Abstract:
The present invention describes an inflatable intraluminal vascular stent which incorporates fine conduits of synthetic material in a meshwork like structure forming a tubular vascular prosthesis. The conduits provide for inflating and deflating the meshwork structure to deploy the stent, adjust its supporting force and for repositioning or removing the stent, if needed. Accordingly, the present invention includes a method for repairing a treatment zone in a vasculature and the like by positioning the inflatable intraluminal vascular stent bridging the treatment zone. Following insertion of the stent into the vasculature spanning the treatment zone, the meshwork structure is inflated to expand the stent against the vasculature wall. Importantly, the inflation pressure is controllable to regulate the supporting force of the stent as it conforms to the shape of the vasculature.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority based on provisional application Ser. No. 60/152,094, filed Sep. 2, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to the treatment of arterial disease including, for example, an abdominal aortic aneurism or occlusive disease of an artery. More particularly, the present invention relates to an improved method for treating arterial disease using a novel intraluminal vascular stent formed of a meshwork of inflatable conduits. This construction provides for readily deploying the stent and for repositioning it should the stent not be initially deployed in the most optimum position in the vasculature. 
     2. Prior Art 
     The prior art describes the treatment of arterial disease by various surgical techniques, some involving the use of stents and grafts. For example, it is well known to interpose a stent within a diseased portion of the human vasculature to prop open and support the vasculature and provide unhindered fluid flow there through. Conventional stents are made of stainless steel wire, Nitinol wire and the like constructed in a meshwork form. Such stents are balloon or self-expandable inside an arterial lumen to provide for supporting and strengthening the walls of a stenotic or occluded artery. Similarly, it is well known in the prior art to use a graft in conjunction with a stent to repair damaged portions of the aorta or other arteries. Grafts, comprised of hollow tubes of prosthetic material such as Dacron, are normally inserted within the walls of a damaged artery and can be deployed into position through the use of a stented balloon catheter, thereby ensuring blood flow and reducing the risk of an aneurysm rupturing. 
     One of the problems with current stent designs is that it is difficult to control the supporting force which they exert against the vasculature side wall. Although the inflation pressure of the balloon catheter can be controlled, once the balloon is deflated and removed leaving the deployed stent in place, the force of the stent supporting the vasculature wall can change over time. Eventually, it is possible that a conventional wire mesh stent could become fatigued and bend and fracture to the extent that the supporting force it exerts is less than desirable to maintain open and unhindered flow through the vasculature. Conventional practice is to re-enter the treatment zone with a balloon catheter which is moved inside the relaxed stent and inflated to re-position the stent against the vasculature side wall. If the stent has relaxed to the point that it no longer sufficiently supports the vasculature wall, it must be removed and replaced. 
     U.S. Pat. Nos. 4,183,102 to Guiset and 5,370,691 to Samson describe inflatable devices for supporting the vasculature. However these devices do not provide a meshwork of intersecting conduits as in the present invention. Guiset disclosed a plurality of hollow toroidal sleeves while Samson relates to a helically wound polymeric tubing. These devices do not provide for lateral flow at the junction of two arteries, for example. 
     The present invention solves the drawbacks of the prior art by providing a novel inflatable intraluminal vascular stent or stented graft and method for treating vasculature diseases. The inflatable characteristic of the present stent means that the supporting force exerted by the stent will not change. Also, the present inflatable stent is selectively deflatable for repositioning should it later be determined that the stent is not positioned in the most desirable location within the vasculature. 
     SUMMARY OF THE INVENTION 
     The present inflatable intraluminal vascular stent incorporates fine conduits of synthetic material in a meshwork like structure forming a tubular vascular prosthesis. The conduits provide for inflating and deflating the meshwork structure to deploy the stent, adjust its force and for repositioning or removing the stent, if needed. Accordingly, the present invention includes a method for repairing a treatment zone in a vasculature and the like by positioning the inflatable intraluminal vascular stent bridging the treatment zone. Following insertion of the stent into the vasculature spanning the treatment zone, the meshwork structure is inflated to expand the stent against the vasculature wall. Importantly, the inflation pressure is controllable to regulate the supporting force of the stent as it conforms to the shape of the vasculature. 
     These and other aspects and advantages of the present invention will become increasingly more apparent to those skilled in the art by reference to the following description and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a perspective view of one embodiment of an inflatable intraluminal vascular stent  10  according to the present invention in a deflated condition. 
     FIG. 1B is a perspective view of the stent  10  shown in FIG. 1A in an inflated condition. 
