Abstract:
A rapid exchange catheter device comprising: an elongated collapsible catheter body with a distal end and a proximal end, having a duct along a portion of the distal end of the elongated body for engagement with a guide-wire, and having a lumen extending from the proximal end towards the distal end, a portion of the lumen at the distal end substantially parallel to at least a portion of the duct; and a stiffening insert for inserting inside the lumen up to a distal end of the lumen, so as to allow advancing the catheter by advancing the stiffening insert, which pushes the distal end of the elongated body at the distal end of the lumen, dragging the rest of the catheter behind it.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to catheters. More particularly it relates to a rapid-exchange catheter with enhanced maneuverability. 
       BACKGROUND OF THE INVENTION 
       [0002]    Catheters are widely used in medical diagnostic and surgical procedures. In these procedures catheters are inserted in a target position in the patient&#39;s body, the target positions including, for example, blood vessels, atrium, ventricle, urethra, bladder, uterus, brain, and other body cavities. 
         [0003]    The deployment of a catheter is an intricate procedure, involving the initial insertion of a guide-wire into the body lumen and navigating its distal end to the target location (and even some distance further beyond), after which the catheter is engaged to the guide-wire and advanced to the target location. 
         [0004]    There are two widely used deployment methods. One is referred to as “over the wire” and the other is called “rapid-exchange”. 
         [0005]    In the “over the wire” method the catheter is mounted over the guide-wire, the guide-wire extending inside the catheter body throughout its length. As the distal end of the catheter and the distal end of the guide-wire are located inside the body, the operator advances the catheter over the guide-wire by pushing the catheter from its proximal end, which is outside the patient&#39;s body. See, for example, U.S. Pat. No. 5,357,978 (Turk). 
         [0006]    In the “rapid-exchange” (sometimes also called “monorail”) catheterization method the catheter is engaged to the guide-wire through a small conduit at its distal end, whereas most of the catheter&#39;s body lies adjacent the guide-wire (but not over it), so that the catheter can be quickly replaced with another (hence the name “rapid-exchange”). See, for example, U.S. Pat. No. 5,040,548 (Yock). 
         [0007]    Typically a catheter must be flexible enough (slack-bodied) to be able to pass in tortuous passages, yet in order to successfully advance the catheter its external walls must posses some rigidity to allow the force exerted at the proximal end to pass to the distal end. This requirement means that catheters cannot be made from pliable collapsible material, and consequently a minimal threshold rigidity level cannot be passed, furthermore, as catheters are pushed from their proximal end, it is imperative that the catheter-body possesses some rigidity or else it would have been impossible to advance a catheter forward at all. 
         [0008]    In order to overcome the problem of advancing slack bodied catheters several deployment methods and devices were introduced. 
         [0009]    U.S. Pat. No. 5,578,009 (Kraus et al.), disclosed an elongated rod, terminating in an abutment device with a lumen for passing of a guidewire, used to push an angioplasty balloon along the guidewire. 
         [0010]    In U.S. Pat. No. 6,254,610 (Darvish et al.) a device for dragging and positioning of a catheter within a duct in a body was disclosed comprising a rod whose distal end distal end is coupled to a loop, designed to be slidably mounted over a guide-wire, and provided with hooking means, onto which catheter is hooked, so that when advancing the rod from its distal end, the loop slides forward over the guidewire, and drags the catheter to its target location. In this patent the catheter is dragged from its distal end rather pushed from behind. 
         [0011]    US 2005/028870 (Chermoni) discloses a catheter with a hydraulic fluid column adapted to apply a pushing force to the front tip of the catheter. Optionally, the body of the catheter comprises two tubes, one or which extends in response to the pushing force (see also WO2005115524). 
         [0012]    It is a purpose of the present invention to provide a catheter of novel design possessing “rapid-exchange” quality and very high flexibility. 
         [0013]    Another purpose of the present invention is to provide a catheter with modifiable rigidity thus allowing the use of the same catheter is cavities of different properties and characteristics. This way the range of different uses and tasks of the same catheter are greatly expanded. 
