Abstract:
A medical balloon is collapsed to a small profile during deflation by preventing tension in the catheter or balloon which might otherwise direct the balloon into a larger diameter collapsed profile, making it difficult to remove the catheter from the body. Tension may be avoided by arranging at least one end of the balloon to slide with respect to the catheter body. The invention is particularly applicable to a relatively stiff, inelastic balloon that is preformed into a geometric cross-sectional shape with corners, such as a square balloon, for encouraging a particular collapsed configuration, e.g., three or more folded lobes.

Description:
This is a continuation of U.S. Ser. No. 09/318,284, filed May 25, 1999 and issued as U.S. Pat. No. 6,135,982, which is a continuation of U.S. Ser. No. 08/943,904, filed Oct. 3, 1997 now U.S. Pat. No. 5,928,193—for updating the status of the priority documents. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to balloon catheterization. 
     BACKGROUND OF THE INVENTION 
     A balloon catheter is a device with an elongated shaft that carries an inflatable balloon. Typically, the shaft is delivered into a narrow body lumen with the balloon in a low profile deflated state. When the treatment site is reached, the balloon is inflated to its full diameter. After treatment is complete, the balloon is again deflated, hopefully to a small diameter profile, and the catheter is removed from the body. Inflation of the balloon may be effective to, for example, dilate the lumen, deliver a stent to the site, block the lumen, at least temporarily, stabilize the catheter, or deliver drugs to the lumen walls. 
     SUMMARY OF THE INVENTION 
     The invention relates to collapsing a balloon to a small profile during deflation by preventing tension in the catheter or balloon which might otherwise direct the balloon into a larger diameter collapsed profile, making it difficult to remove the catheter from the body. Tension in the catheter may be avoided by arranging at least one end of the balloon to slide with respect to the catheter. The invention is applicable to, for example, a relatively stiff, inelastic balloon that is preformed into a geometric cross-sectional shape with corners, such as a square balloon, for encouraging a particular collapsed configuration, e.g., three or more folded lobes. 
     In a first aspect, the invention features a balloon catheter with a flexible catheter body portion extending longitudinally, a spanning portion, and a tip region. The tip region is axially displacable with respect to the spanning portion between a retracted condition and an extended condition without biasing the spanning portion and tip region. The catheter also includes an inflatable balloon having a working portion and proximal and distal end portions. The proximal end portion is attached to the catheter body and the distal end portion is attached to the tip region. The working portion is preconditioned to form at least three lobes. 
     In another aspect, the invention features a balloon catheter with a flexible catheter body portion extending longitudinally from a region remaining outside the body to an end region positioned inside the body, a spanning portion extending through the flexible body portion from the region remaining outside the body and beyond the end region, and a tip region in sliding telescoping relationship with the spanning region between a retracted condition and an extended condition. An inflatable balloon is provided having a proximal and distal end portion. The distal end portion is attached to the tip region. 
     In another aspect, the invention features a method, including delivering a balloon catheter into the body, the balloon catheter including a catheter body extending longitudinally, a tip region, and an inflatable balloon. The balloon has proximal and distal end portions. The proximal end portion is attached to the flexible catheter body portion and the distal end portion is attached to the tip region. The method also includes inflating the balloon, during which the tip region is axially displaced with respect to the catheter body to a retracted condition without biasing the flexible catheter body and tip region. 
     Embodiments may include one or more of the following. The spanning portion is axially fixed relative to the catheter body portion. The tip region is an element concentrically arranged with respect to the spanning portion. The tip region includes a tubular element concentrically about the spanning portion. The tip is axially slidable relative to the spanning portion. The tip is arranged concentrically over a distal portion of the spanning portion. The spanning portion is a solid wire-member. The spanning portion is fixed to the flexible body portion. The spanning portion is a tubular member. 
     Embodiments may also include one or more of the following. The catheter body and tip region include lumens arranged to pass a guidewire through the balloon and beyond the tip member. The catheter spanning portion includes a lumen for passage of the guidewire. The tip region is articulated by a collapsible region. The tip region is in telescoping relationship. 
     Embodiments may also include one or more of the following. A strand element is attached between the catheter and the tip region. The strand element is in a slack condition, free of substantial bias when the tip region is in the retracted condition or extended condition. The tip member and catheter body have complementary mating structure. The tip member and catheter body have bayonet fitting structure. The catheter body has a spanning portion, spanning the interior of the balloon, the spanning portion being a continuous extension of the flexible catheter body portion. The catheter body, spanning portion, and tip-region include lumens for passage of the guidewire. The balloon is made of a substantially inelastic material. The balloon is made of PET. The balloon is inflated to open an obstructed lumen. The catheter is placed over a guidewire. 
     Implementations of the invention may have certain advantages. For example, reliable collapse of the balloon to small diameter makes it easier to withdraw the catheter from the body, particularly in cases where the catheter is drawn into another catheter, such as an introducer catheter or an endoscope. 
