Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Patent Application Ser. No. 60/994,188 filed Sep. 18, 2007. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to medical devices and more particularly to devices for use in insertion or implantation of catheters and the like into the vasculature of patients. 
       BACKGROUND OF THE INVENTION 
       [0003]    Catheters are used in numerous medical procedures. In particular, catheters are used for the introduction or removal of fluids from various venous regions and vessels throughout the body, such as for hemodialysis. The procedure by which these catheters are introduced to the body is delicate and complex. One particularly intricate challenge to catheterization is enlarging a hole in the flesh and vessel to be catheterized while minimizing blood loss and trauma to the patient. Generally, to insert any catheter in a blood vessel, the vessel is identified by aspiration with a long hollow needle in accordance with the Seldinger technique. When blood enters a syringe attached to the needle, indicating that the vessel has been found, a thin guide wire is then introduced, typically through the syringe needle or other introducer device, into the interior of the vessel. The introducer device is then removed, leaving the guide wire within the vessel. The guide wire projects beyond the surface of the skin. 
         [0004]    At this point, several options are available to a physician for catheter placement. The simplest option is to pass a catheter into the vessel directly over the guide wire. The guide wire is then removed. However, use of this technique is only possible in cases where the catheter is of a relatively small diameter, made of a stiff material and not significantly larger than the guide wire. If, however, the catheter is of a relatively large diameter and/or not made of a soft material, one preferable method of inserting the catheter into the vessel is through an introducer sheath. The introducer sheath is simply a large, stiff, thin-walled tube, which serves as a temporary conduit for the catheter that is being placed. The sheath is positioned by placing a dilator, which has a hollow passageway along its longitudinal axis, inside of the sheath and passing both the dilator and the sheath together into the vessel over the guide wire. The dilator expands the opening in the blood vessel to allow for catheter insertion into the vessel. The guide wire and dilator are then removed, leaving the thin-walled sheath in place. The catheter is then inserted into the vessel through the sheath. 
         [0005]    In a setting where a catheter with a hub or other attachment at the proximal end of the catheter has a feature which is larger than that of the inner diameter of the sheath, it is necessary to have a tear-away sheath that can be split away from the catheter as the sheath is being removed from the patient. An example of such a tear-away, or splittable or peelable, sheath, with dilator is set forth in U.S. Pat. No. 6,796,991, which is depicted herein in PRIOR ART  FIGS. 1 and 2  hereof. By splitting the sheath along its longitudinal axis as the sheath is being removed from the patient, the inserting physician will be able to pull out the sheath in such a way that the portion removed from the patient is split, thereby not interfering with any encumbrances on the catheter. Generally, tear-away sheaths are manufactured in a way that aids in the tearing of the sheath at two opposing points on the circumference of the sheath, thereby splitting the sheath into two halves separated longitudinally through the center of the sheath. 
         [0006]    A sheath is generally constructed with a hub at its proximal end. This hub serves as a handle, a mating point for a dilator, and a flat surface to aid in the prevention of blood loss or contamination. When a sheath needs to be split apart in order to be successfully withdrawn from the body while leaving the catheter in place, the hub will also have to be split apart in order to clear the catheter. Preferably, the hub will split along the same lines as the sheath. To accomplish this, the hub must be designed with reveals or other weaknesses along two longitudinal lines aligned with the weaknesses in the sheath. Some previous examples of these weaknesses are tabs or webs which connect two halves of the hub, or recesses in the material comprising the hub. The weaknesses in the hub will help the inserting physician to break apart the hub in line with the tear seams on the sheath. 
         [0007]    Another important facet of the hub is a set of tabs or wings that protrude from the center. These tabs not only help the inserting physician to align, insert and withdraw the sheath, but also to pull the sheath so that the sheath can be removed from around a catheter while still leaving the catheter in place. There are a number of different tab configurations, but it is important to have one which allows for easy maneuverability, control, and leverage. One design includes a hub wherein the tabs protrude from the hub perpendicular to a plane which includes the tear seams in the sheath and the longitudinal axis of the sheath. In this design, the tabs are diametrically opposed from each other and are spaced in such a way that when the tabs are grasped and pulled apart from each other, the sheath and its hub will split down the middle. Another desirable feature of the tabs is that the tabs provide leverage for breaking apart the hub in a manner that does not cause trauma to the incision in the body. 