         [0014]    Other advantages and objects will become apparent after reading the present specification and considering the accompanying figures. 
       SUMMARY OF THE INVENTION 
       [0015]    There is thus provided, in accordance with a preferred embodiment of the present invention, a rapid exchange catheter device comprising: 
         [0016]    an elongated collapsible catheter body with a distal end and a proximal end, having a duct along a portion of the distal end of the elongated body for engagement with a guide-wire, and having a lumen extending from the proximal end towards the distal end, a portion of the lumen at the distal end substantially parallel to at least a portion of the duct; and a stiffening insert for inserting inside the lumen up to a distal end of the lumen, so as to allow advancing the catheter by advancing the stiffening insert, which pushes the distal end of the elongated body at the distal end of the lumen, dragging the rest of the catheter behind it. 
         [0017]    Furthermore, in accordance with some preferred embodiments of the present invention, the stiffening insert is made from metal. 
         [0018]    Furthermore, in accordance with some preferred embodiments of the present invention, the stiffening insert is made from steel. 
         [0019]    Furthermore, in accordance with some preferred embodiments of the present invention, the stiffening insert has a varying stiffness. 
         [0020]    Furthermore, in accordance with some preferred embodiments of the present invention, the stiffening insert has a continuously varying stiffness. 
         [0021]    Furthermore, in accordance with some preferred embodiments of the present invention, the stiffening insert has a discretely varying stiffness. 
         [0022]    Furthermore, in accordance with some preferred embodiments of the present invention, the stiffening insert has a varying cross-section. 
         [0023]    Furthermore, in accordance with some preferred embodiments of the present invention, the insert has a continuously varying cross-section. 
         [0024]    Furthermore, in accordance with some preferred embodiments of the present invention, the insert has a discretely varying cross-section. 
         [0025]    Furthermore, in accordance with some preferred embodiments of the present invention, the device comprising a balloon. 
         [0026]    Furthermore, in accordance with some preferred embodiments of the present invention, the distal end of the elongated body comprises a catheter head, wherein the distal end of the lumen is fluidically connected to an annular void provided about the catheter head, a balloon wall externally covering the void. 
         [0027]    Furthermore, in accordance with some preferred embodiments of the present invention, the annular void is fluidically connected to an inner space through at least one bore. 
         [0028]    Furthermore, in accordance with some preferred embodiments of the present invention, the balloon wall is attached to the catheter head at ends under which a slit is provided, substantially parallel to the balloon wall. 
         [0029]    Furthermore, in accordance with some preferred embodiments of the present invention, a distal end of the stiffening insert is engaged at the distal end of the lumen to the distal end of the catheter. 
         [0030]    Furthermore, in accordance with some preferred embodiments of the present invention, the stiffening insert is removable from the catheter. 
         [0031]    Furthermore, in accordance with some preferred embodiments of the present invention, there is provided a method for rapid exchange catheterization comprising: 
         [0032]    providing an elongated collapsible catheter body with a distal end and a proximal end, having a duct along a portion of the distal end of the elongated body for engagement with a guide-wire, and having a lumen extending from the proximal end towards the distal end, a portion of the lumen at the distal end substantially parallel to at least a portion of the duct; and a stiffening insert for inserting inside the lumen up to a distal end of the lumen; 
         [0033]    advancing the catheter by advancing the stiffening insert, which pushes the distal end of the elongated body at the distal end of the lumen, dragging the rest of the catheter behind it. 
         [0034]    Furthermore, in accordance with some preferred embodiments of the present invention, the method further comprises removing the stiffening insert. 
         [0035]    Furthermore, in accordance with some preferred embodiments of the present invention, the method further comprises replacing the stiffening insert with a stiffening insert having a different stiffness characteristic than the stiffness characteristic of the replaced stiffening insert. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0036]    In order to better understand the present invention, and appreciate its practical applications, the following Figures are provided and referenced hereafter. It should be noted that the Figures are given as examples only and in no way limit the scope of the invention. Like components are denoted by like reference numerals. 
