Abstract:
The present invention tackles the challenging anatomic characteristics of the coronary artery disease in the bifurcation point and the origin of side-branch. The invention has a specifically designed angioplasty balloon catheter, particularly the balloon shape and profile, to be used in the diseased vessels at these difficult anatomic locations. In stent implanting into a coronary artery, a balloon catheter application is an inseparable requirement. A stent is a passive device that cannot be deployed in a diseased or stenosed artery without a pre-stent, with-stent and/or post-stent balloon dilatation. In majority (more than 95%) of available coronary stents, a stent is deployed by balloon expandable mode, meaning that the stent is delivered and expanded inside a vessel lumen by expanding a delivery balloon. This is done by crimping a stent over a folded balloon for delivery into a coronary artery. When expanded by balloon inflation, a stent is expanded and shaped passively by the inflated balloon shape and profile. The balloon catheter is designed to do angioplasty in the bifurcation and side-branch anatomy of coronary arteries, while minimizing the side effect. This specially designed balloon catheter is not only for balloon angioplasty dilatation of the bifurcation and side-branch anatomy, but is also for delivering and deploying specially designed bifurcation or side-branch stents into these difficult anatomic locations, as a stent delivery system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of applicant&#39;s U.S. application Ser. No. 10/943,787 filed on Sep. 9, 2004, for which applicant claims the benefit of its filing date under 35 U.S.C. Sec. 120 and such application is hereby incorporated by reference. This application is also a related application to applicant&#39;s U.S. provisional application Ser. No. 60/499,990 filed Sep. 3, 2003 which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    This invention relates generally to percutaneous balloon coronary angioplasty (PTCA) and coronary stent delivery devices and methods, and more particular to PTCA and coronary stent delivery devices and methods suitable for bifurcation and side-branch anatomies 
         [0004]    2. Description of the Related Art 
         [0005]    By 2002, the percutaneous balloon angioplasty and stent implant procedures have become the dominant non-surgical revascularization method of the atherosclerotic stenosis, or obstruction, of the vascular lumen, and particularly in the coronary vascular system in the heart. With balloon angioplasty alone, without use of stent, the restenosis rate after angioplasty has been as high as 25-35% in the first time clinical cases. With use of bare stents in conjunction with balloon angioplasty, the restenosis was reduced significantly. Even so, the restenosis rate after stent implant is reported as 10-20% range depending on the condition of a vessel stented or what specific stent brand was used, requiring a need for further restenosis reducing measures after intravascular stenting. 
         [0006]    To further reduce the restenosis rate after stent implant, numerous means designed to reduce restenosis rate has been tried, including laser, atherectomy, high frequency ultrasound, radiation device, local drug delivery, etc. Although the brachytherapy (radiation treatment) has proved to be reasonably effective in further reducing restenosis after stent implant, using brachytherapy is very cumbersome, inconvenient and costly. Mainly because it is a radioactive device with a declining isotope half-life, and radiation therapy specialist from another department has to be involved with the interventional cardiologist in the cardiac catheterization laboratory. The laser and atherectomy devices proved to be marginally useful in this purpose with added costs. 
         [0007]    By 2003, drug coated, drug-eluting, stents have been introduced into the U.S. market after an FDA approval. The first U.S. approved drug-eluting stent has Sirolimus, an immune-suppressive drug, as main agent as anti-restenosis. This stent has further reduced a medium term restenosis down to 5-10% range. A cancer treatment drug; Paclitaxol, coated stent is in the clinical testing stage in mid 2003. Both of these drug-eluting stents has changed dramatically the restenosis rate after coronary stent implants. 
         [0008]    With these promising restenosis rate improvements made with the drug-eluting stents, potential prospect for angioplasty and stent implant of bifurcation or side branch lesions of coronary anatomy has also improved. However, successful stent strategy for angioplasty and stenting of bifurcation or side-branch lesions requires two very fundamental elements. First is a specially designed stent that will readily adopt to a set of complex anatomic characteristics of a coronary artery lesion at a bifurcation or side-branch origin, which is far more complex and difficult for a stent to optimally adopt to. A stent that is designed for a regular vessel that is basically a single lumen tubular structure, can not adopt to a multi-lumen and multi-diameter bifurcation lesions. The next requirement is a specially designed angioplasty-stent delivery balloon catheter that is adoptable to the complex anatomic characteristics of a bifurcation or side-branch origin lesions. A specially designed stent cannot be effectively used if there is no specially designed angioplasty-stent delivery balloon catheter that is adopted to the anatomic characteristics of a bifurcation or side-branch origin lesions of coronary artery. 
