the present invention is of a method for deploying a stent at or near a bifurcation . specifically , the method of the present invention allows insertion of two wires into two branches of a vessel while avoiding wire entanglement . for purposes of better understanding the present invention , as illustrated in fig2 - 5 of the drawings , reference is first made to the two - wire method of deploying a stent in a vessel bifurcation ( i . e . the prior art ) as illustrated in fig1 a and 1b . in the example illustrated in fig1 a and 1b , the bifurcation , generally designated 2 , involves a main vessel 3 , which splits into a main vessel continuation 4 , and a branch vessel 5 . the point at which the two branches 4 , 5 intersect is commonly called the “ saddle point ” of the bifurcation . the stent to be deployed is generally designated 8 . it includes a proximal end 8 a to be deployed in the main vessel 3 , and a distal end 8 b to be deployed in the main vessel continuation 4 . for this purpose , it is delivered by a stent delivery device , generally designated 10 , to its precise longitudinal position and radial orientation before it is so deployed . the stent delivery device 10 illustrated in fig1 b is a balloon angioplasty catheter , and the stent 8 is outwardly expandable , so that when the stent is precisely positioned within the bifurcation 2 , the inflation of the balloon of the stent delivery device 10 expands the stent to press its proximal end 8 a firmly against the wall of the main vessel 3 , and its distal end 8 b firmly against the wall of the main vessel continuation 4 . the prior art technique illustrated in fig1 a and 1b for precisely locating the stent 8 before its deployment is a two - wire technique . according to this technique , a main guidewire 11 is initially passed through the main vessel 3 , through the bifurcation 2 , and into the main vessel continuation 4 , and a branch guidewire 12 is also initially passed through the main vessel 3 , the bifurcation 2 , and into the branch 5 , as depicted in fig1 a . the main guidewire 11 and the branch guidewire 12 , after being so placed , are then used for tracking the stent delivery device 10 to its proper position before deploying the stent 8 , as depicted in fig1 b . as briefly described above , a serious problem with the two - wire technique illustrated in fig1 is the risk of entanglement or crossover of the two guidewires 11 , 12 , during the movement of the stent delivery device 10 along these guidewires toward the bifurcation 2 . if such an entanglement or crossing of the guidewires should occur , this would generally result in the cardiologist having to pull back the wires and possibly the stent delivery device in order to re - commence the procedure . in doing this , the cardiologist may dislodge the stent or dissect or even puncture the vessel . reference is now made to fig2 a - 2g , depicting a method of deploying a stent according to a preferred embodiment of the present invention . fig2 b - 2f illustrate a stent delivery device , generally designated 20 , to be deployed in a bifurcation corresponding to bifurcation 2 shown in fig1 , namely one including a main vessel 3 split into a main vessel continuation 4 and a branch vessel 5 . as shown in fig2 a , both a main guidewire 21 and a branch guidewire 22 arc initially placed in the main vessel 3 , preferably extending into main vessel continuation 4 . as shown in fig2 b , delivery system 20 is then advanced over both guidewires , with main guidewire 21 being positioned through a main lumen of delivery device 20 and with branch guidewire 22 being positioned through a branch lumen of delivery device 20 , the construction of which will be described in further detail hereinbelow . as shown in fig2 c , branch guidewire 22 is then retracted until its tip is opposite or proximal to the ostium of the branch vessel 5 . subsequently , as shown in fig2 d , branch guidewire 22 is advanced into the branch vessel 5 . next as shown in fig2 e , delivery device 20 is advanced over both wires until the stent is in its optimal position with respect to the ostium of the bifurcation . the stent is then deployed , as shown in fig2 f . finally , delivery device 20 and guidewires 21 and 22 are removed , leaving only the expanded stent 8 in place . in an alternative embodiment , both guidewires 21 , 22 are initially placed in the branch vessel 5 , and delivery system 20 is advanced over the two wires . in the alternative embodiment just described , main guidewire 21 is retracted and subsequently advanced through main vessel 3 and into main vessel continuation 4 . it is essential that guidewires 21 and 22 are both located in the same vessel , whether that vessel is the main vessel 3 , main vessel continuation 4 , or branch vessel 5 . in this way , crossover and entanglement of the wires is minimized . the method described above is particularly useful for rapid exchange systems , such as those disclosed in u . s . provisional patent application ser . no . 