Abstract:
An apparatus and method to place a bifurcated stent into a body lumen by using a delivery device requiring only one incision. Relative axial movements between a catheter and a sheath in the delivery device permit the insertion and expansion of the stent. During placement into and removal from the patient&#39;s body, the branch sections of the bifurcated stent are held in substantially parallel arrangement. Opposing tendencies between a self-expanding stent and leg portions within the delivery device can be tailored such that, during deployment, the bifurcation bias due to the elastic spring forces in the stent overcome the parallel bias within the delivery device. In situations where a balloon-expandable stent is used, the delivery device obviates the need for balloon change during stent placement. Such catheters can also be used for angioplasty, eventually in combination with stenting, and are also equally applicable to both multibranch and side branch body lumens, which are difficult to reach with conventional devices and techniques.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention generally relates to a device and method for delivering an expandable endoluminal prosthetic device, such as a stent, and more particularly to a device and method for placing a bifurcated stent such that only a single incision into a patient need be made.  
           [0002]    Expandable surgical devices, such as stents and angioplasty balloons, are used in a variety of places in the human body to support various anatomical lumens, such as blood vessels, respiratory ducts, gastrointestinal ducts and the like. Conventionally, these devices are deployed in regions of stenosis or constriction in the target body lumen to hold the lumen open, thus obtaining a patent lumen and preventing immediate or future occlusion or collapse of the lumen and the resultant obstruction of fluids flowing therethrough. Because stent and balloon implantation is a relatively non-invasive procedure, it has proven to be a favorable alternative to surgery in, for example, certain cases of vascular stenosis. Bifurcated devices, with their trunk and branching configuration, are particularly well-suited for use in branching body lumen systems, such as in the coronary vasculature (which include the right, left common, left anterior descending and circumflex arteries and their branches) and the peripheral vasculature (including branches of the carotid, aorta, femoral, popliteal, and related arteries). Placement of such a bifurcated device can be rather complicated, often involving approaching the bifurcated section of the artery through at least two side branches or through the trunk plus one side branch. This procedure can be not only time-consuming, but also lead to more incision sites in the patient&#39;s body, as well as necessitate more complicated maneuvers for the surgeon. Procedures for placement of a bifurcated stent are described in U.S. Pat. No. 5,720,735 to Dorros, entitled “Bifurcated Endovascular Catheter” and U.S. Pat. No. 4,994,071 to MacGregor, entitled “Bifurcating Stent Apparatus and Method”. In these patents, which are representative of the state of the art, each of the branches has a dedicated guide wire to guide the placement of balloons, stents, stent grafts or grafts into a bifurcated anatomical lumen. This redundancy can lead to increases in the overall size, cost and complexity of delivery devices.  
           [0003]    Accordingly, there exists a need for an apparatus used to place bifurcated stents and related surgical devices into a body lumen such that simpler surgical procedures are enabled, with a concomitant decrease in incision number or size and related invasive steps, thereby reducing patient trauma associated with complex medical procedures.  
         SUMMARY OF THE INVENTION  
         [0004]    This need is met by the present invention, where the placement of a stent becomes simplified by the use of a single delivery catheter, using only a single incision in only one location. The present apparatus and method allow for placing non-bifurcating stents in a side branch of a bifurcating lumen, as well as for placement of all kinds of bifurcating stents anywhere in the body, with or without a graft. While it can be readily appreciated that the device described herein is applicable for use in numerous endoluminal devices, and in a variety of bifurcated body lumens, much of the subsequent discussion is limited to the example of a bifurcated stent for use in preventing an abdominal aortic aneurysm (hereinafter referred to as triple A), where such a device is commonly known as a triple A graft stent. Such a stent includes a near side branch section, far side branch section, and a trunk section joined to adjacent, or hinged ends of the two branch sections. Furthermore, it will be appreciated that the expansion of the triple A graft stent and related stents can be effected by plastic deformation due to balloon pressure, or triggering of elastically stored energy in the stent (such as with bistable stents or elastic or superelastic expansion).  
           [0005]    According to an embodiment of the present invention, a catheter for inserting, deploying and removing a bifurcated surgical device is disclosed, where preferable surgical devices include bifurcated endoluminal stents, stent-grafts, grafts and balloon angioplasty mechanisms. The catheter, with an elongate hollow body, narrow proximal end and widened distal end is insertable into a single percutaneous incision site. The hollow body houses a central catheter wire that is used to deploy a stent mounted to the catheter. The distal end of the elongated body includes a flanged, exaggerated generally cylindrical portion configured to sheath the ends of the branch sections of the bifurcated stent, thus ensuring a small cross-sectional area for the entire as-inserted combination. The central catheter wire includes two leg portions connected at a common end to a trunk portion. The two leg portions of the central catheter wire are biased to a closed position, so that they are in a substantially side-by-side, parallel relationship, both effectively parallel with the trunk portion. This bias is important for establishing a small cross sectional area of the wire once the stent has been deployed. In stents that rely on balloons for expansion, this bias in the central catheter wire also helps to bring the deflated balloons together for improved ease of catheter removal. Prior to the deployment of the bifurcated surgical device, the bias is designed to be overcome by inherent spring forces in the branches of the bifurcated surgical device, which needs to expand to approximate the angle formed between the main and branching body lumens. This bias in the bifurcating surgical device is such that a substantially Y-shaped intersection is formed, which also induces the catheter to assume such a shape upon unsheathing of the bifurcating surgical device.  
