Abstract:
The application relates to a shaft ( 10 ) for medical devices comprising an inner tube ( 11 ) and an outer tube ( 12 ), wherein the inner tube ( 11 ) and the outer tube ( 12 ) extend concentrically with a common longitudinal axis from a proximal end ( 15 ) to a distal end ( 16 ) of the shaft ( 10 ), and a spiral wall ( 13 ) projecting radially outwards from the inner tube ( 11 ). Further, the application relates to a catheter having such a shaft ( 10 ).

Description:
[0001]    The invention relates to a shaft for medical devices, preferably inflatable devices, and a catheter having such a shaft. 
       BACKGROUND OF THE INVENTION 
       [0002]    There are multi-lumen catheters known in the art, as for example from U.S. Pat. No. 7,022,106 B2. In these catheters, an outer lumen can be used for inflating and deflating a medical appliance, such as a balloon of a balloon catheter, or stent delivery systems. 
         [0003]    In view of the catheters known from the state of the art, there is potential for further increasing the inflation/deflation speed. 
       SUMMARY OF THE INVENTION 
       [0004]    It is an object of the present invention to provide a shaft for medical devices with improved inflation and/or deflation characteristics. 
         [0005]    This object is solved with a shaft according to the independent claim. Advantageous further developments are subject of the dependent claims. 
         [0006]    According to a first embodiment of the invention, there is provided a shaft for medical devices comprising an inner tube and an outer tube, wherein the inner tube and the outer tube extend concentrically with a common longitudinal axis from a proximal end to a distal end of the shaft, and a spiral wall projecting radially outwards from the inner tube. The advantage of the resulting spiral geometry of a lumen formed between the inner and the outer tube is to alter the flow characteristics of an inflation fluid guided through the inflation lumen. The spiral geometry reduces turbulent flow and promotes laminar flow. This way, the speed of deflation can be increased which can be advantageous in clinical applications. 
         [0007]    Moreover, it can be beneficial that the spiral wall is monolithically formed with the inner tube. This provides an efficient manufacturing and a good durability. 
         [0008]    Furthermore, the shaft can be formed such that the spiral wall is in contact with the inner tube and the outer tube. This way a tortuous curvature of the spiral wall is achieved. This can be beneficial as it ensures a more laminar flow of the inflation media and reduces the turbulent flow that might otherwise occur. Moreover, a connection between the inner and the outer tube is created, which improves the push efficiency or force transmission of the catheter system as it allows that a force applied to the outer tube by a user or physician can be transmitted to a tip of the catheter, which is attached to the inner tube, more optimally. Due to this improved transmission of force from the outer tube via the spiral wall to the inner tube and finally to the catheter tip, the maneuverability or deliverability of the catheter system in tortuous calcified anatomy can be improved. 
         [0009]    Further, it can be advantageous that the inner tube, the outer tube and the spiral wall are monolithically formed. This leads to an easier production and a better durability. 
         [0010]    According to a further development, the spiral wall has a rounded cross-section, and according to a yet further development, the spiral wall has a circular cross-section. 
         [0011]    Moreover, the shaft can be made of polymeric material. This provides a flexible, shaft. 
