Abstract:
Methods and apparatus are provided for inserting a moveable device into a channel such as a vein or artery. The apparatus comprises first and second guide-wires joined by multiple breakable bonds for initially retaining portions of the guide-wires in substantially fixed mutual relationship, the multiple bonds breaking as the moveable device advances along the guide wires. The method comprises inserting the dual guide-wire assembly in the channel with the dual guide-wires initially in fixed relationship to each other and separating the guide-wires by advancing the moveable device along the dual guide-wire assembly sequentially breaking the multiple bonds joining the guide-wires. When the last bond between the wires is broken, the distal tips of the guide-wires are released. The arrangement is especially useful for placing dilation balloons with (or without) stents in bifurcated blood vessels.

Description:
TECHNICAL FIELD 
     The present invention generally relates to means and methods for treatment of partially blocked veins and arteries, and more particularly to improved means and methods for the insertion of bifurcated dilatation balloons and stents. 
     BACKGROUND 
     Dilatation balloons and stents are widely used for the treatment of vascular disorders where partial occlusion of a vein or artery has occurred, for example, from a buildup of plaque or other deposits on an inner wall of a blood vessel. Typically a catheter is moved through the blood vessel from a convenient external entry point to the affected region of the vessel. A guide wire and dilatation balloon are inserted in the catheter and advanced through the catheter and blood vessels to the site. Once in position, the flexible, expandable, preformed dilatation balloon is inflated to a predetermined size with a liquid or gas at relatively high pressures (e.g. about eight to twelve atmospheres) to radially compress the arthrosclerotic plaque in the lesion against the inside of the artery wall and thereby dilate the lumen of the artery. The balloon is then deflated to a small profile so that the dilatation balloon, guide-wire and catheter may be withdrawn from the patient&#39;s vasculature and blood flow resumed through the dilated artery. 
     In order to prevent or reduce restenosis; i.e., a natural re-narrowing of the treated artery, an intravascular prosthesis generally referred to as a stent can be implanted in the affected region. The stent often takes the form of a cylindrically shaped, radially expandable mesh fabricated of, for example, stainless steel or other suitable alloy. The stent is inserted by mounting it in collapsed form over a dilatation balloon, advancing the balloon-stent combination along a guide-wire to the site, and then expanded the balloon and the stent so that the stent is pressed into the inner wall of the blood vessel. The stent overcomes the natural tendency of the vessel walls of some patients to close back down. In this way, normal flow of blood is maintained through the vessel that would not be possible if the stent was not in place. Such procedures and stents are generally known in the art. 
     A particularly difficult problem arises when the blood vessel region to be treated involves a bifurcation, that is, where a single blood vessel divides into two branches. It is much more difficult in this situation to position the dilatation balloon and the stent. Further, where both branches of the bifurcation have plaque deposits, great care must be taken to compress the deposits in both branches as simultaneously as possible to prevent narrowing or closing of one branch while treating the other. 
       FIG. 1  shows bifurcated blood vessel region  10  with main vessel portion  12  and branches  14 ,  16 . A balloon catheter (not shown) has previously been used to compress plaque  18  present in the bifurcation region against inner walls  20 ,  22 ,  24  of vessels  12 ,  14 ,  16  respectively. Stent  26  has been brought to the bifurcation region and expanded against compressed plaque  18  on the inner wall of vessels  12 ,  14 ,  16 . Stent  26  is bifurcated, that is having portion  28  located in main vessel  12 , portion  30  located in branch vessel  14  and portion  32  located in branch vessel  16 . Thus, stent  26  can reduce or delay restenosis. 
     A number of catheter assemblies, methods and stents for treating stenosis in bifurcated regions have been described, for example, in U.S. Pat. No. 6,086,611 to Duffy et al; U.S. Pat. No. 6,129,738 to Lashinski et al; U.S. Pat. No. 6,428,567 to Wilson et al; and U.S. Pat. No. 6,475,208 to Mauch.  FIGS. 2-3  illustrate prior art dilatation balloon-stent assemblies  40 ,  80  used in the prior art to place bifurcated stents. In  FIGS. 2-3 , balloon-stent assemblies  40 ,  80  have dilatation balloon  42  with main vessel portion  44  and branch portions  46 ,  48 . Dilatation balloon  42  is shown un-inflated with stent  50  mounted thereon, ready for insertion. Stent  50  has main vessel portion  52  and branch portions  54 ,  56  located, respectively on balloon portions  44  and  46 ,  48 . Running through dilatation balloon  42  are guide-wires  58 ,  60  where guide-wire  58  passes through dilatation balloon branch  46  and guide-wire  60  passes through dilatation balloon branch  48 . One or both of rounded tips  62 ,  64  on guide-wires  58 ,  60  are often placed at a slight angle to the guide-wire to facilitate penetration into the branch vessel. 