         [0009]    There is a need for an angioplasty-stent delivery balloon catheter that is adapted to the anatomic characteristics of a bifurcation or side-branch origin lesions of coronary artery. There is a further need for a specially designed angioplasty-stent delivery balloon catheter system for bifurcation or side-branch origin applications. There is yet a further need for a stent that is suited for bifurcation or side-branch lesions. 
       SUMMARY OF THE INVENTION 
       [0010]    Accordingly, an object of the present invention is to provide an improved angioplasty stent delivery balloon catheter. 
         [0011]    Another object of the present invention is to provide an angioplasty stent delivery balloon catheter adapted to the anatomic characteristics of a bifurcation or side-branch origin lesions of coronary artery. 
         [0012]    A further object of the present invention is to provide an angioplasty stent delivery balloon catheter, and stent, that are adapted to the anatomic characteristics of a bifurcation or side-branch origin lesions of coronary artery. 
         [0013]    These and other objects of the present invention are achieved in a balloon catheter for use in a vascular bifurcation or side-branch anatomy. A catheter body is provided. A balloon is positioned at a distal portion of the catheter body. The balloon has a balloon outer skin, a first lumen adapted to receive a guidewire and a second lumen configured to provide inflation and deflation of the balloon. The balloon has a first section with a first average diameter, and second section with a second average diameter that is smaller than the first average diameter. The first and second sections are coupled by a transition section that has a geometry and is sized to reduce vessel damage when positioned at a point of vessel bifurcation. 
         [0014]    In another embodiment of the present invention, an angioplasty balloon catheter is provided for use in a vascular anatomy and includes an angioplasty catheter body. A tubular balloon is coupled to a distal end of the angioplasty catheter body. The tubular balloon includes a shaped balloon skin, a catheter shaft with a first lumen configured to receive a guidewire and a second lumen configured to be provide inflation-deflation of the balloon. The balloon has a shaped outer geometry and is size to reduce vessel damage when positioned at a point of vessel bifurcation. 
         [0015]    In another embodiment of the present invention, a stent delivery device includes a catheter body. A balloon is positioned at a distal portion of the catheter body. The balloon includes a balloon outer skin, a first lumen adapted to receive a guidewire, and a second lumen configured to provide inflation and deflation of the balloon. The balloon has a first section with a first average diameter, and a second section with a second average diameter that is smaller than the first average diameter. The first and second sections are coupled by a transition section that has a geometry and is sized to reduce vessel damage when positioned at a point of vessel bifurcation. A vascular stent is positioned on an exterior of the balloon exterior. 
         [0016]    In another embodiment of the present invention, a method of treating a vascular bifurcation or side-branch anatomy provides a catheter that includes a balloon with a transition section that couples a first section with a second section. The transition section has a geometry and size configured to reduce vessel damage when positioned at a point of vessel bifurcation. A stent is mounted in a non-expanded state on an exterior of the balloon. The catheter with the stent in a non-expanded state is positioned at a vascular bifurcation or a vascular side-branch site. The balloon is inflated. The stent is deployed in an expanded state at the vascular bifurcation or vascular side-branch site. The catheter is removed from the vascular bifurcation or a vascular side-branch site. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]      FIG. 1  is a side view of a balloon catheter of the present invention in an inflated state illustrating the first and second sections with different balloon diameters, coupled together by a transition section and including a balloon marker. 
           [0018]      FIG. 2  is a longitudinal cross-sectional view of the  FIG. 1  balloon catheter. 
           [0019]      FIG. 3(   a ) is the  FIG. 2  balloon catheter with an outer-mounted, expanded stent shaped by the inflated shape of the balloon. 
           [0020]      FIG. 3(   b ) is a longitudinal cross-sectional view of the  FIG. 3(   a ) expanded stent, of the present invention, with the balloon assembly removed from the stent lumen. 
           [0021]      FIG. 4  is a side view of one embodiment of a balloon catheter of the present invention with a deflated and folded balloon illustrating a transition section and dissimilar proximal and distal folded balloon profiles. 
