Abstract:
The present invention relates to an adjustable length dilatation balloon catheter that includes a balloon catheter, a sheath that is slidably disposed around the balloon catheter, and an inverting tethering system that permits the selective adjustment of the exposed balloon length.

Description:
RELATED APPLICATIONS 
     The present patent document claims the benefit of the filing date under 35 U.S.C. §119(e) of Provisional U.S. Patent Application Ser. No. 61/898,307, filed Oct. 31, 2013, which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to balloon dilatation catheters and systems having an adjustable length balloon for use in percutaneous transluminal angioplasty (PTA). 
     2. Description of the Related Art 
     In certain clinical applications, there is a need to adjust the working length of a balloon in order to achieve ideal functionality. For example, when treating vascular stenoses (narrowing in blood vessel) using techniques such as PTA or venoplasty, the physician may encounter multiple stenoses of different lengths. The length of the balloon chosen for the procedure may not be appropriate for all stenoses. In these situations, using multiple balloons to dilate the stenoses may increase the complexity and cost of a procedure, as well as increase the inventory of different length balloons a hospital must have on hand. Thus, there is a need for catheter systems that permit the length of the exposed balloon to be controlled during a medical procedure. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an adjustable length dilatation balloon catheter system having a balloon catheter, a sheath, and a tethering system for adjusting the exposed balloon length through the relative movement of the balloon catheter and the sheath. 
     In a first aspect, the invention provides a catheter having a proximal end, a distal end, an inflation lumen, and an external surface. Attached to the catheter distal end is a balloon in fluid communication with the inflation lumen. Slidably disposed around the catheter and balloon is a sheath, which has a proximal end, a distal end, and interior and exterior surfaces. The distal end of the sheath has an inner surface, an outer surface, and a lip that defines a sheath distal opening. Slidably disposed on the catheter external surface is a retraction cuff that is positioned proximal to the sheath proximal end and capable of being actuated in the proximal direction along a catheter longitudinal axis. In operative connection with the distal end of the catheter is an inverting sleeve, the operative connection being to a first end of the inverting sleeve. A portion of the sleeve variably extends along the inner surface of the sheath distal end, through the sheath distal opening, over the lip of the sheath, and along the outer surface of the sheath distal end. The retraction cuff is in operative connection with the inverting sleeve at a second end of the sleeve. The retraction cuff and the operative connection with the inverting sleeve are adapted to pull the sleeve into contact with the lip of the sheath thereby applying a first pulling force on the lip in the proximal direction. Simultaneous with the first pulling force, the lip of the sheath functions as a pivot point such that the sleeve applies a second pulling force on the catheter distal end in the distal direction. 
     In a second aspect, the invention provides a method of controllably deploying a length of balloon in a balloon catheter that is surrounded by a slidable sheath, where the sheath has a distal end and the distal end has an inner surface, an outer surface, and a lip that defines a distal opening. Simultaneous application of a first pulling force on the lip of the sheath in the proximal direction and a second pulling force on the distal end of the catheter in the distal direction effects a change in the relative positions of the sheath and the balloon, thereby exposing a length of the balloon through the sheath distal opening. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary embodiment of an adjustable length balloon dilatation catheter. 
         FIG. 2  illustrates a view of the overlay of the balloon, the inverting sleeve, and the sheath. 
         FIG. 3  illustrates an exemplary embodiment of a sheath. 
         FIG. 4  illustrates an exemplary embodiment of the catheter and inverting sleeve without the sheath. 
         FIG. 5  illustrates a view of the overlay of the inverting sleeve and the balloon without the sheath. 
         FIG. 6  illustrates an alternate embodiment where the inverting sleeve is operatively connected to the catheter distal end by a second plurality of strands. 
         FIG. 7  illustrates an exemplary embodiment of an adjustable length balloon dilatation catheter with the balloon in a deployed state. 
         FIG. 8  illustrates the catheter, the balloon, and the inverting sleeve without the sheath where the balloon is in a deployed state. 
         FIG. 9  illustrates a catheter with a wireguide lumen and an inflation lumen with a balloon attached at the distal end of the catheter. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments are described with reference to the drawings in which like elements are referred to by like numerals. The relationship and functioning of the various elements of the embodiments are better understood by the following detailed description. However, the embodiments as described below are by way of example only, and the invention is not limited to the embodiments illustrated in the drawings. For example, although the drawings and descriptions illustrate over-the-wire type designs, the invention is also suitable for use with rapid-peripheral exchange systems. It should also be understood that the drawings are not to scale and in certain instances details have been omitted, which are not necessary for an understanding of the embodiments, such as conventional details of fabrication and assembly. 
