Abstract:
An anti-reflux stent includes an extended inner sleeve, a stent surrounding at least a portion of the inner sleeve and a coating that bonds the stent to the inner sleeve whereby the extended inner sleeve can have a cross-sectional thickness that varies along the length of the inner sleeve. The inner sleeve is made of a material having a thickness and/or flexibility such that the distal end not surrounded by the stent collapses under gastric pressure to prevent the contents of the stomach from flowing into an esophagus. Food and liquid can pass through an inner lumen of the inner sleeve to enter a stomach when desired.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to medical devices in general, and to anti-reflux stents in particular.  
         BACKGROUND OF THE INVENTION  
         [0002]    Gastroespohageal reflux disease (GERD) is a medical condition whereby stomach acids repeatedly enter the lower portion of the esophagus because the lower esophageal sphincter (LES) at the entrance of the stomach fails to close properly. The LES may fail to close because it is diseased or has atrophied. Alternatively, patients having cancer or a tumor in the esophagus may have the LES forced open by a stent so that food and liquids can be ingested. The reflux of stomach acids into the esophagus causes severe heartburn and may contribute to the onset of other diseases.  
           [0003]    One method of relieving GERD is to place an anti-reflux stent into the entrance of the stomach. An anti-reflux stent is a device that has a one-way valve to allow food and liquid to enter the stomach but prevents liquids from passing back through the valve. Examples of anti-reflux stents can be found in J. Valbuena, “Palliation of Gastroesophageal Carcinoma with Endoscopic Insertion of a New Anti-reflux Prosthesis,” Gastrointestinal Endoscopy, Vol. 30, No. 4 pp. 241-243 (August 1994) and U.S. Pat. No. 6,302,917.  
           [0004]    A conventional anti-reflux stent has a tubular sleeve that hangs into the stomach and a stent that surrounds a portion of the sleeve to provide a lumen through which food and liquids may pass.  
           [0005]    In general it is desirable that an anti-reflux stent provide a smooth lumen opening into the stomach and an outer surface that will limit tissue growth into the stent such that it remains open and could be removed if desired. In addition, it is desirable that the valve characteristics that are provided by the sleeve can be easily selected during manufacture.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention is an anti-reflux stent that is placed into the opening of a stomach by a physician. The anti-reflux stent includes an extended inner sleeve, a stent surrounding a portion of the inner sleeve, and a coating over the stent such that the stent is bonded to the inner sleeve. The distal end of the inner sleeve is flexible such that it compresses under normal gastric pressure in the stomach to prevent stomach contents from flowing back into the esophagus. However, under increased esophageal pressure and peristaltic action, food and liquid can pass through the sleeve in its collapsed state to enter the stomach.  
           [0007]    In one embodiment of the invention, the inner sleeve has thickness and flexibility such that it inverts into the stent with sufficient gastric pressure. The proximal end of the stent may be coated to allow the stent to be removed or may be free of coating to aid in stent retention. The proximal end of the stent may be cylindrical or flared radially outward such that the stent can be embedded in or secured to an esophageal lining. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
         [0009]    [0009]FIG. 1 illustrates a conventional anti-reflux esophageal stent in place in an opening of a stomach;  
         [0010]    [0010]FIG. 2 is a cross-sectional view of an anti-reflux esophageal stent in a pressurized or closed position in accordance with one embodiment of the present invention;  
         [0011]    [0011]FIGS. 2A, 2B illustrate one technique for removing an anti-reflux stent in accordance with the present invention;  
         [0012]    [0012]FIG. 3 illustrates the proximal end of an anti-reflux esophageal stent having a flared end;  
         [0013]    [0013]FIG. 4 illustrates an anti-reflux esophageal stent having a non-coated portion;  
         [0014]    [0014]FIG. 5 is a flow chart showing a series of process steps used to make an anti-reflux esophageal stent in accordance with one embodiment of the invention;  
         [0015]    [0015]FIG. 6 is a flow chart showing a series of process steps used to make an anti-reflux esophageal stent in accordance with another embodiment of the present invention;  
         [0016]    [0016]FIG. 7 shows one embodiment of a form that creates a valve within an anti-reflux stent in accordance with another embodiment of the present invention;  
         [0017]    [0017]FIG. 8 a  shows a tube forming the basis of the stent;  
         [0018]    [0018]FIG. 8 b  shows a weave forming the basis of the stent;  