60 / 413 , 552 , filed on sep . 26 , 2002 and incorporated by reference herein in its entirety , and described further hereinbelow , and any other rapid exchange system used in stent delivery . the method may also be used for any other delivery system , including over - the wire systems which are well known in the art , as well as systems such as the ones disclosed in pending u . s . patent application ser . no . 09 / 455 . 299 , tiled dec . 6 , 1999 ; ser . no . 09 / 741 , 761 , tiled dec . 18 , 2000 : and ser . no . 09 / 663 , 111 filed sep . 15 , 2000 , all of which are incorporated herein by reference in their entireties and described finer hereinbelow . furthermore , this method may be useful for a dual stent system , in which a ran stent and a side branch stent , or two portions of one stent , are used in the bifurcation . this type of stent may be useful , for example , for drug delivery into a bifurcated vessel . reference is now made to fig3 a - 3f , which illustrate an alternative embodiment of the present invention . fig3 b - 3f illustrate a stent delivery device , generally designated 20 , to be deployed in a bifurcation corresponding to bifurcation 2 shown in fig1 , namely one including a main vessel 3 split into a main vessel continuation 4 and a branch vessel 5 . in the technique illustrated in fig3 a - 3f , a single guidewire is used to track the delivery device 20 . it should be noted that an additional wire may be placed in the blood vessel prior to the procedure described , and that the physician can utilize this additional wire for any one or more of the procedures which precede stent placement , such as , but not limited to , fluoroscope visualization , stentless balloon angioplasty or predilatation , insertion of a visualization catheter , use with additional diagnostic and / or therapeutic devices , etc . however , the additional wire plays no role in the delivery of the device and as such , will generally not be included in the description to follow . as shown in fig3 a , a main guidewire 21 is initially placed through the main vessel 3 , the bifurcation 2 , and the main vessel continuation 4 . as shown in fig3 b , delivery device 20 having a stent 8 thereon is applied to the guidewire 21 , by passing the guidewire 21 through main lumen 12 , and moving the delivery device 20 to its initial position , a preferred embodiment of which is illustrated in fig3 b . in this initial position , the delivery device 20 is located proximal to the proximal end of the bifurcation 2 . in alternative embodiments , delivery device 20 may be initially placed directly opposite or distal to the bifurcation 2 , and then adjusted accordingly . if stent 8 is formed with a side opening 30 , the construction of which will be described further hereinbelow , the stent delivery device may be rotated , so as to radially position the stent properly , e . g ., with the side opening facing the ostium of the branch vessel . however , it should be noted that automatic alignment of the side opening may take place once the branch guidewire 22 is inserted into the branch vessel 5 and the delivery device 20 is advanced . in one embodiment of the invention , the branch guidewire 22 may be pre - loaded in a branch lumen 14 of the delivery device 20 , with the distal end of branch guidewire 22 protruding from a side of the stent , preferably from a designated side hole 30 , so that the branch guidewire 22 is moved with the delivery device 20 to the initial position , a preferred embodiment of which is illustrated in fig3 b . in this embodiment , the distal end of branch lumen 14 may also protrude from the side of the delivery device 20 and the stent 8 carried thereby . in the latter case , brunch guidewire 22 might not protrude from the side of the stent , as it can be advanced to protrude therefrom at a later stage . in an alternative embodiment the branch guidewire 22 would be inserted into branch lumen 14 of the delivery device 20 only after the delivery device 20 has been moved to its initial position . in both embodiments , the distal end of branch guidewire 22 could protrude through side opening 30 in the stent , or through one of the cellular or spiral spaces in the stent or any other opening , if no side opening is present . in either case , when the delivery device 20 has been moved to the vicinity of its initial position , the branch guidewire 22 is manipulated from its proximal end so that its distal end is advanced into the branch vessel 5 , as shown in fig3 c , the delivery device 20 is den further advanced or lacked as the case may be , to its final , stent - deployment position , a preferred embodiment of which is shown in fig3 d . the preferred stent - deployment position of the sent delivery device 20 is the location where the intersection of tee branch guidewire 22 with the balloon 26 ( commonly called the “ crotch point ”) generally coincides with the saddle point of the main vessel continuation 4 and branch vessel 5 , as described , for example , in u . s . pat . no . 