Patent Publication Number: US-11660420-B2

Title: Catheters and related devices and methods of manufacture

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 63/290,417, filed Dec. 16, 2021; this application is a continuation-in-part of U.S. patent application Ser. No. 17/508,459 filed Oct. 22, 2021, which is a continuation-in-part of U.S. patent application Ser. No. 16/572,307 filed Sep. 16, 2019 and U.S. patent application Ser. No. 16/572,330 filed Sep. 16, 2019; which claim the benefit of U.S. Provisional Application No. 62/900,645, filed Sep. 15, 2019, U.S. Provisional Application No. 62/899,929, filed Sep. 13, 2019, and U.S. Provisional Application No. 62/732,282, filed Sep. 17, 2018, the entire disclosures of which are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to intraluminal catheters such as intravascular coronary, peripheral and neuro catheters, intrabronchial catheters and other catheters used in small caliber anatomy. 
     BACKGROUND 
     Catheters are used in a wide variety of medical procedures. In some challenging applications, the catheter must navigate a long, narrow and tortuous path to get from the access site to the treatment site. Thus, catheter designs often balance therapeutic or diagnostic function with flexibility, pushability and profile, especially in small caliber anatomy. In such applications, it may be desirable to have as small of a cross-sectional profile as possible, and/or as large of a working lumen as possible. 
     Generally speaking, at least a portion of the catheter is formed by assembling polymeric tubes, often with multiple polymeric layers and metallic reinforcement such as a coil or braid. The polymeric tubes are generally formed by extrusion. The profile of the catheter is substantially influenced by the wall thickness of the tubular extrusion. However, commonly used polymeric extrusions are limited in terms of how thin the wall thickness can be made. 
     In general, with thermoplastic extrusions of any type, the extrusion process is generally governed by the control of polymer volume flow. Tight mechanical control of the extruder lead screw (pump) provides tight control of final dimensions of any extruded part. The miniature nature of medical tubing extrusions presents a polymer volume control challenge. Slight variations in lead screw performance can result in meaningful differences in polymer volume flow and variations in the ultimate dimensions of the extruded part. A tubular wall thickness of 0.0015″+/−0.0005″ is generally accepted as the industry standard lower limit for thermoplastic medical tubing extrusion. At that dimension, tubular extrusion is a low volume process. 
     Thus, it would be desirable to have a wall-thicknesses less than 0.0015″ and tolerances tighter than 0.0005″ (or 33%) to enable different catheter constructions to achieve the lowest profile possible, largest working lumen possible and enable better performing catheters for access to smaller caliber anatomy. 
     SUMMARY 
     In an example embodiment, the present disclosure provides new catheter constructions involving the use of thin film extrusions. Generally speaking, thin (flat) film extrusions may be made substantially thinner than tubular extrusions with tighter manufacturing tolerances. As mentioned above, tubular extrusion is a low volume process. By contrast, thin sheet of film is a higher volume process, so thinner walls may be achieved. In thin film extrusions, the extrusion is thin and wide. As compared to a small tube the polymer volume flow is high and variations in pump performance are less meaningful. The tooling for thin film can be adjusted during the extrusion process vs. hard tooling for tube extrusion. This allows adjustment of the tooling during a run and ensures dimensional requirements are met. The dwell time within the extruder is an important factor. If flow is too low, the polymer degrades. Ultra-thin small tubes do not have enough flow volume. Specifically, thin film extrusion is higher polymer volume flow and less sensitive to extruder pump performance variation as compared to tube extrusion. By way of example, the polymer volume of a thin film extrusion that is 6.0″ wide and 0.0015″ thick is volumetrically equivalent to approximately 27 extruded tubes with an internal diameter of 0.070″ of equivalent wall thickness. This increased extrusion flow volume makes thin film extrusion less sensitive to processing variations (averaging the variations over the entire width) and enables thinner extrusions without creating low flow, a long heat history, and polymer degradation. In addition, the thin film extrusion die is mechanically simple and adjustable enabling titration during an extrusion run to achieve accurate dimensions. 
     Using thin film extrusion, tubes with a wall thickness less than 0.0015″ may be made using the techniques described herein. In addition to thinner walls, tighter dimensional tolerances can be achieved by thin film extrusion because of the aforementioned variables. For example, tubes may be made with thin film extrusion with a wall thickness less than 0.0015″, preferably 0.0010″, 0.0075″, 0.0005″ or even 0.0003″, with corresponding tolerances of ±0.0002″, 0.00013″, 0.0001″, and less than 0.0001″. 
     The example embodiments described herein may be used alone or in combination to achieve the desired result. In each case, the result may be a catheter with a lower profile and/or larger working lumen with better performance. The catheter may comprise a coronary, peripheral and neuro guide catheter, diagnostic catheter, aspiration catheter, microcatheter, balloon catheter, stent delivery catheter or the like. 
     In one example embodiment, a catheter comprises an elongate tubular shaft that includes a thin film polymeric layer with two opposing long edges. The thin film may have a thickness of less than 0.0015″ and a tolerance of less than 0.0005″ (or 33%). Preferably, the thin film thickness may be less than 0.0010″, 0.00075″ or even 0.00050″ depending on the application. The thin film may have a length that is greater than its width to define a thin film elongate ribbon. The width of the ribbon may approximate the circumference of the tubular shaft. The thin film may extend around the longitudinal axis to define a tubular shape with the edges abutting each other to form a joint. The joint may be linear (e.g., straight) or non-linear (e.g., helical) and may be continuous or discontinuous. The tubular-shaped thin film layer may have a uniform wall thickness around the circumference, and the uniform wall thickness may extend across the joint. 
     The elongate shaft may further include a reinforcement layer disposed over an inner liner with the thin film layer disposed over the reinforcement layer. The reinforcement layer may comprise metal such as a braid or coil. 
     The thin film polymeric layer may comprise a first thin film layer and a second thin film layer, wherein the first thin film layer is connected to the second thin film layer end-to-end to define a circumferential joint. The circumferential joint may orthogonal or at an acute angle to the longitudinal axis. The first thin film layer may comprise a material that is different than the material of the second thin film layer. The materials may be different in terms of composition, dimension or other characteristic such as hardness, flexibility color, thickness or radiopacity, for example. One or more layers of thin film may be employed, with each layer comprising the same, similar or different material as described above. 
     In another example embodiment, a method of making catheter or a portion thereof is described. The method may comprise providing a thin film polymeric sheet having a thickness of less than 0.0015″, for example, and two opposing long edges. The thin film may be rolled such that the two opposing long edges form a gap. Heat and force may be applied along the edges such that the gap closes, the edges abut each other, and a longitudinal joint is formed. The heat and force may be removed to result in a thin film tube. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The drawings, along with the detailed description, serve to illustrate various embodiments, concepts and principles of the present disclosure. A brief description of the drawings, which are not necessarily to scale, follows: 
         FIG.  1    is a schematic flow chart of a manufacturing method according to an embodiment of the present disclosure for making a catheter or portion thereof with a thin film sheet; 
         FIGS.  2 A- 2 M  are schematic illustrations of parts, assemblies and subassemblies of the manufacturing method shown in  FIG.  1   ; 
         FIG.  2 N  is an enlarged top view showing an intermediate portion of a device for guiding and supporting catheters such as, for example, stent delivery catheters;  
         FIGS.  3 A- 3 I  are schematic illustrations of parts and manufacturing methods according to another embodiment of the present disclosure for joining thin film sheets end-to-end for use on a catheter or portion thereof; 
         FIGS.  4 A- 4 D  are schematic illustrations of parts and manufacturing methods according to yet another embodiment of the present disclosure for making multi-layered thin film sheets or modified thin film sheets for use on a catheter or portion thereof; 
         FIGS.  5 A- 5 E  are schematic illustrations of guide or diagnostic catheters incorporating a thin film according to an embodiment of the present disclosure; 
         FIGS.  6 A- 6 H  are schematic illustrations of microcatheters incorporating a thin film according to an embodiment of the present disclosure; 
         FIGS.  7 A- 7 B  are schematic illustrations of balloon catheters incorporating a thin film according to an embodiment of the present disclosure; and 
         FIGS.  8 A- 8 B  are schematic illustrations of an aspiration catheter incorporating a thin film according to an embodiment of the present disclosure. 
     
