Abstract:
A stent delivery system is disclosed for delivering and deploying a radially expandable stent at a strategic orientation and location in a body vessel. The delivery system includes an elongated flexible tubular shaft sized suitably for insertion into the body vessel, first and second inflatable members disposed adjacent the distal end of the elongated shaft and an endoprosthesis disposed about the first and second inflatable members. The delivery system further includes a tip assembly which during to advancement of the delivery system is configured as a single tip assembly, wherein prior to deployment of the expandable endoprosthesis, the tip assembly is split into a first tip and a second tip, wherein one of the tips remains in a main branch and the second tip is advanced into a side branch lumen to align the endoprosthesis prior to deployment.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to catheters and systems used for delivering devices such as, but not limited to, intravascular stents and therapeutic agents to sites within vascular or tubular channel systems of the body. More particularly, it relates to delivery catheters and systems for delivering stents to bifurcated vessels.  
       BACKGROUND OF THE INVENTION  
       [0002]     A type of endoprosthesis device, commonly referred to as a stent, may be placed or implanted within a vein, artery or other tubular body organ for treating occlusions, stenoses, aneurysms or dissections of a vessel by reinforcing the wall of the vessel or by expanding the vessel. Stents are normally placed to scaffold the vessel and avoid elastic recoil after angioplasty. Another reason for applying stent is it to treat dissections in blood vessel walls caused by balloon angioplasty of the coronary arteries as well as peripheral arteries and to improve angioplasty results by preventing elastic recoil and remodeling of the vessel wall. Two randomized multicenter trials have shown a lower restenosis rate in stent treated coronary arteries compared with balloon angioplasty alone (Serruys, P W et al. New England Journal of Medicine 331: 489-495, 1994, Fischman, D L et al. New England Journal of Medicine 331:496-501, 1994). Stents have been successfully implanted in the urinary tract, the bile duct, the esophagus and the tracheo-bronchial tree to reinforce those body organs, as well as implanted into the neurovascular, peripheral vascular, coronary, cardiac, and renal systems, among others. The term “stent” as used in this Application is a device that is intraluminally implanted within bodily vessels to reinforce collapsing, dissected, partially occluded, weakened, diseased or abnormally dilated or small segments of a vessel wall.  
         [0003]     One common procedure for intraluminally implanting a stent within a body vessel is to first dilate the relevant region of the vessel with a balloon catheter. Subsequently, a delivery catheter, such as Percutaneous Transluminal Coronary Angioplasty (PTCA) Catheters containing a dilator at the distal end thereof, is applied to transport a stent to the lesion site, and to deploy the stent in a position that bridges the affected portion of the vessel. The expanded stent provides scaffolding to the lumen that allows adequate blood flow within the lumen. These delivery catheters typically include a relatively long flexible shaft (e.g., normally about 145 cm in length that is sized to be percutaneously inserted into the vessels) with a dilator or stent deployment assembly at the distal end of the shaft that carries the stent.  
         [0004]     During any such catheterization and interventional procedures, including for example angioplasty and/or stenting, a hollow needle is initially applied through a patient&#39;s skin and tissue to facilitate advancement of the catheter shaft through the target vasculature. As is often the case, however, the catheter shaft may need to be inserted into vessels having a relatively tortuous path leading to the lesion site. Since it can be difficult to steer many types of catheters, guidewires are applied to facilitate advancement of the catheters through the vessel. Guidewires are typically formed from a very small diameter metallic wire having a flexible tip that can be rotatably controlled to some degree. The operator is shaping the tip of the guidewire by bending it depending on the anatomy of the vessel. Since the guidewire body is transmitting torque very well, the tip of the catheter can be steered through the anatomy of the patient. Furthermore steerable guidewires have been developed which allow the operator to deflect the tip of the wire actively in the vasculture of the patient. The ability to rotatably control the tip is important in that the guidewire can be steered to access a desired location through a potentially tortuous path such as the vasculature.  
         [0005]     Once the guidewire is advanced through the needle and into the patient&#39;s blood vessel, the needle is removed. An introducer sheath is then advanced over the guidewire into the vessel, e.g., in conjunction with or subsequent to a dilator. The catheter or other deployment device may then be advanced through a lumen of the introducer sheath and over the guidewire into a position for performing a medical procedure. Thus, the introducer sheath may facilitate introducing various devices into the vessel, while minimizing trauma to the vessel wall and/or minimizing blood loss during a procedure.  
