Patent Publication Number: US-2011054438-A1

Title: Stent delivery at a bifurcation, systems and methods

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to intravascular catheter devices and stents. More particularly, the present invention describes catheters, systems and assemblies, as well as methods for delivery of stents or scaffolds at bifurcations, e.g., for repairing diseased blood vessels at a bifurcation. 
     Intravascular stents or scaffolds are used for various purposes, including opening occluded blood vessels. In a typical approach, a stent is provided in a contracted form, e.g., disposed surrounding a deflated balloon positioned inside the stent. The stent and balloon are positioned at a distal portion of a catheter device, and a physician or operator inserts a guidewire into the lumen or blood vessel, and then slides the catheter over the wire to position the stent in the desired location. The stent is then expanded, e.g., via balloon expansion, so that the stent is anchored in place to hold the vessel open. Once the stent has been expanded, the balloon is deflated and the catheter withdrawn from the blood vessel. Treatment can also be combined with therapeutic agents or pharmaceuticals to improve healing and/or prevent restenosis. 
     Repairing blood vessels at a bifurcation has been particularly challenging for several reasons, including the need for an accurate and deliberate positioning of the stent in a precise location that provides adequate coverage of the diseased area, but while maintaining blood vessel patency and allowing adequate blood flow through the vessels at or downstream of the treatment site. Prior treatment using conventional tubular or cylindrical stents has presented a variety of problems. For example, conventional stents have been deployed so that either the entire stent is in the main lumen upstream of the bifurcation, or the proximal portion of the stent is positioned in the main lumen upstream of the bifurcation, while the distal portion is located entirely or unevenly in a downstream branch vessel. In the former case, the stent is often not advanced distally enough to provide the desired coverage of the diseased area. In the latter instance, vessel repair often comes at the expense of obstructing or failing one of the branch lumens or downstream vessels. Another approach has included positioning of multiple different stents at different locations in the bifurcation. Besides conventional cylindrical stents, more elaborate designs, such as bifurcated stents, have become available. Use of such non-conventional stents, however, like the use of multiple conventional stents, undesirably increases the complexity and invasiveness of the treatment. 
     Thus, a need exists for improved methods and systems for delivery of stents or scaffolds at bifurcations, thereby providing more efficient and effective repair of diseased blood vessels at a bifurcation. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides systems and methods for delivery of a stent or scaffold at a body lumen or blood vessel bifurcation in a patient and, more particularly, repairing diseased blood vessels at a bifurcation. A system includes a first scaffold deployment catheter with at least one balloon located on a distal portion of the catheter. A non-bifurcated or standard tubular scaffold or stent is used, and is placed so that a proximal portion of the scaffold is over a balloon and a distal portion is over a balloon or extends distal to a balloon. The catheter includes one or more guidewire lumens, and the catheter can be delivered over one or more guidewires so that the end of the catheter enters into the bifurcation and the distal end of the scaffold diverges or spreads over the carina. The balloon(s) may then be expanded to open and anchor the proximal portion of the scaffold. The first catheter is then withdrawn and a second expansion system, such as a pair of kissing balloons or single bifurcated balloon, is advanced into position and expanded to deploy the distal portion of the scaffold. 
     The systems and methods of the present invention may provide numerous advantages, including a more simplified system using a standard tubular scaffold or stent, compared to approaches requiring delivery of numerous stents, advancing guidewires though the struts of delivered stents, or use of stents of more elaborate design, such as bifurcated stents. The present techniques further provide for advancement of the distal portion of the scaffold deeper into the bifurcation so that the delivered scaffold covers the outer flank of the bifurcation where the diseased portion is most prevalent, while the inner carina is usually open and does not need scaffold coverage. Guidewires are maintained in both branch lumens throughout the stent delivery procedure. 
     Thus, in one aspect, the present invention includes systems and methods for positioning a cylindrical scaffold at a bifurcation of a main lumen into first and second branch lumens. A method can include positioning a scaffold at a bifurcation of a main lumen into first and second branch lumens, including advancing a first balloon catheter system to the bifurcation. The first catheter system can include at least one main balloon with a scaffold positioned over the main balloon(s), or partly over the main balloon(s) and partly distal to the main balloon(s). The main balloon catheter system is advanced until the distal portion of the scaffold has entered the bifurcation, and the main balloon(s) is/are inflated to expand the proximal portion of the scaffold on a generally proximal side of the bifurcation while the distal portion of the scaffold remains partially or substantially unexpanded. Further, a second scaffold expansion system is introduced, e.g., following main catheter withdrawal, and expanded or balloon inflated to expand the distal portion of the scaffold on a generally distal side of the bifurcation. Thus, the proximal portion of the scaffold and the distal portion of the scaffold can be expanded in seriatim. 
