Abstract:
A deflectable sheath with increased range of curvature for human use is provided. The improvement focuses on the use of different durometer polymers that compose the lumen in the portion of deflection. The use of differing durometer polymers allow the deflectable sheath to be bent in a multitude of asymmetric curvature radii therefore providing the physician with a sheath that can traverse different regions of the body than with previous sheaths.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from U.S. provisional Application Ser. No. 61/061,814, filed Jun. 16, 2008. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The present invention generally relates to medical devices such as deflectable sheaths. More particularly, the present invention relates to a steerable sheath catheter for positioning in a desired orientation and location in the human body. 
       SUMMARY OF THE INVENTION 
       [0003]    Many current deflectable sheaths are designed to deflect in different directions to reach locations within the human body. These sheaths are composed of overlapping monolithic polymer layers that form continuous lumen(s). A wire mesh is typically placed between the monolithic polymer layers to provide added rigidity. Pull wire(s) are typically incorporated along the length of the sheath to provide a means of deflection. 
         [0004]    Current sheaths however, have a limited deflection radius. When these sheaths are bent, the radius of curvature at the point of deflection is constant and symmetric about a deflection point. The sheath&#39;s arc of deflection is constant which therefore results in limited freedom of motion. This limitation substantially hinders the accessibility of the catheter to gain access to the desired location within the human body. Therefore, what is needed is a deflectable sheath that overcomes the shortcomings of previous designs by allowing the radius of curvature at the point of deflection to change, i.e. allow for asymmetric curvature about a point of deflection. This would allow the physician to gain access more easily in the human body particularly in the diseased vasculature which has been constricted with blockages. 
         [0005]    The present invention is an improved deflectable sheath catheter that is capable of deflecting over a wider range of curvatures, i.e. is capable of deflecting over an asymmetric or non symmetrical range of curvatures. The improvement is directed to the use of a combination of materials with multiple durometers or hardness&#39;s that reside within the outer lumen of the sheath. 
         [0006]    In manufacturing the catheter, a step or void is created in the region of intended deflection in the outer lumen layer. The step is then filled with a polymer(s) consisting of differing durometer(s). This creates a matrix of differing durometer polymers. Single or multiple steps can be made in the distal region of the outer lumen. These steps are also filled with a polymer(s) of differing durometer(s) to create a matrix of materials. 
         [0007]    Conventional sheath catheters do not have a step region that incorporates a combination of differing durometer materials. Instead, they are composed of lumen layers with each lumen layer composed of a monolithic polymer with a single and continuous durometer from one end to the other. The integration of a step region of differing durometer materials within an individual lumen enables the sheath catheter to deflect over a much wider range of curvatures than that provided by conventional deflectable sheaths. This asymmetric deflection functionality results in a sheath that is capable of a wider range of motion than previous deflectable sheaths. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of a bi-directional steerable sheath assembly according to the present invention. 
           [0009]      FIG. 2  depicts the preferred composition of the different polymer regions with different durometers in the outer layer lumen of the distal portion. 
           [0010]      FIGS. 3A to 3C  depict the various annular extensions of the different polymer regions that comprise the distal portion of the outer lumen as they wrap around the sheath and adjoin at the step interface. 
           [0011]      FIG. 4  depicts an alternate composition of the different polymer regions with different durometers in the outer layer lumen of the distal portion. 
           [0012]      FIG. 5  depicts an alternate composition of the different polymer regions with different durometers in the outer layer lumen of the distal portion. 
           [0013]      FIG. 6  depicts examples of the different radius of curvatures capable of the sheath at the distal region. 
           [0014]      FIG. 7  is a perspective view showing the addition of a ring  72  on the inner lumen. 
           [0015]      FIG. 8  is a perspective view that shows the placement of the pull wires  80  and  82  along the inner lumen. 
           [0016]      FIG. 9  is a perspective view that shows the method of attachment of the pull wires  80 ,  82  to the outer ring  72 . 
           [0017]      FIG. 10  is a perspective view that shows the placement of the wire mesh  140  over the sheath assembly of the inner lumen  70  and attached pull wires  80 ,  82 . 
           [0018]      FIG. 11  is a perspective view that shows the wire mesh  140  placed over the pull wires  80 ,  82  and inner lumen  70 . 
           [0019]      FIG. 12  is a perspective view that shows the placement of the second outer lumen  160  over the inner lumen, wire mesh and pull wire assembly depicted in  FIG. 13 . 
