Abstract:
A probe including at its distal extremity a tubular flexible sheath core supporting at least a winding forming a shock electrode and connected to a electrical conductor of connection extending in a internal lumen of the sheath core. In a way characteristic of the invention, the sheath core extends axially without a solution of continuity in the area supporting the winding. In particular, the sheath core comprises cavities to receive and hold conducting inserts, of homologous size with cavities formed locally close to the ends of the winding, the insert being connected to the interior side to the electrical conductor, and on the external side to the corresponding extremity of winding. A longitudinal slit connects the two cavities and allows, by elastic deformation of the sheath core, the introduction into the cavities and in the internal lumen of the unit formed by the final extremity of the electrical conductor beforehand equipped with its two inserts.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to “active implantable medical devices” as defined by the Jun. 20, 1990 Directive 90/385/CEE of the Council of the European Communities.  
       BACKGROUND OF THE INVENTION  
       [0002]     The invention more particularly concerns the family of apparatuses that deliver to the core pulses of high enery (i.e., pulses notably exceeding the energy provided for simple stimulation) to try to put an end to a tachyarrhythmia. These devices are called “implantable defibrillators” or “implantable cardiovertors,” it being understood that the invention also covers implantable defibrillators/cardiovertors or defibrillators/cardiovertors/stimulators.  
         [0003]     “Implantable defibrillator” or “implantable cardiovertor” devices have two principal parts—a pulse generator, and a probe or a system of probes. The pulse generator monitors cardiac activity and generates high energy pulses when the heart presents a ventricular arrhythmia that is deemed susceptible to being treated. When the high energy is comprised between approximately 0.1 and 10 J, the therapy is referred to as “cardioversion” and the electric shock is called “cardioversion shock.” When the high energy is greater than approximately than 10 J, the therapy is called defibrillation and the electric shock is called “defibrillation shock.” The pulse generator is connected to one or more probes comprising electrodes whose role is to distribute this energy to the core in a suitable way.  
         [0004]     The present invention relates to the particular case where the generator is connected to a “mono-body” probe, that is a single probe carrying the various electrodes making it possible to deliver shocks of defibrillation or cardioversion. The shock electrodes appear as windings of wire supported by a distal tubular extremity of the probe and are intended to come into contact with cardiac tissues at the place where the cardioversion or defibrillation energy must be applied. The windings are connected to a conducting wire traversing the length of the probe.  
         [0005]     Mono-body probes generally comprise two shock electrodes: a first electrode, known as “supraventricular,” which will be positioned in the high vena cava to apply the shock to the atrium; and a second electrode, a ventricular one, which will be located more closely to the distal extremity of the probe.  
         [0006]     The mono-body probes are generally of the “isodiameter” type, i.e., they have the same diameter over the entire length of the distal part intended to be implanted in the venous network. This facilitates implantation, as well as any later explantation. This means that the external surface of the windings forming the shock electrodes is flush with the external surface of the probe, so as not to present any change in diameter along the implanted length of the probe.  
         [0007]     The manufacturing of these mono-body probes is relatively delicate, taking into account the presence of the windings, the requirements for continuity of probe diameter, and the need for carrying the electric connection inside the body of the probe with the electrical conductor allowing delivery of the shock energy.  
         [0008]     The technique employed until now to manufacture these probes consists of taking a plurality of tubular sections of encasable sheath, one after another, setting up the windings, and electrically connecting them progressively to their internal conductor at the various sections of the tube of the probe. This structure, which makes it possible to answer the specific constraints associated with manufacturing these probes, has, however, the disadvantage of creating zones and/or electric weaknesses at the places where the various sections are connected, in particular short-circuits on the high voltage conductor supplying the shock energy. However, in practice, it has been noted that the ruptures of the insulated tube support often occur at the places of the connections between the various sections of sheath, because of the zones of weakness locally created at the place of these connections. Moreover, this structure of encased sections implies a relatively complex and long manufacturing process, in particular because of the need for sticking the successive sections together. U.S. Pat. No. 6,374,142 and PCT Application No. WO-A-02/087689 describe such mono-body isodiameter probes produced starting from encased successive sections of sheath.  
       OBJECTS AND SUMMARY OF THE INVENTION  
       [0009]     One of the goals of the present invention is to cure the above-described disadvantages by proposing another structure for the distal part of a mono-body defibrillation probe—a structure that does not present a zone of weakness in the vicinity of the windings and can be manufactured simply and quickly.  