           [0006]    The coaxial arrangement between the components of the present system and the stent, as well as the relative axial movement between them permit both simple operation coupled with unobtrusive cross-sectional dimensions. Operability is further enhanced by the inclusion of position-indicating markers with steerable features. In addition to providing indicia of stent axial (or translational) position relative to the catheter, these markers provide readily-apparent indicia of the angular position of the device vis-à-vis the body lumen to enable accurate positioning of the stent. To enhance patient safety, the catheters of each of this and the following embodiments may optionally include a flexible housing that can follow the angular movements between the branches easily, while it smoothens the functioning of the device.  
           [0007]    Alternately, the apparatus can be adapted to accept self-expanding stents, where the bifurcated balloon is replaced by multiple travelling sheaths that work in cooperation with tension and pushing elements within the catheter for removal of the sheaths from the stent surface. In this configuration, an additional wire, called a sheath deployment wire, is disposed adjacent the central catheter wire in the same hollow portion of the elongate body. The two wires work in conjunction with one another, as the sheath deployment wire is used to push the self-expanding stent and one or more of the stent-restraining travelling sheaths farther into the aorta such that the stent and sheaths are entirely beyond the body lumen bifurcation point. As previously discussed, the stent branches are of such spring bias that their tendency to splay is greater than the ability of the central catheter wire leg portions to stay together. This bifurcation allows one of the stent branches to be positioned in each of the iliac arteries upon partial pullback of the stent. Once the pullback has been accomplished, and the stent sheaths have been seated adjacent the body lumen bifurcation point, the central catheter wire, which now includes a series of mechanical stops along its trunk section, can be translated relative the stent such that it engages the travelling sheaths surrounding the far side branch and the trunk, moving them away from their corresponding stent sections, and permitting the stent to expand under its own elastic power. Once this is completed, the near side branch sheath can be removed by pulling back on the sheath deployment wire to allow expansion of the final stent section, at which time the catheter can be withdrawn therethrough, and out the incision.  
           [0008]    According to another embodiment of the present invention, a catheter used for the deployment of a self-expanding surgical device is similar in structural attributes to the aforementioned alternate embodiment catheter, with an additional biasing sleeve to facilitate removal of the sheath and wire once the surgical device has been inserted. This results in a sandwich-like structure that surrounds the surgical device, and includes the central core catheter wire inside the inner surface of the self-expanding surgical device, a travelling sheath surrounding the outer surface of the surgical device, and a biasing sleeve disposed on the outer surface of the travelling sheath. Once the crush-resistant surgical device is pushed out from the travelling sheath and deployed in the body lumen, the contracting force of the biasing sleeve causes the travelling sheath to collapse into a smaller diameter, coming to rest substantially on or adjacent the central catheter wire. This reduced cross-sectional area makes it easier to remove the sheath and wire through the hollow inner core of the now-expanded surgical device without snagging or otherwise inadvertently engaging the surgical device.  
           [0009]    According to another embodiment of the present invention, a catheter for delivering a non-branching stent can be placed into a side branch of a body lumen for situations where the catheter side branch makes an acute angle from the main lumen insertion direction, thereby overcoming the difficulty with which conventional catheters have had in reaching such a side branch. In this configuration, the main catheter, in contrast to the previous embodiment, does not have an elongate hollow body, instead comprising a core wire, sheath and sheath deploying wire. The core wire is further defined by a main body portion and a leg portion, where the main body portion extends from a user-graspable proximal end to a distal end, and the leg portion is hingedly attached to the main body portion&#39;s distal end and configured for transporting the stent. The inherent spring stiffness at the distal junction is such that the leg and main body portions are biased in an open position to form an acute angle roughly commensurate with the angle made between the main body and side branch lumens. The angled bias between the distal end of the core wire&#39;s main body portion and the joined leg portion can be overcome such that the remote end of the leg portion is pointing substantially toward the proximal end of the main body portion. In this compressed state, the cylindrical, substantially hollow sheath can be inserted over the distal junction, thus holding the main body and leg portions of the core wire in a substantially parallel configuration. The stent can be inserted over the remote end of the leg portion that protrudes beyond the open end of the sheath. As with the previous embodiments, the stent can be either self-expanding or balloon expandable. In the balloon-expandable variant, the core wire could be of hollow tubular structure to permit the passage of an expansion fluid or an additional wire therethrough. The use of a central catheter wire, surrounded by the thin-walled tube with high flexibility (made from, for example a superelastic Nitinol) is but one example. A catheter with such a tubular core wire has more longitudinal rigidity and gives a better support for accurate relative movements between the central catheter wire and the delivery sheath. Proximal actuation using such a configuration becomes much more controllable, thus facilitating the user&#39;s task.  