     FIG. 2A is a perspective view of a second embodiment of an inflatable intraluminal vascular stent  50  according to the present invention in a deflated condition. 
     FIG. 2B is a perspective view of the stent  50  shown in FIG. 2A in an inflated condition. 
     FIG. 3 is a partial cross-sectional view of the fill port  28  for the stent  10 ,  50  and the mating fitting  84  for the inflation conduit  72 . 
     FIG. 4 is a perspective view of a release plunger  116  for opening the fill port  28  and a pump  122  for inflating the stent. 
     FIG. 5 is a perspective view of the stent of FIGS. 2A and 2B secured to a graft  132  according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning now to the drawings, FIGS. 1A and 1B illustrate one exemplary embodiment of an inflatable intraluminal vascular stent  10  comprising a tubular shaped prosthesis  12  for a body passageway and FIGS. 2A and 2B show another embodiment of an inflatable intraluminal vascular stent  50  comprising a tubular shaped prosthesis  52 , both according to the present invention. It should be understood that the terms “inflatable intraluminal vascular stent” and “inflatable prosthesis” are interchangeably used to some extent in describing the present invention, insofar as the methods, apparatus, and structures of the present invention may be utilized not only in connection with an inflatable intraluminal vascular stent for expanding partially occluded segments of a blood vessel or a body passageway, but may also be utilized as an inflatable prosthesis for many other types of body passageways. For example, the inflatable prostheses  12 ,  52  may also be used for such purposes as: (1) supportive stent placement within blocked arteries opened by transluminal recanalization, but which are likely to collapse in the absence of an internal support; (2) similar use following catheter passage through mediastinal and other veins occluded by inoperable cancers; (3) reinforcement of catheter created intrahepatic communications between portal and hepatic veins in patients suffering from portal hypertension; (4) supportive stent placement of narrowing of the esophagus, the intestine, the ureters, the urethra; and (5) supportive stent reinforcement of reopened and previously obstructed bile ducts. Accordingly, the term “intraluminal vascular stent” encompasses use for expanding the lumen of a body passageway and the term “body passageway” encompasses any duct within the human body, such as those previously described, as well as any vein, artery, or blood vessel within the human vasculature. 
     FIGS. 1A and 1B show one embodiment of a stent  10  according to the present invention as a tubular shaped prosthesis  12  including first and second ends  14  and  16  and an outer wall surface  18  disposed between the ends. Preferably, the wall surface  18  is formed by a plurality of intersecting elongate members  20  and  22  of a conduit-shaped synthetic material. In that respect and with reference to the orientation of FIGS. 1A and 1B, the prosthesis  12  comprises the plurality of parallel elongate members  20  disposed in an orientation running generally south-west to north-east from the first end  14  to the second end  16  of the stent  10 , and the plurality of parallel elongate members  22  disposed in an orientation running generally south-east to north-west from the first end  14  to the second end  16  of the stent  10 . 
     In the deflated condition, the conduit-shaped elongate members  20  and  22  intersect with one another at acute angles designated  24  in FIG. 1A, intermediate the first and second ends  14  and  16 . This intersecting construction is shown, for example, at junctions  26 . In an alternate embodiment of the present invention, the plurality of elongate members  20  and  22  do not necessarily have fluid flow communication with one another at each of their intersections  26 . Instead, the outer surface of each of them are fixedly secured to one another at their intersections by ultrasonic welding, gluing and the like. What is important is that each of the plurality of elongate members  20  and  22  have fluid flow communication from a fill port  28 , which is shown in FIG.  3  and will be described in greater detail hereinafter. 
     FIGS. 1A and 1B also show an optical radiopaque marker  30  secured to the stent  10 . The radiopaque marker  30  is optional, but is necessary to determine the position of the stent in the vasculature during deployment. The marker  30  may be any suitable radiopqaue material, preferably metal. Materials such as the platinum series of metals (platinum, palladium, etc.) and gold, silver, and tantalum may be used as the marker  30 . Certain stainless steels are also suitable for use as the marker. It should also be understood that the marker  30  can have various shapes and sizes and should not be limited to that shown. 