    
    
     While embodiments and aspects of the present disclosure are amenable to various modifications and alternative forms, specifics thereof have been shown and described by way of example, not limitation. 
     DETAILED DESCRIPTION 
       FIG.  1    is a schematic flow chart of an example manufacturing process  100  using thin film to make a portion of a catheter. The manufacturing method  100  is explained in general steps with reference to  FIG.  1   , and variations are described elsewhere herein. The manufacturing process  100  may be applied to a wide variety of catheters, some of which are described herein. In the example shown in  FIG.  1   , the manufacturing process  100  is described with reference to a tri-layer catheter construction, but the thin film technique may be applied to other catheter constructions. When describing the manufacturing method  100 , reference is made to  FIGS.  2 A- 2 M  to show the components being assembled.  
     For a tri-layer construction, a liner and reinforcement subassembly may be manufactured, onto which a thin film may be applied. To make the liner and reinforcement subassembly, a thin-walled tube (inner or liner)  202  may be extruded  102  using conventional tubular extrusion techniques. Alternatively, the liner  202  may be formed from thin film ribbon as described herein. It may be desirable that the liner  202  be lubricious, in which case the liner  202  may be made of PTFE or HDPE, for example. Thin-walled PTFE tubing is available from a variety of vendors including Zeus of Orangeburg, S.C., USA or Junkosha of Tokyo, Japan. For intravascular applications over a 0.014″ diameter guidewire, the wall thickness of the liner may be 0.0015″ with an inside diameter of about 0.016″, for example. The length of the liner  202  may approximate the overall length of the catheter or a portion thereof, ranging from 10 cm to 175 cm, for example. 
     To facilitate construction, the liner  202  may be placed  104  on a mandrel  204  as shown in  FIG.  2 A . Optionally, the mandrel  204  may comprise annealed stainless-steel such that it may be subsequently removed by stretching causing it to become longer and thinner to ease removal. Also optionally, the liner  202  may be stretched  104  on the mandrel  204  to achieve a thinner wall thickness. 
     A reinforcement layer  206  may be fabricated  106  as a separate component and placed  108  on the liner  202  or fabricated  106  directly on the liner  102 . For example, the reinforcement layer  206  may comprise braided stainless-steel wire fabricated by conventional means as a separate component. Alternatively, the reinforcement layer  206  may comprise a coiled stainless-steel wire wound directly on the liner  202 . By way of example, not limitation,  FIG.  2 B  show a coil  206  being wound directly on the liner  202 . The reinforcement layer  206  may be monofilament or multifilament with varying pic count or pitch as desired. 
     The reinforcement layer  202  may be tightened  108  (if not already) and the ends may be secured  110  to avoid unwinding, unraveling or otherwise becoming loose. Securing  110  the ends of the reinforcement layer  206  may be accomplished by additive means such as by using a heat-shrink sleeve or an adhesive. Alternatively, the ends may be secured  110  by a non-additive means such as by welding  210  adjacent filaments or windings of the reinforcement layer  206  as shown in  FIG.  2 C . An example of a suitable welder is a 100 W Ytterbium fiber laser with the following settings: 50-100% (75% nominal) power; 0.1-0.5 ms (0.3 ms nominal) pulse width; 1-10 mm/min (3 mm/min nominal) feed rate; 1-10 Hz (3Hz nominal) frequency; and 0.0025-0.0050″ (0.0045″ nominal) spot size. The laser may be aimed at the seam between adjacent windings such that heat from the laser causes metal to flow between adjacent windings to form a weld joint upon cooling. With the reinforcement layer  206  secured tightly on the liner  202 , the subassembly is complete  112 . 
     An outer thin film layer may be disposed over the subassembly  112  by initially extruding  114  a flat and thin thermoplastic film or sheet  220 . As mentioned previously, it is possible to achieve a thinner wall with a flat film or sheet extrusion than with a tube extrusion for the reasons explained previously. For example, whereas thermoplastic tube extrusions typically reach their lower limit of wall thickness around 0.0015″, thin film extrusions can attain a wall thickness well below 0.0015″, down to 0.0003″, for example. Any wall thickness (T) may be selected for the thin film sheet  220 , but wall thicknesses of less than 0.0015″, and preferably 0.001″ or less may be used to achieve a lower profile. Thin film sheet extrusions are available from multiple vendors such as Peak Nano of Valley View, Ohio, or Polyzen, Inc. of Apex, N.C. Examples of a suitable thin film sheet material include thermoplastic elastomers (TPE) such as polyether block amide (e.g., PEBAX, VESTAMID) or polyamides generally (aka, nylons), polyethylenes (e.g., LDPE, HDPE), etc. 
     As shown in  FIGS.  2 D and  2 E , the thin film sheet  220  may be cut  116  into ribbons  222  wherein the width (W) is substantially greater than the length (L), for example, and wherein the width and length of the ribbons  222  correspond to the outside circumference and length, respectively, of the subassembly  112 . The ribbons  222  may be cut from the sheet  220  by shearing or laser cutting, for example. For laser cutting, the sheet  220  may be placed in a masking fixture with voids defining where the laser may pass to cut the sheet  220 . The laser cuts may be made in two passes, one on each side of the sheet  220  passing partway through to provide a smooth cut free of burrs or flash. The result is a plurality of ribbons  222 , each having a precise wall thickness (T), length (L) and width (W). An example of a suitable laser is a 100 W Ytterbium fiber laser with the following settings: 50-100% (80% nominal) power; and 0.3-1.0 ms (0.55 ms nominal) pulse width. The masking fixture may be made from a laser cut or milled metal plate such as stainless-steel. 
     A ribbon  222  may then be wrapped  118  around the subassembly  112 , wherein the width of the ribbon  222  spans the circumference of the subassembly  112  and the long edges along the length of the ribbon  222  extend along the length of the subassembly  112  to define a longitudinal gap (G) therebetween as shown in  FIG.  2 H . To facilitate wrapping of the ribbon  222  around the subassembly  112 , a fixture may be utilized. For example, the ribbon  222  may be preloaded in a carrier tube  230 , such as a heat-shrink tube as shown in  FIG.  2 F . The ribbon  222  may include a tapered end  224  and hole  226  formed at one end thereof during the cutting process to facilitate pulling (or pushing) the ribbon  222  into the carrier tube  230  using a pulling (or pushing) device  232  releasably connected to the ribbon  222  via hole  226  as shown in  FIG.  2 G . As the ribbon  222  enters the carrier tube  230 , the tapered end  224  engages the circular end of the carrier tube  230  causing the ribbon  222  to roll as shown in  FIG.  2 F . 