           [0020]      FIG. 13  is a perspective view of the placement of the shrink wrap layer  170  over the sheath assembly comprising the wire mesh, pull wires, and inner and outer polymer lumens. 
           [0021]      FIG. 14  is a perspective view of the entire sheath assembly comprising the inner and outer lumens, wire mesh, pull wires and shrink wrap. 
           [0022]      FIG. 15  is a depiction of the sheath assembly being heat treated in a furnace  190 . 
           [0023]      FIG. 16  is a perspective view showing an exemplary deflectable sheath of the present invention having different durometer polymer regions that comprise the distal portion of the outer lumen. 
           [0024]      FIG. 17  is an exploded cross-sectional view along line  17 - 17  of  FIG. 16 . 
           [0025]      FIG. 18  is an exploded cross-sectional view along line  18 - 18  of  FIG. 16 . 
           [0026]      FIG. 19  is an exploded cross sectional view along line  19 - 19  of  FIG. 16 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    As used herein, the term “durometer” relates to the hardness of a material defined as a material&#39;s resistance to permanent indentation. In the hardness measurement of polymers, elastomers and rubbers according to the present invention, durometer is measured according to ASTM D2240 type A scale. 
         [0028]    As used herein, a “step” is a transition from a first polymeric material to a second polymeric material where the first and second materials do not meet each other at an annular transition that forms a plane aligned generally perpendicular to a longitudinal axis of the sheath. An example is where the first polymeric material can range from 45° to 315° of the annular extent of the sheath member with the second polymeric material being the remainder of the annular extent along a cross-section aligned perpendicular to a longitudinal axis of the sheath. Multiple polymeric materials can be adjoined together around the catheter so as long as they together form a complete 360° annular extent around the sheath. 
         [0029]    The present invention is a deflectable sheath  10  which is comprised of an elongated tubular structure that is flexible yet substantially non-compressible along its length. The deflectable sheath  10  extends from a deflectable distal portion  16  having a distal end  18 , which is adapted to be disposed within a patient to a proximal portion  14 . The sheath  10  is comprised of an outer tubular lumen member  160  formed of a polymeric material, such as of PEBAX. An inner tubular member  70  composed of a polymeric material, such as PTFE forms the inner lumen of the sheath. The PTFE inner lumen provides the sheath  10  with sufficient lubricity so that medical instruments, devices, and the like, slide through the sheath  10  with a minimal amount of force. A wire mesh  140  and pull wires  80  and  82  both formed of stainless steel, reside between the two lumen layers  70  and  160 . A handle assembly  12 , in turn, provides for selective deflection of a distal portion  16  of the sheath  10  into anyone of a number of disparate orientations, as will be further described in detail herein below. However, it is the incorporation of multiple durometer polymeric materials in the distal portion  16  of the outer lumen  160  that creates the extended asymmetric deflection of the sheath catheter as described in more detail below. 
         [0030]      FIG. 1  illustrates a bi-directional asymmetric sheath assembly  10  according to the present invention. The deflectable sheath  10  has a length extending from a proximal portion  14  supported by the handle assembly  12  to a distal portion  16  and distal end  18 . The distal portion  16 , a section within the outer lumen  160 , in turn is composed of at least two distal regions that are contiguous with each other at a step. 
         [0031]    For example,  FIG. 2  illustrates the distal portion  16  of the sheath  10  comprising a first distal region  20  composed of a polymeric material of a different durometer than the proximal portion  14 . Preferably the first distal region  20  is composed of PEBAX of a 65 durometer that extends annularly about 360° around the sheath. The first distal region  20  meets a second distal region  22  composed of a polymeric material of a different durometer than the first region  20 , such as 55 durometer PEBAX. The first distal region  20  meets the second distal region  22  and third distal region  24  at an annular transition  28  that forms a plane aligned generally perpendicular to a longitudinal axis of the sheath. The second distal region  22  extends annularly about 180° around the sheath and meets a third distal region  24  at a step  26 . The third distal region  24  is composed of yet another polymeric material of a different durometer than the first and second distal regions  20  and  22 , such as 35 durometer PEBAX. The third distal region  24  has a proximal portion  24 A that extends annularly about 180° around the sheath and a distal portion  24 B that extends to the end  18  of the distal portion  16  of the sheath  10 . 