     Assembly  80  of  FIG. 3  differs from assembly  40  of  FIG. 2  in that balloon branch  48  has extension portion  66  attached to distal end  49  thereof and clip  68  provided thereon. Portion  58 - 1  of guide-wire  58  is initially bent down and placed in clip  68  before insertion of assembly  80  through the catheter (not shown) into the affected region of the blood vessel. This aids in keeping branches  46 ,  48  of balloon catheter  42  together during insertion, reducing the chance that tip  62  will snag on an interior wall of the vessel or go into a branch ahead of the site being treated. Once assembly  80  is just in front of the bifurcation, guide-wire  58  is withdrawn slightly until it pops out of clip  68 , so that assembly  80  now takes on an orientation much like assembly  40  in  FIG. 2  as far as tips  62 ,  64  are concerned. Guide-wires  58 ,  60  are then advanced respectively into the bifurcated vessel branches. Then balloon catheter portions  46 ,  48  with stent portions  54 ,  56  are advanced along guide-wires  58 ,  60  to place the balloons and respective stent portions into the vessel branches. Balloon  42  is inflated to expand stent  50  and place it against the inner walls of the vessels. Balloon  42  is then deflated and withdrawn. Stent  50  remains in place. 
     While the above-described apparatus and methods are useful, they suffer from a number of disadvantages. For example, it is often very difficult to advance the dilatation balloon along the guide-wires when the guide-wires become twisted or tangled during insertion. When this happens it is often necessary to withdraw the guide-wires partially or completely and re-insert them. The more the guide-wires and/or balloon assembly are inserted, withdrawn and re-inserted before or after balloon dilatation, the greater the likelihood of damaging the interior wall of the vessel. Damage can occur when one or both of tips  62 ,  64  and/or stent  50  snag on the vessel wall and/or go into a dissection, that is, a fissure in the vessel wall that can arise from the dilatation process. Further, the need to partially withdraw and advance one or more guide-wires to release tips  62 ,  64 , as for example, with the arrangement of  FIG. 3 , can exacerbate this situation. In addition, the very large ratio of length L to diameter D of the guide-wires (typically L/D=10 3  to 10 4 ) means they have very low stiffness, which makes it to difficult to insert them, to control their orientation and to avoid tangling. An increase in stiffness without loss of flexibility is desirable. 
     Accordingly, there continues to be a need for improved means and methods for dilatation balloons and stents to treat vascular stenosis. In particular, there is an ongoing need for means and methods that reduce the need for withdrawing and re-inserting guide-wires, dilatation balloons and/or stents. Further, there is a need for improved means and methods for treating bifurcated regions so that the guide-wire tips can be maintained in fixed relationship to each other during insertion without requiring one or both to be partially withdrawn in order to be released. In addition, there is an ongoing need for means and methods that reduce twisting and/or tangling of the guide-wires during insertion and manipulation of the dilatation balloon and stent. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. 
