Abstract:
A method for constructing a plug for an electrical connection to a multipolar lead for an active implantable medical device includes providing a plug body having an insulating monobloc central core, the monobloc central core having a generally cylindrical shape, a cylindrical side surface, and a housing, providing a connection wire and a conductive pod, attaching the connection wire to the conductive pod, placing the conductive pod into the housing with connection wire extending therefrom, placing a conductive cylindrical ring on the cylindrical side surface, wherein the cylindrical side surface centers the conductive cylindrical ring coaxially about the monobloc central core, attaching the conductive pod to the cylindrical ring to create an electrical contact zone on a cylindrical outer surface of the plug body.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    This application is a continuation of application Ser. No. 13/423,030 filed Mar. 16, 2012, hereby incorporated by reference in its entirety, which claims the benefit of French Application No. 1152166 entitled “Electrical Connection Plug For A Multipolar Lead Of Active Implantable Medical Device” and filed Mar. 16, 2011, which is hereby incorporated by reference in its entirety. 
     
    
     FIELD 
       [0002]    The present invention relates to active implantable medical devices as defined by the Jun. 20, 1990 directive 90/395/CEE of the European Community Council, more particularly to devices that continuously monitor the cardiac activity of a patient and deliver if necessary to the heart electrical pulses for stimulation, cardiac resynchronization, cardioversion and/or defibrillation in case of a rhythm disorder detected by the device, and to neurological devices, cochlear implants, drug pumps, and implanted biological sensors. The present invention even more particularly relates to an electrical multi-polar connection plug for a lead such as a monobody lead equipped with both stimulation and defibrillation shock electrodes. 
       BACKGROUND 
       [0003]    Active implantable medical devices generally include a housing, which is often called “the generator”, that is mechanically and electrically connected to one or more “leads” that have electrodes that in turn come into contact with the tissues to which it is desirable to apply electrical pulses and/or to collect an electrical signal of the patient&#39;s myocardium, nerve, or muscle. 
         [0004]    Standardized connection systems have been used for years to ensure an interchangeability of the leads and generators produced by different manufacturers. Thus, the standards called “IS-1” and “IS-4” define a number of dimensional and electrical characteristics for the leads to be connected to the generator. For defibrillation or cardioversion leads, wherein electrical stresses are more severe in view of the high energy passing from the generator to the lead, the “DF-1” and “DF-4” standards define the dimensional and electrical characteristics of the connection system. 
         [0005]    The complexity of multi-polar leads, which already incorporate specific constraints in terms of the electrical energy associated with delivery of pacing or shock pulses, is enhanced by the development of multisite devices and intracardiac sensors, such as peak endocardial acceleration (PEA) sensors. This complexity leads, in terms of connectivity, to a proliferation of connection plugs, in addition to different standards depending on the plugs. 
         [0006]    It is thus desirable to obtain a single plug that is subject to a single standard having a plurality of electrical contacts to simultaneously ensure connections to various terminals of the generator for all applicable energy levels, whether for the collection of depolarization signals, for the application of stimulation pulses or for the delivery of a defibrillation shock. In this context, a single “isodiametric” connection plug, namely a plug having a uniform cylindrical shape, designed to be inserted in a counterpart cavity of the generator, is known. 
         [0007]    EP 1641084 A1 and its counterpart U.S. Pat. No. 7,175,478 (both assigned to Sorin CRM S.A.S. previously known as ELA Medical) describes one such isodiametric connection plug with the outer cylindrical surface having a stack of annular electrical contact zones, realized with alternating conductive cylindrical rings and insulating zones, the latter designed to electrically isolate the conductive rings. In addition, each electrical contact in the cavity of the generator must be isolated from the other contacts and from the environment outside the cavity by suitable seals. Originally placed on the lead, these joints are now placed in the cavity because of the fact, more particularly for defibrillation leads, high voltages are applied to the contact elements. It is therefore essential that the connecting pins of the multipolar leads are dimensionally stable over time and comply, with precise tolerances, with the geometric description of the imposed standards. These requirements help ensure that the electrical contact zones and insulating zones coincide with the corresponding zones of the cavities of the generators, when inserting the connector plugs into the cavities, as well as during the useful life of the active implantable medical device. 