         [0032]    In the exemplary construction shown in  FIG. 2 , materials with three different and distinct durometers compose the outer layer lumen of the sheath  10 . However a combination of as few as two or a multitude of three or more distinct distal regions of a multitude of geometric shapes could also be used as long as the adjacent distal regions are composed of adjoining polymeric materials of differing durometers. Preferably the durometer of the polymeric material from one region differs by at least 10 durometers from the adjacent region. In that respect, for the sake of clarity the various regions of different durometers in a contiguous relationship with each other will be designated “first distal region”, “second distal region”, “third distal region”, etc. as they extend from a most proximal distal region to the end of the distal portion  16  of the sheath  10 . 
         [0033]    More particularly with respect to  FIG. 2 , the deflectable sheath  10  of the present invention comprises the distal portion  16  extending for a length of about two inches to as much as about thirty-five inches with a diameter between about 0.1 inches to about 3 inches. The distal portion  16  is comprised of the first distal region  20  having a cylindrical shape that meets a second distal region  22  at an annular transition  28 . If desired, the first distal region  20  is the proximal portion  14  supported by handle  12 . In that case, there is no “middle sheath portion”. In any event, the second distal region  22  meets the third distal region  24  at a step  26 . Step  26  as depicted in  FIG. 2  shows a 90° transition of the second distal region  22  to the third distal region  24  where it adjoins together and assumes a completely cylindrical shape extending to a distal end  18  of the distal sheath portion  16 . Although depicted as a 90° angle as shown in step  26 , the step transition can assume a multitude of different angles such as 45° and 180° or be of a curved transition boundary. 
         [0034]    In that respect, the polymeric materials can have a wide range of annular extents, as long as they combine to have an annular extent of 360°. For example, the cross-section designated by line  3 A- 3 A of  FIG. 2  shows an embodiment where polymeric material  22  extends about 45° around the annular extent of the sheath while polymeric material  24  is the remainder of about 315°. In  FIG. 2 , cross-sectional line  3 B- 3 B shows an embodiment where both materials  22  and  24  extend about 180° around the annular extent of the sheath. In  FIG. 2 , cross-sectional line  3 C- 3 C shows an embodiment where polymeric material  22  extends about 315° around the annular extent of the sheath while polymeric material  24  is the remainder of about 45°. In each case, delineation between the respective materials  22  and  24  is designated by the abrupt transition line  21 . 
         [0035]    As further shown in  FIG. 4 , an alternate embodiment of the present deflectable sheath invention comprises a first distal region  30  of a durometer polymeric material having a cylindrical shape extending 360°. The first distal region  30  extends to and meets with a second distal region  32  of a polymeric material. The first distal region  30  can be composed of a PEBAX polymer of a durometer ranging from about 80 to about 65. The first distal region  30  meets the second distal region  32  at an annular transition at an annular transition that forms a plane aligned generally perpendicular to a longitudinal axis of the sheath  31 . The second distal region  32  is comprised of a proximal portion  32 A having a cylindrical shape extending 360° to a distal portion  32 B extending somewhat less than that, for example 180°. 
         [0036]    The second distal region  32  and a third distal region  34  are each of different durometer polymeric materials than that of the first distal region  30 . The proximal portion  32 A of the second distal region  32  extends to a step  33  where it meets the third distal region  34  having a cylindrical shape extending 180 about the periphery of the sheath. 
         [0037]    The distal portion  32 B of the second region  32  and the third distal region  34  in turn meet a fourth distal region  36  at a transition  37 . The forth distal region  36  extends about 180° around the periphery of the sheath as a complementary portion to the distal portion  32 B of the second region  32  and the third distal region  34 . 
         [0038]    The third distal region  34  in turn meets the proximal portion  38 A of a fifth distal region  38  at a step  39 . In turn, the distal portion  38 B of the fifth distal region  38  meets the fourth distal region  36  at a step  41 . Both distal regions  36  and  38  are of a different durometer. The proximal portion  38 A of the fifth distal region  38  extends annularly about 180° around the sheath until it transitions into the distal portion  38 B which has a cylindrical shape extending 360° to the distal end thereof. The fourth distal region  36  can be of a polymeric material having a durometer that is the same or different than that of the first and second distal regions  30  and  32 . The fifth distal portion  38  meets a sixth distal region  40  at an annular transition that forms a plane aligned generally perpendicular to a longitudinal axis of the sheath, which in turn extends to the end  18  of the sheath  10 . 
         [0039]    In another embodiment, the second distal region  32  can be composed of a polymeric material such as PEBAX with a durometer ranging from about 75 to about 60. The third distal region  34  can be composed of a polymeric material such as PEBAX with a durometer ranging from about 70 to about 55. The fourth distal region  36  can be composed of a polymeric material such as PEBAX with a durometer ranging from about 65 to about 45, the fifth distal region  38  can be composed of a polymeric material such as PEBAX with a durometer ranging from about 55 to about 35 and the sixth distal region  40  having a durometer of from about 60 to about 50. The first distal region and the third or fourth distal regions  30 ,  34  or  36  can be of the same durometer material as long as adjoining distal regions are not of the same durometer. 