           [0022]      FIG. 5  is a side view of the  FIG. 4  balloon catheter with a stent crimp-mounted over the folded balloon for delivery and deployment. 
           [0023]      FIG. 6  illustrates an over-the-wire embodiment of the  FIG. 1  balloon catheter. 
           [0024]      FIG. 7  illustrates a rapid-exchange embodiment of the  FIG. 1  balloon catheter. 
       
    
    
     DETAILED DESCRIPTION  
       [0025]    Referring to  FIG. 1 , one embodiment of a balloon catheter  10  according to the present invention will now be described. The balloon catheter  10  includes a balloon  12  positioned at a distal portion of catheter shaft  72  (see  FIG. 6 ). The balloon  12  has a balloon outer skin  14 . In this embodiment, balloon  12  may have a first section  16  with a first average diameter and second section  18  with a second average diameter that is smaller than first average diameter. First and second sections  16  and  18  are coupled by a transition section  20  that has a geometry and is sized to reduce vessel damage when positioned at a point of vessel bifurcation. 
         [0026]    Balloon catheter  10  is particularly suited for use in stenting bifurcation or side-branch origin lesions. Balloon catheter  10  is configured to provide proper and/or successfully implantation of a stent at bifurcation or side-branching origin lesions. Coronary bifurcations have variable sets of complex anatomic characteristics that are met with the use of balloon catheter  10  with first section  16 , second section  18  and transition section  20 . Balloon catheter  10  is configured to carry a stent, in a non-expanded state, and deliver the stent to bifurcation or side-branching origin lesions. Balloon  12  is then expanded and molded into an elongated tabular structure by its external shape when inflated with pressurization by a variety of means including but not limited to the introduction of a fluid such as saline and the like. 
         [0027]    In one specific embodiment, a stent is expanded and deployed with a nominal inflating pressure of about 8-10 ATM (atmospheric pressure) that is exerted by balloon  12 . In another embodiment, balloon  12  can be expanded in a pressure of 20 ATM or more. 
         [0028]    Transition section  20  can have a proximal-to-distal step-down between first and sections  16  and  18 . Balloon  12  can include a radiopaque marker  22  to coincide with transition section  20 . Radiopaque marker  22  can be positioned at a number of different locations, including but not limited to, proximal, distal and intermediate positions of transition section  20 . 
         [0029]    Balloon catheter  10  can be utilized as both a balloon angioplasty and a stent delivery system for bifurcation and side-branch origin anatomies of coronary vessels. Balloon catheter  10  can be a modular system, as described hereafter. In a stent implant procedure, particularly in complex anatomic environment like in bifurcation lesions, a pre-stent balloon dilatation of the stenotic lesion is often a pre-requisite. Balloon catheter  10  can be used as a balloon angioplasty device alone, as a pre-stent pre-dilatation device, as a stent delivery tool, and the like. 
         [0030]    In a bifurcation anatomy, if only one side-branch and its origin has a stenotic lesion, balloon  12  is inserted in the side-branch with a distal small diameter segment  18 , and the large main branch with a proximal large diameter segment  16 . Radiopaque marker  22  is used as a guide to position transition section  20  at the bifurcation point under fluoroscopy for either angioplasty or stent delivery purposes. In each procedure, transition section  20  may be placed at the side-branch origin using radiopaque marker  22 , which can coincide with the location of transition section  20 . With balloon  12 , if radiopaque marker  22  is properly positioned at the side-branch origin (i.e., at bifurcation point), the distal small diameter segment  18  and proximal large diameter segment  16  of the balloon tube are properly placed, respectively, in the smaller side-branch and the larger main branch. Similarly, when balloon  12  is used as a stent delivery system for a bifurcation stent, radiopaque marker  22  is the key guide under fluoroscopy to position transition section  20  of a stent  56  at the bifurcation point. 
         [0031]    Stent  56  can be a passive device that is not self expanding. When balloon  12  is inflated, stent  56  is expanded and molded in positioned at the bifurcation anatomy with first section  60  in the main branch, second section  62  in the side-branch and transition section  58  at the bifurcation point (i.e., side-branch origin). Once stent  56  is deployed and expanded, a jail-break balloon dilatation on the stent wall that blocks the distal main branch beyond the side-branch origin is desired. In one embodiment of the present invention, a size of a jail-broken stent cell should match the size and diameter of the vessel distal to the side-branch origin. For this purpose of optimally jail-broken cell size, stent  56  that is specifically designed for bifurcation application can have a properly planned reserve cell boundary for a sufficient stretching into an optimal jail-broken cell size. 
