Abstract:
An over-the-wire balloon dilatation catheter has a stainless steel hypotube catheter shaft having a partially collapsed distal region. The partially collapsed region has a convex radius and a concave radius with the degree of collapse increasing distally while maintaining patency. The catheter includes a tubular element which overlaps a distal portion of the partially collapsed region, said tubular element comprising a wire coil disposed about its proximal region and being sealingly bonded within the concave partially collapsed region. The bonding region of the catheter shaft and tubular element is further sealingly disposed within the proximal end of a distal tubular member having a distal inflatable region. The distal end of the tubular element is sealingly disposed within the distal end of the distal tubular member.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation application of U.S. application Ser. No. 10/741,574 filed Dec. 19, 2003, which is a continuation application of U.S. application Ser. No. 09/886,328 filed Jun. 21, 2001, now U.S. Pat. No. 6,733,487, which is a continuation application of U.S. application Ser. No. 09/132,119 filed Aug. 11, 1998, now U.S. Pat. No. 6,273,879, which is a continuation of U.S. application Ser. No. 08/955,049 filed Oct. 21, 1997, which is a continuation of U.S. application Ser. No. 08,657,013 filed May 30, 1996, now U.S. Pat. No. 5,702,439, which is a continuation of U.S. application Ser. No. 08/521,460 filed Aug. 30, 1995, now U.S. Pat. No. 5,522,818, which is a continuation of U.S. application Ser. No. 08/344,931 filed Nov. 23, 1994, which is a continuation of U.S. application Ser. No. 08/035,254 filed Mar. 22, 1993, now U.S. Pat. No. 5,395,334, which is a continuation of U.S. application Ser. No. 07/792,786 filed Nov. 15, 1992, now U.S. Pat. No. 5,217,482, which is a continuation of U.S. application Ser. No. 07/574,265 filed Aug. 28, 1990, now U.S. Pat. No. 5,156,594. 
     
    
     BACKGROUND OF INVENTION 
       [0002]    The present invention relates to the field of angioplasty. In particular, the present invention relates to a dilatation balloon catheter of the “over-the-wire” type having a relatively short distal guide wire lumen extending through the balloon of the catheter. 
         [0003]    Angioplasty procedures have gained wide acceptance in recent years as efficient and effective methods for treating types of vascular disease. In particular, angioplasty is widely used for opening stenoses in the coronary arteries, although it is also used for the treatment of stenoses in other parts of the vascular system. 
         [0004]    The most widely used form of angioplasty makes use of a dilatation catheter which has an inflatable balloon at its distal end. Typically, a hollow guide catheter is used in guiding the dilatation catheter through the vascular system to a position near the stenoses (e.g., to the coronary artery ostia). Using fluoroscopy, the physician guides the dilatation catheter the remaining distance through the vascular system until a balloon is positioned to cross the stenoses. The balloon is then inflated by supplying fluid under pressure through an inflation lumen in the catheter to the balloon. The inflation of the balloon causes stretching of the artery and pressing of the lesion into the artery wall, to reestablish acceptable blood flow through the artery. 
         [0005]    There has been a continuing effort to reduce the profile and shaft size of the dilatation catheter so that the catheter not only can reach but also can cross a very tight stenosis. A successful dilatation catheter must also be sufficiently flexible to pass through tight curvatures, especially in the coronary arteries. A further requirement of a successful dilatation catheter is its “pushability”. This involves the transmission of longitudinal forces along the catheter from its proximal end to its distal end, so that a physician can push the catheter through the vascular system and the stenoses. 
         [0006]    Two commonly used types of dilatation catheters are referred to as “over-the-wire” catheters and “non-over-the-wire” catheters. An over-the-wire catheter is one in which a separate guide wire lumen is provided in the catheter so that a guide wire can be used to establish the path through the stenoses. The dilatation catheter can then be advanced over the guide wire until the balloon on the catheter is positioned within the stenoses. One problem with the over-the-wire catheter is the requirement of a larger profile and a generally larger outer diameter along the entire length of the catheter in order to allow for a separate guide wire lumen therethrough. 
         [0007]    A non-over-wire catheter acts as its own guide wire, and thus there is no need for a separate guide wire lumen. One advantage of a non-over-the-wire catheter is its potential for a reduced outer diameter along its main shaft since no discrete guide wire lumen is required. However, one disadvantage is the inability to maintain the position of the guide wire within the vascular system when removing the catheter and exchanging it for a catheter having a smaller (or larger) balloon diameter. Thus, to accomplish an exchange with a non-over-the-wire catheter, the path to the stenoses rust be reestablished when replacing the catheter with one having a different balloon diameter. 
         [0008]    In an effort to combine the advantages of an over-the-wire catheter with a non-over-the-wire catheter, catheters have been developed which have guide wire lumens which extend from a distal end of the catheter through the dilatation balloon and then exit the catheter at a point proximal of the dilatation balloon. The guide wire thus does not extend through the entire length of the catheter and no separate guide wire lumen is required along a substantially proximal section of the catheter. That proximal section can thus have a smaller outer diameter since it is only necessary to provide an inflation lumen therethrough for catheter operation. A further advantage of this type of modified over-the-wire-catheter is that the frictional forces involved between the guide wire and the shortened guide wire lumen are reduced, thereby reducing resistance to catheter pushability and enhancing the “feel” and responsiveness of the catheter to a physician. 