           [0037]      FIG. 1  illustrates a sectional view of an improved rapid-exchange catheter according to a preferred embodiment of the present invention, for angioplasty uses, inserted in a body lumen. 
           [0038]      FIG. 2   a  illustrates a sectional view of an improved rapid-exchange catheter according to another preferred embodiment of the present invention, for angioplasty uses, inserted in a body lumen. 
           [0039]      FIG. 2   b  illustrates sectioned detail of the catheter shown in  FIG. 2   a —its front (distal) end. 
           [0040]      FIG. 3   a  illustrates a general view of an improved rapid-exchange catheter according to a preferred embodiment of the present invention. 
           [0041]      FIG. 3   b  illustrates a sectional view of the catheter shown in  FIG. 3   a,  inserted in a body lumen. 
           [0042]      FIG. 3   c  illustrates the rear (proximal) end of the catheter shown in  FIG. 3   b.    
           [0043]      FIG. 4   a  illustrates a sectional view of an improved rapid-exchange catheter according to another preferred embodiment of the present invention, for angioplasty uses. 
           [0044]      FIG. 4   b  illustrates a stiffening insert with continuously varying stiffness along its body, for incorporation with an improved rapid-exchange catheter, according to a preferred embodiment of the present invention. 
           [0045]      FIG. 4   c  illustrates a stiffening insert with discretely varying stiffness along its body, for incorporation with an improved rapid-exchange catheter, according to a preferred embodiment of the present invention. 
           [0046]      FIG. 5  illustrates holding the proximal end of an improved rapid-exchange catheter according to a preferred embodiment of the present invention and advancing it. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0047]    A main concept of the present invention is the provision of an improved rapid-exchange catheter, which is advanced to its target position by way of applying a pulling force on its front distal end, instead of pushing it from behind (its proximal end). In order to facilitate this a stiffening insert is introduced into the body of the catheter, whose distal end is either engaged to or leans against a location at the distal end of the catheter and which when pushing the distal end of the catheter forward causes the body of the catheter with its entire length to be dragged behind the distal end. This eliminates the need for a stiff catheter body allowing the catheter body to be made from extremely pliable collapsible material, as there is no longer a need to transfer a pushing force exerted at the proximal end of the catheter along the catheter body all the way to its distal end in order to advance it forward. 
         [0048]    The wall of the catheter tube can be collapsible but not stretchable, as it has to transfer liquid pressure into the balloon at the catheter head. 
         [0049]    Another main aspect of the present invention stems from the understanding that in order to facilitate the existence of highly flexible catheters their deployment ought to be carried out regardless the rigidity presented by the catheter body itself, rather use an stiffening insert that is engaged to the distal end of the catheter and passes through the body of the catheter. When advancing the catheter, the stiffening insert is pushed its distal end pushing against the distal end of the catheter from within, thus effectively dragging the catheter body behind the distal end. 
         [0050]    The stiffening insert is preferably in the form of a wire insert made of a material substantially harder than the body of the catheter (typically steel, preferably steel 316, which is bio-compatible, but other materials can be used too). 
         [0051]    In some preferred embodiments of the present invention the stiffening insert is provided in several diameters in order to facilitate modifiable rigidity, but replacing one stiffening insert with another of different diameter. This is useful when the catheterization procedure is halted as a result of excessive friction, or when the operator realizes that the friction inside the body is very low. In this case the operator can replace the stiffening insert with another stiffening insert of lower rigidity (smaller diameter) in the case of excessive friction, or higher rigidity (larger diameter) in the case of very low friction. 
         [0052]    In some embodiments of the present invention the stiffening insert has varied stiffness along its length. This is to compensate for the fact that as the catheter is advanced into the body it becomes increasingly harder to advance it further due to friction exerted by the increasingly longer path it takes. In order to overcome this problem the stiffening insert is softer at its distal end and becomes increasingly harder further down its length towards the proximal end. 