         [0010]     The probe of the invention is a mono-body defibrillation probe of the known type described above, i.e., with a probe body that includes at its distal extremity an insulated sheath core of a tubular flexible material, supporting at its periphery at least one winding of wire forming a shock electrode for application of a defibrillation or cardioversion energy, this winding being electrically connected to an electrical conductor extending longitudinally in an internal lumen inside the sheath core.  
         [0011]     In a manner characteristic of the invention, the sheath core extends axially without solution of continuity (i.e., without interruption) in the area(s) supporting the winding(s).  
         [0012]     Very advantageously, the sheath core locally comprises a crossing cavity located in the vicinity of at least one of the winding ends. It is envisaged moreover that an insert of conducting material, of a size homologous with the aforesaid cavity, is placed therein, with this insert being electrically connected, on the interior side, with the electrical conductor and, on the external side, with the corresponding extremity of the winding.  
         [0013]     In particular, the sheath core can comprise a cavity in the vicinity of each extremity of the winding, and it then comprises also a crossing longitudinal slit connecting the two cavities and radially extending from the external surface of the sheath core to the internal lumen thereof, so as to allow, by elastic strain of the material of the sheath core on both sides of the slit, the introduction into the cavities and the internal lumen of the unit formed by the final extremity of the electrical conductor provided beforehand with the two inserts to which it was mechanically and electrically connected.  
         [0014]     In one embodiment of the invention, it is envisaged to have junction ring for mechanical and electric connection of the insert to the winding, this ring being a cylindrical ring of conducting material, with an internal surface able to cooperate with a part turned towards the outside of the insert, and an external surface comprising a connection part able to cooperate with a part turned towards the interior of the extremity of the winding. This ring can in particular comprise, in the area of internal surface able to cooperate with the insert, an assembly part capable of allowing mechanical and electric solidarization from the ring to the insert. The assembly part is preferably a part comprising a crossing opening able to allow solidarization of the ring to the insert by welding from the outside. Moreover, the diameter of the assembly part is greater than the diameter of the connection part, the difference of the diameters being approximately equal to double the thickness of the winding, so that the external surface of the ring is approximately level with the external surface of the winding.  
         [0015]     Preferably, the probe is provided with an external envelope made of a flexible insulated material sheathing the sheath core along its length, except for the area of the winding, with the diameter of the external envelope being approximately equal to the diameter of winding. In this case, the ring can also comprise, at the opposite side of the connection part, a shafting part receiving the extremity of the external envelope adjacent to the winding. For the assembly, the insert can comprise, on the interior side, a sleeve, axially oriented, for crimping the insert to the electrical wire. Preferably both the space included between the radial walls of the slit and the internal volume of the lumen in the area of the slit are provided with an electrically insulated sealing material, such as polymeric resin that is hardenable, e.g., an adhesive silicone. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     Further benefits, features, and characteristics of the present invention will become apparent to a person of ordinary skill in the art in view of the following detailed description of a preferred embodiment of the invention, made with reference to the annexed drawings, in which like reference characters refer to like elements, and in which:  
         [0017]      FIG. 1  is an overall view of a mono-body defibrillation probe according to the present invention;  
         [0018]      FIG. 2  is an enlarged perspective view, of the proximal extremity of the tubular sheath, at the place where the sheath terminates to widen and be divided into a plurality of conductors connected to a connector;  
         [0019]      FIG. 3  is a perspective view showing the sheath core and the elements that will be there inserted to later allow connection to the defibrillation winding; and  
         [0020]      FIG. 4  is a detailed cross-section of the part of the probe at the place of the defibrillation winding, showing the various internal elements and the way that the electric connection with the winding is carried out. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     In  FIG. 1 , reference  10  indicates generally a mono-body probe of which the distal extremity  12  is intended to be introduced by the venous network into the two atrial and ventricular cavities, so as to detect there cardiac activity and apply as needed a defibrillation or cardioversion shock. The probe is provided at its proximal extremity  14  with various elements for connection to an appropriate generator, e.g., a generator of the Defender or Alto or Ovatio type manufactured by the assignee hereof, ELA Medical, Montrouge, France.  
         [0022]     Probe  10  carries a first shock electrode  16 , intended to be placed in the right ventricle and constituting, e.g., the negative terminal for application of the potential voltage of defibrillation or cardioversion. This ventricular shock electrode  16  is connected by a connection conductor  18  on a connection terminal  20  to the generator, advantageously a terminal of the DF-1 standard type.  