         [0009]    Perhaps the most significant advantage of using a shortened guide wire lumen is in the ease of exchange of the catheter over the guide wire. In performing an angioplasty procedure using such a catheter, the catheter is “back loaded” over the guide wire by inserting the proximal tip of the guide wire into a distal opening of the guide wire lumen in the catheter. The catheter is then advanced by “feeding” the catheter distally over the guide wire while holding the guide wire stationary. The proximal end of the guide wire will then emerge out of the proximal opening of the guide wire lumen (which is substantially spaced distally from the proximal end of the catheter itself) and is accessible again for gripping by the physician. The catheter can be preloaded onto the guide wire in this manner before the guide wire is inserted into the guide catheter or after. The either case, the guide wire is steered and passed through the guide catheter, coronary vessels and across a lesion. The exposed portion of the guide wire is then grasped while the catheter is advanced distally along the guide wire across the lesion. Using this procedure, little axial movement of the guide wire occurs during catheter loading and positioning for angioplasty. 
         [0010]    If the dilatation balloon is found to be inadequate (too small or too large), the catheter can be similarly withdrawn without removing the guide wire from across the lesion. The guide wire is grasped while the catheter is withdrawn, and when the proximal opening of the guide wire lumen is reached, the grasping hand must be moved incrementally away from the proximal opening as the catheter is incrementally withdrawn, until the catheter is fully removed from the guide catheter and the guide wire is thus again exposed and accessible adjacent to the proximal end of the guide catheter. 
         [0011]    This shortened guide wire lumen type of dilatation catheter design thus offers the advantages associated with the rapid exchangeability of catheters. The design also presents the potential to provide a smaller catheter shaft, since the guide wire is not contained within the proximal portion of the catheter shaft. The smaller catheter shaft thus allows for better contrast media injection and, as a result, better visualization. In addition, because of the rapid exchangeability features, standard non-extendable guide wires of approximately 175 centimeters in length may be used. Further, because the guide wire is contained in only a distal shorter guide wire lumen of the catheter, free wire movement is enhanced when compared to a standard over-the-wire catheter where the guide wire extends through a guide wire lumen extending along the entire length of the catheter. 
         [0012]    While several structures for such shortened guide wire lumen dilatation catheter have been proposed these structures suffer from several disadvantages. Such catheters have been one piece polyethylene catheters having dual lumen configurations adjacent their distal regions. Typically, such catheters have larger than necessary shaft sizes and are stiffer in their distal regions than would be desired, including those portions bearing the dilatation balloon. A further disadvantage is that the proximal shaft portion of such catheters is relatively flexible, and has low column strength shaft, so that it tends to “bunch” and buckle when advanced across a lesion. To counteract this deficiency in such designs, additional stiffener elements have been provided in the shaft, which necessarily require a larger catheter shaft to accommodate the stiffener element structure. The known dilatation balloon catheter designs which include shortened guide wire lumens extending through the distal portion of the catheter suffer from the disadvantages mentioned above and do not take advantage of the unique opportunities presented by the possibilities of such designs in construction and application. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention is an over-the-wire dilatation balloon catheter which has a guide wire lumen extending through only a distal portion of the catheter. The guide wire lumen extends from a distal end of the catheter proximally through a balloon of the catheter and exits the catheter at a point proximal of the balloon, but substantially distally from a proximal end of the catheter itself. 
         [0014]    The present invention for a balloon dilatation catheter includes a thin-walled, high strength metallic tube having a longitudinal inflation lumen extending therethrough from its proximal end to its distal end. An intermediate sleeve section extends distally from the metallic tube. The sleeve section is more flexible than the metallic tube, and includes a proximal segment of inner core tube which has a longitudinal guide wire lumen extending therethrough and an outer sleeve which extends over the proximal segment of the core tube to define a longitudinally extending annular inflation lumen therebetween that is in fluid communication with the inflation lumen of the metallic tube. The guide wire lumen has an outlet at a proximal end of the proximal segment of the core tube, and the core tube has a distal segment which extends distally beyond the distal end of the outer sleeve. Means are provided for exposing the guide wire lumen outlet to the exterior of the catheter adjacent and proximal to the distal end of the metallic tube, without compromising the integrity of the inflation lumens extending through the catheter. An inflatable balloon extends over the distal segment of the core tube and has its proximal end connected to the distal end of the outer sleeve. A distal end of the balloon is connected to the core tube so that an interior of the balloon is in fluid communication with the annular inflation lumen in the sleeve section. Means are provided for preventing significant closure of the guide wire lumen and annular inflation lumen in the sleeve section adjacent the distal end of the metallic tube when the more flexible sleeve section is bent laterally relative to the metallic tube. 
         [0015]    In a preferred embodiment of the present invention, the metallic tube is formed from a proximal relatively long stainless steel tube and a distal relatively short stainless steel tube bonded thereto. The outer diameter of the proximal tube is smaller than the outer diameter of the distal tube, thus providing a catheter structure which is highly trackable and has a generally all shaft cuter diameter, yet is very pushable and responsive to a doctor controlling movement of the catheter from its proximal end. Preferably, the means for exposing includes a longitudinal crimp adjacent the distal end of the distal stainless steel tube. The crimp extends laterally inwardly from one side of the distal tube, and has a proximal transition region and distal bonding region. The proximal end of the inner core tube is nested within the distal bonding region of the crimp and bonded thereto. The outer sleeve extends over at least a distal portion of the bonding region and is sealably affixed thereabout. 