     The carrier tube  230 , with the ribbon  222  rolled therein, may be slid onto the subassembly  112  such that the ribbon  222  is essentially wrapped  118  around the subassembly  112 , with a linear gap (G) between the long edges of the ribbon  222 , and an annular space between the inner surface of the ribbon  222  and the outer surface of the subassembly  112  as shown in  FIG.  2 I . The ribbon  222  may be wrapped in a linear fashion (straight or longitudinal) or a nonlinear fashion (e.g., helical or spiral). Optionally, rather than defining a gap, the long edges may abut each other or overlap. 
     The linear gap (G) and the annular space may be closed by the application  120  of heat and inward force, thus forming a joint. Sufficient heat may be applied to cause the ribbon  222  to be at a temperature above the glass transition temperature of the ribbon  222  material. Thermal energy may be applied by convectively (e.g., hot air gun), conductively (e.g., drawing through a heated die or hot jaws) or radiantly (e.g., laser or heat lamp), for example. The inward force may be applied by compression outside the ribbon  222  or vacuum inside the ribbon  222 . In the illustrated example, heat and compression are applied  120  to cause the heat-shrink carrier tube  230  to compress and mold the ribbon  222  onto the subassembly, thus closing the linear gap (G) and the annular space, and creating a bond between the ribbon  222  and subassembly  112  as shown in  FIG.  2 J . When the gap (G) is closed, a longitudinal joint or seam may be formed, although perhaps not visible, wherein the longitudinal edges of the ribbon abut each other and are bonded and the polymeric material flows together to form an outer thin film layer. It may be preferable to have the longitudinal edges abut each other, as opposed to overlapping each other, to minimize profile. If visible, the longitudinal joint or seam may serve to inform the user of the rotational position of the catheter as it is torqued during navigation, for example. 
     The outer thin film layer formed by the ribbon  222  may be cooled  122  and optionally reflowed to further compress the ribbon  222  between filaments of the reinforcement layer  206  into more intimate contact with the liner  202 . Cooling may be performed by ambient air or a cold liquid quench, for example. After cooling, the mandrel  204  may be removed from the completed tri-layer catheter shaft construction  124  as shown in  FIG.  2 K . Thus, a catheter shaft may be configured with a thin film outer layer with a thickness less than 0.0015″, preferably 0.0010″, 0.0075″, 0.0005″ or even 0.0003″, with corresponding tolerances of ±0.0002″, 0.00013″, 0.0001″, and less than 0.0001″, and having a continuous and uniform thin wall around the circumference of catheter shaft. 
     As mentioned above, reflowing may be performed to further compress the outer thin film layer and provide a connection between adjacent outer sections. For example, as shown in  FIG.  2 L , an additional section may be added to the tri-layer shaft assembly and reflowed using heat and compression. In this example, the tri-layer shaft construction may include a liner  202  disposed on a mandrel  204  with a reinforcement layer  206  and a first ribbon  222 A outer layer assembled as described herein. Additionally, a porous substructure  208  comprising, for example, a laser-cut metallic saddle, may be connected to an end of the reinforcement layer  206  and disposed on the liner  202 . A second ribbon  222 B, comprising a different material or the same or similar material with different properties, may be applied as described herein to form a second thin film outer section. A compression roller  240 , such as a stretched elastomeric O-ring, may be rolled over the heat-shrink tube  230  to apply additional compression while heat is applied. This may cause the first thin film outer section of ribbon  222 A to reflow into the second thin film outer section of ribbon  22 B creating a reflow zone of mixed ribbon material  222 C. If, for example, the material of ribbon  222 B is harder than the material of ribbon  222 A, then the reflowed zone of mixed ribbon material  222 C may have a hardness between that of ribbon  222 A and  222 B to provide a smooth transition is flexibility. Thus, using this reflow technique, the following results may be achieved: the outer film layer of ribbon  222 A may be connected to the adjacent outer film layer of ribbon  222 B via a reflow zone of mixed ribbon material  222 C create a smooth transition in terms of the outer diameter and the flexibility between adjacent thin film outer sections; the outer film layer of ribbon  222 A may be (further) disposed between the filaments of the reinforcement layer  206 ; the outer film layer of ribbon  222 B may be (further) disposed in the pores of the substructure  208 ; the outer film layers of both ribbon  222 A and  222 B may be in (more) intimate contact with the liner  202 . 
     Referring to  FIG.  2 M , in some embodiments, the saddle member  152  comprises a saddle interlocking portion  212 , the encapsulation layer  124  comprises a complementary interlocking portion  216 , and the saddle interlocking portion  212  and the complementary interlocking portion  216  engage each other to form a mechanically interlocking connection. In some embodiments, the saddle interlocking portion  212  comprises a plurality of lock features  214  and the complementary interlocking portion  216  of the encapsulation layer  124  comprises a plurality of complementary features  218 . In some embodiments, the complementary features  218  are mechanically interlocked with the lock features  214  at the mechanically interlocking connection. In some embodiments, the lock features  214  of the saddle interlocking portion  212  comprise a plurality of embayments  225  defined by the saddle member  152  and a plurality of peninsular members  223  of the saddle member  152 . In some embodiments, as depicted in  FIG.  2 M , the embayments  225  and the peninsular members  223  are disposed along a distal terminal edge of the saddle member  152  in an ABAB pattern in which each A corresponds to a peninsular member  223  and each B corresponds to an embayment  225 . In some embodiments, each of the embayments  224  is disposed between two peninsular members  223  and each peninsular member  223  is disposed between two embayments  225 . In some embodiments, at least one of the embayments  225  is disposed between two peninsular members  222  and at least one of the peninsular members  223  is disposed between two embayments  225 . In some embodiments, each peninsular member  223  of the saddle interlocking portion  212  comprises a neck portion  266  extending distally beyond an edge of the saddle member  152  and a head portion  268  extending distally from the neck portion  266 . In some embodiments, each neck portion  266  has a neck width, each head portion  268  has a head width, and the head width being greater than the neck width. 