         [0040]    Preferably, the durometer parameter decreases as the various polymeric materials extend to the distal end  18  of the sheath. However, that is not an absolute. In some designs, it may be desired to have a first polymeric material of a first durometer meeting a second polymeric material of a second durometer that in turn meets a third polymeric material of a third durometer. The third durometer can be less than both the first and second polymers or it can be less than one of them, but greater than the other. 
         [0041]      FIG. 5  shows another alternate embodiment of the deflectable sheath invention. This alternate embodiment comprises a first distal region  50  which extends annularly about 360° about the sheath and meets the first portion  52 A of the second distal region  52 . Distal region  52  consists of a polymeric material of a different durometer than distal region  50  and extends annular about 180° about the sheath. Distal portion  52 A extends to distal portion  52 B of distal region  52 . The distal portion  52 A meets distal portion  54 A, a distal portion of the third distal region  54 , at step  53 . Distal portion  52 B meets distal portion  54 B, an extension of distal portion  54 A at step  55 . A fourth distal region  56  which extends annularly about 360° about the sheath, meets distal portion  54 B at an annular transition  57 . Distal region  56  extends to the end of the sheath  18 . Durometers of the polymeric material within the different distal regions can range from about 75 to about 25 with each adjacent distal region having a different durometer. 
         [0042]      FIG. 8  shows the resulting extended asymmetrical deflection range of motion. With the added distal regions that are adjoined at annular transitions and interface steps of differing durometer polymeric materials, resulting in the asymmetric curvature of the distal portion  16  to 315° and more or as little as 45°. The deflectable sheath can bend at different or asymmetric angles about the deflection point; the larger angle of 315° is shown by numerical designation  172  while the smaller curvature of as little as 45° is shown by numerical designation  174 . 
         [0043]    As illustrated in  FIG. 7 , the manufacturing process of the deflectable sheath begins with an inner lumen  70  which consists of a monolithic PTFE material of a constant durometer. The lumen  70  is sized and shaped to receive, for example, instruments, fluids, media and the like. The length of this lumen is about twelve inches to about seventy inches long with a diameter of about 0.10 inches to about 1 inch. 
         [0044]    A support ring  72  as shown in  FIG. 7  is placed over the distal end of the inner PTFE lumen  70  and forms a tight fit. The distal support ring  72  is preferably made of stainless steel. The ring  72  can also be made of a different rigid material including but is not limited to, a rigid polymeric material, ceramic, titanium, copper, gold, silver, platinum, palladium, NITINOL®, or other metal alloy. The purpose of the support ring  72  is to provide stability to the distal end as well as provide a support for attachment of the pull wire  80 ,  82 . 
         [0045]    Next pull wires  80  and  82  depicted in  FIG. 8  are placed at opposing sides of the inner lumen. For maximum deflection the push/pull wires should be placed 90° from the complementary distal region. In other words, to provide maximum deflection, the opposing pull wires need to placed so that each of them lays across different durometer distal regions. Preferably the pull wires should be placed opposing each other and 90° from the transition steps of the previously described distal regions of varying durometers to create maximum deflection. These pull wires provide mechanical support to the sheath as well as a means for the operator to push and pull and consequently bend the catheter&#39;s distal region. The pull wires  80  and  82  extend from the support ring  72  at the distal end to the handle  12  where they connect to mechanisms for providing tension and compression to consequently deflect the distal portion  16  of the sheath  10  in one direction or another as previously described with respect to  FIG. 6 . Such push/pull mechanisms are well known by those skilled in the art and do not necessarily form a differentiating aspect of the present invention. The push/pull wires  80  and  82  are made of stainless steel material. However other materials including but not limited to copper, titanium, gold, silver, platinum, palladium, NITINOL®, or flexible polymers and textile materials such as VECTRAN® or Spectra can also be used. 
         [0046]    Push/pull wires  80  and  82 , are then affixed to the distal support ring  72  by means of welding  90  such as laser or resistance welding  90  as depicted in  FIG. 9 . Alternate means of fixation include, but not limited to, chemical bonding, brazing, and soldering. The resulting attachment bond created either through welding, brazing, soldering or other means is depicted as  92 . 