         [0016]    The means for preventing closure of a present invention may take a number of different forms. In a preferred embodiment, the means for preventing closure comprises a coil member affixed to the sleeve section adjacent the distal end of the metallic tube. As such, the coil member may be affixed about the outer sleeve to extend distally from the metallic tube or about the inner core tube to extend distally from the metallic tube. Such a coil member further may have its coils spaced uniformly apart or spaced increasingly apart as it extends distally from the metallic tube. Preferably, the coil member is formed from a spirally shaded ribbon. A compression sheath is provided to envelope the coil member and maintain the coil member in secure engagement to the sleeve section. In an alternative embodiment, the means for preventing closure comprises a tubular member affixed to the sleeve section adjacent the distal end of the metallic tube, with the tubular member being formed from a polyimide material. 
         [0017]    Such closure preventing means thus provide a bending relief design between the relatively stiff metallic tube and more flexible distal region of the balloon dilatation catheter, to prevent kinking during catheter preparation work and handling (prior to insertion of the dilatation catheter into the guide catheter and patient). Such kinking or “crimping” of the catheter can result in a binding on the guide wire as it extends through the guide wire lumen or a reduction in size of the annular inflation lumen between the metallic tube and balloon or a compromise in strength of the catheter tubings, all of which will compromise the utility and responsiveness of the dilatation catheter. In addition, the closure preventing means reduces the possibility of a failure or separation of the bonds adjacent the distal end of the metallic tube which may be caused by excess strain placed on such bonds during catheter preparation or handling. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a side elevational view of a balloon dilatation catheter of the present invention having a distal guide wire lumen therethrough and showing a guide wire. 
           [0019]      FIG. 2  is a sectional side elevational view of the balloon dilatation catheter of  FIG. 1 . 
           [0020]      FIG. 3  is an enlarged sectional view as taken along lines  3 - 3  in  FIG. 2 . 
           [0021]      FIG. 4  is a sectional side elevational view of a portion of the catheter of the present invention, illustrating an alternative structure for a reinforcing coil member thereon. 
           [0022]      FIG. 5  is a sectional side elevational view of a portion of the catheter of the present invention, illustrating an alternative structure for a reinforcing coil member thereon. 
           [0023]      FIG. 6  is an enlarged sectional view as taken along lines  6 - 6  in  FIG. 5 . 
           [0024]      FIG. 7  is a sectional view of a portion of an alternative embodiment of the catheter of the present invention. 
           [0025]      FIG. 8  is a sectional view of a portion of an alternative embodiment of the catheter of the present invention. 
           [0026]      FIG. 9  is a sectional view of a portion of an alternative embodiment of the catheter of the present invention. 
           [0027]      FIG. 10  is a sectional view of a portion of an alternative embodiment of the catheter of the present invention. 
           [0028]      FIG. 11  is a sectional view of a portion of an alternative embodiment of the catheter of the present invention. 
           [0029]      FIG. 12  is a sectional view of a portion of an alternative embodiment of the catheter of the present invention. 
           [0030]      FIG. 13  is a sectional view of a portion of an alternative embodiment of the catheter of the present invention. 
       
    
    
       [0031]    Although the above-identified drawing figures set forth various embodiments of the invention, other embodiments of the invention are also contemplated, as noted in the discussion. In all cases, this disclosure presents illustrated embodiments of the present invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art which will fall within the scope and spirit of the principles of this invention. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Overall Catheter Structure 
       [0032]    A balloon dilatation catheter  20  of the present invention is illustrated generally in  FIG. 1 . The catheter  20  has a proximal main shaft section  22 , an intermediate sleeve section  24  and a distal balloon section  26 . The main shaft section  22  has a proximal end  28  and a distal end  30 . Likewise, the intermediate sleeve section  24  has a proximal end  32  and a distal end  34 . The distal balloon section  26  has a proximal waist  36 , an intermediate expandable segment  38  and a distal waist  40 . 
         [0033]    As illustrated in  FIG. 1 , the distal end  30  of the main shaft section  22  is connected to the proximal end  32  of the sleeve section  24 , and the distal end  34  of the sleeve section  24  is connected to the proximal waist  36  of the balloon section  26 . In use, the catheter  20  is coupled to an inflation device (not shown) by a luer manifold  42  connected to the proximal end  28  of the rain shaft section  22 . The inflation device thus provides or removes inflation solution from the catheter  20  to selectably inflate or deflate the intermediate expandable segment  38  of the distal balloon section  26  (in  FIG. 1 , is expandable segment  38  is shown in its inflated configuration). 