         [0008]    In this context, two key parameters must be taken into account, namely, on the one hand, the surface state of the electrical contact and insulating zones, and on the other hand, the coaxiality of the electrical contact and insulating zones along the connection plug. These parameters are indeed crucial for the quality of the electrical contact in the generator cavity and for sealing the system. 
         [0009]    With these constraints, the difficulty of making a plug connector with a constant diameter along the entire length of the part and with multiple electrical contacts is increased, which in turn raises many manufacturing problems. In addition, the constraint of a small outer diameter (e.g., 3.2 mm according to ISO 27186) limits the design possibilities, so that the impact of complying with tight tolerances that are needed for industrial production can be considerable in terms of time and cost. 
         [0010]    In this context, the connection plug described in EP 1641084 A1 and U.S. Pat. No. 7,175,478 mentioned above is not entirely satisfactory, because it does not guarantee a perfect coaxiality of the different zones. Indeed, in this prior art plug, the electrical contact zones and insulating zones are defined by cylindrical elementary parts the axial and angular alignment of which is obtained by longitudinal rods fitted in bores formed in each counterpart section of elementary parts. However, the minimum functional space between the pins and bores to allow stacking of the elementary parts leads to a lack of concentricity of the assembly, detrimental to the electrical contact and sealing of the connection plug inside the generator cavity. 
         [0011]    U.S. Patent Publication No. 2005/221671 A1 proposes a plug for electrical connection of a multipolar lead for an active implantable medical device, said plug having a cylindrical outer surface including a plurality of annular electrical contact zones axially distributed and formed of conductive cylindrical rings, the electrical contact zones being alternately separated by a plurality of intercalary insulating cylindrical zones. The plug connector further includes an insulating monobloc core, a piece having a generally cylindrical shape and a plurality of coaxial centering side cylindrical surfaces, with a conductive ring being placed on at least one centering side surface. The desired coaxiality of the conductive rings directly results from the centering side surfaces formed during the manufacture of the monobloc core piece. The fact that there is a unique piece for the central core, so with no functional clearance, ensures the long term stability of the coaxial rings. 
         [0012]    However, the described structure requires welding the wire “blind” in a through-hole of the conductive ring, without the possibility of any visual inspection of the weld integrity. The problem of correct positioning of the different rings (i.e., the conductive rings provided with their welded wire and the insulating rings) during the assembly of the plug also remains, while satisfying the constraints of longitudinal alignment and of centering of the rings (namely, for an optimum, and desired perfect, coaxiality of the electrical contact and insulating zones), with a sufficient reproducibility and reliability, without significant increase in production costs and with simple parts and simple manufacturing and control processes, as appropriate for an industrial solution with profitability and efficiency for production in large quantities. 
       OBJECT AND SUMMARY 
       [0013]    To this end, broadly, the present invention is directed to a multipolar lead having a core comprising a plurality of housings receiving a corresponding plurality of intermediary conductive pods on which connection wires are welded, the pods being welded to respective conductive rings. 
         [0014]    Advantageously, the intermediate pods have a slot for insertion of the connection wire, aligned in the axis of the core or transverse to the core axis. 
         [0015]    In practice, the conductive rings are brought into position on the respective electrical contact zones by sliding each along the central core. To facilitate this operation, the present invention discloses that the side surfaces preferably have a centering longitudinal positioning shoulder for the conductive rings. The shoulders of the side surfaces operate in this way as an abutment for the conductive rings. This in turn provides very good precision in the positioning of the rings. 
         [0016]    In one embodiment, to facilitate the introduction of the rings on the core, advantageously the central core has a longitudinal flat for an introduction of the conductive rings on the centering side surfaces by reversible elastic deformation. A slightly oval shape is given to the rings for introduction into the core, by a slight pressure applied to the rings, possibly passing over the positioning shoulders, and axially sliding them into position, then releasing the pressure so that the rings recover their initial annular shape and engage and conform closely to the centering side surfaces. 
