Abstract:
A high-frequency application device for vascular use, in particular for application of high-frequency (HF) energy to the renal arterial wall, including: a catheter ( 1 ) with a lumen ( 4 ) passing through it in the longitudinal direction; a self-expanding stent-like support ( 6 ) guided in the lumen ( 4 ); and an HF applicator ( 9 ) arranged on the support ( 6 ) for delivering HF energy to bodily tissue, wherein the HF applicator ( 9 ), as a multipole arrangement, has a plurality of HF contact elements ( 14 ) distributed axially and peripherally over the support ( 6 ), which are insulated from the support ( 6 ) and are connectable to an HF source ( 10 ) for simultaneous or sequential delivery of HF energy to different positions of the bodily tissue.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of priority to U.S. patent application Ser. No. 61/728,251 filed Nov. 20, 2012; the content of which is herein incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a high-frequency application device for vascular use, in particular for application of high-frequency (HF) energy to the renal arterial wall. 
       BACKGROUND 
       [0003]    Such a high-frequency application device is known as a result of prior public use and comprises a catheter with a lumen passing through it in the longitudinal direction, a self-expanding stent-like support guided in the lumen, and an HF applicator arranged on the support for delivering HF energy to bodily tissue. 
         [0004]    This known HF application device has just a single HF applicator as a single-pole ablation electrode. If, for therapeutic purposes, HF energies are to be applied in a bodily cavity or bodily vessel at a number of positions offset from one another, for example as is the case with RSD (renal sympathetic denervation) therapy, this single ablation electrode is associated with the disadvantage that the procedure has to be repeated a number of times per vessel at different positions in order to ensure the success of the therapy. Up to six repetitions per vessel are normal. Since HF energy has to be applied to each individual ablation point for up to two minutes, the intervention as a whole is very time-consuming. With the single-pole method, the ablation points cannot be positioned very precisely, since, after each application of HF energy, the catheter has to be manually displaced axially and also in a circumferential direction over a specific path. 
         [0005]    Other approaches, known as a result of prior public use, for solving the above problem are based on the use of a balloon catheter. However, this has the disadvantage that a curved artery is directed in a straight line upon balloon dilation, which is associated with the risk of rupture of the vessel. In addition, balloons of different size have to be used for different vessel diameters. 
         [0006]    Lastly, braided stent designs have the disadvantage of demonstrating a very significant change in length during their expansion. This likewise hinders accurate positioning of the ablation points. In addition, the pressure of the electrodes against the arterial wall can only be adjusted with difficulty. 
         [0007]    Proceeding from the aforementioned disadvantages of the prior art, the object of the invention is to create a high-frequency application device for vascular use, in which HF energy can be delivered simultaneously to a number of locations. 
       SUMMARY 
       [0008]    This object is achieved, in accordance with the characterizing part of claim  1 , by a high-frequency application device, in which the HF applicator, as a multipole arrangement, has a plurality of HF contact elements distributed axially and peripherally over the support. These are insulated from the support and are connectable to an HF source for simultaneous or sequential delivery of HF energy to different positions of the bodily tissue. 
         [0009]    The HF application device according to the invention thus makes it possible to deliver HF energy simultaneously to a number of positions, for example to the inner vessel wall of a renal artery. The ablation process for each artery thus takes place over just a short period of time, as would be necessary in the prior art for the application of HF energy to a single ablation point. The duration of the painful ablation procedure is thus reduced many times over. The HF contact elements can be freed in the artery due to the arrangement on a self-expanding stent-like support (for example made of shape-memory metal such as Nitinol). Once the HF energy has been delivered, the support is retracted back into the catheter, or the catheter is slid back over the support, and can thus be removed from the artery. The system is thus not only self-expanding, but can also be repositioned. 
         [0010]    Preferred developments of the high-frequency application device according to the invention are characterized in the dependent claims. The HF contact elements may thus each have a freed contact zone and at least one connecting web forming their mechanical connection to the support. As a result of this embodiment, the individual functions of the mechanical holding of the contact elements and the HF energy delivery are assigned to different components, namely the contact zone and the connecting web. These components can therefore each be tailored optimally to their task. 
         [0011]    Furthermore, the high-frequency application device can be designed in the region of each of the contact zones such that the position of these zones can be varied between a passive position resting against the unexpanded support or embedded therein and an active position protruding radially beyond the outer contour of the expanded support. The therapeutically effective contact zones thus protrude radially beyond the contour of the edge of the stent-like support structure and ensure sufficient contact with the vessel wall, even in winding passages of arteries. The contact zones are arranged at defined axial and peripheral distances from one another in this instance, whereby successful therapy is to be achieved in a reliably predictable manner. 
