Abstract:
An angioplasty balloon including a non-deployable stent to prevent or reduce the potential for slippage of the inflated balloon with respect to the vessel wall being treated. The balloon includes a non-deployable stent that is adapted to be secured to the balloon or angioplasty balloon catheter. The stent has a proximal end, a distal end, and at least three radially-spaced struts, each, each strut connecting the proximal end to the distal end and having one or more bends that allow expansion of the strut to accommodate the inflation of the balloon. The stem is made or a material so that the stent collapses upon deflation of the balloon.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 13/022,489, filed Feb. 7, 2011, which is a continuation of U.S. application Ser. No. 11/292,426, filed Dec. 1, 2005, now U.S. Pat. No. 7,931,663, which is a continuation of U.S. application Ser. No. 10/651,557, filed Aug. 29, 2003, now abandoned, which was a continuation-in-part of U.S. patent application Ser. No. 10/399,589, filed Apr. 18, 2003, now U.S. Pat. No. 7,691,119, which is the U.S. National Stage of PCT Application No. PCT/US02/35547, filed Nov. 6, 2002, which claimed the benefit of U.S. Provisional Application Ser. No. 60/344,982, filed on Nov. 9, 2001, the full disclosures of which are incorporated herein by reference. U.S. application Ser. No. 12/694,163, filed Jan. 26, 2010, as a continuation of U.S. application Ser. No. 10/399,589, filed Apr. 18, 2003, is also a related application. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    When a balloon used for percutaneous transluminal angioplasty (PTA) or percutaneous transluminal coronary angioplasty (PTCA) is inflated and forced into contact with the plaque, the balloon can have a tendency to move or slip longitudinally in relation to the lesion or the vessel wall being treated. 
         [0003]    Cutting balloons (atherotomy) have recently shown clinical efficacy in preventing the reoccurrence of some types of restenosis (specifically calcified lesions and instent restenosis). The cutting balloon is a coronary dilatation catheter with 3 to 4 atherotomes (microsurgical blades) bonded longitudinally on the balloon surface. As the cutting balloon is inflated, the atherotomes move radially and open the occluded artery by incising and compressing the arterial plaque in a controlled manner. An additional advantage of the cutting balloon is that it maintains its position during inflation by using the metal blades on the external surface of the balloon to penetrate into the tissue and prevent the balloon from moving. 
         [0004]    Accordingly, it is the principal objective of the present invention to provide a PTA or PTCA balloon that, like a cutting balloon, has a reduced potential of slippage when inflated in a vessel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a perspective view of an inflated angioplasty balloon incorporating a non-deployable stent according to the present invention. 
           [0006]      FIG. 2  is a plan view of the inflated angioplasty balloon and non-deployable stent of  FIG. 1 . 
           [0007]      FIG. 3  is a perspective view of the non-deployable stent in its expanded condition, as shown in  FIG. 1 , with the angioplasty balloon removed so as to more clearly show the stent. 
           [0008]      FIG. 4  is a plan view of the non-deployable stent of  FIG. 3 . 
           [0009]      FIG. 5  is a perspective view of an alternate embodiment of the non-deployable stent associated with an angioplasty balloon that has a longer working length than the angioplasty balloon shown in  FIGS. 1 and 2 . 
           [0010]      FIG. 6  is an engineering drawing showing, in plan view, the layout of a non-deployable stent adapted to be used with an angioplasty balloon of 20 mm in length. (All dimensions shown in the drawing are in inches.) 
           [0011]      FIG. 7  is a perspective view of an inflated angioplasty balloon incorporating an alternative embodiment of a non-deployable stent which does not include any connecting elements between the struts intermediate the ends of the balloon. 
           [0012]      FIG. 8  is a perspective view of the non-deployable stent shown in  FIG. 7 , with the angioplasty balloon removed so as to more clearly show the stent. 
           [0013]      FIGS. 9 and 10  are perspective views similar to  FIGS. 1 ,  5 , and  7  showing a further embodiment of the invention. 
           [0014]      FIG. 11  is a perspective view of a further embodiment of the present invention showing the balloon and non-deployable stent in conjunction with a catheter. 
           [0015]      FIG. 12  is an engineering drawing showing, in plan view, the layout of another embodiment of a non-deployable stent adapted to be used with an angioplasty balloon, in accordance with the present invention. 
           [0016]      FIG. 13  is an engineering drawing showing, in plan view, the layout of an alternate non-deployable stent of the embodiment in  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    The non-deployable stent of the present invention may be used in conjunction with a conventional balloon catheter, A PTA or PTCA catheter (dilatation catheter) may be a coaxial catheter with inner and outer members comprising a guide wire lumen and a balloon inflation lumen, respectively. Each member can have up to 3 layers and can be reinforced with braids. The proximal end of the catheter has a luer hub for connecting an inflation means, and a strain relief tube extends distally a short distance from the luer hub. The distal ends of the outer and inner members may include a taper. The catheter shaft is built using conventional materials and processes. A catheter having multi-durometer tubing with variable stiffness technology is also a possibility. The catheter should be compatible with a 6F guide catheter. Optionally, the catheter may be a multi-lumen design. 