           [0010]    According to another embodiment of the present invention, a stent delivery catheter comprising an elongate body, central catheter wire and a stent release wire is disclosed. The elongate body includes a proximal end, a distal end sufficiently enlarged relative to the proximal end so as to sheath an engaging end portion of a stent, and a hollow core extending between the proximal and distal ends. The central catheter wire fits through the hollow core, and is positionable relative to the hollow core. The central catheter core wire is made up of a main body portion with a user-graspable proximal end and a distal end, and a leg portion comprising a distal end joined to the distal end of the main body section to form a hinged relationship therebetween and a remote end engageable with the stent. The stent release wire is disposed within and positionable relative to the hollow core in much the same way as the central catheter wire. The stent release wire is defined by a main body portion with a user-graspable proximal end and a distal end configured to engage the stent and the remote end of the leg portion. As with the previous embodiment, the central catheter wire may be of hollow tubular construction to permit the placement of another wire or fluid supply line therein.  
           [0011]    According to yet another embodiment of the present invention, a method for inserting a bifurcating surgical device, such as a stent, is disclosed. The method includes bringing the stent into place by advancing the whole stent in a delivery catheter with restraining sheath through a single incision location. By way of example, this single incision could be through a main side branch artery in a patient&#39;s leg. The distal end of the delivery catheter holding the stent is inserted until it arrives adjacent the aneurysm area, with the lower ends of the stent branch sections beyond the body lumen bifurcating point, where the aorta divides itself into the two common iliac arteries. Upon insertion beyond this bifurcating point, a restraining sheath is pulled back, thereby exposing the unconnected ends of the two branch sections. The stent is still in its unexpanded state, but the elasticity of the two branch sections of the stent tends to create an angle between the two hingedly connected branch sections. In the present context, two or more members are considered to be hingedly connected when they are joined at a common end, regardless of how they are attached, such that only relative rotational movement (with no translational component) is permitted at such connected end, while the opposing unconnected ends are free to move relative to one another, constrained only by resistive forces operating at the connected end. A resiliently biased connection could include hingedly connected members that exhibit elastically deformable properties such that upon removal of a constraining force, the members would revert back to a predetermined unconstrained spacing relative to one another. By proper engineering choice of the elastic force, the amount of spread between the unconnected ends of the branch sections is such that they can gently be pulled back into their respective arteries, while the trunk section of the stent is also pulled back into the final artery section, where the aneurysm is located.  
           [0012]    Once the stent is properly positioned relative to the iliac arteries and the lower aorta, the whole stent can be expanded into the final shape, by, for example, either self-expansion features integral to the stent, or by a conventional expander (typically a balloon) located within the delivery catheter. In the former case, the stent may be made of a shape-memory material. In the latter case, the balloon can either be made from one single piece, with the same overall shape as the bifurcated stent, or from several sections that can be inflated at different times. With such a bifurcated balloon, the whole stent can be expanded without repositioning of the balloon and, if needed, can be done very fast, thus reducing critical operation time. After deflating, the balloon can then be moved in the catheter insertion (distal) direction until the free end of the far side leg portion is moved completely beyond the body lumen bifurcation point and into the trunk section of the aorta. The two branch sections of the bifurcating balloon have been made elastic as well, but in a different way than the branch sections of the stent, such that they are biased to a substantially parallel orientation in line with the trunk of the balloon. One way this biasing can be achieved is by using two elastic spring wires, strips or tubes made from straight superelastic Nitinol, or related shape-memory material, disposed either in or outside the center of the balloon branch sections, coming together in or near the center of the balloon trunk. Thus, in addition to the two opposing bias forces previously discussed, where the branch sections of the stent have to move apart for placement and the leg portions of the central catheter wire have to move together for easier removal, the presence of the balloon bias further reinforces the closing tendency of the catheter so promote the small cross-sectional area necessary to ensure ease and safety of catheter removal. Thus, once the stent has been deployed, and the catheter with the deflated balloon has been pushed into the trunk section of the aorta, the balloon branch sections snap back to their parallel position and the whole catheter with the deflated balloon can be withdrawn from the body through the incision site. For additional safety and reduction of the pull-out force required, the exaggerated distal end of the catheter&#39;s elongate body can re-sheath the two leg portions of the central catheter wire that engage the branch sections of the balloon. An elastic sleeve can optionally be used to surround the balloon, thereby minimizing the balloon geometry after deflation by applying a biasing load on the balloon. This acts to decrease deflation time, as well as control the timing of inflation over the balloon length or influence the final dimensions during and after inflation.  
           [0013]    According to still another embodiment of the present invention, a method of inserting a side branching stent is disclosed. After the stent is brought beyond the body lumen bifurcation point, the restraining sheath that held the wire sections parallel is removed by pushing farther into the distal direction. The natural bias of the distal junction then forces the predisposed angle between the core wire&#39;s main body and leg portions. Once the angle inherent in the spring bias is established, the catheter is pulled back in proximal direction, causing the catheter to enter the side branch of the lumen that has to be treated. After deployment of the stent, the catheter is pushed into the initial direction of insertion until the remote end of the leg portion is again beyond the body lumen bifurcation point. The catheter sections are then brought into their parallel position by reinsertion into the sheath, and then the whole device is pulled out through the initial insertion location.  