         [0032]    If all three vessel segments of a bifurcation anatomy are affected by an atherosclerotic lesion, (i.e., a proximal main branch and two distal side branches), all three vessel segments of the bifurcation may need angioplasty and stenting. Balloon  12 , as part of a modular system, is effective for this anatomy. First and second sections  16  and  18  can deliver two separate stents at the bifurcation lesion. A first set of balloon  12  delivers and deploys a stent  56  into the first side branch. A proximal larger diameter segment  60  of stent  56  is deployed in the proximal main branch. A distal smaller diameter segment  62  of stent  56  is deployed in the first side-branch, simultaneously. 
         [0033]    After jail-breaking the side-wall of proximal larger segment  60  of stent  56  to open the blocking struts to the distal un-stented branch, a second set of balloon  12  delivers and deploys a stent  56  into the second side branch, repeating the similar procedural steps as the first side-branch stenting. When the second stent is deployed, the main branch proximal to the bifurcation or side-branch point has two over-lapping stent segments  60 . At this point, the side-wall of the proximal larger segment  60  of the second stent struts blocks the orifice of the first side-branch which already was stented. This requires another, second, jail-breaking of the side-wall of the proximal larger segment  60  of the second stent to open the orifice of the first side-branch that received the first stent. 
         [0034]    Balloon  12  can be made both in an over-the-wire exchange system illustrated in  FIG. 6 , and in a rapid-exchange system, as illustrated in  FIG. 7 . Balloon catheter  10  of both a rapid-exchange system and an over-the-wire system can be identical. Balloon catheter  10  is shown with balloon  12  in an inflated side view in  FIG. 1 , a longitudinal cross-sectional view in  FIG. 2 , a folded-balloon view and a stent  56 -mounted view over a balloon  12  in a folded configuration  70 . 
         [0035]    The profile and configuration of balloon  12  is illustrated in an inflated state in  FIG. 1 . Proximal and distal ends  24  and  26  of balloon  12 , respectively, are on a catheter shaft at positions  28  and  30  can be achieved according to well known balloon catheter fabrication methods. A guidewire  32  is in place in a guidewire lumen  34  (see  FIG. 2 ) that runs through a longitudinal axis of a shaft of balloon catheter  10 . 
         [0036]    Also illustrated are a distal tip  36  of balloon catheter  10  and a distal port  38  of guidewire lumen  34 . Balloon  12  has first and second sections  16  and  18  that are coupled with a transition section  20 . Balloon  12  is made of balloon skin  14  and maintains an enclosed balloon lumen  40 . Balloon skin  14  can be made of a variety of different materials, including but not limited to, polyethylene, nylon, PET, other polymer combinations, and the like. It will appreciated that balloon  12  can be made of any suitable material used in fabricating balloon skin  14 . In the  FIG. 1  embodiment, three markers  22 ,  42 , and  44  are provided, and balloon  12  has an inflation-deflation lumen opening  46 . 
         [0037]    Balloon  12  has a dual-diameter balloon silhouette, denoted as first and second sections  16  and  18 . Transition section  20  has a geometry and is sized to reduce vessel damage when positioned at a point of vessel bifurcation. Generally, first section  16  has an average diameter that is larger than an average diameter of second section  18 . First and second sections  16  and  18  can have lengths that are about the same or different, with first section  16  being longer or shorter than second section  18 . 
         [0038]    In the embodiment illustrated in  FIG. 1 , the longitudinal margins of first section  16  of balloon skin  14  are roughly parallel to each other, and diameter is substantially the same along the length of first section  16 . In another embodiment, all or a portion of the longitudinal margins can be non-parallel, such as in a tapered configuration, and at least a portion of the diameters along the length of first section  16  are different. This is the case when first section  16  has a tapered geometry. Similarly, the longitudinal margins of second section  18  can also be roughly parallel to each other as well as non-parallel, such as in a tapered configuration. At least a portion of the diameters of second section  18  can be different. 