     With reference to  FIG.  2 N , it will be appreciated that the tubular guiding member  105  comprises an inner tubular member  120  and a support structure  166  that is disposed about an outer surface  140  of the inner tubular member  120 . As shown in  FIG.  2 N , in some embodiments, the support structure is a proximal collar portion  170 . The portions of the support structure may be formed by an elongate support member  180 . In  FIG.  2 N , the elongate support member  180  can be seen extending along helical path around the outer surface  140  of the inner tubular member  120 . In some embodiments, the elongate support member  180  forms a plurality of turns. As shown in  FIG.  2 N , the proximal collar portion  170  of the support structure may include a proximal closed loop  176 . In the embodiment of  FIG.  2 N , the proximal closed loop  176  may comprise a proximal weld  188  and a proximal portion  184  of the elongate support member  180  that extends around the outer surface  140  of the inner tubular member  120 . 
     In the example embodiment of  FIG.  2 N , the saddle member  152  is fixed to a distal portion of the shaft member  150  at a weld WZ. In one example embodiment, weld WZ is created using a laser welding process. It should be noted, however, that various joining processes may be used to fix the saddle member  152  to the shaft member  150  without deviating from the spirit and scope of this detailed description. Examples of joining processes that may be suitable in some applications include TIG welding, plasma welding, laser welding, brazing, soldering, and adhesive bonding. With reference to  FIG.  2 N , it will be appreciated that the saddle member  152  includes a weld joint WC. In some example methods, saddle member  152  is positioned over an inner tubular member and clamping force is applied to the saddle member  152  so that the saddle member  152  tightly encircles the inner tubular member. In some example methods, a weld is formed at weld joint WC while the saddle member  152  is tightly encircling the inner tubular member.   
     As an alternative to connecting adjacent outer thin film layers by reflow after the ribbon  222  has been wrapped around the subassembly  112 , different ribbons (in terms of composition or physical properties, such as hardness, for example) may be connected beforehand. Two or more ribbons may be connected by overlap welding or butt welding, for example. Such connection may be made when the thin film is in the form of a sheet (i.e., before the ribbon is cut), or when the thin film is in the form of a ribbon. For purposes of illustration, not limitation, the connection is described with reference to a thin film sheet. 
     Turning to  FIG.  3 A , thin film sheet  300  includes a first thin film sheet section  302  positioned to abut a second thin film sheet section  304  along an edge  306 . An abutting joint may be preferred over an overlapping joint to minimize profile. The first section  302  may comprise a first material and the second section  304  may comprise a second material, where the first material is different from the second material in terms of composition, dimensions or properties. For example, the first section  302  may be formed of a PEBAX and the second section  304  may be formed of VEASTAMID. Alternatively, the first section  302  and the second section  304  may be formed of the same or similar polymers but with different properties such as hardness, radiodensity or color, for example. Or the first section  302  may have a different wall thickness than the second section  304 . These differences may be taken alone or in combination, depending on the desired properties of the catheter. 
     The edge  306  may be configured at a right angle or at an acute angle, such as 45 degrees as shown, for example. An angled edge  306  provides more contact surface area between the first  302  and second  304  thin film sheet sections to enhance bond strength, for example. In addition, when cut into a ribbon and configured into a layer of a catheter shaft, an angled edge  306  may provide a gradual transition between the first  302  and second  304  thin film sections, thus providing a gradual transition in properties such as flexibility, for example. 
     Where the edges of adjacent thin film sections come together, a circumferential joint or seam may be formed, although perhaps not visible, where the material of adjacent sections flows together. When incorporated into a catheter or portion thereof and viewed from the side, the circumferential joint or seam may appear as a circle around the perimeter of the catheter if the edge is configured at a right angle, or an oval around the perimeter of the catheter if the edge is configured at an acute angle. The number and spacing of such joints may be a function of the number and spacing of sections used. When different colored sections are used, the joint may be used to inform the user how far the catheter extends into another catheter, for example. This may be helpful when advancing or retracting the catheter inside another catheter, for example, and may indicate anatomical position of the catheter. 
     As shown in  FIG.  3 B , as well as  FIG.  3 C  which is a cross-sectional view taken along line C-C in  FIG.  3 B , the first  302  and second  304  thin film sheet sections may be held in place by blocks  310  on either side of the sheets  302 ,  403  such that the edges of the thin film sheet sections  302 ,  304  remain in intimate contact. Pressure and heat may then be applied to along the edge  306  to bond the first  302  and second  304  thin film sheet sections together to form a seam at edge  306 . Pressure may be applied by compression via blocks  310 , for example. Sufficient heat may be applied to cause both the edges of the first  302  and second  304  sheet sections to be at a temperature above their respective glass transition temperatures. Thermal energy may be applied by convectively (e.g., hot air gun), conductively (e.g., heated block) or radiantly (e.g., laser or heat lamp), for example. As shown in  FIG.  3 D , the blocks  310  may include windows  312  through which heat (e.g., laser) may be transmitted to the edge  306  while acting as a heat sink for adjacent areas. 
       FIGS.  3 A- 3 D  illustrate a single seam formed along edge  306  between two sheet sections  302  and  304 . The same principles may be applied to any desired number of sheet sections. For example, in  FIGS.  3 E,  3 F and  3 G , an example of a thin film sheet comprising four sections is shown schematically.  FIGS.  3 F and  3 G  are cross sectional views taken along lines F-F and G-G, respectfully, in  FIG.  3 E . Each of thin film sheet sections  32 ,  303 ,  304  and  305  may comprise different materials, properties or dimensions, which allows catheters to be further customized along their length for purposes of flexibility, radiodensity, color, etc. and ultimately for better performance. By way of example, not limitation, sheet section  302  may incorporate radiopaque loading for enhanced visibility under fluoroscopy, sheet section  303  may comprise the same or similar material as sheet section  302  but be free of radiopaque loading, sheet section  304  may comprise the same or similar material as sheet section  303  but with a higher hardness for enhanced pushability, and sheet section  305  may comprise the same or similar material as sheet section  304  but with a greater wall thickness for enhanced rigidity. 