         [0019]    [0019]FIG. 8 c  shows a layer forming the basis of the stent in accordance with the invention;  
         [0020]    [0020]FIG. 8 d  is a schematic representation of the composition forming the stent in accordance with the invention comprising a tube, a weave and a coating;  
         [0021]    [0021]FIG. 9 shows a schematic cross section or end view of the stent of the invention in accordance with FIG. 8 d;    
         [0022]    [0022]FIG. 10 a  shows an embodiment in accordance with the invention of capturing free filament ends using a cover cap;  
         [0023]    [0023]FIG. 10 b  shows an additional embodiment in accordance with the invention of captured filament ends using a filament tube;  
         [0024]    [0024]FIG. 10 c  shows an embodiment having welded filament ends;  
         [0025]    [0025]FIG. 10 d  shows a folding-over of the tube to effect capture of the filament ends;  
         [0026]    [0026]FIG. 11 a  shows an application device for placing the stent in accordance with the invention;  
         [0027]    [0027]FIG. 11 b  shows an application device in accordance with FIG. 11 a  having an inserted stent and conical plug;  
         [0028]    [0028]FIG. 11 c  shows an application device having a capture and displacement device turned with respect to FIG. 11 a;    
         [0029]    [0029]FIG. 12 shows a stent having raised portions on the outer peripheral surface formed by free ends of filament pieces;  
         [0030]    [0030]FIG. 13 shows a stent having anchors introduced on the outer surface in the extended state;  
         [0031]    [0031]FIG. 14 shows a stent in accordance with FIG. 13 in an expanded state.  
         [0032]    [0032]FIG. 15 shows a stent having differing surface contours in dependence on axial and radial directions; and  
         [0033]    [0033]FIG. 16 shows a stent in an expanded state having widened lumens at each free end region. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0034]    As indicated above, the present invention is an anti-reflux esophageal stent that allows a patient to ingest food or other liquid while preventing stomach acids from flowing back into the esophagus. FIG. 1 illustrates a conventional anti-reflux stent  10  that is placed at the entrance of a stomach  12  in the area of the lower esophageal sphincter (LES)  14 . With the anti-reflux stent  10  in place, the proximal end of the stent forms a lumen into the opening of the stomach while the distal end acts to prevent the contents of the stomach  12  from entering the esophagus. The anti-reflux stent  10  comprises a flexible polymeric sleeve that collapses under the gastric pressure of the stomach  12  thereby forming a one-way valve. Food and liquid can pass in the distal direction through the collapsed sleeve but stomach acids do not flow in the proximal direction through the collapsed sleeve. However, the one-way valve can invert if the stomach pressure is sufficient to force the distal end  16  of the sleeve into the stent such as during vomiting or if the patient needs to belch. Details of the anti-reflux stent  10  are considered known to those of ordinary skill in the art and are for example disclosed in U.S. Pat. Nos. 6,302,917 and 6,162,244, which are herein incorporated by reference.  
         [0035]    [0035]FIG. 2 is a cross-section view of an anti-reflux esophageal stent in accordance with one embodiment of the present invention. The anti-reflux stent  20  has an inner sleeve  22 , a stent  24  surrounding a portion of the inner sleeve  22  at the proximal end, and a coating  26  over the stent  24  that bonds the stent  24  to the inner sleeve  22 . The inner sleeve  22  is preferably a polymeric tube that can be manufactured in a variety of manners including extrusion, molding, or forming the sleeve on a mandrel that is dipped into a polymeric solution. The materials and dimensions of the inner sleeve  22  are selected such that it will collapse in the area where it is not supported by the stent  24 . Therefore, the sleeve  22  forms a one-way valve for passage of food or liquids into the stomach of a patient. Representative materials for the inner sleeve  22  include silicone, urethane or other flexible, bio-compatible materials.  
         [0036]    In accordance with the present invention, the closure characteristics of the one-way valve can be tailored by the selection of the materials and/or dimensions of the inner sleeve. The sleeve may have different dimensions or thicknesses along its length. For example, the sleeve might be thicker in the portion that is covered by the stent and thinner at the portion that is not covered by the stent. In yet another embodiment, the inner sleeve may be made of different layers along its length by coating the inner sleeve with different materials such as silicone, polyurethane, or other surface enhancing, friction reducing or other modifying coatings. Furthermore, the sleeve could be extruded using two or more different materials in order to tailor the characteristics of the inner sleeve along its length.  