         [0018]    The balloon  1  may be made of either nylon or nylon copolymer (compliant, non-puncture) or PET (high pressure, non-compliant) with a urethane coating to provide tackiness. The balloon may be a multi-layered balloon with a noncompliant inner layer to a most compliant outer layer. For example, an inner most layer of PET, which provides a higher pressure balloon, surrounded by an outer layer of nylon, which provides a more puncture-resistant surface. The balloon may be from 1.5-12 mm in diameter (1.5-4 mm for coronary and 4-12 mm for peripheral vessels) and 15-60 mm in length (15-40 mm for coronary and up to 60 mm for peripheral vessels). The balloon inflation pressure will be from 8-20 atmospheres, depending on the wall thickness of the balloon. When inflated, the balloon ends or necks are cone-shaped. 
         [0019]    In keeping with the invention, the balloon is provided with a Nitinol (NiTi) structure, generally designated  2 , that incorporates bends for both radial and longitudinal expansion of the Nitinol structure  2  in response to longitudinal and radial expansion of the balloon during inflation, so that the Nitinol structure  2  maintains the balloon in its intended position during inflation. This Nitinol structure  2  can be described as a non-deployable or temporary stent that provides for both controlled cracking of vessel occlusion and gripping of vessel wall during an angioplasty procedure. The Nitonol structure  2  comprises a laser cut hypo tube that expands upon inflation of the balloon, but collapses upon deflation of the balloon because of the super-elastic properties of the Nitinol material, rather than remain expanded in the deployed condition, as would stents in general. 
         [0020]    The Nitinol structure or non-deployable stent  2  has a proximal end  3 , a distal end  4 , and, therebetween, anywhere from 3-12 struts or wires  5  (depending on balloon size—but most likely 3-4 struts) with a pattern of radial and longitudinal bends. The use of laser cutting in connection with stent manufacture is well known (See, e.g., Meridan et al. U.S. Pat. No. 5,994,667), as is the use of the super-elastic nickel-titanium alloy Nitinol (see e.g., Huang et al. U.S. Pat. No. 6,312,459). 
         [0021]    As seen in  FIGS. 1-4 , each end of the four struts  5  has a sinusoidal bend  6  that allows the laser cut hypo tube to expand longitudinally when the balloon  1  is inflated. The linear length of the sinusoidal bends  6  is sized to accommodate the longitudinal expansion of the balloon  1  due to inflation. The strut or wire  5  cross sectional shape can be round, triangular or rectangular. Preferred diameter of the struts  5  ranges from 0.003 to 0.010 inch. 
         [0022]    At the longitudinal center of the hypo tube, a U-shaped circumferential connector  7  joins each strut  5  to its adjacent strut. As best seen in  FIGS. 3 and 4 , the U-shaped connectors  7  are on opposing sides of the central radial axis. The distal end  4  of the hypo tube is adhered to the distal neck of the balloon or the distal end of the catheter shaft, and the proximal end  3  of the hypo tube is either attached to the proximal neck of the balloon or to the proximal end of the catheter shaft. The struts  5  may be attached to the working region of the balloon  1  to assist the hypo tube in staying with the balloon as it inflates and deflates, and an adhesive, such as a cyanoacrylate adhesive, may be used to tack the struts down onto balloon at various points. 
         [0023]    Catheter shafts to which the balloon and laser cut hypo tube are attached can have diameters ranging from 2.5F to 8F, and the distal end may be tapered and slightly less in diameter than the proximal end. 
         [0024]    In  FIG. 6 , the dimensions of the laser cut hypo tube are for use with a 3 mm (0.118 in) diameter by 20 mm length balloon. The circumference of a 3 rom balloon is nD=3.14(3 mm) 9.42 mm or 0.37 in. As can be readily appreciated, the total length of all U-shaped connectors  7  (up and back) must be greater than the circumference of the inflated balloon  1 . The length of each U-shaped connector  7  (up and back), may be calculated using the following equation: where d is the diameter of the inflated balloon and n is the number of struts. The total length of the U-shaped bends (up and back) must exceed this length. 
         [0025]    The resulting number is divided by 2 to get the length which each up-and-back side of the U-shaped connector should exceed. For example: for a 3 mm balloon compatible, laser-cut hypo tube with four struts, the length of each U-shaped connector (up and back) is 0.37 inch divided by 4=0.0925 in. Further divide by 2 and to get 0.04625 in. This is the length that each side of the U-shaped connector must exceed. 
         [0026]    There is also one or more sets of U-shaped connectors  7  in between the sinusoidal bends  6 . The set includes one U-shaped connector for each strut (3 struts—a set of 3 U-shaped connectors; 4 struts—a set of 4 U-shaped connector; and so on). The number of U-shaped connector sets depends on the length of the balloon and thus, the length of the laser cut hypo tube. For a 20 mm length balloon, there is one set of U-shaped connectors spaced 10 mm from the end (at the halfway point along length of balloon). For a 40 mm length balloon, there are three sets of U-shaped connectors spaced in 10 mm increments (the first set is spaced 10 mm from one end; the second set is spaced 10 mm from first set; and the third set is spaced 10 mm from each the second set and the other end). The equation for number of sets of U-shaped connectors. 
         [0000]    
       
