Abstract:
A stent designed with an attachable positioning apparatus to effectively place the stent at the precise deployment site within a narrowed vascular region such as an artery. In the preferred embodiment, the present invention comprises a stabilizing wire. The positional apparatus is, for example, frictionally engaged to the stent balloon and adjacent wire loops for frictional engagement with the walls to position the stent at the deployment site. Other means to engage the positional apparatus and stent balloon and adjacent wire loops can include: elastic bands, adhesion, or polymer bonding. The stent is maneuvered through the vessel by a balloon catheter that is guided by a guiding catheter up the vessel to where the narrowing is located. Upon exiting the guiding catheter and approaching the deployment site within the coronary artery, the wire loops expand and frictionally engage the artery walls and, thereby, effectively position the stent at the deployment site within the narrowed vessel. This apparatus and method is particularly useful for stent placement at an ostium (origin) of a vascular region.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to an intravascular stent and, in particular, to an apparatus and method to quickly, effectively, and accurately position a stent within a stenosed (narrowed) vascular region, particularly at its ostium (origin).  
           [0003]    2. Background And Description of The Prior Art  
           [0004]    A stent is an intravascular prosthesis implanted in a blood vessel to maintain vascular patency in an artery, vein, lymph, or another duct in the body such as the biliary duct, ureter, or urethera (collectively referred to as vessels). For example, a stent is often a necessary treatment for atherosclerosis. Atherosclerosis is an accumulation of lipids, also known as lesions, plaques, or atheromas, in the intimal or inner layer of an affected artery. The resulting intimal thickening of lipids restricts arterial blood flow, disrupting the function of or permanently damaging the nourished organ such as the heart. Typically, the accumulation of lipids is localized and occurs in coronary, renal, cerebral, or peripheral arteries.  
           [0005]    Treatments for atherosclerosis focus on improving blood flow through narrowed arteries. One method, balloon angioplasty, simply expands a balloon catheter to compress lipid plaque against the artery wall. Unfortunately, scar tissue (neointimal proliferation) often builds up over time and renarrows the artery. This is called restenosis. To reduce the chance of restenosis, stents are often implanted. A stent is an expandable meshed metal tube used to support a narrowed artery after angioplasty. In this procedure, the stent is deployed at the center of the lipid accumulation. Once a deployment site is identified, the stent is maneuvered through the vessel to that site. Physicians typically use fluoroscopic x-ray and injection of radiopaque contrast and marking bands on the stent balloon to determine if the stent is positioned at the narrowed region. Once positioned, the stent expands to compress the lipids, thereby opening the artery and increasing blood flow. Stenting, as described in the prior art, significantly reduces restenosis of the artery compared to balloon angioplasty alone.  
           [0006]    Unfortunately, prior art stent positioning methods and apparatuses have several inherent shortcomings. First, the physician must rely on hand and eye coordination, using the radiopaque marking bands, to position the stent. Second, the radiopaque marking bands are generally placed either in the front of or at the back of the stent. As a result, the doctor must estimate the center position of the stent at the deployment site based on the marked stent ends. This procedure is imprecise. Third, when the stent is deployed in a coronary artery, the doctor must constantly fight the movement of a beating heart that changes the position of the artery with each inspiration and expiration. As the artery changes position, the stent position may also change. And fourth, the prior art is not able to precisely position and deploy a stent when the narrowing is at the origin (ostium) of a vessel.  
           [0007]    Ineffective and inaccurate stent placement results in a poor overall patient outcome. If the stent is deployed too distal to the vessel narrowing, ineffective plaque compression results. Further, a higher rate of restenosis may be expected. If the stent is placed too proximal to a narrowing at the aorta origin (ostium), the stent may hang into the aorta and a thrombus (clot) may form on the stent. Placement of the stent too proximal may also result in inappropriate and unintended blockage of another blood vessel.  
           [0008]    Thus, an apparatus and method is needed to more effectively and accurately position a stent at a desired deployment site within the narrowed area of a vessel, thereby improving overall patient outcome.  