     An exemplary embodiment of an adjustable length balloon catheter system is illustrated in  FIG. 1 . A sheath  30  is slidably disposed around a catheter  10 . The sheath  30  has a proximal end  32  and a distal end  34 . On the proximal end is an optional grip  70  that may be used in some circumstances for advancing or retracting the sheath relative to the internal catheter. A balloon  20  is shown partially exposed through the distal opening of the sheath. Also shown in  FIG. 1  are parts of an inverting tether system. The exemplary inverting tether system of  FIG. 1  includes an inverting sleeve  41  that is operatively connected to a first plurality of strands  42  at the second end  48  of the sleeve  41 . The strands extend in the proximal direction along the exterior of the sheath through apertures  35  in sheath  30 , along the interior of the sheath, and through or alongside the catheter toward the proximal end of the catheter. The strands  42  are connected to a retraction cuff  60  that is slidably disposed around the catheter  10  at the proximal end  12  of the catheter in a location that is proximal to the sheath proximal end  32 . Application of a pulling force on the retraction cuff  60  in the proximal direction translates the pulling force from the retraction cuff  60  through the strands  42  to the inverting sleeve  41 . As will be explained in greater detail below, pulling on the inverting sleeve  41  in the proximal direction effects a change in the relative positions of the sheath  30  and the catheter  10  thereby exposing a length of the balloon  20 . 
     In  FIG. 2  is shown a close-up of the sheath  30  with the inverting sleeve  41  on the interior of the sheath and a balloon  20  on the interior of the inverting sleeve  41 . The sheath  30  is slidably disposed around the catheter  10  with the sleeve  41  and balloon attached to the catheter distal end  14 . Thus, on the distal end of the device are three layers of materials: the sheath  30 , the inverting sleeve  41 , and the balloon  20 . 
       FIG. 3 . illustrates an exemplary embodiment of the sheath  30  in greater detail. Sheath  30  has a lip  36  at the distal end  34  that defines a sheath distal opening  38 . On the interior of the sheath at the distal end is an inner surface  31  and on the exterior is an outer surface  33 . Also shown in  FIG. 3  is an aperture  35  through which may pass a strand  42  that extends from the sleeve  41  to the proximal end of the catheter (see  FIG. 1 ). In certain embodiments, the sheath has a plurality of apertures. For example, in certain embodiments, the sheath has 2-4 apertures. In still other embodiments, the sheath has 2 apertures. 
     As shown in  FIG. 2 , in the inverting tether system of the invention the inverting sleeve  41  generally has a first end  44 , a second end  48 , and a middle portion  46 . The first end  44  is operatively connected to the catheter distal end  14  between the balloon  20  and the sheath  30 . The second end  48  is operatively connected to the retraction cuff  60  (e.g., with strands  42 ). Because the sheath  30  and the middle portion  46  of the inverting sleeve are slidable relative to each other, the middle portion  46  variably and movably extends along the inner and outer surfaces of the sheath distal end  34 , through the sheath distal opening  38 , inverting over the lip  36  of the sheath distal end  34 , and along the outer surface  33  of the sheath distal end. Depending on the state of deployment of the balloon, a greater or lesser amount of the middle portion  46  of the inverting sleeve will extend along the inner surface  31  and outer surface  33  of the sheath distal end  34 . When the balloon is in a deployed state, a greater amount of the middle portion  46  will extend along the outer surface  33  of the sheath distal end  34  than when the balloon is not deployed. Conversely, when the balloon is deployed a lesser amount of the middle portion  46  of the inverting sleeve  41  will extend along the inner surface  31  of the sheath distal end  34  than when the balloon is not deployed. 
       FIG. 4  illustrates the inverting sleeve  41  and catheter  10  in one embodiment of the inverting tether system (the sheath  30  and balloon  20  are omitted for clarity). In the embodiment in  FIG. 4 , the first end  44  of the sleeve  41  is attached to the catheter distal end  14  to form an operative connection. The configuration in  FIG. 4  shows the inverting sleeve  41  with a fold  45 , like a rolled-up sleeve. When the sheath  30  surrounds the sleeve  41 , the fold  45  is formed over the lip  36  by the middle portion  46  passing through the opening  38  and folding back over in the proximal direction. 