           [0014]    The catheter used to insert the side-branching stent can include an elongate hollow body, a core wire and a release wire. In this configuration, the central catheter core wire may be of hollow tubular construction (as hereinbefore discussed in conjunction with previous embodiments) to permit the placement of at least the release wire or a fluid supply line (if needed) therein. Such an arrangement promotes both relative motion between the components, as well as small footprint of the stent deployment mechanism. 
       
    
    
       [0015]    Other objects and advantages of the invention will become more apparent after reference to the following description, the accompanying drawings and the appended claims.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 shows the first step of the insertion of a stent delivery catheter with balloon, stent and a delivery sheath upon insertion into an aorta, according to an aspect of the present invention;  
         [0017]    [0017]FIG. 2 shows the tendency of the stent, balloon and central catheter wire of FIG. 1 to splay when unsheathed;  
         [0018]    [0018]FIG. 3 shows the placement of the stent, balloon and central catheter wire of FIG. 2 into cooperative engagement with the body lumen bifurcation point;  
         [0019]    [0019]FIG. 4 shows the inflation of the balloon and its expansion effect on the stent;  
         [0020]    [0020]FIG. 5 shows balloon in a deflated condition once the stent has been secured to the aorta and iliac arteries;  
         [0021]    [0021]FIG. 6 shows the tendency of the angle between the central catheter wire leg portions to close when the catheter is moved beyond the body lumen bifurcation point;  
         [0022]    [0022]FIG. 7 shows the retraction of the central catheter wire and the balloon into the sheath of the catheter just prior to removal of the entire assembly from the body lumen;  
         [0023]    [0023]FIG. 8 shows a variation of the stent delivery catheter, where the balloon-expandable stent has been replaced by a self-expanding stent;  
         [0024]    [0024]FIG. 9 shows the use of a stent sheath deployment wire to push the stent and travelling sheaths beyond the body lumen bifurcation point, enabling opening bias similar to that of FIG. 2;  
         [0025]    [0025]FIG. 10 shows the use of the central catheter wire to pull back the stent and sheaths into a seating arrangement with the body lumen bifurcation point similar to that of FIG. 3;  
         [0026]    [0026]FIG. 11 shows the use of mechanical stops connected to the central catheter wire pulled in a proximal direction to effect removal of the travelling sheath from one of the stent branches;  
         [0027]    [0027]FIG. 12 shows the use of the mechanical stops of FIG. 11 pushed in a distal direction to effect removal of the travelling sheath from the stent trunk;  
         [0028]    [0028]FIG. 13 shows the use of the stent sheath deployment wire to pull the travelling sheath off the remaining stent branch, in addition to the use of the central catheter wire to bring the travelling sheaths into operative contact with one another;  
         [0029]    [0029]FIG. 14 shows the use of the reintroduction of the travelling sheaths into the distal end of the catheter prior to withdrawing the catheter from the incision site;  
         [0030]    [0030]FIG. 15 a  shows a stent delivery catheter according to another embodiment of the present invention for use in the insertion of a stent into a body lumen side branch;  
         [0031]    [0031]FIG. 15 b  shows the placement of the stent beyond the body lumen bifurcation point, as well as the tendency of the core and leg portion wires to bifurcate upon removal of the restraining sheath;  
         [0032]    [0032]FIG. 15 c  shows the pulling back of the stent into seating relationship with the body lumen bifurcation point;  
         [0033]    [0033]FIG. 15 d  shows the stent in its expanded condition and placed adjacent an arterial lesion;  
         [0034]    [0034]FIG. 15 e  shows the resheathing and removal of the leg portion wire by pushing the catheter in a distal direction beyond the body lumen bifurcation point;  
         [0035]    [0035]FIG. 15 f  shows the removal of the catheter from the aorta prior to exiting the incision site;  
         [0036]    [0036]FIG. 16 a  shows a stent delivery according to another embodiment of the present invention that includes a pull wire at the distal end of the side branch; and  
         [0037]    [0037]FIG. 16 b  shows the use of the pull wire to pull the distal end back into the delivery sheath once the stent has been delivered to and expanded in its desired location. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0038]    [0038]FIG. 1 shows an aorta  10  with an aneurysm  11  and two common iliac arteries  12   a  and  12   b . According to a first aspect of the present invention, a delivery catheter  20  with proximal and distal ends  20   a  and  20   b , respectively, is shown partially inserted into aorta  10 , carrying with it an uninflated balloon  21  and a bifurcated stent  22  with branch sections  22   a  and  22   b  and trunk section  22   c . The balloon  21  is made up of branches  21   a ,  21   b  and trunk  21   c . Distal end  20   b  of delivery catheter  20  is widened to define a retractable delivery sheath  23  that holds stent branch sections  22   a  and  22   b  in parallel. Although stent  22  is configured representatively as an axial series of expandable rings, connected by a longitudinal backbone elements  22   e  and  22   f  (shown in more detail in FIGS.  4 - 7 ), its geometry can be any conventional expandable kind capable of producing desirable structural properties, and is therefore not described in further detail. The catheter  20  has a hollow core  20   c  that encases a central catheter wire  24 , which is used to translate the balloon  21  and stent  22  relative to the delivery sheath  23  of catheter  20 . The catheter  20 , balloon  21  and stent  22  are inserted into a patient at some remote location, such as in a leg portion (not shown). The catheter  20  is strong and stable enough to enable it to be moved through the body lumen without buckling. It is further desirable that the catheter  20  is made steerable over the range of insertion such that, upon application of a torsional force by a user&#39;s hand, it can be easily rotated and positioned in the patient&#39;s body. In the balloon-expandable genre of stents, hollow core  20   a  further requires a fluid supply line (not shown) to transport expansion fluid from an external source and into the balloon to provide sufficient inflation force.  