         [0006]     In some applications, the targeted region of a vessel may be at a location where the vessel bifurcates. For example, in cases where plaque has developed in the region of a vessel bifurcation, it may be desirable to perform angioplasty, atherectomy, and/or stenting in one or all of the affected vessels. In general, it is very important to preserve the side branch and the main branch of the bifurcation. In some occlusions, it might occur that during the dilation, plaque will be shifted from the treated vessel to the non-treated vessel, and will then occlude that non-vessel. This effect is known as the “snowplow” effect. To enable re-access to the vessel that has been affected by the “snowplow” effect, most physicians prefer to place a guidewire in the non-treated branch as well. If the non-treated vessel is occluded during this procedure, the guidewire positioned in the non-treated vessel will function as a guiding element, and will allow the advance of another catheter to reopen that vessel. In other applications, it may be desirable to insert a bifurcation stent specifically dedicated to treat lesions at a vessel bifurcation.  
         [0007]     In the recent past, several commercially available bifurcation stents have been developed that treat bifurcation lesions. By way of example, common alternatives to bifurcation lesion stenting include the Elective T technique, the Provisional T Technique, the Coulotte Technique, the V Technique and the Crush. In addition, dedicated bifurcation systems like the Frontier and AST Systems has been developed. While these bifurcation stent designs have encountered varying degrees of success, one major problem associated with all bifurcation systems is that the delivery and deployment of the stent, relative to the side branch, is extremely difficult. This is due primarily to the difficulty in properly controlling the orientation, alignment and position of the stent deployment assembly relative to the main branch and side branch of the bifurcated vessel.  
         [0008]     During advancement of the catheter shaft along the predisposed guidewire, the stent deployment assembly, which supports and transports the stent in a collapsed state, is not rotatably controlled. Hence, it is likely necessary to rotate and reorient the distal delivery assembly about its&#39; longitudinal axis since the bifurcation stent must be properly aligned relative to the side branch before deployment. Current systems that require rotation of the delivery system many times result in less than ideal stent placement.  
         [0009]     Other types of delivery systems such as those that utilize two inflatable balloons disposed on the end of a catheter shaft have additional placement difficulties. Many times systems utilizing more than one balloon are tracked over two separate guidewires, wherein one guidewire is placed in the main branch and the second into the bifurcated branch. Problems associated with systems that utilize two separate guidewires have the potential for the two guidewires to become entangled and create difficulties in successful deployment of one or both stents because twists between the guidewires prevent the systems from tracking to the target treatment site, for example.  
         [0010]     Accordingly, there is a need for a stent delivery system with improved alignment and orientation capabilities of the distal stent deployment assembly for those stents (e.g., bifurcation stents) that require precise radial alignment relative to the target vessel site.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention is directed toward a stent delivery system for delivering and deploying a radially expandable stent at a strategic orientation and location in a body vessel.  
         [0012]     In accordance with the present invention there is provided a stent delivery system for delivering and deploying a radially expandable stent at a strategic orientation and location in a body vessel, said delivery system comprising: an elongated shaft; a first inflatable member extending from a distal end of the elongated shaft; a second inflatable member extending from the distal end of the elongated shaft and disposed adjacent to the first inflatable member, wherein the first and second inflatable members are in fluid communication with each other, and a tip assembly, the tip assembly including a first tip portion associated with the first inflatable member and a second tip portion associated with the second inflatable member, wherein the first and second tip portions are configured to be detachably associated with each other.  
         [0013]     In accordance with the present invention there is provided a method for placing an expandable endoprosthesis in a lumen, comprising: advancing an endoprosthesis delivery system over at least one guidewire to a location adjacent a bifurcation location, the guidewire extending through a tip assembly; advancing a second guidewire through the tip assembly; separating the tip assembly to form a first tip and a second tip, wherein the first tip is disposed about one of the guidewires and the second tip is disposed about the other guidewire; advancing the delivery system to the bifurcation location; and deploying the endoprosthesis.  