     Also shown in FIG. 1A, the tubular shaped prosthesis  12  has a first diameter, d, which permits intraluminal delivery of the prosthesis  12  into a body passage (not shown). With reference to FIG. 1B, upon the application of an inflating force to the conduit construction of the intersecting elongate members  20  and  22 , the tubular shaped prosthesis  12  inflates to a second diameter, D. The second diameter D is variable in size and dependent upon the force of the medium inflated into the intersecting elongate members  20  and  22  of the tubular shaped prosthesis  12   
     The elongate members  20  and  22  forming the outer wall surface  18  of the tubular shaped prosthesis  12  may be of any suitable synthetic polymeric material which is inflatable and compatible with the human body and with bodily fluids with which the vascular graft or prosthesis  12  may come into contact. In that respect, the elongate members  20  and  22  must be made of a synthetic material which has the requisite strength and elasticity characteristics to permit the tubular shaped prosthesis  12  to be inflated from the configuration shown in FIG. 1A to the configuration illustrated in FIG.  1 B and further to permit the tubular shaped prostheses  12  to retain its inflated configuration providing the enlarged diameter D. Exemplary synthetic polymeric materials for the stent  10  include high-density polyethylene, low-density polyethylene, and polypropylene, as well as interpolymers and block copolymers of these polyolefins. Other polymers such as polyacrylonitrile, polyethylene terephthalate, polybutylene terephthalate, silicones, natural and synthetic rubbers and polytetrafluoroethylene are also suitable materials. Further, it is within the scope of the present invention to provide an inflatable stent as a hybrid of these materials. For example, it may be desirable to provide the stent made of two of the materials so that different portions of the stent inflate at different rates. 
     Preferably, the elongate members  20  and  22  are fabricated from PTFE having a cylindrical cross-section. The elongate members  20  and  22  can, of course, have other cross-sectional configurations, such as triangular, square, rectangular, hexagonal, etc. 
     Finally, the prosthesis  12  is provided with loops  32  and  34  at the respective first and second ends  14  and  16 . The loops  32  and  34  provide for positioning the prosthesis  12  at a treatment zone in the vasculature using the apparatus and method set forth in U.S. Pat. No. 5,948,017 to Taheri. This patent is incorporated herein by reference. 
     FIGS. 2A and 2B show another preferred embodiment of an inflatable intraluminal vascular stent  50  comprising a tubular shaped prosthesis  52  having first and second ends  54  and  56  and an outer wall surface  58  disposed between the ends. The outer wall surface  58  is formed of a plurality of longitudinal members  60  intersecting with lateral numbers  62 , both of a conduit-shaped synthetic material. In the deflated condition, the conduit-shaped elongate members  60  and  62  intersect with one another at right angle junctions, designated  64  in FIG.  2 A. The connecting members  60  and  62  are of a conduit-shaped material in fluid flow communication with each other and with a fill port  28 . The fill port  28 , which is similar to that shown in FIGS. 1A and 1B, is described in detail hereinafter with respect to FIG.  3  and provides for inflating the connecting members  60  and  62  of the stent  50  having a deflated diameter d to provide the expanded stent configuration shown in FIG. 2B having the inflated diameter D. 
     As with the prosthesis  10  shown in FIGS. 1A and 1B, prosthesis  50  is provided with a radiopaque marker  67  and with loops  68  and  70  at its respective ends  54  and  56  for positioning the prosthesis in the vasculature according to U.S. Pat. No. 5,948,017 to Taheri. 
     It should be pointed out that the prosthesis configurations illustrated in FIGS. 1A,  1 B,  2 A and  2 B are only illustrative. In that respect, FIGS. 1A and 1B are provided to illustrate that the present invention covers stents having conduit-shaped members meeting each other at an acute angle in the deflated condition and FIGS. 2A and 2B are provided to illustrate that the present invention also covers stents having conduit-shaped members meeting each other at right angles in the deflated condition. Accordingly, stents  10  and  50  are illustrative and inflatable prosthesis according to the present invention can have a myriad of configurations that are only limited by the imagination of those skilled in the art. For example, U.S. Pat. Nos. B1 4,733,665, 4,994,071, 5,104,404, 5,382,261, 5,449,373, 5,514,154, 5,549,663, 5,569,295, 5,591,197, 5,603,721, 5,697,971, 5,728,131, 5,733,303, 5,735,893, 5,776,161, 5,776,183, 5,800,515, 5,810,872, 5,827,321 and 5,836,964 are illustrative of various alternative shapes of prosthesis devices which can be made of conduit-material, instead of the wire material described in the respective patents, to provide an inflatable prosthesis according to the present invention. 
     FIGS. 1A,  1 B,  2 A and  2 B show the respective stents  10  and  50  having an inflation conduit  72  connectable to the fill port  28  for inflating the stents. As shown in greater detail in FIG. 3, the inflation conduit  72  is a cylindrically shaped member having a threaded fitting  74  at its distal end. The inflation conduit  72  is made of a synthetic material that is flexible enough to travel through the vasculature to the stents  10 ,  50  positioned at a treatment zone in the vasculature. In the alternative, the inflation conduit is connected to the stent as the stent is being deployed to the treatment zone. 