     In the embodiment of  FIG. 4 , the catheter  10  has a distal opening  18  that is in communication with an internal lumen  15  (i.e., a strand lumen) and a proximal opening  16 . The openings  16  and  18  and the strand lumen  15  form a channel through which may pass a strand  42  that extends from the sleeve  41  to the retraction cuff  60 . The distal opening  18  aligns with (i.e., is in communication with) the aperture  35  such that the strand  42  passes through the aperture  35  and the opening  18  and into the lumen  15 . In certain embodiments, the catheter  10  has at least one distal opening  18  and one proximal opening  16 . In other embodiments, the catheter  10  has a plurality of distal and proximal openings  18  and  16 , respectively. For example, in certain embodiments, the catheter  10  has 2-4 distal openings  18 . In still other embodiments, the catheter  10  has 2 distal openings  18 . In general, the number of distal openings  18  corresponds with the number of apertures  35 , proximal openings  16 , lumens  15 , and strands  42 . In yet other embodiments, multiple strands  42  may join into a single strand that connects to the retraction cuff  60  by passing through a single aperture  35 , distal opening  18 , internal lumen  15 , and proximal opening  16 . In preferred embodiments, the distal opening  18  has an elongated shape to accommodate movement of the catheter  10  in the distal direction while avoiding the strand  42  becoming bound in the distal opening  18 . Although an internal lumen  15  is shown in  FIG. 4 , the channel through which the strand passes may be open or partially open on the exterior of the catheter. For example, the channel may have walls and a floor formed in the side of the catheter with intervening bridging elements or a cage-type structure that restrain the strands within the channel. The catheter  10  in  FIG. 4  also has an inflation lumen  13 . Optionally, the catheter  10  includes a wire guide lumen  17  in addition to an inflation lumen  13 , one possible configuration being shown in  FIG. 9 . Also shown generally in  FIG. 9  is a wire guide  50  and a single lumen shaft  52  that allows extension of the wire guide lumen through the balloon  20 . The single lumen shaft  52  may be bonded to the distal end  14  of the catheter  10  to maintain the wire guide lumen  17  through to the distal end of the balloon. 
     In  FIG. 5  is shown the catheter  10 , the sleeve, and the balloon  20  without the surrounding sheath  30 . As can be seen in  FIG. 5 , the inverting sleeve attaches at the first end  44  to the catheter distal end  14 , and the inverting sleeve surrounds the balloon  20 . In  FIG. 5 , the inverting sleeve is shown surrounding substantially all of the balloon  20 . As the balloon  20  is deployed by application of a pulling force on the second end  48  of the inverting sleeve, more of the balloon  20  will be exposed outside the sheath  30 . 
     The inverting tether system is not limited to the embodiments explicitly shown and described herein. For example, although the inverting sleeve is shown as a continuous piece of material, the inverting sleeve may use any material that is sufficiently compliant and flexible to fold over the lip of the sheath while having the strength to exert a pulling force on the lip and the catheter distal end. Thus, the middle portion of the inverting sleeve may alternatively be a mesh material or may be an extension of the strands  42  in the distal direction to attach to the catheter distal end  14 . In certain embodiments, the first end  44 , second end  48 , and middle portion  46  of the sleeve together comprise a plurality of strands that extend from the retraction cuff  60  along the outer surface  33  of the sheath distal end  34 , over the lip  36 , along the inner surface  31  of the sheath distal end  34  and into attachment with the catheter distal end  14 . In other embodiments, the inverting sleeve  41 , including the first end  44 , second end  48 , and middle portion  46 , comprises a single continuous piece of material, such as a fabric. In certain embodiments, the first end  44  of the inverting sleeve  41  attaches directly to the catheter distal end  14  by, for example, heat bonding, adhesive, or other bonding/fastening technique/mechanism well-known in the arts. In other embodiments, a second plurality of strands  49  ( FIG. 6 ) form an operative connection between first end  44  and the catheter distal end  14 . In general, the operative connection between the first end  44  of the inverting sleeve  41  and the catheter distal end  14  may use any type of bridging or connecting material including sutures, threads, strings, wires, mesh, fabric, polymer, etc. 