     In another aspect, a method includes placing a first guidewire from the main lumen into the first branch lumen and a second guidewire from the main lumen into the second branch lumen. Following positioning of the first and second guidewires, a main balloon catheter is advanced over at least one guidewire. The scaffold can be coupled with the main balloon catheter such that a proximal portion of the scaffold is positioned over a balloon and a distal portion of the scaffold is positioned over a balloon or distally of a balloon. The balloon catheter is advanced until the distal portion of the scaffold has entered the bifurcation. Following positioning the scaffold in the bifurcation, the main balloon(s) is/are inflated to expand the proximal portion of the scaffold on a generally proximal side of the bifurcation while the distal portion of the scaffold remains partially or substantially unexpanded. The main balloon is removed from the bifurcation, and first and second balloon catheters are introduced over a first guidewire from the main lumen into the first branch lumen and over a second guidewire from the main lumen into the second branch lumen, respectively, so that said first and second balloons are positioned, e.g. side-by-side, within the distal portion of the scaffold. Following introduction of the first and second balloons, the balloons are inflated to expand the distal portion of the scaffold on a generally distal side of the bifurcation. 
     In another aspect, the present invention includes scaffold delivery catheters and systems. A catheter can include a catheter body having a distal end, a proximal end, and at least one guidewire lumen extending to the distal end, at least one main inflatable balloon disposed on the catheter body at a predetermined distance proximally of the distal end. The catheter can further include a cylindrical scaffold having a proximal portion disposed over an inflatable balloon and a distal portion disposed over a balloon or distally of an inflatable balloon. The scaffold can be disposed over a balloon such that inflation of one or more inflatable balloon(s) will expand the proximal portion while leaving the distal portion of the scaffold partially or substantially unexpanded. Guidewire assemblies suitable for use with catheters and techniques described herein are further provided. 
     For a fuller understanding of the nature and advantages of the present invention, reference should be made to the ensuing detailed description and accompanying drawings. Other aspects, objects and advantages of the invention will be apparent from the drawings and detailed description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A through 1C  provide a simplified illustration of scaffold positioning at a bifurcation including a main vessel lumen and branch lumens, according to an embodiment of the present invention. 
         FIG. 2  illustrates a balloon catheter with a bifurcated distal portion and a scaffold positioned on the catheter, according to an embodiment of the present invention. 
         FIGS. 3A through 3D  illustrate scaffold positioning at a bifurcation, according to an embodiment of the present invention. 
         FIGS. 4A through 4F  illustrate scaffold positioning at a bifurcation, according to yet another embodiment of the present invention. 
         FIG. 5  illustrates a balloon catheter having a non-bifurcated distal portion and a scaffold positioned on the catheter, according to an embodiment of the present invention. 
         FIG. 6  shows a balloon catheter having a bifurcated distal portion and a scaffold positioned on the catheter, and further having a first and second guidewire coupled with the catheter, according to an embodiment of the present invention. 
         FIGS. 7A and 7B  illustrate embodiments of balloon catheters having a bifurcated distal portion, according to embodiments of the present invention.  FIG. 7A  shows a catheter having a balloon encircling both first and second guidewire lumens.  FIG. 7B  shows a catheter having a balloon encircling a first guidewire lumen with a second guidewire lumen disposed opposite an outer surface of the balloon. 
         FIGS. 8A and 8B  illustrate a balloon catheter having a scaffold positioned over a balloon, the catheter coupled with a guidewire assembly and further coupled with a retractable sheath, in accordance with further embodiments of the present invention. 
         FIGS. 9A and 9B  illustrate a balloon catheter having a scaffold positioned over a balloon, where the balloon is configured for a rolling-type movement along a longitudinal length of the catheter. 
         FIGS. 10A and 10B  illustrate an exemplary guidewire assembly according to an embodiment of the present invention, including a first guidewire having a lumen and a second guidewire sized for positioning and advancement through the first guidewire lumen. 
         FIGS. 11A and 11B  illustrate a guidewire assembly according to an exemplary embodiment of the present invention, the assembly including a first guidewire having a lumen extending distally to a side opening and a second guidewire sized for positioning and advancement in the lumen. 
         FIGS. 12A and 12B  illustrate yet another guidewire assembly according to an exemplary embodiment of the present invention, the assembly including guidewires having a generally cylindrical distal portion and a proximal portion having a “D-shaped” cross-sectional geometry. 
         FIGS. 13A and 13B  illustrate a balloon catheter having a scaffold positioned over a balloon, the balloon encircling one of two guidewire lumens, and the inflated diameter of the proximal portion of the balloon greater than the inflated diameter of the distal portion of the balloon 
         FIGS. 14A and 14B  illustrate a balloon catheter having a scaffold positioned over two balloons on two guidewire lumens. The proximal balloon has a larger inflated diameter than the distal balloon. 
