Abstract:
An implantable medical electrode device, in particular a cardiovascular cardiac pacemaker or defibrillator electrode device, comprises an elongate, tubular electrode body ( 2 ), a fixing zone ( 4 ) in front of the distal end ( 3 ) of the electrode body ( 2 ), in which the externally closed peripheral envelope ( 8 ) of the electrode body ( 2 ) is reversibly expandable into a body lumen ( 27 ) for detachable fixing of the electrode device ( 1 ), and an expansion apparatus, situated in the fixing zone ( 4 ), for controlling the expansion and contraction in the fixing zone ( 4 ).

Description:
This application takes priority from German Patent Application DE 10 2006 011 349.7 filed 11 Mar. 2006, the specification of which is hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an implantable medical electrode device and, in particular, a cardiovascular cardiac pacemaker or defibrillator electrode device. 
     2. Description of the Related Art 
     On the background of the present invention, it is to be noted that implantable electrode devices of this type must be anchored at a specific body location, so that they do not change their position over the course of time. This is especially important when such electrode devices are implanted in a moving organ, such as the heart. 
     To fix the electrode device, implementing fixing units, such as screws, needles, hooks, anchors (tines), or projections and corresponding undercuts, into which the tissue may grow, on their elongate, tubular electrode bodies in a fixing zone before the distal end is known. 
     Fixing in a blood vessel represents a special case, since sharp tips or edges of the fixing units may cause injuries or at least irritations on the vessel wall here in particular. For this reason, typical fixing units are designed in such a way that they jam in the vessel because of their shaping. 
     In addition to the anchoring of such electrode devices, which is as atraumatic as possible, fixing in vessels of various diameters also plays a role. 
     Electrode devices implantable in vessels, which have the above-mentioned “tines”, silicone screws, or helical and/or hooked electrode bodies, are commercially available. Through pre-shaped electrode bodies of this type, for example, having bending points applied in a targeted way, the electrode body may be applied in a formfitting way to the angles and discharges of veins in the cardiovascular system, for example, and thus achieve fixing. In linear veins, positional fixing may be performed by stretching these targeted bends. Furthermore, electrodes which have an electrode body shaped as a helix on the distal end, which clamps on the vascular wall by expansion forces, are known. 
     An especially simple fixing technology, which does not achieve optimal therapeutic results, however, is wedging the distal tip of the electrode body in the vessel. The electrode body is advanced into the left-ventricular vein branch, for example, until the tip of the electrode body jams in the vein and assumes a “wedge position”. The vein is closed in this position. 
     All of the preceding anchoring technologies have various disadvantages, such as the dependence of the final position of the electrode body on the ratio the diameter of the vein to the dimensions of the tip, helix anchors, or “tines”. The final position of the electrode body thus achievable is not necessarily the most favorable therapeutic position. 
     Reference is made to, for example, WO 98/42403 A1 or U.S. Pat. No. 5,170,802 A of the published prior art. These publications disclose a fixing unit having a “stent”, which is expanded when the electrode device is located at the desired position in the vessel. The electrode body is wedged in position by the expansion of the stent structure. This solution has the disadvantage that the fixing is not reversible, which make detaching and replacing the electrode device after a first fixing, which is sometimes necessary, and also removal of the electrode device difficult. 
     A solution for the problem of repositioning is disclosed in WO 94/07564 A1, in which the fixing is performed by an expandable or self-expanding wire basket. This construction has the disadvantage that the wires cut into the vascular wall and thus may be very traumatic. 
     Finally, U.S. Pat. No. 5,411,546 A1 discloses various solutions for fixing in a vessel, for example, wire spirals which are reversibly extendable from the catheter envelope and retractable back therein. However, the fixing is not very reliable, due to the smaller diameter of the wires and the small contact area between spirals and vascular wall connected thereto, and the limited clamping force with which the spirals may press against the vascular wall, so that the latter is not damaged. The wire constructions also disclosed in the publication are—as already mentioned above—highly traumatic. Furthermore, a “sail construction” is also disclosed in this published prior art, which is again not reversible. 