     Still further aspects, features, and advantages follow. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     We first briefly describe the drawings. 
    
    
     DRAWINGS 
     FIG. 1 is a cross-sectional side view of a balloon catheter with the balloon in the initial deflated condition as the catheter is delivered to a site where dilatation is to take place and FIG. 1 a  is an end-on cross-sectional view through the balloon and catheter 
     FIGS. 2 and 2 a  are views similar to FIGS. 1 and 1 a  with the balloon inflated and dilating the lumen; 
     FIGS. 3 and 3 a  are views similar to FIGS. 1 and 1 a  with the balloon partially deflated after dilatation; 
     FIGS. 4 and 4 a  are views similar to FIGS. 1 and 1 a  with the balloon fully deflated after dilatation; 
     FIGS. 5 and 5 a  are cross-sectional side views of the catheter with the balloon removed and a slidable tip in retracted and extended conditions; 
     FIG. 6 is a perspective view of the tip assembly; 
     FIG. 7 is a side view of another balloon catheter during delivery to a treatment site; 
     FIG. 8 is a cross-sectional side view of the catheter in FIG. 7; 
     FIG. 9 is an exploded view of another catheter; 
     FIG. 10 is a side view of another catheter; 
     FIG. 11 is a cross-sectional side view of another catheter. 
    
    
     STRUCTURE AND OPERATION 
     Referring to FIGS. 1-6, a balloon catheter  2  may be delivered into a body lumen  4 , such as the esophagus, for dilating a lesion  6 . The catheter  2  is delivered through an endoscope  8  which extends from a coupling part  10 , remaining outside the body, to an end positioned close to the lesion. The catheter  2  has a catheter body  12  including a flexible portion  14  which extends most of its length from a coupling  16 . The catheter also has a spanning portion  18  which extends through the balloon  20 . The catheter also includes a tip  22 . 
     The balloon  20  includes proximal and distal end portions  24 ,  26  and a working portion  28 . The proximal and distal end portions  24 ,  26  are attached to the catheter body and the tip  22 . The tip  22  can slide axially with respect to the spanning portion  18  which prevents bias, i.e., tension or compression in the catheter or balloon as the balloon is inflated and deflated, particularly with a balloon that has been preformed with corners to preferentially collapse to a particular shape. 
     Referring particularly to FIGS. 1 and 1 a , during delivery to the treatment site, the balloon is deflated and in an initial collapsed condition in which it is tightly wrapped about the catheter in a series of overlapping wings or lobes  30 , preferably three or more. In this condition, the tip  22 , while movable axially, does not slide substantially due to the resistance of the mass of the tightly wrapped balloon. The balloon in this small diameter form can be passed through the endoscope  8  and threaded to the dilatation site. 
     Referring particularly to FIGS. 2 and 2 a , for dilating the site, the balloon is inflated so that the working portion  28  presses against the lumen wall, including the lesion  6  forcing, the passageway open. During inflation, the lobes  30  of the folded balloon unfold and at full inflation the working portion of the balloon has a generally circular cross section as shown in FIG. 2 a . Inflation may be achieved by an inflation/deflation controller  32 , such as a syringe or other device which directs inflation fluid through the catheter body into the balloon. At full inflation, the ends  24 ,  26  of the balloon may be drawn together. With the end  26  attached to the tip  22 , any compression biasing that might otherwise be placed on the catheter body, spanning member or tip  22  is avoided as the tip  22  slides (arrow  34 ) proximally over the spanning member  18 . 
     Referring to FIGS. 3 and 3 a , after dilatation, the balloon is deflated by withdrawing fluid within the balloon and through the catheter body using controller  32 . As the balloon deflates, the ends may be pushed apart. Any tension biasing in the catheter body, spanning portion or tip is avoided as the tip  22  slides (arrow  36 ) distally under the force of the collapsing mass of balloon material. In the intermediate stage of deflation, the balloon has a geometric shape with a series of corners  38  which assist further collapse of the balloon into a small profile. Avoiding tension in the catheter prevents forces from acting on the balloon which might disturb the collapse intended by the corners  38 . 
     Referring to FIGS. 4 and 4 a , further deflation of the balloon is achieved by creating a vacuum within the balloon again using controller  32 . The tip  22  may continue axial movement as deflation continues (arrow  40 ). The profile of the balloon in the fully collapsed condition is a series of four lobes  42  in which the balloon has a sufficiently small diameter to be withdrawn through the endoscope  8 . 
