Abstract:
A dilator ( 100 ) for expanding a vessel incision to assist insertion of a catheter thereinto and having a distal end ( 104 ) and a proximal end ( 106 ). The dilator has two portions ( 110,210 ) that are assembled together at a hinge ( 112,212 ) permitting angled-apart proximal ends ( 122,222 ) of the two portions at the proximal end ( 106 ) to be squeezed together about the hinge which slightly spreads apart the respective distal ends ( 114,214 ) of the two portions to enlarge the incision into the vessel. A spring ( 150 ) biases apart the proximal ends of the two portions to maintain the two distal ends ( 114,214 ) together until pried apart as desired to dilate the vessel incision.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority from U.S. Provisional Patent Application Ser. No. 60/757,225 filed Jan. 9, 2006. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to the field of medical devices and more particularly to vessel dilators.  
       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 and/or arterial 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.  
         [0004]     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 with a proximal end portion of the guide wire projecting beyond the surface of the skin.  
         [0005]     At this point, several options are available to the practitioner for catheter placement. The simplest option is to pass a catheter into the vessel directly over the guide wire, whereafter the guide wire is removed; a variation on this option has been adopted recently in which a stylet is inserted about the guide wire within the catheter and which extends distally from the catheter&#39;s distal tip to facilitate entry of the catheter through the vessel incision, or venectomy. Both of these techniques require that the venectomy be predilated; even with predilation it is commonly difficult to insert the catheter through the venectomy, in certain patients, especially using the guide wire only.  
         [0006]     If, however, the catheter is of a relatively large diameter and/or not made of a stiff 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. Prior to use of the sheath, usually a plurality of smaller-to-larger size dilators are used in sequence, placed onto and removed from the guide wire, to attain the appropriately large size for the venectomy. The sheath is positioned by placing the final dilator to be used, 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 through the sheath.  
         [0007]     In a setting where a catheter with a hub or other attachment at the 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. 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 point 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.  
         [0008]     Some dilator and sheath assemblies that include a connection between the dilator and sheath are known. U.S. Pat. No. 6,796,991 discloses a sheath and dilator assembly in which the sheath hub and the dilator hub having mating female and male threads to establish a connection therebetween, with the dilator being removable after sheath tip access to the vasculature is attained, after which the catheter is then inserted over the guide wire and into and through the sheath into the vasculature.  
         [0009]     Dilating devices are also known for use in dilating vasculature incisions for insertion thereinto of medical tubing into the vasculature such as a catheter or an intravenous tube. One such device is disclosed in U.S. Pat. No. 2,842,133 and has two embodiments each having first and second components that together define an elongate channel through which tubing is insertable. In one version, the first and second components are affixed to respective hinged transverse spring-loaded finger pieces, and their distal portions are pivotable apart against spring bias when the finger pieces are squeezed together, to part the distal ends of the two components and dilate the vein when the pair of pieces are manually squeezed together.  
         [0010]     It is desired to provide a dilating device that is easily manipulated and operated by the practitioner, in a single step procedure, for catheter insertion.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention, briefly, is a dilator assembly having first and second dilator portions, each having proximal and distal portions, a longitudinal axis extending between the first and second dilator portions, and a longitudinal passageway extending along the longitudinal axis between the distal portions. The first and second dilator portions are hingedly connected proximally of their distal portions, and the passageway is adapted to accommodate a catheter being inserted longitudinally therethrough. The pivoting dilator is operable between an insertable position and a dilating position by forcing the at least one of the first and second proximal ends toward the longitudinal axis and pivoting apart the first and second distal portions.  
         [0012]     Preferably, the first and second distal end portions are frustoconical when together and have non-sharp distal tips, and no sharp exposed edges and corners. Also, the first and second proximal portions may be spring biased apart causing the first and second distal portions are spring biased together, or the first and second distal portions may be spring biased together distally of the hinge, causing the proximal portions to be biased apart. Preferably, also, the first and second proximal portions are ergonomically shaped handles for manual gripping and squeezing. The hinged connection between the first and second dilator portions may be located approximately midway along the longitudinal axis, and preferably is laterally offset to permit access to the longitudinal passageway for insertion of a catheter into the dilator.  