     As mentioned herein, the connections between sections may be made when the thin film is in the form of a sheet (i.e., before the ribbons are cut).  FIG.  3 H  schematically illustrates a top view of a sheet  300  with four sheet sections  302 ,  303 ,  304 , and  305  that may be cut into a plurality of ribbons  320 , each with the same or similar length (L), width (W) and proportions of sections  302 ,  303 ,  304 , and  305  as shown in  FIG.  3 I . To achieve this, the four sheet sections  302 ,  303 ,  304 , and  305  may be connected as described above. Longitudinal cuts may be made through the sheet as described previously to define the width W of each ribbon  320 . Because the edges  306  of adjacent sheet sections are configured at an angle, staggered end cuts may be made for each ribbon  320 , resulting in scrap sections  316 , ribbons  320  of equal length L, and sections  302 ,  303 ,  304 , and  305  of equal length. The ribbons  320  may then be constructed into a catheter or layer thereof as described previously. 
     In addition to providing different sections of thin film along a length of sheet or ribbon as described above, different sections of thin film may be provided across the width or thickness of a thin film sheet or ribbon. For example, different sections of thin film may be provided across the thickness of a thin film sheet or ribbon using multiple layers, which may comprise a coextruded a thin film sheet  400  as schematically shown in  FIG.  4 A , a laminated thin film sheet  420  as schematically shown in  FIG.  4 B , or a composite thin film sheet  440  as schematically shown in  FIG.  4 C . The composite thin film sheet  440  may comprise a lamination of coextruded thin film sheets  400  or laminated thin film sheets  420 . Each thin film layer of the coextruded  400 , laminated  420  or composite  440  multilayer sheet may be selected to have a specific property such as strength, hardness, flexibility, radiopacity, lubricity and/or color, for example. Further, the multilayered sheets  400 ,  420  or  440  may comprise sheet sections connected end-to-end as described previously. The multilayered sheets  400 ,  420  or  440  may be formed into ribbons and incorporated into a catheter or layer thereof as described previously. 
     With reference to  FIG.  4 A , and by way of example, not limitation, a lubricious polymer (e.g., PTFE or HDPE) may be loaded into hopper A, a radiopaque loaded PEBA or VESTAMID may be loaded into hopper B, and a tie material may be loaded into hopper C. The three materials may pass through extruder E to form a co-extruded tri-layer sheet  400  with a lubricious inner layer  402 , a radiopaque outer layer  404  and a tie layer  406 . Tie layer  406 , which may comprise a blend of the inner and outer materials or a material with sticky characteristics, may aid in adhering the interfaces between the inner  402  and outer  404  layers and mitigate delamination when is use. The rheology of the grades of materials for each layer may be closely matched to ease co-extrusion. 
     With reference to  FIG.  4 B , the same or similar layers  402 ,  404  and  406  may form a laminated sheet  420 . The layers of the laminated sheet may be bonded by application of heat and pressure. Pressure may be applied by compression blocks (not shown) disposed on both sides of the sheet  420  surface, for example. Heat may be applied on the entire surface or at discrete locations to define spot welds using a suitable heat source and masking plate, for example. 
     With reference to  FIG.  4 C , the multi-layer sheets  400  or  420  may form a composite sheet  440 . In this example, tri-layer sheets formed by co-extrusion  400  or lamination  420  may be stacked and laminated using the same or similar application of heat and pressure as described above. In addition, the composite sheet  440  may be laminated under vacuum conditions to remove any gas that may be trapped between layers. 
     Each thin film sheet or ribbon may be chemically or physically modified to alter its properties. For example, a thin film sheet or ribbon may incorporate a surface modification (e.g., plasma treatment, roughened) to enhance its adherence to other layers. Alternatively, a thin film sheet or ribbon may have a portion of material removed, wherein the portion removed extends partially or completely through the thickness of the film. For example, a modified thin film sheet  460  may incorporate divots, holes, grooves or slots  462  as schematically shown in  FIG.  4 D . Such features may extend partially or completely through the thickness of the film  404 . The features may be formed in a manner similar to how the ribbon is cut from the thin film sheet as described previously, using a laser and masking template. In the illustrated example, the slots  402  may comprise cuts that extend through the thickness of the thin film  404  in a discontinuous circumferential pattern to impart additional flexibility along its length while retaining structural integrity, for example. 
     Such features may be made in a single thin film layer or a multilayer thin film. In the latter instance, the features may be made in an inner or outer layer, where the middle layer has different properties that make it less susceptible to the material removal process. For example, the material of the middle layer may have a higher melt temperature than the material of the inner or outer layer such that thermal ablation (e.g., laser cutting) forms the feature in the inner and/or outer layer but not the middle layer with an appropriately set ablation temperature. This general approach may be applied to any single layer, any combination of layers or all the layers. The layer or layers having the modification (e.g., cut pattern) may have a higher glass transition temperature than the other layers such that the modified layers retain the modification during assembly onto a catheter shaft by heat and compression. Further, any layer with an exposed surface (inside or outside) may incorporate a lubricious coating (e.g., silicone, hydrophilic polymer). 
     The constructions, features, and manufacturing techniques described herein may be incorporated, in whole or in part, taken alone or in combination, into a variety of catheters such as coronary, peripheral and neuro guide catheters, guide catheter extensions, diagnostic catheters, aspiration catheters, microcatheters, balloon catheters, stent delivery catheters and the like, whether femoral access, radial access or other access, some examples of which are described herein. The table below illustrates how thin film tubes may be implemented in a variety of intravascular catheters, and the percent (%) improvement in wall thickness between conventional (prior art) devices and new (present disclosure) devices. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                   
                   