         SUMMARY OF THE INVENTION  
         [0009]    Accordingly, the present invention provides an apparatus and method to effectively position a stent within an intravascular region (vessel) that has narrowed, including the ostium (origin) of the vessel. Additional and related objects of the present invention include: providing a more efficient device to position the stent at a deployment site; reducing the number of stents required to compress the plaque and open the vessel to abate the reduction in blood flow caused by the occlusion; preventing restenosis; reducing the amount of time needed to position the stent within the narrowed vessel, thereby reducing the amount of time required to perform the procedure; reducing the amount of time that a patient must remain in the cardiac catheterization lab; reducing radiation exposure to the patient and cardiac catheterization staff; reducing the amount of radiopaque contrast used, thereby decreasing the risk of renal failure; minimizing the costs to repair and strengthen a narrowed vessel; and reducing heart movement as a stenting obstacle, whereby the stent maintains position within a narrowed coronary artery prior to deployment.  
           [0010]    The present invention comprises a positional apparatus for a stent. The positional apparatus can be frictionally engaged to the distal end of the stent, stent balloon or stent catheter. Other possible ways to attach the apparatus to the stent may include elastic bands, springs, adhesives, welds, clasps, screws, snaps, magnets, polymer bondings, or by contiguous formation with the stent, stabilizing wire or a balloon catheter. The apparatus has an expandable and retractable element used to engage the vessel wall to position the stent at the deployment site. The apparatus and stent are maneuvered through the vessel by a balloon catheter that is guided by a guiding wire and guiding catheter up the vessel to the narrowing. Upon exiting the guiding catheter and approaching the deployment site within the narrowed vessel, the positional element is expanded, thereby engaging the wall of the vessel and positioning the stent at the precise deployment site within the narrowed vessel.  
           [0011]    Other objects of the present invention will become more apparent to persons having ordinary skill in the art to which the present invention pertains from the following description taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0012]    The foregoing objects, advantages, and features of the present invention, as well as other objects and advantages, will become apparent with reference to the description and drawings below, in which like numerals represent like elements and in which:  
         [0013]    [0013]FIG. 1 is a side elevational view of a positional apparatus for a stent.  
         [0014]    [0014]FIG. 2 is a front cross-sectional view of the positional apparatus illustrating one of the preferred embodiments of the present invention with a connector (spring) expandable element (wire loops).  
         [0015]    [0015]FIG. 3 is a side elevational view of a stabilizing wire attached to the positional apparatus and stent and coaxially mounted within a balloon catheter.  
         [0016]    [0016]FIG. 4 is a front view of a patient illustrating insertion of the stent into the human body and the direction the stent follows to a narrowed vascular region.  
         [0017]    [0017]FIG. 5 is a side cross-sectional view of a vessel with the positional apparatus and stent at the vessel deployment site.  
         [0018]    [0018]FIG. 6 is a front cross-sectional view, taken along line  6 - 6  of FIG. 5, of the narrowed vessel in relation to the positional device, stent and the Stabilizing Wire.  
         [0019]    [0019]FIG. 7 is a side cross-sectional view of the expanded balloon catheter and stent being deployed within a vessel.  
         [0020]    [0020]FIG. 8 is a side cross-sectional view of the deployed stent and the removal of the stent placement device, Stabilizing Wire, and catheter.  
         [0021]    [0021]FIG. 9 is a side perspective view of the stent as deployed within the narrowed vessel.  
         [0022]    [0022]FIG. 10 shows a side perspective view of the stent, catheter balloon, and positional device while moving toward the narrowed vascular region.  
         [0023]    [0023]FIG. 11 shows a side perspective view of the catheter balloon and positional device while moving away from the stented vascular region.  
         [0024]    [0024]FIG. 12 shows an alternative preferred embodiment of the present invention using a new type of balloon catheter with an annular ring.  
         [0025]    [0025]FIG. 13 shows an alternative preferred embodiment of the present invention using a flange as the deployment site regulator.  
