Abstract:
A first aspect of the present invention is an ostial stent positioner that has the form of a wire for most of its length and having a cylinder with expandable legs situated at the positioner&#39;s distal end. The cylinder with its attached wire acts as an introducer sheath to introduce a stent delivery system with a stent into the artery that is to be stented. A second aspect of the present invention is a method for accurately placing a stent at the ostium of an artery that would have an ostial stenosis. Examples of such arteries that have ostial stenoses are the right and left main coronary arteries, a saphenous vein graft as used in coronary bypass surgery and the renal arteries. Each of these arteries has an ostium situated at the aorta.

Description:
FIELD OF USE  
       [0001]     This invention is in the field of devices for placing stents within a stenosis that extends to or near the ostium of an artery.  
       BACKGROUND OF THE INVENTION  
       [0002]     Although most stenoses do not occur at the ostium of an artery, there are thousands of cases each month where the mouth of an artery (the ostium) is substantially obstructed at its aortic take-off; this is called an aorto-ostial lesion. In such cases, the interventional cardiologist or radiologist is frequently unable to place the stent&#39;s proximal end within ±2 mm of the ostial plane. Two types of incorrect stent positions are (1) when the stent&#39;s proximal end extends more than 2 mm into the aorta, and (2) when the stent&#39;s proximal end is placed more than 1-2 mm into the artery distal to the ostial plane.  
         [0003]     In U.S. Pat. No. 6,458,151, F. S. Saltiel describes an ostial stent positioning device. However, the most important feature of such a device; namely, and expandable distal portion that touches the wall of the aorta near the ostium of the artery to be stented is not optimized for easy usage of such a device.  
         [0004]     In U.S. Pat. No. 5,749,890, A. Shaknovich utilizes a stent mounted on a catheter that has an inflatable section that touches the wall of the aorta in the vicinity of the ostium of the artery that is to be stented. Such a design precludes an accurate stent positioning system that can be used with the stent delivery system of any manufacturer.  
       SUMMARY OF THE INVENTION  
       [0005]     A first aspect of the present invention is an ostial stent positioner that has the form of a wire for most of its length and having a cylinder with expandable legs situated at the positioner&#39;s distal end. The cylinder with its attached wire acts as an introducer sheath to introduce a stent delivery system with a stent into the artery that is to be stented. A second aspect of the present invention is a method for accurately placing a stent at the ostium of an artery that would have an ostial stenosis. Examples of such arteries that have ostial stenoses are the right and left main coronary arteries, a saphenous vein graft as used in coronary bypass surgery and the renal arteries. Each of these arteries has an ostium situated at the aorta.  
         [0006]     The method for using this invention would be to first back load the ostial stent positioner within a guiding catheter. The next action would be to place the guiding catheter through the aorta in a conventional manner so that its distal end will be engaged within or near the ostium of the artery that is to be stented. A guide wire would then be advanced through the guiding catheter until its distal end was placed distal to the stenosis. If pre-dilitation of the ostial stenosis was needed, a balloon angioplasty catheter would be advanced over the guide wire and through the guiding catheter and the catheter&#39;s balloon would be inflated to pre-dilate the stenosis. After the balloon angioplasty catheter was removed from the guiding catheter (or if no pre-dilatation was required) then a stent delivery system with the required stent would be advanced over the guide wire until the stent&#39;s proximal end lay distal to the ostium of the artery. The stent delivery system would have its proximal radiopaque marker band placed just distal to the ostial plane of the artery to be stented. While retaining the guide wire and a distal portion of the stent delivery system in the artery, the guiding catheter with the positioner inside would then be pulled back a short distance into the aorta. The positioner would then be advanced until its expandable legs at the positioner&#39;s distal end extended beyond the guiding catheter&#39;s distal end, thus allowing the expandable legs to fully expand. The guiding catheter would then be advanced until its distal end surface pushes gently against the positioner&#39;s expandable legs to engage them against the wall of the aorta and generally align the legs at the ostium of the artery that is to be stented. The plane of the “feet” which are located at the distal ends of the expandable legs would then be situated at the artery&#39;s ostial plane. Since the expandable legs would have feet that would be formed from a material that included a radiopaque substance or from a metal that is coated with or made from a radiopaque metal, the interventional cardiologist who is performing this procedure would have a clear angiographic/fluoroscopic marker of the ostial plane of the artery that is to have a stent placed within the ostial stenosis of that artery. The interventional cardiologist would then pull the stent delivery system back until the proximal radiopaque marker band within the balloon of the stent delivery system was aligned appropriately relative to the radiopaque feet of the expandable legs. The balloon would then be inflated to deliver the stent accurately at the ostial stenosis with the stent&#39;s proximal end lying within 2 mm of the ostial plane of the artery (typically just proximal to the true ostial plane). It is expected that an experienced interventional cardiologist could place the proximal end of the stent within 1.0 mm, just proximal to the ostial plane.  