         [0034]    The catheter  20  of the present invention is designed for use in combination with a catheter guide element such as a guide wire  50 . In use in a coronary application, both the guide wire  50  and the catheter  20  are fed through and guided to an arterial lesion by means of a tabular guide catheter (not shown). Both the catheter  20  and guide wire  50  are therefore longer than the guide catheter, with a typical catheter length of approximately 135 cm and a typical guide wire length of approximately 175 cm. As illustrated in  FIG. 1 , the guide wire  50  extends longitudinally along the exterior of the main shaft section  22  of the catheter  20 . Adjacent the distal end  30  of the main shaft section  22 , the guide wire  50  enters the structure of the catheter  20  and extends distally therethrough until it exits the catheter structure adjacent the distal waist  40  of the distal balloon segment  26 . As seen  FIG. 2 , a separate guide wire lumen  52  is provided in the catheter  20  through the intermediate sleeve section  24  and distal balloon section  26  thereof. The guide wire  50  thus is only entrained within the catheter  20  within this guide wire lumen  52 , which is much shorter than the total length of the catheter  20  (e.g., the guide wire lumen  52  is approximately 30 cm long). The guide wire  50  has a proximal end  53  and a distal end  54  and is of a typical structure for guiding angioplasty catheters. At its distal end  54 , the guide wire  50  preferably has a coiled and rounded tip structure which is bendable for steerability of the guide wire. 
         [0035]    Referring now to  FIG. 2 , which shoes the catheter  20  in greater detail, it is seen that the proximal end  28  of the rain shaft section  22  further has a strain relief tube  60  disposed between the luer manifold  42  and shaft section  22 . The strain relief tube  60  is larger than the main shaft section  22 , and thus provides a step-wise strain relief function between the inflexible luer manifold  42  and the more flexible main shaft section  22 . The main shaft section  22 , tubular member  60  and luer manifold  42  are secured together respectively by suitable adhesive means, such as epoxy or cyanoacrylate. 
       Main Shaft Section 
       [0036]    The main shaft section  22  is preferably formed as a thin-walled, high strength stainless steel tube structure, which is referred to as hypodermic tubing or hypotube. As a tubular structure the main shaft section  22  thus has a longitudinally extending inflation lumen  62  extending therethrough from its proximal end  28  to its distal end  30 , which provides a means for the movement and pressurization of inflation fluid through the catheter  20  to and from the distal balloon section  26 . 
         [0037]    In a preferred embodiment, the main shaft section  22  is formed from two stainless steel tube sections, a proximal relatively long shaft section  64  and a distal relatively short shaft section  66 . A distal end of the proximal shaft section  64  and a proximal end of the distal shaft section  66  are sealably affixed together by suitable means, such as by a solder joint. The proximal end of the distal shaft section  66  fits coaxially over the distal end of the proximal shaft section  64 , as seen in  FIG. 2 , thereby allowing the proximal shaft section  64  to assume a smaller outer diameter than the distal shaft section  66 . The main shaft section  22  is provided with a lubricous coating (such as polytetraflouroethylene) to lessen frictional resistance (at least to the extent that the proximal shaft section  64  is so coated). The use of a thin-walled (e.g., 0.003 inch wall thickness), metallic tube structure for the main shaft section  22  thus provides a stiff enough shaft for pushability yet allows for a relatively small diameter shaft, thereby enhancing catheter visualization via fluoroscopy and catheter versatility. The inherent high strength nature of such a structure also allows it to withstand the fluid pressures necessary for proper catheter operation, which in a plastic shaft structure would require thicker walls. The high column strength and thickness of a hypotube shaft also gives improved responsiveness to the catheter. Thus, the balloon and distal regions of the catheter move definitively (in a 1:1 relationship) with motions imparted at the catheter&#39;s proximal end by a physician. This feature allows the physician to actually “sense” the pathway as the catheter is tracked, which gives valuable information in the passage of the catheter to and through the lesion. 
         [0038]    In the distal shaft section  66  of the main shaft section  22 , a longitudinal crimp  68  is provided which extends laterally inwardly from one side of the distal section  66 . The distal shaft section  66  has three sections, a proximal tubular region  70 , a transition region  72 , and a distal bonding region  74 . The crimp  68  extends from its proximal origin in the transition region  72  to its greatest lateral depth in the bonding region  74 . The crimp  68 , as further illustrated in  FIG. 3 , does not seal off or close the inflation lumen  62 , but does transform the inflation lumen from, a circular lumen  62  to a crescent shape through the bonding region  74 , as seen at  63  in  FIG. 3 . 
       Catheter Intermediate Sleeve Section 
       [0039]    The intermediate sleeve section  24  extends distally from the main shalt section  22 , and is bonded thereto adjacent the bonding region  74  of the distal shaft section  66 . The intermediate sleeve section  24  has two primary longitudinal components, an inner core tube  80  and an cuter sleeve or tube  82 . The inner core tube  80  has a proximal segment  84  within the sleeve section  24  and a distal segment  86  within the distal balloon section  26 . The inner core tube  80  and outer sleeve  82  are both preferably formed from thin-walled high density polyethylene. 
         [0040]    The inner core tube  80  has a proximal end  88  and a distal end  90 . At its proximal end  88 , the core tube  80  is nested within the bonding region  74  of the distal shaft section  66  and bonded thereto by suitable means, such as epoxy or cyanoacrylate. The core tube  80  is thus affixed to the main shaft section  22  in an “off-axis” alignment at the bonding region  74 . However, as seen in  FIG. 2 , as the core tube  80  extends distally from the main shaft section  22 , it is aligned generally coaxially with the shaft section  22 . 
         [0041]    The core tube  80  defines the guide wire lumen  52  extending through the catheter  20 . The guide wire lumen thus has a proximal outlet  92  adjacent the proximal end of the core tube  80  and a distal cutlet  94  adjacent the distal end  80  of the core tube  80 . At least one marker band  96  is provided about the core tube  80  (preferably centered within the expandable segment  38  of the distal balloon section  26 ) to aid in illuminating the position of the catheter  20  via fluoroscopy during an angioplasty procedure. 