         [0013]     The dilating device of the present invention can replace the use of sequential dilators and introducer sheaths in a single step procedure that enables controlled venectomy dilation to only the desired size; and its use significantly reduces the potential of air embolism or blood leakage that would occur after removal of a dilator from a sheath just prior to insertion of the catheter into the sheath, in prior methods.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     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:  
         [0015]      FIG. 1  is an isometric view of a pivoting dilator, according to a first embodiment of the present invention;  
         [0016]      FIG. 2  is an isometric view of the pivoting dilator shown in  FIG. 1  opened to illustrate the inside surfaces;  
         [0017]      FIG. 3  is a side view of a second embodiment of the pivoting dilator;  
         [0018]      FIG. 4  is a side view of a third embodiment of the pivoting dilator;  
         [0019]      FIG. 5  is an isometric view of one of the two identical halves of the pivoting dilator in  FIG. 4 ;  
         [0020]      FIG. 6  is an isometric view of a fifth embodiment of dilator, an assembly having multiple components;  
         [0021]      FIG. 7  is an enlarged isometric view of the hub connection of the dilator assembly of  FIG. 6 ;  
         [0022]      FIGS. 8 and 9  are top and side views of the dilator assembly of  FIGS. 6 and 7 ;  
         [0023]     FIGS.  10  to  13  are, respectively, an isometric, top, side and end view of one of the two proximal portions of the dilator assembly of FIGS.  6  to  9 ;  
         [0024]     FIGS.  14  to  18  are isometric, top, side, end and enlarged hub views of one distal portion of the dilator assembly of FIGS.  6  to  9 ; and  
         [0025]     FIGS.  19  to  23  are isometric, top, side, end and enlarged hub views of the other distal portion of the dilator assembly of FIGS.  6  to  9 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]     In the drawings, like numerals indicate like elements throughout. The words “proximal” and “distal” refer to directions away from and closer to, respectively, the insertion tip of a dilator according to the present invention. The terminology includes the words above specifically mentioned, derivatives thereof, and words of similar import. The following describes a preferred embodiments of the invention. However, it should be understood based on this disclosure, that the invention is not limited by the preferred embodiment described herein.  
         [0027]     Referring to  FIG. 1 , a vessel dilator  100  according to the present invention is disclosed. The dilator  100  is used to expand a vessel to assist a physician during insertion of a catheter (not shown) into a patient&#39;s blood vessel (not shown) usually over a guide wire (not shown) extending through the dilator. The dilator  100  includes a distal end  104  that is to be inserted into the blood vessel through an incision or venectomy, and also includes a proximal end  106  that remains outside of the blood vessel when the distal end  104  of the dilator  100  is inserted into the blood vessel. A longitudinal axis  108  extends through the dilator  100  between the distal end  104  and the proximal end  106 .  
         [0028]     A first dilator portion  10  extends between the distal end  104  and the proximal end  106  generally on one side of a plane P which encompasses the longitudinal axis  108 . A second dilator portion  210  extends between the distal end  104  and the proximal end  106  generally on an opposing side of the plane P from the first dilator portion  110 . The first dilator portion  110  includes a male hinge portion  112  disposed between the distal end  104  and the proximal end  106 . The second dilator portion  210  includes a female hinge portion  212 , adapted to mate to the male hinge portion  112  and also disposed between the second distal end  204  and the second proximal end  206 .  
         [0029]     Referring now to  FIGS. 1 and 2 , the first dilator portion  110  has a first distal portion  114  concluding in a first distal tip  120  and having a first distal outer surface  116  and a first distal inner surface  118 . The second dilator portion  210  has a second distal portion  214  concluding in a second distal tip  220  and is defined by a second distal outer surface  216  and a second distal inner surface  218 . The first and second distal portions  114 , 214  have a generally C-shaped cross-section, when the cross-sectional view is taken in a plane that is perpendicular to the longitudinal axis  108 , and together define a passageway through the first and second distal portions.  
         [0030]     The first dilator portion  110  has a first proximal portion  122  having a first inner surface  124  that is generally semicircular and concave, and has a second dilator portion  210  has a second proximal portion  222  that has a second inner surface  224  that is generally semicircular and concave. Preferably, the semicircular and concave shape of the first and second inner surfaces  124 , 224  is an extension of the C-shaped cross section of the first and second distal portions  114 , 214 , thereby giving the first and second inner surfaces  124 , 224  a generally C-shaped cross section, and together define a passageway through the first and second proximal portions when the first and second proximal portions  122 , 222  are pivoted together that aligns with the passageway through the first and second distal portions.  
         [0031]     Both the first and second distal portions  114 , 214  are tapered away from the proximal portions  112 , 212 , respectively, decreasing in width and thickness moving closer to their respective distal tips  120 , 220  distally along the longitudinal axis  108  from the proximal end  106 .  
