Abstract:
An electrode connection for an electrode catheter including an electrode, a line for electrical signals configured as a coil having an electrode end connected to the electrode, and a fixation device for the electrode end of the coil on the electrode, wherein the fixation device includes an inner sleeve, on which the electrode end of the coil sits, and a squeeze ring, which acts upon the electrode end of the coil, establishing an electrical contact with the electrode and mechanical clamping on the inner sleeve.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application claims the benefit co-pending U.S. Provisional Patent Application No. 61/367,889, filed on Jul. 27, 2010, which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a form-fitting electrode connection, in particular for an electrode catheter, comprising an electrode, a line for electrical signals, embodied as a coil connected to the electrode, and a fixation device for the electrode end of the coil to the electrode. 
       BACKGROUND 
       [0003]    With regard to the background of the invention, it should be pointed out that the mechanical and electrical connection of the line embodied as a coil in an electrode catheter having a head or ring electrode—for example, in a cardiac pacemaker electrode—must be particularly reliable because an interruption in this connection would lead to failure of the electrode catheter, which could have fatal consequences for the patient. Furthermore, such a defect would necessitate replacement of the electrode catheter, which would in turn necessitate an interventional procedure with all the usual accompanying circumstances, risks and consequences for the patient. 
         [0004]    Mechanical and electrical connections of the coil to the electrode based on welding and crimping processes are fundamentally known and customary through obvious prior use. Although such connections are quite acceptable with regard to their reliability, these known approaches still have various disadvantages. 
         [0005]    In welding, the material of the coil must naturally be fundamentally weldable. To this extent, welding processes cannot be used with coil wires made of various core and sheath materials, which have different melting points. Furthermore, the materials to be joined must be coordinated with one another, so that they can be welded to one another. This depends on the melting points of the welding partners and the diffusion of alloy elements therein. This may lead to embrittlement of the joining partners in the area of the heat influence zone. Components having very thin walls within the electrode device are fundamentally very problematical to weld. Another disadvantage is the inability to inspect such a welded joint. It is quite possible for an initial inspection for mechanical strength and electrical contact to be positive even if the weld is defective in the long run. Finally, even the smallest impurities on the components may lead to incomplete welded joints and thus result in manufacturing rejects. 
         [0006]    The crimping mentioned above has safety deficiencies from the standpoint of production technology inasmuch as the quality of the joint usually depends on the hardness of the components. Furthermore, small diameters of components involved in a crimped connection are not possible because it is necessary to provide certain minimum wall thicknesses and a design of the joint adapted to the crimping technique together with an essential supporting structure and a separate crimping sleeve. 
         [0007]    Against the background of the problems associated with the state of the art described above, an object of the present invention is to improve upon an electrode connection in its fixation device for the electrode end of the coil to the electrode, so that a secure mechanical and electrical connection of the coil to the electrode can be created, regardless of the materials used. 
       SUMMARY 
       [0008]    The object is achieved by an electrode connection having a fixation device, comprising:
       an inner sleeve, on which the electrode end of the coil sits, and   a squeeze ring, which acts on the electrode end of the coil, establishing electrical contact with the electrode and mechanical clamping on the inner sleeve.       
 
         [0011]    The inventive electrode connection avoids the problems of the state of the art described herein. First, no welded joint is used, so the fixation device is able to establish a connection between the wire coil and the electrode regardless of the materials used. Second, since this is a purely mechanical process, better monitoring ability is also provided, which essentially leads to an improvement in the quality of the joint. 
         [0012]    Certain dependent claims (e.g., claims  2 - 6 ) characterize a first advantageous implementation of the basic principle of the electrode connection as defined in independent claim  1 . This first variant is based on a type of form-fitting connection between the coil end, which is widened due to the outer cone of the inner sleeve, with the squeeze ring, which is provided with a suitable inner cone and is pushed onto the widened coil end. In particular, the squeeze ring is pushed onto the coil end with deformation of the line forming the coil end, so that an intimate and fixed connection is established in the manner of a form-fitting connection between the inner sleeve, the wire coil and the squeeze ring. 
         [0013]    A second variant of the basic concept as characterized in other dependent claims (e.g., claims  7 - 12 ) is based on a type of screw connection, in that the electrode end of the coil, which is wound openly, is screwed onto the inner sleeve by engaging a threaded element behind it, and the section of the coil element screwed over the threaded element is acted upon by the squeeze ring, in particular, axially against the threaded element. Due to the resulting compression of the openly wound coil end, in particular, up to blocking by the squeeze ring, a type of self-locking effect is induced in the screw connection between the wire coil and the inner sleeve, making any release of the mechanical and thus electrical connection between the inner sleeve and the coil end fundamentally impossible. 
         [0014]    Various other objects, aspects and advantages of the present invention can be obtained from a study of the specification, the drawings, and the appended claims. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0015]    Additional features, details and advantages of the invention are derived from the following description of exemplary embodiments on the basis of the accompanying drawings, in which: 
           [0016]      FIG. 1  shows a side view of an electrode catheter, 
           [0017]      FIGS. 2 and 3  show enlarged details of longitudinal axial sections of the electrode catheter in the area of a ring and head electrode in a first embodiment, 
           [0018]      FIG. 4  shows an enlarged detail of a longitudinal, axial section of an electrode catheter in the area of the head electrode in a second embodiment, 
           [0019]      FIG. 5  shows a side view of the inner sleeve used in the fixation device according to  FIG. 4 , and 
           [0020]      FIG. 6  shows an axial view of the inner sleeve according to  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    As shown in  FIG. 1 , in particular, the electrode catheter, which is used for cardiac therapy, comprises an elongated tubular catheter body  1 , which is provided with a connecting plug  2  at its proximal end for connection to a corresponding implant. A ring electrode  4  is arranged in the area of the distal end  3 , and there is a head electrode  5  directly at the tip of the distal end  3 . These electrodes  4  and  5  serve to deliver or measure an electrical signal, i.e., an electro-cardiac signal in the present case, via their respective external electrode contact surfaces  6  and  7 , for example, for reliable and effective defibrillation or diagnostic testing for early detection of atrial fibrillations and progression of cardiac insufficiency. 