     Referring to FIGS. 5-6, more detailed views of the catheter are provided. The flexible body portion  14  includes a flexible tubular sheath  44  and a core wire  46 . The flexible sheath  44  terminates at an annular coupling  48 . The core wire  46  is fixed to the coupling and extends beyond it, forming the spanning region  18  and terminating at an end region  50 . The tip region  22  includes a polymeric tip member  52  which includes a lumen area with a hypotube  54  sized to slidably receive the end region  50  of the spanning portion  18 . For safety, the tip region  22  is connected to the core wire by a series of wires  56 . One end  58  of each is attached to the hypotube  54  and the other end  60  is attached to the spanning portion  18 . As the tip region  22  slides proximally (arrow  62 ), the wires are in a slack condition. As the tip  22  slides distally (arrow  64 ), the wires  56  take up the slack but without creating tension. 
     In a particular embodiment, the catheter is designed for use in the esophagus. The catheter has an overall length of about 180 cm. The flexible body is formed of nylon and has outer diameter of about 0.078 inch, an inner diameter of about 0.061 inch, and length of about 170 cm. A metal tube, about 0.20 inch long with an inner diameter of about 0.052 inch, and a wall thickness of about 0.005 inch, is embedded in the distal end of the flexible body for attachment of the core wire. The core wire, made of stainless steel, has a diameter of about 0.023 inch and a length of about 180 cm, extending beyond the flexible shaft about 10 cm. The core wire is attached to the tube by welding. The core wire extends proximally through the catheter to the coupling where it is attached. The core wire enhances the pushability of the catheter, making it easier to urge it through the endoscope and body lumen without collapsing or buckling. The tip is made of PEBAX 3535 (Atochem, Philadelphia, Pa.) and has a outer diameter of about 0.075 inch, a wall thickness of about 0.022 inch, and a length of about 1 inch. The tip hypotube has an inner diameter of about 0.035 inch, a wall thickness of about 0.009 inch, and a length of about 0.75 inch. The hypotube is overmolded to the tip by injection molding. The flexible wires are made of stainless steel, have a diameter of about 0.005 inch and extend from the tip about 0.875 inch. They are attached to the tip tube and core wire by welding. Alternatively, the wires may be polymeric such as Kevlar or Vectron, in which case they are attached to the catheter by adhesive. The free sliding play of the tip on the core wire is about 0.750 inch. The balloon has a square shape and is made of PET. Balloon of this type are discussed in Campbell et al. U.S. Pat. No. 5,456,666, the entire contents of which is incorporated by reference. In embodiments, the balloon may be made of other materials such as compliant or semicompliant polymers. An example is a balloon made of PBT elastomer, such as Arnitel (polybutadieneterephthalate, available from PSM, the Netherlands). 
     Referring to FIGS. 7 and 8, in another embodiment, a catheter  80  is arranged for delivery into the body over an axially moveable guidewire  82 . The guidewire  82  may be delivered into the lumen and then the catheter  80  slid over the guidewire  82 . Referring particularly to FIG. 8, the catheter  80  includes a flexible polymeric catheter body  84  and a tube member  86  which extends through the body  84  and forms a spanning region  88 . The tube member  86  terminates in an end opening  90 . The catheter also includes a tip  92  with an outer polymeric body  94  and an inner tube member  86 . The spanning tube  88  terminates within the inner tube  96  of the tip  92 . The inner tube  96  includes an end opening  98 . The catheter therefore provides a passageway from the catheter body, through the balloon and end of the tip region  92 . The passage may extend proximally to the proximal end of the catheter outside the body and/or the guidewire may emerge from the catheter just proximal of the balloon for rapid exchange. 
     Referring to FIG. 9, in another embodiment, a catheter  110  includes a flexible polymeric tube  112 , a core wire  114 , and a slidable tip  116 . The core wire  114  includes a nub  118  which can be engaged with a bayonet fitting  120  on the tip  116 . The bayonet fitting includes a slot  122 , permitting axial sliding motion of the tip  116  with respect to the catheter while preventing rotational motion about the catheter axis. 
     Referring to FIG. 10, a catheter  130  includes a flexible tubular body  132  and a core wire  134 . The core wire extends to a bellows  136  which is attached to a tip region  138 . The tip region  138  may be a segment of core wire material or it may be another material, such as a soft polymer. The bellows  136  permits axial motion of the tip  138  relative to the catheter body. The bellows may be manufactured of, for example, a highly flexible stainless steel or a superelastic material such as nitinol. In another embodiment, the bellows is replaced by a hinge arrangement. For example, a pair of radially opposed hinges may be provided with the arms of the hinges being attached to the core wire and the tip. 
     Referring to FIG. 11, a catheter  150  includes a continuous polymeric body  152  including a proximal region  154  and a spanning region  156 . The catheter  150  also includes a tip member  158  which is slidably disposed over the distal portion of the spanning region  156 . The catheter has a pair of lumens  160 ,  162 . The lumen  160  is used for introducing inflation fluid to the balloon. The lumen  162  is for passing a guidewire. The lumen  162  terminates in a end opening  164  at the end of the spanning region  156 . The slidable tip  158  includes an axially aligned end opening  166  for through passage of the guidewire from the distal end of the catheter. 
     Still further embodiments are within the following claims.