         [0039]    Balloon catheter  10  is particularly useful for vascular bifurcation or side-branch anatomies. Balloon catheter  10  may be a balloon angioplasty and stent delivery catheter configured for use in specific anatomic characteristics of a bifurcation or side-branch origin lesions of coronary artery. A bifurcation in coronary anatomy is created when a main branch gives rise to a side branch. A side-branching of coronary anatomy results in a hub that is connected to three separate segments of branches: a main branch proximal to the branching point, a new side branch distal to the branching point and an extension of the main branch distal to the branching point. In this situation, the branching point becomes a bifurcation. In other words, a bifurcation is formed when an artery divides into two distal branches. 
         [0040]    Regarding the side-branch vs. bifurcation anatomic definition, a bifurcation means a dividing point where one coronary artery branch becomes into two branches. Therefore, any side-branch take-off point is technically interchangeable with a bifurcation point. In a practical sense, a side-branch point is a bifurcation point and a bifurcation point is a take-off point of a side-branch. One unique instance is where a main branch divides into two equal sized caliber branches. In this instance, either one of the two bifurcated branches could be called the main branch anymore. Or both could be called bifurcated side-branches. Inmost of these instances of bifurcation vessel anatomy, the main branch before a side-branch take-off, or before two equally bifurcated branches, remains a larger diameter vessel and a side-branch or equally bifurcated branches become smaller caliber vessel(s). For practical purpose, a side-branching and bifurcation can be termed interchangeably in most of the situation, except perhaps in few exceptions. In this disclosure and discussions, bifurcation point and side-branch point is used concurrently or interchangeably. 
         [0041]    The anatomy of a bifurcation can have three different vessel diameters. There can be at least be two different vessel diameters associated with a bifurcation point. When an atherosclerotic lesion develops at a bifurcation, one, two or all three branches can be involved with atherosclerotic plaques. Furthermore, an angle at which a side branch takes off from the main branch also has a wide range of variations. % 
         [0042]    A side-branch arises from the main branch at varying angles of take-off. Balloon catheter  10  is delivered to a side-branch take-off point in a folded delivery mode. Second section  18  enters into the side-branch, while first section  16  stays in the main branch. Balloon  12  dilates both the proximal and distal zones of the side-branch take-off point at the same time. When a folded balloon in delivery mode  60  (as seen in  FIG. 4 ) enters a side-branch, balloon  12  and its shaft bend at an angle to accommodate the angle of take-off of the side-branch from the main branch. A degree of bending of balloon  12  in delivery mode  60  can be determined by a degree of the take-off angle of the side-branch. 
         [0043]    At an insertion stage of balloon catheter  10  for a angioplasty or stenting procedure, placement of balloon  12  in the coronary side-branch point causes a bending of balloon  12  along with the catheter shaft. The exact point of bending of balloon  12  is preferable at transitional section  20  and coincides with the transitional point between the larger diameter proximal branch and the smaller diameter side-branch of coronary anatomy. When balloon  12  is inflated in place, first section  16  stays in the proximal larger caliber main coronary branch, and second section  18  occupies the space in the distal small caliber side-branch. If first section  16  is prolapsed into the smaller caliber side-branch, the small caliber side-branch can have an intimal tear or dissection as a complication. Conversely, if second section  18  is prolapsed into the proximal large diameter main artery, second section  18  can be a cause for a possible serious problems. Proper placement of balloon  12  in the side-branch or bifurcation is critical not only for balloon dilatation but also for stent placement when balloon catheter  10  is used as a stent delivery and deployment vehicle. 
         [0044]    One or more radiopaque markers can be included with balloon catheter  10  to provide for a more precision placement of balloon  12  in a side-branch or bifurcation point. In the Figure-i embodiment, three balloon markers  22 ,  42 , and  44  are provided. One marker  22  is in the middle, another one  42  near or at proximal end  24 , and another one  44  to mark distal end  26  of balloon  12 . 
         [0045]    In one embodiment, radiopaque marker  22  is placed in transition section  20 . In one embodiment, a radiopaque marker  22  is a middle marker designed to indicate the location of the transition section  20  between first section  16  and second section  18 . Middle marker  22  is positioned at transition section  20 , or in sufficiently close proximity, as to enable the operator to position, under fluoroscopy, transition section  20  at the side-branch take-off or bifurcation point in coronary artery during an angioplasty or stenting procedure. Once middle marker  22  and transition section  20  are accurately placed at the bifurcation point of the coronary anatomy, balloon catheter  10  is ready for dilatation at the exact desired location. Radiopaque marker  22  can be circumferentially attached on a catheter shaft  55  inside balloon lumen  48  to accurately indicate the location of transition  20 . Middle marker  22  can be placed near, but not exactly, at the location of transition section  20  and can still accurately indicate the position of transition section  20  under fluoroscopy during an angioplasty procedure. 
