Abstract:
Balloon catheters such as guide catheters can be configured to provide distal occlusion, while still providing sufficient interior lumen space for device delivery. Such catheters can provide a desired level of balloon expansion, yet prevent vessel damage caused by balloon over-expansion. A catheter can include an elongate shaft having a distal region, a proximal region and a lumen extending therebetween. A balloon is inflated to a desired expansion configuration with a desired diameter. Over-inflation of the balloon causes longitudinal expansion instead of increased radial expansion, thus maintaining the diameter of the balloon.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates generally to catheters and more specifically to intravascular catheters that include an occlusion balloon to restrict blood flow during treatment.  
       BACKGROUND OF THE INVENTION  
       [0002]     Balloon catheters are used in a number of surgical applications including occluding blood flow either distally or proximally of a treatment site. The inflation of the balloon must be controlled in order to avoid over expansion or rupture of the balloon, which may rupture or otherwise damage the vessel.  
         [0003]     Reinforced balloons that only expand to a predetermined diameter are effective in reducing over-expansion of the balloon, but are limited to use in a specific sized vessel. Similarly, the use of a non-expandable sheath over the balloon may prevent over-inflation, but the size of the sheath limits the size of the vessel in which the system can be used.  
         [0004]     A need remains for a balloon catheter that can provide the desired level of inflation while minimizing the risk of over-inflation.  
       SUMMARY OF THE INVENTION  
       [0005]     The invention is directed to balloon catheters, such as those configured for providing proximal or distal occlusion, that minimize the risk of over-expansion while still providing sufficient inflation. In one embodiment, the balloon catheter has an elongate shaft with a lumen and an inflatable balloon disposed over a distal region of the shaft. The balloon includes a distal portion that is configured to expand to a first, desired, expansion configuration when a first amount of fluid is inserted into the balloon. When pressure in increased by adding more fluid such that the balloon is over-inflated, it expands to a second expansion configuration. The diameter of the inflated balloon in the first expansion configuration is substantially the same as the diameter of the over-inflated balloon in the second expansion configuration, yet force against the vessel wall does not increase substantially due to expansion of a proximal portion of the balloon which generally does not expand at the first pressure.  
         [0006]     Accordingly, an example embodiment of the invention is a balloon catheter in which a proximal portion of the balloon is releasably attached to the shaft such that this proximal portion is released and inflated when excess inflation fluid is inserted into the balloon.  
         [0007]     Another embodiment of the invention is a balloon catheter in which the proximal portion of the balloon is thicker than the distal portion such that injection of a first amount of inflation fluid causes the distal portion to inflate while the proximal portion remains in a collapsed configuration. When a greater amount of inflation fluid is injected into the balloon, the proximal portion inflates, resulting in increased longitudinal expansion while maintaining a substantially constant radial expansion against the vessel wall without excessive force that could cause damage or excessive pressure that could cause balloon failure.  
         [0008]     The balloon catheter can be a multi-lumen catheter or a single lumen catheter. In a multi-lumen catheter, the balloon may be disposed such that it receives inflation fluid from an outer lumen, leaving an inner lumen available for delivery of various medical instruments or fluids. In a single lumen catheter, the balloon may be disposed such that a distal portion of the balloon overlies inflation ports in the catheter shaft, and a proximal portion of the balloon overlies a solid portion of the shaft. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:  
         [0010]      FIG. 1  is a cross-sectional view of the distal region of a balloon catheter in accordance with an embodiment of the invention;  
         [0011]      FIG. 2  is a cross-sectional view of the balloon catheter of  FIG. 1  with the balloon inflated to a first inflation configuration;  
         [0012]      FIG. 3  is a cross-sectional view of the balloon catheter of  FIG. 1  with the balloon inflated to a second inflation configuration;  
         [0013]      FIG. 4  is a cross-sectional view of the distal region of a balloon catheter in accordance with another embodiment of the invention;  
         [0014]      FIG. 5  is a cross-sectional view of the balloon catheter of  FIG. 4  with the balloon inflated to a first inflation configuration;  
         [0015]      FIG. 6  is a cross-sectional view of the balloon catheter of  FIG. 4  with the balloon inflated to a second inflation configuration;  
         [0016]      FIG. 7  is a cross-sectional view of the distal region of a balloon catheter in accordance with another embodiment of the invention;  
         [0017]      FIG. 8  is a cross-sectional view of the balloon catheter of  FIG. 7  with the balloon inflated to a first inflation configuration;  
         [0018]      FIG. 9  is a cross-sectional view of the balloon catheter of  FIG. 7  with the balloon inflated to a second inflation configuration;  
         [0019]      FIG. 10  is a cross-sectional view of a balloon catheter in accordance with another embodiment of the invention, inflated to a first configuration; and  
         [0020]      FIG. 11  is a cross-sectional view of a balloon catheter in accordance with another embodiment of the invention, inflated to a first configuration. 