         FIGS. 15A and 15B  illustrate a balloon catheter having a scaffold positioned over a balloon and two guidewire lumens, whereby the balloon catheter and scaffold is advanced into the vessel and close to the bifurcation in part over one guidewire lumen and in part over the other guidewire lumen 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides systems and methods for delivery of a stent or scaffold at a blood vessel or body lumen bifurcation, e.g., for repairing diseased blood vessels at a bifurcation in a patient. A bifurcation can include, e.g., a region of a vessel or lumen at or near a point where division of two or more branches occurs. A bifurcation as referred to herein can include a generally symmetric or, more typically, generally asymmetric bifurcation. The systems and methods of the present invention deliver a staged deployment or expansion of a tubular scaffold or stent, or stent/scaffold generally non-bifurcated in having an end with a single opening rather than a plurality of different openings. According to the present invention, a scaffold can be more optimally advanced and positioned into the bifurcation such that the delivered scaffold covers the outer flank of the bifurcation where the diseased portion may be most prevalent. 
       FIGS. 1A through 1C  include a simplified side view illustrating general aspects of scaffold positioning at a bifurcation according to an embodiment of the present invention. The scaffold and positioning thereof is shown sans catheters for clarity. Non-limiting, exemplary catheter systems are described further below. Scaffold  10  is advanced, e.g., over an expandable balloon catheter system, through the vasculature of a patient and is aligned adjacent to or approaches the bifurcation of a main lumen  12  into branch lumens  14  and  16 . The scaffold  10  includes a simple cylindrical or tubular shaped scaffold or stent, including a proximal portion  18  and a distal portion  20 . The scaffold  10  is entered into the bifurcation (e.g., aligned adjacent to or approaches the bifurcation), and may be positioned such that the distal end of the scaffold diverges or spreads over the carina  22 , and at least partially into one or more branch lumens. The scaffold  10  is then expanded and positioned, or anchored, to the lumen wall in a staged manner. Expansion and scaffold positioning includes a first expansion where a proximal portion  18  of the scaffold is deployed ( FIG. 1B ), followed by expansion or deployment of a distal portion  20  of the scaffold ( FIG. 1C ). 
     The terms “stent” and “scaffold” are generally used interchangeably herein, and include any of the array of expandable (e.g., balloon expandable) prostheses and scaffolds which are introduced into a lumen at a target treatment site and expanded in situ to exert a radially outward force against the lumen wall for positioning or anchoring in the lumen wall at the treatment site. Any number of scaffold or stent configurations may be employed in the systems of the present invention. The scaffolds or stents of the present invention can include a closed or an open lattice structure, and will typically be fabricated from a malleable or elastic material. Malleable materials such as stainless steel, gold, platinum, titanium, cobalt chromium and other alloys or bioabsorbable materials such as polymers may be selected for stent composition, and scaffolds are typically expanded by balloon inflation, causing deformation of the lattice so that it remains deformed in an open position after deployment. Particular patterns, such as ring and link patterns, element dimensions and material composition can be selected to accommodate a particular application including, but not limited to, variations in length, expanded diameter, coverage, flexibility, resorbability, and/or the like. Scaffolds will typically include a length of about 6 mm to about 38 mm. As described further herein, scaffolds can be disposed on a balloon of a catheter such that the proximal portion of the scaffold is positioned on a balloon with the distal portion of the scaffold is either on a balloon or extends distally to a balloon. In the embodiments with a distal portion of the scaffold extending distally to a balloon, the portion of a cylindrical scaffold disposed distally of an inflated balloon will typically have a length in the range of about 2 mm to about 12 mm. Scaffolds may also be coated with one or more compositions such as a therapeutic agent or drug (e.g., anti-restenosis drug), including those known in the art. Deployment of a scaffold is typically described herein in the context of a coronary artery stent procedure, but it should be understood that the invention may be employed in any variety of blood vessels and other body lumens in which stents or tubular scaffolds are deployed. 
     Various catheter systems, scaffold delivery catheters, including balloon catheters, and designs may be employed for scaffold delivery as described herein, and non-limiting exemplary systems and designs are described further herein. Catheter systems can be configured in a conventional manner in the sense that they can be configured for use with one or more guidewires, and will typically include an internal guidewire lumen for receiving a guidewire. Deployment catheters and catheter systems of the present invention can rely on any of a number of guidewire configurations, including rapid exchange, over-the-wire, or a combination of both. While certain exemplary embodiments described herein may be illustrated with a particular guidewire configuration, it will be recognized that additional guidewire configurations are included within the scope of the present invention. Additionally, balloon catheters as described herein will include an inflation lumen through which the balloon is inflated and deflated. Catheter balloons can vary in design or sizing, and may be selected at least partially on the intended use and/or treatment requirements. Catheter balloons, for example, will typically range from about 4 mm to about 26 mm in length. Catheters may further include one or more markers, such as radiopaque markers, to facilitate tracking of the device during an interventional procedure. 
