Patent Publication Number: US-2011071559-A1

Title: Cutting Member for Bifurcation Catheter Assembly

Description:
RELATED APPLICATIONS 
     This application is a continuation of co-pending U.S. application Ser. No. 11/750,748, filed May 18, 2007, the entire disclosure of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to catheter systems and methods for treating vessel bifurcations. 
     BACKGROUND 
     Catheters are used with stents and balloon inflatable structures to treat strictures, stenoses, and narrowing in various parts of the body. Various catheter designs have been developed for the dilatation of stenoses and to deliver and deploy stents at treatment sites within the body. 
     Stents are typically intraluminally placed by a catheter within a vein, artery, or other tubular body organ for treating conditions such as, for example, occlusions, stenoses, aneurysms, dissection, or weakened, diseased, or abnormally dilated vessel or vessel wall, by expanding the vessel or by reinforcing the vessel wall. Once delivered, the stents can be expanded using one or more inflation members such as balloons. Stents can improve angioplasty results by preventing elastic recoil and by remodeling of the vessel wall and treating dissections in blood vessel walls caused by balloon angioplasty of coronary arteries. Stents can also be used as a drug delivery medium for treatment of damaged portions of a vessel. 
     While conventional stent technology is relatively well developed, stent technologies related to treatment of the region of a vessel bifurcation are still being developed. One challenge related to treatment of a vessel bifurcation involves the minimization of restenosis of the treated vessel. 
     SUMMARY 
     The present disclosure relates generally to catheter assemblies for treatment of bifurcated lumens in a patient, such as vessel bifurcations. 
     In one arrangement, a catheter assembly for deployment in a vessel includes a catheter shaft extending from a proximal end portion to a distal end portion. A balloon is operatively coupled to the distal end portion of the catheter shaft. At least one cutting member is coupled to the catheter assembly. As the balloon is inflated, the cutting member is moved to a position to cut a portion of the vessel. 
     There is no requirement that an arrangement or method include all features characterized herein to obtain some advantage according to this disclosure. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of an example catheter assembly for treatment of a vessel bifurcation shown in a non-deployed state. 
         FIG. 2  is a schematic perspective representation of a distal portion of the catheter assembly of  FIG. 1 . 
         FIG. 3  is a schematic cross-sectional view of the distal portion of the catheter assembly of  FIG. 1  shown in a deployed state. 
         FIG. 4  is a schematic side view of the catheter assembly shown in  FIG. 1  in a position prepared for treatment of a vessel bifurcation. 
         FIG. 5  is a schematic side view of the catheter assembly shown in  FIG. 4  with the side catheter branch extending into a branch vessel of the vessel bifurcation. 
         FIG. 6  is a schematic side view of the catheter assembly shown in  FIG. 5  with the side and main balloons inflated at the vessel bifurcation. 
         FIG. 7  is a schematic representation of a distal portion of another example catheter assembly for treatment of a vessel bifurcation shown in a deployed state. 
         FIG. 8  is a schematic representation of a distal portion of another example catheter assembly for treatment of a vessel bifurcation shown in a deployed state. 
         FIG. 9  is a schematic end view of the balloon of the distal portion of the catheter assembly of  FIG. 8  in a non-deployed state. 
         FIG. 10  is a schematic representation of a distal portion of another example catheter assembly for treatment of a vessel bifurcation shown in a deployed state. 
         FIG. 11  is a schematic view of an example cutting member. 
         FIG. 12  is another schematic view of the cutting member of  FIG. 11 . 
         FIG. 13  is another schematic view of the cutting member of  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION 
     I. Overview 
     This disclosure relates to bifurcation treatment systems, catheter assemblies, and related methods of treating bifurcations in a patient&#39;s body. The term “bifurcation” means a division location from one unit into two or more units. Generally, two types of bifurcations of a body organ include: 1) a main tubular member defining a main lumen and a branch tubular member defining a branch lumen that extends or branches off from the main tubular member, wherein the main and branch lumens are in fluid communication with each other; and 2) a primary or main member defining a primary or main lumen (also referred to as a parent lumen) that splits into first and second branch members defining first and second branch lumens. The term “lumen” means the cavity or bore of a tubular structure such as a tubular organ (e.g., a blood vessel). 
     Example applications of the principles disclosed herein include cardiac, coronary, renal, peripheral vascular, gastrointestinal, pulmonary, urinary, and neurovascular systems. Bifurcated vessels in such systems can become partially or fully blocked over time, which is referred to as stenosis of the artery. There are various procedures to treat the stenosis of a vessel, including angioplasty and/or the placement of a stent at the point of stenosis to reopen the vessel. Restenosis of the bifurcated vessel can occur over time. It is desirable to minimize the effects of restenosis. 
     The catheter assemblies, systems and methods disclosed herein can be used for locating a branch vessel of the vessel bifurcation and for treatment of stenoses of such vessels. In some examples, the catheter assemblies include one or more cutting members that are used to cut the vessel tissue at or near the stenosis. As used herein, the term “cut” means to gash, incise, slash, slit, open, or otherwise penetrate. In one example, the cutting is done during delivery of a therapy, such as the placement of a stent relative to the vessel bifurcation for treatment of the vessel bifurcation. Other arrangements are possible. In the examples shown, the cutting of the vessel tissue can help to minimize restenosis of the vessel. 
     II. The Example Illustrated in FIGS. 1-6 
     An example catheter assembly  10  is shown schematically with reference to  FIGS. 1-6 . The catheter assembly  10  is configured for treatment of a vessel bifurcation, such as a vessel bifurcation  80  described below. 
     Referring now to  FIG. 1 , the catheter assembly  10  includes a main catheter branch  12  and a side catheter branch  14 . The main catheter branch  12  includes a catheter shaft  20  having a proximal end portion  28  with a proximal end  18  and a distal end portion  30 . The catheter shaft  20  defines a main inflation lumen extending therethrough. The main catheter branch  12  further includes a main guidewire housing  22 . The main guidewire housing  22  defines a main guidewire lumen. 
     The main catheter branch  12  further includes a main balloon  24  extending along the guidewire housing  22 . A proximal waist  38  of the main balloon  24  is operably mounted to the catheter shaft  20 , and a distal waist  36  of the main balloon  24  is operably mounted to the main guidewire housing  22 . 
     The main catheter branch  12  further includes a side balloon  26 . See  FIG. 3 . The side balloon  26  includes an inflatable portion  45 , a distal waist  44 , and proximal waist  46 . The side balloon  26  generally extends around the main balloon  24 . 
     The waist members  44 ,  46  define a side inflation lumen through which inflation fluid is provided to the side balloon  26 . When uninflated, the inflatable portion  45  of the side balloon  26  maintains a generally collapsed profile. When inflated as shown in  FIG. 3 , the inflatable portion  45  of the side balloon  26  extends radially outward relative to the longitudinal axis of the main balloon  24 . 
     Typically, the distal waist  44  is operably mounted to the main guidewire member  22  distal of the main balloon  24 , and the distal waist  44  is also operably mounted in fluid communication with the side balloon  26 . The proximal waist  46  is operably mounted in fluid communication to the inflation portion  45 . The proximal waist  44  is also operably mounted to the distal end portion of the catheter shaft  20  in fluid communication with the main inflation lumen therein. The main balloon  24  is also coupled in fluid communication with the inflation lumen. 
     As shown in  FIGS. 1 and 3 , the side catheter branch  14  extends generally along the catheter shaft  20 . In examples, the side catheter branch  14  is generally parallel to the catheter shaft  20 , although other configurations are possible. The side catheter branch  14  has a side guidewire lumen extending therethrough. The side catheter branch  14  is used to align features of the catheter assembly  10  with the ostium into the branch vessel, as described below. 
     In the example shown in  FIGS. 1 and 3 , the side catheter branch  14  is coupled to the main catheter branch  12  by a ring assembly  53 . The ring assembly  53  including a first portion  55  coupled to the main catheter branch  12  so that the ring assembly  53  is fixed axially with respect to the main catheter branch  12 . In the example shown, the ring assembly  53  is positioned proximally on the main catheter branch  12  approximately one inch from the proximal waist  38  of the main balloon  24 . Other positions are possible. A second portion  57  of the ring assembly  53  is coupled to the first component  55  such that the second portion  57  can rotate about the first component  55 . The side catheter branch  14  is coupled to the second portion  57  so that the side catheter branch  14  can rotate about the main catheter branch  12 , while being fixed axially by the ring assembly  53 . 
     Referring to  FIGS. 1-3 , positioned about the main and side balloons  24 ,  26  is a sheath  52 . In example arrangements, the sheath  52  is crimped or otherwise attached to the balloons  24 ,  26  and/or the side catheter branch  14 . For example, in one arrangement, the sheath  52  is coupled to the side catheter branch  14  so that the sheath  52  can rotate about the main catheter branch  12  to a desired orientation. 
     Attached to an outer circumference  54  of the sheath  52  are one or more articulated cutting members, such as cutting members  62 ,  64 . Each cutting member  62 ,  64  includes a first cutting portion  66  and a second cutting portion  68 . In the example shown, the first cutting portions  66  of each of the cutting members  62 ,  64  are coupled to the outer circumference  54  of the sheath  52 . 
     The second cutting portions  68  are rotatably coupled to the first cutting portions  66  so that the second cutting portions  68  can pivot with respect to the first cutting portions  66 . In example arrangements, the second cutting portions  68  can pivot generally outwardly away from the outer circumference  54  of the sheath  52 . For example, the second cutting portions  68  can rotate generally radially outwardly from the outer circumference  54 . In some arrangements, the second cutting portions  68  rotate in a direction generally perpendicular to a longitudinal axis of the main catheter branch  12 . In one arrangement, the second cutting portions  68  are positioned to extend adjacent to and overlap an aperture  92  formed in the sheath  54  (see  FIG. 2 ), such that the side balloon  26  can extend through the aperture  92  to contact and pivot the second cutting portions  68 . 
     For example, referring now to  FIG. 3 , the catheter assembly  10  is shown with the main and side balloons  24 ,  26  in expanded form in the deployed state. As the side balloon  26  is expanded, the inflatable portion  45  extends through the aperture  92  in the sheath  52  (see  FIG. 2 ) to engage a lower surface  98  of the second cutting portions  68  of the cutting members  62 ,  64 . As the inflatable portion  45  expands, the inflatable portion  45  forces the second cutting portions  68  to pivot in opposite directions  94 ,  96  with respect to the first cutting portions  66 . In this manner, the first and second cutting portions  66 ,  68  can be forced against and cut the stenosis in the main and branch portions of the vessel, as described further below. 
     An outer surface  70  of each cutting member  62 ,  64  is configured to cut tissue, such as a stenosis in the bifurcated vessel. For example, in one embodiment, the outer surface  70  includes a sharpened edge that can be used to mechanically cut the stenosis. In other arrangements, the outer surface  70  can be used to deliver other therapies that are capable of cutting the stenosis, such as Radio Frequency (RF), ultrasonic, or other electromechanical ablation therapies. 
     The cutting members  62 ,  64  can be delivered to the stenosis in the bifurcated vessel using a variety of methods. For example, as described below with reference to  FIGS. 4-6 , the outer surface  70  of the cutting members  62 ,  64  can be coated with a material, such as polymeric material, that covers the cutting members  62 ,  64  so that the cutting members  62 ,  64  do not cut the blood vessel during delivery of the cutting member  62 ,  64  to the stenosis. Once at the desired site, the polymeric material can be removed so that the outer surface  70  can be used to cut the stenosis. For example, in one arrangement, the coating is removed by applying an electrical charge to the cutting members  62 ,  64  to erode the polymeric material. In other embodiments, the cutting members  62 ,  64  are configured such that, as the cutting members  62 ,  64  are employed as described below, the outer surface  70  cuts through the coating to cut the blood vessel. 
     In yet other arrangements, the cutting members  62 ,  64  can be folded against the outer circumference  54  of the sheath  52  during delivery. When the cutting members  62 ,  64  reach the stenosis, the cutting members  62 ,  64  can be mechanically moved into the cutting position. In one example, the cutting members  62 ,  64  are moved into the cutting position using hydraulic pressure from the fluid in the inflation lumens for the main and side balloons  24 ,  26 . In another embodiment, electricity is used to excite a ferrofluidic fluid within the balloons  24 ,  26  and/or a lumen connected to the cutting members  62 ,  64  to cause the cutting members  62 ,  64  to move from a stowed position to the cutting position, or the cutting members  62 ,  64  can themselves include Electroactive Polymers (EAP). In another arrangement, the cutting members  62 ,  64  can be made of a shape member material such as nitinol. In yet another example, an outer sheath can be placed over the cutting members  62 ,  64  during delivery. The outer sheath can be removed once the cutting members  62 ,  64  are at the stenosis to allow the cutting members  62 ,  64  to cut the stenosis. 
     In yet another example, the cutting members  62 ,  64  can be coupled directly to the main or side balloons. See  FIGS. 7 and 8 . In such arrangements, the cutting members can be encompassed within the folds of the main or side balloons during delivery. See  FIG. 9 . Upon expansion of the main or side balloons, the cutting members  62 ,  64  are exposed to allow the cutting members  62 ,  64  to cut the walls of the vessels. Other examples are possible. 
     In yet other examples, a plurality of cutting members can be mounted about the circumference of the sheath  52 . Upon delivery the sheath  52  extends at least partially into the bifurcated vessel, so that the cutting members located on the sheath can cut the bifurcated vessel. The cutting members on the sheath can also contact portions of the main vessel to cut any stenosis located in the main vessel as well. Other configurations are possible. 
     Referring now to  FIGS. 4-6 , the catheter assembly  10  can be used for treatment of the vessel bifurcation  80 . Typically, a main vessel guidewire  62  is inserted into a main vessel  82  of the vessel bifurcation  80  to a point distal of the vessel bifurcation. A branch vessel guidewire  60  is advanced to the vessel bifurcation and inserted through an ostium or opening  86  of a branch vessel  84 . A proximal end of the main vessel guidewire  62  is then inserted into the main guidewire lumen, and a proximal end of the branch vessel guidewire  60  is inserted into a branch guidewire lumen defined by the side catheter branch  14 . See  FIG. 4 . 
     The catheter assembly  10  is advanced over the guidewires  60 ,  62  to the vessel bifurcation  80 . See  FIG. 5 . The catheter assembly  10  is then advanced further distally until a distal end portion  56  of the side catheter branch  14  is positioned within the branch vessel  60 . A marker system (described further below) can be used to help confirm proper radial and axial alignment of the lateral branch opening  54  of the sheath  52  relative to the ostium  86  into the branch vessel  84 . 
     As the side catheter branch  14  follows the branch vessel guidewire  60 , the side catheter branch  14  rotates about the main catheter branch  12  at the ring assembly  53 . As the side catheter branch  14  rotates about the main catheter branch  12 , the sheath  52 , which is coupled to the side catheter branch  14 , also rotates about the main catheter branch  12  so that the aperture  92  formed in the sheath  54  (see  FIG. 2 ), is aligned with the ostium  86  of the branch vessel  84 . 
     After proper positioning of the catheter assembly  10  is confirmed, the main and branch balloons  24 ,  26  are inflated. As the side balloon  26  is inflated, the inflatable portion  45  positioned at the aperture  92  extends through the aperture of the sheath  54 . The remaining portions of the side balloon  26  contact and are held within the sheath  52  so that only the inflatable portion  45  extends through the aperture  92 . The inflatable portion  45  contacts and moves the second cutting portions  68  of the cutting members  62 ,  64 . As the inflatable portion  45  is further inflated, the second cutting portions  68  pivot in the directions  94 ,  96  with respect to the first cutting portions  66  so that the second cutting portions  68  engage the ostium  86  and/or the wall of the branch vessel  84 . In this position, the first and second cutting portions  66 ,  68  of the cutting members  62 ,  64  can be used to cut any stenosis on the walls of the main or branch vessels  82 ,  84 . 
     In one example, the sheath  52  can be moved axially within the main vessel  82  when the cutting members  62 ,  64  are in place to cause the cutting members  62 ,  64  to cut the stenosis in the vessels  82 ,  84  as desired. For example, in one arrangement, the second portion  57  of the ring assembly  53  can be released from the first component  55  once the catheter assembly  10  is in place so that the side catheter branch  14  can be moved axially with respect to the main catheter branch  12  to move the sheath  52  axially within the main vessel  82 . In other arrangements, other therapies such as RF or electrical can be delivered to initiate cutting. 
     In some examples, additional therapy can be delivered after the cutting members  62 ,  64  are used to cut the stenosis. For example, in one arrangement, one or more drugs are delivered to further minimize restenosis after the walls of the vessels  82 ,  84  have been cut. 
     In another example, a bifurcated stent is delivered to the bifurcation  80  after the walls of the vessels  82 ,  84  are cut. For example, a stent (not shown) can be positioned about the sheath  54 . After the cutting members  62 ,  64  are used to cut the stenosis, the sheath  54  can be removed from the catheter assembly  10 , and the stent can then be delivered to the bifurcated vessel by further expansion of the main and side balloons  24 ,  26 . 
     Other configurations are possible. For instance, in another example, the cutting members can be coupled directly to the stent. The cutting members can be made of a bioabsorbable material, such as iron or magnesium, so that, after delivery and cutting, the cutting members dissolve or otherwise dissipate over time. 
     It can be advantageous to use the cutting members  62 ,  64  to cut and create stress points on the walls of the main and/or side vessels  82 ,  84  adjacent to the ostium  86  because cutting of the area of the stenosis can minimize future restenosis of the area. For example, typically, the healthy portions of the blood vessel are more elastic than the heavily calcified regions of the stenosis. During deployment of therapy using balloons, the health portions of the blood vessel are therefore stretched more easily, which can cause stress-induced inflammatory effects leading to new stenoses. The use of the cutting members to cut the calcification associated with the stenoses allows the stenosis to be more easily expanded as well, thereby causing less stretching of the healthy blood vessel walls and the associated stress-induced inflammatory effects. 
     III. The Example Illustrated in FIG. 7 
     Referring now to  FIG. 7 , another example distal end portion  110  of a catheter assembly is shown. The distal end portion  110  is similar to that of the catheter assembly  10  described above, except that cutting members  162 ,  164  are coupled to the side balloon  26 , rather than a sheath. The first cutting portion  66  of each cutting member  162 ,  164  is coupled to the balloon  26 , and the second cutting portion  68  of each cutting member  162 ,  164  is coupled to the first cutting portion  66  so that the second cutting portion  68  can pivot with respect to the first cutting portion  66 . 
     As the side balloon  26  is inflated as shown in  FIG. 7 , the inflatable portion  45  of the side balloon  26  contacts and moves the second cutting portion  68  of each of the cutting members  162 ,  164  so that the second cutting portions  68  pivot in directions  194 ,  196 . In this manner, the first cutting portions  66  can be used to cut the wall of the main vessel, and the second cutting portions  68  can be used to cut the wall of the branch vessel of the bifurcation. 
     IV. The Example Illustrated in FIGS. 8 and 9 
     Referring now to  FIG. 8 , another example distal end portion  210  of a catheter assembly is shown. The distal end portion  210  includes a balloon  224  with a bulge  226  when inflated as shown in  FIG. 8 . Cutting members  262 ,  264  are coupled to the balloon  224 . The first cutting portion  66  of each cutting member  262 ,  264  is coupled to the balloon  224 , and the second cutting portion  68  of each cutting member  262 ,  264  is coupled to the first cutting portion  66  so that the second cutting portion  68  can pivot with respect to the first cutting portion  66 . 
     As the balloon  224  is inflated as shown in  FIG. 8 , the bulge  226  contacts and moves the second cutting portion  68  of each of the cutting members  262 ,  264  so that the second cutting portions  68  pivots. In this manner, the first cutting portions  266  can be used to cut the wall of the main vessel, and the second cutting portions  268  can be used to cut the wall of the branch vessel at the bifurcation. 
     Referring now to  FIG. 9 , the balloon  224  is shown in a semi-folded state. A plurality of folds  228  are formed as the balloon  224  is folded to reduce the profile of the balloon  224  in the non-deployed state. An example of a balloon folded in such a manner is shown in U.S. Pat. No. 7,160,317 filed on Jan. 4, 2002, the entirety of which is hereby incorporated by reference. The cutting members  262  and  264  (not shown in this view) are positioned in the interior between two folds  228  of the balloon  224  so that the cutting members  262 ,  264  are shielded by the folds  228  of the balloon  224  until the balloon  224  is expanded. Upon expansion of the balloon  224 , the folds  228  dissipate and the cutting members  262 ,  264  are exposed and moved to the cutting position shown in  FIG. 8 . 
     V. Alternative Arrangements for the Cutting Members 
     Referring now to  FIG. 10 , another arrangement for a distal end portion  310  of a catheter assembly is shown. The distal end portion  310  includes a plurality of cutting members  362 ,  363 ,  364 ,  365  coupled to the balloon  224 . In the example shown, the cutting members  362 ,  364  are coupled to the balloon  224 , and the cutting members  363 ,  365  are coupled to the bulge  226 . The cutting members  362 ,  363 ,  364 ,  365  each form a “sharks tooth” or pyramid configuration with a pointed cutting surface  370 . In this manner, the cutting members  362 ,  364  can be used to cut the wall of the main vessel, and the cutting member  363 ,  365  can be used to cut the wall of the branch vessel of the bifurcation. In the example shown, the cutting members  363 ,  364 ,  365 ,  366  are configured to fold laterally against the surface of the balloon  224  until the balloon  224  is inflated. For example, elastic members (not shown) made of a compliant material such as silicon rubber can be used to hold the cutting members  363 ,  364 ,  365 ,  366  against the surface of the balloon  224  prior to deployment. 
     Referring now to  FIGS. 11-13 , another example cutting member  462  is shown, which is similar to the cutting members  62 ,  64  shown in  FIGS. 1-9 . The cutting member  462  includes first and second cutting portions  466 ,  468 . The second cutting portion  468  pivots about a point  472  in a direction  480  with respect to the first cutting portion  466 . In example embodiments, the cutting member  462  is configured to allow the second cutting portion  468  to pivot to a specified angle α with respect to the first cutting portion  466 . In some examples, the angle α is greater than 90 degrees. In other examples, the angle α is less than 90 degrees. In the examples in which the angle α is less than 90 degrees, the first and second cutting portions  466 ,  468  can create a “scissor-type” action that captures and cuts the vessel at the ostium between the first and second cutting portions  466 ,  468  to thereby enhance the cutting action of the cutting member  462 . In example arrangements, the appropriate angle α is determined by the caregiver during a prescan of the bifurcation. 
     Other arrangements for the cutting members are possible. For example, in one alternative, each cutting member is broken into more than two portions that can pivot with respect to one another. In yet another example, each cutting member is made of a single portion. In yet another arrangement, some of the cutting members can be located on a sheath, and other cutting members can be located on the main or side balloons. Other configurations are possible. 
     The cutting members can be deployed at various points along the sheath and/or balloon to cut various portions of the walls of the main or branch vessels. In one alternative example, a plurality of cutting members are formed along the main balloon, side balloon, sheath, and/or an outer circumference of the side branch lumen to cut the walls of the main and/or side branch vessels at a plurality of sites. The cutting members can extend at one or a plurality of directions and/or orientations with respect to the other cutting members and the walls of the main and/or side branch vessels. 
     In yet another alternative, a kissing balloon arrangement can be used, in which a main balloon is positioned in the main vessel, and a side balloon is positioned along the main balloon. A distal part of the side balloon is positioned through the ostium into a branch vessel. Cutting members can be positioned along the side balloon, such as on the distal part that extends into the branch vessel. Upon inflation of the side balloon, the cutting members cut the vessel wall of the branch vessel, as described above. Other configurations are possible. 
     VI. Other Alternative Materials and Arrangements 
     In some arrangements, the distal end portions  30 ,  110 ,  210 ,  310  of the catheter assemblies can include marker material that is visible under X-ray or in fluoroscopy procedures. In some examples, the mark material is positioned along the distal end portions of the main and side catheter branches. Features of the system  10  that include marker material can be more easily identified and distinguished under X-ray or in fluoroscopy procedures. Some example marker materials include gold, platinum and tungsten. In one embodiment, the marker material can be included in a band structure that is secured to at least one of the main and side catheter branches  12 ,  14 . In other embodiments, the marker material is part of the material composition of portions of the main and side catheter branches  12 ,  14 . Viewability of features of the catheter assembly  10  under X-ray or fluoroscopy can assist the physician operating the system  10  to more easily adjust a position of the system  10  relative to the vessel bifurcation  80 . Example markers and marker materials suitable for use with system  10  are described in U.S. Pat. No. 6,692,483 to Vardi, et al., and co-pending U.S. Provisional Patent Application Ser. No. 60/776,149, filed on Feb. 22, 2006, and titled MARKER ARRANGEMENT 
     FOR BIFURCATION CATHETER, which patent matters are incorporated herein by reference. 
     Alternative catheter assemblies to those described above are configured for use with stents having self-expanding features. Self-expanding stents and self-expanding features of a stent typically do not require the use of an inflatable member such as a balloon to expand the stent or stent feature. Typically, self-expanding stents, such as those stents described in U.S. Published Patent Application No. 2004/0176837, are held in a constricted state using a sheath that fits over the stent. In the constricted state, the stent is able to navigate through a body lumen to the treatment site. Once the stent and sheath are positioned at the treatment site, the sheath is retracted proximally to release the stent for expansion of the stent into a radially expanded state. 
     A wide variety of stents, catheters, and guidewire configurations can be used with the catheter assembly embodiments of the present disclosure. The inventive principles disclosed herein should not be limited to any particular design or configuration. Some example stents that can be used with the catheter assemblies disclosed herein can be found in, for example, U.S. Pat. Nos. 6,210,429, 6,325,826 and 6,706,062 to Vardi et al., U.S. Pat. No. 7,220,275 to Davidson et al., and U.S. Published Patent Application No. 2004/0176837 titled SELF-EXPANDING STENT AND CATHETER ASSEMBLY AND METHOD FOR TREATING BIFURCATIONS, the entire contents of which are incorporated herein by reference. In general, the aforementioned stents include a lateral branch opening located between distal and proximal open ends of the stent. The lateral branch opening defines a path between an inner lumen of the stent and an area outside of the stent. The stent lateral branch opening is distinct from the cell openings defined between strut structures from which the stent sidewall is constructed. In some stents, the lateral branch opening can be surrounded by expandable structure. The expandable structure can be configured to extend radially into the branch lumen of the bifurcation upon expansion of, for example, an inflatable portion of the bifurcation treatment system. Typically, the stent is expanded after being positioned in the main lumen with the lateral branch opening aligned with an opening into the branch lumen. Alignment of the lateral branch opening with the opening into the branch lumen includes both radial and axial alignment. The stent, including the expandable structure surrounding the lateral branch opening, can be expanded with a single expansion or multiple expansions using one or more inflatable members. 
     The main and side balloons, and all other balloons disclosed herein, can be made of any suitable balloon material including compliant and non-compliant materials and combinations thereof. Some example materials for the balloons and catheters disclosed herein include thermoplastic polymers, polyethylene (high density, low density, intermediate density, linear low density), various co-polymers and blends of polyethylene, ionomers, polyesters, polycarbonates, polyamides, poly-vinyl chloride, acrylonitrile-butadiene-styrene copolymers, polyether-polyester copolymers, and polyetherpolyamide copolymers. One suitable material is SURLYN®, a copolymer polyolefin material (DuPont de Nemours, Wilmington, Del.). Still further suitable materials include thermoplastic polymers and thermoset polymeric materials, poly(ethylene terephthalate) (commonly referred to as PET), thermoplastic polyamide, polyphenylene sulfides, polypropylene. Some other example materials include polyurethanes and block copolymers, such as polyamide-polyether block copolymers or amide-tetramethylene glycol copolymers. Additional examples include the PEBAX® (a polyamide/polyether/polyester block copolymer) family of polymers, e.g., PEBAX® 70D, 72D, 2533, 5533, 6333, 7033, or 7233 (available from Elf AtoChem, Philadelphia, Pa.). Other examples include nylons, such as aliphatic nylons, for example, Vestamid L21011F, Nylon 11 (Elf Atochem), Nylon 6 (Allied Signal), Nylon 6/10 (BASF), Nylon 6/12 (Ashley Polymers), or Nylon 12. Additional examples of nylons include aromatic nylons, such as Grivory (EMS) and Nylon MXD-6. Other nylons and/or combinations of nylons can also be used. Still further examples include polybutylene terephthalate (PBT), such as CELANEX® (available from Ticona, Summit, N.J.), polyester/ether block copolymers such as ARNITEL® (available from DSM, Erionspilla, Ind.), e.g., ARNITEL® EM740, aromatic amides such as Trogamid (PA6-3-T, Degussa), and thermoplastic elastomers such as HYTREL® (Dupont de Nemours, Wilmington, Del.). In some embodiments, the PEBAX®, HYTREL®, and ARNITEL® materials have a Shore D hardness of about 45D to about 82D. The balloon materials can be used pure or as blends. For example, a blend may include a PBT and one or more PBT thermoplastic elastomers, such as RITEFLEX® (available from Ticona), ARNITEL®, or HYTREL®, or polyethylene terephthalate (PET) and a thermoplastic elastomer, such as a PBT thermoplastic elastomer. Additional examples of balloon material can be found in U.S. Pat. No. 6,146,356, which is incorporated herein by reference. 
     VII. Conclusion 
     As described herein, example arrangements include a catheter assembly for deployment in a bifurcated vessel. The catheter assembly includes a catheter shaft extending from a proximal end portion to a distal end portion, and a balloon operatively coupled to the distal end portion of the catheter shaft. The catheter assembly also includes a sheath positioned about the balloon, the sheath including at least one cutting member coupled thereto. As the balloon is inflated, the cutting member is moved to a position to cut a portion of a main vessel and/or the bifurcated vessel. In some examples, the cutting member includes first and second portions, the first portion being coupled to and pivoting with respect to the second portion to cut the bifurcated vessel. In this manner, restenosis of the bifurcated vessel is minimized. 
     It is noted that not all of the features characterized herein need to be incorporated within a given arrangement, for the arrangement to include improvements according to the present disclosure.