         [0039]    The proximal end of central catheter wire  24  includes a first marker  25  to enable a user to check the longitudinal position of the central catheter wire  24  in relation to a second marker  26  located on catheter  20 . Comparison of the distance between markers  25  and  26 , shown as X, allows the user to determine the position of the two branch sections  22   a  and  22   b  relative to the end of delivery sheath  23 . Thus, when the markers  26  and  25  are brought together, their close juxtaposition indicates that the stent  22  and balloon  21  are outside the sheath  23 . The markers  25  and  26  additionally function to provide the user with readily apparent visual information about the rotational position of the two branch sections  22   a  and  22   b  in relation to the position of the two common iliac arteries  12   a  and  12   b . This ensures that, prior to stent expansion, branch  22   b  is in its proper rotational position with respect to iliac artery  12   b , as it points to the right (as depicted in the figure) when branch section  22   b  is aligned with iliac artery  12   b.    
         [0040]    [0040]FIG. 2 shows that once the stent  22  has been inserted beyond body lumen bifurcation point  12   c , the delivery sheath  23  may be retracted so that stent branch sections  22   a  and  22   b  are released, enabling them to open up under their own elastic separating force to create an angle A between them, where they split from the trunk section  22   c  at the stent bifurcating point  22   d . In addition to the aforementioned configurational choices, the elastic properties of the stent can be controlled by proper material choices, where polymers, metals, memory materials with superelastic or temperature dependant behaviour, organic materials, ceramics and combinations thereof can be especially useful. Similarly, such approaches can be used for some of the other elements used to enable catheter functioning, such as the central catheter wire  24  that, through integral bifurcating features, interacts with the opening force of the stent branch sections  22   a ,  22   b . In one example, a suitable material would be Nitinol, a nickel-titanium alloy with shape-memory properties that allow high elastic strain and the stable forces over a high strain range. The branch sections  22   a ,  22   b  of the stent  22  can be programmed to take a preferable parallel position by means of heat treatment of the Nitinol. The tendency of the stent branch sections  22   a ,  22   b  to open up their relative angle can also be influenced by some additional elastic wires, strips, tubes or sheaths, made from Nitinol or any other suitable material. Designed-in elastic properties of stent  22  can alternatively come from the aforementioned backbone-like elements  22   e ,  22   f  that connect a series of ring segments of the stent in an axial direction, or could be stored in some other body, such as a segment of graft material (not shown) brought in place together with the stent  22 .  
         [0041]    Referring now to FIG. 3, the catheter  20  with the uninflated balloon  21  and unexpanded stent  22  are brought into position by pulling back on the catheter  20  until body lumen bifurcation point  12   c  of aorta  10  and stent bifurcation point  22   d  are brought into their desirable relative position. The angular bias provided by the branch sections  22   a  and  22   b  ensures that when catheter  20  is pulled back, stent bifurcation point  22   d  will seat itself adjacent body lumen bifurcation point  12   c . When this occurs, stent  22  is ready for expansion in order to reach the walls of arteries  12   a ,  12   b.    
         [0042]    [0042]FIG. 4 shows stent  22  placed in its final destination in an expanded state, along with inflated balloon  21 . Together, trunk  24   c  and leg portions  24   a ,  24   b  define a central spring element that has the tendency to close the angle A between the stent branch sections  22   a ,  22   b  that gets formed when they bifurcate. To augment the angle-closing bias of the central catheter wire  24 , which is made up of multiple sections, including first leg portion  24   a , second leg portion  24   b  and trunk  24   c , all joined together at bifurcation point  24   d , an additional sleeve or ring can be pulled over bifurcation point  24   d  of the central catheter wire  24 , thereby keeping the leg portions  24   a ,  24   b  together. Despite the tendency of the central catheter wire leg portions  24   a ,  24   b  to go to their preferable parallel position, they are kept open because they touch the inner wall of the stent  22  near bifurcating point  22   d , as shown in the figure. In addition, catheter central wire trunk  24   c  and leg portions  24   a  and  24   b  serve as a framework for the surrounding balloon branches  21   a  and  21   b  and balloon trunk  21   c . The active biasing pressure of the sleeve can determine the threshold pressure for inflation, and so the sequence of expansion of the stent  22  can be controlled. The tendency of the stent  22  branch sections  22   a  and  22   b  to create angle A in FIG. 2 is strong enough to overcome the biasing force of the central catheter wire leg portions  24   a  and  24   b , which would otherwise tend to close the angle A. An example of an elastic element in the stent  22  that has the tendency to open up the angle is shown as the backbone elements  22   e  and  22   f , integrated in the surface of the stent  22 . One or more fluid supply lines (not shown) provide expansion fluid to inflate balloon  21  through, for example, side holes to allow the expansion fluid to enter into the balloon sections  21   a ,  21   b ,  21   c  for inflation. If desired, the pattern and sequence of inflation of the different balloon sections can be controlled in time by having multiple fluid supply lines disposed in catheter hollow core  20   c    24  that are connected to multiple lumens. An alternative method, that only requires a single fluid supply line, is the use of a surrounding biasing sleeve that hinders the inflation of balloon sections in a different way along the length of the balloon.  