     
    
     DETAILED DESCRIPTION  
       [0021]     For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.  
         [0022]     All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure.  
         [0023]     The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).  
         [0024]     As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.  
         [0025]     The following description should be read with reference to the drawings wherein like reference numerals indicate like elements throughout the several views. The drawings, which are not necessarily to scale, depict illustrative embodiments of the claimed invention.  
         [0026]      FIG. 1  is a cross-sectional view of a catheter  10  in accordance with an embodiment of the invention. The catheter  10  can be one of a variety of different catheters, but is preferably an intravascular balloon catheter. Except as described herein, the catheter  10  can be manufactured using conventional techniques and materials. The intravascular catheter  10  can be sized in accordance with its intended use. The catheter  10  can have a length that is in the range of about 50 centimeters to about 150 centimeters and can have a diameter that is in the range of about 2 F (French) to about 11 F.  
         [0027]     In the embodiment illustrated in  FIGS. 1-3 , the intravascular catheter  10  is a coaxial multi-lumen catheter. Catheter  10  includes an elongate shaft  12  that has a proximal region  14 , a distal region  16  and a distal end  18 . The elongate shaft  12  includes an outer tubular member  28  and an inner tubular member  30 . The inner tubular member  30  extends from the proximal region  14  of the elongate shaft  12  to the distal end  18  of the elongate shaft  12 . The inner tubular member  30  defines a lumen  32  that extends through the elongate shaft  12 . The outer tubular member  28  extends from the proximal region  14  to the location of the balloon  20 . The balloon  20  has a proximal portion  22  and a distal portion  24 . The proximal portion  22  is bonded to the outer tubular member  28  of the shaft  12  and the distal portion  24  of the balloon  20  is bonded to the inner tubular member  30 . The outer tubular member  28  defines a second lumen  26  for inflating the balloon  20 .  
         [0028]     In some embodiments (not illustrated), the elongate shaft  12  can include one or more shaft segments having varying degrees of flexibility. For example, the elongate shaft  12  can include a proximal segment, an intermediate segment and a distal segment. In some embodiments, the elongate shaft  12  can also include a distal tip segment that can be formed from a softer, more flexible polymer. The elongate shaft  12  can include more than three segments, or the elongate shaft  12  can include fewer than three segments.  
         [0029]     If the elongate shaft  12  has, for example, three segments, such as a proximal segment, an intermediate segment and a distal segment, each segment can include an inner tubular member  30  that is the same for each segment and an outer tubular member that becomes increasingly more flexible with proximity to the distal end  18  of the elongate shaft  12 . For example, the proximal segment can have an outer tubular member that is formed from a polymer having a hardness of 72D (Durometer), the intermediate segment can have an outer tubular member that is formed from a polymer having a hardness of 63D and the distal segment can be formed from a polymer having a hardness of 40D.  
         [0030]     If the elongate shaft  12  has three segments, each of the segments can be sized in accordance with the intended function of the resulting catheter  10 . For example, the proximal segment can have a length of about 35 inches, the intermediate segment can have a length that is in the range of about 2 inches to about 3 inches, and the distal segment can have a length that is in the range of about 1 inch to about 1.25 inches.  
         [0031]     The outer tubular member  28  can be a single layer having a lumen therethrough  26  that is sized to accommodate the outer surface  34  of the inner tubular member  30 . In some embodiments, the outer tubular member  28  can have an outer diameter that is in the range of about 0.065 inches to about 0.13 inches and an inner diameter that is in the range of about 0.050 inches to about 0.12 inches. The outer tubular member  28  can have an overall length that is in the range of about 50 cm to about 150 cm.  