         [0022]    On the basis of  FIGS. 2 and 3 , a first embodiment of the connection of electrodes  4  and  5  to corresponding feeder lines  8  and  9  is explained. Two such feeder lines  8  and  9  in the form of coils  10  and  11  sitting coaxially one inside the other are thus guided from proximally in the tubular catheter body  1 . The outer coil  10 , with the feeder line  8 , serves to form a connection to the ring electrode  4 , as illustrated in  FIG. 2 . The inner coil  11  is continued in the distal direction through the electrode  4  with insulation. 
         [0023]    The fixation device, which is illustrated in  FIG. 2  and is labeled as  12  on the whole, has an inner sleeve  13  on which the electrode end  14  of the coil  10  sits. The inner sleeve  13  is provided with an outer cone  15 , which is widened in the distal direction and on which the coil end  14  is placed in assembly and, therefore, also sits with a widened conical shape. 
         [0024]    A squeeze ring  16 , which is provided with an inner cone  17  that also widens in the distal direction, is pushed onto the module comprising the inner sleeve  13  and the electrode end  14  of the coil  10 . The squeeze ring  16  is threaded onto the coil  10  before the electrode end  14  is pushed onto it and, after connecting the coil  10  to the inner sleeve  13 , it is pushed further in the distal direction, and the widened coil end is more or less squeezed onto it. The feeder line  8  forming the coil end  14  is deformed slightly, so that a type of form-fitting connection is established between the inner sleeve  13 , the coil end  14  and the squeeze ring  16 , achieving a mechanically stable and electrically secure connection between these components, which are made of an electrically conductive material. In the distal end area, the squeeze ring  16  is secured by placing it on a bearing shoulder  18  on the end of the inner sleeve  13  facing distally. 
         [0025]    The cone angles K 15  and/or K 17  on the outer cone  15  of the inner sleeve  13  and/or on the inner cone  17  of the squeeze ring  16  are shallow and amount to approximately 15° and, in particular, preferably approximately 10°, for example. Furthermore, they match in their angle values. In one form, it is contemplated that the angles be smaller than 15°. 
         [0026]    To establish an electrical connection between the coil  10  and the ring electrode  4 , on its side  19  facing radially outward the squeeze ring  16  is connected to the ring electrode  4  in an electrically conducting manner, for example, by a physically bonded connection. 
         [0027]    The inner coil  11  of the feeder line  9  is continued in the distal direction through the inner bore  20  of the inner sleeve  13  to the head electrode  5  with an insulating tube  21  in between (see  FIG. 3 ). 
         [0028]      FIG. 3  shows a fixation device  12  like the fixation device explained with reference to  FIG. 2  for connecting the inner coil  11  to the feeder line  9  on the head electrode  5 . This design corresponds to that of the fixation device  12  according to  FIG. 2 , and to the extent that the description of the fixation device  12  from  FIG. 2  can be applied fully to the design shown in  FIG. 3 , reference can be made thereto in order to avoid repetition. Components having the same design are labeled with identical reference numerals. 
         [0029]    The inner bore  20  of the inner sleeve  13  of the fixation device  12  on the head electrode  5  serves to pass through a mandrel and/or guide wires for the electrode catheter. A central head bore  22  in the head electrode  5  is aligned with the inner bore  20 . 
         [0030]      FIGS. 4-6  show an alternative embodiment of a fixation device  12 ′ for connecting a coil  11  of the feeder line to the head electrode  5 . The fixation device  12 ′ has an inner sleeve  13 ′, which is embodied not as a cone but instead as a cylindrical sleeve with regard to its base body. At approximately one-fourth of its total length, a threaded element in the form of a web  24  running over a partial circumference of the inner sleeve  13 ′ is designed on the lateral surface  23  of the inner sleeve  13 ′. As shown in  FIGS. 5 and 6 , in particular, the web  24  runs over an angle W of approximately 240° to 300° and, preferably 270°, in the peripheral direction P around the inner sleeve  13 ′. The web has a height “h”, which is slightly greater than the diameter “d” of the feeder line  9  forming the coil. Its width “b” corresponds approximately to the diameter “d”. 
         [0031]    As shown more clearly in  FIG. 4 , the coil  11 ′ is provided with winding gaps and may thus be screwed onto the inner sleeve  13 ′ over the threaded element web  24  until multiple windings have passed by the web  24 . Then, a squeeze ring  16 ′ is pushed onto the distal end of the inner sleeve  13 ′ against the screwed-on coil windings  25 , so that the coil windings  25  are acted upon in such a way that they are compressed on block. This state is illustrated in  FIG. 4 . Because of this compression, the winding package  25  is secured between the squeeze ring  16 ′ and the web  24  by a self-locking effect, so that the coil  11 ′ cannot be un-screwed and, therefore, it is impossible to loosen the connection between it and the inner sleeve  13 ′. 
         [0032]    The squeeze ring  16 ′ is secured on the inner sleeve  13 ′ by suitable measures, such as, for example, a bonded connection Likewise, the side  19 ′ of the squeeze ring  16 ′ facing radially outward is again securely connected electrically and mechanically to the head electrode  5  by, for example, a bonded connection. 
         [0033]    The inner bore  20 ′ of the inner sleeve  13 ′ together with the head bore  22  of the head electrode  5  in turn serves to provide passage for a mandrel or guide wires for the electrode catheter. 
         [0034]    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.