         [0037]    The stent  24  bonded to the inner sleeve  22  may be a braided or knitted stent made from a variety of materials including polyester, nylon, stainless steel, Nitinol™ brand metal alloy, Kevlar™ or other materials that provide sufficient rigidity and strength. The stent is preferably self expanding but could be expandable by a balloon or other device. Examples of particular stents that could be used in an anti-reflux stent of the present invention are set forth in U.S. Pat. Nos. 4,954,126 and 4,655,771, which are herein incorporated by reference.  
         [0038]    To bond the stent  24  to the inner sleeve  22 , a coating  26  covers the stent  24 . The coating covers the fibers that comprise the stent thereby sealing it to the inner sleeve  22 . To obtain the best possible adhesion, it is believed that the coating  26  should be made of the same material as the inner sleeve  22 . Therefore, if the inner sleeve  22  is made of a silicone material, then the coating  26  should be similarly made of a silicone material. Alternatively, if the inner tube  22  is made from a urethane material, then the coating  26  should also be made of a urethane-type material. While the use of similar materials is believed to be preferred, other materials may provide sufficient strength and bonding properties to coat the stent and adhere it to the outer surface of the inner sleeve  22 . Various thicknesses of the outer coating can be made by varying the dipping rate or building up a coating as a number of different layers.  
         [0039]    As shown in FIG. 2A, the majority of the stent  24  is covered by a coating  26 . At the proximal end of the stent are a number of bare wire or thread loops  30  that allow the anti-reflux stent to be retrieved from the patient.  
         [0040]    As shown in FIG. 2B, to retrieve the stent, a catheter  32  is inserted into the esophagus and a suture is passed through a lumen of the catheter and through a number of the loops  30  to cinch the proximal end of the stent closed. With the proximal end of the stent  24  cinched, its diameter is decreased and the endoscope and anti-reflux stent can be withdrawn from the patient&#39;s esophagus. Alternatively, the cinched anti-reflux stent may be fully or partially retracted into a retrieval tube prior to being withdrawn from the patient. The coating  26  over the stent  24  limits the ingrowth of tissue into the stent and may be lubricous to aid in its removal.  
         [0041]    In the example shown in FIG. 2, the proximal end of the stent  24  has a generally cylindrical cross-section. However the diameter of the stent may vary along its length. For example, the proximal end of the stent may be flared radially outward such as that shown in FIG. 3. The flared proximal end  40  extends radially outward and may provide additional ability to hold the stent in place within the esophagus.  
         [0042]    In yet another embodiment of the invention, the proximal end of the stent  24  does not overlap with the inner sleeve  22 . That is, the proximal end of the stent  24  comprises a length of bare mesh. If the proximal end of the stent is not coated, tissue may grow into the interstitial spaces between the fibers or wires that comprise the stent thereby acting to secure the stent within the esophagus if desired. Alternatively, the physician can put a suture or other attachment mechanisms through the exposed portion of the stent to help maintain its position within the esophagus.  
         [0043]    [0043]FIG. 5 shows a series of process steps that can be used to manufacture an anti-reflux stent in accordance with one embodiment of the invention.  
         [0044]    Beginning at a block  50 , an extrusion that forms the inner sleeve is placed over a mandrel. At a block  52 , a stent is placed over the proximal end of the extrusion. At a block  54 , a coating is formed over the stent to secure it to the extruded inner sleeve. The coating may be formed by dipping the portion of the mandrel including the stent into a 2-part silicone bath or other coating material. Alternatively, the coating may be formed by spraying it or molding it over the stent. The mandrel is then removed from the inner diameter of the inner sleeve.  
         [0045]    [0045]FIG. 6 shows an alternate series of process steps that can be used to make an anti-reflux stent in accordance with the present invention. Beginning at a block  60 , an inner sleeve is created on a mandrel by dipping it in a material such as silicone or urethane bath. With the inner sleeve created on the mandrel, a stent is placed over the proximal end of the inner sleeve at a block  62 . The exterior of the stent is then coated at a block  64  by dipping the mandrel including the stent into a material such as 2-part silicone or urethane bath. Alternatively, the coating can be applied by spraying or molding it over the stent. The mandrel is then removed from the inner sleeve.  