     A bifurcation scaffold delivery system according to an embodiment of the present invention is illustrated with reference to  FIG. 2 . The catheter system  30  includes a first scaffold deployment catheter  32 , configured for initial positioning of the scaffold  34  at a desired location in a bifurcation at a first stage, where the scaffold  34  is advanced to a bifurcation and the proximal portion of the scaffold is expanded. The catheter  32  includes a bifurcated distal portion  35  and a balloon  36  located proximally of the bifurcation  35 . Each of the bifurcations include a guidewire lumen  38 ,  40 . A non-bifurcated scaffold (e.g., standard tubular stent) is positioned on the catheter balloon  36 , the scaffold  34  including a proximal portion  44  and a distal portion  46 . The scaffold  34  is disposed such that the proximal portion  44  is positioned over the balloon  36  and the distal portion  46  is positioned distally of the balloon  36  and over the bifurcation  35 . 
     Positioning a scaffold within a bifurcation using a system similar to the one described in  FIG. 2  above, is described with reference to  FIGS. 3A through 3D . The system can be advanced to the bifurcation  48  or treatment site via advancement over one or more guidewires  50 ,  52  positioned in the lumen(s). As described above, the system includes a scaffold deployment catheter  32 , designed for advancement through the main lumen  54  and into the bifurcation and branch lumens  56 ,  58 . The catheter includes a main balloon  36  located proximally of a bifurcated distal end. The distal end includes guidewire lumens  38 ,  40 . During at least initial positioning, one or more guidewires  50 ,  52  can be advanced through the main lumen and into one or more of the branch lumens. Where a dual guidewire configuration is used, a first guidewire  50  is advanced through the main lumen and into branch lumen  56 , and a second guidewire  52  is similarly advanced through the main lumen and into branch lumen  58 . The guidewires  50 ,  52  can be advanced and positioned in seriatim or substantially at the same time. With one or more guidewires positioned in the bifurcation, the catheter  32  can be advanced over one of the guidewires  50 ,  52 , or both. For example, in one embodiment, both guidewires  50 ,  52  are advanced and positioned in branch lumens  56 ,  58 , respectively, and the catheter  32  is loaded over such that the guidewires  50 ,  52  are run through lumens  38 ,  40 , respectively. 
     In another embodiment, a first guidewire is advanced into a branch lumen and the catheter is loaded over the guidewire and advanced to the bifurcation, while a second guidewire can be loaded into the catheter prior to advancement and positioning and advanced along with the catheter (e.g., similar to examples described further below). In yet another embodiment, the catheter is advanced over a first positioned guidewire, and once the catheter is positioned at or near the bifurcation, a second guidewire can be advanced through a lumen of the catheter and then further into the second branch lumen. Various embodiments of guidewire use and positioning can be utilized in conjunction with scaffold positioning according to the present invention, and certain such embodiments are described further herein. 
       FIG. 3A  illustrates initial positioning of the catheter and scaffold system within the bifurcation. With guidewires  50 ,  52  running through the main lumen  54  and into branch lumens  56 ,  58 , respectively, distal advancement of the catheter sends guidewire lumens  38 ,  40  of the catheter  32  into respective branch lumens of the bifurcation. As illustrated, with distal advancement of the catheter, branch lumens  38 ,  40  diverge slightly or flare out over the carina and permit advancement of the scaffold  34  such that distal portion of the scaffold is advantageously positioned deeper within the bifurcation. Next, the balloon  36  of the catheter is inflated so as to deploy the proximal portion  44  of the scaffold in the vessel or lumen immediately upstream or proximal of the bifurcation ( FIG. 3B ). The catheter  32  can then be withdrawn and a second deployment system including balloons  60 ,  62  can be advanced over guidewires  50 ,  52  and positioned in the bifurcation and at least partially into lumens  56 ,  58 , as shown in  FIG. 3C . Balloons  60 ,  62 , can be generally short (e.g., about 4 mm to about 10 mm in length) balloons, with inflated diameter selected or matched relative to the diameter of each downstream vessel or lumen. Balloons  60 ,  62  can be advanced substantially simultaneously into position, or one at a time. Once in position, balloons  60 ,  62  can be inflated (e.g., simultaneously inflated) to deploy the distal portion  46  of the scaffold ( FIG. 3D ). Thus, as illustrated, the scaffold is positioned and then deployed in a staged manner, with the proximal portion of the scaffold (e.g., generally the proximal about ½ to about ¾ portion of the scaffold) deployed by inflation of balloon  36  of the catheter, and then the distal portion of the scaffold (e.g., the distal approximately ¼ to about ½ portion of the scaffold) is deployed via inflation of balloons  60 ,  62 , as illustrated above. 