     The threaded fitting  74  is a female shaped member connected to a reduced diameter portion  76  of the distal end of the inflation conduit  72  by a hose clamp  78  and the like. The fitting  74  is provided with double threads  80  that threadingly mate with the double threads  82  of a male fitting  84  secured to a reduced diameter portion  86  of the stent  10 ,  50  by a hose clamp  88 . The male fitting  84  has an internal bore  90  comprising a cylindrical shaped portion  92  leading to a dome-shaped restriction  94 . The dome-shaped restriction  94  communicates with a frusto-conical portion  96  forming a seat  98 . The frusto-conical portion  96  tapers outwardly from the seat  98  to the threaded end of the fitting  84 . The female fitting  74  is provided with an internal frusto-conical bore  100  that tapers outwardly from the threads  80  towards the inflation conduit  72 . When the female fitting  74  is threadingly mated to the male fitting  84  the respective frusto-conical portions  96  and  100  align with each other. The male fitting  84  is also provided with an annular groove  102  intermediate the length of the cylindrical shaped portion  92  of the bore  90 . The annular groove  102  is of a greater diameter than the cylindrical portion  92  and supports a snap-ring  104  that confines a coil spring  106  biasing a ball check valve  108  against the seat  98 . Preferably the ball  108  is of deformable synthetic material to seal against the seat  98  to thereby seal the inflatable stent  10 ,  50 . 
     To inflate the stent  10 ,  50 , the female fitting  74  at the end of the inflation conduit  72  is threadingly mated to the male fitting  84 . Those skilled in the art will readily understand that the inflation conduit  72  could be provided with male threads and the stent fitting  84  with female threads without departing from the spirit and scope of the present invention. The inflation conduit  72  supports an internal release wire  110  having its distal end  112  residing in the frusto-conical sections  96  and  100  and its proximal end  114  disposed in a release plunger  116  (FIG.  4 ). 
     The release plunger  116  has a piston  118  connected to the release wire  110  for moving the wire towards and away from the ball check valve  108 . When the release wire  110  contacts the ball check valve  108 , it overcomes the biasing force of spring  106  to open communication between the inflation tube  72  and the stent  10 ,  50 . With the check valve  108  opened, an inflation plunger  120  of an inflation pump  122  is actuated to fill an inflation medium into the stent  10 ,  50 . This is done by first opening a shut-off valve  124  and moving the plunger  120  toward the opened check valve  108  to move the inflation medium into the stent  10 ,  50 . The inflation medium can comprise a gaseous material such as carbon dioxide, air, a flowable gelatinous material, a metal powder, water or similar fluid and the like. In that manner, the prosthesis is radially and laterally expanded from its collapsed or deflated diameter d to its inflated diameter D. The second diameter D is variable and controlled by the amount of inflation medium flowed into the prosthesis. 
     When the stent  10 ,  50  is properly inflated, the piston  118  of the release plunger  116  is moved away from the stent  10 ,  50  to move the release wire  110  back into the female fitting  74 . This enables the ball check valve  108  to seal against the seat  98  to close communication into and out of the stent. The shut-off valve  124  is closed and if desired, the pump  122  is disconnected from the inflation conduit  72  by coupling  126 . 
     Should it be determined that the stent has been inflated too much, the plunger  120  is actuated to move the release wire  110  to open the check valve  108  as has previously been described. A needle valve  128  on the release plunger  116  is then actuated to open communication with the inflation conduit  72  to bleed off a quantity of the inflation medium through a vent opening  130  of the release plunger  116 . That way, the inflation medium is removed from the stent to deflate it, as needed. This could occur if it is later determined after deployment that the stent is in a position in the vasculature that is not optimum, or if the stent is initially over inflated. 
     At such time as the prosthesis is completely inflated to support the vasculature, the inflation conduit  72  is rotated in the opposite direction from that used to connect the inflation conduit to the stent  10 ,  50 . The inflation conduit  72  is withdrawn from the vasculature and the vasculature is then closed in the normal manner. 
     FIG. 5 is a perspective view showing that it is also within the scope of the present invention to combine the stent  50  with a graft  132 . The graft  132  is a hollow tube of prosthetic material such as Dacron, that is secured to the stent  50  such as by sewing, gluing and the like. The graft further helps to ensure blood flow through the vasculature and to reduce the risk of an aneurysm rupturing, as is well known to those skilled in the art. 
     It is intended that the foregoing description be only representative of the present invention and that the present invention be only limited by it hereinafter appended claims.