         [0043]    [0043]FIG. 5 shows the catheter  20  in the same position as in FIG. 4, with the balloon  21  now deflated. The stent  22  sections  22   a  through  22   d  form a tight fit with the surrounding aorta  10  and arteries  12   a ,  12   b . One or more longitudinally disposed stent backbones  22   e ,  22   f  provide axial structure and stability. Stent  22  can also be used with a graft (not shown) that surrounds, or is surrounded wholly or partly by it. Balloon sections  21   a ,  21   b  and  21   c  return to their smaller, as-inserted diameter and closely surround their respective catheter central wire leg portions and trunk  24   a ,  24   b  and  24   c . This can be achieved by making the balloon  21  from either an elastic material, or by combining an elastic biasing material with a less compliant underlying balloon section (not shown).  
         [0044]    [0044]FIG. 6 shows how the catheter  20  has been moved farther into the iliac artery  12   a  such that the end of leg portion  24   b  and balloon branch  21   b  are clear of body lumen bifurcation point  12   c . This allows the leg portions  24   a ,  24   b  of the catheter central wire  24  spring back to their preferable parallel position, bringing the deflated balloon branches  21   a ,  21   b  with them. The stent  22 , now firmly lodged in aorta  10  and iliac arteries  12   a ,  12   b , is left in place while delivery sheath  23  can be further pushed inward such that its distal end is beyond body lumen bifurcation point  12   c  to engage the now substantially parallel ends of balloon branches  21   a ,  21   b.    
         [0045]    [0045]FIG. 7 shows the catheter  20  with the delivery sheath  23  reinserted over the ends of the balloon branches  21   a  and  21   b  as evidenced by distance X between markers  25  and  26 , to enable removal from the patient&#39;s body. This ensures the narrow cross sectional area and resultant lower friction to minimize the risk of injury that could otherwise be caused by the free end of the central catheter wire leg portion  24   b  piercing the artery wall upon withdrawal. As shown in this figure (as well as FIGS. 5 and 6), the size of the deflated balloon  21  is smaller than the inner diameter of the expanded stent  22  to enable free movement of the balloon  21 , the central catheter wire  24  and its leg portions  24   a ,  24   b  upon removal. In this regard, the use of a biasing sleeve (not shown) around the balloon  21  can be very helpful in not only maintaining the circular cross sectional area of balloon  21  upon deflating, but also by minimizing its size. Further, the active biasing forces of the elastic sleeve can speed the deflation process.  
         [0046]    Referring now to FIG. 8, another aspect of the present invention is shown, where a delivery catheter  120  surrounding a self-expanding stent  122  with branch sections  122   a ,  122   b  and trunk section  122   c , is placed adjacent the aorta  110  with an aneurysm  111  and the two common iliac arteries  112   a  and  112   b . The delivery catheter  120  has a narrow proximal end  120   a  and a wider distal end  120   b  that holds the stent branch sections  122   a  and  122   b  parallel. The inside of catheter  120  is hollow such that it houses central catheter wire  124  in a manner similar to the embodiment shown in FIGS.  1 - 7 , where central catheter wire  124  can be pushed and pulled by the user. Also, as with the previous embodiment, a delivery sheath  123  is defined at the wider distal end  120   b  of catheter  120 . A second, sheath deploying wire  144  (to be discussed in more detail later) is disposed adjacent central catheter wire  124 .  
         [0047]    Referring now to FIGS. 9 and 10, once the various stent sections  122   a ,  122   b  and  122   c  are beyond the body lumen bifurcation point  112   c , the delivery catheter  120  is pulled back to release the stent branch sections  122   a  and  122   b  and enable them to open up. Similar to the first embodiment, central catheter wire  124  is capable of bifurcation, having two branch sections  124   a  and  124   b  that join together with trunk section  124   c  at bifurcation point  124   d . Additionally, travelling sheaths  133   a ,  133   b  and  133   c  are disposed around each of the stent sections  122   a ,  122   b  and  122   c  respectively, such that the stent sections are encased until such time as stent placement and expansion is desired. First mechanical stop  124   e  is configured to engage the inner distal end of travelling sheath  133   c  such that, upon appropriate translational force applied by central catheter wire  124 , travelling sheath  133   c  can be separated from stent trunk section  122   c . FIG. 10 shows with particularity how the catheter  120  with the unexpanded stent branch sections  122   a ,  122   b  and unexpanded stent trunk  122   c , all with travelling sheaths  133   a ,  133   b  and  133   c , are brought into position by pulling back on the catheter  120  in a manner similar to that shown in FIG. 3.  