         [0007]     The main objects of this invention is to provide a means and method for accurately placing the proximal end of a stent within ±2 mm of the ostial plane of an artery that has a stenosis located at or near the ostium of that artery.  
         [0008]     Another object of this invention is to place the proximal end of a stent within ±1.0 mm of the ostial plane of an artery that has a stenosis located at or near the artery&#39;s ostium.  
         [0009]     Still another object of the present invention is to teach a method for accurately placing a stent within an ostial stenosis.  
         [0010]     These and other objects and advantages of this invention will become obvious to a person of ordinary skill in this art upon reading the detailed description of this invention including the associated drawings as presented herein. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a side view of a Touhy-Borst fitting, a guiding catheter and an ostial stent positioner that acts as an introducer sheath for placing the proximal end of a stent in close proximity to the ostial plane of an artery that has an ostial stenosis.  
         [0012]      FIG. 2  is a longitudinal cross section of a distal portion of the ostial stent positioner located within the guiding catheter showing the expandable legs in their folded state.  
         [0013]      FIG. 3  is a cross section of a distal portion of the guiding catheter, a stent on a stent delivery system and the positioner showing the distal end plane of the feet of the expandable legs placed at the ostial plane of an artery having an ostial stenosis.  
         [0014]      FIG. 4  is an alternate embodiment of the present invention using a self-expandable cylinder with expandable legs that is made from a shape memory alloy such as Nitinol.  
         [0015]      FIG. 5  is a cross section of an introducer that is designed to facilitate the introduction of the self-expandable cylinder of  FIG. 4  into a guiding catheter. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]      FIG. 1  is a side view of a catheter system  10  whose object is to accurately place a stent with its proximal end being situated close to the ostial plane of an artery having an ostial stenosis. The catheter system  10  would include an ostial stent positioner  17  that has a wire  11  which connects a small diameter handle  12  to a cylinder  16  (shown in  FIG. 2 ) which has expandable distal end legs  14  with radiopaque feet  15 .  FIG. 1  also shows a guiding catheter  40  that has a proximal Luer fitting  41  that is joined to a Touhy-Borst fitting  30 . When the feet  15  are fully expanded, the diameter “D” would typically be between 4 and 10 mm for coronary artery stenting and between 5 and 15 mm for stenting a renal artery. When the expandable legs  15  with radiopaque feet  15  are fully expanded they would have the general appearance of the petals of a flower. When the legs  15  are pushed forward beyond the distal end of the guiding catheter  40 , they expand radially outward as shown in  FIG. 1 . When the handle  12  is pulled back, the legs  15  are retracted into the guiding catheter  40  and then the positioner  17  can be pulled out of the guiding catheter  40  after the stent has been placed into the ostial stenosis.  
         [0017]     The Touhy-Borst fitting  30  has an adjustable seal fitting  31  (which is a hemostasis valve) that can initially be slightly loosened to allow the positioner  17  to be advanced or pulled back through the guiding catheter  40  without excessive blood leakage. When the expandable legs  14  are in their correct position for placement at the ostial plane of a stenosed artery, (as seen in  FIG. 3 ) the adjustable seal fitting  31  can be tightened to hold a fixed position of the legs  23  relative to the guiding catheter  40  during stent deployment. The Luer fitting  32 , being in fluid communication with the lumen of the guiding catheter  40 , can be used for flushing the lumen with saline solution and/or for injecting contrast medium. The Luer connector  33  is used to form a removable fluidic seal with the Luer fitting  41  of the guiding catheter  40 .  
         [0018]      FIG. 2  is an enlarged cross section of the distal portions of the guiding catheter  40  and the positioner  17 . The positioner  17  is shown with its expandable legs  14  in their unexpanded state within the guiding catheter  40 . In this state, the guiding catheter  40  can be advanced through an introducer sheath at the patient&#39;s groin until its distal end is within the ostium of the artery that is to be stented. Furthermore, in this state, both a guide wire and a stent delivery system can be advanced through the guiding catheter  40  and through the ostial stenosis. The cylinder  16  is attached at its proximal end to the wire  11  and at its distal end to each of the four legs  14 . Although 3 legs  14  (of an actual  4  legs) are shown in  FIG. 2 , as few as 2 or as many as 16 of petal-like legs  14  could be used for an effective array of expandable legs  14 .  