         [0032]     The outer tubular member  28  can be formed of any suitable material such as a polymeric material. Polymers with low durometer or hardness can provide increased flexibility, while polymers with high durometer or hardness can provide increased stiffness. In some embodiments, the outer tubular member  28  can be formed of a material that will provide characteristics useful in providing column support to the elongate shaft  12  when the outer member is deployed thereon.  
         [0033]     In some embodiments, the polymer material used is a thermoplastic polymer material. Some examples of some suitable materials include those discussed previously with respect to the outer tubular member  28  of the elongate shaft  12 . By employing careful selection of materials and processing techniques, thermoplastic, solvent soluble, and thermosetting variants of these materials can be employed to achieve the desired results.  
         [0034]     In some embodiments, the elongate shaft  12  can optionally include a reinforcing braid or ribbon layer to increase particular properties such as kink resistance. The distal part of the inner tubular member  30  can be made of polymers such as polytetrafluoroethylene (PTFE), better known as TEFLON®, or polyether block co-polyamide polymers such as PEBAX®. A reinforcement such as a platinum coil, stainless steel coil, or nitinol braid may also be used. An outer PEBAX® layer can be laminated over the reinforcement for kink resistance and to prevent the lumen  32  collapsing under negative pressure. Alternatively, a reinforcing braid or ribbon layer can be positioned between the outer tubular member  28  and the inner tubular member  30 .  
         [0035]     The inner surface of the outer tubular member  28  can be coated with a lubricious material to reduce friction between the inner surface of the outer tubular member  28  and the outer surface  34  of the inner layer  30 . An exemplary material is TEFLON®.  
         [0036]     In some embodiments (not illustrated), the outer tubular member  28  can be formed having two or more layers. In such embodiments, the outer tubular member  28  can have an inner layer that includes, is coated with, or formed from TEFLON®. The outer layer can be formed of any suitable polymer.  
         [0037]     The inner tubular member  30  can be a uniform material and can define a lumen  32  that can run the entire length of the elongate shaft  12  and that is in fluid communication with a lumen (not illustrated) extending through a hub assembly. The lumen  32  defined by the inner tubular member  30  can provide passage to a variety of different medical devices, and thus, the inner tubular member  30  can include, be formed from or coated with a lubricious material, such as TEFLON®, to reduce friction within the lumen  32 . The inner tubular member  30  can be dimensioned to define a lumen  32  having an appropriate inner diameter to accommodate its intended use. In some embodiments, the inner layer  30  can define a lumen  32  having a diameter of about 0.058 inches and the inner tubular member  30  can have a wall thickness of about 0.001 inches.  
         [0038]     The outer tubular member  28  can be formed from any suitable polymer that will provide the desired strength, flexibility or other desired characteristics. Polymers with low durometer or hardness can provide increased flexibility, while polymers with high durometer or hardness can provide increased stiffness. In some embodiments, the polymer material used is a thermoplastic polymer material. Some examples of some suitable materials include polyurethane, elastomeric polyamides, block polyamide/ethers (such as PEBAX®), silicones, and co-polymers. The outer tubular member  28  can be a single polymer, multiple layers, or a blend of polymers. By employing careful selection of materials and processing techniques, thermoplastic, solvent soluble, and thermosetting variants of these materials can be employed to achieve the desired results.  
         [0039]     In particular embodiments, a thermoplastic polymer such as a co-polyester thermoplastic elastomer such as that available commercially under the ARNITEL® name can be used. The outer layer  28  can have an inner diameter that is slightly larger than the outer diameter of the inner tubular member  30  to define second lumen  26 .  
         [0040]     In some embodiments, the outer tubular member  28  can have an inner diameter in the range of about 0.0600 inches to about 0.0618 inches and an outer diameter in the range of about 0.0675 inches to about 0.0690 inches. Part or all of the outer tubular member  28  can include materials added to increase the radiopacity of the outer layer  28 , such as 50% bismuth subcarbonate.  
         [0041]     The balloon  20  is positioned such that the distal portion  24  is attached to the outer surface  34  of inner tubular member  30  and the proximal portion  22  is attached to the outer tubular member  28  of the shaft  12 . In the illustrated embodiment of  FIG. 1 , the balloon  20  is positioned such that approximately half of the balloon  20  is mounted over the outer layer  28  and approximately half of the balloon is mounted over the inner layer  30 . The second lumen  26  provides means for introducing an inflation fluid into the balloon  20 .  