         
           
             
               L 
               10 
             
             - 
             1 
           
         
       
     
         [0000]    where L=length of balloon in mm. Other embodiments, such as those shown in  FIGS. 7 and 8 , do not incorporate the intermediate U-shaped connectors. 
         [0027]      FIG. 12  is directed to another embodiment of a non-deployable stent  102  which can be used with a conventional balloon catheter, in accordance with the present invention. The stent of this embodiment preferably has a Nitinol structure, though other materials can be used as discussed supra, that incorporates bends for both radial and longitudinal expansion of the stent in response to radial and longitudinal expansion of the balloon during inflation, so that the stent  102  maintains the balloon in its intended position. Similar to the stents of the other embodiments of the present invention discussed supra, the stent comprises a laser cut hypo tube that expands upon inflation of the balloon and collapses upon deflation of the balloon. Further, the stent is preferably secured to the balloon with some type of anchoring means. Preferably, such anchoring means are utilized at the ends of the stent and around the neck of the balloon. Examples of such anchoring means are utilized at the ends of the stent and around the neck of the balloon. Examples of such anchoring means include an adhesive such as for example a UV adhesive, cyanoacrylate, or a two-part epoxy, RF heat welding, solvent bonding, or crimping or swaging the ends of the stent to the shaft. Alternatively, a mechanical anchoring means can be used to anchor the stent to the balloon. With such a means, a small sleeve made of a similar material as the shaft of the catheter is mounted over the ends of the stent and heat welded together where the ends of the stent are sandwiched between the shaft and the sleeve. 
         [0028]      FIG. 12  shows the hypo tube of the stent in an unrolled (flat) and non-extended state. The stent  102  has a proximal end  103  and a distal end  104 . At each end, there are cage mounted flanges  110 . These flanges can be used to attach the stent to the neck of the balloon. The flanges also spring open radially to permit insertion of the balloon during assembly. Between the ends, the stent  102  includes extension sections  112 , serpentine rings  114  and elongation links  116 . 
         [0029]    Serpentine rings  114  have a serpentine shape and allow the stent  102  to expand radially when a balloon in the stent is inflated. However, as the balloon expands, the serpentine rings  114  will shorten in length. Accordingly, extension sections  112  and elongation links  116  expand longitudinally to compensate for any shortening of the length of the serpentine rings  114 . Preferably, elongation links  116  have a z-shape, s-shape or accordion shape, as shown in  FIG. 12 . 
         [0030]      FIG. 13  is an alternative embodiment showing a stent  202  having the same features as the stent in  FIG. 12  except that stent  202  in  FIG. 13  has elongated links  216  with a different pattern than the elongated links  116  in stent  102  of  FIG. 12 . More specifically, elongated links  216  have a zig zag pattern. Stent  202  of  FIG. 13  operates in a substantially similar manner to that of stent  102  in  FIG. 12 . 
         [0031]    While the present invention is not limited in the number of serpentine rings, extension sections and elongated links used in the stent,  FIG. 13  illustrates a preferred embodiment. The stent  202  in  FIG. 13  has from proximal end  103  to distal end  104 , a first extension section  112 , a first set of serpentine rings  114 , a first set of elongated links  216 , a second set of serpentine rings  114 , a second set of elongated links  216 , a third set of serpentine rings  114 , a third set of elongated links  216 , a fourth set of serpentine rings  114 , and a second extension section  112 . 
         [0032]      FIG. 13  also shows an example of possible dimensions, in inches, of each of the components of the stent  202 . These dimensions would also be used for each of the similar components in stent  102  in  FIG. 12 . 
         [0033]    It will be understood that the embodiments and examples of the present invention, which have been described, are illustrative of some of the applications of the principles of the present invention. Numerous modifications may be made by those skilled in the art without departing from the true spirit and scope of the invention.