5 , 749 , 825 . fig3 d illustrates a preferred embodiment of the final stent - deployment position of the delivery device 20 , wherein the delivery device 20 locates the stent 8 both longitudinally and radially with respect to the bifurcation 2 , after it is tacked over the main guidewire 21 in the main vessel continuation 4 . when the delivery device 20 has been so positioned , the balloon 26 is inflated to thereby expand the stent 8 to firmly press its proximal end 8 a against the inner surface of the main vessel 3 , and its distal end 8 b against the inner surface of the main vessel continuation 4 , as shown in fig3 e . after the stent has been so deployed , balloon 26 is deflated , thereby permitting removal of the delivery device 20 , leaving the stent 8 within the bifurcation 2 , as shown in fig3 f . it will be appreciated that the movement of the delivery device 20 , and the inflation and deflation of the balloon 26 , cam be effected in accordance with known techniques , e . g ., as described in u . s . pat . no . 5 , 749 . 825 . in addition , a self - expandable stent 8 may be used , wherein balloon 26 is not included . it will also be appreciated that if the bifurcation 2 has already received an additional guidewire then this additional guidewire , which is not utilized in the stent positioning methods described herein , is to be removed prior to inflation of the balloon 26 . if the additional guidewire 66 is not so removed , it will be trapped between the expanded stent 8 and the vessel wall . the main guidewire and / or the branch guidewire will typically be last to be removed from the patient vascular system . it should be noted that in this preferred embodiment the branch guidewire 22 is not initially placed into the bifurcation 2 as in the prior art described above with respect to fig1 a , but rather is carried by , or received by , the delivery device 20 before or after the delivery device bas been moved , over the main guidewire , to an initial position near the bifurcation , so that it does not become entangled with or cross over the main guidewire 21 during the positioning of the delivery device 20 . in an alternative embodiment , shown in fig4 , the branch guidewire 22 is used to track the delivery device 20 . as shown in . fig4 , branch guidewire 22 is initially placed through the main vessel 3 , the bifurcation 2 , and the branch vessel 5 . for precisely locating the delivery device 20 with respect to both its longitudinal position and its radial orientation , a main guidewire 21 is used . that is , the main guidewire 21 is not initially placed into the bifurcation 2 as in the prior art described above with respect to fig1 , but rather is loaded into the delivery device 20 before or after the delivery device 20 is advanced over the branch guidewire 22 , to an initial position , and in this alternative embodiment the main guidewire 21 is then advanced through the delivery device 20 , through the stent 8 into the main vessel continuation 4 . the delivery device 20 is then tracked over the main guidewire 21 in the main vessel continuation 4 , and by the branch guidewire 22 in the branch vessel 5 , to its final longitudinal and radial position before the stent 8 carried thereon is deployed with respect to the main vessel 3 and the main vessel continuation 4 . the delivery device 20 may be of a similar construction as that disclosed in pending u . s . patent application ser . no . 09 / 455 , 299 , filed dec . 6 , 1999 ; ser . no . 09 / 741 , 761 , filed dec . 18 , 2000 ; and ser . no . 09 / 663 , 111 filed sep . 15 , 2000 , all of which are incorporated herein by reference in their entireties . in other embodiments , the delivery device 20 may be of a similar construction as other dual lumen delivery devices , such as the one disclosed in u . s . pat . no . 5 , 749 , 825 to fischell et al . briefly , as shown in fig5 , a delivery device 20 may be a catheter with a catheter body 12 and a side member 14 that is adjacent to catheter body 12 . side member 14 may be slidably movable with respect to catheter body 12 or may be attached thereto . in one embodiment , catheter body 12 has a balloon 26 around which a stent 8 is crimped . in another embodiment , stent 8 is self - expandable and balloon 26 is not included . in a preferred embodiment , stent 8 has a side hole 30 for alignment with an ostium of a branch vessel . various types of side hole are described in u . s . provisional patent application no . 