixedly connected to the cylindrical electrode head  1 , the drug store in the form of a hollow cylinder  21  is slid over and fastened in the distal region. 
         [0037]    In the shown embodiment, the electrode head  1  is preferably manufactured from PEEK half-shells, however PU half-shells or housing parts formed from another polymer that can be used in implanted parts can also be manufactured alternatively. In principle, the manufacture from a biocompatible metal, such as, for example, titanium or a titanium alloy or high-grade steel, is also considered, wherein special design provisions have to be made, however, in order to ensure the radiopacity of the length by which the helical coil is screwed out, and specific spring ranges, which are not provided in the above-described embodiment, would possibly have to be provided. 
         [0038]    The embodiment of the present invention is not limited to the above-described examples and high-lighted aspects, but the present invention can also be implemented in a large number of modifications within the capabilities of a person skilled in the art. 
         [0039]      FIGS. 4A  (closed shell) and  4 B (open shell) show a perspective illustration of an alternative screw electrode head  101 , which has a basic cylindrical shape of an implantable pacemaker electrode line, of which the construction is shown in greater detail in  FIGS. 5-6 . At the distal end, the electrode head  101  has a rounded flange portion  101   a  of a first diameter, which is adjoined (in this order) by a first longer cylinder portion  101   b  of smaller diameter, a second longer cylinder portion  101   c  of larger diameter (which can be bigger, smaller or equal to the first diameter), and lastly a third longer cylinder portion  101   d,  again of reduced diameter and also below the diameter of the first cylinder portion  101   a.  The second longer cylinder portion  101   c  of larger diameter can consist of three cylinder portions  101   c ′,  101   c ″ and  101   c ′″, where the diameter of the cylinder portions  101   c ′ and  101   c ′″ is smaller or equal compared to the diameter of the cylinder portion  101   c ″, but the diameter of the cylinder portion  101   c ′ is bigger than the diameter of the rounded flange portion  101   a  and also bigger than the diameter of the cylinder portion  101   b.  The diameter of the cylinder portion  101   c ′″ is bigger than the diameter of the cylinder portion  101   d.  In addition, it can be seen that the electrode head  101  has an open distal end  101   e,  in which the distal end of a helical coil  3  can be seen. Furthermore, a continuous interface  101   f,  i.e., a weld seam or groove, can be seen where the prefabricated first shell part  101 . 1  and the second shell part  101 . 2  of the electrode head  101  are put together. 
         [0040]      FIG. 5  shows the inner design of the electrode head  101 , together with the first shell part  101 . 1  and the second shell part  101 . 2  of the head housing, and  FIG. 6  shows the second shell part  101 . 2  of the head housing, in each case again in a perspective illustration. For the sake of improved clarity, the above-referenced portions  101   a  to  101   e  of the outer contour of the head housing are not denoted again in  FIGS. 5-6 . It can be seen in  FIG. 5 , however, that the housing of the head  101 , formed out of the shell parts  101 . 1 ,  101 . 2 , has a division (naturally likewise in a half-shell-like manner) into three chamber segments  101 A,  101 B and  101 C, adjoining one another in the longitudinal direction. The mentioned chamber segments are separated from one another by partition walls shaped primarily in the form of segments of a circle or a ring and having at least a central aperture, of which both partition walls  101 D and  101 E can be seen in  FIG. 5 . In  FIG. 6 , merely the more distal partition wall  101 D can be seen, because it is connected to the second shell part  101 . 2 . The two shell parts  101 . 1  and  101 . 2  can be held together by one or two rings which can be slid over the cylinder parts  101   c ′ and  101   c ′″. The rings can preferably manufactured from PEEK, PU or from another polymer that can be used in implanted parts. In principle, the manufacture from a biocompatible metal, such as, for example, titanium or a titanium alloy such as Platinum/iridium or high grade steel, is also considered. In addition, at least one of the rings can be an X-ray contrast ring, consisting at least in parts of a radiopaque material such as, i.e., Platinum/iridium. In addition or alternatively, the housing parts, in particular, the first and second shell parts  101 . 1  and  101 . 2 , of the head housing are expediently welded or adhesively bonded together. 
         [0041]    When comparing the two drawings, it can be easily seen that the half-shells  101 . 1 ,  101 . 2  are not identical, but have different projections and returns or stops and centering means, both in the region of the distal flange and of two of the three stepped cylindrical regions and lastly also in the region of the partition walls. Inter alia, it is thus ensured that there are overlap regions of sufficient size in the wall of the head housing between the first and second half-shell so as to ensure high mechanical stability and tightness of the rear region of the head housing. Due to the asymmetric form of the two shell parts  101 . 1  and  101 . 2 , it is sufficient if the two shell parts  101 . 1  and  101 . 2  are held together by one or two rings which can be slid over the cylinder parts  101   c ′ and  101   c ′″. In this case the housing parts, in particular, the first and second shell part  101 . 1  and  101 . 2 , of the head housing do not necessarily need to be welded or adhesively bonded together. It can be seen from  FIG. 6 , that the second shell part has a pin  12  so that the helical coil acting as a fixation screw can be rotated out from the head housing in distal direction. 
         [0042]    It can be seen from  FIGS. 5 and 7  how the helical coil  3  fills the distal chamber  101 A of the electrode head  101  in the retracted state in its entire length and surrounds, via its proximal end, a ram  5   a  of a fixing screw actuation shaft  5 , to which it is fastened (not visible here) in an integrally bonded manner (for example, by means of welding). In the second chamber  101 B, the fixing screw actuation shaft  5  is surrounded by a ring seal  7  in such a way that the periphery of the chamber  101 B is largely filled. In the third chamber  101 C, a contact sleeve  11  for electrically contacting the conductor coil (not shown here) of the electrode line body with the ram  5   a  or the helical coil  3  can be seen. 
         [0043]    One or more of the helical coil  3 , the fixing screw actuation shaft  5  and the ram  5   a  of the fixing screw actuation shaft  5  can consist at least in part of a radiopaque material. In case both rings are made as X-ray contrast rings and at least the ram  5   a  of the fixing screw actuation shaft  5  consists at least in part of a radiopaque material, it is possible to inspect how far the helical coil acting as a fixation screw has been rotated out from the head housing in distal direction. 
         [0044]    It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teachings of the disclosure. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention, which is to be given the full breadth thereof. Additionally, the disclosure of a range of values is a disclosure of every numerical value within that range.