         [0008]    During insertion, especially in the time between the removal of the dilator from the sheath and the insertion of the catheter through the sheath, it is possible for blood loss through the sheath, or the introduction of contaminants or air through the sheath and into the vessel. For this reason, it is desirable that measures be taken to prevent blood, air or contaminants from traveling through the sheath. In the past, inserting physicians have simply held their thumb over the opening in the proximal end of the sheath; however, a more permanent and reliable means for preventing blood, air or contaminants from traveling through the sheath is desirable. It is therefore desirable for the hub to include a valve located in the sheath. Such a valve would facilitate the insertion of objects such as a catheter, dilator or syringe through the sheath while restricting blood loss and reducing the chance of contaminants entering the patient&#39;s bloodstream when the sheath is not engaged with a dilator or a catheter. 
         [0009]    In the case where a sheath does not have a small diameter or a narrow point, the dilator is often used to aid in the insertion of the sheath. The dilator has a long tubular section, the outside diameter of which is slightly smaller than the inside diameter of the sheath. The dilator also has a pointed tip on its distal end and a hollow center, which runs along the entire length of the dilator. The dilator is inserted into the body with the guidewire running through its center, thereby allowing the tip of the dilator to follow the guidewire to the place that is to be catheterized. On its proximal end, the dilator may have a hub. Like the hub of the sheath, this hub can also serve a number of purposes, such as providing a stable handle to aid in guiding the dilator into the vein, and as a mechanism which can mate with the sheath hub to form a locked connection. 
         [0010]    In PRIOR ART  FIGS. 1 and 2 , a releasably locking dilator and sheath assembly and methods for releasing the dilator from the sheath and longitudinally splitting the sheath are provided. The assembly includes a dilator having a dilator hub and a sheath having a sheath hub. The sheath hub has a valve and two opposing winged tabs, each tab having a perpendicular portion and an angled portion as well as a female threaded portion. The dilator hub has a male threaded portion designed to engage the female threaded portion of the sheath hub. The dilator is released from the sheath by rotating the dilator 90° in relation to the sheath and pulling the dilator out of the sheath. The sheath is longitudinally split by creating a coupling moment on each of the winged tabs thereby forcing the sheath and the sheath hub to split longitudinally. With the sheath, the valve and the sheath hub split longitudinally, the sheath is removed from around a catheter while leaving the catheter in place. 
         [0011]    It is desired to provide a hemostasis valve for a splittable sheath, and to provide a sheath assembly with hemostasis valve and sheath hub for use therewith, that are splittable for facilitating removal of the sheath from about an inserted catheter. 
       BRIEF SUMMARY OF THE INVENTION 
       [0012]    The present invention is a hemostasis tearaway sheath assembly having a splittable sheath tube and a splittable hub affixed thereto, with the hub being at the proximal end of the sheath assembly, the sheath tube extending to a smaller diameter distal sheath end, a passageway extending through the assembly from the proximal end to the distal end and defining a longitudinal axis therethrough. The sheath tube includes frangible longitudinal lines of weakness (or seams) therealong to facilitate peeling or splitting during the tearaway procedure once splitting has been initiated by splitting apart of the hub by the practitioner. The assembly of the present invention also includes an easily split hemostasis valve contained and affixed within the hub. 
         [0013]    The hub comprises two opposing sections joined to each other at frangible joints or webs until intentionally split apart, so that the hub remains an integral one-piece unit until split by the practitioner after insertion of the catheter into a patient&#39;s vasculature has been accomplished, with a grippable wing joined to each hub section for handling and for initiating splitting in a manner known in the art. The hub also provides distinct opposing gaps between the two opposing sections that are joined at frangible sections within the gaps, and upon splitting of the hub by the practitioner, the sheath tube also splits apart as the tearaway procedure continues. The easily split hemostasis valve contained within the proximal end of the hub is, prior to splitting, selectively openable to permit insertion therethrough of a dilator and later of a catheter forming a seal therewith and therearound, but otherwise remains closed to prevent blood effusion. 