                 % 
               
               
                 Device 
                   
                 Distal OD 
                 ID 
                 Wall 
                 Thinner 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Diagnostic 
                 Conventional 
                 5 F 
                 0.045-.047″  
                 0.009″ 
                   
               
               
                 Catheter 
                 New 
                 5 F 
                 0.060″ 
                 0.003″ 
                 67% 
               
               
                 Guide 
                 Conventional 
                 6 F 
                 0.070-0.071″ 
                 0.0045″ 
                   
               
               
                 Catheter 
                 New 
                 6 F 
                 0.075″ 
                 0.003″ 
                 33% 
               
               
                 Guide 
                 Conventional 
                 6 F 
                 0.056-0.057″ 
                 0.005″ 
                   
               
               
                 Catheter Ext. 
                 New 
                 6 F 
                 0.061″ 
                 0.003″ 
                 40% 
               
               
                 Micro- 
                 Conventional 
                 1.8 F   
                  0.0155″ 
                 0.004″ 
                   
               
               
                 Catheter 
                 New 
                 1.4 F   
                  0.0155″ 
                 0.0022″ 
                 45% 
               
               
                 Balloon 
                 Conventional 
                 2.5 F    
                   
                 0.005″ 
                   
               
               
                   
                   
                 (0.033″) 
                   
                   
                   
               
               
                 Catheter 
                 New 
                 1.9 F    
                   
                 0.003″ 
                 40% 
               
               
                   
                   
                 (0.025″) 
                   
                   
                   
               
               
                 Aspiration 
                 Conventional 
                 6 F 
                 0.068″ 
                 0.006″ 
                   
               
               
                 Catheter 
                 New 
                 6 F 
                 0.074″ 
                 0.003″ 
                 50% 
               