         [0026]    [0026]FIG. 14 shows an alternative preferred embodiment of the present invention using rods as the deployment site regulator. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]    The present invention generally relates to a device and method for stent placement. Although the preferred embodiment describes use within an artery, the invention could be applied to any region of a person or animal where stent placement is used to open a narrowed vessel. Please note that proximal and distal orientation relationships in this description are in relationship to their point of insertion in a body and not the orientation about the narrowing of the vessel. This includes orientations of the stent apparatus itself where the proximal stent end is actually what many physicians refer to as the distal stent end.  
         [0028]    [0028]FIG. 1 illustrates a stent positioning apparatus  20  in one of its preferred embodiments and is not intended to limit the apparatus in any way. The preferred stent positioning apparatus  20  consists of a plurality of stabilizing wires  22  and a deployment site regulator  24 . The stabilizing wires  22  have a proximal end  26  and a distal end  28 . Proximal end  26  and distal end  28  are separated by a stabilizing wire length  30  with a stabilizing wire spacing diameter  32 . The stabilizing wire length  30  is of sufficient length to reach a narrowed region within either a primary blood vessel or a coronary artery. Preferably, the stabilizing wire length  30  is approximately  160  centimeters long and the stabilizing wire spacing diameter  32  is approximately 0.3 centimeters wide.  
         [0029]    The deployment site regulator  24  is attached to the distal end  28  of the stabilizing wires  22 . Attachment can be by means of frictional engagement, elastic bands, springs, adhesives, welds, clasps, screws, snaps, magnets, polymer bondings, or contiguous with any stent placement element such as a stent  46 , a balloon catheter  54  or the stabilizing wires  22 . In the preferred embodiment, the deployment site regulator  24  comprises a spring  34  and a plurality of wire loops  36 . The spring  34  is attached to the stabilizing wires  22  such that the spring  34  and stabilizing wires  22  will not become detached during a stent procedure. The wire loops  36  extend outwardly from and parallel to spring  34 . The wire loops  36  are attached to spring  34  at an attachment point  38 . Preferably, wire loops  36  are permitted unrestricted rotation about attachment point  38  in relation to spring  34 . The unrestricted rotation allows wire loops  36  to be maneuvered through a guiding catheter  40 , having a guiding catheter sheath  98  (FIG. 5), to or from the narrowed region of the vessel during the stent procedure. Wire loops  36  have a surface such that contact with the interior walls of guiding catheter  40  does not impede the progress of wire loops  36  through guiding catheter  40 , but is sufficient to frictionally engage a vessel  48  interior wall (FIG. 4) without damaging the vessel  48 .  
         [0030]    In FIG. 5, vessel  48  has a vessel diameter  102  that is sufficiently smaller than a wire loop diameter  104  (FIG. 6) in its natural position. Preferably, wire loops  36  are made of a nitinol wire frame. Alternatively, the wire loops  36  may be made of another type of wire frame or material, provided the wire loops  36  made with the alternative material are able to perform the same functions as the wire loops  36  with the nitinol wire. A further embodiment, described below and shown in FIG. 12, removes the wire loops  36  and instead uses a balloon catheter with an expanded diameter annular ring to engage adjacent structures of the vessel  48 .  
         [0031]    Other embodiments of the deployment site regulator  24  could include any device that can make its way through the guiding catheter sheath  98  in a retracted position, but can expand to engage adjacent structures of the vessel  48 . These could include a rubber flange  108  (FIG. 13) or outward radiating rods  110  (FIG. 14) instead of loops.  