         [0014]    In a preferred embodiment, the split valve includes a distal slit partially across a transverse valve section, the slit being openable only to permit receipt therethrough of a dilator, syringe or catheter when same is pushed against the transverse valve section, and then closing sealingly when the device is withdrawn therethrough, and also closing sealingly about a guidewire remaining in place until catheter insertion. Also, preferably, the valve comprises two opposing halves, either molded separately or, as is preferable, that are formed from an integrally molded valve that is bisected and then fused together to form a weak bond that is easily broken during splitting of the sheath assembly as mentioned above. Each valve half includes a mounting flange or ear extending laterally from its proximal end, which ear includes a post-receiving aperture. Correspondingly, the sheath hub includes a valve-receiving recess at its proximal end that includes a pair of anchor posts beside the passageway that will extend through the two post-receiving apertures of the valve. Further, the assembly includes a cap comprising a pair of cap halves, which remain unfixed to each other, that are fastened to the proximal hub end in a force fit so as to compress the ears of the valve. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain the features of the invention. In the drawings: 
           [0016]      FIGS. 1 and 2  are isometric views of a PRIOR ART sheath/dilator assembly, and the sheath of the assembly shown with the dilator removed; 
           [0017]      FIG. 3  is an enlarged isometric view of the tearaway sheath assembly of the present invention, showing the sheath hub and valve cap at the proximal end of the sheath tube and the hub&#39;s gaps aligned with lines of weakness of the sheath tube; 
           [0018]      FIG. 4  is an exploded isometric view of the assembly of  FIG. 3  in which are seen the valve and two separate cap halves spaced proximally from the sheath hub proximal end; 
           [0019]      FIG. 5  is a plan view of the split valve of  FIG. 4  after the two valve portions are fused together; 
           [0020]      FIG. 6  is a cross-sectional view of the valve of  FIG. 5  taken along lines  6 - 6  thereof; 
           [0021]      FIG. 7  is an isometric view of a half valve portion prior to valve fusion; 
           [0022]      FIG. 8  is a cross-sectional view of the hub assembly with valve, with a dilator extending therethrough; 
           [0023]      FIG. 9  is an isometric view of a sheath assembly with dilator locked in position; and 
           [0024]      FIGS. 10 and 11  are, respectively, isometric views of an alternative embodiment of a complete valve and a valve half. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    In the drawings, like numerals indicate like elements throughout. Certain terminology is used herein for convenience only and is not to be taken as a limitation on the present invention. The terms “distal” and “proximal” refer, respectively, to directions closer to and away from the vascular insertion site on the patient. The terminology includes the words specifically mentioned, derivatives thereof and words of similar import. The embodiments illustrated below are not intended to be exhaustive or to limit the invention to the precise form disclosed. These embodiments are chosen and described to best explain the principle of the invention and its application and practical use and to enable others skilled in the art to best utilize the invention. 
         [0026]    In PRIOR ART  FIGS. 1 and 2 , a sheath assembly  10  is shown comprising a dilator  12  and a sheath  14 , and having a longitudinal axis “L”. Dilator  12  has a dilator hub  16  at its proximal end, and its distal end portion  18  extends beyond the distal end  20  of sheath  14  to a distal tip  22 . Sheath  14  includes a sheath tube  24  and a sheath hub  26  at the proximal end of the sheath tube, and is seen in  FIG. 2  with the dilator removed. Sheath hub  26  is seen to have grippable wings  28  to facilitate the initiation of splitting by the practitioner to peel away the sheath from an inserted catheter (not shown). To facilitate splitting of the sheath  14  from around the catheter, the sheath tube has a pair of opposed frangible seams  30 , and sheath hub  26  includes frangible webs along opposed gaps  32  that are aligned with seams  30 . The proximal end  34  of sheath  14  includes a threaded locking arrangement for locking with the dilator hub  12  prior to removal of the dilator. 
         [0027]    Sheath assembly  100  of the present invention is illustrated in  FIGS. 3 and 4 . The sheath assembly includes a sheath tube  102  with a proximal end portion  104  and extending to a distal end, with a passageway extending therebetween defining a longitudinal axis. The sheath tube  102  preferably is extruded of polytetrafluoroethylene (PTFE) having longitudinal polymeric orientation providing inherent lines of weakness represented as lines  106 , for splitting therealong once splitting is initiated at the hub seams by the practitioner after completion of the insertion of the catheter&#39;s distal portion into the vasculature of a patient (not shown). Alternatively, as is shown in PRIOR ART  FIGS. 1 and 2 , the sheath hub can having a conventional pair of opposed seams or frangible sections  106  that define weaknesses along which the sheath tube is easily split by the practitioner. 