         [0042]      FIGS. 4-6  illustrate a single lumen design of catheter  100  having an elongate shaft  112  including a common guidewire/inflation lumen  132  extending therethrough. The common lumen  132  accommodates the guidewire  140  and facilitates inflation and deflation of the balloon  120 . A guidewire seal  145  is provided at the distal end  118  of the elongate shaft  112  to provide a fluid seal about the guidewire  140 . With this arrangement, inflation fluid passes from the inflation syringe (not shown), through the common lumen  132  around the guidewire  140  disposed therein, through the inflation ports  150 , and into the interior of the balloon  120  to facilitate inflation and deflation thereof. Markers  138  are disposed on the shaft  112  at the attachment points for the balloon  120 , and at a position midway therebetween.  
         [0043]     The balloon  120  is attached to the shaft  112  of the single lumen catheter  100  near the distal end  118  of the shaft  112 . The distal portion  124  of the balloon  120  is attached to the shaft  112  distally of the inflation ports  150 , and the proximal portion  122  of the balloon  120  is attached to the shaft  112  proximally of the inflation ports  150 . The balloon  120  is positioned on the shaft  112  such that about one half of the balloon  120  overlies the portion of the shaft  112  with the inflation ports  150  and one half overlies the solid shaft  112 .  
         [0044]     The balloon  20  may be made of a highly compliant material that elastically expands upon pressurization. Because the balloon  20  elastically expands from the deflated state to the inflated state, the balloon  20  has an extremely low profile in the deflated state and does not require balloon folding as with other non-compliant or semi-compliant balloon materials. The balloon  20  may be formed of silicone, urethane polymer, or an extruded thermoplastic polyisoprene rubber such as a 40A durometer hydrogenated polyisoprene rubber, which is commercially available under the trade name Chronoprene™ from Carditech International, Inc.  
         [0045]     Hydrogenated polyisoprene provides a balloon  20  having superior performance and manufacturing attributes. In particular, hydrogenated polyisoprene may be processed with standard polyolefin processing equipment to obtain balloon tubing having a wall thickness of approximately 0.001 inches to 0.010 inches and a corresponding inside diameter of approximately 0.016 inches to 0.028 inches. Such tubing has been demonstrated to produce balloons having a nominal outside diameter when inflated of approximately 3.0 mm to 5.5 mm.  
         [0046]     The highly compliant balloon  20  preferably elastically expands at pressures less than 1.0 ATM. The highly compliant balloon  20  may have a pressure compliance of 2.0 mm/ATM or more at pressures less than 2.0 ATM. The highly compliant balloon  20  may have a volumetric compliance of approximately 0.3 mm per 0.01 ml to 0.5 mm per 0.01 ml at pressures less than 2.0 ATM, for balloons having a nominal diameter of approximately 3.5 mm and a length of approximately 10 mm to 15 mm.  
         [0047]     The ends of the balloon  20  are attached to the shaft  12  using conventional bonding means such as thermal bonding using a laser. In one embodiment, the proximal portion  22  of the balloon  20  is releasably attached to the shaft  12  such that when a first amount of inflation fluid is introduced into the collapsed balloon, as shown in  FIG. 1 , the distal portion  24  of the balloon  20  inflates while the proximal portion  22  remains in an uninflated configuration. See  FIG. 2 . If an excess amount of inflation fluid is introduced into the balloon  20 , the proximal portion  22  releases from the shaft  12  and inflates. See  FIG. 3 .  
         [0048]     The releasable bond between the proximal portion  22  of the balloon  20  and the shaft  12  may be achieved by heating the balloon and/or the shaft  12  such that the proximal portion  22  of the balloon is adhered to the shaft  12  but is not permanently bonded. In an alternative embodiment, the proximal portion  22  of the balloon  20  can be releasably attached to the shaft  12  using an adhesive. The adhesive is selected to adhere the proximal portion  22  to the shaft  12  when the distal portion  24  is inflated to the desired diameter or pressure, but to release the proximal portion  22  when the distal portion  24  is over-inflated and the stress on the adhesive bond exceeds a predetermined threshold.  