         [0046]    A stent  56  is provided that is particularly designed for a bifurcation or side-branch application. In this embodiment, stent  56  has a transition section  58  that is positioned between a first section  60  and a second section  62 . First section  60  has a larger average diameter than an average diameter of section  62 . When crimp-mounting stent  56  for delivery on balloon  12  of the present invention, transition section  58  of stent  56  should also be placed to coincide with middle marker  22  so that stent  56  is deployed accurately at a bifurcation or side-branch by using the reference of middle marker  22  under fluoroscopy during a procedure. Stent  56  is then correctly molded and deployed in the bifurcation or side-branch by dilating the balloon  12  with first and second sections  16  and  18  in the vessel lumen. 
         [0047]    A central shaft of balloon  12  can carry middle marker  22  and inflation-deflation lumen opening  54 . As previously discussed, middle marker  22  indicates the location of transition section  20  but is not necessary located at a position that indicates the center of balloon  12 . A length ratio between first section  16  and second section  18  may be variably changed as necessary. Therefore, the position of transition section  34  may also be variably shifted along the longitudinal length of balloon  12 . In one embodiment, middle marker  22  is designed to follow the location of transition section  34  which may shift up or down the longitudinal axis of balloon  12 , and need not necessarily indicate the center of balloon shaft  44 . 
         [0048]    The location of inflation-deflation lumen opening  54  can be placed at almost any location inside balloon lumen  38 . Many single lumen balloons have an opening in the proximal end of the balloon lumen. In the embodiment illustrated in Figure-i, inflation-deflation lumen opening  54  is placed distal to middle marker  22  and distal to transition section  34 . This particular configuration has a purpose. 
         [0049]    When balloon  12  is inflated in a bifurcation or side-branch take-off point, balloon skin  14  may slide proximally toward the larger diameter side of the vessel anatomy. Inflation-deflation lumen opening  54  inflates second section  18  earlier than first section  16  when inflation-deflation lumen opening  54  is second section  18 . Thus, second section  18  is inflated first and anchors distal end  26  of balloon  12  to prevent sliding of balloon skin  14  proximally into the large caliber main branch of the coronary artery. This may be more significant when balloon catheter  10  is used for stent delivery to a bifurcation or side-branch take-off point. 
         [0050]    By way of illustration, stent  56  can slide forward or backward during a stent deployment phase if the vessel anatomy is in a certain condition, such as the one described above. Because bifurcation or side-branch stenting involves two dissimilar caliber vessels within the length of stent  56 , as discussed in the earlier paragraphs, sliding of stent  56  during deployment can cause undesirable consequences. By inflating second section  18  first and placing inflation-deflation lumen opening  54  in the distal zone, sliding of stent  56  during deployment in a bifurcation or side-branch anatomy may be prevented. 
         [0051]      FIG. 2  illustrates balloon catheter of  FIG. 1  in a longitudinal cross-section diagram. In the  FIG. 2  embodiment, three markers  22 ,  42 ,  44 , guidewire  32  and inflation deflation lumen  54  are shown. Guidewire  32  traverses through guidewire lumen  34 . Balloon  12  is bonded on a catheter shaft at positions  18  and  20 . Distal port  20  of guidewire  32  is also shown. 
         [0052]    Referring now to  FIG. 3(   a ), the same longitudinal cross-sectional view of balloon catheter  10 , from  FIG. 2 , now includes an expanded two-step stent  56  that is in a surrounding position around the balloon  12  which is an inflated, two-step dilation balloon. As indicated earlier, a stent is a very passive device that is generally expanded by balloon inflation. In one embodiment, a self-expanding stent is not used with balloon catheter  10  of the present invention. In  FIG. 3(   a ), stent  56  is passively shaped, forms generally to the geometry of balloon  12  and follows the two-step pattern of sections  16  and  18 . Stent  56 , in an expanded state, has a proximal end  64  and a distal end  66 . In  FIG. 3(   a ), stent  56  has a first section  60  with a larger average diameter than an average diameter of a second section  62 . First and second sections  60  and  62  are joined at a transition section  58 , where a proximal-to-distal step down of a diameter transition of stent  56  occurs. 