         [0046]    In some embodiments, it may be desirable to add one or more valves to the anti-reflux stent. FIG. 7 illustrates one method of creating a set of valves in an anti-reflux stent  70 . The anti-reflux stent has an inner sleeve  72 , a stent  74  covering a portion of the inner sleeve  72  and a coating  76  that bonds the stent  74  to the inner sleeve  72 . A set of valve flaps  78   a ,  78   b ,  78   c  can be formed in an inner lumen of the inner sleeve  72  by inserting a form  79  into the inner lumen. The form has a divider  80  that divides the area of the lumen into sections. With the form  79  in place, the anti-reflux stent is dipped into a polymeric solution and the divider  80  creates valve flaps that are bonded to the interior lumen of the inner sleeve. The one or more valve flaps created when the form  79  is removed from the stent  70  further prevent the reflux of stomach acids into the esophagus. The valve flaps can be positioned anywhere along the length of the stent but may be advantageously positioned to align with an LES when the stent is installed.  
         [0047]    [0047]FIGS. 8 a - 8   d  illustrate the construction of a stent  100  in accordance with the invention. The stent  100  consists essentially of an inner sleeve  102  (see FIG. 8 a ) made from elastic material, a tubular weave  103  tightly seating on the outer surface of the inner sleeve  102  (see FIG. 8 b ) and woven together from a plurality of filaments  105 , as well as a coating  104  (FIG. 8 c ) introduced onto the outer surface of the inner sleeve  102 . FIG. 8 d  shows the stent  100  in the constructed state. The inner sleeve  102  has a smooth inner surface and is strengthened through integration with the weaving  103  comprising the filaments  105 , wherein the tubular weaving  103  and the inner sleeve  102  are joined by means of the coating  104 . In accordance with FIG. 8 d , the coating  104  is constructed in such a fashion that the prominent structure caused by the filaments  105  on the outer surface of the tube  102  projects through the coating  104  to lead to a structured outer surface of the coating  104 .  
         [0048]    [0048]FIG. 9 shows a schematic cross-section or end view of the stent in accordance with the invention. The inner sleeve  102  as well as the weave  103 , comprising the filaments  105  and tightly seating on the outer surface of the inner sleeve  102 , are bonded together by means of the relatively thin coating  104 . In the embodiment in accordance with FIG. 9, the stent  100  has a structured outer surface dominated by the filaments  105  of rounded cross-section on the outer surface of the inner sleeve  102 . The coating  104  is thereby sufficiently thin that the spaces between the filaments  105  are not completely filled up, wherein the structure dominated by the filaments  105  at the outer surface of the inner sleeve  102  is simply covered in a sealed fashion using the coating  104 .  
         [0049]    The embodiments in accordance with FIGS. 10 a - 10   d  show different ways of holding the filament ends  109  together. In FIG. 10 a , the ends  109  of the filaments  105  are connected to each other in a protected fashion using a cover cap  106 . In accordance with FIG. 10 b , the ends  109  of the filaments  105  are each connected to each other by means of a common filament tube  107 . The free ends  109  of the filament  105  in accordance with FIG. 10 c  are held together and captured by means of a weldment  108 . In accordance with FIG. 10 d , it is also possible to capture the free ends of the filament  105  by means of a folding-over  120  of the inner sleeve  102 .  
         [0050]    [0050]FIGS. 11 a  and  11   b  show an application device  110  which is suitable for introducing the stent  100  into a body cavity. The application device  110  in accordance with FIGS. 11 a  and  11   b  consists essentially of an outer application bushing  115  as well as an inner capture and displacement device  111 . The inner capture and displacement device  111  has a spread-out capture device  112  at one end and is configured smoothly at the end opposite to the capture device  112 . In addition, the capture and displacement device  111  has a lumen  114 . In FIG. 11 a , the stent  100  is pulled into the application device  110  in the direction of arrow  121  using the spread-out end of the capture device  112 . The outer diameter of the capture and displacement device  111  is thereby dimensioned in such a fashion that it can be displaced within a lumen  113  of the application bushing  115 . In accordance with FIG. 11 c , a stent  100  which is already captured using the capture and displacement device  111  is displaced in the direction of arrow  122  out of the application bushing  115  and positioned within a body cavity.  