         [0049]     The degree of attachment is such that when the distal portion  24  of the balloon is inflated to the desired diameter, the proximal portion  22  remains adhered to the shaft  12 , and is released only when the distal portion  24  is over-inflated.  
         [0050]     Once the balloon is inflated to the desired pressure or diameter, inserting additional inflation fluid causes increased pressure and stress at the transition area between the inflated distal portion  24  and the releasably attached proximal portion  22 . This increased stress causes the bond between the proximal portion  22  and the shaft  12  to be released, allowing the additional inflation fluid to inflate the proximal portion  22  of the balloon  20 .  
         [0051]     In one embodiment, the entire proximal portion  22  of the balloon  20  is releasably attached to the shaft  12 . In another embodiment, the proximal portion  22  is releasably attached to the shaft  12  at least at the juncture between the distal portion  24  and proximal portion  22 . In the embodiment illustrated in  FIG. 10 , the releasable attachment  125  is a discrete point of attachment at the juncture between distal and proximal portions of the balloon  120 . Alternatively, the releasable attachment  125  can be an annular band at the juncture between distal and proximal portions of the balloon  120 . In another embodiment, the releasable attachment  125  consists of multiple bands along the proximal portion  122 . The releasable attachment  125  can also be multiple discrete points arranged about the shaft  112 . In this embodiment, once the distal portion  124  of the balloon  120  is inflated, insertion of additional inflation fluid increases the pressure surrounding each discrete attachment point until the attachment points are broken and the proximal portion  124  of the balloon is inflated.  
         [0052]     In another embodiment, illustrated in  FIG. 11 , a sheath  190  is disposed over the proximal portion  122  of the balloon  120 . The sheath  190  can be attached to the shaft  112  proximally of the proximal portion  122  of the balloon  120 . In one embodiment, the sheath  190  is not attached to the shaft  112 . The sheath  190  can be made of an elastomeric material similar to or different from the material from which the balloon  120  is made. In one embodiment, the sheath  190  can be bonded, laminated or otherwise attached to the proximal portion  122  of the balloon  120 . The sheath  190  impedes the inflation of the proximal portion  122  of the balloon  120  such that an increased amount of inflation fluid or increased pressure is necessary for the proximal portion  122  of the balloon  120  to inflate under the sheath  190 .  
         [0053]     In an alternative embodiment, the sheath  190  can be made of a material that can be broken, torn, or ruptured under pressure. The strength of the sheath  190  is such that it remains intact, keeping the proximal portion  122  of the balloon  120  in a deflated configuration until the pressure at the juncture between the distal and proximal portions of the balloon exceeds a predetermined threshold. The sheath  190  then breaks, tears or ruptures, allowing the proximal portion  122  of the balloon  120  to inflate.  
         [0054]     The additional longitudinal balloon area provided by the released proximal portion  22  of the balloon  20  allows for a substantial amount of excess inflation fluid to be held by the balloon  20  without increasing the balloon diameter. This is shown in  FIGS. 2 and 3 , where the diameter D 1  of the balloon  20  with just the distal portion  24  inflated is substantially the same as the diameter D 2  of the balloon  20  with both the distal portion  24  and the proximal portion  22  inflated.  
         [0055]     The amount of over-inflation protection achieved by the balloon can be adjusted by varying the amount of the proximal portion  22  of the balloon  20  that is releasably attached to the shaft  12 . In the embodiment illustrated in the figures, the proximal portion  22  that is releasably attached to the shaft  12  is approximately one half the length of the balloon  20 . A greater amount of protection is provided by releasably attaching a larger percentage of the balloon to the shaft. The length of the balloon and the length of the proximal portion that is releasably attached to the shaft is selected to achieve the desired diameter of the initially inflated distal portion  24  and the amount of over-inflation protection needed for a particular surgical procedure.  
         [0056]     In another embodiment as illustrated in  FIGS. 7-9 , the proximal portion  222  of the balloon  220  has a wall thickness that is greater than a wall thickness of the distal portion  224  of the balloon  220 . The increased thickness in the proximal portion  222  requires a greater pressure to achieve inflation. The distal portion  224  is inflated by injecting a first amount of inflation fluid into the balloon  220 . The amount of pressure necessary to achieve inflation of the distal portion  224  is insufficient to inflate the proximal portion  222 . Once the distal portion  224  of the balloon  220  is inflated to the desired pressure or diameter, injection of additional inflation fluid causes the pressure in the balloon  220  to increase, resulting in inflation of the proximal portion  222 .  