         [0053]    The stiffness of the stiffening insert may vary in a continuous manner or discretely, or may be fixed along the entire body of the stiffening insert. 
         [0054]    During a angioplasty catheterization procedure, the catheter may be positioned within an occlusion, so that more force is needed to expand the volume of the balloon as the occlusion resists the expansion of the balloon. In this case the stiffening insert is withdrawn, the catheter itself remaining in position due to the friction exerted by the lumen wall on the catheter head, allowing more liquid volume to be pumped into the catheter head as a result of the free space available due to the removal of the insert. 
         [0055]    Reference is now made to the figures. 
         [0056]      FIG. 1  illustrates a sectional view of an improved rapid-exchange catheter according to. a preferred embodiment of the present invention, for angioplasty uses, inserted in a body lumen. 
         [0057]    Shown is the distal portion of the catheter, which goes into the body lumen and is aimed at being deployed at a desired target location within the lumen  2 . The catheter  10  shown is an angioplasty catheter for insertion into the vasculature and for performing dilation where an occlusion occurs and for deployment of a stent. It comprises a catheter head  12  through which a duct  13  is provided for a guide-wire  14  to pass through. As this is a rapid exchange catheter the guide-wire duct crosses the catheter head  12  but not further the length of the catheter tube  32 . Catheter tube  32  leads liquid through its lumen into the catheter head  12  into a cavity  28  inside the catheter head, which extends towards the front distal end of the head up to point  29 . Stiffening insert  30  is inserted into the catheter along its tube  32  and into cavity  28  of the head  12 , and is advanced (the arrows indicating the direction of advance) until it reaches point  29  (see also  FIG. 3   b ). From that moment any additional forward motion by the stiffening insert will result in exertion of a pushing force on the inside of distal point  29  of the catheter head  12 , which leads to the catheter head  12  being advanced forward, dragged along almost all of its entire length (apart from a small portion at the front of the catheter head which lies between point  29  and the very distal tip  15  of the head. When the catheter head has reached its final destination, stiffening insert  30  may be withdrawn leaving the catheter head in position. Alternatively the stiffening insert may remain inside. 
         [0058]    The catheter head has a novel design. External balloon wall  16 , on which stent  18  may be further provided, encloses void  20 , which extends annularly about the catheter head and which is fluidically connected through at least one bore  22  to cavity  28 . The balloon wall  16  is attached at its ends  24  to the catheter head, and small cuts  26  are provided in the catheter head, substantially parallel to the end  24  of balloon wall  16 . When liquid is forced into the catheter head the internal pressure rises causing the attached ends  24  of balloon wall  16  to rise outwardly expanding balloon wall outwardly and consequently forcing stent  18  open. 
         [0059]      FIG. 2   a  illustrates a sectional view of an improved rapid-exchange catheter according to another preferred embodiment of the present invention, for angioplasty uses, inserted in a body lumen. This is a slight modification of the catheter shown in  FIG. 1 . The catheter head  12  is provided with cap  36 , which is secured to the distal end of the catheter head  12 . A short tube  32  is provided inside duct  13  for stiffening the duct through which guide-wire  14  passes, the end of the short tube passing through cap  36 . 
         [0060]      FIG. 2   b  illustrates sectioned detail of the catheter shown in  FIG. 2   a —its front (distal) end. Cap  36  is provided with a slit  38  into which the distal end of stiffening insert  30  may be brought. In this catheter version the stiffening insert  30  reaches to the very distal end of the catheter head  12 , so practically the entire length of the catheter as well as its head are dragged behind the distal end of the stiffening insert as it is advanced forward. Slit  38  may be narrow enough to firmly hold the distal end of the stiffening insert preventing its removal, or it may be wide enough for the distal end of the stiffening insert to be inserted and removed at will. 