         [0017]    Preferably, the intermediate insulating areas are formed by insulating rings. In this embodiment, the insulating rings are alternately threaded onto the core with the conductive rings. In an alternative embodiment, the insulating rings can be made by overmolding on a conductive ring. In yet another embodiment, the intermediate insulating zones are preferably made by injection molding of an insulating material. This process concerns filling the spaces created between the conductive rings to make an isodiametric part that especially satisfies the applicable standard, in this embodiment the ISO 27186 requirements. 
         [0018]    According to a preferred embodiment, the core is molded of an insulating material such as polyetheretherketone (PEEK) or Tecothane (registered trademark), which materials are commercially available for medical purposes. 
         [0019]    Preferably, the cylindrical shape of the core allows a “natural” release, along the axis of opening of the mold, without drawers or spacers. This molding process allows for providing very precise dimensional characteristics on its surfaces, including the centering surfaces and on concentricity. Of course, the same mold can be used to make many parts. This results in excellent reproducibility of the dimensions from one part to another and commercial practicability. 
         [0020]    It should be understood, however, that the advantage of the preferred method involving molding does not prevent the core from being manufactured by machining or any other method of producing the isolating parts as would be understood by one of ordinary skill in the art. 
         [0021]    Advantageously, the present invention also addresses and resolves an issue which pertains to holding the wires in position for the bonding, which wires extend axially along the central core, from the lead to the electrical contacts of the connection plugs with the generator. In this regards, floating wires can touch each other or touch a conductive ring and are undesirable. 
         [0022]    To this end, the present invention preferably provides means for maintaining conductor connection wires along the cylindrical core which are formed on the centering side surfaces to avoid this concern. In particular, the holding means comprises a longitudinal slot formed on the centering side surfaces for applying a connection wire against the cylindrical core. Advantageously, the holding means further comprises at least one second centering side surface intended to hold a connection wire in at least one longitudinal notch. 
         [0023]    Thus, the centering side surfaces have a dual function, that of ensuring the proper centering of the conductive rings and that of holding in place the wire for the connection bonding. 
     
    
     
       DRAWINGS 
         [0024]    Further features, characteristics and advantages of the present invention will become apparent to a person of ordinary skill in the art from the following detailed description of preferred embodiments of the present invention, made with reference to the drawings annexed, in which like reference characters refer to like elements and in which: 
           [0025]      FIG. 1  is a perspective view of a multipolar lead equipped with a connection plug in accordance with a preferred embodiment of the present invention; 
           [0026]      FIG. 2  is a longitudinal section of the lead of  FIG. 1 ; 
           [0027]      FIG. 3  is a perspective view of the central core of the connection plug shown in  FIGS. 1 and 2 ; 
           [0028]      FIG. 4  is a detail view of the core of  FIG. 3 ; 
           [0029]      FIG. 5  is a front view of the central core of the  FIG. 3  disposed on a support; 
           [0030]      FIG. 6  is a perspective view of one embodiment of the central core of  FIG. 3   
           [0031]      FIG. 7  is a front view of an embodiment of the the central core of  FIG. 3  having a longitudinal flat; 
           [0032]      FIGS. 8   a  and  8   b  are perspective views of a first method for mounting a connection wire on an intermediary pod; 
           [0033]      FIGS. 9   a  and  9   b  are perspective views of a second method for mounting a connection wire on an intermediary pod; 
           [0034]      FIG. 10  is a top view of the central core of  FIG. 3  with intermediary pods; 
           [0035]      FIG. 11  is a perspective view of the central core of the  FIG. 10  showing means for holding the connection wires; 
           [0036]      FIG. 12  is a sectional view taken along line AA of  FIG. 10 ; 
           [0037]      FIG. 13  is a perspective view of a connection plug in accordance with an embodiment of the present invention during assembly of the conductive rings; 
           [0038]      FIG. 14  is a sectional view of  FIG. 12  of the connection plug shown in  FIG. 13 ; 
           [0039]      FIG. 15  is a perspective view of a connection plug plug in accordance with an embodiment of the present invention after assembly of conductive rings; 
           [0040]      FIG. 16  is a perspective view of the connection plug after an overmolding of the intermediary insulating zones in accordance with one embodiment of the present invention; 
           [0041]      FIG. 17  is a sectional view of the plug of  FIG. 16  through a contact zone; 
           [0042]      FIG. 18  is a sectional view of the plug of  FIG. 16  through an intermediary insulating zone; 
           [0043]      FIG. 19  is a perspective view illustrating an embodiment of the intermediary insulating zones; 
           [0044]      FIG. 20  is a perspective view illustrating another embodiment of the intermediary insulating zones; and 
           [0045]      FIG. 21  is a sectional view of the central core of  FIG. 7  showing a method for introduction of the conductive rings by elastic deformation. 