     As discussed above, a catheter system of the present invention can be advanced to a bifurcation over a single guidewire configuration or more than one guidewire. In one embodiment, a two-wire system can be utilized, with the scaffold delivery system advanced over a first guidewire with a second wire “loaded” on the catheter. Referring now to FIG.  4 A, a two-wire catheter  70  or scaffold delivery system is advanced in a body lumen including a main lumen and branch lumens. The catheter  70  includes a main balloon  72  located proximally of a bifurcated distal end  74 . A non-bifurcated scaffold  75  or stent (e.g., standard tubular stent) is positioned on the catheter, the scaffold including a proximal portion and a distal portion, with the proximal portion positioned over the balloon and the distal portion positioned distally of the balloon. The catheter further includes guidewire lumens  76 ,  78 , with the distal portion of guidewire lumen  76  including a tapered nose-cone, which can be shaped and/or composed of a material (e.g., soft elastomeric material) selected to minimize trauma to the vessel during advancement of the catheter. Guidewires  82  and  84  are positioned to extend through the main lumen and into respective branch lumens. Guidewires  82  and  84  maintain branch vessel access and may be used for pre-dilation of the bifurcation with standard balloon catheters, prior to advancing the scaffold delivery system  70  into the vessel. The catheter is advanced over guidewire  82 , which runs through lumen  76 , while a second guidewire  86  is “loaded” on the catheter, or positioned in lumen  78  without extending substantially out the distal end of lumen  78 , as shown in  FIG. 4A . Once the delivery system is advanced to a location just upstream of the bifurcation, the loaded wire  86  can be advanced into a downstream branch ( FIG. 4B ). Once guidewire  86  is advanced into a downstream branch, guidewire  84  can be removed. With guidewires  82  and  86  advanced in branch lumens, the delivery catheter can then be advanced further into the bifurcation (e.g., a final few mm) so that the distal portion of the scaffold enters into the bifurcation, and may be partly flared or splayed on the wires  82 ,  86 , as shown in  FIG. 4C . Balloon  72  is expanded so as to deploy the proximal portion of the scaffold  75  ( FIG. 4D ). The catheter  70  is then withdrawn, leaving guidewires  82  and  86  in position ( FIG. 4E ). Balloons  88  and  90  are then advanced over wires  82  and  86 , and into respective branch lumens, for inflation and deployment of the distal portion of the scaffold  75  ( FIG. 4F ). 
     A scaffold delivery system according to another embodiment of the present invention is illustrated with reference to  FIG. 5 . The system includes a scaffold deployment catheter  100  including a proximal portion and a distal portion. The distal portion includes a guidewire lumen  102  extending through the catheter elongated body and a main balloon  104 . The guidewire lumen  102  in the illustrated embodiment includes a non-bifurcated distal portion that is more truncated in comparison to other embodiments described herein. While the catheter is illustrated as having a single guidewire lumen, alternate embodiments can include more than one guidewire lumen. The guidewire lumen can be sized to accommodate a single guidewire, or multiple guidewires, or one or more guidewires of a variety of sizes. The system further includes a tubular or non-bifurcated scaffold  106  positioned on the catheter. The scaffold  106  includes a proximal portion and a distal portion, with the scaffold  106  disposed on the catheter such that the proximal portion is over the balloon  104  and the distal portion is positioned distally of the balloon  104 . The catheter  100  can be advanced over one or more guidewires, including, for example, over a guidewire having a bifurcated portion, for positioning of the scaffold at a lumen bifurcation as described further herein. 
       FIG. 6  shows a scaffold delivery system or catheter system according to an embodiment of the present invention, and illustrates a coupling of the delivery system with guidewires where the catheter can be advanced over a first guidewire, with a second guidewire loaded on the catheter. The system includes a catheter  110  having a proximal portion and a distal portion, the distal portion having a bifurcation with lumens  112  and  114  extending along a length of the catheter body and forming a bifurcated distal portion. Lumen  112  further includes a tapered nose-cone  116 , and extends more distally relative to lumen  114 . The system further includes a balloon  118  disposed on the body of the catheter  110 , and scaffold  120  having a proximal portion and distal portion. In use, the first guidewire  122  can be advanced through a body lumen of the patient and positioned at a desired location with respect to a bifurcation or treatment site. The catheter is then advanced over the guidewire and into position. While being advanced, the second guidewire  124  can be positioned loaded onto the catheter and disposed at least partially in lumen  114 . As the catheter is advanced over the first guidewire  122  or as the catheter is positioned at a desired location, the loaded second guidewire  124  can be advanced distally and into a branch lumen of the bifurcation. Use of the catheter illustrated in  FIG. 6  can be further understood with reference to  FIGS. 4A through 4F , where similar catheter positioning is described. 