               
                   
               
            
           
         
       
     
     For example, as shown in  FIG.  5 A , a guide or diagnostic catheter  500  may incorporate the constructions described herein. Catheter  500  may include a proximal portion  502  with a hub and a distal portion  504  with an optional pre-set curve configured for the particular anatomy being accessed. Catheter  500  may include a tubular shaft  510  with a lumen  508  extending therethrough from the proximal portion  502  to the distal portion  504  ending in a distal facing opening  506 . 
     As best seen in  FIG.  5 B , which is a partially sectioned detail view of the boxed portion shown in  FIG.  5 A , the catheter shaft  510  may comprise an inner liner  524  such as thin-walled PTFE over which a reinforcement layer  526  such as braid may be disposed. The outer layer may comprise a series of thin film sections  512 ,  514 ,  516  and  518  of the same or similar material with decreasing hardness from proximal to distal. The outer layer may be constructed as described herein to form a longitudinal joint or seam  520 , as well as circumferential joints or seams between each of the thin film sections  512 ,  514 ,  516  and  518 . 
     For example, with reference to  FIG.  5 C , a thin film ribbon  530  may be formed from a sheet comprising a series of thin film sections  512 ,  514 ,  516  and  518 . The ribbon  530  may be rolled to define a gap G as shown in  FIG.  5 D , as well as  FIG.  5 E  which is a partially sectioned detail view of the boxed portion shown in  FIG.  5 D . The ribbon  530  may be placed in a carrier  230  comprising, for example, a heat shrink tube, and loaded onto a subassembly comprising liner  524  and reinforcement layer  526 . Applying heat and compression conforms the ribbon  530  around the subassembly, closes the gap G, and forms a longitudinal joint  520  along the longitudinal edges of the ribbon  530 . 
     By using a thin film outer layer with a thickness less than 0.0015″, preferably 0.0010″ 0.0075″, 0.0005″ or 0.0003″, for example, the density (e.g., picks per inch or PPI) of the reinforcement layer (e.g., braid)  526  may be increased and the inside diameter of the through lumen  508  may be increased to improve performance without compromising the profile of the catheter  500 . For example, a conventional 6F catheter may have an outside diameter of 2 mm or 0.0786″, an extruded inner liner wall thickness of 0.0015″, a braid thickness of 0.005″ (0.00075″ thick wire braided at 60 PPI) and an extruded outer covering having a wall thickness of 0.0038″, resulting in an inside diameter of 0.071″. By contrast, by using a thin film for the outer covering having a wall thickness of 0.00075″ to 0.001″, for example, the braid density may be increased to 120-180 PPI using the same wire and inner liner, resulting in a larger inside diameter of 0.074″. The thin film outer covering generally allows the precise application of ultra-thin conformal coatings such that additional reinforcement support structure can be added and the inside diameter may be enlarged to improve performance without increasing the size (outside diameter) of the catheter  500 . 
     With reference to  FIG.  6 A , a microcatheter  600  may incorporate the constructions described herein. Microcatheter  600  may include a proximal portion  602  with a hub and a distal portion  604  that may optionally be tapered as shown, for example. Microcatheter  600  may include a tubular shaft  610  with a lumen  608  extending therethrough from the proximal portion  602  to the distal portion  604  ending in a distal facing opening  606 . 
     As best seen in  FIG.  6 B , which is a partially sectioned detail view of the boxed portion shown in  FIG.  6 A , the catheter shaft  610  may comprise an inner liner  624  such as thin-walled PTFE over which a reinforcement layer  626  such as a coil may be disposed. The outer layer may comprise a series of thin film sections  612 ,  614  and  616  of the same or similar material with decreasing hardness from proximal to distal. As seen in  FIG.  6 C , which illustrates a partial section of the catheter shaft  610  wall, the thin film outer layer allows the use of additional reinforcement material  626 , such as two layers of counter-wound coil, without increasing the profile of the microcatheter  600 . The outer layer may be constructed as described herein to form a longitudinal joint or seam  620 , as well as circumferential joints or seams between each of the thin film sections  612 ,  614  and  616 . 
     Whereas the microcatheter  600  uses a single lumen  608  that may accommodate a guidewire or be used for delivering fluids and devices, microcatheter  640 , shown schematically in  FIG.  6 D , uses two lumens  607  and  608 . In this example, a dual lumen extrusion  628  may replace the inner liner  624  described with reference to  FIG.  6 A . The catheter shaft  610  may include a proximal port  634  that provides access to lumen  608  wherein a guidewire may extend proximally out of port  634 , distally through lumen  608 , and distally out of the distal facing opening  606 . This dual lumen and side port configuration may be referred to as monorail, rapid exchange, etc., and may be used for exchanging the catheter  640  over a conventional length guidewire. The catheter shaft  610  may also incorporate a distal port  632  in fluid communication with lumen  607  and the hub on proximal portion  602 . This configuration allows liquids and devices to be delivered without removal of a guidewire disposed in lumen  608 . 
     For both microcatheter  600  and  640 , and with reference to  FIG.  6 F , a thin film ribbon  630  may be formed from a sheet comprising a series of thin film sections  612 ,  614 , and  616 . The ribbon  630  may be rolled to define a gap G as shown in  FIG.  6 G , as well as  FIG.  6 H  which is a partially sectioned detail view of the boxed portion shown in  FIG.  6 G . The ribbon  630  may be placed in a carrier  230  comprising, for example, a heat shrink tube, and loaded onto a subassembly comprising liner  624  and reinforcement layer  626 , or comprising dual lumen extrusion  628  and reinforcement layer  626 . Applying heat and compression conforms the ribbon  630  around the subassembly, closes the gap G, and forms a longitudinal joint  620  along the longitudinal edges of the ribbon  630 . 