         [0048]    Referring now to FIG. 11, the distal end of central catheter trunk section  124   b  is connected to the end of travelling sheath  133   b  such that upon the application of a downward translational force imparted by central catheter wire  124  through trunk section  124   b , stent sheath  133   b  moves past the end of stent branch section  122   b , forcing its release, as stent branch section  122   b  assumes its expanded position upon removal of the restraints imposed by travelling sheath  133   b . The engagement point that coincides with the joined distal end of central catheter trunk section  124   b  and the end of travelling sheath  133   b  enables a smoother release (with less likelihood of stent sheath buckling) than when the sheath had to be pushed. The bifurcation point  124   d  of the central catheter wire  124  was originally above the bifurcation point of the stent (as can be seen in FIG. 9); whereas in the present figure it has moved downward while travelling sheath  133   b  was pushed down, with the mechanical stop  124   f  of the main wire has slid downward to engage travelling sheath  133   c . The mechanical stop  124   e  has slid downward together with the central catheter wire  124 . After having pushed out the stent branch section  122   b , the travelling sheath  133   b  is empty and cocoon-like. One way to minimize the size is through the introduction of an elastic biasing sleeve  150  that can be placed around the outer surface of travelling sheath  133   b . The biasing sleeve  150  can be configured from a rather rigid material with a well-defined geometry and maximum inner diameter that fits well around the stent branch section  122   b . For the biasing sleeve around this delivery stent  123 , the function is to compress the inner sleeve with a radial compression force to make it as small as possible. By crushing the travelling sheath  133   b , a smaller diameter results, thus reducing the chances that the now empty sheath  133   b  will catch on the stent branch section  122   b  upon removal of the former from the latter. Accordingly, the biasing sleeve  150  can be any thin-walled conventional material, so long as it provides sufficient force on the travelling sleeve  133   b  to crush the sheath diameter upon release of stent branch section  122   b . The interaction between the compressed stent  122   b , the travelling sheath  133   b  and the biasing sleeve  150  has to be optimized to achieve the best combination of ease of stent delivery plus small cross-sectional profile for the catheter  120  upon removal. This requires that not only must the sheath be capable of being crushed once the stent branch section  122   b  is deployed, but also ensuring that the travelling sheath  133   b  is rigid enough to avoid premature deployment of the stent  122   b  disposed therein.  
         [0049]    [0049]FIG. 12 shows how the central catheter wire  124  trunk section  124   c , working in conjunction with mechanical stop  124   e  has pushed the travelling-sheath  133   c  upward to release the trunk section  122   c  of the stent. The function of mechanical stop  124   e  is that while the central catheter wire  124   c  can slide freely through the hole in the distal end of travelling-sheath  133   c , once it reaches the position of mechanical stop  124   e , the stent-sheath  133   c  is carried along with trunk section  124   c  as it is pushed up. It further shows how the catheter has been moved higher into aorta  110 , where the leg portions  124   a ,  124   b  spring back to their preferable parallel position. Further, a sheath deploying wire  144  with mechanical stop  144   a  is attached to the lower end of the travelling sheath  133   a  to pull it downward. This wire  144  can be disposed substantially parallel to central catheter wire  124  and leave the patient&#39;s body at the proximal end of the catheter  120 , although this is not necessary. A hole in the flange portion of delivery sheath  123  permits the sheath deploying wire  144  to run freely through the delivery sheath  123  of catheter  120  until mechanical stop  144   a  engages the wall of the flanged portion. From that position, the surgeon can pull catheter  120  down, thus removing travelling sheath  133   a  from stent branch section  122   a.    
         [0050]    Referring now to FIG. 13, the central catheter wire  124  has been pulled down to bring the travelling-sheaths  133   a ,  133   b  down through the expanded stent sections  122   c ,  122   a  such that the travelling-sheaths  133   a ,  133   b  are lying beside each other in a substantially parallel arrangement. The cross sectional area of the adjacent travelling-sheaths  133   a ,  133   b  is small enough that they can be inserted into delivery sheath  123 . The engagement of mechanical stop  124   f  with travelling sheath  133   c  has the effect of pulling down travelling sheath  133   c  into contact with the remaining travelling sheaths  133   a ,  133   b  similar to that of the as-inserted position depicted in FIG. 8.  
         [0051]    [0051]FIG. 14 shows the catheter  120  with the delivery sheath  123  shifted upward over the ends of the catheter branch sections  122   a ,  122   b  to enable removal from the patient&#39;s body. Sheath deploying wire  144  with mechanical stop  144   a  now extends from delivery sheath  123 , but lies substantially parallel to the narrow portion of catheter  120  in a tight formation in order to avoid difficulty in removing the catheter from the patient&#39;s body. As with the previous embodiment, it is helpful if the cross-sectional area of the various components are minimized prior to catheter  120  removal from the patient&#39;s body.  