     BRIEF SUMMARY OF THE INVENTION 
     Proceeding therefrom, the present invention is based on the object of providing an electrode device, which allows reliable but also reversible fixing and is comparatively atraumatic. 
     This object is achieved according to the present invention by the features of the electrode device specified in Claim  1 , according to which the electrode body is provided in the area of its fixing zone with an externally closed peripheral envelope, which is reversibly expandable for removable fixing in a body lumen, however. Expansion means are provided for controlling the expansion in the fixing zone, which may be implemented in greatly varying ways. It is to be noted on the externally closed peripheral envelope that it may be the wall of the actual electrode body of the electrode device, or also separate tubing drawn over the electrode body. 
     Because of the preceding construction of the fixing zone according to the present invention, secure, atraumatic fixing of the electrode device in a vein in the heart is possible, for example, by expanding the peripheral envelope by the expansion means (such as fluid pressure, a balloon, or axial tension/pressure on the fixing zone) at the desired position until the peripheral envelope is fixed in the vessel. It may be seen that fixing is performed independently of the diameter of the body lumen—of course, within certain boundaries. Because an externally closed envelope expands, no sharp wires, corners, or edges project into the fixing zone, so that the fixing—as provided according to the object—is performed very atraumatically. 
     Preferred embodiments of the expandable fixing zone having alternative expansion means are specified in the subclaims. To avoid repetitions, reference is made to the following description for more detailed discussion thereof, in which various exemplary embodiments of the subject matter of the present invention are explained on the basis of the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 and 2  show a longitudinal section through the fixing zone of an electrode device in the contracted and expanded states, respectively, of the fixing zone, 
         FIG. 3  shows a schematic overall view of an electrode device, 
         FIG. 4  shows a detail axial section of the electrode device in the area of the proximal pressure medium supply, 
         FIG. 5  shows a partial side view of the fixing zone of an electrode body having anchoring elements on the exterior, 
         FIG. 6 through 19  show schematic detailed longitudinal axial sections of the fixing zone of electrode devices having a folded configuration in various embodiments, 
         FIG. 20  shows a top view of a bistable tilting element for use in the fixing zone of an electrode body, 
         FIGS. 21 and 22  show schematic side views of two such tilting elements in the expanded and contracted states of the fixing zone, respectively, and 
         FIGS. 23 and 24  show detail longitudinal axial sections through the fixing zone of an electrode body which has the tilting elements from  FIGS. 20 through 22 . 
     
    
    
     DETAILED DESCRIPTION 
     As is clear from  FIGS. 1 and 2 , an implantable medical electrode device in the form of a cardiac catheter, identified as a whole by  1 , has an elongate, tubular electrode body  2 , which is provided in front of the distal end  3  ( FIG. 3 ) with a fixing zone  4 , which is a few millimeters long. The coiled electrode supply lines  6 , using which the stimulation electrodes  7  shown in  FIG. 3  are supplied with voltage, for example, run in separate internal tubing  5  in the interior of the electrode body  2 . 
     The wall  8  of the electrode body  2  is implemented as more flexible in the area of the fixing zone  4  than in the adjoining remaining areas. Furthermore, a stent-like, plastically deformable support structure  9  is embedded in the wall material therein. This support structure  9  is an essentially tubular, plastically deformable, expandable stretched metal or plastic molded part. The expansion forces of this support structure  9  are to be tailored by suitable material selection and texturing of the ribs  10 —for example, by tailoring of the rib width, rib height, the shape of the bending legs, etc.—to the elastic and geometric properties of the embedding material of the wall  8  of the fixing zone  4 , which are in turn determined by the wall thickness and the material selection, such as latex, silicone, or polyurethane. 