       
    
    
     DETAILED DESCRIPTION 
       [0046]    With reference to  FIGS. 1 and 2 , the proximal end of a multipolar lead of an implantable medical device, such as a pacemaker, defibrillator or a resynchronizer, is shown. The lead  1  includes a lead body  20  on which various connection conductors extending through a connection plug  10  are arranged in between an electrical pulse generator (not shown) and the poles of the lead  1  placed at the distal end of body  20 . In the embodiment illustrated in  FIGS. 1 and 2 , four connection conductors are represented, including a hollow conductor  24 , such as a coiled cable, electrically connected to an axial pin  104  providing an electrical contact with the axial generator and having at its center a lumen communicating with a corresponding lumen  14  formed in the axial pin  104 . This allows the introduction of a stylet for the practitioner to guide the lead during implantation in the patient or for the passage of a (conventional) screw fixation system for the lead. 
         [0047]    The hollow conductor  24  is housed inside a flexible sheath  30  of insulating material such as silicone, which has excellent fatigue resistance properties. However, to facilitate its introduction into the venous system, the sheath  30  is externally provided with a coating material having a low friction coefficient, for example, polyurethane. 
         [0048]    In addition to the hollow conductor  24 , the sheath  30  includes, in the non-limiting example illustrated in  FIG. 2 , three other connection conductors, the wires  21 ,  22 ,  23  whose proximal ends are respectively connected to three zones  11 ,  12 ,  13  of ring electrical contact axially located along the connection pin  10 . As can be seen in  FIGS. 1 and 2 , the latter is a multipolar cylindrical connection pin, plugged in a single movement in a counterpart cavity of the generator. This method of simultaneous plugging ensures the electrical connection of the various electrodes located at the poles of the lead  1  to the corresponding terminals of the generator. Such a multipolar connection plug is notably described in EP 1641084 A1 and U.S. Pat. No. 7,174,478 mentioned above. 
         [0049]    The plug  10  of  FIGS. 1 and 2  forms an “isodiametric” assembly, that is to say in which the zones  11 ,  12 ,  13  of annular electrical contact and the intercalary isolating zones  31 ,  32 ,  33 ,  34  alternately separating the contact zones exhibit a smooth cylindrical outer surface. In the embodiment illustrated in  FIGS. 1 and 2 , the zones  11 ,  12 ,  13 , are made by conductive cylindrical rings  101 ,  102 ,  103  which are connected to the wires  21 ,  22 ,  23  according to a method described hereafter. 
         [0050]    The connection plug  10  is organized around a generally cylindrical hollow monobloc central core  200 , an exemplary embodiment of which is shown in  FIG. 3 . As indicated above, core  200  can advantageously be made by natural molding of an insulating material such as PEEK (polyetheretherketone) or Tecothane (registered trademark). Recesses generically denoted  270  in  FIG. 3  are provided on the body of the core  200  to provide a form that is useful to simplify the removal of second retaining side surfaces  262   a  (see  FIGS. 4 ,  11 ). 