         [0042]    The cuter sleeve  82  is generally tubular in form, and has a proximal end  100  and a distal end  102 . The outer sleeve  82  is bonded about the distal shaft section  66  and the core tube  80  adjacent the bonding region  74 , as seen in  FIGS. 2 and 3  and is held in place thereto by suitable means, such as epoxy or cyanoacrylate. The outer sleeve  82  extends distally from the main shaft section  22  over the proximal segment  84  of the core tube  80 , and as such, defines a distal continuation of the inflation lumen of the catheter  20 . A longitudinally extending annular inflation lumen  104  is formed between the core tube  80  and outer sleeve  82 . Of course, the proximal end  100  of the outer sleeve  82  is securely sealed about the distal shaft section  66  and the core tube  80  so that the longitudinal inflation lumens  62  and  104  through the catheter  20  are not compromised to the exterior of catheter  20 , but are in fluid communication therethrough. 
         [0043]    The intermediate sleeve structure defined above is the basic sleeve structure for all embodiments of the present invention contemplated and disclosed herein—namely, an inner core tube bonded to a distal portion of the main catheter shaft, with an outer sleeve forming an annular continuation of the inflation lumen through the main shaft between the core tube and outer sleeve. As discussed below and illustrated herein, various configurations of the connections and components relative to the formation of the distal guide wire lumen, including the coupling of the main shaft to the intermediate sleeve section, are contemplated. 
       Catheter Distal Balloon Section 
       [0044]    The distal balloon section  26  is connected to the components of the intermediate sleeve section  24 . The proximal waist  36  of the balloon section  26  is connected to the distal end  102  of the outer sleeve  82  by suitable means, such as by epoxy or cyanoacrylate. The distal waist  40  of the balloon section  26  is bonded to the core tube  80  adjacent its distal end  90  by suitable means, such as by epoxy or cyanoacrylate. An interior  106  of the balloon section  26  is thus sealed and in fluid communication with the annular inflation lumen  104  within the sleeve section  24 . In a preferred embodiment, the balloon section  26  is forced from a compliant balloon material (e.g., polyolefin), although a balloon formed from thin-walled non-compliant material (e.g., PET—polyethylene terephthalate) is also contemplated. 
       Kink-Resistant Structure 
       [0045]    The metallic main shaft section  22  is relatively stiff compared to the polyethylene intermediate sleeve section  24 . This creates a rather abrupt chance in the flexibility of the materials for the catheter  20  adjacent the distal end  30  of the main shaft section  22  (at the bonding region  74 ). The use of a hypotube for the main shaft section  22  in the catheter  20  creates a catheter which is considerably stiffer than most previous over-the-wire angioplasty balloon catheter designs. Such stiffness is not a concern as long as the metallic main shaft section  22  remains in the relatively straight guide catheter within the patient, and indeed such stiffness provides distinct benefits in use of the catheter  20 , as described above. In the distal portions of the catheter  20  (intermediate sleeve section  24  and distal balloon section  26 ), the catheter  20  must be very trackable and flexible in order to negotiate the tortuous coronary anatomy to and across the lesion. The relatively sharp transition in stiffness as the catheter structure changes from the metallic main shaft section  22  to the much more flexible polymer intermediate sleeve section  24  creates two concerns. First, during handling of the catheter prior to usage, there is a potential to kink the catheter structure at that flexibility transition point. Secondly, when the catheter is in vivo, the distal end  30  of the main shaft section  22  could potentially “dig in” to the guide catheter and create excessive friction due to the lack of bending support from a the more flexible intermediate sleeve section  24 . 
         [0046]    To address these concerns, a kink-resistant structure  110  is provided to prevent kinking and possible damage to the intermediate sleeve section  24  during catheter preparation, handling and use. In its simplest form, this kink-resistant structure  110  provides a member of intermediate stiffness or transitory stiffness and kink-resistant nature between the relatively stiff main shaft section  22  and the relatively flexible intermediate sleeve section  24 . The kink-resistant structure  110  includes a coil member  112  affixed to the intermediate sleeve section  24  adjacent the distal end  30  of the main shaft section  22 . The coil member  112  creates an intermediate stiffener element between the relatively stiff main shaft section  22  and the relatively flexible intermediate sleeve section  24  to allow bending of the catheter without kinking. The coil member  112  preferably has its coils spaced uniformly apart, and is preferably formed from a spiral ribbon of stainless steel placed about the outer sleeve  82  along that portion thereof extending over the bonding region  74  and distally therefrom. The coil member  112  is secured to the outer sleeve  82  by suitable adhesive means, such as by epoxy. To further secure the coil member  112  to the intermediate sleeve section  24 , a heat-shrinkable sheath  114  is fitted over the coil member  112 . Preferably the sheath  114  is formed from a polyimide or polyolefin material which is expanded radially outwardly and then shrunk down over the coil member  112  and outer sleeve  82  to secure the coil member  112  thereto. To further secure the sheath  114  and coil member  112  in place, some adhesive is provided between the sheath  114  and the intermediate sleeve section  24 . By covering the ends of the coil member  112 , the sheath  114  also lessens the chances of those ends providing a rough edge or catch as the catheter  20  is advanced through the guide catheter or artery. 