         [0019]      FIG. 3  is a cross section of a distal portion of the catheter system  10  shown with the distal plane  45  of the feet  15  placed at the ostial plane of a stenosed artery. The feet  15  are attached to the expandable legs  14  that are attached to the cylinder  16  which has its position within the guiding catheter  40  adjusted by means of the wire  11 . Any such placement of the feet  15  can be defined as having their distal plane  45  “co-planar” with the ostial plane of the artery that has an ostial stenosis.  FIG. 3  also shows a guide wire  26  placed through the stent delivery system  20  which has a shaft  21 , a proximal radiopaque marker band  24 , a distal radiopaque marker band  25  and a stent  23  mounted onto a balloon  22 . The ostial stent positioner  17  would be designed to introduce essentially any commercially available stent delivery system  20  into an arterial stenosis. Thus, any interventional cardiologist could use the positioner  17  with any stent delivery system that he or she favors.  FIG. 3  also shows how the guiding catheter  40  is used to gently push the feet  15  against the wall of the aorta at the ostium of the stenosed artery.  
         [0020]     At the start of the stenting procedure, the ostial stent positioner  17  would be positioned as shown in  FIG. 2  with the expandable legs  14  placed inside the guiding catheter  40 . The catheter system  10  and the guide wire  11  could then be advanced through a conventional introducer sheath (not shown) typically placed at the groin of the patient into whom the stent  23  is to be placed. The guide wire  26  (or a separate 0.035 inch diameter guide wire) would be placed into and through the ostial stenosis and the guiding catheter  40  would be advanced until its distal tip was placed through the arterial ostium. The stent delivery system  20  would then be advanced over the guide wire  26  and through the guiding catheter  40  until the proximal radiopaque marker band  24  was positioned just distal to the ostium of the stenosed artery. The guiding catheter  40  would then be pulled back into the aorta. The positioner  17  (which was already back loaded into the guiding catheter  40 ) would then be advanced through the guiding catheter  40  until the expandable legs  14  extended out of the distal end of the guiding catheter  40 . The guiding catheter  40  would then be pushed gently forward in a distal direction so as to obtain the configuration as generally shown in  FIG. 3 .  
         [0021]     With the configuration as shown in  FIG. 3 , the interventional cardiologist would be able to clearly visualize the distal plane  45  of the radiopaque feet  15  and also visualize the proximal radiopaque marker band  24 . When the radiopaque marker band  24  is pulled backward until it is co-planar with feet  15 , then the proximal end of the stent  23  would be placed within ±2 mm of the plane of the ostium of the vessel which is to be stented. The balloon  22  would then be inflated to deliver the stent  23  into the ostial stenosis. Thus, an interventional cardiologist should be able to readily place the proximal end of the stent  23  within ±2 mm of the ostial plane. With some experience, it is expected that the proximal end of the stent  23  could be placed within at least ±1.0 mm of the ostial plane and probably within ±0.5 mm.  
         [0022]     Although one method for accurately placing the stent  23  into an ostial stenosis has been described herein, it should be understood that there are several other ways that the present invention could be used to provide accurate stent positioning within an ostial stenosis. For example, the guiding catheter  40  with the positioner  17  in place as shown in  FIG. 2  could first be placed over a 0.035 inch diameter guide wire and into the lumen of the ostial stenosis. That larger diameter guide wire could then be removed and a 0.014 inch diameter guide wire could be placed through the stenosis. The stent delivery system  20  could then be advanced over that guide wire  26  and positioned as shown in  FIG. 3 . The guiding catheter could then be pulled back and the expandable legs  14  could then be deployed as described herein. An important feature of the system  10  is that the guiding catheter  40  and positioner  17  could be held to be motionless while the guide wire  26  or the stent delivery system  20  could be advanced forward or pulled back to obtain an accurate positioning of the stent  23  within the ostial stenosis.  
         [0023]      FIG. 4  is a flat layout view of self-expandable cylinder  50  that would replace the fixed diameter cylinder  16  of  FIGS. 2 and 3 . The strut  56  is designed to join to a wire that is equivalent to the wire  11  of  FIGS. 1, 2  and  3 , which wire is used to move the ostial stent positioner  17  within the guiding catheter  40 .  FIG. 5  shows the wire  11  attached to the proximal end of the strut  56 . This attachment can be by means of welding, soldering or (with a somewhat different configuration) by means of a biocompatible adhesive. It is also conceived that the cylinder  50  and the wire  11  can be formed from a single piece of metal. The circumferential struts  51  provide a spring-like action to gently place the straight struts  52  against the inner wall of the guiding catheter  40 . The expandable legs  54  with radiopaque feet  55  are joined to both the struts  51  and  52 . The feet  55  could be made radiopaque by plating with a highly radiopaque metal such as platinum, gold or tantalum or they could be made from a high density metal.  