         [0032]     With the exception of the male hinge portion  112  and the female hinge portion  212 , preferably the first dilator portion  110  and the second dilator portion  210  are generally mirror images of each other. Those skilled in the art will recognize that the first and the second dilator portion  110 , 210  may have either the male hinge portion  112  or the female hinge portion  212 .  
         [0033]     Preferably, the male hinge portion  112  has a generally circular profile and extends from a point on the first dilator portion  110  that is located between the first distal portion  114  and the first proximal portion  122 . The male hinge portion  112  is disposed about a hinge axis  113  extending therethrough that is located within the plane P and is perpendicular with the longitudinal axis  108 . Preferably, the male hinge portion  112  comprises two portions that are disposed one on either side of the C-shaped cross section of the first inner surface  124 , so that there is an unobstructed passageway extending between the proximal end  106  and the distal end  104  along the first proximal inner surface  124  and the first distal inner surface  118 . The female hinge portion  212  is generally C-shaped complementary to the generally circular profile of the male hinge portion  112 , and disposed along the second dilator portion  210  between the second proximal portion  222  and the second distal portion  214 . The open end of the generally C-shaped female hinge portion  212  faces the first dilator portion  110 .  
         [0034]     Preferably, the female hinge portion  212  is sized to hingedly engage the male hinge portion  112  when the male hinge portion  112  is inserted inside of the open end of the female hinge portion  212 . When the dilator is assembled, the female hinge portion  212 , like the male hinge portion  112 , is disposed about the hinge axis  113 . Preferably, the female hinge portion  212  comprises two portions disposed one on either side of the C-shaped cross section of the second inner surface  224  at the same points along the hinge axis  113  as the male hinge portion  112 , so that there is an unobstructed passageway extending between the proximal end  106  and the distal end  104  along the second proximal inner surface  224  and the second distal inner surface  218 .  
         [0035]     Preferably, when the male hinge portion  112  is engaged with the female hinge portion  212 , the female hinge portion  212  is partially rotatable about both the male hinge portion  112  and the hinge axis  113 . While the current embodiment shows the male hinge portion  112  is disposed on the first dilator portion  110  and the female hinge portion  212  is disposed on the second dilator portion  210 , those skilled in the art will recognize that there are other hinge configurations that may be used to achieve the same result of hingedly connecting the first dilator portion  110  to the second dilator portion  210  without departing from the scope of the present invention. An example of such an alternate embodiment as shown in  FIGS. 4 and 5 , is a dilator  100  wherein the first dilator portion  110  may have one male hinge portion  112  and one female hinge portion  212 , and correspondingly, the second dilator portion  210  may also have one male hinge portion  112  and one female hinge portion  212 . This type of optional configuration for the dilator portions  110 , 210  provides for two identical dilator portions to be hingedly mated together to form the dilator  100 , thereby reducing production costs. In assembly, the mating male and female hinge portions  112 ,  212  of the first and second dilator portions  110 , 210  may be mated together to hingedly connect the first dilator portion  110  to the second dilator portion  210 .  
         [0036]     As shown in  FIG. 1 , when the assembled dilator  100  is in an insertable position, the first and second distal ends  114 , 214  are disposed towards each other and the first and second proximal portions  122 , 222  are angled away from the plane P. The portions of the first and second proximal portions  122 , 222  that are closest to the hinge axis  113  are the portions that are closest to the plane P. The first and second proximal portions  122 , 222  are then sloped away from the plane P in such a way that the most proximal points on the first and second inner surfaces  124 , 224  are the portions of the inner surfaces  124 , 224  that are furthest away from the plane P.  
         [0037]     The first and second proximal portions  122 , 222  have first and second gripping surfaces  126 , 226  respectively. Preferably, the first gripping surface  126  is opposed to the second gripping surface  226  so that during operation the first gripping surface  126  may be squeezed relatively toward the second gripping surface  226 . Squeezing the first gripping surface  126  towards the second gripping surface  226  pivots the dilator from a generally insertable position to a generally dilating position.  
         [0038]     Preferably, the pivoting dilator  100  is biased in the insertable position using a biasing member, such as a torsion spring  150 , shown in  FIG. 2 . The torsion spring  150  is located between the first proximal end  122  and the hinge axis  113  and pushes the first proximal end  122  and the second proximal end  222  away from each other and the plane P. Torsion spring  150  has an opening  152  therethrough aligned with the passageway between the first and second distal portions  114 , 214 . While  FIG. 2  shows a torsion spring  150  as the biasing member, those skilled in the art will recognize that other types of biasing members may be used to bias the dilator  100  in the insertable position. The biasing member may be anything that will squeezably retain the dilator  100  in the insertable position, that does not obstruct the passageway defined by and between the first and second distal portions.  