     As is clear from  FIG. 3 , a supply unit  12  is provided around the electrode body  2  at the proximal end  11  of the cardiac catheter  1 , via which a hydraulic pressure medium, such as physiological saline solution, may be injected into the electrode body  2 , implemented as pressure-tight tubing, at a pressure pH, using a syringe  13  via the attached feed line  14 . The proximal end  11  of the cardiac catheter  1  is formed by a terminal plug  15  for the individual stimulation electrodes  7 . 
     The supply unit  12  is illustrated in  FIG. 4 . The connection  16  of the feed line  14  is seated centrally in wall of a cylindrical sleeve  17  enclosing one of the electrode bodies  2 , between whose front openings and the electrode body  2 , O-ring seals  18  are fitted in each case. These seals are impinged by clamping sleeves  47  which may be screwed onto the cylindrical sleeve  17  for the seal, so that the pressure fluid may be injected into the annular space between the electrode body  2  and the internal tubing  5  via the connection  16  and a feed opening  19 . 
     As is clear from  FIGS. 1 and 2 , the distal end  3  of the cardiac catheter  1  is advanced in the coronary sinus until the desired position of the stimulation electrodes  7  is reached, for example. The ability to monitor this procedure using x-rays is improvable by an appropriate design of the support structure  9  from an x-ray-visible material, such as suitably coated plastic, stainless steel, platinum or titanium alloys, magnesium, or gold. 
     By impinging the fixing zone  4  using the pressure fluid as expansion means, the support structure  9  is plastically expanded there and thus stretches radially outward, as is recognizable in  FIG. 2 . This is continued until the expanded diameter of the fixing zone  4  presses against the vascular inner wall (not shown here) and thus fixes the cardiac catheter  1  in this position. 
     For repositioning or removal of the cardiac catheter  1 , the pressure fluid is suctioned off, through which a partial vacuum arises, which ensures that the fixing zone  4  contracts again and the support structure  9  more or less collapses, through which the configuration shown in  FIG. 1  is achieved again and the cardiac catheter  1  is freely displaceable. 
     The expansion diameter D in the fixing zone  4  may be directly influenced by control of the introduced volume of the pressure fluid or by the applied pressure—even in the event of pneumatic control. The pressure fluid may also be transferred into the electrode body  2  through an eccentric auxiliary lumen or external, coaxially situated tubing (not shown in detail in the figures). 
     Finally, it is to be noted that axial deformability is also achievable by suitable shaping of the embedded support structure  9 , so that the cardiac catheter  1  also remains sufficiently flexible for placement in the vessels in the area of the fixing zone  4 . 
     As is clear from  FIG. 5 , additional fixing of the cardiac catheter  1  may be achieved by suitable texturing of the external surface of the fixing zone  4 . For this purpose, in a further embodiment, rib-shaped anchoring elements  20  are applied to the exterior distributed around the circumference parallel to the longitudinal direction of the electrode body  2  in the area of the fixing zone  4 . In the unexpanded configuration, these anchoring elements  20  press flat against the exterior of the cardiac catheter  1 , so that insertion without problems is ensured. The anchoring elements  20  spread out due to the expansion of the fixing zone  4 , as shown in  FIG. 5 , and additionally mechanically impinge the inner wall of the vessel (not shown here). In particular, significantly greater withdrawal security of the cardiac catheter  1  is thus achieved. The anchoring elements  20  may be designed as soft or rigid depending on the material selection. Elastomers, other plastics, or metals come into consideration as materials. 
     The exemplary embodiments of the cardiac catheter  1  shown in  FIGS. 6 through 19  are based on a purely mechanical control principle. For this purpose, the fixing zone  4  is provided with a folded configuration identified as a whole by  21 , which acts as expansion means together with a traction or shear impingement applied coaxially to the electrode body, and is explained in the following in greater detail on the basis of the individual figures. 