     BRIEF SUMMARY OF THE INVENTION 
     Methods and apparatus are provided for inserting a medical device into a channel such as a vein or artery, especially one containing a bifurcation. In a preferred embodiment, the medical device comprises a dilatation balloon with or without a stent thereon. The apparatus comprises first and second guide-wires joined by multiple breakable bonds for initially retaining portions of the guide-wires in substantially fixed relationship. The multiple bonds break as the medical device advances along the guide wires toward the distal ends located proximate to the channel bifurcation. When the last bond between the guide-wires is broken, the distal tips of the guide-wires are released and available to guide insertion of, for example, the dilatation balloon (without or without a stent) into the bifurcated region of a vein or artery. The method comprises inserting the dual guide-wire assembly in the channel with the dual guide-wires initially in held fixed relationship to each other by the multiple bonds and separating the guide-wires by advancing the medical device along the dual guide-wire assembly sequentially breaking the multiple bonds joining the guide-wires. In a preferred embodiment, each guide wire passes through a separate branch of the dilatation balloon and guides such branch into the bifurcation channels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and 
         FIG. 1  is a simplified schematic cross-sectional view of a stenotic bifurcated blood vessel in which a stent has been inserted at the bifurcation; 
         FIG. 2  is a simplified side view of a bifurcated stent delivery assembly according to the prior art; 
         FIG. 3  is a simplified side view similar to  FIG. 2  of a further bifurcated stent delivery system according to the prior art; 
         FIG. 4  is a simplified side view of a dual guide-wire assembly for inserting balloon catheters and/or stents, according to the present invention; 
         FIGS. 5A-B  are simplified side views of a portion of the dual guide-wire assembly of  FIG. 4  showing further details and according to first and second embodiments of the present invention; 
         FIGS. 6A-B  are simplified cross-sectional views through the guide-wire assembly portion of  FIGS. 5A-B , respectively; 
         FIG. 7  is a simplified side view of a dilatation balloon being advanced along the dual guide-wire assembly of the present invention; 
         FIG. 8  is a simplified side view similar to  FIG. 7  of a dilatation balloon carrying a stent, being advanced along the dual guide-wire assembly of the present invention; 
         FIG. 9  is a simplified side view of a portion of the dual guide-wire assembly portion of  FIG. 4  showing further details and according to a further embodiment of the present invention; 
         FIG. 10  is a simplified cross-sectional view through the guide-wire assembly of  FIG. 9 ; 
         FIG. 11  is a simplified side view of a portion of the dual guide-wire assembly portion of  FIG. 4  showing further details and according to a still further embodiment of the present invention; 
         FIG. 12  is a simplified cross-sectional view through the guide-wire assembly of  FIG. 11 ; 
         FIG. 13  is a simplified cross-sectional view through the guide-wire assembly of  FIG. 4  according to an additional embodiment of the present invention; 
         FIGS. 14A-B  are simplified cross-sectional views of the dual guide-wire assembly portion of  FIG. 13 , showing further details; 
         FIG. 15  is a simplified side view, similar to  FIG. 4 , of a double dual guide-wire assembly according to a yet further embodiment of the present invention; and 
         FIGS. 16A-C  are simplified schematic illustrations of different guide-wire arrangements for double dual guide-wire assemblies of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
       FIG. 4  is a simplified side view of dual guide-wire assembly  100  for use with balloon catheters and/or stents, according to the present invention. Assembly  100  has first guide-wire  102  with distal tip  104  and proximal end  106 , and second guide-wire  108  with distal tip  110  and proximal end  112 . Tips  104 ,  110  are desirably rounded but any suitable shape may be used. Guide-wires  102 ,  108  are conveniently of Ni—Ti alloy referred to as NITINOL, with a polymer coating. Such polymer coatings are well known in the art. For example and not intended to be limiting, polyamides, urethanes, PBAC or esters are useful polymer coatings. Guide-wires  102 ,  108  typically have diameters D on the order of ˜0.28 mm uncoated and ˜0.36 mm when polymer coated, but larger and smaller diameter wires and wires made of other materials can also be used. Typical guide-wires have lengths L of from 100-500 cm. Tips  104 ,  106  are staggered by distance  114  of the order of 10-150 mm to facilitate insertion in vessel branches. It is useful to have one or both tips  104 ,  110  offset at a slight angle with respect to the axis of the respective guide-wire. In  FIG. 4 , for purposes of illustration and not intended to be limiting, tip  104  is angled and tip  110  is straight. 
     Guide-wires  102 ,  108  are breakably joined or bonded together at multiple locations  116 . Spacing  118  between bonds or joining locations  116  are between approximately 0-200 mm and conveniently 10-150 mm but, as will be subsequently explained, other spacings and substantially continuous bonding or joining of guide-wires  102 ,  108  may also be used. It is important that bonds or joining locations  116  be separable or breakable, that is, that guide-wires  102 ,  108  can be popped apart as a balloon catheter and/or stent are advance from proximal ends  106 ,  112  toward distal ends  104 ,  110  in the direction of arrow  140  in  FIGS. 7-8 . 