       FIGS. 7A and 7B  show scaffold delivery systems according to further embodiments of the present invention, illustrating exemplary balloon and lumen configurations.  FIG. 7A  shows a system including delivery catheter  130  and a scaffold  148  positioned as described elsewhere herein, with a proximal portion of the scaffold disposed over balloon  132 , and distal portion of the scaffold positioned distal to the balloon. The catheter  130  includes guidewire lumens  134  and  136 , with the inflatable or expandable balloon  132  encircling both lumens  134  and  136 . In alternate embodiments, a catheter can be configured such that one or more guidewire lumens is disposed outside an expandable balloon or, in other words, with the one or more guidewire lumens disposed between an outer surface of a balloon and a scaffold positioned on the catheter.  FIG. 7B  illustrates a scaffold delivery system including a delivery catheter  140  having a balloon  142  encircling a first lumen  144 , with a second lumen  146  not encircled or positioned outside the balloon  142 . A scaffold  148  is shown coupled with the catheter  140  in a manner as describe elsewhere herein. Guidewire lumen  144  is encircled by balloon  142 , whereas guidewire lumen  146  runs outside balloon  142  and is disposed between an outer surface of the balloon  142  and an inner surface of scaffold  148  as shown. Upon expansion/inflation of the balloon  142 , lumen  146  and a proximal portion of scaffold  148  are expanded outward. Additional embodiments making use of the concepts described herein may be envisioned and are further included here. For example, in yet another embodiment, a delivery catheter may include both a first and second lumen disposed outside a balloon, such that inflation of the balloon provides lateral movement and expansion of the lumens, as well as a scaffold, disposed outside the balloon in the manner described herein. 
       FIGS. 8A and 8B  shows a scaffold delivery system including delivery catheter  150  and retractable sheath  152  covering a portion of the catheter, and at least partially covering a scaffold  154  disposed on the catheter. The system is illustrated having a delivery catheter, e.g., similar to embodiment described above with reference to  FIG. 5 , though various catheter designs may be used. The catheter  150  includes a distally positioned expandable balloon  156  and a guidewire lumen  158 , having a distal opening and a proximal opening. A non-bifurcated or cylindrical scaffold  154  is shown having a proximal portion positioned over the balloon  156  and a distal portion that extends beyond the balloon and distally. The catheter can be advanced over a positioned guidewire  160 , as described herein. The delivery catheter is shown positioned over a bifurcated guidewire system (although various guidewire configurations may be utilized). The guidewire system includes a first or outer guidewire  160  including a lumen through which a second guidewire  162  (or inner guidewire) can be positioned. The first guidewire  160  includes a distal opening  163  through which the second guidewire  162  can be advanced so as to form a distal guidewire bifurcation. The system further includes an outer sheath  152  positioned over the catheter so as to at least partially cover the scaffold  154 . The sheath  152  is coupled to an elongated member  164  that allows control of movement and/or positioning of the sheath during use. 
     In use, the guidewire system as illustrated in  FIGS. 8A and 8B  can be positioned, e.g., by advancing the first guidewire through a lumen of the patient and so a distal portion of the first guidewire enters into a branch lumen of a bifurcation. The distal opening of the first guidewire will be positioned proximally, e.g., upstream, of the bifurcation and the second guidewire can be advanced through the lumen of the first guidewire, with a distal portion of the second guidewire advanced out the opening in the wall of the first guidewire and into a second branch lumen of a bifurcation. The catheter delivery system can be advanced over the first guidewire, either prior to or following positioning of the second guidewire as described, or with the second guidewire loaded into the first guidewire lumen. The catheter is positioned proximally or upstream of the bifurcation with the distal portion of the scaffold disposed within the sheath. Once in the desired position, the sheath can be moved or withdrawn proximally so as to expose a distal portion of the scaffold. With a distal portion of the scaffold at least partially exposed outside the sheath, the catheter system can be advanced distally so that the distal portion of the scaffold spreads or flares over the guidewire bifurcation, as shown in  FIG. 8B , for positioning the scaffold in the patient&#39;s body lumen bifurcation. Once the sheath is withdrawn from covering the balloon, scaffold positioning can be accomplished in a staged manner similar to described further herein. The balloon  156  of the catheter is inflated so as to deploy the proximal portion of the scaffold upstream or proximal to the bifurcation. The catheter can then be withdrawn and a deployment system advanced for fully expanding the distal portion of the scaffold, e.g., as described above. 