         [0028]    Referring primarily first to  FIG. 3 , a sheath hub  110  is affixed to the proximal end portion  104  of the sheath tube, the sheath hub being affixed to the sheath tube along the distal end portion  112  of the hub. A pair of wings or tabs  114  extend from respective opposed sections  116 , 118  of hub  110  at its proximal end  120 , for gripping by the practitioner for initiating the splitting of the sheath assembly for tearing it away from the catheter, by their being pried toward the sheath distal end such that the splitting of the hub begins at its proximal end  120  and separating hub sections  116 , 118  completely from each other along a pair of opposed gaps  122 . A dilator  200  is disposed through the sheath with its proximal end portion  202  extending proximally from the sheath hub  110  and including a dilator hub  212 . Also seen in  FIG. 3  is a frangible section  124  disposed along the inside edge of gap  122  of sheath hub  110 ; the frangible section or webs on both sides of the hub join together the two hub sections  116 , 118 . 
         [0029]    Now referring to  FIG. 4 , valve  150  is shown exploded from hub  110 , the two halves  182  of cap  180  are shown exploded from hub  110  and valve  150 , and dilator hub  212  is withdrawn from the sheath enabling showing of the dilator&#39;s elongate tube  204  and clearly showing detail of the cap  180  and valve  150 . Hub  110  includes a large diameter cylindrical portion  126  extending to its proximal end  120  and to a smaller diameter distal end portion  112  whereat it is affixed to a proximal end of sheath tube  102 . A passageway extends through the hub  110  in fluid communication with the elongate passageway of the sheath tube  102 . Proximal end  120  of hub  110  includes a proximally extending wall  128  defining therewithin a valve-receiving recess  130  having extended lateral recess portions  132  to either side of the passageway  126 . Extending proximally from the recess bottom in each lateral recess portion  132  is an anchor post  136  that is generally centered with respect to the respective lateral recess portion  132  and is associated with a respective valve half. Shown just laterally outwardly of the opposite ends of wall  128  are a pair of apertures  138  for securing the cap to the hub  110 , discussed later. 
         [0030]    Hemostasis valve  150  will now be described with reference to  FIGS. 4 to 7 . Valve  150  includes opposing halves or portions  152 A, 152 B that preferably are heat-fused together along a weak but sealed interfacial joint  154 ; alternatively, the opposing halves  152 A, 152 B can be bonded with a weak silicone adhesive. At its distal end, valve  150  includes a transverse distal section  156 . Distal section  156  includes a slit  158  therethrough extending partially to the peripheral portions thereof. Valve  150  also includes a proximal cavity  160  for receipt of the distal end of a dilator or catheter and may include an annular ridge  162  for engaging the side surfaces of the device inserted thereinto. Each valve portion  152 A, 152 B includes a lateral flange or ear  164 A, 164 B at its proximal end, which further includes a post-receiving aperture  166 A, 166 B therethrough; preferably, a thick flange extends from the lateral flanges to surround the entrance to proximal cavity  160 . The valve  150  may be initially molded in two separate sections or halves, or, as is preferable, initially molded as an integral whole that is bisected into opposing halves. The valve halves  152 A, 152 B may be made of silicone and may be fused together by a weak but sealed interfacial joint  154  such as by placing the valve halves into a common conforming mold of the shape of an integral valve body and maintained at 400° F. for 1.25 hours. Optionally, an additional slit  168  can be formed through transverse distal valve section  156  partially along the weak interfacial joint  154 , thus being orthogonal to slit  158 . 
         [0031]    Referring now to  FIG. 4 , cap  180  preferably comprises two completely separate but identical halves  182 , for securing valve  150  within valve-receiving recess  130  of sheath hub  110 . The interface  184  between the cap halves  182  is aligned with gaps  122  of hub  110  and seams  108  of sheath tube. Cap  180  defines a passageway  186  extending therethrough from a beveled lead-in at the cap&#39;s proximal end, with passageway  186  sufficiently large in inner diameter for a dilator and a catheter to be movably inserted therethrough. An outer cap wall  188  extends distally to be received around wall  128  surrounding valve-receiving recess  130  of hub  110 , and securing posts  190  of the cap halves are snap-fitted and/or friction fitted into apertures  138  of hub  110 ; optionally, each cap half may also be affixed to a respective hub half-portion by adhesive. Also, optionally, the cap halves  182  may include respective protuberances and apertures along their interface  184  for precise co-alignment when assembled paired together to the hub  110 . 