       FIGS. 5A-B  are simplified side views of portions  120 ,  122  of the dual guide-wire assembly  100  of  FIG. 4  showing further details and according to first and second embodiments of the present invention.  FIGS. 6A-B  are simplified cross-sectional views through the dual guide-wire assemblies of  FIGS. 5A-B , respectively.  FIGS. 5A-B  illustrated several spaced-apart joining or bonding regions  116 , formed, for example, by applying localized adhesive or adhesive coated connectors  122 ,  124  between guide-wires  102 ,  108 . Reference numbers  116 - 1 ,  116 - 2 ,  116 - 3  . . . etc., are used herein to identify variations in bonding or joining regions  116 . In  FIGS. 5A-6A , plastic connecting members  122  of width  123  and spacing  118  are, for example, adhesively bonded between guide-wires  102 ,  108  at locations  116 - 1 ,  116 - 2 . Some or all of connecting members  122  are scored by groove or slot  126  to facilitate fracture of connecting member  122  in the manner illustrated in  FIGS. 7-8 , but this is not essential. For purposes of illustration, members  122  are shown with groove or slot  126  in region  116 - 1  and without groove or slot  126  in region  116 - 2  in  FIGS. 5A-6A . 
       FIGS. 5B-6B  illustrate use of adhesive  124  to join guide-wires  102 ,  108  in locations  116 - 3 . Adhesive  124  is conveniently injected or squeezed between guide-wires  102 ,  108  at locations  116 - 3 . This is readily accomplished by means well known in the art. While adhesive  124  is shown as being applied at distinct locations  116 - 3  of width  125  and spacing  118 , those of skill in the art will understand based on the explanation herein, that spacing  118  and width  125  of adhesive  124  may be varied, even so much that adhesive  124  is applied substantially continuously between guide-wires  102 ,  108 , except at ends  104 ,  110  and  106 ,  112 . All that is necessary is that guide-wires  102 ,  108  progressively separate when passed through bifurcated dilatation balloon  132  as shown in  FIGS. 7-8 . Those of skill in the art will understand that this is accomplished by controlling the amount and nature of adhesive  124 . This can be determined without undue experimentation depending upon the type of adhesive and cure method selected. A non-limiting example of a suitable adhesive is LOCTITE®-461, available from the Henkel Loctite Corporation, Rocky Hill, Conn. 06067. 
       FIG. 7  is a simplified side view of stenosis treatment assembly  130  comprising dilation balloon  132  having main body  134  and branches  136 ,  138  being advanced along dual guide-wire assembly  100 , in the direction of arrow  140 . Guide-wires  102 ,  108  of assembly  100  are still tied together by bonds or joining regions  116  in portion  142  to the right of dilation balloon  132  in  FIGS. 7-8 , that is, between dilation balloon  132  and distal ends  104 ,  110 . As ends  137 ,  139  of branches  136 ,  138  of dilation balloon  132  moves toward guide-wire ends  104 ,  110 , then in transition region  144  guide-wires  102 , 108  must spread apart to enter the spaced-apart openings in balloon ends  137 ,  139 . This spreading causes bonds or joining regions  1168  near ends  137 ,  139  to fracture or separate so that each guide-wire  102 ,  108  can pass through its respective dilation balloon branch  136 ,  138 , through main body  134  and emerge at proximal end  146  of assembly  130 . A great advantage of the arrangement of assembly  130  using dual guide-wire assembly  100  is that ends  104 ,  110  of guide-wires  102 ,  108  are held in substantially fixed relationship while guide-wires  102 ,  108  and treatment assembly  130  are being inserted in the vein or artery and maneuvered into position before the bifurcation and aligned therewith. Only when dilation balloon  132  is advanced to the distal end of dual guide-wire assembly  100  does last bond or joining location  116 -L break, releasing tips  104 ,  110 . This greatly facilitates insertion and alignment. The arrangement of  FIG. 7  can be used to flatten the plaque in the bifurcation region in preparation for placing a stent therein. 