     Another embodiment of a scaffold delivery system is described with reference to  FIGS. 9A and 9B . The system includes a delivery catheter  170  having an expandable balloon  170  disposed on a distal portion of the catheter, the catheter configured to provide movement of the balloon longitudinally or along the long axis of the catheter. The balloon is coupled to the catheter outer wall at least at points  174 ,  176 , with balloon ends inverted and extending along the catheter length. The balloon is unattached proximal to point  174  as well as distal to point  176  such that a force applied to the balloon allows the balloon to roll along the length of the catheter. For example, a force applied to the proximal portion or end of the balloon can allow the balloon to sort of roll along the catheter length in a distal direction. In one embodiment, as illustrated in  FIGS. 9A and 9B , the system includes an elongated member  178  having a distal portion slideably coupled to the shaft of the catheter proximal to the balloon. The elongated member  178  further includes a proximal portion extending proximally and configured to allow application of a force to the distal portion of the member for actuating or sliding the distal portion along the catheter length. A scaffold  180  can be positioned at least partially over the balloon for advancement and positioning in a lumen of a patient. As shown in  FIG. 9A , a scaffold can initially be positioned entirely over the balloon, or alternatively can be positioned with less than the entire length of the scaffold disposed over the balloon. Actuation of the member  178  distally along the length of the catheter so as to apply a force about the proximal end of the balloon  172 , in turn, allows the balloon  172  and scaffold  180  to roll forward and distally along the catheter length. As the balloon moves distally, the distal portion of scaffold is displaced off the distal portion of the balloon as the balloon inverts or folds inward at the distal end as being secured at anchor or attachment points  174 ,  176 . The positioning of the scaffold and movement of the balloon as described allows placement of the scaffold with respect to the balloon such that the proximal portion of the scaffold is disposed on the balloon, while a distal portion of the scaffold extends distal to the balloon. 
     In use, a scaffold  180  can be positioned on the balloon  172 , e.g., as illustrated in  FIG. 9A , and the catheter  170  advanced through a body lumen over a guidewire positioned in the body lumen. Guidewire configurations and positioning can be accomplished as described herein, including use of a single guidewire, a bifurcated guidewire, or a plurality of guidewires. A guidewire(s) is advanced through the body lumen and into position at a bifurcation. The catheter is advanced over the guidewire(s) running through the catheter lumen having openings  182 ,  184 . The catheter is advanced to the bifurcation, and member  178  is actuated to apply a force to the balloon, resulting in the balloon rolling forward or distally, and the scaffold rolling distally to extend further from the distal end of the balloon relative to the starting position of the balloon prior to member actuation, as described above. The actuation of the member and movement of the balloon as described, alone or in combination with movement of the catheter (e.g., withdrawing the catheter shaft proximally), allows the distal portion of the scaffold to be advanced into the bifurcation. The balloon can then be expanded or inflated for expansion and positioning of the proximal portion of the scaffold, or the portion of the scaffold positioned over the balloon following member actuation and balloon movement as described. The catheter can then be withdrawn and a second expansion system (e.g., pair of kissing balloons) advanced to the bifurcation and expanded for expansion and positioning of the distal portion of the scaffold.  FIG. 9  depicts a scaffold delivery system with a single guidewire lumen. The same rolling scaffold delivery system, except with two guidewire lumens (not depicted), could be used with two guidewires. The scaffold delivery system could either be advanced to the bifurcation over two guidewires or advanced near to the bifurcation over one guidewire with the second guidewire “loaded” on the catheter, as described previously. 
     As mentioned above, various guidewire configurations and assemblies can be utilized according to the methods and systems of the present invention. One exemplary guidewire apparatus or combination is described with reference to  FIGS. 10A and 10B , where a bifurcated guidewire assembly is illustrated. The assembly  190  includes an outer tube or first guidewire  190  having a proximal portion and distal portion, and further including a lumen extending through a length of the guidewire with the guidewire wall having holes or openings to the lumen including proximal opening  194 , distal opening  196 , and opening  198  disposed there between and on a side of the tube wall. Typically, opening  198  will be disposed on a distal portion of the first guidewire  192 . The assembly system further includes an inner wire or second guidewire  200  sized and configured for advancement through the lumen of the first guidewire  192 . In use, in one embodiment, the first  192  and second  200  guidewires can be advanced as one through a body lumen and into a desired position, such as into a first branch lumen of a bifurcation. The first guidewire  192  can then be positioned such that the opening  198  is at or near the bifurcation. The second guidewire  200  is then withdrawn proximally through the first guidewire lumen  192  such that the distal end of the second guidewire is proximal to the opening  198 , with positioning of the second guidewire then adjusted or rotated and advanced such that the second guidewire extends out opening  198  and can be advanced into a second branch lumen of a bifurcation. Alternatively, the first guidewire  192  can be first advanced into a desired position with the second guidewire  200  then advanced through the lumen of the first guidewire, or both guidewires can be positioned together, e.g., with the second guidewire “loaded” into the lumen of the first guidewire. 
     A guidewire apparatus or assembly according to another embodiment of the present invention is described with reference to  FIGS. 11A and 11B . The assembly  210  includes an outer tube or first guidewire  212  having a proximal portion and distal portion, and further including tube wall openings  214  and  216 , with a lumen extending there between through the body of the guidewire  212 . The tube  212  includes an elongated portion extending distal to the opening  216 . The assembly  210  further includes an inner wire or second guidewire  218  sized for advancement though the lumen of the outer tube  212 . 