         [0012]    Different embodiments of the contact zones are conceivable. The contact zone may thus be designed as a closed therapeutic contact surface having a flat, paddle-like form. These contact zones are manufactured relatively easily together with the support structure in terms of the production process, for example by being cut from a tubular material. 
         [0013]    Alternatively, the contact zone may form a mechanical holder, on which a separate therapeutic contact surface is arranged. For example, this can be designed as an HF electrode head, which is arranged in a receptacle of the holder. 
         [0014]    The HF electrode head is then advantageously decoupled galvanically from the holder by local insulation, and is ideally simultaneously coupled thermally, as effectively as possible, to the metal support structure. To this end, the HF electrode can be glued to, or in, the metal support structure, for example by means of thermally conductive yet electrically insulating adhesives. It is also possible to cast the HF electrode integrally with the metal support structure using a polymer. 
         [0015]    The HF electrode head can be supplied with energy in the conventional manner via individual wires, although energy supply via a printed circuit board, which sits on the support and on which the HF electrode head is assembled, is advantageous. 
         [0016]    Individual annular surfaces for forming the therapeutic contact surfaces of the respective contact zones may also be provided on the support for the purpose of galvanic decoupling. 
         [0017]    A further alternative for the insulation of the contact zone lies in an insulation layer, for example a thin plastics layer, as a coating over the entire support or over part of the support. 
         [0018]    The contact zones can be reliably positioned in a variable manner relative to the support as a result of a further possible length-flexible design of the connecting webs of the contact elements between the respective contact zone and the support, said webs in particular extending in a meandering manner. Reliable contacting of the application device against the vessel wall can thus be assisted. 
         [0019]    Since, with HF applications in vessels, point-specific temperature monitoring of the location to which energy is applied is advantageous, one or more temperature sensors may be provided in, or on, the HF contact elements. The temperature in the vicinity of the therapeutic contact surface can thus be checked in an ongoing manner. 
         [0020]    Further preferred embodiments characterize basic structures, known per se, for the stent-like self-expanding support. This can also be designed in the manner of what is known as a slotted tube stent, also referred to hereinafter as a “slotted tube” for short. This stent structure is cut from a tube, for example by means of a laser beam, and therefore forms a closed design in contrast to a braided design. In addition, this stent structure does not demonstrate a change in length that is relevant in practice during the expansion process, whereby very accurate positioning of the ablation points in the peripheral and axial direction is made possible. Significant advantages compared to the single-pole ablation apparatus known from the prior art, which is based on a braided design of the stent, are thus achieved. The rate of success when subjecting the sympathetic nerves in the renal artery for example to sclerotherapy increases significantly compared to this braided design stent as well as single-pole application. 
         [0021]    Further advantages of the slotted tube stent compared to the braided design lie in the smaller profile expansion, since the points of intersection of the wire braid present in the braided design are omitted. Furthermore, insulation can be implemented more easily by a polymer coating after shape-setting. Insulated wires in the braided design do not allow any temperature treatment for shape-setting in the stent structure. Furthermore, as a support structure, slotted tube stents have a lower torsional rigidity than the extremely torsionally rigid braided design structures. The radial force of the HF contact elements, which for example are formed as paddle-like attachments, can also be set in an improved manner. 
         [0022]    Greater versatility of the stent design can be cited as one advantage compared to balloon technology. Curved vessels are not straightened during treatment (dilated balloon), thus reducing the risk of damage to the vessel. In addition, the blood flow through the meshes of the slotted tube stent is practically uninterrupted. 
         [0023]    An alternative for the design of the support is a type of stent graft or the combination of a plurality of a number of self-expanding annular segments, which are assembled in succession on a bearing shaft displaceable in the catheter. Both versions have advantages similar to those of the slotted tube stents detailed above. 