       FIG. 8  is a simplified side view similar to  FIG. 7  of dilatation balloon  132  of  FIG. 7  carrying collapsed stent  150 , being advanced along dual guide-wire assembly  100  in the direction of arrow  140 . The details of dilatation balloon  132  in  FIG. 8  are the same as in  FIG. 7 . Stent  150  has main body portion  152 , and branch portions  154 ,  156  riding on dilatation balloon main body  134  and branches  136 ,  138 , respectively. The explanation given above with respect to  FIG. 7  also applies to  FIG. 8 , and the same advantages obtain. In particular, having dual guide-wire assembly  100  tied together by bonds or joining locations  116  until just before stent  150  is delivered to the bifurcation is a great advantage. When last bond or joining region  116 -L reaches region  144  proximate to ends  137 ,  139  of dilatation balloon  132 , bond  116 -L breaks or separates thereby releasing tips  104 ,  110  so that stent  150  may be placed in the bifurcated region. 
       FIG. 9  is a simplified side view of portion  160  of the dual guide-wire assembly  100  of  FIG. 4  showing further details and according to a further embodiment of the present invention.  FIG. 10  is a simplified cross-sectional view through the guide-wire assembly portion of  FIG. 9 .  FIGS. 9-10  show further details of guide-wires  102 ,  108  whereby guide-wires  102 ,  108  have central metal cores  102 M,  108 M and polymer coatings  102 P,  108 P, as mentioned earlier. Polymer coatings  102 P,  108 P are fused together in region  162  to provide bonds or joining locations  116 . This is conveniently accomplished by, for example, using lasers or other focused energy beams  164  from sources  166  directed at regions  162  while force is applied as denoted by arrows  168 . Polymer coatings  102 P,  108 P on guide-wires  102 ,  108  desirably have “D-shaped” cross-sections. Wires  102 ,  108  are arranged in  FIGS. 9-10  with the flat sides of the “D” facing each other in proximal relationship. This conveniently increases the surface area where guide-wires  102 ,  108  are to be bonded together, either locally or continuously or a combination thereof. Metal cores  102 M,  108 M can be circular with D-shaped varying thickness polymer coatings as illustrated in  FIG. 10  or metal cores  102 M,  108 M can be D-shaped with a substantially uniform thickness polymer coating. Either arrangement is useful. D-shaped guide-wires  102 ,  108  of either configuration are suitable for use with bonding and joining arrangements illustrated elsewhere herein, e.g., as in  FIGS. 4-16 . 
     However, other joining methods may also be used, as for example and not intended to be limiting, applying a small amount of solvent or adhesive or both in regions  162  to soften and locally bond polymer coatings  102 P,  108 P in response to pressure denoted by arrows  168 . Either of these or other methods well known in the art are useful for creating regions  162  serving as bonds or joining locations  116 . As illustrated in the left half of  FIG. 9 , bond or joining location  116 - 4  formed by regions  162 - 1  of width  163  and separation  118  (see  FIG. 4 ) is provided. However, such bonds or joining locations  116 - 4  from regions  162 - 1  need not be discrete but as illustrated by bond or joining location  116 - 5  formed by region  162 - 2  in the right half of  FIG. 9 , can also be substantially continuous. It is only necessary that assembly  100  using the embodiment illustrated by portion  160  of  FIGS. 9-10  separate when dilatation balloon  132  is advanced in the direction of arrow  140  in  FIGS. 7-8 . Persons of skill in the art will understand based on the description herein that the strength of bonds  116 - 4 ,  116 - 5  can be adjusted by varying the fusion time, power and size of fused region(s)  162  in order to accomplish this. 
       FIG. 11  is a simplified side view of portion  170  of the dual guide-wire assembly  100  of  FIG. 4  showing further details and according to a still further embodiment of the present invention.  FIG. 12  is a simplified cross-sectional view through the guide-wire assembly portion of  FIG. 11 . Portion  170  has wire-guides  102 ,  108  surrounded by plastic tubing  172 . Plastic tubing  172  is preferably shrink-wrap tubing. Shrink-wrap tubing has the property that in its pre-treated state, it has a larger inside diameter and therefore may be easily slipped over combined guide-wires  102 ,  108 . But when heated or otherwise treated, it shrinks to fit closely around the combination of guide-wires  102 ,  108 , thereby holding them firmly together. Shrink-wrap tubing  172  may be applied in discrete portions  172 - 1  of width  173  and spacing  118  (see  FIG. 4 ) to form bonds or joining locations  116 - 6  as illustrated in the left-hand portion of  FIG. 11 , or applied as substantially continuous element  172 - 2  to form substantially continuous bond or joining location  116 - 7  as illustrated in the right-hand portion of  FIG. 11 . 