         [0012]    These and other embodiments are described in more detail with reference to the Figures. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0013]      FIG. 1  is a three-dimensional view of a shaft according to a first embodiment of the invention; 
           [0014]      FIG. 2  is a three-dimensional, transparent illustration of the shaft according to the first embodiment; 
           [0015]      FIG. 3  is a longitudinal sectional view of the shaft according to the first embodiment; 
           [0016]      FIG. 4  is a three-dimensional view of the shaft according to the first embodiment viewing the shaft in cross-section; 
           [0017]      FIG. 5  is a three-dimensional view of a shaft according to a second embodiment of the invention, and 
           [0018]      FIG. 6  is a longitudinal sectional view of the shaft according to the second embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]      FIGS. 1 to 4  show a shaft  10  according to a first embodiment of the invention, wherein  FIG. 1  is a three-dimensional view,  FIG. 2  is a three-dimensional, transparent illustration,  FIG. 3  is a longitudinal sectional view, and  FIG. 4  is a three-dimensional view showing the shaft  10  in cross-section. The shaft  10  comprises an inner tube  11  and an outer tube  12 , the inner tube  11  being arranged inside the outer tube  12 . The inner tube  11  and the outer tube  12  are flexible and preferably free of openings in a radial direction, respectively. The inner tube  11  and the outer tube  12  are arranged co-axially, i.e. they have a common longitudinal axis. When viewed in cross-section, a spiral wall  13  projects radially from an outer surface of the inner tube  11  to an inner surface of the outer tube  12 . In a longitudinal direction of the shaft  10 , the spiral wall  13  runs helically around the inner tube  11  with the common longitudinal axis of the tubes  11 ,  12  as center axis. Preferably, the inner tube  11 , the outer tube  12  and the spiral wall  13  are formed monolithically of polymeric material. In more detail, the shaft is produced by twisting the shaft  10  about its longitudinal axis when it is extruded. Thus, a central inner tube  11  is formed which is surrounded by a spiral shaped inflation lumen  14  which is formed between the radially outer surface of the inner tube  11  and the radially inner surface of the outer tube  12 . This inflation lumen  14  runs longitudinally through the entire length of the shaft  10 , i.e. from a proximal end  15  of the shaft  10  to a distal end  16  of the shaft  10 . The inside of the inner tube  11  is separated in a fluid-tight manner from the inflation lumen  14 . 
         [0020]      FIGS. 5 and 6  show a shaft  20  according to a second embodiment of the invention, wherein  FIG. 5  is a three-dimensional view, and  FIG. 6  is a longitudinal sectional view. The shaft  20  comprises an inner tube  21  and an outer tube  22 , the inner tube  21  being arranged inside the outer tube  22 . The inner tube  21  and the outer tube  22  are flexible and preferably free of openings in a radial direction, respectively. Preferably, the inner tube  21  and the outer tube are arranged co-axially. When viewed in cross-section, a spiral wall  23  projects radially from an outer surface of the inner tube  21  without contacting an inner surface of the outer tube  22 . Also in cross-section of the shaft  20 , the spiral wall  23  has a rounded cross-section, preferably a circular cross-section, the outer circumferences of the inner tube  21  and the spiral wall  23  overlap slightly in the area in which these elements are connected. In a longitudinal direction of the shaft  20 , the spiral wall  23  runs helically around the inner tube  21  with the common longitudinal axis of the tubes  21 ,  22  as center axis. Preferably, the inner tube  21  and the spiral wall  23  are formed monolithically. The inner tube, the outer tube  22  and the spiral wall  23  are preferably made of polymeric material. The second embodiment of the invention allows, to manufacture the inner tube  21  with the spiral wall  23  formed on it separately from the outer tube. In more detail, the inner tube  21  is produced with the spiral wall  23  formed on it by twisting or rotating the inner tube  21  about its longitudinal axis when it is extruded. The outer tube  22  can simply be extruded without twisting. Thereafter, the inner tube  21  can be inserted into the outer tube  22 . Thus, a central inner tube  21  is formed which is surrounded by a inflation lumen  24  which is formed between the radially outer surface of the inner tube  21  and the radially inner surface of the outer tube  22 , wherein the inflation lumen  24  has a spiral wall influencing the flow characteristics. This inflation lumen  24  runs in a longitudinally direction through the entire length of the shaft  20 , i.e. from a proximal end  25  of the shaft  20  to a distal end  26  of the shaft  20 . The inside of the inner tube  21  is separated in a fluid-tight manner from the inflation lumen  24 . 
         [0021]    While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive and it is not intended to limit the invention to the disclosed embodiments. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously.