Patent Publication Number: US-2005131524-A1

Title: Method for treating a bifurcated vessel

Description:
FIELD OF THE INVENTION  
      This is a continuation-in-part application ofU.S. Ser. No. 10/373,489 filed Feb. 25, 2003 which is incorporated herein by reference. 
    
    
      The present invention relates, in general, to intralumenal medical devices, and, more particularly, to a new and useful stent having a non-uniform longitudinal pattern whereby the center section of the stent is more open in design than the proximal and distal sections of the stent as well as deformable struts for supporting and conforming to the ostium of a vessel side branch for enhancing vessel coverage and accommodating the side branches of vessels.  
     BACKGROUND ART  
      A stent is commonly used as a tubular structure left inside the lumen of a duct to relieve an obstruction. Commonly, stents are inserted into the lumen in a non-expanded form and are then expanded autonomously (or with the aid of a second device) in situ. When used in coronary artery procedures such as an angioplasty procedure for relieving stenosis, stents are placed percutaneously through the femoral artery. In this type of procedure, stents are delivered on a catheter and are either self-expanding or, in the majority of cases, expanded by a balloon. Self-expanding stents do not need a balloon to be deployed. Rather the stents are constructed using metals with spring-like or superelastic properties (i.e., Nitinol), which inherently exhibit constant radial support. Self-expanding stents are also often used in vessels close to the skin (i.e., carotid arteries) or vessels that can experience a lot of movement (i.e., popliteal artery). Due to a natural elastic recoil, self-expanding stents withstand pressure or shifting and maintain their shape.  
      As mentioned above, the typical method of expansion for balloon expanded stents occurs through the use of a catheter mounted angioplasty balloon, which is inflated within the stenosed vessel or body passageway, in order to shear and disrupt the obstructions associated with the wall components of the vessel and to obtain an enlarged lumen.  
      Balloon-expandable stents involve crimping the device onto an angioplasty balloon. The stent takes shape as the balloon is inflated and remains in place when the balloon and delivery system are deflated and removed.  
      In addition, balloon-expandable stents are available either pre-mounted or unmounted. A pre-mounted system has the stent already crimped on a balloon, while an unmounted system gives the physician the option as to what combination of devices (catheters and stents) to use. Accordingly, for these types of procedures, the stent is first introduced into the blood vessel on a balloon catheter. Then, the balloon is inflated causing the stent to expand and press against the vessel wall. After expanding the stent, the balloon is deflated and withdrawn from the vessel together with the catheter. Once the balloon is withdrawn, the stent stays in place permanently, holding the vessel open and improving the flow of blood.  
      Additionally, the presence of vessel side branches has had a major influence on the strategy of angioplasty for over a decade. It is common thought that over half of angioplasty procedures may place a vessel side branch in danger. The presence of side branches may also increase procedural complications. The occlusion rate of side branches during coronary angioplasty ranges from  3-15 %, depending on the clinical and anatomic features of the vessels. Stents may improve or worsen the flow through vessel side branches in both elective and bailout settings. The concept of “stent jail” is described as the incarceration of vessel side branches when their ostia are covered and made inaccessible by trunk vessel stenting.  
      To date, there have been no adequate stent designs or methods for stenting a bifurcated vessel that can avoid the problem of stent jailing in any appreciable or reportable way. The present invention is directed toward solving this stent jailing problem through a novel stent and novel method of use.  
     SUMMARY OF THE INVENTION  
      The present invention relates to a novel stent and novel method of use for treating a bifurcated lesion in a vessel. In one embodiment, a stent in accordance with the present invention comprises a lattice defining a substantially cylindrical configuration having a proximal end portion and a distal end portion, and a middle portion between the proximal end portion and the distal end portion. The lattice is movable from a crimped state to an expanded state. The lattice also has a plurality of adjacent hoops wherein each hoop has a plurality of adjacent loops. A plurality of bridges connect adjacent hoops. Additionally, a plurality of extensions are located on at least some portions of the lattice. Each of the hoops and extensions define a cell. And, the proximal end portion and the distal end portion of the lattice have at least one cell respectively and the middle portion of the lattice has at least one cell containing a plurality of deformable extensions. The at least one cell of the middle portion has spacing between adjacent hoops that is greater than the spacing between adjacent hoops of the proximal end portion and distal end portion respectively.  
      The plurality of extensions are cantilevered projections from the bridges of the lattice. And, the plurality of extensions are movably deformable in a direction away from the lattice and preferably external to the outer diameter of the stent. Preferably, at least some of the extensions are movably deformable in a direction away from the bridges. And preferably, at least some of the extensions are movably deformable in a direction away from the hoops.  
      Preferably, the stent in accordance with the present invention has one or more of the extensions that comprise a center arm terminating in a bifurcation. Additionally or optionally, the one or more of the extensions comprise one or more arms extending from the bifurcation.  
      More preferably, the one or more of the extensions comprise a first arm and a second arm extending from the bifurcation. In some embodiments according to the present invention, the first arm is at a length shorter than the length of the second arm, or vice versa, i.e. the first arm is at a length longer than the length of the second arm.  
      Moreover, the stent according to the present invention further comprises a drug on one or more portions of the lattice. In other embodiments according to the present invention, the stent further comprises a drug and polymer combination on one or more portions of the lattice. Particular examples of appropriate drugs include rapamycin, paclitaxel and a number of other drugs addressed later in this disclosure.  
      Furthermore, the stent according to the present invention is made of various materials. One material for the stent is a metal alloy such as stainless steel. Another material for the stent is a superelastic material which includes a superelastic alloy such as NiTi. Other materials include Cobalt based Alloys such as Cobalt-Chrome (L605).  
      Another appropriate material for the composition of the stent is a polymeric material. In some embodiments in accordance with the present invention, the stent is made of a biodegradable polymer.  
      The present invention also is directed to a novel method for treating a bifurcated lesion in a vessel. In one embodiment according to the present invention, a method for treating a bifurcated vessel wherein the bifurcated vessel has a main vessel and a side branch vessel extending from the main vessel comprises the steps of: 
          identifying a site in the main vessel;     placing a stent at the site in the main vessel, the stent comprising: 
            a lattice defining a substantially cylindrical configuration having a proximal end portion and a distal end portion, and a middle portion between the proximal end portion and the distal end portion, the lattice being movable from a crimped state to an expanded state, the lattice having a plurality of adjacent hoops, each hoop having a plurality of adjacent loops; a plurality of bridges connecting adjacent hoops; a plurality of extensions on the lattice; each of the hoops and bridges defining a cell; and the proximal end portion and the distal end portion of the lattice having at least one cell respectively and the middle portion of the lattice having at least one cell, the at least one cell of the middle portion having spacing between adjacent hoops that is greater than the spacing between adjacent hoops of the at least one cell of proximal end portion and distal end portion respectively, the lattice containing a plurality of deformable extensions;    
            dilating the at least one cell of the middle portion adjacent the side branch vessel; and     supporting a surface of the side branch vessel with at least one of the plurality of the extensions by deformably moving the at least one of the plurality of extensions away from the lattice and into contact with the surface of the side branch vessel.        

      In one embodiment according to the present invention, the method further comprises dilating the at least one cell of the middle portion adjacent the side branch vessel with a balloon. In another embodiment according to the present invention, the stent is made of a self-expandable material such as NiTi and the at least one cell of the middle portion is dilated due to shape memory aspects of the at least one cell (adjacent hoops and bridges) and the extensions associated therewith.  
      In other embodiments in accordance with the present invention, the method further comprises dilating the at least one cell of the middle portion adjacent an ostium of the side branch vessel. The dilating of the at least one cell of the middle portion adjacent an ostium of the side branch vessel can be conducted with a balloon.  
      The method according to the present invention further comprises placing a second stent in the side branch vessel. Accordingly, the second stent is placed in the side branch vessel at the ostium, and/or the second stent is placed in the side branch vessel adjacent the dilated at least one cell of the middle portion of the first stent, and/or the second stent is placed in the side branch vessel within the dilated at least one cell of the middle portion of the first stent.  
      Another embodiment in accordance with the present invention is directed to a method for treating a bifurcated vessel wherein the bifurcated vessel has a first vessel and a second vessel extending from the first vessel. The method comprises the steps of: 
          identifying a site in the first vessel;     placing a stent at the site in the first vessel, the stent comprising: 
            a lattice defining a substantially cylindrical configuration having a proximal end portion and a distal end portion, and a middle portion between the proximal end portion and the distal end portion, the lattice being movable from a crimped state to an expanded state, the lattice having a plurality of adjacent hoops; a plurality of bridges connecting adjacent hoops; a plurality of extensions on the lattice; each of the hoops and bridges defining a cell; and the proximal end portion and the distal end portion of the lattice having at least one cell respectively and the middle portion of the lattice having at least one cell, containing a plurality of deformable extensions;    
            dilating the at least one cell of the middle portion adjacent the second vessel; and     supporting a surface of the second vessel with at least one of the plurality of the extensions by deformably moving the at least one of the plurality of extensions away from the lattice and into contact with the surface of the second vessel.        

    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The novel features of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to organization and methods of operation, together with further objects and advantages thereof, may be best understood by reference to the following description, taken in conjunction with the accompanying drawings in which:  
       FIG. 1A  is a perspective view of a prior art stent of a closed cell design in a crimped state;  
       FIG. 1B  is a partial side view of a section of the prior art stent of  FIG. 1A  in a configuration conducive for a polishing manufacturing step;  
       FIG. 1C  is a partial side view of a section of the prior art stent of  FIG. 1A  in the crimped state;  
      FIG. ID is a partial side view of a section of the prior art stent of  FIG. 1A  in an expanded state;  
       FIG. 2A  is a partial side view of a prior art stent of an open-cell design in a configuration conducive for a polishing manufacturing step;  
       FIG. 2B  is a partial side view of the prior art stent of  FIG. 2A  in a crimped state;  
       FIG. 2C  is a partial side view of the prior art stent of  FIG. 2A  in an expanded state;  
       FIG. 3A  is a side view of a stent as a closed-cell design having an open area center section and one or more extensions in accordance with the present invention;  
       FIG. 3B  is an enlarged partial side view of the stent of  FIG. 3A  in accordance with the present invention;  
       FIG. 3C  is a perspective view of the stent of  FIG. 3A  in isolation after undergoing a cell dilation procedure in accordance with the present invention;  
       FIG. 3D  is a perspective view of the stent of  FIG. 3A  in a main vessel after undergoing a cell dilation procedure in accordance with the present invention;  
       FIG. 3E  is a perspective view of the stents of  FIG. 3A  in both a main vessel and a branch vessel in accordance with the present invention.  
       FIG. 4A  is a partial side view of a stent as an open-cell design having an open area center section and one or more extensions in accordance with the present invention;  
       FIG. 4B  is an enlarged partial side view of the stent of  FIG. 4A  in accordance with the present invention;  
       FIG. 4C  is a perspective view of the stent of  FIG. 4A  in isolation after undergoing a cell dilation procedure in accordance with the present invention;  
       FIG. 4D  is a perspective view of the stent of  FIG. 4A  in a main vessel after undergoing a cell dilation procedure in accordance with the present invention; and  FIG. 4E  is a perspective view of the stents of  FIG. 4A  in both a main vessel and a branch vessel in accordance with the present invention.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      As known in the art and best illustrated in  FIGS. 1A-1D  and  2 A- 2 C, a stent  100 , 100   a  respectively is an expandable prosthesis for a body passageway. It should be understood that the terms “stent” and “prosthesis” are interchangeably used to some extent in describing the present invention, insofar as the method, apparatus, and structures of the present invention may be utilized not only in connection with an expandable intraluminal vascular graft for expanding partially occluded segments of a blood vessel, duct or body passageways, such as within an organ, but may so be utilized for many other purposes as an expandable prosthesis for many other types of body passageways. For example, expandable prostheses may also be used for such purposes as: (1) supportive graft placement within blocked arteries opened by transluminal recanalization, but which are likely to collapse in the absence of internal support; (2) similar use following catheter passage through mediastinal and other veins occluded by inoperable cancers; (3) reinforcement of catheter created intrahepatic communications between portal and hepatic veins in patients suffering from portal hypertension; (4) supportive graft placement of narrowing of the esophagus, the intestine, the ureters, the uretha, etc.; (5) intraluminally bypassing a defect such as an aneurysm or blockage within a vessel or organ; and (6) supportive graft reinforcement of reopened and previously obstructed bile ducts. Accordingly, use of the term “prothesis” encompasses the foregoing usages within various types of body passageways, and the use of the term “intraluminal graft” encompasses use for expanding the lumen of a body passageway. Further in this regard, the term “body passageway” encompasses any lumen or duct within the human body, such as those previously described, as well as any vein, artery, or blood vessel within the human vascular system.  
      As used herein, the terms “biodegradable”, “degradable”, “degradation”, “degraded”, “bioerodible”, “erodible” or “erosion” are used interchangeably and are defined as the breaking down or the susceptibility of a material or component to break down or be broken into products, byproducts, components or subcomponents over time such as days, weeks, months or years.  
      As used herein, the terms “bioabsorbable”, “absorbable”, “resorbable” and “bioresorbable” are used interchangeably and are defined as the biologic elimination of the products of degradation by metabolism and/or excretion.  
      The stent  100  (FIGS. lA- 1 D) and  100   a  ( FIGS. 2A-2C ) comprises an expandable lattice structure made of any suitable material which is compatible with the human body and the bodily fluids (not shown) with which the stent  100  and  100   a  may come into contact. The lattice structure is an arrangement of interconnecting elements made of a material which has the requisite strength and elasticity characteristics to permit the tubular shaped stent  100  and  100   a  to be expanded or moveable from the crimped state shown in  FIGS. 1A and 1C  and  FIG. 2B  respectively to the deployed or expanded state as shown in  FIG. 1D  and  FIG. 2C  respectively and further to permit the stent  100  and  100   a  to retain its expanded state at an enlarged diameter. Suitable materials for the fabrication of the stent  100  and  100   a  include silver, tantalum, stainless steel, cobalt-based alloys such as cobalt-chrome (L605), gold, titanium or any suitable plastic material having the requisite characteristics previously described.  
      The stent  100  and  100   a  may also comprise a superelastic alloy such as nickel titanium (NiTi, e. g., Nitinol). For stents  100  and  100   a  made of superelastic material, the superelastic design of the stent  100  and  100   a  make it crush recoverable and thus suitable as a stent or frame for any number of vascular devices for different applications.  
      The stent  100  and  100   a  comprises a tubular configuration formed by a lattice of interconnecting elements defining a substantially cylindrical configuration and having front and back open ends  102 ,  104  and defining a longitudinal axis  103  extending therebetween ( FIG. 1A ). The stent  100  ( FIGS. 1A-1D ) is known and has a closed-cell  120  (closed cell design) and the stent  100   a  ( FIGS. 2A-2C ) is known and has an open-cell  120   a  (open cell design). Characteristics of open and closed cell designs will be addressed in greater detail later in this disclosure. In its closed crimped state, the stent  100  and  100   a  has a first, smaller outer diameter for insertion into a patient and navigation through the vessels and, in its expanded (deployed) state, a second, larger outer diameter for deployment into the target area of a vessel with the second diameter being greater in size than the first diameter. The stent  100  and  100   a  comprises a plurality of adjacent hoops  106  extending between the front and back ends  102 ,  104 . The hoops  106  include a plurality of longitudinally arranged struts  108  and a plurality of loops  110  connecting adjacent struts  108 . Adjacent struts  108  are connected at opposite ends so as to form any desired pattern such as a substantially S or Z shape pattern. The plurality of loops  110  have a substantially semi-circular configuration and are substantially symmetric about their centers.  
      The stent  100  and  100   a  further comprises a plurality of flexible links or bridges  114  and  114   a  respectively. The bridges  114  and  114   a  connect adjacent hoops  106 . The details of the bridges  114  and  114   a  are more fully described below.  
      The term “flexible link” or “bridges” have the same meaning and can be used interchangeably. There are many types or forms for the flexible links or bridges  114 . For example, the bridges  114  and  114   a  may be an S-Link (having an S-Shape or being sinusoidal shape), a J-Link (having a J-Shape), and N-Link (having an N-shape), M-Link (M-Shaped) or W-Link (W-Shaped), wherein each of these configurations can also be inverted.  
      In general, bridges  114  and  114 ( a ) respectively are used to connect adjacent hoops  106 . Each bridge comprises two ends wherein one end of the bridge is attached to a first hoop for example  106 , and the other end of the bridge is attached to a second, adjacent hoop, for example  106 , as shown in  FIG. 1A . The attachment points for the bridge can be at any location on the hoops  106 , for instance, connection points at or directly on loops  110  or struts  108 . Thus, bridges that connect at every loop  110  of adjacent hoops  106 , define a closed-cell as shown in  FIGS. 1A-1D . Moreover, bridges that connect adjacent hoops  106  at only a select number of loops  110 , e.g. a set number of loops  110  without interconnecting bridges, define an open-cell such as illustrated in  FIGS. 2A-2C .  
      The above-described geometry distributes strain throughout the stent  100  and  100   a , prevents metal to metal contact where the stent  100  and  100   a  is bent, and minimizes the opening between the features of the stent  100  and  100   a ; namely, struts  108 , loops  110  and bridges  114   114   a  respectively. The number of and nature of the design of the struts, loops and bridges are important design factors when determining the working properties and fatigue life properties of the stent  100  and  100   a . It was previously thought that in order to improve the rigidity of the stent, struts should be large, and thus there should be fewer struts  108  per hoop  106 . However, it is now known that stents  100  having smaller struts  108  and more struts  108  per hoop  106  improve the construction of the stent  100  and provide greater rigidity.  
       FIG. 1D  and  FIG. 2C  illustrate the stent  100  and  100   a  in its deployed or expanded state. As may be seen from a comparison between the stent configurations illustrated in  FIG. 1C  and  FIG. 2B  respectively and the stent configuration illustrated in  FIG. 1D  and  FIG. 2C  respectively, the geometry of the stent  100  and  100   a  changes quite significantly as it is deployed from its crimped state to its expanded or deployed state . As the stent undergoes diametric change, the strut angle and strain levels in the loops  110  and bridges  114  and  114   a  are affected. Preferably, all of the stent features will strain in a predictable manner so that the stent  100  is reliable and uniform in strength. In addition, it is preferable to minimize the maximum strain experienced by the struts  108 , loops  110  and bridges  114  and  114   a  since Nitinol properties are more generally limited by strain rather than by stress.  
      With respect to stent designs in general, there are regular connections which refer to bridges  114  and  114   a  that include connections to every inflection point around the circumference of a structural member, i.e. the loops  110  of adjacent hoops  106 .  
      Additionally, for stents having an open-cell design, e.g.  100   a , there are periodic connections for the stent bridges  114   a  that include connections to a subset of the inflection points (loops  110 ) around the circumference of the structural members (lattice). With respect to these period connections, the connected inflection points (loops  110 ) alternate with unconnected inflection points (loops  110 ) in some defined pattern.  
      Moreover, in general, bridges can join the adjacent structural members at different points. For example, in a “peak-peak” connection, the bridges  114  and  114   a  join the adjacent structural members or loops  110  by joining the outer radii formed by adjacent loops  110 . Alternatively, the bridges  114  and  114   a  can form “peak-valley” connections wherein the bridges  114  and  114   a  join the outer radii of one inflection point (of a structural member) to the inner radii of the inflection point of an adjacent structural member. Additionally “valley-valley” connections are also possible when the inner radii of inflection points of adjacent structural members are joined.  
      Furthermore, the bridges  114  and  114   a  between adjacent structural members, i.e. hoops  106 , define cell patterns as briefly mentioned above. For example, bridges  114  may define a “closed-cell” formed where all of the internal inflection points, e.g. loops  110  are connected by bridges  114  as shown in  FIGS. 1A-1D .  
      Furthermore, it is common for bridges  114  to form a “closed-cell” which is in essence a sequential ring construction wherein all internal inflection points of the structural members are connected by bridges  114 . The closed-cells permit for plastic deformation of the stent  100  during bending thereby allowing adjacent structural members to separate or nest together in order to more easily accommodate changes in shape of the stent  100 . The primary advantages of a closed-cell stent design is that it provides optimal scaffolding and a uniform surface regardless of the degree of bending of the stent. Depending on the specific features of a closed-cell design, the stent  100  may be less flexible than a stent with an open-cell design.  
      Turning now to the present invention, the same reference numerals will be used to designate like or similar features for a stent  100   b  ( FIGS. 3A-3E ), and  100   c  ( FIGS. 4A-4E ) in accordance with the present invention as best illustrated in these figures. One novel stent  100   b  in accordance with the present invention is a closed-cell design stent as best illustrated in  FIGS. 3A and 3B . By way of example, the stent  100   b  has a center section, center portion, center segment, middle section, middle portion or middle segment (all used interchangeably herewith)  105  that contains and utilizes bridges  114   b  that connect every loop  110  of adjacent hoops  106 . By way of example, the bridge  114   b  is shown as a sinusoidal-shaped bridge, however, the bridge  114   b  can comprise any particular shape or configuration such as the shapes addressed above.  
      Each bridge  114   b  has a finger or extension  118  integrally formed therewith and contiguous with the bridge  114   b . In accordance with the present invention, the extension  118  is a finger or finger-like projection from the bridge  114   b . Each bridge  114   b  can include more than one extension  118  extending therefrom. For instance, the sinusoidal-shape bridge  114   b  includes one or more apex  116  and a pocket  115 , which is a space directly beneath or underlying the apex  116  as shown. In this example, the extensions  118  are linear projections and extend from pocket  115  of an adjacent bridge  114   b . Extensions  118  and side extensions  119  (described in detail below) are located at any desired location for the stent  100   b  such as proximal end sections, segments or portions  102 , distal end sections, segments or portions  104  and center sections, segments or portions  105 . Preferably, extensions  118  and side extensions  119  are located in center section  105  of stent  100   b.    
      The extensions  118  extend from each pocket  115  of bridge  114   b  and are designed as cantilevered projections that are expandable or movably deformable in a direction away from bridge  114   b  by balloon force or by shape memory or the like during a side branch access procedure, for instance, treating lesions and supporting tissue in a vessel bifurcation, vessel trifurcation or a vessel having more than two side branches as well as treating lesions and supporting tissue in a bifurcation of a vessel bifurcation such as treatment and/or supporting of the iliac arteries or the like. The extension  118  has a center arm terminating in a bifurcation  140 . Each bifurcation  140  further includes at least one arm, for instance, a first arm  142  and a second arm  144 . The arms  142  and  144  can have different dimensions, for instance, the first arm  142  is shorter in length than the second arm  144  or vice versa, i.e. first arm  142  is greater or longer in length than second arm  144 . Alternatively, the extensions  118  project from the apex  116  of the bridge  114   b  (not shown).  
      Additionally, side extensions  119  are located on each pocket of adjacent loops  110  and project into the cells  120  located in center or middle section  105  of the stent  100   b . For efficiency purposes, such as ensuring compactness and low profile for crimping the stent  100   b  onto its delivery device or catheter, the bifurcation  140  is shaped to receive and accommodate the apex  116  of an adjacent bridge  114   b . Thus, adjacent bridges  114   b  will have adjacent extensions  118  that nest with each other when the stent  100   b  is in the crimped state. The side-by-side alignment of adjacent extensions  118 , of adjacent bridges  114   b  is facilitated by the shape of the bridges (in this example a sinusoidal shape embodiment) whereby at the underside of each apex  116  resides a bridge pocket  115  of sufficient size and configuration in order to receive and accommodate the extension (finger)  118 . At a minimum, the apex  116  of one bridge  114   b  will fit within the arms  142  and  144  of bifurcated  140  of extension  118  of an adjacent bridge  114   b  in the crimped state.  
      Additionally, the stent  100   b  has a center or middle portion or center or middle section  105  (designated by dashed lines) that has greater spacing (more open spaced area) between adjacent hoops  106  than the spacing (or size of open space areas) at or near the proximal end section or segment  102  and the distal end section or segment  104  respectively of the stent  100   b . Thus, the cells  120  of center section or portion  105  have a greater spacing between adjacent hoops  106 , than the spacing of the cells between adjacent hoops  106  at or near the proximal end section  102  and the distal end section  104  respectively.  
      A major advantage of the open-spaced center section  105  in one embodiment in accordance with the present invention, is that after the stent  100   b  is expanded in a vessel, such as a main or trunk vessel  200 , it may be desirable to conduct a cell dilation procedure, for example, a side branch access procedure such as shown in  FIGS. 3A-3E . Accordingly, the cell  120  itself is required to be dilated. Thus, when the cell  120  of the stent  100   b  is dilated through a cell dilation procedure, for example, a side branch access procedure, the cell  120  is dilated, in one embodiment, by placing a balloon within cell  120  in the center section  105  and inflating the balloon within the cell  120 . As the cell  120  is dilated, the extensions  118  and  119  are moved in a direction away from the bridge  114   b  and loop  110  respectively as shown in  FIG. 3C . Extensions  118  and  119  are designed to deform such that the extensions  118  and  119  come into supporting contact with the tissue of a vessel side branch  220  upon dilation of the cell  120  as shown in  FIG. 3D . This deformation causes an enlarged surface area for supporting the vessel side branch because the extension  1118 , due to its bifurcated  140  and side arms  142  and  144 , facilitates good contact and supporting surface for the vessel side branch. The extension  119  also provides additional contact and supporting surface area for the vessel side branch upon dilation of the cell  120 . These same advantages are afforded to the open-cell design stent  100   c  ( FIGS. 4A-4E ) in accordance with the present invention. Moreover, in another embodiment according to the present invention, the stent  100   b  and  100   c  ( FIGS. 3A-3E ) and (FIGS,  4 A- 4 E) respectively are self-expanding stents made of a shape memory material such as NiTi and the cell  120  ( FIGS. 3C-3E ) and the cell  120   a  ( FIGS. 4C-4E , addressed in greater detail below) are dilated by the shape memory aspect of the lattice features defining the cell, i.e. no separate balloon dilation step is required, but rather, the cell  120  and  120   a  respectively is dilated based on shape memory properties alone, to include deformation of the extensions  118  and  119  away from the lattice at the cell  120  and  120   a  respectively.  
      Additionally, the extensions  118  and  119  can be located on any of the loops  110 , and struts  108  as well as the bridges  114   b  or in any combination thereof.  
      In accordance with the present invention, the stent  100   b  ( FIGS. 3A-3E ), and stent  100   c  ( FIGS. 4A-4E ), have extensions  118  and  119  respectively located on one or more of the following components of the center section  105  of the stent lattice in one embodiment of the invention: the bridges  114   b , the hoops  106 , the loops  110 , and/or the struts  108 . Additionally, in another embodiment of the invention, extensions  118  and  119  are located on one or more of these stent features of the proximal end section  102 , the center section  105  and the distal end section  104  in any combination, i.e. extensions  118  and  119  located on the entire length of the stent or located on one or more of the sections  102 ,  104  and  105 . Moreover, the components of the stent lattice and the extensions  118  and  119  respectively have drug coatings or drug and polymer coating combinations that are used to deliver the drug, i.e. therapeutic and/or pharmaceutical agents including: 
      antiproliferative/antimitotic agents including natural products such as vinca alkaloids (i.e. vinblastine, vincristine, and vinorelbine), paclitaxel, epidipodophyllotoxins (i.e. etoposide, teniposide), antibiotics (dactinomycin (actinomycin D) daunorubicin, doxorubicin and idarubicin), anthracyclines, mitoxantrone, bleomycins, plicamycin (mithramycin) and mitomycin, enzymes (L-asparaginase which systemically metabolizes L-asparagine and deprives cells which do not have the capacity to synthesize their own asparagine); antiplatelet agents such as G(GP)II b III a  inhibitors and vitronectin receptor antagonists;     antiproliferative/antimitotic alkylating agents such as nitrogen mustards (mechlorethamine, cyclophosphamide and analogs, melphalan, chlorambucil), ethylenimines and methylmelamines (hexametbylmelamine and thiotepa), alkyl sulfonates-busulfan, nirtosoureas (carmustine (BCNU) and analogs, streptozocin), trazenes - dacarbazinine (DTIC); antiproliferative/antimitotic antimetabolites such as folic acid analogs (methotrexate), pyrimidine analogs (fluorouracil, floxuridine, and cytarabine), purine analogs and related inhibitors (mercaptopurine, thioguanine, pentostatin and 2-chlorodeoxyadenosine {cladribine}); platinum coordination complexes (cisplatin, carboplatin), procarbazine, hydroxyurea, mitotane, aminoglutethimide; hormones (i.e. estrogen); anticoagulants (heparin, synthetic heparin salts and other inhibitors of thrombin); fibrinolytic agents (such as tissue plasminogen activator, streptokinase and urokinase), aspirin, dipyridamole, ticlopidine, clopidogrel, abciximab; antimigratory; antisecretory (breveldin);     antiinflammatory: such as adrenocortical steroids (cortisol, cortisone, fludrocortisone, prednisone, prednisolone, 6α-methylprednisolone, triamcinolone, betamethasone, and dexamethasone), non-steroidal agents (salicylic acid derivatives i.e. aspirin; para-aminophenol derivatives i.e. acetominophen; indole and indene acetic acids (indomethacin, sulindac, and etodalac), heteroaryl acetic acids (tolmetin, diclofenac, and ketorolac), arylpropionic acids (ibuprofen and derivatives), anthranilic acids (mefenamic acid, and meclofenamic acid), enolic acids (piroxicam, tenoxicam, phenylbutazone, and oxyphenthatrazone), nabumetone, gold compounds (auranofin, aurothioglucose, gold sodium thiomalate); immunosuppressives: (cyclosporine, tacrolimus (FK-506), sirolimus (rapamycin), azathioprine, mycophenolate mofetil); angiogenic agents: vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF) platelet derived growth factor (PDGF), erythropoetin,; angiotensin receptor blocker; nitric oxide donors; anti-sense oligionucleotides and combinations thereof; cell cycle inhibitors, mTOR inhibitors, and growth factor signal transduction kinase inhibitors. It is important to note that one or more of the lattice components (e.g. hoops, loops, struts, bridges and extensions) are coated with one or more of the drug coatings or drug and polymer coating combinations.    

      Additionally, stent  100   b  and  100   c  in accordance with the present invention are made of any material such as metal alloys, nickel titanium alloys such as NiTi, including deformable metal alloys or plastics, metal alloys or plastics that exhibit crushing or recoil upon deployment of the stent or polymer materials such as biodegradable polymers and/or bioabsorbable polymers. Thus, the entire stent  100   b  and  100   c  itself (all components) or selectable components of the stent  100   b  and  100   c  in accordance with the present invention can be made of any of these type of materials to include plastics or polymers to include biodegradable polymers and/or bioabsorbable polymers. Additionally, the biodegradable polymers and/or bioabsorbable polymers used as material for stent  100   b  and  100   c  can be drug eluting polymers capable of eluting a therapeutic and/or pharmaceutical agents according to any desired release profile.  
      As illustrated in  FIGS. 3A-3E  and  4 A- 4 E, the extensions  118  and  119  are cantilevered projections and terminate in a free end (not connected to the stent lattice, e.g. connected at only one end to the stent lattice) that are movably deformable away from the stent lattice and longitudinal axis of stent  100   b  and  100   c  when the stent is deployed to its expanded or deployed state. In accordance with the present invention, the extension  118  and  119  can comprise a different material from the remainder of the components used for the stent lattice (for instance the hoops, loops, struts and bridges) especially if a different stiffness is desired.  
      As shown in  FIGS. 4A and 4B , the stent  100   c  in accordance with the present invention is an open-cell design stent also having a center section  105 . The center section  105  has a plurality of cells  120   a  having extensions  118  (connected to bridges  114   b ) and side extensions  119  connected at the inner most portion of the loops  110  (for example at the apex of loop  110 ). Accordingly, the cells  120   a  of the center section  105  of stent  100   c  have a larger open-spaced area (defined as the spacing between adjacent hoops  106 ) when compared to the open spaced areas associated with cells at or near proximal end section  102  and distal end section  104  respectively.  
      The same features and functionality as described above for the stent  100   b  also apply to the stent  100   c  in accordance with the present invention with the exception that the stent  100   c  is of an open-cell design.  
      As mentioned above, the extensions  118  and  119  enhance the overall surface area of the stent  100   b  and  100   c  respectively especially when the cell  120  is dilated as part of a cell dilation procedure for establishing vessel side branch access. The increased surface area within the space or area defined by the stent lattice including the extensions  118  and  119 , provides not only a significant advantage in preventing the prolapse of plaque or tissue into the cell  120   a  and ultimately into the lumen of the stent ( 100   b  and  100   c ) when deployed within a vessel  200 , i.e. at the site of a lesion within the vessel, but also provides support for the tissue of the vessel branch  220  thereby preventing “jailing” and maintaining good open patency of the vessel side branch  220 . Accordingly, the extensions or fingers  118  and  119  respectively in accordance with the present invention inhibit this prolapse phenomena thereby providing a prevention barrier against restenosis of the vessel  200  at the lesion site as well as permit good blood flow through the vessel side branch  220 . Additionally the extensions or fingers  118  and  119  are good for localized drug delivery to a very common site for restenosis in bifurcations, namely the vessel carina and/or ostium.  
      In accordance with the present invention, the extensions or fingers  118  and  119  respectively may also take the form of other shapes and patterns.  
      Additionally, the stent  100   b  and  100   c  in accordance with the present invention may be made from various materials such as those referred to above. For example, the stent  100   b  and  100   c  is made of an alloy such as stainless steel. Moreover, the stent  100   b  and  100   c  is alternatively made of a crush-recoverable material such as a superelastic material or superelastic alloy or combination of alloys. In particular, the stent  100   b  and  100   c  is made of nickel titanium (NiTi) or nickel titanium tertiary alloys thereby providing it with superelastic and crush recoverable properties as a self-expanding stent. Preferable materials include those which are plastically deformable like stainless steel and cobalt-chrome.  
      As mentioned previously, a major advantage of the extensions  118  and  119  respectively, is that the extensions provide enhanced and/or additional coverage and support at the ostium and carina of a vessel side branch  220  ( FIGS. 3D and 4D  respectively) with either a closed-cell or the open-cell stent  100   b  and  100   c  respectively when the stent  100   b  and  100   c  undergo a dilation of the cell  120   a  as part of a vessel side-branch access procedure such as the one briefly described above. Thus, upon dilation of a cell  120   a , for example in the center section  105  of stent  100   b  and  100   c  respectively, the extensions  118  and  119  respectively are cleared from flow passage at the vessel side branch  220  due to balloon expansion (in one embodiment of the invention or by shape memory deformation in another embodiment of the invention), and the cantilevered extensions  118  and  119  respectively are moved away from the lattice and cell  120   a  into a support position (by the balloon expansion or by shape memory deformation respectively) against the tissue of the vessel side branch  220  for directly supporting the side branch vessel  220  thereby forming a stable graft at the main vessel  220  and side branch vessel  220  junction as illustrated in  FIGS. 3D and 4D  respectively.  
      Method for Accommodating Vessel Side Branches  
      As best illustrated in  FIGS. 3D and 3E  and  FIGS. 4D and 4E  respectively, the novel method for accommodating vessel side branches and avoiding stent jailing problems in accordance with the present invention comprises identifying a vessel  200  to be treated with a stent, for instance by using stent  100   b  and  100   c  and placing the stent  100   b  and  100   c  at a site within the target vessel  200 . By way of example, the target vessel can be either a main vessel or trunk vessel  200  of any artery or one of the minor side branches  220  extended therefrom.  
      Additionally, a determination is made as to whether or not any connecting vessels adjacent the site in the targeted vessel also require stent placement. This determination can be made either with prior to placement of the stent  100   b  and  100   c  in the target vessel or after placement of the stent  100   b  and  100   c  at the site. Placement of a second stent  100   b  and  100   c  in one of the side branch vessels  220  or vessels  220  connecting the target vessel  200  after placement of a first stent  100   b  and  100   c  in the main or trunk vessel  200  or the initial or first vessel  200  is made for purposes such as treating disease such as stenosis, vulnerable plaque, ischemic heart disease or the like or for establishing or re-establishing patency of a side branch vessel  220  or second vessel  220  by removing obstructions at the ostia of the side branch vessel or second vessel which may be caused one of the elements or features of the lattice of stent  100   b  and  100   c , i.e. a “jailing” problem or by displaced tissue of any one of the vessels such as intima at the ostia of the side branch vessel  220  or second vessel  220 .  
      Preferably, when placing stent  100   b  and  100   c  in the main vessel  200  or trunk vessel  200  (the initial vessel or first vessel to be stented) the center section  105  of the stent  100   b  and  100   c  is aligned at, near or over the ostium of the side branch vessel  220  or second vessel  220  interconnecting the main vessel or first vessel  200 .  
      Accordingly, after placement of the first stent  100   b  and  100   c , within the main vessel or first vessel  200  and alignment of a cell  120  and  120   a  within center section  105  at, near or over the ostium of the side branch vessel or second vessel  220 , the cell  120  and  120   a  is identified and expanded, for example, by inserting a catheter having an expansion device such as a balloon and inflating the balloon such that the cell  120  and  120   a  is expanded or dilated to a larger size (when compared to the size of cell  120  and  120   a  after initial placement and prior to dilation of the cell  120  and  120   a , i.e. an initial smaller size), or in an alternative embodiment according to the present invention, the lattice portions defining the cell  120  and  120   a , i.e. the adjacent hoops  106  and bridges  114   b , are expanded as part ofthe self-expanding material of the stent  100   b  and  100   c  to include self-expansion of the extensions  118  and  119  upon deployment of stent  100   b  and  100   c  to its expanded state or expanded configuration.  
      Dilation of cell  120   a  at the ostium of the side branch vessel or second vessel  220  is accomplished by exerting force upon the one or more of the components of the lattice defining cell  120   a  for the stent  100   b  and  100   c  such as the hoops  106 , the loops  110 , the struts  108 , the bridges  114   b , the extensions  118  and  119 , the bifurcations  140 , and the arms  142  and  144 . Accordingly, an expansion device, such as a catheter having an inflatable balloon is inserted into the cell  120   a  such as being inserted at a location adjacent or near one or more of lattice components such as those described above. Inflation of the balloon exerts the requisite force on the one or more cell defining components of the lattice.  
      Moreover, upon dilation of cell  120   a , for example, through balloon dilation, the components of the lattice are moved away from the cell  120   a  as shown in  FIGS. 3C and 3D  and  FIGS. 4C and 4D  respectively. Particularly, the cantilevered extensions  118  and  119  are moved away from the bridge  114   b  and loop  110  respectively (moved away from longitudinal axis of stent  100   b  and  100   c ). The extensions  118  and  119  are designed such that portions of the surface area of the extension  118  (such as the center arm, the bifurcation  140  and arms  142  and  144 ) and extension  119  contact and support the vessel wall of the side branch vessel or second vessel  220 , particularly at the ostium thereby providing additional support for the side branch vessel or second vessel  220  and thereby preventing prolapse of this tissue at the vessel bifurcation and thereby preventing jailing of the side branch vessel or second vessel  220 .  
      As best illustrated in  FIGS. 3E and 4E  respectively, after dilating cell  120   a , a second stent  100   b  and  100   c  in accordance with the present invention, is placed, in the side branch vessel or second vessel  220 , i.e. at the ostium of the side branch vessel or second vessel  220 . The second stent  100   b  and  100   c  is placed either simultaneously with dilation of the cell  120   a  by deployment of the second stent  100   b  and  100   c  upon inflation of the balloon or after dilation of the cell  120   a  through use of a second delivery device, such a catheter, carrying the second stent  100   b  and  100   c .  
      While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.