     Thus,  FIG. 6  shows a reduction of the wall thickness of the electrode body  2  in the area of the fixing zone  4 . If, after positioning of the cardiac catheter  1 , a pull wire (not shown in greater detail), which is attached to the tip of the electrode body  2 , has traction applied to it in the proximal direction in relation to the electrode body  2 , the electrode body  2  bulges out in the area of the thin part of the wall and forms an annular fold  22  projecting radially outward ( FIG. 7 ). This fold is crowned in cross-section and thus atraumatic. The diameter of the annular fold  22  is expanded until the latter presses securely against a vascular wall and provides anchoring of the cardiac catheter  1 . 
     An exemplary embodiment is shown in  FIG. 8 , in which three annular folds  22  arrayed in the axial direction arise upon traction impingement of the pull wire due to three narrower thin parts of the wall arrayed in the axial direction. 
     For a corresponding design of the wall  8  in diameter and/or varying flexibility of the wall material, the annular fold  22  may also form a sawtooth profile after the expansion, as shown in  FIG. 9 . The retention force is thus greater in the withdrawal direction of the cardiac catheter  1  than in the insertion direction. 
     In the embodiment shown in  FIG. 10 , the wall  8  is designed in such a way that upon expansion with the aid of the pull wire (not shown), the annular folds  22  slide one over another, so that multiple centrally positioned internal folds  23  and multiple peripherally positioned external folds  24  arise. Therefore, the diameter expansion of the electrode body  2  is not only based solely on folding, but rather also on thickening of the material by forming multiple, preferably at least three layers. 
       FIGS. 11 and 12  shows an embodiment in which a single annular fold  22  is formed, the thick parts  25  introduced in the wall  8  sliding one over another in layers in such a way that the layers are locked. If the internal fold  23  is pushed under the external fold  24  as the folds are pushed together, the thick part  25  of the internal fold  23  snaps behind the corresponding thick part  25  of the external fold  24 , by which the configuration formed is fixed. 
     In the embodiment shown in  FIG. 13 , rib-like anchoring elements  20  are again provided around the circumference at the edge of the fixing zone  4 , which are spread out upon expansion of the annular folds  22  and additionally anchor themselves in the vascular wall.  FIG. 14  shows the corresponding area of the cardiac catheter  1  in the stretched state, in which the anchoring elements  20  press against the stretched electrode body  2 . 
     In the embodiment shown in  FIG. 15 , the electrode body  2  is designed in regard to its material selection and wall diameter in the fixing zone  4  in such a way that the flanks  26  of the annular folds  22  forming are stiffened. If the cardiac catheter  1 , as shown in this figure, is positioned in the vessel  27 , the pull wire (not shown) is actuated and the folding occurs, as shown in  FIG. 16  in an intermediate state. In this state, the vessel  27  is somewhat overexpanded. Upon further actuation of the pull wire, the annular folds  22  fold over the radially maximally expanded configuration again, so that the stiffened flanks  26  lie one on top of another and fix the cardiac catheter  1  in the vessel  27  ( FIG. 17 ). 
     In the variation shown in  FIGS. 18 and 19 , a spreading unit  28 , which supports the folding, is provided in the electrode body  2  in the area of the fixing zone  4 . This spreading unit  28  has a cone  29  fixed in the electrode body  2 , which cooperates with a spreading sleeve  31 , which is mounted distally in front of it and is impinged by the pull wire  30 . Upon impingement of the pull wire  30  in the proximal direction, the cone  29  engages under the spreading arms  32  of the spreading sleeve  31 , which thus radially expand and contribute to the formation of the annular folds  22 . The stability of the fixing may be increased by the spreading unit  28 . With an elastic embodiment of the spreading arms  32 —and also the anchoring elements  20 —the folding and opening out of the anchoring elements  20  are reversible. As already noted, the folding may be optimized both by variation of the wall thickness of the electrode body  2  in the fixing zone  4  and also by varying the degrees of hardness of the material and/or by pre-shaping using memory effect. 