         [0023]     Probe  10  also carries at its distal part  12  a second shock electrode  22 , which is known as a “supra-ventricular” an electrode, intended to be positioned in the high vena cava for application of a shock to the atrium. This supra-ventricular shock electrode  22  is connected by connection conductor  24  on connection terminal  26  to the generator, preferably also with a DF-1 standard connector.  
         [0024]     Probe  10  is also equipped with an extremity electrode  28 , which is a detection/stimulation electrode intended to be positioned at the bottom of the right ventricular cavity. This electrode  28  is connected by a conductor  30  on a connection terminal  32  to the pacemaker, advantageously with an IS-1 connector standard.  
         [0025]     As shown in  FIG. 4 , conductor  30  is a hollow conductor, e.g., a conductor internally wound, having in its center a lumen  34  that allows introduction of a stylet for the guidance of distal extremity  12  by a physician into the venous network at the time of implantation of the probe  10 .  
         [0026]     Referring again to  FIG. 1 , the defibrillation potential can be applied between the supra-ventricular shock electrode  22  and the generator case, or between the ventricular shock electrode  16  and the generator case, or between electrodes  16  and  22 , in a bipolar mode.  
         [0027]     The configuration just described (i.e., two defibrillation electrodes and one stimulation electrode) is, however, not restrictive, and the invention is also applicable to the case of a probe equipped with only one defibrillation electrode winding, or not including a distal stimulation electrode, or including two stimulation electrodes (for a stimulation in bipolar mode, in particular), etc.  
         [0028]      FIGS. 2 and 4  more precisely show the configuration of three conductors  18 ,  24 , and  30  in the distal tubular extremity  12  of the probe  10 . These conductors are placed in respective lumens of a tubular sheath core  36  made out of a flexible insulated material such as a silicone. The conductors  18  and  24 , which must transmit the defibrillation or cardioversion energy, are micro-cables having their own insulators, respectively 38 and 40, e.g., in ETFE. The silicone material constituting the sheath core  36  presents excellent properties of fatigue strength. Regardless, it would be difficult to make the sheath core  36  penetrate in the venous network just as it is, and for this reason the sheath core is wrapped outside by a sheath  42  made out of a material with low coefficient of friction, e.g., polyurethane.  
         [0029]     The present invention relates more particularly to the way in which the probe  10  is constructed/assembled in the vicinity of the shock electrode windings  16  and  22 .  FIGS. 3 and 4  illustrate a preferred structure for the ventricular shock electrode winding  16 . Because this structure is the same supraventricular shock electrode winding  22 , the structure for that winding will not be further described in detail.  
         [0030]     In a way characteristic of the invention, the sheath core  36  is a solid tube, without solution of continuity over the entire length of the distal part  12 , in particular in the area of the windings  16  and  22 . This is due to a particular structure of the electric connection system between the winding and its corresponding conductor located inside the sheath core  36 .  
         [0031]     Thus, as illustrated in  FIGS. 3 and 4 , conductor  18 , intended to feed the winding  16 , is equipped with two metal parts  46 ,  46 ′ which function as inserts, solidarized mechanically, and electrically connected, with the conductor  18  by setting of (sliding) sleeves  48 ,  48 ′ over a stripped length emerging from insulator  38 .  
         [0032]     It is indeed desirable to have an electric connection of conductor  18  with the two ends of winding  16 , in order to produce the most homogeneous possible electric field between these two ends at the time of application of the defibrillation or cardioversion energy. If the winding is fed by its two ends, the current density will be better distributed, thus avoiding the risk of burning the surrounding tissues. For a defibrillation shock that can require application of energy of up to 40 joules, the peak voltage can reach 750 V. For this voltage, the homogeneity of the electric field at the time of the shock is a significant constraint to take into account when designing the probe.  
         [0033]     As illustrated in  FIG. 3 , the sheath core  36  comprises two cavities  50 ,  50 ′, which extend from the external surface of the sheath core to the lumen  44  ( FIG. 4 ) receiving conductor  18 . These two cavities  50 ,  50 ′ are joined together by a longitudinal slit  52  ( FIG. 3 ), which extends along the sheath core  36  and radially from the external surface of the sheath core to the lumen  44  ( FIG. 4 ) receiving conductor  18 . The interior dimensions of these cavities  50 ,  50 ′ are homologous with the external dimensions of inserts  46 ,  46 ′, so that the inserts can be entirely placed into the cavities, with their upper surface  54  ( FIG. 4 ) being level with the upper surface  56  of the sheath core  36 . On the interior side, the lower face  58  of insert  46  preferably rests on the surface  60  of the lumen  44 .  