         [0014]     In accordance with an alternative embodiment of the present invention there is provided a delivery system configured to deploy an endoprosthesis at a bifurcation, the delivery system comprising 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The assembly of the present invention has other objects and features of advantage that will be more readily apparent from the following description of the best mode of carrying out the invention and the appended claims, when taken in conjunction with the accompanying drawing, in which:  
         [0016]      FIG. 1  is a plan view of an exemplary embodiment of a bifurcation delivery catheter in accordance with the present invention;  
         [0017]      FIG. 2  is a plan view of the distal end of the catheter of  FIG. 1  illustrating the tip design;  
         [0018]      FIG. 3  is an isometric view of an exemplary embodiment of a tip in accordance with the present invention;  
         [0019]      FIG. 4  is an isometric view of the tip assembly of  FIG. 3  wherein the tip assembly has been separated into a first tip and second tip;  
         [0020]      FIGS. 5A through 5D  are end views of the tip of  FIG. 3 , illustrating the separation process of the tip assembly as well as the advancement of the second guidewire in accordance with the present invention;  
         [0021]      FIGS. 6A through 6D  illustrate the delivery system of the present invention in use;  
         [0022]      FIG. 7  is a plan view of an alternative embodiment of a bifurcation delivery catheter in accordance with the present invention;  
         [0023]      FIG. 8  is a plan view of the distal end of the catheter of  FIG. 7  illustrating the tip design;  
         [0024]      FIG. 9  is an isometric view of an alternative embodiment of a tip in accordance with the present invention;  
         [0025]      FIG. 10  is an isometric view of the tip assembly of  FIG. 9  wherein the tip assembly has been separated into a first tip and second tip; and  
         [0026]      FIGS. 11A through 11D  illustrate the delivery system of the present invention in use. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]     While the present invention will be described with reference to a few specific embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications to the present invention can be made to the preferred embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims. It will be noted here that for a better understanding, like components are designated by like reference numerals throughout the various figures.  
         [0028]     In accordance with the present invention there is provided a catheter, wherein the catheter is configured to deliver and deploy at least one expandable member within a lumen. The catheter includes a first end, a second end and a shaft extending therebetween. At least one inflatable member is disposed adjacent the distal end and coupled to an inflation lumen extending through the shaft of the catheter, preferably at least two inflatable members are disposed adjacent the distal end, wherein each of the inflatable members includes a separate inflation lumen, thereby allowing independent inflation of the inflatable members. In use, the catheter is delivered within a lumen by tracking at least a portion of the catheter over a coaxial guidewire. The distal end is tracked to a location adjacent a bifurcation to be treated. The coaxial guidewire is activated to separate into a main branch guidewire and a side branch guidewire, either simultaneously or in response to the separation of the guidewires the distal tip of the catheter separates from one composite tip to two independent tips  
         [0029]     Referring now to  FIG. 1  there is shown an exemplary embodiment of the catheter in accordance with the present invention. As shown in  FIG. 1 , the catheter  10  has a proximal end  12 , a distal end  14  and a shaft  16  extending therebetween. A luer fitting  17  may be disposed adjacent the proximal end  12  of the shaft  16 . As shown in  FIG. 1 , the luer fitting includes an aperture  18  disposed therethrough, wherein the aperture  18  is in fluid communication with a lumen  11  (not shown) extending along the length of the shaft  16 . Lumen  11  is configured to receive at least one guidewire therethrough as will be described in greater detail below. The luer  17  may further include an inflation fitting  13 , wherein the inflation fitting is in fluid communication with at least one inflation lumen  20  (not shown) which extends along the length of the shaft  16 , wherein the inflation lumen  20  is in fluid communication with at least one inflatable member  30  disposed adjacent the distal end  14  of the shaft  16  as will be described in detail below.  
         [0030]     Disposed adjacent the distal end  14  of the shaft  16  is at least one inflatable member  30  as shown in  FIG. 1  and described above. Preferably, the catheter  10  in accordance with an exemplary embodiment of the present invention includes at least two inflatable members  30  disposed adjacent the distal end  14  of the shaft  20 . The inflatable members  30  are coupled to the shaft  16  through inflation lumens  20 , wherein the inflation lumens  20  extend along the length of the shaft  16  and are fluidly coupled to the inflation port  13  disposed on the luer  17 . The inflatable members  30  are in fluid communication with each respective inflation lumen, thereby being capable of being expanded from a first diameter to a second diameter. The distal ends of each of the inflation lumens terminate within the volume of the inflatable member, wherein mandrels  21  extend beyond a distal ends of each of the inflatable members and terminate at a tip member  40 . The tip member  40  is comprised of at least two components, wherein the two components interact to form a single tip as shown with a guidewire lumen  41  extending therethrough.  