         [0024]     To introduce a stent delivery system into a coronary artery, the typical diameter for the guiding catheter  40  would be 6, 7 or 8 French (Fr). It would be highly desirable for the ostial stent positioner  17  to be made with a single diameter of its cylinder that holds the expandable legs  54 . This would decrease the inventory requirements for the positioner  17  for each cath lab that performs coronary interventions. Specifically, only one diameter of the expandable struts  51  would be required and it would fit into guiding catheters that are either 6, 7 or 8 Fr. It would also be highly desirable to have the cylinder  50  (as shown in  FIG. 4 ) expand radially outward to gently press outwardly onto the inner surface of the guiding catheter  40 . To that end, the cylinder  50  could be formed from a shape memory alloy such as Nitinol. To have a single product that would be suitable for 6, 7 or 8 Fr guiding catheters, the outer diameter of the cylinder  50  should be approximately the inside diameter of an 8 Fr guiding catheter. Such a cylinder  50  would then also fit snugly within either 6 Fr or 7 Fr guiding catheters. The wall thickness for the cylinder  50  would ideally be between 0.001 and 0.003 inches.  
         [0025]      FIG. 5  is a highly enlarged cross section of an introducer  60  that would be used to place the self-expandable cylinder  50  into the guiding catheter  40 . The introducer  60  would have an outer diameter of its cylindrical portion  61  that was just smaller in diameter than the inner diameter of the 6 Fr guiding catheter. With the assistance of its tapered end  66 , the introducer  60  could then be placed into a 6, 7 or 8 Fr guiding catheter. To insert the ostial stent positioner  17  with the self-expandable cylinder  50  into the introducer  60 , the wire  11  attached to the strut  56  would first be placed through the cone  64  and then it would be pulled through the interior cylindrical surface  63 . The conical surface  64  would compress the self-expandable cylinder  50  to a small enough outside diameter to be able to be inserted into a 6 Fr (or even smaller diameter) guiding catheter. It is also envisioned that a carefully made cylinder  50  could be compressed enough to be placed into and used with a guiding catheter as small as 4 Fr. It should also be understood that a larger diameter guiding catheter  40  could be used specifically for treating an ostial stenosis in a renal artery. Guiding catheters as large as 14 Fr could be used for inserting a stent into an ostial stenosis. Of course, the expanded diameter of the cylinder  50  must also be at least slightly larger than the inside diameter of any such a guiding catheter. When the wire  11  has been used to pull the self-expandable cylinder  50  into the interior cylinder  63 , the proximal end of the cylinder  50  should be generally aligned with the plane  67  of the introducer  60  as shown in  FIG. 5 . When this condition is met, the distal end of the radiopaque feet  15  will be a distance “L” from the plane of the shoulder  65  of the holding cylinder  62 . This positioning will accurately align the feet  55  within the guiding catheter  40  so that the configuration will be as shown in  FIG. 2 .  
         [0026]     To properly place the self-expandable cylinder  50  into the guiding catheter  40 , the wire  11  is first back loaded through the guiding catheter  40  and the introducer  60  is pushed through the distal end of the guiding catheter  40  until the shoulder  65  is against the guiding catheter&#39;s distal end. The introducer  60  is then pulled out of the guiding catheter  40  while holding onto the handle  12  of  FIG. 1  of the ostial stent positioner  17 . When this is done, the distal end of the radiopaque feet  15  will be exactly the distance “L” from the distal end of the guiding catheter  40 . This will be exactly the correct distance when the guiding catheter  40  including the ostial stent positioner  17  are advanced together until the distal end of the guiding catheter  40  lies at or into the ostium of the stenosed artery. The holding cylinder  62  is designed so that it can be easily held by the operator when placing the introducer  60  into the guiding catheter  40 . The introducer  60  could be machined from a metal such as aluminum or molded from a clear plastic material such as polycarbonate. A transparent (i.e., a clear) plastic would have the advantage of allowing the operator to see the self-expandable cylinder  50  being advanced into the introducer  60  and the guiding catheter  40 . Alternatively, the introducer  60  could be formed from a thin metal cylinder that makes up the cylinder  61  that is molded into the rest of the structure of the introducer  60 .  
         [0027]     Various other modifications, adaptations and alternative designs are of course possible in light of the teachings as presented herein. Therefore it should be understood that, while still remaining within the scope and meaning of the appended claims, this invention could be practiced in a manner other than that which is specifically described herein.