         [0032]    Cap  180  may include a locking section for lockingly engaging the dilator hub  202  of the dilator  200 . The locking section is shown to comprise a pair of locking pins  192  extending proximally from a proximal surfaces of the respective cap halves, each locking pin  192  including an enlarged head  194  on the end of a pin shaft  196 . A distal end  206  of the dilator hub  202  includes a cooperating locking section adapted to grip the locking pins to secure the dilator in position assembled to the introducer sheath assembly  100 . The cooperating locking section is shown to comprise a pair of hooks  208  that extend first radially outwardly from the side of the dilator hub distal end  204  and then circumferentially a selected small distance in a common direction, thus defining a pair of post-receiving slots  210  that are each sufficiently large to receive in a snug fit thereinto the shafts  196  of the cap&#39;s posts  192  distally of their enlarged heads when the dilator  200  is fully inserted into the sheath assembly and abutting the cap, and then rotated a small angular distance in the common direction thus moving the hooks about the locking pins. 
         [0033]    The interrelationship of the various associated portions of the hub, valve and cap is best explained with respect to  FIGS. 3 and 4 . Valve  150  is seated within valve-receiving recess  130  of sheath hub  110 . The anchor posts  136  of the hub  110  extending through the apertures  166 A, 166 B of the valve ears assures that the valve halves will become separated from each other and remain with the respective hub portions when the hub is split for peeling the sheath assembly from about the catheter after catheter insertion. Similarly, the respective cap halves  182  will also remain with the respective hub portions upon splitting of the sheath hub  110 . 
         [0034]    Frangible sections or webs  124  of hub  110  that join hub sections  116 , 118  are formed adjacent the inside surface of the passageway of the hub and are very thin. It is preferred that, mainly for manufacturing reasons, the gaps  122  of hub  110  extend radially inwardly from hub outer surfaces to inner gap end portions that are U-shaped converging at the frangible webs  124 , in order for the mold inserts to remain relatively thick, robust and durable over many molding cycles and also to carefully control the thickness of the frangible webs. The webs may have a thickness, for example, of about 0.005 in (0.127 mm), and the width of the gaps  122  at the outer surfaces can be, for example, about 0.010 in (0.254 mm). 
         [0035]    It can be discerned from  FIG. 6  that the transverse distal section  156  of the valve would be abutted by a proximal end of a guide wire (not shown) during initial placement of the sheath assembly over the guide wire after the guide wire is placed in the vasculature, later by the dilator distal tip inserted through the hub and valve and later by the catheter distal tip, with the slit  158  permitting an opening therethrough in response to guide wire, dilator or catheter insertion, with the valve maintaining engagement with the outer surfaces of the guide wire, dilator or catheter as it passes therethrough; and the slit will also close against the guide wire upon withdrawal of the dilator from the sheath assembly, forming a hemostasis seal and preventing effusion of blood. The hub and the cap may be made of polyethylene or polypropylene. 
         [0036]    An enlarged cross-section of the proximal end of the assembly  100 , 200  is depicted in  FIG. 8 , wherein the sheath hub  110  contains the split hemostasis valve  150  seated therewithin, the cap half members  182 , 182  and the dilator  200  locked to the cap half members so that the dilator tube  202  extends through the valve  150  and into the sheath tube  102 . The half portions of valve  150  are secured in place by posts  136  extending proximally through apertures  166 A, 166 B. Cap posts  190  are fitted into holes in the hub half portions. Dilator hub  204  is secured to cap members  182  when hooks  208  are rotated and post-receiving slots  210  thereof are snap-fitted around locking pins  192  of the cap members. An opening  220  in the proximal portion of dilator hub  204  permits insertion therethrough of a guidewire (not shown). 
         [0037]    A view of the entire assembly is shown in  FIG. 9 , partly in cross-section to show another embodiment of valve  250  in its open state, with a valve  250  and a valve half  252  illustrated in  FIGS. 10 and 11 , respectively. Two or more rib portions  268  are provided along outer surfaces of the converging distal end portions  270  of the valve halves  252  to enhance the closing of slit  258  either entirely, if no medical device extends therethrough, or tightly around a medical device extending therethrough, by virtue of the stiffness of the added material. 
         [0038]    It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Technology Category: 1