     As noted above, a guidewire configuration suitable for use with systems and methods of the present invention can include a multi-guidewire assembly or apparatus.  FIGS. 12A and 12B  show an exemplary guidewire assembly  220 . A single guidewire  222  is shown in  FIG. 12A , the guidewire including a proximal portion and a distal portion having different cross-sectional geometries. The proximal portion can include a flattened or planar surface along a length of the wire, such as a “D-shaped” cross-sectional geometry. As shown in  FIG. 12B , such a configuration advantageously allows two guidewires  222 ,  224  to couple together, e.g., along the proximal portions, and may reduce wire tangling or guidewire wrap, reduce unwanted torque during use, and/or allow the distal portion to more easily or controllably assume the desired arrangement. The distal portion of wire  222  or  224  is shown having a generally cylindrical geometry or circular cross-sectional shape. 
     Another embodiment of the scaffold delivery system is depicted in  FIGS. 13A and 13B . In  FIG. 13A  the uninflated delivery system  230  has two guidewire lumens  231 ,  232  with an inflatable balloon  233  encircling one guidewire lumen  231 . The scaffold  234  is positioned such that the proximal end  235  and the distal end  236  are both disposed over the balloon.  FIG. 13B  depicts the inflated delivery system  230  with guidewire lumens  231  and  232 . Inflation of the balloon  233  expands the stent  244 . The proximal end of the stent  245  is fully expanded and the distal end  246  partly expanded. The inflated diameter of the proximal portion of the balloon  247  is greater than the inflated diameter of the distal portion of the inflated balloon  248 . 
       FIGS. 14A and 14B  depict another embodiment of the scaffold delivery system.  FIG. 14A  depicts an uninflated delivery system  250  with two guidewire lumens  251 ,  252  with an inflatable balloon  253  encircling guidewire lumen  251  and another inflatable balloon  254  encircling guidewire lumen  252 . The scaffold  255  is positioned such that the proximal end  256  is disposed over balloon  253  and the distal end  257  is disposed over balloon  254 .  FIG. 14B  depicts the inflated delivery system  250  with guidewire lumens  251  and  252 . Inflation of balloons  253  and  254  may be simultaneous or in seriatim. Inflation of balloon  253  expands the proximal portion of the scaffold  255 . Inflation of balloon  254  partially expands the distal portion of the scaffold  256 . The inflated diameter of balloon  253  is greater than the inflated diameter of balloon  254 . 
       FIGS. 15A and 15B  depict the distal portion of another embodiment of a scaffold delivery system with two guidewire lumens. In  FIG. 15A  the uninflated scaffold delivery system  270  with two guidewire lumens  271 ,  272  an inflatable balloon  273  and a scaffold  274  is advanced over a first guidewire  275  towards the bifurcation  276 . The distal portion of the guidewire  277  is positioned in a first branch vessel  278 . The first guidewire  275  traverses a first guidewire lumen  271 , exits from its distal end  279 , enters a sidehole on a second guidewire lumen  280 , traverses a distal portion  281  of the second guidewire lumen  272 , and then exits from its distal end  282 . The distal portion of a second guidewire  283  is positioned in the proximal portion of the second guidewire lumen  284 . The scaffold delivery system  270  and the second guidewire  283  are advanced as one unit towards the bifurcation  276 , over the first guidewire  275 . In  FIG. 15B , the first guidewire  275  is withdrawn from the first branch vessel  278  and from the distal portion of the second guidewire lumen  281  into the first guidewire lumen  271 . It is then advanced into the second branch vessel  289 . The second guidewire  283  positioned in the proximal portion of the second guidewire lumen  284  is then advanced through the distal portion of the second guidewire lumen  281  and into the first branch vessel  278 . 
     The systems and methods for delivery of a stent or scaffold at a blood vessel or body lumen bifurcation described herein may be used with standard tubular scaffolds or stents. They may also be used with tubular scaffolds or stents with modified features to enhance treatment or repair of the bifurcation. By way of example, aspects of the tubular scaffold or stent which may be modified include the number of circumferential elements, length of circumferential elements, number and configuration of connecting elements, and strut thickness. These modifications may be applied to all of the tubular scaffold or stent, or part of the tubular scaffold or stent, such as the distal portion. These modifications may improve treatment or repair of the bifurcation, for example by extending coverage further into the bifurcation, or increasing the radial force applied to the outer flanks of the bifurcation. 
     As noted above, a vessel or lumen bifurcation as discussed herein can include a generally symmetric as well as a bifurcation that is generally not symmetric. For illustration purposes, bifurcations are generally shown herein as substantially symmetric. It will be recognized that systems and methods of the present invention will not be limited to any particular anatomical arrangement of a bifurcation, and will include methods and systems configured or suitable for treatment of bifurcations of a wide range of morphological structure or arrangement. 
     It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are included within the spirit and purview of this application and scope of the appended claims. Numerous different combinations are possible and such combinations are considered part of the present invention.