         [0031]     As further shown in  FIG. 1 , the catheter  10  may be configured to receive a guidewire along its entire length within the guidewire lumen  11  disposed within the shaft  16 . Alternatively, as shown in  FIG. 1 , the catheter  10  may include at least one port  15  formed within the wall of the shaft  16  and in communication with the guidewire lumen  11 , wherein a guidewire may be placed within the port  15  and extended beyond the distal end of the shaft  16  as shown. Such a configuration is commonly referred to as a rapid-exchange catheter. It is further contemplated, that the catheter  10  may include a second port  19  adjacent the proximal end  12  of the shaft  16 , wherein the second port  19  is associated with the guidewire lumen  11 , wherein a guidewire  100  may be disposed thorough the port  19  and along the length of the shaft and through tip  40  of the catheter  10 . By allowing the guidewire to pass through the port  19  and not through the aperture  18  of the luer  17 , the aperture  18  may be utilized for other functions, such as a second inflation lumen.  
         [0032]     Referring now to  FIG. 2 , there is shown an exemplary embodiment of the distal tip of the catheter  10  in accordance with the present invention, wherein an endoprosthesis such as a stent is shown radially disposed about the first and second inflatable members  30 .  
         [0033]     Referring now to  FIG. 3 , there is shown an exemplary embodiment of a tip member  40  in accordance with the present invention. As shown in  FIG. 3 , the tip member  40  is a composite tip comprising a first tip member  42  and a second tip member  44 , wherein when coupled together form the tip member  40  having a lumen  41  extending therethrough.  
         [0034]     Referring now to  FIG. 4  there is shown the tip member  40 , wherein the first and second tip members  42  and  44  have been separated into two distinct tip members each having a lumen  45  and  43  disposed therethrough respectively. Each of the first and second tip members are fixedly attached to the distal mandrels,  21 , wherein when separated as shown in  FIG. 4 , the catheter  10  converts from a single tipped catheter to a dual tip catheter as will be described below with regard to the methods in accordance with the present invention. The bodies of the tip members  42  and  44  are preferably constructed having a generally cylindrical profile, wherein a slot is disposed extending along a longitudinal length of the bodies, wherein the slot enables the bodies to expand in diameter, thereby allowing the bodies of the tip members  42  and  44  to nest together as shown in  FIG. 3 . The tip members  42  and  44  are preferably constructed of a resilient pliable material, wherein the bodies are capable of flexing and/or be expanded about one another to nest together as shown in  FIG. 3 . Additionally, the tip members  42  and  44  must be constructed of a material which has a sufficiently low durometer such as to not cause damage to a lumen in which the catheter is disposed therein.  
         [0035]     Referring now to  FIGS. 5A  through SD there is shown the sequence of tip separation that occurs prior to placement of the distal tip of the catheter in a desired location. Referring now to  FIG. 5 , there is shown a cross-sectional view of the composite tip assembly  40  in accordance with the present invention. As show, the composite tip assembly  40  comprises a first tip member  42  and a second tip member  44 , wherein the first tip member  42  is radially received within a lumen of the second tip member  44 . Additionally as shown, a guidewire is shown disposed through the aperture  41  of the tip assembly  40 .  
         [0036]     Referring now to  FIG. 5B  there is shown a cross-sectional view of the composite tip assembly  40  in accordance with the present invention wherein the two tip portions  42  and  44  are beginning to separate. It can be seen that the second tip portion  44  is partially expanded about the first tip portion  42 . Additionally as shown in  FIG. 5B , a second guidewire  102  is extended from a lumen of the first guidewire  100 .  
         [0037]     Referring now to  FIG. 5C  there is shown a cross-sectional view of the composite tip assembly  40  in accordance with the present invention wherein the two tip portions  42  and  44  are almost completely separated and wherein the second guidewire  102  has been extended from a lumen of the first guidewire  100 .  