         [0051]    The central core  200  is mainly characterized by the presence of side surfaces  211   a,    211   b,    212   a,    212   b,    213   a,    213   b  for coaxial centering, to obtain a very simple and low cost optimum coaxiality of the annular conductive rings  101 ,  102 ,  103  when during the assembly of the plug  10 , they are placed on the side surfaces. To this end, the curvature of the side surfaces and the inner curvature of the rings must be identical.  FIG. 4  is a more detailed view of the side surfaces  213   a,    213   b.    
         [0052]    The electrical connection between the connection wires  21 ,  22 ,  23  and the annular conductive rings  101 ,  102 ,  103  preferably can be performed as follows. Initially, according to  FIGS. 8   a ,  8   b ,  9   a ,  9   b , the connection wires  21 ,  22 ,  23  are connected to intermediate conductive terminals pods, generically referenced  240 , which are disposed within housings  201 ,  202 ,  203  provided on the core  200  and which can be seen in greater detail in  FIGS. 3 ,  4 ,  6 ,  10 . 
         [0053]    Pods  240  are preferably made of a biocompatible conductive material, such as stainless steel 316 SS or MP35N. The connection wires  21 ,  22 ,  23  are preferably protected by an insulating sheath made of Ethylene TetraFluoroEthylene (ETFE) or PolyTetraTluoroEthylene (PTFE), the wires being then stripped to their end connected to the terminal through intermediary pod  240 . Pods  240  can be machined. 
         [0054]    Given the position of housings  201 ,  202 ,  203  on core  200 , that is to say at the location of annular rings  101 ,  102 ,  103 , the external curvature of pod  240  must be compatible with the inner curvature of the rings. 
         [0055]    Two embodiments of pod  240  are proposed. The first version, as illustrated in  FIGS. 8   a ,  8   b , allows directly alignment of connection wire  23  in the axis of core  200 . In this case, to allow easier introduction of connection wire  23 , intermediary pod  240  has an insertion groove  241 . In the second version, as illustrated in  FIGS. 9   a ,  9   b , wires  21 ,  22  are transversely placed, making it necessary to bend them and fold them to realign them in the axis of core  200  and redirect them to body  20  of the lead. 
         [0056]    The electrical connection between connection wires  21 ,  22 ,  23  points and intermediary pod  240  can be achieved by laser welding, electric welding or any other suitable technology for linking together two metal parts. 
         [0057]    Then, pods  240  provided with their respective wires are placed in housings  201 ,  202 ,  203 . The wires  21 ,  22  which are transversely coming out of the axis of the core  200  are inserted into slots formed on the side surfaces  212   a  and  211   b  and then they are bent and folded so that they extend along the core  200 , in parallel to its axis, as shown in  FIG. 11 . 
         [0058]    The assembly operation can be performed under conventional binocular viewing, with the support tooling shown in  FIG. 5 , wherein the core  200  is placed on a horizontal support on a hollowed plate  2  with two lateral wings  230   a,    230   b  arranged at the end to the core. 
         [0059]    According to an advantageous feature, core  200  is provided with means for maintaining connection points of wires  21 ,  22  in their position illustrated in  FIG. 11 , namely against the core and parallel to its axis. These holding means generally include longitudinal notches formed on the centering side surfaces. 
         [0060]    For example, the section view of  FIG. 12  shows longitudinal slots  253   a,    253   b  formed in the centering side surfaces  213   a,    213   b,  these notches being intended to respectively apply and maintain the connection wires  21 ,  22  against the core  200 . As shown in  FIG. 11 , connection wire  22  is also maintained by longitudinal slot  252   a  of side surface  212   a.    
         [0061]    In order to improve the retention position of the connection wires, second centering side surfaces are provided on the core  200  to retain the connection wires  21 ,  22  in the longitudinal slots once they are introduced there. As illustrated in  FIG. 11 , for example, the second retaining side surfaces of wire  22  are referenced  261   a ,  262   a.  Other side surfaces of this type, not shown in the drawings, are symmetrically present to hold the wire  21  into the corresponding slots. 