         [0039]     When the first and second proximal ends  122 , 222  are squeezed together the pivoting dilator  100  pivots into a dilating position, and a cavity is formed along the longitudinal axis  108  that is defined by the first inner surface  124  and the second inner surface  224 . Preferably, the cavity is large enough to allow a catheter (not shown) to be inserted into the patient&#39;s blood vessel between the first dilator portion  110  and the second dilator portion  210 . While the present embodiment shows a first inner surface  124  and a second inner surface  224  having generally semicircular shapes, to accommodate a catheter with a circular cross section, those skilled in the art will recognize that the first and second inner surfaces  124 , 224  may be shaped to accommodate catheters with many different types of cross-sectional shapes.  
         [0040]     Preferably, the dilator  100  is made from a biocompatible rigid or semi-rigid material. Examples of such a material are: titanium, stainless steel, nylon, polyvinylchloride, acrylic, polycarbonate or any other suitable biocompatible rigid or semi-rigid material. Those skilled in the art will recognize that this list of materials is merely exemplary and that there are other suitable materials that may be used to make the dilator  100  without departing from the scope of the present invention.  
         [0041]     In use, an incision is made into a patient&#39;s skin and then, using the well-known Seldinger technique, an opening is made into the selected vessel. A guidewire (not shown) is then inserted through the incision and into the vessel opening until its distal end is placed at a selected site along the vessel using known imaging techniques. The proximal end of the guidewire protruding from the patient is inserted between the first distal end  114  and the second distal end  214 . The pivoting dilator  100 , biased in the insertable position, is then slid distally along the guidewire until the distal end  104  of the pivoting dilator  100  is disposed within the patient&#39;s vessel and the proximal end  106  of the pivoting dilator remains outside of the vessel.  
         [0042]     With the pivoting dilator  100  partially disposed within the vessel, the first proximal end  122  is then squeezed towards the second proximal end  222  pivoting the dilator  100  about hinge axis  113  to the dilating position thereby spreading the first and second distal portions  114 , 214  away from each other and dilating the vessel. With the dilator  100  in the dilating position and the vessel dilated, the guidewire is removed. Alternatively, the guidewire may be removed prior to squeezing of the first and second proximal ends  122 , 222  towards each other. Optionally, the guidewire may be left in the vessel until after the catheter is inserted.  
         [0043]     The distal tip of the catheter is inserted between the first proximal end  122  and the second proximal end  222 . In a situation where the inserting physician has left the guidewire in the vessel, the catheter is inserted over the guidewire; however, if the guidewire has been removed prior to the insertion of the catheter, the catheter may be inserted without the use of a guidewire. With the distal tip of the catheter between the first and second proximal ends  122 , 222 , the catheter is then slid distally, past the first and second proximal portions  114 , 214  and the first and second hinge portions  112 , 212  and into the patient&#39;s vessel.  
         [0044]     A second embodiment of a pivoting dilator  300  is shown in  FIG. 3 . The dilator  300  has a proximal end  306 , a distal end  304  and a longitudinal axis  308  extending therethrough between the proximal end  306  and the distal end  304 . The dilator  300  comprises a first dilator portion  310  and a second dilator portion  410 . The first dilator portion  310  and the second dilator portion  410  are generally mirror images of each other and are hingedly joined to each other by a hinge pin  311 , disposed within a first hinge portion  312  and a second, similar hinge on the opposite side (not shown). Each of the first dilator portion  310  and the second dilator portion  410  have a generally semicircular cross-section, when cut in a plane perpendicular to the longitudinal axis  308 . The first dilator portion  310  has a first proximal end  318  and first distal end  314 , having a first distal tip  316 . The second dilator portion  410  has a second proximal end  418  a second distal end  414 , having a second distal tip  416 .  