         [0038]     Referring now to  FIG. 5D  there is shown an end view of the composite tip assembly  40  in accordance with the present invention wherein the two tip portions  42  and  44  have been completely separated from each other to form two distinct tips. Additionally, as shown, the first guidewire  100  and the second guidewire  102  are each captured within a tip portion  42  and  44  respectively. Additionally, it can be seen that the first and second tip portions  42  and  44  resiliently close about the respective guidewire disposed therethrough, thus enabling the guidewire to be used as a guide for the tip portions  42  and  44 .  
         [0039]     It shall be understood that tip assembly  40  as shown herein and described above is an exemplary embodiment of a tip assembly. It is contemplated that various modifications may be made to the geometry and/or the material selection of the tip in order to enable similar functionality as described above. In accordance with an alternative embodiment, the tip assembly  40  may comprise at least two tip portions which are disposed adjacent to one another in longitudinal alignment, wherein the two tip portions may or may not be detachably coupled to each other.  
         [0000]     Methods of Use  
         [0040]     Referring now to  FIGS. 6A through 6D  there is shown an exemplary embodiment of a method of use of the catheter  10  in accordance with the present invention to deploy an endoprosthesis at a bifurcation location or adjacent to a bifurcation location. p Referring now to  FIG. 6A  there is shown the distal tip portion of the catheter  10  in accordance with the present invention. As shown in  FIG. 6A  an expandable medical device  300  is shown disposed radially about the inflatable members  30 . A guidewire  100  is shown disposed through at least a portion of guidewire lumen of the catheter shaft and through the tip assembly  40 . As shown, the distal end of the catheter  10  is placed adjacent to a bifurcation in a lumen such as a vessel or artery.  
         [0041]     Referring now to  FIG. 6B  there is shown the distal tip of the catheter  10  in accordance with the present invention, wherein the tip assembly  40  has been separated into two tips  42  and  44 . Additionally as shown in  FIG. 6B  and described above, a second guidewire  102  is advanced from a portion  101  of the first guidewire  100 . Each of the tips  42  and  44  are guided to a desired location by their respective guidewires.  
         [0042]     Referring now to  FIG. 6C  the distal end of the catheter  10  has been advanced further into the lumen, wherein each of the guidewires respectively guides tips  42  and  44  along the main branch of the lumen and along the side branch of the lumen. Additionally, as shown in  FIG. 6C , the inflatable members  30  have been inflated after the expandable endoprosthesis has been properly positioned with respect to the geometry of the main branch and the side branch of the lumen.  
         [0043]     Referring now to  FIG. 6D  there is shown the expanded endoprosthesis  300  as placed in the lumen adjacent the side branch, wherein the catheter  10  has been removed but the guidewires  100  and  102  remain in position in the lumen. An advantage of the present system over previous systems is the present system allows for the placement of an expandable endoprosthesis as shown and described above while maintaining guidewires in the main branch and the side branch of the vessel. If desired, additional medical devices may then be placed over the guidewire to perform additional medical procedures. Further still, in the event of plaque shift or rupture in either the main branch or of the side branch of the vessel, by having the guidewire remain in the respective branch during the procedure enables a user to re-access the site easily.  
         [0044]     An additional advantage of the present system over previous systems is the present system is capable of working in conjunction with a coaxial guidewire, which allows for placement of a guidewire within each of the branch vessels without creating twists between the guidewires.  
         [0045]     In accordance with the present invention, it is contemplated that although the present invention was described in use with a guidewire  100 , wherein the guidewire  100  is a coaxial guidewire having an opening  101  and a second guidewire  102  disposed slidably therein, it is contemplated that the catheter  10  as shown and described and the method shown and described herein may be completed by utilizing two separate guidewires.  
       Alternate Embodiment  
       [0046]     In accordance with the present invention an alternative embodiment of a delivery catheter will be described in detail with reference to  FIGS. 7-11D . In accordance with the alternative embodiment of the present invention there is provided a catheter, wherein the catheter is configured to deliver and deploy at least one expandable member within a lumen. The catheter includes a first end, a second end and a shaft extending therebetween At least one inflatable member is disposed adjacent the distal end and is coupled to an inflation lumen extending through the shaft of the catheter, preferably at least two inflatable members are disposed adjacent the distal end, wherein each of the inflatable members includes a separate inflation lumen, thereby allowing independent inflation of the inflatable members.  