     Since the inverting sleeve  41  operatively attaches to the catheter distal end  14  and folds back over the lip  36  of the sheath distal end  34 , the application of a pulling force on the sleeve  41  in the proximal direction causes the sleeve  41  to contact the lip  36  of the sheath  30  and to result in pulling forces in opposing directions on the lip  36  of the sheath  30  and the catheter distal end  14 . Pulling on the sleeve  41  produces a first pulling force that is applied to the lip  36  of the sheath  30  and a second pulling force that is applied simultaneously to the catheter distal end  14 . Holding the sheath  30  in place while pulling on the sleeve  41  produces a forward (i.e., distal) movement of the catheter  10  and balloon  20  by the force of the sleeve  41  pulling the catheter  10  out of the sheath  30 . The lip  36  of the sheath  30  acts as a pivot point whereby holding the sheath  30  in place translates the pulling force from the sheath  30  to the catheter  10 . The pulling force is maintained until a desired length of balloon  20  has been exposed for a given procedure. In an alternative method of operation, the catheter  10  may be held in place while a pulling force is applied to the sleeve  41 , thereby resulting in a proximal displacement of the sheath  30  to expose a length of balloon  20 . In either case, the exposed balloon  20  may then be inflated using known techniques to dilate a region of stenosis. 
     In operation, typically a user will hold the sheath  30  in place while pulling in the proximal direction on the retraction cuff  60 . The retraction cuff  60  is operatively connected to the inverting sleeve  41 , for example, by a first plurality of strands  42 . Thus, pulling on the retraction cuff  60  serves to produce a force that pulls the inverting sleeve  41  in the proximal direction, which in turn pulls the distal end  14  of the catheter  10  and the balloon  20  in the distal direction, thereby exposing a length of balloon  20  through the sheath distal end  34 . As explained above, the catheter  10  may alternatively be held in place while the sheath  30  is allowed to slide proximally along the catheter shaft. 
       FIG. 7  illustrates a configuration of the device after the sleeve  41  has been retracted proximally by the strands  42  and retraction cuff  60 , thereby pulling distally on the catheter  10  at the point where the first end  44  of the sleeve  41  is attached to the catheter distal end  14 . As can be seen, the pulling force on the sleeve  41  acts to expose a length of balloon  20 , which can then be inflated as shown. In  FIG. 8  is another depiction of a balloon  20  in a deployed and inflated state but where the sheath  30  and strands  42  have been omitted for clarity. 
     The balloon  20  may be resheathed by deflating the balloon and advancing the sheath  30  through the use of the grip  70  while holding the catheter  10  in place. This process advances the sheath  30  back over the inverting sleeve  41  and the deflated balloon  20 . Alternatively, the sheath  30  may be held in place while pulling on the catheter  10  in the proximal direction to pull the inverting sleeve  41  and balloon  20  back into the sheath  30 . 
     The working length of the balloon is generally at least about 2 cm, preferably about 2 cm to 8 cm. The inflated diameter of the balloon may range from about 5 mm to about 15 mm. 
     The catheter shaft, the balloon and the sheath can be formed from conventional materials such as melt processable thermoplastic polymers, e.g. polyethylene, polyethylene terephthalate, polyester-polyamide such as Hytrel® and an ionomer such as Surlyn®. The sheath can be formed in a laminate construction, e.g. where one layer of the laminate is a relatively high strength to withstand the balloon inflation pressure without significant expanding, e.g. polyethylene terephthalate or a high density polyethylene and another layer is a relatively low strength but more flexible to provide good flexibility for tracking, e.g. a polyester-polyamide such as Hytrel®, a low density polyethylene or a suitable polyurethane. Generally, the more compliant the balloon, the less strength needed in the sheath. 
     The inverting sleeve can be formed of a medical grade elastic material such as silicone, polyurethane, a copolymer of these, or other elastomeric material commonly used in interventional catheters. The inner surface of the inverting sleeve may have a somewhat tacky surface texture or property. 
     Those of skill in the art will appreciate that embodiments not expressly illustrated herein may be practiced within the scope of the present discovery, including that features described herein for different embodiments may be combined with each other and/or with currently-known or future-developed technologies while remaining within the scope of the claims presented here. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting. It is understood that the following claims, including all equivalents, are intended to define the spirit and scope of this discovery. Furthermore, the advantages described above are not necessarily the only advantages of the discovery, and it is not necessarily expected that all of the described advantages will be achieved with every embodiment of the discovery.