         [0051]    In order to utilize the application device in accordance with FIGS. 11 a ,  11   b  and  11   c , the stent is initially pulled into the application bushing  115  in accordance with FIG. 11 a  by means of the spread-out end  112  of the capture and displacement device  111 . After the stent  100  is completely within the application bushing  115  in accordance with FIG. 11 b  the stent  100  is positioned within the lumen  113  of the application bushing  115  by means of the conical plug  116 . A guided motion of the capture device  112  in the direction of arrow  121  then frees the stent  100 . The conical plug  116  is removed from the application bushing  115  and the capture and displacement device  111  is pulled out of the application bushing  115 , turned around and once more inserted into the application bushing  115  at its other end (see FIG. 11 c ). Optical observation of the placing of the stent  100  is facilitated by an instrument which can be guided through a lumen  114 . The application device  110  is subsequently placed and situated within the body cavity through displacement of the capture and displacement device  111 .  
         [0052]    [0052]FIG. 12 shows a stent  150  which is formed from a tube  151 , a weave  152  and a coating  153 . In addition to filament threads  154  from which the weave  152  is produced, a second filament thread  155  is adjacent to the threads  154  and is interrupted in sections, the free ends  156  of which protrude above the weave  152  and the coating  153 . The free ends  156  build hooks for tissue adjacent to the outer surface of the stent.  
         [0053]    [0053]FIG. 13 shows another embodiment of a stent  160 , in the elongated state, which has a weave  162 . Anchors  165  are introduced on a flat section of outer surface  164  of the stent  166 . Each anchor  165  is connected to the outer surface  164  of the stent  160  in a position-stable manner via first end  166 . A second end  167  seats on the outer surface  164  of the stent  160 . The stent  160  is elongated in the direction of arrow  168 .  
         [0054]    [0054]FIG. 14 shows the stent  160  of FIG. 13 in an expanded state. The stent  160  expands in the direction of arrow  171  so that an increased lumen  172  results. During expansion, the second ends  167  of the anchors  165  “stand up” and become separated from the outer surface  164 . The second ends  167  facilitate the hooking or digging of the anchors  165  of the stent  160  into an adjacent surface.  
         [0055]    [0055]FIG. 15 shows a stent  180  which likewise consists essentially of a tube  181 , a weave  182  and a coating  183 . The shape of the stent  180  differs in dependence on its axial and radial dimensions. The stent  180  assumes a distended shape  184  in an expanded state. The distended shape  184  is effected by weaving the weave  182  over a mould having this distended contour  184 . The shape can be arbitrary and can be adjusted to the application. The distended shape  164  shown in FIG. 11 can be fashioned in a permanent manner using thermal shaping techniques.  
         [0056]    [0056]FIG. 16 shows an additional embodiment of a stent  190 , consisting essentially of a tube  191  supporting a weave  192  covered by a coating  193 . As seen from the side, the outer shape of the stent  190  has a concave dependence  194  along its axial extent so that the stent  190  has free ends  195 ,  196  which define a wider lumen in both end regions of the stent  190 . The free ends  195 ,  196  can be reinforced by means of ring structures on the outer surface of the stent  190 . These ring structures can also be introduced on arbitrary sections of the stent at the outer surface thereof independent of the embodiment of FIG. 16.  
         [0057]    The invention concerns a stent  100  for the bracing and/or holding-open of a body cavity having a tube  102  made from an elastic material, a tubular weave  113  comprising filaments  105  seating in close adjacency to the outer surface of the inner sleeve  102  as well as a coating  104  applied to the outer surface of the inner sleeve  102  which attaches the weave  103  to the outer surface of the inner sleeve  102 . The coating  104  is adapted to have a structured outer surface dominated by the weave  103 . The stent  100  in accordance with the invention can be produced economically with adjustable restoring forces and facilitates a secure placing within a body cavity. Means for preventing drifting within the body cavity can also be introduced onto the outer surface of the stent. In each of the FIGS.  8 - 16 , an anti-reflux stent is created by lengthening the inner sleeve such that it is longer than the stent. With the sleeve sufficiently long, it will collapse in the stomach thereby forming a one-way valve to allow the passage of food and fluids into the stomach but prevent stomach acids from flowing back into the esophagus.  
         [0058]    While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.