         [0047]     In use, the catheter is delivered within a lumen by tracking at least a portion of the catheter over a first guidewire. The distal end is tracked to a location adjacent a bifurcation within a lumen to be treated. A second guidewire is advanced through at least a portion of the catheter to a point distal to the inflatable members, at which point, the distal tip of the catheter separates from one composite tip to two independent tips. Preferably, the distal tips each become associated with a respective guidewire and are tracked to a location adjacent a bifurcation to be treated, where an endoprosthesis can then be deployed in response to inflation of the inflatable members.  
         [0048]     The delivery system in accordance with the alternative embodiment differs from that described above, in that the guidewire lumens disposed through each of the inflatable members extends distally through the inflatable members and terminates at the distal tip location, wherein the catheter in accordance with the alternative embodiment can be delivered to a bifurcation site over a single guidewire, wherein a second guidewire can then be deployed into the branch lumen of the bifurcation. Unlike the delivery system described above, the delivery system of the alternative embodiment does not require the use of a special guidewire in order to place the system within the bifurcation.  
         [0049]     Referring now to  FIG. 7  there is shown an exemplary embodiment of the alternative embodiment of a catheter in accordance with the present invention. As shown in  FIG. 7 , the catheter  50  has a proximal end  52 , a distal end  54  and a shaft  56  extending therebetween. A luer fitting  57  is disposed adjacent the proximal end  52  of the shaft  56 . As shown in  FIG. 7 , the luer fitting includes an aperture  58  disposed therethrough, wherein the aperture  58  is in fluid communication with at least one lumen  51  (not shown) extending along the length of the shaft  56 . Lumen  51  is configured to receive at least one guidewire therethrough as will be described in greater detail below. The luer  57  may further include an inflation fitting  53 , wherein the inflation fitting is in fluid communication with at least one inflation lumen  60  which extends along the length of the shaft  56 , wherein the inflation lumen  60  is in fluid communication with at least one inflatable member  70  disposed adjacent the distal end  54  of the shaft  56  as will be described in detail below.  
         [0050]     Disposed adjacent the distal end  54  of the shaft  56  is at least one inflatable member  70  as shown in  FIG. 7  and described above. Preferably, the catheter  50  includes at least two inflatable members  70  disposed adjacent the distal end  54  of the shaft  56 . The inflatable members  70  are coupled to the shaft  56  through inflation lumens  60 , wherein the inflation lumens  60  extend along the length of the shaft  56  and are fluidly coupled to the inflation port  53  disposed on the luer  57 . The inflatable members  70  are in fluid communication with each respective inflation lumen, thereby being capable of being expanded from a first diameter to a second diameter. The distal guidewire lumens  61  extend beyond a distal end of each of the inflatable members and terminate at a tip assembly  80 .  
         [0051]     As further shown in  FIG. 7 , the catheter  50  may be configured to receive a guidewire along its entire length within each of the guidewire lumens  61  disposed within the shaft  56 . Alternatively, as shown in  FIG. 7 , the catheter  50  may include at least one port  55  formed within the wall of the shaft  56  and in communication with the guidewire lumen  61 , wherein a guidewire may be placed within the port  55  and extended beyond the distal end of the shaft  56 , as shown. Such a configuration is commonly referred to as a rapid-exchange catheter. It is further contemplated, that the catheter  50  may include a second port  59  adjacent the proximal end  52  of the shaft  56 , wherein the second port  59  is associated with a guidewire lumen  61 , wherein a guidewire  500  may be disposed through the second port  59  and along the length of the shaft and through tip assembly  80  of the catheter  50 . By allowing the guidewire to pass through the second port  59  and not through the aperture  58  of the luer  57 , the aperture  58  may be utilized for other functions, such as a second inflation lumen.  
         [0052]     Referring now to  FIG. 8 , there is shown an exemplary embodiment of the distal tip of the catheter  50  in accordance with the present invention, wherein an endoprosthesis  600  such as a stent is shown radially disposed about the first and second inflatable members  70 .  