     To facilitate plastic tubing  172  breaking apart when dilatation assembly  130  of  FIGS. 7-8  advances along dual guide-wire assembly  100  employing arrangement  170 , cutouts  174  and/or scoring grooves  176  may be provided. By controlling the wall-thickness of tubing  172  and the frequency, size and depth of cutouts  174  and/or the size and depth of grooves  176 , the force required to separate guide-wires  102 ,  108  using the arrangement of  FIGS. 11-12  when placed in the configuration of  FIGS. 7-8 , may be advantageously controlled. It is desirably that some adhesive be applied between guide-wires  102 ,  108  and tubing  172  if the arrangement of  116 - 6  is used in order to prevent the upper and/or lower halves of tubing pieces  172 - 1  from separating from wires  102 ,  108  and becoming lodged in the blood vessel being treated. With the arrangement of configuration  116 - 7  where the tubing is substantially continuous, the separated halves of tubing  172 - 2  may be withdrawn when the stenosis treatment assembly  130  is withdrawn. 
       FIG. 13  is a simplified cross-sectional view of guide-wire assembly  100  at location  13 - 13  of  FIG. 4 , and  FIGS. 14A-B  are simplified cross-sectional views taken at right angle to the view of  FIG. 13  at location  14 - 14  of  FIG. 13 , together showing still further details of wire-guide assembly portion  180  illustrating a still further embodiment of the present invention. Joining location  116  of portion  180  of assembly  104  is referred to by reference number  116 - 8  to distinguish it from other implementations of joining location  116 . Joining location  116 - 8  is formed by zipper-like structure  181  wherein teeth  182  extend from guide-wire  102  toward guide-wire  108  and teeth  104  extend from guide-wire  108  toward guide-wire  102 . Teeth  182 ,  184  interlock like the teeth of a zipper, as illustrated in  FIGS. 14A-B .  FIG. 14A  shows zipper-structure  181  of joining location  116 - 8  in the engaged or closed configuration whereby guide-wires  102 ,  108  are temporarily locked together.  FIG. 14B  shows the same region as in  FIG. 14A  but with zipper structure  181  opening as it approaches region  144  in  FIGS. 7-8 . Thus joining location or means  116 - 8  employing zipper structure  181  is locally capable of retaining guide-wires  102 ,  108  in joined configuration, progressively un-zipping as dilatation balloon (with or without stent  150 ) advances toward distal ends  104 ,  110 , whereupon zipper  181  forming joining location  116 - 8  fully opens, thereby releasing guide-wires  102 ,  108  and separating tips  104 ,  110 , as desired. Zipper structure  181  of joining location  116 - 8  is preferably substantially continuous rather than spaced apart, but this is not essential. Zipper teeth  182 ,  184  are conveniently formed of metal or plastic and interlock in much the same way as a conventional zipper for joining cloth or other flexible material. Teeth  182 ,  184  may be attached to guide-wires  102 ,  108  by any convenient means, as for example but not limited to, welding, gluing, crimping around a longitudinal ridge on guide-wires  102 ,  108 , engaging slots in the ridge or in guide-wires  102 ,  108 , combinations thereof or other suitable means well known in the art. 
       FIG. 15  is a simplified side view, similar to  FIG. 4 , but of double dual guide-wire (DDGW) assembly  200  according to a yet further embodiment of the present invention. DDGW assembly  200  is conveniently formed of two dual guide-wire assemblies  100 - 1 ,  100 - 2  constructed according to the principles taught herein. Individual dual guide-wire assemblies  100 - 1 ,  100 - 2  have guide-wires  102 - 1 ,  108 - 1  and  102 - 2 ,  108 - 2 , bonds or joining locations  116 A,  116 C, and tips  104 - 1 ,  110 - 1  and  104 - 2 ,  110 - 2 , respectively. Each dual guide-wire assembly  100 - 1 ,  100 - 2  is suitable for use with dilatation balloon  132  with or without stent  150 . Dual wire-guide assemblies  100 - 1 ,  100 - 2  are conveniently joined by bonds or joining locations  202  of width  203  and spacing  205  analogous to and made generally in the same way as bonds or joining locations  116  (e.g.,  116 - 1 ,  116 - 2 , . . .  116 - 8  or any combination thereof) as described herein. 