         [0047]    Although the kirk-resistant structure is described and illustrated in connection with a balloon dilatation catheter, it is contemplated that such a structure be employed in any catheter shaft as a transition from a first thin-walled, high strength metallic tube structure to a second tube structure which is more flexible than the metallic tube structure. Such a kink-resistant structure, as described above (and also below in various embodiments), may be employed in a single lumen catheter shaft, or in multiple lumen catheter shaft having a central core tube such as the multi-lumen shaft illustrated by the intermediate sleeve section of the catheter disclosed in  FIGS. 1-4 . 
       Alternative Catheter Embodiment 
       [0048]    Numerous alternative embodiments of the catheter of the present invention are contemplated. For example, several alternative arrangements for the main shaft section and intermediate sleeve structure portion of the catheter are illustrated and discussed herein, but it is not intended that the illustrated embodiments are all inclusive of those structures and designs which are included within the spirit and scope of the present invention. In the following discussion of further alternative embodiments of the present invention, to the extent a component is identical to that of a previously described embodiment, like reference numerals are used. 
         [0049]      FIG. 4  illustrates an alternative embodiment for the distal portion of a catheter according to the present invention. Specifically, the outer sleeve (of the intermediate sleeve section) and the distal balloon section are formed from the same component, as a unitary member. Thus, proximal waist  36 A of distal balloon section  26 A is elongated proximally and acts as the outer sleeve for intermediate sleeve section  24 A. A proximal end  115  of the proximal waist  36 A is sealably fixed about the core tube  80  and main shaft section  22  adjacent the bonding region  74  thereof. It should be understood that the prospect of having a unitary outer sleeve and balloon member is applicable to all embodiments disclosed herein and contemplated, although it is only illustrated and discussed with respect to the catheter structure of  FIG. 4 . 
         [0050]      FIG. 4  also shows another variation for the catheter&#39;s structure illustrated in FIGS.  1 - 3 . In  FIG. 4 , kink-resistant structure  110 A includes coil member  112 A which is defined as a spiral ribbon of stainless steel placed about a proximal portion of the proximal waist  36  along the bonding region  74  and distally therefrom. The coil member  112 A does not have its coils uniformly spaced apart, but rather has its coils spaced increasingly further apart as the coil member extends distally from the main shaft section  22 . This results in a coil member  112 A which becomes increasingly more flexible, thereby “feathering out” the change in relative stiffness and strain or kink relief between the relatively inflexible main shaft section  22  and the relatively flexible intermediate sleeve section  24 A. As before, a heat-shrinkable sheath  114 A is fitted over the coil member  112 A to further secure the coil member  112 A to the sleeve section  24 A. 
         [0051]    In  FIG. 5 , a modified main shaft section  22 B is illustrated. The main shaft section  22 B is formed as a thin-walled, high strength stainless steel tube or hypotube, but is defined as a single tubular shaft  117  from its proximal end to its distal end  30 B. The single shaft  117  has a longitudinally extending inflation lumen  62 B therethrough, and at its proximal end (not shown) the single shaft  117  is mounted to an inflation device in a manner such as that illustrated for the catheter of  FIG. 2 . Adjacent its distal end  30 B, the single shaft  117  has a longitudinal crimp  68 B which extends laterally inwardly from one side of the single shaft  117 . The single shaft  117  thus has three sections, a proximal, relatively elongated tubular region  70 B, a relatively short distal transition region  72 B and a relatively short distal bonding region  74 B. The crimp  68 B extends from its proximal origin in the transition region  72 B to its greatest lateral depth in the bonding region  74 B. The crimp  68 B does not seal or close off the inflation lumen  62 B, but rather transforms the inflation lumen  62 B from a circular lumen to a half-moon lumen through the bonding region  74 B, as seen at  63 B in  FIG. 6 . It is again understood that the use of a single tube to define the main shaft section of the catheter of the present invention is applicable to the other alternative embodiments of the catheter structures disclosed herein. 
         [0052]      FIGS. 5 and 6  also illustrate an alternative arrangement for the kirk-resistant structure of the inventive catheter. Kink-resistant structure  210  includes coil member  212 . The sleeve section  24 B includes an outer sleeve  82 B and an inner core tube  80 B, with the core tube  80 B adapted to be nested within and bonded to the main shaft section  22 B in its distal bonding region  74 B. The coil member  212  of the kink-resistant structure  210  is positioned about the core tube SOB within the distal bonding region  74 B and extending distally therefrom. The coil member  212  is preferably formed from stainless steel (either from a wire or ribbon) and may have uniform coil spacing or increasingly spaced coils as the coil member  212  extends distally from the main shaft section  228 . The coil member  212  is secured to the core tube  80 B by suitable means, such as by embedding the coil member  212  in an epoxy layer  214  about the core tube  80 B. A proximal end  100 B of the outer sleeve  82 B is bonded about the main shaft section  22 B and inner tube  80 B and coil structure  210  in the bonding region  74 B thereof, as seen in  FIGS. 5 and 6 . In the intermediate sleeve section  24 B, the inner core tube  80 B thus provides a guide wire lumen  52 B therethrough, and an annular inflation lumen  104 B is provided, between the inner tube  80 B and outer sleeve  82 B. Although the kink-resistant structure  210  is within the annular inflation lumen  104  and the outer sleeve  82 B necks down distally front the main shaft section  22 B, the size of the annular inflating lumen  104  is sufficient to provide proper fluid flow to and from the catheter&#39;s balloon. 