         [0053]    First section  60 , second section  62  and transition section  58  of stent  56  are correlated in geometry and size to first section  16 , second section  18  and transition section  20  of balloon  12 . Transition section  58  of stent  56 , transition section  20  of balloon  12  and middle marker  22  of balloon  12  are also correlated. During an angioplasty or stent procedure, middle marker  22  is the guide for the operator to place middle marker  22  at the precise location of a side-branch or bifurcation of coronary artery. In various embodiments, balloon  12  is a two-step angioplasty balloon suitable to perform angioplasty in side-branch lesions of coronary artery, and also as a bifurcation stent delivery system. The two-step/two-diameter configuration of balloon  12  is suitable for delivery and shaping of stent  56  in bifurcation lesions that includes proximal large and distal small caliber vessel branches. 
         [0054]    Referring now to  FIG. 3(   b ), stent  56 , which has the same two-step/dual diameter configuration, is illustrated as being expanded and shaped by balloon  12 , and balloon  12  has been removed. In  FIG. 3(   b ) stent  56  is essentially the same stent as that of  FIG. 3(   a ). Stent  56  has the same proximal end  64  and distal end  66 , along with an expanded lumen  68 . Transition section  58  borders first section  60  and the smaller second section  62 . The shape of expanded stent  56  is a critical element of the design of stent  56  for bifurcation use. Stent  56  is deployed and molded in place in a bifurcation lesion by a stent delivery system that utilizes balloon  12  with the two-step/dual-diameter geometry. Balloon  12  has a geometry that is configured to provide deployment and molding of the shape of stent  56  for its deployment in a bifurcation or side-branch lesion of coronary artery. 
         [0055]      FIG. 4  illustrates a side view of balloon catheter  10  with balloon  12  folded into a low profile shape  70  for angioplasty, or for crimping a stent over the folded balloon  12  for delivery. Balloon catheter  10  has a proximal shaft  72 , a distal shaft portion  73 , distal tip  38  and guidewire  32  positioned in guidewire lumen  34  and runs through the entire length of the catheter shaft. Balloon  12 , in the folded state illustrated in  FIG. 4 , extends from proximal end  74  and distal end  76 . In the  FIG. 4  embodiment, first section  78  has a larger average diameter than that of second section  80 , as well as a larger average diameter than that of transition section  58 . 
         [0056]    With balloon  12  in the  FIG. 4  folded configuration, it is now ready for a balloon dilatation angioplasty. Balloon catheter  10  can be utilized with, classic balloon angioplasty, pre-dilatation angioplasty for stent implant, post-dilation after a stent implant, and the like. As illustrated in  FIG. 4 , balloon  12  is suitable for bifurcation and side-branch anatomies and is shown as being in a folded configuration with a low profile state for a balloon angioplasty application. 
         [0057]    Similarly, balloon  12 , in the folded state, is utilized for the delivery of stent  56 . Stent  56  is crimped over the exterior of folded balloon  12 . When stent  56  is mounted over folded balloon  12 , balloon catheter  10  is ready for a bifurcation stent delivery as shown in  FIG. 5 . 
         [0058]    In  FIG. 5 , stent  56  may be crimp-mounted over the  FIG. 4  folded balloon  12 . In this embodiment, stent  56  is shown in a state that readies it for delivery to a bifurcation or side-branch lesion in a coronary artery. In this embodiment, stent  56  is shown with a proximal end  64  and a distal end  66 , and folded balloon  12  has an exposed proximal end  84  and an exposed distal end  86  that is not covered by stent  56 . In this mounted state, stent  56  has a first section segment  88  coupled by a transition section  90  to a second section  92 . The average diameter of first section  88  is larger then transition section  90  and second section  92 , and the average diameter of transition section  90  is larger than an average diameter of second section  92 . Stent transition section  90 , transition section  77  of folded balloon  12  and radiopaque middle marker  22  underneath are aligned to coincide with each other. By positioning radiopaque marker  22  at a bifurcation or side-branch lesion, under fluoroscopy during a stenting procedure, both folded balloon  12  and stent  56  are automatically and correctly positioned in the bifurcation or side-branch lesion. Stent  56  is then expanded by when folder balloon  12  is inflated at the bifurcation or side-branch lesion. Stent  56  is transformed into the expanded two-step/dual-diameter stent  56  of  FIG. 4 . 