         [0047]    Following attachment of the pull wires  80 ,  82  as shown in  FIG. 9 , a stainless steel wire mesh  140  is placed over the assembly as shown in  FIG. 10 . The wire mesh  140  is pulled over the inner lumen/pull wire assembly and forms a tight fit over the inner PTFE lumen  70  and opposing pull wires  80  and  82  as shown in  FIG. 11 . The steel wire mesh  140  provides additional mechanical support to the sheath. The addition of the wire mesh  140  is also known to those skilled in the art and the addition of the wire mesh does not form a differentiating aspect of the present invention. Preferably the wire mesh is composed of stainless steel. Alternate wire braid mesh materials may include NITINOL®′ titanium, copper, nickel, gold, silver, palladium, platinum, ceramic or rigid polymer. 
         [0048]    Following the addition of the stainless steel wire mesh  140  as shown in  FIG. 11 , a second polymeric lumen of PEBAX is placed over the sheath assembly as shown in  FIG. 12 . The lumen is composed of a high durometer polymeric material, preferably of PEBAX, having a durometer from about 50 to about 150. The preferred durometer of the proximal region is between 70 and 75. The length of the outer lumen corresponds to that of the inner lumen and can be about twelve inches to about seventy inches long with a diameter of about 0.10 inches to about 3 inches. 
         [0049]    A step or steps are cut in the area of intended deflection in the distal portion  16  of the outer lumen material typically by splitting the outer lumen. The removal of the material from the outer lumen creates the space for the different durometer polymeric material. The step or steps are then filled with a geometrically matching piece of material of differing durometer as shown in  FIGS. 2 ,  4 , and  5 . This results in the creation of the different distal regions that comprise the distal portion of the outer lumen of the sheath. The filling material is PEBAX with a durometer that is typically less than 75. Other polymeric materials could also be used provided that the alternate polymeric material has a different durometer and readily fuses together with the outer lumen layer  160  material. 
         [0050]    The entire assembly of the PTFE inner lumen  70 , push/pull wires  80  and  82 , wire mesh  140  and outer lumen  160  is then encased in a shrink wrap material  170  as shown in  FIG. 13 . The sheath assembly with the shrink wrap material  170  ready for heat treating is shown in  FIG. 14 . The assembly is then heat treated in a furnace  190  as shown in  FIG. 15  at a preferred temperature of between about 350° F. to about 450° F. for about 5 to about 10 minutes in ambient atmosphere and pressure to create the final assembly. After heat treating, the remaining shrink wrap material  170  is removed from the surface of the sheath  10 . 
         [0051]      FIG. 16  shows an exemplary embodiment of a finished bi-directional asymmetric steerable sheath  10  according to the present invention. The illustration depicts the sheath  10  from the proximal region  14  through the distal portion  16  and shows the inner PTFE lumen  70 , distal support ring  72 , wire mesh  140  and push/pull wires  80  and  82  which attachment weld  92  also included in the illustration are distal regions  50 ,  52 , and  54  similar to that which is depicted in  FIG. 5 . The first distal region  50  extends annularly 360 around the sheath  10 . Distal region  50  adjoins distal region  52  which then adjoins distal region  54  at annular transition  55  which then extends to the end of the sheath.  FIG. 17  illustrates the cross section at point  17 - 17  which is prior to the distal portion  16  section which shows the inner lumen  70 , monolithic outer lumen  160 , wire mesh  140  and push/pull wires  80  and  82 .  FIG. 18  illustrates cross section  18 - 18  which depicts the outer lumen distal regions of  54  and  52 , annular transition  55 , the inner lumen  70 , wire mesh  140  and push/pull wires  80  and  82 . Finally  FIG. 19  depicts the cross section  19 - 19  of the above sheath assembly at the distal end. The cross section shown in  FIG. 19  consists of the inner PTFE lumen layer  70 , distal end support ring  72 , and pull wires  80  and  82  which are welded to the opposing sides. 
         [0052]    Thus, it can be seen that the present invention provides a physician with a sheath assembly  10  that is capable of readily deflecting the distal portion  16  in any one of a myriad of direction, both upwardly and downwardly with respect to a longitudinal axis thereof as shown in  FIG. 16 . This provides the physician with a great degree of flexibility in maneuvering the distal end  16  of the sheath  10  for performing a medical procedure inside the vasculature of a patient. 
         [0053]    It is appreciated that various modifications to the inventive concepts described herein may be apparent to those of ordinary skill in the art without departing from the spirit and scope of the present invention as defined by the appended claims.