         [0053]      FIGS. 7-13  illustrate an alternative configuration for that portion of the catheter adjacent the proximal inlet of the guide wire lumen. Instead of providing a crimp structure in the distal end of the main shaft section, an aperture is provided adjacent to and proximal of the distal end of the main shaft section. The aperture is aligned and sealably coupled to the inner tube to define the guide wire lumen proximal outlet. In all disclosed embodiments, the main shaft section is preferably formed from a hypotube-like material. 
         [0054]    As seen in  FIG. 7 , an alternative embodiment of the catheter of the present invention has a proximal main shaft section  22 C formed from thin-walled, high strength stainless steel tubing. A longitudinally extending inflation lumen  62 C extends therethrough from a proximal end of the main shaft section  22 C to its distal end  30 C. In the embodiment seen in  FIG. 7 , the main shaft  22 C is formed from two stainless steel tube sections, a proximal relatively long shaft section  64 C and a distal relatively short shaft section  66 C bonded on the distal end of the proximal section  64 C. This two-part main shaft section structure thus allows a substantial length of the main shaft section  22 C to be formed from the proximal shaft section  64 C which has a smaller diameter than the distal shaft section  66 C. 
         [0055]    The distal shaft section  66 C has an oval-shaped aperture  119  extending through its wall, with the oval being elongated in the longitudinal direction of the main shaft section  22 C. The aperture  119  is spaced proximally from a distal end of the distal shaft section  66 C (the distal end  30 C of the main shaft section  22 C). The space between the aperture  119  and distal end  30 C thus defines in part a bonding region  121  for connecting the main shaft section  22 C to a distally extending intermediate sleeve section  24 C. 
         [0056]    As before, the intermediate sleeve section  24 C includes an inner core tube  80 C and an outer sleeve  82 C. A proximal end  88 C of the core tube  80 C is sealably bonded about the aperture  119  to align the proximal end  88 C and aperture  119  and thereby define a proximal outlet  92 C for a guide wire lumen  52 C extending through the core tube  80 C. As seen in  FIG. 7 , a proximal portion  123  of the core tube  80 C extends laterally from the aperture  119  into the distal shaft section  66 C and turns longitudinally and distally relative thereto to be aligned generally coaxially therewith. As such, the inflation lumen  62 C is continued distally past the aperture  119  as a generally annular inflation lumen  125 , between the core tube  80 C and distal shaft section  66 C (along the bonding region  121 ). Proximal end  100 C of the outer sleeve  82 C is bonded about the distal shaft section  66 C in the bonding region  121  by a suitable means, such as by epoxy or cyanoacrylate. As seen in  FIG. 7 , the outer sleeve  82 C extends distally from the main shaft section  22 C over the core tube  80 C and defines a longitudinally extending annular inflation lumen  104 C between the core tube  80 C and outer sleeve  82 C. The proximal end  100 C of the outer sleeve  82 C is sealed about the distal shaft section  66 C so that the longitudinal inflation lumens  62 C,  125  and  104 C are not compromised to the exterior of the catheter, but are in fluid communication therethrough. 
         [0057]    In  FIG. 7 , kink-resistant structure  310  includes coil member  312  (of a wire or ribbon-like structure) which is bonded about the outer sleeve  82 C to extend distally from the distal end  30 C of the main shaft section  22 C. In this embodiment, the coil member  312  does not extend about any portion of the main shaft  22 C. The coil member  312  is secured to the outer sleeve  82 C by suitable adhesive means, such as epoxy  314 , and is embedded therein to firmly hold the coil member  312  in place about the intermediate sleeve section  24 C. In the embodiment of  FIG. 7 , the coil member  312  is illustrated with its coils being spaced increasingly longitudinally apart as the coil member  312  extends distally along the catheter. 
         [0058]      FIGS. 8-13  also illustrate embodiments of the catheter of the present invention wherein an aperture is provided through the main shaft section wall to accommodate the proximal outlet for the relatively short, distal guide wire lumen. As opposed to the embodiment of  FIG. 7 , however, the embodiments illustrated in  FIGS. 8-13  show the main shaft section as a single shaft rather than as a multi-part shaft. Indeed,  FIG. 8  illustrates a catheter structure identical to that of  FIG. 7 , except that the main shaft section  22 D is shown as a single shaft  217 , rather than having proximal and distal shaft sections  64 C and  66 C as seen in  FIG. 7 . As such, the catheter inflation lumen includes longitudinally extending inflation lumens  62 D,  125 D and  104 D. 
         [0059]      FIG. 9  is an embodiment of the catheter of the present invention otherwise similar to  FIG. 8 , except that kink-resistant structure  410  has coil member  412  with uniformly spaced coils along the entire length. Again, the entire coil member  412  is fixed to the outer sleeve  82 C of the intermediate sleeve section  24 C by embedding the coil member  412  within a suitable material such as epoxy or cyanoacrylate  414 . 