         [0032]    [0032]FIG. 2 illustrates the deployment site regulator  24  with more specificity. Preferably, the stabilizing wires  22  and spring  34  are circular in shape and the spring  34  has a diameter  42  approximately equal to the stabilizing wire spacing diameter  32 . Spring  34  is a closed loop that consists of a plurality of coils  44 . The coils  44  are situated adjacent to one another in equal spacing around the entire periphery of spring  34 . Coils  44  permit spring  34  to be expanded during the stent procedure. Wire loops  36  are attached to spring  34  between coils  44 . Preferably, wire loops  36  are equally spaced around the entire periphery of spring  34 . FIG. 2 is a non-limiting example which depicts eight wire loops  36  around the entire periphery of spring  34 . Alternatively, the deployment site regulator  24  may contain more or fewer wire loops  36  as long as the proper frictional engagement is provided by wire loops  36  to accurately position the stent  46  (FIG. 3) at the deployment site within the vessel  48 . The deployment site regulator  24  is releasably attached to the stent  46  using a frictional engagement. As the stent  46  expands to the deployed position, the deployment site regulator  24  is released from the stent  46 . Elastic bands, springs, adhesives, welds, clasps, screws, snaps, magnets, polymer bondings, or contiguous with the stent  46  or the stabilizing wires  22  can be used rather than frictional engagement to releasably attach the stent  46  to the deployment site regulator  24 . In an alternative embodiments shown below, a specially shaped catheter is described.  
         [0033]    The interconnection of stent  46  to stabilizing wires  22  is more clearly illustrated in FIG. 3. Stent  46  is generally a hollow, cylindrical prosthesis that comprises thin walled, tubular members that define a narrow web-like mesh. Stent  46  has a stent proximal end  50  and a stent distal end  96 . Stent distal end  96  of stent  46  is attached to spring  34  at proximal end  26  of the stabilizing wires  22 . Stent  46  has a stent length  52  of approximately eight to thirty-eight millimeters. Extending throughout the hollow center of stent  46  and stabilizing wires  22  is the balloon catheter  54 . Balloon catheter  54  comprises a balloon  56  and a balloon shaft  58 . Balloon  56  is releasably mounted and centered within stent  46  and has a balloon length  60 . The balloon length  60  will correspond to the stent length  52  and has an overhand of approximately 0.1-0.2 millimeters beyond the stent  46 . Alternatively, the balloon length  60  may be equal to or smaller than the stent length  52  as long as balloon  56  is capable of inflating to effectively expand stent  46 . Within balloon  56  is a balloon guidewire  62 . Balloon guidewire  62  has a balloon guidewire diameter  64 . In the preferred embodiment, balloon guidewire diameter  64  is 0.14 centimeters.  
         [0034]    Balloon shaft  58  has a balloon shaft diameter  66 . In the preferred embodiment, balloon shaft diameter  66  is approximately 0.8 millimeters.  
         [0035]    In FIG. 4, a non-limiting example of the inventive apparatus is depicted in which guiding catheter  40  is inserted into a human body  68 . Typically, guiding catheter  40  is inserted or cannulated into the vessel  48  which is located in a leg  70  of the human body  68 . A portion of guiding catheter  40  remains outside of the human body  68  while the remainder of guiding catheter  40  is inserted into human body  68 . Guiding catheter  40  enters human body  68  at an incision point  72  and follows through vessel  48  along a path  74 . Vessel  48 , at incision point  72 , is a femoral artery that becomes an iliac artery and then the aorta artery at the point where the iliac arteries merge. Guiding catheter  40  follows path  74  until it reaches a point near the primary coronary arteries of a heart where a narrowed vascular region  76  is located.  
         [0036]    In FIG. 5, the proximal portion of vessel  48  is enlarged to depict its origin and the positioning of stent  46  within the narrowed vascular region  76 , the site of deployment. Narrowed vascular region  76  consists of an accumulation of lipids  78  that form large patches (atherosclerotic plaques)  80  and  82  on the interior walls of vessel  48 . In many instances, patch  80  almost contacts patch  82 . Narrowed vascular region  76  represents the location of the highest concentration of lipids  78  in which patches  80  and  82  restrict the greatest amount of blood flow through vessel  48 .  