         [0061]      FIG. 3   a.  illustrates a general view of an improved rapid-exchange catheter according to a preferred embodiment of the present invention. Tube  32  may be separate from the catheter head and plugged into the catheter head using a female connection as shown in this figure (and in  FIG. 2   a ). Alternatively it may be plugged to the catheter head over a male connection—flange  35  (see  FIG. 1 ). 
         [0062]      FIG. 3   b  illustrates a sectional view of the catheter shown in  FIG. 3   a,  inserted in a body lumen. 
         [0063]      FIG. 3   c  illustrates the proximal end of the catheter shown in  FIG. 3   b.  The stiffening insert  30  is inserted into tube  32  of the catheter through flange  40  provided at the proximal end of the catheter tube. 
         [0064]      FIG. 4   a  illustrates a sectional view of an improved rapid-exchange catheter according to another preferred embodiment of the present invention, for angioplasty uses, in two states—deflated and inflated. Ends  25  of balloon wall  16  are attached to, the body of catheter head  12  over annular void  20 , with optional slits  27  beneath ends  25  cut into the body of catheter head  12 . When liquid is forced into cavity  28  of catheter head  12 , pressure is increased in annular void  20  causing balloon wall  16  to bulge outwardly, deploying stent  18 . 
         [0065]      FIG. 4   b  illustrates a stiffening insert with continuously varying stiffness along its body, for incorporation with an improved rapid-exchange catheter, according to a preferred embodiment of the present invention. This is achieved by varying the diameter (cross-section) of the insert continuously along its length. 
         [0066]    The varying stiffness has a significant appeal in the context of the present invention, as distal tip  56 , which travels deepest into the body lumen has nothing in front of it (no additional insert material) to push forward and on the other hand has to take up the form of any turn or bent it comes across in order to advance properly. Moreover, it has to be guided and navigated to the target location and for these ends it must be rather flexible. At point  54 , which is near the distal tip yet behind point  56  there is a need for greater rigidity, as at this point the front portion of the stiffness insert (up to tip  56 ) needs to be pushed forward. Yet greater rigidity is required at point  52  further down stiffening insert  30 , and still greater rigidity is required at proximal end  50  of the stiffening insert. As we proceed further down the stiffening insert there is less need for flexibility (for a greater portion of the insert has already advanced in front) and greater need for rigidity as more insert material has to be pushed forward. 
         [0067]      FIG. 4   c  illustrates a stiffening insert with discretely varying stiffness along its body, for incorporation with an improved rapid-exchange catheter, according to a preferred embodiment of the present invention. Here the rigidity (flexibility) of the stiffening insert varies discretely, with segments of different rigidity  59 ,  57 ,  55 ,  53 ,  51 —each segment of having a fixed diameter throughout the segment. This is achieved by varying the diameter (cross-section) of the insert discretely along its length. 
         [0068]    The stiffening insert can possess a varying stiffness not only by changing its diameter along its length. The stiffening insert may be made from materials with varying density, or from different materials placed in different parts along the length of the insert, the different materials having different stiffness characteristics. 
         [0069]      FIG. 5  illustrates holding the proximal end of an improved rapid-exchange catheter according to a preferred embodiment of the present invention and advancing it. 
         [0070]    It is evident that when the proximal portion of the catheter tube  32  is held firmly between fingers  31  of the operator and advanced into the guide catheter  60 , which is inserted in an Easy-catch™ (by Superior Healthcare Group) applicator  62 , tube wall  32 , which is collapsible, becomes wrinkled and slack, whereas stiffening insert transfers the force from the operator&#39;s hand towards the distal tip of the stiffening insert. The body of the catheter is dragged behind its distal tip. 
         [0071]    It should be clear that the description of the embodiments and attached Figures set forth in this specification serves only for a better understanding of the invention, without limiting its scope. 
         [0072]    It should also be clear that a person skilled in the art, after reading the present specification could make adjustments or amendments to the attached Figures and above described embodiments that would still be covered by the present invention.