         [0052]    Referring now to FIGS. 15 a  through  15   f , another embodiment of the present invention for use in main-to-side branch body lumens is shown. Here, a single stent  222  is placed into a side branch  210   b  of a body lumen  210 , which is difficult to reach with conventional catheters. Side branches  210   b  that engage the main lumen  210  in an acute angle are amenable to the insertion of a catheter  220  according to the present embodiment of the invention for the purpose of putting an angioplasty balloon (not shown) or stent  222  into place. In FIG. 15 a , such a bifurcating lumen  210  is shown with a lesion  211  in the side branch  210   b  of body lumen  210 . A long core wire  224  includes a main body portion  224   a  and a leg portion  224   b  that are hingedly connected at a distal junction  224   c . The leg portion  224   b  also contains the angioplasty balloon (not shown) or stent  222 . Restraining sheath  223  can hold the core wire&#39;s main body and leg portions  224   a ,  224   b  parallel, and can be moved relative to the stent  222  and the core wire  224  by sheath deploying wire  244 . As with the previous embodiment, both the core wire  224  and the sheath deploying wire  244  include markers  225  and  226  respectively, to assist the user in determining proper angular and translational positioning of the stent within the body lumen  210 . As shown in FIG. 15 b , after bringing the substantially parallel main body and leg portions  224   a ,  224   b  beyond the body lumen bifurcation point  212   c , the sheath  223  that held the sections parallel is removed by sliding it farther through body lumen  210  by pushing on sheath deploying wire  244 . Upon removal of sheath  223  from a significant portion of leg portion  224   b  of core wire  224 , the spring bias forces the now unrestrained remote end to create an angle A with the main body portion  224   a . As shown in FIG. 15 c , the wire  224  and sheath  223  are pulled back toward the body lumen bifurcation point  212   c , while the stent  222  enters the lumen side branch  210   b  with the lesion  211 . As shown in FIG. 15 d , the stent  222  has been expanded by one of the methods as have been described hereinbefore. This can include balloon expansion methods, where the wire takes on a tubular configuration such that it is capable of transporting expansion fluid to the distal end of leg portion  224   b  through its hollow center (not shown). In such a hollow configuration, the core wire  224  could also be used to house one or more, such as sheath deploying wire  244 . This can be further advantageous in situations that employ a wedge ring (discussed below). FIG. 15 e  shows the leg portion and main body portion of core wire  224  being pushed in a distal direction until the remote end of leg portion  224   b  is beyond the body lumen bifurcation point  212   c . FIG. 15 f  shows the leg portion being brought into a substantially parallel position with main body portion of the wire  224 , reinserted into and secured by sheath  223 . After that, the whole device can be pulled out in the proximal direction toward the incision (not shown) without risk.  
         [0053]    Alternative ways to create an angle between the core wire  224  and side branch wire  224   b  are also possible. One example is the proximal actuation of a sliding wedge ring  260  (shown for clarity only in FIG. 15 a ) that is forced between the two parallel wires to push them apart. This embodiment works in conjunction with the embodiment of FIGS. 15 a - 15   f , where the wedge ring  260  may be a separate structure, or may occupy the proximal end of sheath  223  such that it can decouple from the remainder of the sheath. The sheath deploying wire  244 , or another, separate wire (not shown) could be connected to the wedge ring  260  to facilitate is axial movement relative to either the sheath  223 , the core wire  224 , or both. Sliding back of the wedge ring  260  allows the closure of the angle A between main body and leg portions  224   a ,  224   b . The wedge ring  260  can also be used in reverse, where by proximal actuation of the ring, the angle A can be opened by releasing the wire portions so that the bias of the wire portions to splay promotes separation of the leg portion free end from the main body portion.  
         [0054]    Referring now to FIG. 16 a , the restraining means also play an important safety role. Catheter  320  with core wire  324 , side branch wire  324   b  and junction point  324   c  is shown. The tip  324   d  of side branch wire  324   b  is connected to a thin, flexible release wire  330  that follows a shortened path from the proximal end of core wire  324 , toward the junction  324   c  and down core wire  324  to its distal end. The release wire  330  runs inside stent  322 , and is mounted without any tension force. In configurations that utilize balloon angioplasty or related elastic expansion devices, the release wire  330  would be disposed over the outer surface of the balloon (not shown), but still within the unexpanded stent. At the proximal side  310   b  of the body lumen  310 , the pulling force F 0  on the core wire  324  is zero. FIG. 16 b  shows how catheter  320  can be removed once the stent  322  has been inserted. After angioplasty or stenting, the junction point  324   c  is moved distally until the tip  324   d  of the side branch wire  324   b  moves beyond the bifurcation point  312   c  of the body lumen  310 . In order to bring side branch wire  324   b  and core wire  324  in their parallel position, the operator pulls at the proximal end of the release wire  330  with a force F 1 , while core wire  324  is held still, thus forcing tip  324   d  of side branch wire  324   b  to move closer to core wire  324  and finally into delivery sheath  323 . Then the whole device can easily be removed through the side branch  310   b  of the bifurcating lumen  310 . As with the embodiment shown in FIGS. 15 a - 15   f , the core wire  324  can be of hollow tubular construction such that a fluid supply line (not shown) could be disposed inside, thus integrating with a balloon-expandable stent. In another variation, the release wire  330  could be disposed within core wire  324  when the latter is in the aforementioned hollow tubular configuration.  
         [0055]    Other modifications of this invention beyond these embodiments specifically described here may be made without departing from the spirit of the invention. Accordingly, such modifications are considered within the scope of the invention as limited solely by the appended claims.