         [0037]    To perform the stent procedure, guiding catheter  40 , as explained earlier, is first inserted into human body  68  and manipulated through vessel  48  to a holding position  84  near the entry of vessel  48  and the narrowed vascular region  76 . Next, stent  46  and balloon  56  are connected to the stent positioning apparatus  20  outside the human body  68 . A stent-balloon catheter combination  86  with the stent positioning apparatus  20  attached is inserted into and manipulated through the guiding catheter sheath  98 . During the manipulation through guiding catheter sheath  98 , wire loops  36  contact the interior wall and are forced into a rearward trailing position with respect to stent  46 , as illustrated in FIG. 10. Stent-balloon catheter combination  86  exits guiding catheter  40  at holding position  84 . Upon exiting guiding catheter  40 , wire loops  36  return to an approximately perpendicular position with respect to stent  46 . The stent-balloon catheter combination  86  is then manipulated toward narrowed vascular region  76 . Upon nearing narrowed vascular region  76 , the target deployment site, the wire loops  36  begin to frictionally engage the adjacent walls of vessel  48  at engagement points  88  and  90 . The frictional engagement of the wire loops  36  with the walls of vessel  48  adjacent to the deployment site suspends the forward movement of stent-balloon catheter combination  86  through vessel  48 . The forward movement of stent-balloon catheter combination  86  is suspended at the deployment site and stent-balloon catheter combination  86  is centered directly within narrowed vascular region  76  as illustrated more clearly in the cross-sectional view of FIG. 6.  
         [0038]    [0038]FIG. 6 illustrates the accumulation of lipids  78  around the entire interior periphery of vessel  48  with stent-balloon catheter combination  86  located in the center of vessel  48  at the deployment site. Once stent-balloon catheter combination  86  is positioned within the deployment site of narrowed vascular region  76 , balloon  56  is inflated, as illustrated in FIG. 7. When balloon  56  begins to inflate, the exterior of balloon  56  contacts the interior of stent  46  and outwardly forces stent  46  into an expanded position. As stent  46  expands with the inflation of balloon  56 , spring  34  correspondingly expands with stent  46  to expansion points  92  and  94  in FIG. 7. As balloon  56  inflates, it applies pressure on lipids  78 . Since lipids  78  are a waxy type material, lipids  78  succumb to the pressure of balloon  56  and, thereby, compress against the walls of vessel  48 . The compression of lipids  78  reduces the blockage and expands the diameter of vessel  48  to restore vessel patency or blood flow through vessel  48 .  
         [0039]    In FIG. 8, with the stent  46  in place, balloon  56  is deflated and balloon catheter  54  with the stent positioning apparatus  20  is retracted through the guiding catheter  40  for removal from human body  68 . Guiding catheter  40  is then removed from human body  68 . FIG. 11 illustrates the removal of the balloon catheter  54  and the stent positioning apparatus  20 . As before, wire loops  36  contact the interior wall of vessel  48  and are forced into a rearward trailing position with respect to the direction of removal. Stent  46  remains within vessel  48 , as illustrated in FIG. 9, as a prosthesis to repair or strengthen vessel  48  and prevent restenosis.  
         [0040]    As an alternative preferred embodiment of the present invention, FIG. 12 illustrates a specially designed balloon catheter instead of the plurality of wire loops  36  to hold the stent  46  in place. As shown, prior to reaching the narrowed vascular region  76 , an annular ring balloon  100  is inflated until an annular ring balloon diameter  106  sufficiently exceeds the vessel diameter  102  to suspend the forward movement of the stent-balloon catheter combination  86  through vessel  48 . This embodiment could also be achieved using only one balloon catheter. This specially shaped catheter would be partially inflated before reaching the narrowed vascular region  76  so that the stent-balloon catheter combination  86  portion of the catheter was smaller in diameter than vessel diameter  102 , including narrowed vascular region  76 . But, the annular ring balloon  100  portion would, as before, have an annular ring balloon diameter  106  sufficiently exceeding the vessel diameter  102  to suspend the forward movement of the stent-balloon catheter combination  86  through vessel  48 .  
         [0041]    Thus, an apparatus and method is provided to guide the placement of a stent within the deployment site of a narrowed blood vessel for accurate deployment during a stent procedure. While the invention has been described in conjunction with specific embodiments, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, the present invention attempts to embrace all such alternatives, modifications and variations that fall within the spirit and scope of the appended claims.