         [0059]    In a real life implementation for a bifurcation or side-branch anatomy, crimp-mounted stent  56  and balloon  12  bend a certain way to conform to the coronary vessel anatomy. In an expanded state, stent  56  also conforms to the coronary vessel anatomy in a certain way, depending on the degree of conformability of the design of stent  56 . 
         [0060]    Stent  56  cannot be expanded and molded into a two-step/dual-diameter stent in a bifurcation or side-branch origin lesion unless it is delivered by balloon  12 . In order words, stent  56  must be expanded by a balloon with has mutli-step/multi diameter geometry. In one specific embodiment, the folded balloon  12  has a first section  78 , second section  80  and transition section  77 . The balloon that deploys stent  56 , e.g., balloon  12  is a two-step/dual diameter balloon. 
         [0061]      FIG. 6  illustrates an embodiment with balloon catheter  10  is shown in an over-the-wire catheter exchange system. As seen in  FIG. 6 , balloon catheter  10  has a first lumen  118  adapted to receive a guidewire  32  and a second lumen  120  configured to provide inflation and deflation of balloon  12 . In this embodiment, balloon catheter  10  has a proximal end  112  and a proximal guidewire lumen opening  118  on the left end of  FIG. 6 , and distal end  36  and a distal guidewire lumen opening  38  on the right end of  FIG. 6 . The proximal end of catheter shaft  72  has a Y-connector  116  with a guidewire lumen opening  118  and an inflation deflation lumen opening  122  with a connection distally to a strain-relief sleeve  130 . Main shaft  72  of catheter  10  encompasses the entire length of catheter  10  from a proximally located Y-connector  116  and traverse through stent delivery balloon assembly  200  and ends in distal shaft  20 . A guidewire  32  is positioned in place through guidewire lumen  34  of catheter  10 . Balloon assembly  200  of balloon catheter  10  has the main business role as a bifurcation or side-branch angioplasty and stent delivery system. Balloon assembly  200  has basically similar configuration as illustrated in  FIG. 5 . 
         [0062]    As illustrated in  FIG. 7 , a two-step/dual-diameter balloon tube assembly  200  is adapted for an angioplasty rapid-exchange catheter system. The distal end segment of the balloon catheter  210 , including balloon assembly  200  and crimp-mounted stent  56 , is exactly the same as  FIG. 6 . The catheter  210  has a proximal end  212  is made of a with an opening  222 . The difference is in proximal end connector  260 , a rapid-exchange proximal guidewire opening  262  and a hard metallic proximal shaft  264  of balloon catheter  10 . Because proximal guidewire opening  262  is on the side of catheter shaft  266 , moved to the distal catheter shaft proximal to balloon assembly  200 , proximal end  212  is made of a simple tubular connector hub  260 , providing an opening  222  for inflation-deflation of distally mounted balloon assembly  200 . A guidewire  32  is entered into guidewire lumen  34  through proximal opening  262 , which is an open orifice made on the side of a soft catheter shaft  266 , and exits through distal guidewire opening  38  at distal end  26  of balloon catheter  210 . As indicated above balloon assembly  200  at the distal end of balloon catheter  210  is same as  FIG. 6 , including the same two-step/dual-diameter balloon tube  12  and the middle radiopaque marker  22 . The exactly same balloon assembly  200  of  FIG. 6  is adapted to a rapid-exchange catheter system as illustrated in  FIG. 7 . 
         [0063]    While the invention has been described and illustrated with reference to certain particular embodiments thereof, those skilled in the art will appreciate that various adaptations, changes, modifications, substitutions, deletions, or additions of procedures and protocols may be made without departing from the spirit and scope of the invention. For example, with any of the above embodiments, the relative diameters of the balloon may be sized as shown in the figures. In one embodiment, the diameter of the larger section of the balloon greater than the diameter of the smaller section. Although not limited to the following, in other embodiments, the average diameter of the larger section of the balloon is about 5%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or other percentages greater than the average diameter of the smaller section of the balloon. Other details can be found in my provisional application U.S. Ser. No. 60/499,990 filed Sep. 3, 2003, which application is fully incorporated herein by reference. 
         [0064]    The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. It is intended that the scope of the invention be defined by the following claims and their equivalents.