         [0024]    In accordance with a further development of all embodiments, variants and alternatives of the described high-frequency application device, the HF contact elements are manufactured from a material having good X-ray contrast. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0025]    Further features, details and advantages of the invention will become clear from the following description of exemplary embodiments based on the drawings, in which: 
           [0026]      FIG. 1  shows a schematic overview of a high-frequency application device, 
           [0027]      FIG. 2  shows a schematic plan view of an HF applicator having a slotted tube design, 
           [0028]      FIG. 3  shows the distal end of the HF application device according to  FIG. 1  with the HF applicator in the active position, 
           [0029]      FIG. 4  shows a schematic plan view of an HF applicator with a stent graft design, 
           [0030]      FIG. 5  a schematic view of the distal end of a high-frequency application device with an HF applicator formed of a plurality of self-expanding annular segments, 
           [0031]      FIG. 6  shows a plan view of an HF contact element in a first embodiment, 
           [0032]      FIG. 7  shows a plan view of an HF contact element in a second embodiment, 
           [0033]      FIG. 8  shows an axial section of the HF contact element along the line of section A-A according to  FIG. 6 , 
           [0034]      FIGS. 9 and 10  show an axial section of the HF contact element similar to  FIG. 8  in two further different embodiments, 
           [0035]      FIGS. 11 and 12  show plan views of an HF applicator with a support having a slotted tube design in the collapsed and expanded state, 
           [0036]      FIG. 13  shows a schematic perspective view of the HF applicator according to  FIGS. 11 and 12  in the expanded state, 
           [0037]      FIGS. 14 and 15  show plan views of an HF applicator in a further embodiment in the collapsed and expanded state, and 
           [0038]      FIG. 16  shows a plan view of an HF applicator formed as an individual segment. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    As can be seen from  FIG. 1 , a high-frequency application device for vascular use has a catheter  1  formed as an elongate tube with an outer shaft  2  and an inner shaft  3  arranged therein. An annular lumen  4  is formed between these shafts and passes through the catheter  1  in the longitudinal direction. 
         [0040]    A support  6  that is stent-like at least at the distal end  5  is arranged in this lumen  4  and is to be actuated at its proximal end  7  by a schematically indicated actuation mimic  8  in a manner that is yet to be described in greater detail. At the distal end  5  of the support  6 , an HF applicator denoted on the whole by  9  is provided, for example to apply HF energy for complete or partial transection or traumatization of sympathetic nerves at the renal artery for lasting therapy of chronic hypertension. This HF energy is not generally used to completely transect or destroy the nerve physiologically, but to make it incapable of function as a result of processes induced by the HF energy. 
         [0041]      FIG. 1  shows a purely schematic illustration of an HF source  10  for supplying energy to the HF applicator  9 , said HF source being connected to the HF applicator  9  via a suitable line  11 . 
         [0042]    A first embodiment for the HF applicator  9  is illustrated in  FIGS. 2 and 3 . The support  6  is formed in this case in the manner of a slotted tube stent, which forms a type of net structure from main meander struts  12  and longitudinal bridge struts  13 . HF contact elements  14  are distributed over the support  6  at various meander points of the main meander struts  12  and are each connectable as an electrode to the HF source  10  for the delivery of HF energy at different positions of the bodily tissue. 
         [0043]    With use of the high-frequency application device, the catheter  1  is advanced via its distal end  5  to the corresponding position within the body, together with the support  6  retracted into its lumen  4 , as indicated in  FIG. 1 . Once in this position, the outer shaft of the catheter  1  is withdrawn, so that the self-expanding support  6  expands when it exits from the lumen  4 , as shown in  FIG. 3 . 
         [0044]    The HF contact elements  14  are each formed in this case by a contact zone  15 , freed from surrounding material of the support  6  by corresponding cutouts, at a connecting web  16  carrying said contact zone for mechanical connection thereof to the support  6 . As can be seen in  FIG. 3 , the contact zones  15  of the HF contact elements  14  are displaced radially outwardly as a result of the expansion of the support  6 , such that a reliable contact between the contact zones  15  and the bodily tissue, for example of the renal artery, surrounding the HF applicator  9  is ensured. In this state, the contact zones  15  can then be supplied by the HF source  10  with corresponding HF energy, and corresponding ablations can be carried out at the contact points for therapeutic purposes. 
         [0045]      FIG. 4  illustrates an alternative embodiment for the support  6 , which in this case is designed in the manner of a stent graft. This again has main meander struts  12 , which are interconnected in the longitudinal direction by a flexible woven fabric  17  however. Similarly to the embodiment according to  FIGS. 2 and 3 , HF contact elements  14  again sit on the main meander struts  12 . 