         [0060]    In the catheter structure of  FIG. 10 , intermediate section  24 B has an inner core tube  80 E and an outer sleeve  82 E. The structure of the catheter is otherwise the same as the catheter of  FIG. 9 , except that the kink-resistant structure thereof is positioned inside the outer sleeve  82 E rather than outside of the outer sleeve. Kink-resistant structure  510  is affixed to an inner surface of the outer sleeve  82 E distally of the main shaft section  22 D by a suitable means, such as embedded adhesive  514 . The kink-resistant  510  includes coil member  512  which provides an intermediate stiffener between the relatively stiff main shaft section  22 D and the relatively flexible intermediate sleeve section  24 E. As seen, the outer sleeve  82 E necks down distally from the kink-resistant structure  510  to provide a lower profile for the catheter in its distal regions. An annular inflation lumen  104 E formed between the inner tube  80 E and outer sleeve  82 E (and at a proximal end thereof, between the inner tube  80 B and the kink-resistant structure  510 ) is not compromised by such a necked-down sleeve design but maintained at sufficient size to provide for adequate and quick inflation and deflation of the balloon. 
         [0061]    In  FIG. 11  intermediate sleeve section  24 F includes an inner core tube  80 F and an outer sleeve  82 F. Kink-resistant structure  610  is mounted about the inner tube  80 F along the bonding region  121  and extending distally from the main shaft section  22 D into the intermediate sleeve section  24 F. The kink-resistant structure includes coil member  612  which is affixed about the core tube  80 F by suitable means such as being embedded in epoxy or another suitable adhesive  614 . As seen in  FIG. 11 , the outer sleeve  82 F has an enlarged diameter at its proximal end to accommodate the main shaft section  22 D and the kink-resistant structure  610 , and so that the annular inflation lumens  125 F and  104 F about the core tube  90 F remain sufficiently large to provide proper inflation and deflation pressures to the balloon of the catheter. 
         [0062]      FIGS. 12 and 13  illustrate a further variation of the kink-resistant structure of the present invention. In the embodiments of  FIGS. 12 and 13 , the kink-resistance structure does not include a coil member, is formed from a polymer tube which is of intermediate stiffness between the main shaft section and intermediate sleeve section. In  FIG. 12 , kink-resistant structure  710  is provided which is formed from a polyimide or other stiff polymer tube  727 . The tube  727  is bonded about an inner core tube  80 G of the intermediate sleeve section  24 G by a suitable adhesive, such as epoxy or cyanoacrylate. The tube  727  extends through a distal portion of the bonding region  121  and distally beyond the main shaft section  22 D into the intermediate sleeve section  24 G. Again, an outer sleeve  82 G of the sleeve section  24 G has an enlarged diameter at its proximal end to accommodate the main shaft section  22 D and the kink-resistant structure  710 , and so that the components are dimensioned such that annular inflation lumens  125 G and  104 G are not compromised. 
         [0063]    In  FIG. 13 , kink-resistant structure  810  is illustrated, as formed from a polyimide or other stiff polymer tube  829  which is bonded to the inner surfaces of both the main shaft section  22 D and an outer sleeve  82 H of an intermediate sleeve section  24 H at a bonding region  121 H. The tube  829  thus provides not only a kink-resistant structure to accommodate the change in stiffness of the main shaft section and intermediate sleeve section, but also provides a substrate for bonding the to catheter sections together by a suitable adhesive, such as epoxy or cyanoacrylate. A core tube  80 H of the sleeve section  24 H extends through the interior of the tube  829  to the aperture  119  on the main shaft section  22 D. Thus, an annular longitudinally extending inflation lumen  131  is formed as a “bridge lumen” (between the core tube  80 H and tube  829 ) from the inflation lumen  62 D to an annular inflation lumen  104 H within the sleeve section  24 H. 
         [0064]    As mentioned above, various combinations of these alternative component and catheter structures are contemplated and are intended to be considered, although not explicitly shown. For example, it is contemplated that a two-part main shaft section structure (such as illustrated in  FIGS. 2 ,  4  and  7 ) may be combined with any one of the kink-resistant structure such as that illustrated in  FIGS. 8-13 . By way of example and not limitation, a further example of such a combination may include the use of a distal balloon section having an elongated proximal waist (such as shown in  FIG. 4 ) with any of the alternative kink-resistant structures disclosed herein. 
       CONCLUSION 
       [0065]    The balloon dilatation catheter of the present invention is an over-the-wire catheter structure with a distal guide wire lumen which optimizes the features of such a catheter in a way not previously considered or achieved. The use of a hypotube-type main shaft for the catheter allows the attainment of a high strength, pushable shaft having thin walls and small diameter. The further use of a two-part hypotube shaft structure allows an even smaller diameter for the proximal elongated section of the main catheter shaft. Employing a crimp as a means for aligning and creating a proximal outlet for the relatively short guide wire lumen also serves to provide a transition region for exit of the guide wire from the catheter itself which is relatively gradual. The crimped shaft design also provides additional stiffness in the transition region where the guide wire enters and exits the catheter proximally of the balloon thereof, thereby creating a more rigorous catheter structure. Because the catheter of the present invention is based upon a relatively stiff proximal main shaft section, and such a catheter must have a relatively flexible distal portion for working through the tortuous arterial anatomy, a strain relief or kink-resistant structure is provided to make a more gradual transition between the relatively stiff main catheter shaft and the relatively flexible distal portion of the catheter. Various configurations of strain relief and kink-resistant structures are disclosed herein, and all are believed suitable to accomplish the desired end of preventing significant closure of the guide wire lumen and annular inflation lumen in the more flexible distal portions of the catheter, especially adjacent the distal end of the main catheter shaft. 
         [0066]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.