         [0034]     The electric and mechanical connection of inserts  46 ,  46 ′, and thus of conductor  18 , with winding  16 , is carried out via junction rings  62 ,  62 ′. The junction ring  62  presents a central part  64 , from which interior surface  66  comes in contact with the upper surface  54  of insert  46 . The external surface  68  of the central part  64  has a diameter roughly equal to the external diameter of winding  16  and the external diameter of the polyurethane sheath  42 ; based on that, the external surface  70  of the sheath is level with the external surface  68  of the ring, thus ensuring the required isodiameter configuration. On the side that is farthest from the winding  16 , ring  62  comprises a part of lesser diameter  72  intended to fix with force (friction force fit) in the interior extremity of the external sheath  42 . On the side that is closest to the winding, the ring  62  comprises a part of lesser diameter  74  intended to fix with force in the interior extremity of winding  16 .  
         [0035]     To ensure the electric and mechanical solidarization of insert  46  to the connection ring of  62  (and thus winding  16 ), the central part  64  of the ring is equipped with an opening  76 , making it possible to carry out from the outside welding point  78  (like that illustrated on the right  FIG. 4 ), preferably a laser welding point.  
         [0036]     Lastly, under winding  16 , the remaining space around conductor  18  and around the various contiguous elements is filled with an electrically insulated sealing material, e.g., a setting polymeric resin, such as a resin silicone.  
         [0037]     One now will describe the manner of carrying out such a probe structure with a mechanical continuity of the sheath core  36  in the area supporting the electrode.  
         [0038]     First of all, the sheath core  36  is prepared with its external sheath  42  only in the proximal area of the probe, i.e., on the left part of  FIG. 4 . This external sheath thus stops in the vicinity of cavity  50  on the proximal end of the probe  16 , i.e., toward the left in  FIGS. 3 and 4 . Separately (e.g., on another preparation setup) insulator  38  of conductor  18  is stripped on its distal side over an adaptable length, to crimp there two contact blocks  46 ,  46 ′ at a desired distance, by means of sleeves  48 ,  48 ′. The unit obtained is illustrated partly on the top portion of  FIG. 3 . Conductor  18  is then threaded by its proximal extremity (i.e., the one opposed to the contact blocks  46 ,  46 ′) into lumen  44  via opening  50  of the sheath core  36 , while letting exceed on the distal side the free part with the inserts  46 ,  46 ′. The set formed by this length of wire with the inserts  46 ,  46 ′ is then completely introduced inside the sheath core  36 , by placing two inserts  46 ,  46 ′ in the two homologous cavities  50 ,  50 ′, with the part of conductor  18  connecting these two inserts being introduced by elastic deformation of sheath core material on both sides of slit  52 . Once the unit is thus introduced, sleeves  48 ,  48 ′ and conductor  18  find their place inside lumen  44  and the two lips of slit  52  can thus regain their initial shape. The unit is maintained tightly in place with a local injection, via slit  52 , of a resin silicone mass (reference number  80  on  FIG. 4 ), which thus comes to fill lumen  44  at the place of slit  52  and cavities  50 ,  50 ′, with a tight obturation of lumen  44  on both sides of the unit thus made up.  
         [0039]     The following stages consist of, successively: 
        1. slipping on the ring  62 ,     2. fixing the ring  62  in the part of external sheath  42  located on the proximal side of the probe (on the left on  FIG. 4 );     3. slipping on the winding  16 ;     4. fixing the proximal extremity of the winding on the ring  62 ;     5. slipping on the ring  62 ′;     6. fixing the ring  62  on the distal extremity of the winding  16 ;     7. slipping the sheath  42 ′ on the distal side of the probe; and     8. fixing on the ring  62 ′.        
 
         [0048]     The unit is thus mechanically assembled. The operation is repeated identically for the other winding. Laser welding points  78  make it possible to perform the electric and mechanical connection of the rings  62 ,  62 ′ on the one hand to the ends of winding  16  (in zone  74 ), and on the other hand to the respective inserts  46 ,  46 ′.  
         [0049]     One skilled in the art will appreciate that the present invention can be practiced by other than the described embodiments, which are presented for purposes of illustration and not of limitation.