         [0062]    According to  FIG. 13 , conductive annular rings  101 ,  102 ,  103  are then put in place by sliding along the axis of core  200  to get them respectively next to pods  240  to which they must be electrically connected.  FIG. 14  shows a sectional view of the final disposition of the conductive ring  103  around the core  200 . The core  200  equipped with all conductive rings is shown in  FIG. 15 . 
         [0063]    Rings  101 ,  102 ,  103  are then welded to intermediate pods  240  by laser welding, electrical welding or any other suitable technology. This can be done ring after ring or on all the three rings placed at once on a positioning tool. It should be understood that the welded connection should not affect the surface finish and cylindricity of the rings. For this, for example, a welding on the side of the ring, tilting the assembly formed by the core  200 , conductor wires  21 ,  22 ,  23  connected to pods  240  and to rings  101 ,  102 ,  103  can be performed. This welding step is preferably a perfectly controlled and inspectable process, made easier by central core  200  which partly plays the role of an internal tool. 
         [0064]    The conductive rings have an outer diameter given by the applicable standard, e.g., ISO 27186. Their positioning is critical, as is their coaxiality. As already mentioned, the coaxiality is achieved by centering the side surfaces on which the rings are in support. The longitudinal positioning can be ensured by shoulders  221   a,    221   b,    222   a,    222   b,    223   a,    223   b  respectively carried by side surfaces  211   a,    211   b,    212   a,    212   b,    213   a,    213   b  that can be seen in  FIG. 6 , and against which rings  101 ,  102 ,  102  abut. 
         [0065]    In this embodiment, it is expected that core  200  has a longitudinal flat  270 , shown in  FIG. 7 , allowing introduction of the conductive rings on the centering side surfaces by reversible elastic deformation. As shown in  FIG. 21 , a conductive ring, such as ring  101  may according to this method be brought into position by successively crossing shoulders  223   a,    223   b,  and shoulders  222   a,    222   b.    
         [0066]    The final step is to fill the spaces  111 ,  112 ,  113 ,  114  shown in  FIG. 2  between rings  101 ,  102 ,  103  with an insulating material to achieve the intercalary insulating zones  31 ,  32 ,  33 ,  34  alternately separating the contact zones  11 ,  12 ,  13 , as shown in  FIG. 1 . In this operation, it must be ensured that the connection plug  10  is fully isodiametric in accordance with the applicable standard, e.g., ISO 27186, and that it guarantees the tightness of the system, which results, as noted above, in the quality of contact of the plug  10  with the seals arranged in the cavity of the generator receiving the plug. 
         [0067]    Filling spaces  111 ,  112 ,  113 ,  114  can be achieved, for example, by overmolding or injection of glue or plastics, or of another insulating material.  FIGS. 17 and 18  respectively show a section of connection plug  10  through electrical contact zone  13  and a section through insulating zone  33  after overmolding with an insulating material  280 . 
         [0068]    According to an alternative embodiment as illustrated in  FIG. 19 , the isodiameter desired for plug  10  is obtained by providing a stack of insulating rings, such as those referenced  121 ,  122  in  FIG. 20  above, and of conductive rings, the coaxiality of all rings being provided by the centering side surfaces described above, the connection between a conductive ring and a subassembly formed by a connection wire and the corresponding pod being performed before each insertion of an insulating ring. 
         [0069]    The second variant of  FIG. 20  implements pairs consisting of an insulating ring overmolded onto a conductive ring, such as pairs ring  121 /ring  101  and ring  122 /ring  102 , each pair being connected by the conductive ring to a subassembly connection wire/pod before the introduction of a new pair. 
         [0070]    It should be understood by a person of ordinary skill in the art that the present invention not only greatly simplifies the assembly of a multipolar lead connection plug, but it also allows a visual inspection at each stage of assembly. The operator thus has better control at each stage of the process. 
         [0071]    In addition, the connection plug of the present invention can either be performed directly on an existing lead body or subsequently be connected to the lead. This allows the possibility to outsource the manufacturing of the plug and to adapt it to any lead body. 
         [0072]    One skilled in the art will appreciate that the present invention can be practiced by other than the embodiments described herein, which are provided for purposes of illustration and not of limitation.