       FIGS. 16A-C  are simplified cross-section views through DDGW assembly  200  of  FIG. 15 , showing alternative arrangements of the guide-wires. For simplicity of illustration, cross-hatching has been omitted. In  FIG. 16A , DDGW assembly  200  of  FIG. 15  is shown as being substantially flat, that is with the guide-wires  102 - 1 ,  108 - 1 ,  102 - 2 ,  108 - 2  joined by bonds  116 ,  202  and lying substantially in a common plane. This corresponds to the arrangement shown in  FIG. 15 . However, persons of skill in the art will understand based on the description herein, that DDGW assembly  200  may be folded so that dual guide-wire assemblies  100 - 1  and  100 - 2  are superposed rather than side-by-side. Such alternative arrangements are illustrated in  FIGS. 16B-C . In  FIG. 16B , dual guide-wire assemblies  100 - 1  and  100 - 2  lie one above the other and bonds  202  attach to guide-wires  102 - 1  and  102 - 2  (or  108 - 1  and  108 - 2  or both) at right angles to bonds  116 . While bonds  202  are shown between wires  102 - 1  and  102 - 2 , bonds  202  can also be placed in location  203  between guide-wires  108 - 1  and  108 - 2  or in both locations. In  FIG. 16C , dual guide-wire assemblies  100 - 1  and  100 - 2  are located one above the other but laterally displaced so that they fit together more compactly, making it easier to insert them through the catheter and the blood vessel. In  FIG. 16C , the use of dual bonds  202  is illustrated, but this is not essential. The arrangements of  FIGS. 16A ,  16 B,  16 C are obtained by varying the location of bonds or joining locations  202  around the circumference of the guide-wires. 
     The advantage of DDGW assembly  200  is that it may be inserted into the blood vessel as a unit. The individual guide-wires of DDGW assembly  200  are much less likely to become twisted or tangled, as may happen when guide-wires are inserted individually. With DDGW assembly  200 , one dual guide-wire assembly, e.g.,  100 - 1 , can be used with first dilatation balloon  132 - 1  (e.g., see  FIG. 7 ) to compress the plaque against the inside walls of the vessels. When first dilatation balloon assembly  132 - 1  is advanced along guide-wire  100 - 1  it breaks bonds or joining locations  116 A and bonds or joining locations  202 , leaving second dual guide-wire assembly  100 - 2  unaffected. After the plaque has been compressed against the interior wall of the vessel, first dilatation balloon  132 - 1  can be withdrawn. First guide-wire assembly  100 - 1  is conveniently also withdrawn but may be left in place until the procedure is complete, at the discretion of the user. Second dilatation balloon  132 - 2  with stent  150  thereon can then be advanced along dual guide-wire assembly  100 - 2  to insert the stent at the desired location in the vessel. It is not necessary to withdraw and reinsert any guide-wires since the second set of guide-wires is already in place. Being able to place multiple sets of guide-wires in a vessel in a single insertion is an advantage and can reduce the risk of damage to the walls of the blood vessel that may arise from multiple insertions. By using two or more guide-wires bonded together in the manner described above, there is an increase in stiffness without a significant loss of flexibility. This is an advantage of the present invention. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. For example, while various different arrangements have been illustrated for forming bonds or joining locations  116 ,  202  (e.g.,  116 - 1 ,  116 - 2 , . . . etc.), persons of skill in the art will understand based on the teachings herein that any of the illustrated arrangement may be used in constructing assemblies  100 ,  200  and further that different arrangements may be used in different locations in the same assembly  100 ,  200  depending on the needs and preferences of the user. Both discrete and substantially continuous bonding or joining arrangements have been illustrated for assemblies  100 ,  200  and both are useful, the exact choice depending upon the needs of the user. A combination of discrete and continuous bonding or joining locations may also be used in the same guide-wire assembly. Further, while guide-wires have been mostly illustrated herein as having circular cross-section, this is merely for convenience of explanation and persons of skill in the art will understand that guide-wires of other cross-sectional shape can also be used and are intended to be included in the present invention. 
     It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.