         [0046]    In the embodiment shown in  FIG. 5 , the support  6  is formed of a plurality of self-expanding annular segments  18 ,  19 ,  20 , which are each fastened on the inner shaft  3  of the catheter  1  via sleeves  21 . Similarly to the embodiments according to  FIGS. 2 and 4 , each annular segment again has main meander struts  12  with HF contact elements  14  fitted thereon. The main meander struts  12  are in this case connected to the sleeves  21  via longitudinal coupling struts  22 . As can be seen clearly on the basis of  FIG. 5 , the annular segments  18 ,  19 ,  20  are folded together in an umbrella-like manner when the inner shaft  3  is retracted into the outer shaft  2  of the catheter  1 , whereby the stent-like annular segment structure contracts. Inversely, the annular segments  18 ,  19 ,  20  expand when the outer shaft  2  is withdrawn over the inner shaft  3 , whereby the HF contact elements  14  again contact the inner wall of the vessel. 
         [0047]    Different embodiments of the HF contact elements  14  are to be explained on the basis of  FIGS. 6 to 10 .  FIG. 6  thus shows an HF contact element  14 , of which the contact zone  15  is formed as a closed therapeutic contact surface  23  having a flat, paddle-like form. This is decoupled galvanically from the connecting webs  16 , and thus from the rest of the support  6 , in a suitable manner, for example by a thin plastics coating  24 . 
         [0048]    The variant illustrated in  FIGS. 7 and 8  shows an HF contact element  14  having a contact zone  15 , which forms an annular mechanical holder  25  in the form of an aperture  26 . An HF electrode head  27  is housed in this aperture  26  as a therapeutic contact surface  23 , which is insulated galvanically in the aperture  26  via a suitable ring insulator  28 . The electrode head  27  itself is supplied with HF energy via the above-mentioned lines  11 , as also shown in  FIG. 8 . 
         [0049]    In the embodiment illustrated in  FIG. 9 , the HF electrode head  27  likewise sits in a galvanically decoupled manner via the ring insulator  27  in the aperture  26  of the mechanical holder  25 , which is formed by the contact zone  15 , but a printed circuit board  29  is in this case provided beneath the contact zone  15 , the HF electrode head  27  being assembled on said printed circuit board and being connected accordingly to the HF source  10  via strip conductors (not illustrated in greater detail). 
         [0050]    In the embodiment according to  FIG. 10 , the HF electrode head  27  is likewise assembled on a printed circuit board  29 , wherein this sits on the mechanical holder  25  however, such that the aperture  26  can be omitted. The HF electrode head  27  is again supplied with energy via strip conductors on the printed circuit board  29 . 
         [0051]    With the HF electrode heads  27  shown in  FIGS. 7 to 10 , a temperature sensor  30  is integrated and is used to measure the temperature in the direct vicinity of the ablation location. The application of HF energy to the bodily tissue can thus be controlled in a particularly reliable manner. 
         [0052]      FIGS. 11 ,  12  and  13  show a support  6  based on a slotted tube design with lattice struts  31  arranged in a diamond-shaped manner, wherein annular surfaces  32  are formed as contact zones  15  at different points of this structure and are connected to the structure of the support  6  via meandering connecting webs  16 . 
         [0053]    As is clear from  FIGS. 12 and 13 , the meandering connecting webs  16  compensate for the expansion movement of the lattice struts  31  and ensure that the annular surfaces  32  remain far outwards in the radial direction and protrude radially beyond the contour of the support  6 . 
         [0054]    A further example of a support design with main meander struts  12 , curved longitudinal bridge struts  13  and a contact zone  15 , designed as an annular surface  32 , of the HF contact elements  14  is shown in  FIGS. 14 and 15 . The contact zones  15  are in this case connected to the main meander struts  12  via a single, narrow connecting web  16 . As can be seen from  FIG. 15 , the annular surfaces  32 , which, in the contracted position, are embedded into the structure between two curved bridge struts  13 , slide outwardly beyond the bridge struts  13  during the expansion process, whereby the contact with the surrounding tissue is again ensured. 
         [0055]    The basic designs of the support  6  shown in  FIGS. 11 to 13  and  14  and  15  are known in principle as a “closed-cell” slotted tube design (closed cell design), apart from the additions provided in accordance with the invention. 
         [0056]    Lastly, an individual segment having main meander struts  12  and longitudinally extending bridge struts  13  is illustrated in  FIG. 16 , wherein a contact zone  15  formed as an annular surface  32  is again connected between two meander curves to the main meander struts  12  via a connecting web  16 . 
         [0057]    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 teaching. 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.