60 / 404 , 756 , filed aug . 21 , 2002 , incorporated herein by reference in its entirely . side hole 30 may be of various shapes and sizes , and may also have a portion designed to partially extend into the branch vessel . in an alternative embodiment of the present invention , a rapid exchange delivery system is used , such as the one described in u . s . provisional patent application ser . no . 60 / 413 , 552 , filed on sep . 26 , 2002 and incorporated by reference herein in its entirety . a system such as the one described is shown in fig6 . the system disclosed in the above - referenced patent application and shown in fig6 is a rapid exchange system with a dual lumen catheter , specifically designed for vessel bifurcations . as shown in fig6 , delivery device 20 has exit ports 23 and 25 for the main guidewire 21 and branch guidewire 22 , respectively , which exit ports are located at a distance of approximately 1 to 150 cm from the distal end of delivery device 20 . in a preferred embodiment , the exit ports 23 and 25 are located at a distance of approximately 10 to 20 cm from the distal end of delivery device 20 . in an exemplary preferred embodiment , the exit ports 23 and 25 are located at a distance of 15 cm from the distal end of delivery device 20 . in this system , a three - way bond is created at exit ports 23 and 25 , maintaining three lumens : exit ports 23 and 25 , and a lumen for fluid infusion for inflation of balloon 26 . in alternative embodiments , delivery device 20 is used for delivering guidewires 21 and 22 to a main vessel continuation 4 and a branch vessel 5 , without having a stent placed on the delivery device 20 . an example of such a delivery device includes a catheter with a two - headed balloon or a dual lumen balloon . in this embodiment , delivery device 20 may be of a similar construction as that disclosed in pending u . s . patent application ser . no . 09 / 816 , 690 , filed mar . 22 , 2001 , and incorporated by reference in its entirety . briefly , delivery device 20 has two lumens 32 and 34 passing therethrough . as can be seen in fig6 , lumen 32 has a distal end opening 13 which is preferably disposed at or near the end of the delivery device . lumen 34 has a distal end opening 15 which is preferably disposed at a location some distance proximal to the distal end of the delivery device 20 . main branch guidewire 21 ( not shown ) is receivable through lumen 32 and branch guidewire 22 ( not shown ) is receivable through lumen 34 . while the invention has been described with respect to two preferred embodiments , it will be appreciated that these are set forth merely for purposes of example , and that many other variations , modifications and applications or the invention may be made . it should be readily apparent that either the two - wire method illustrated in fig2 a - 2g , or the one wire method illustrated in fig3 a - 3f may be used for introducing the wires of any of the delivery devices described herein , or any other delivery device in which two wires are needed . although the invention has been described in conjunction with specific embodiments thereof , it is evident that many alternatives , modifications and variations will be apparent to those skilled in the art . accordingly , it is intended to embrace all such alternatives , modifications and variations that fall within the spirit and broad scope of the appended claims . all publications , patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification , to the same extent as if each individual publication , patent or patent application was specifically and individually indicated to be incorporated herein by reference . in addition , citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention .
a method of deploying a stent in a bifurcation includes introducing two guidewires through the main vessel and using the two guidewires for guiding a dual lumen catheter carrying a stent first to an initial position proximal to the stent deployment position , retracting one wire , and projecting it from the catheter and through a side of the stent a branch guidewire into the second branch vessel , and then moving the catheter to the predetermined deployment position while guided by the main guidewire in the first branch vessel , and the branch guidewire in the second branch vessel . the stent is then expanded , and the catheter is removed with the stent remaining in its deployed position an alternative embodiment includes introducing one wire , advancing the system over the one wire and subsequently introducing the second wire .