     A distal portion of the reinforcement layer  626  may comprise a more radiopaque material than a proximal portion of the reinforcement layer to facilitate fluoroscopic navigation. For example, a radiopaque coil comprising a rectangular ribbon (e.g., 0.005″×0.0015″) with a tantalum core (approximately 40% by cross sectional area) and a jacket of spring temper MP35N or stainless-steel may be used. In this example, the jacket material may have an X-ray attenuation coefficient less than 50 l/cm and the core material may have an X-ray attenuation coefficient greater than the 50 l/cm. The tantalum core provides radiopacity and the MP35N or stainless-steel jacket provides structural integrity and is weldable. The coil may have a variable pitch wind such that a low pitch (e.g., no gap) portion provides more radiodensity and a higher pitch portion provides more flexibility. 
     With reference to  FIG.  7 A , a balloon angioplasty catheter  700  may incorporate the constructions described herein. The balloon angioplasty catheter  700  may be used for plain old balloon angioplasty (POBA) or for stent delivery, for example. The balloon catheter  700  may comprise a fixed-wire, over-the-wire, or rapid exchange construction as shown. The balloon catheter  600  may include a proximal portion  702  with a hub or manifold and a distal portion  704  that may optionally be tapered as shown, for example. The balloon catheter  700  may include a tubular shaft  710  comprising an inner  712  and an outer  714 . A balloon  706  may be connected to the shaft  710  with a proximal waist  718  connected to the outer and a distal waist  716  connected to the inner  712 . The inner  712  may define a guidewire lumen  724  and an inflation lumen  722  may be defined in the annular space between the inner  712  and outer  714  for inflation and deflation of the balloon  706 . The inner  712  may include a lubricious liner  726  (e.g., PTFE or HDPE) and a jacket  728  (e.g., PEBAX or VESTAMID). A radiopaque marker band  708 A may be disposed between the liner  726  and a jacket  728 . Alternatively, a support structure  708 B (e.g., a coil of flat metal ribbon which may be radiopaque) may be disposed between the liner  726  and a jacket  728  as shown on balloon catheter  740  illustrated in  FIG.  7 B . 
     Both the liner (inner) layer  726  and the jacket (outer) layer  728  of the inner tube  712  may comprise a thin film ribbon that is wrapped, heated and compressed to form joint or seam  720  as described herein. By using thin film ribbon, the inner  712  may have an ultra-thin wall, enabling a smaller distal balloon waist  716  for the same size guidewire lumen  724 . This reduces the crossing profile of the balloon catheter  700 / 740  enabling it to cross tight vascular restrictions such as those encountered in chronic total occlusions (CTOs) and generally in very small caliber anatomy. 
     With reference to  FIG.  8 A , an aspiration catheter  800  may incorporate the constructions described herein. Aspiration catheter  800  may include an elongate tubular shaft  802  defining an aspiration lumen therein for removal of vascular thrombus, fibrin clot or the like. The aspiration lumen may extend from a hub  804  connected to the proximal end of the shaft  802  (for connection to a pump) to a distal opening  806  at the distal end of the shaft  802 . In this example, a thin film layer  812  may be used as an inner liner, which may comprise a lubricious thermoplastic such as HDPE. The thin film layer  812  may be disposed over coils  808  and  814 , with the thin film layer  812  extending to the inner lumen between turns of the coils  808  and  814 , as shown. Alternatively, the thin film layer  812  may be disposed under coils  808  and  814 . In the former instance, the thin film layer  812  may be applied over the coils  808  and  814  using heat and inward pressure as described previously. In the latter instance, the thin film layer  812  may be applied under the coils  808  and  814  using heat and outward pressure. Outer layer  810  comprising, for example, PEBAX or VESTAMID, may be disposed over the thin film layer  812  as shown, or if the thin film layer  812  is disposed under the coils  808  and  814 , the outer layer may be disposed over the coils  808  and  814 . A reflow process, for example, as described herein, may be used to cause the outer layer  810  to extend into the space between turns of the coils  808  and  814 . A thin film tie layer (not shown) may be used to enhance the connection between the lubricious inner layer  812  and the outer layer  810 . 
     As shown in  FIG.  8 A , as well as  FIG.  8 B , which is a detailed section view of the box shown in  FIG.  8 A , the shaft  802  may incorporate tow coil sections, namely distal coil  808  and more proximal coil  814 . The two coils  808  and  814  may comprise different materials, different dimensions, and different winding parameters. For example, the distal coil  808  may be more radiopaque than the more proximal coil  814 . In this example, the distal coil  808  may comprise a rectangular ribbon (e.g., 0.005″×0.0015″) with a tantalum core  809  (approximately 40% by cross sectional area) and a jacket  809  of spring temper MP35N or stainless-steel, and the more proximal coil  814  may comprise a stainless-steel ribbon, both available from Fort Wayne, Ind. In addition, the distal coil  808  may have greater spacing between turns than the more proximal coil  814 , such that the distal portion of the catheter shaft  802  is more flexible. Laser spot welds, as described previously, may be used to connect the coils  808  and  814  and secure the ends thereof. In addition, the coils  808  and  814  may be coated with a polymer  816  such as polyamide or parylene by vapor deposition to enhance the connection between the coils  808  and  814  to the thin film layer  812 . Collectively, these features may provide a thin-walled aspiration catheter  800  with a larger aspiration lumen without increasing the outside profile of the catheter  800 . 
     The constructions, features, and manufacturing techniques described herein may be incorporated, in whole or in part, taken alone or in combination, into a variety of catheters such as the guide, diagnostic, micro, balloon and aspiration catheters, as described herein by way of example, not limitation. The same may be applied to other vascular catheters such as oncology catheters as well as non-vascular catheters such as bronchial catheters.