         [0053]     Referring now to  FIG. 9 , there is shown an exemplary embodiment of a tip member  80  in accordance with the present invention. As shown in  FIG. 9 , the tip assembly  80  is a composite tip comprising a first tip member  82  and a second tip member  84 , wherein the first and second tip members maybe detachably coupled together to form the composite tip assembly  80  as shown. Tip members  82  and  84  are fixedly attached to the distal ends of each of the guidewire lumens  61   a  and  61   b  respectively.  
         [0054]     Referring now to  FIG. 10  there is shown the tip assembly  80 , wherein the first and second tip members  82  and  84  have been separated into two distinct tips each having a guidewire lumen  61   a  and  61   b  disposed therethrough respectively. Each of the first and second tip members are fixedly attached to their respective guidewire lumens  61   a  and  61   b , wherein when separated as shown in  FIG. 10 , the catheter  50  converts from a single tipped catheter to a dual tip catheter as will be described below with regard to the methods in accordance with the present invention.  
         [0055]     The body of tip member  82  is preferably constructed having a generally cylindrical profile, wherein its length is at least as long as tip member  84  to act as the leading tip while tracking over the guidewire. The body of tip member  84  includes a slot that is disposed extending along a longitudinal length of the body, and a slot that is disposed extending along a radial length of the body, the radial slot beginning at the termination of the longitudinal slot and extending in both radial directions, wherein the slots enable the bodies to expand in diameter, thereby allowing the body of the tip member  82  to nest within the tip member  84  as shown in  FIG. 9 . The tip members  82  and  84  are preferably constructed of a resilient pliable material, wherein the bodies are capable of flexing and/or expanding about one another to nest together as shown in  FIG. 9 . Additionally, the tip members  82  and  84  must be constructed of a material which has a sufficiently low durometer such as to not cause damage to a lumen in which the catheter is disposed therein.  
         [0056]     Referring now to  FIGS. 11A through 11D  there is shown an exemplary embodiment of a method of use of the catheter  50  in accordance with the present invention to deploy an endoprosthesis at a bifurcation location or adjacent to a bifurcation location.  
         [0057]     Referring now to  FIG. 11A  there is shown the distal tip portion of the catheter  50  in accordance with the present invention. As shown in  FIG. 11A  an expandable endoprosthesis  600  is shown disposed radially about the inflatable members  70 . A guidewire  500  is shown disposed through guidewire lumen  61  a of the catheter shaft and through the tip assembly  80 . As shown, the distal end of the catheter  50  is placed adjacent to a bifurcation in a lumen such as a vessel or artery.  
         [0058]     Referring now to  FIG. 11B  there is shown the distal tip of the catheter  50  in accordance with the present invention, wherein the tip assembly  80  has been separated into two tips  82  and  84 . Additionally as shown in  FIG. 11B  and described above, a second guidewire  502  is advanced through guidewire lumen  61   b  from a point proximal to the inflatable member. After reaching the tip assembly  80 , the second guidewire forces tip member  84  to increase in diameter, thereby decoupling tip member  84  from tip member  82 . After becoming decoupled, tip member  84  then relaxes, leaving the second guidewire  502  nesting within the tip member  84 . Each of the tips  82  and  84  are guided to a desired location by their respective guidewires.  
         [0059]     Referring now to  FIG. 11C  the distal end of the catheter  50  has been advanced further into the lumen, wherein each of the guidewires respectively guides tips  82  and  84  along the main branch of the lumen and along the side branch of the lumen. Additionally, as shown in  FIG. 11C , the inflatable members  70  have been inflated after the expandable endoprosthesis  600  has been properly positioned with respect to the geometry of the main branch and the side branch of the lumen.  
         [0060]     Referring now to  FIG. 11D  there is shown the expanded endoprosthesis  600  as placed in the lumen adjacent the side branch, wherein the catheter  50  has been removed but the guidewires  500  and  502  remain in position in the lumen. An advantage of the present system over previous systems is the present system allows for the placement of an expandable endoprosthesis as shown and described above while maintaining guidewires in the main branch and the side branch of the vessel. If desired, additional medical devices may then be placed over the guidewires to perform additional medical procedures. Further still, in the event of plaque shift or rupture in either the main branch or the side branch of the vessel, by having the guidewires remain in the respective branch during the procedure enables a user to re-access the site easily.  
         [0061]     The invention is susceptible to various modifications and alternative forms, and specific examples thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the invention is not to be limited to the particular forms or methods disclosed, but to the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the claims.