         [0057]     The difference in thickness between the distal portion  224  and proximal portion  222  of the balloon  220  is selected to achieve the desired inflation characteristics. In one embodiment, the distal portion  224  is about half the thickness of the proximal portion  222 . In another embodiment, the distal portion  224  is about one-third the thickness of the proximal portion  222 .  
         [0058]     The balloon  220  can be made using conventional techniques including molding, extruding, stretching, etc., to achieve the desired difference in thickness between the distal  224  and proximal  222  portions. In one embodiment, the distal  224  and proximal  222  portions are about equal in length. In alternative embodiments, the proximal portion  222  is longer than the distal portion  224  to provide a greater safety measure against over-inflation. The proximal portion  222  can also be shorter than the distal portion  224 .  
         [0059]     Radiopaque marker bands  38  may be disposed on the elongate shaft  12  adjacent to the connection between the balloon  20  and the elongate shaft  12  to facilitate radiographic positioning of the balloon  20 . An additional marker band  38  may be disposed midway between the distal and proximal marker bands  38 . The marker bands  38  may be solid or split bands of platinum or other radiopaque metal. Radiopaque materials are understood to be materials capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique during a medical procedure. This relatively bright image aids the user of device in determining its location. Some examples of radiopaque materials can include, but are not limited to, gold, platinum, iridium, palladium, tantalum, tungsten alloy, plastic material loaded with a radiopaque filler, and the like.  
         [0060]     In use, the catheter  10 ,  100  is inserted to the desired location with the balloon  20 ,  120  in a collapsed configuration, as seen in  FIGS. 1 and 4 . An inflation fluid is injected through the second lumen  26  of a multi-lumen catheter  10  or the single lumen  132  in a single lumen catheter  110 . Inflation fluid is injected until the distal portion  24 ,  124  of balloon  20 ,  120  is expanded to the desired diameter D 1  in the first expansion configuration, seen in  FIGS. 2 and 5 . The distal and center markers  38 ,  138  are used as a guide for determining when the distal portion  24 ,  124  of the balloon  20 ,  120  is at the desired inflation configuration.  
         [0061]     If excess inflation fluid is inserted, the proximal portion  22 ,  120  of the balloon  20 ,  120  is released, and the balloon  20 ,  120  is inflated to the second expansion configuration, as shown in  FIGS. 3 and 6 . By comparing  FIGS. 2 and 5  with  FIGS. 3 and 6 , respectively, it is clear that the first diameter D 1  of the balloon  20 ,  120  in the desired first inflation configuration is substantially the same as the diameter D 2  of the balloon  20 ,  120  in the second, over-inflation configuration. This longitudinal expansion provides a safety measure in that it prevents the over-inflated balloon  20 ,  120  from achieving an excessive diameter, resulting in damage or rupture of the vessel.  
         [0062]     The balloon  20  can be sized as appropriate to fit over the elongate shaft  12 , as well as to nearly or completely occlude a particular vasculature in which the balloon  20  will be used. In some embodiments, the balloon  20  can have a length that is in the range of about 0.5 cm to about 2 cm. The balloon  20  can have a first diameter (desired first expansion configuration) that is in the range of about 1 mm to about 1.5 cm. The balloon can have an average thickness that is in the range of about 0.001 inches to about 0.002 inches.  
         [0063]     In some embodiments, part or all of catheter  10  can include a lubricious coating. Lubricious coatings can improve steerability and improve lesion-crossing capability. Examples of suitable lubricious polymers include hydrophilic polymers such as polyarylene oxides, polyvinylpyrolidones, polyvinylalcohols, hydroxy alkyl cellulosics, algins, saccharides, caprolactones, and the like, and mixtures and combinations thereof. Hydrophilic polymers can be blended among themselves or with formulated amounts of water insoluble compounds (including some polymers) to yield coatings with suitable lubricity, bonding and solubility. In some embodiments, a distal portion of the catheter can be coated with a hydrophilic polymer, while the more proximal portions can be coated with a fluoropolymer.  
         [0064]     It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size and arrangement of steps, without exceeding the scope of the invention. The invention&#39;s scope is, of course, defined in the language in which the appended claims are expressed.