     As is not shown in detail in  FIGS. 6 through 19 , the distal end of the fixing zone  4  may be connected to a pull wire or pull cable, which runs inside the electrode body  2  and is situated so it is movable in relation thereto. The proximal end of the pull wire extends beyond the proximal end of the electrode body  2 . Pulling on the pull wire or fixing the pull wire while simultaneously advancing the electrode body  2  allows the distal and the proximal ends of the fixing zone  4  to move toward one another, which causes the annular folds  22  to bulge outward, possibly with formation of the internal and external folds  23 ,  24 . It is possible to disengage the fixing of the cardiac catheter  1  thus performed by pushing on the pull wire, if it is sufficiently stiff. As an alternative, a stylet may be inserted into the electrode body  2 , using which the distal end of the flexible area may be pushed forward again. In a kinematic reversal, the pull wire having the distal end may also be used as a buttress, if the proximal end of the electrode body  2  is retracted. In any case, contraction and smoothing of the folds and stretching of the fixing zone  4  while releasing the cardiac catheter  1  will occur. 
     Finally, a further variation of the expansion and contraction of the cardiac catheter  1  in the area of its fixing zone  4  is illustrated in  FIGS. 20 through 24 . This is based on the bistable tilting element  33  shown in a top view in  FIG. 20 , which comprises two legs  34 ,  35 , each bent in an S-shape. These are laid mirror-reversed on one another and riveted to one another at the intersection points  36 . Furthermore, an anchoring element  37  in the form of a sheet metal lamella is again attached at one terminal intersection point  36 , which projects inward in the direction of the main axis connecting the intersection points  36 . The two legs  34 ,  35  form the shape of an 8 in a top view—as may be seen well in  FIG. 20 . 
     As may be seen from  FIGS. 21 and 22 , the legs  34 ,  35  are not planar in a side view, but rather are connected to one another under tension by riveting in such a way that the tilting element  33  is also bent in an S-shape along its longitudinal axis  38 .  FIG. 21  shows two such tilting elements  33  in a configuration which corresponds to the application shown in  FIGS. 23 and 24  in the expanded state. The sections of the legs  34 ,  35  supporting the anchoring elements  37  are bent convex, the remaining sections are bent concave. This is a stable final position, which may be snapped over into the second stable final position illustrated in  FIG. 22  by impinging the concave sections of the legs  34 ,  35  outward. In this position, the sections of the legs  34 ,  35  supporting the anchoring elements  37  are bent concave, while the remaining sections are now convex. Overall, the tilting element  33  may thus be snapped over between a concave-convex and a convex-concave configuration to pass between the expanded and the contracted states. 
     As shown in  FIGS. 23 and 24 , the legs  34 ,  35  of the tilting element  33  are completely embedded in the wall  8  of the electrode body  2 , so that the latter again forms an externally closed envelope. Only the anchoring elements  37  project outward from the wall  8 . 
     To implant a corresponding cardiac catheter  1 , the embedded tilting elements  33 , as shown in  FIG. 23 , are brought into the bistable final position in which the anchoring elements  37  are retracted by concave shaping of the corresponding sections of the legs  34 ,  35 . Subsequently, a deflated catheter balloon  39  is drawn through the electrode body  2  up to below this concave section and inflated as expansion means. The corresponding sections of the legs  34 ,  35  are thus arched outward, the tilting elements  33  thus jump over into the other bistable final position shown in  FIG. 24 , in which the anchoring elements  37  project outward due to the convex shape of the sections of the legs  34 ,  35  on which they are mounted and ensure reliable anchoring of the cardiac catheter  1  in the vessel (not shown). 
     To achieve this anchoring, it is sufficient to position a deflated balloon  39  between the concavely arched sections of the legs  34 ,  35  and reinflate the balloon  39 , as shown in  FIG. 23 . The tilting elements  33  thus jump back into the other bistable final position, which is shown in  FIG. 23 . The cardiac catheter  1  may then be withdrawn or repositioned without problems.