         [0045]     The proximal end  306  is generally semi-circular in shape, when viewed from the side, as shown in  FIG. 3 . The first proximal end  318  and the second proximal end  418  each form approximately one half of the semi-circular shape of the proximal end  306 , thereby forming a semi-circular cross-sectioned proximal end  106 . The first and second proximal ends  318 , 418  extend proximally from the hinge pin  311  and away from each other. First and second proximal tip portions  322 , 422  are located at the proximal-most part of the first and second proximal portions  318 , 418  and in a direction that is generally parallel to the longitudinal axis  308 . A first gripping surface  324  and a second gripping surface  424  are preferably disposed on the first and second proximal portions  318 , 418  respectively and on the sides of the respective proximal portions  318 , 418  that are furthest from the longitudinal axis  308  located directly therebetween. The first and second distal tips  316 , 416  define a distal opening  305  around the longitudinal axis  308  that is sized to allow the dilator  300  to be inserted into a patient&#39;s vessel over a guidewire.  
         [0046]     A first proximal retaining rib  320  and a first distal retaining rib  321  are located on the first dilator portion  310 , preferably located just distally of the hinge pin  311  and closer to the hinge pin  311  than the first distal tip  316 . A second proximal retaining rib  420  and a second distal retaining rib  421  are located on the second dilator portion  410  just distally of the hinge pin  311  and closer to the hinge pin  311  than the second distal tip  416 . The proximal and distal retaining ribs  320 , 420 ;  321 , 421  are aligned with each other in order to form retaining ribs that completely encircle the dilator  306 . A biasing member, such as a rubber band  325 , is disposed around the dilator  300  and retained proximally of the distal retaining rings  321 , 421  and distally of the proximal retaining rings  320 , 420 . The rubber band  325  biases the dilator in the closed, or insertable, position. Operation of the dilator  300  is similar to the operation of the dilator  100 .  
         [0047]     A third embodiment of a dilator  500  is shown in  FIGS. 4 and 5 . Like the previous embodiments disclosed herein, the dilator  500  of  FIG. 4  comprise first and second dilator portions  510 , 610  that preferably are identical to each other. The dilator  500  comprises a proximal end  506 , a distal end  504  and a longitudinal axis  508  extending therethrough between the proximal end  506  and the distal end  504 . In use, the distal end  504  is inserted into the vessel to be dilated (not shown) and the proximal end  506  remains outside of the vessel.  
         [0048]     The first dilator portion  510  comprises a first distal portion  514  located at the distal end  504  of the dilator  500 , a first proximal portion  522  disposed at the proximal end  506  of the dilator  500  and a first hinge portion  512  disposed between the first distal portion  514  and the first proximal portion  522 . As shown best in  FIG. 5 , the first hinge portion  512  includes a first male hinge portion  512   a  and a first female hinge portion  512   b . Referring back to  FIGS. 4 and 5 , the second dilator portion  610  comprises a second distal portion  614  located at the at the distal end  504  of the dilator  500 , a second proximal portion  622  disposed at the proximal end  506  of the dilator  500  and a second hinge portion  612  disposed between the second distal portion  614  and the second proximal portion  622 .  
         [0049]     Like the other embodiments described herein, as shown best in  FIG. 5 , each of the first dilator portion  510  and the second dilator  610  portion have a generally “C” shaped cross-section, when the cross-sectional view is taken in a plane that is perpendicular to the longitudinal axis  508 . Combined, the first and second dilator portions  510 , 610  form a dilator  500  having a generally circular cross section. The first and second dilator portions  510 , 610  define a generally circular passageway, extending therethrough along the longitudinal axis  508 .  
         [0050]      FIG. 5  shows the first dilator portion  510 , which is one half of the pivoting dilator assembly  500  and is identical to the second dilator portion  610  of  FIG. 4 . The first male hinge portion  512   a  is generally circular in shape and is centered about a hinge axis  513 . The first female hinge portion  512   b  is generally “C” shaped and is also centered about the hinge axis  513 . The first female hinge portion  512   b  is sized to hingedly engage a second male hinge portion (not shown) of the second dilator portion  610 , which is identical to the first male hinge portion  512   a  of the first dilator portion  510 . Likewise, the first male hinge portion  512   a  is sized to hingedly engage a second female hinge portion (not shown) of the second dilator portion  610 , which is identical to the first female hinge portion  512   b  of the first dilator portion  510 .  
         [0051]     Each of the first and second proximal portions  522 , 622  respectively extend in a generally proximal direction from the first and second distal portions  514 , 614  and at an angle β from the longitudinal axis  508 , shown in  FIG. 4  as being about 5 degrees. Preferably, the first and second proximal portions  522 , 622  and the first and second distal portions  514 , 614  meet, respectively, at a point proximate to the first and second hinge portions  512 , 612  respectively. The dilator may also have a biasing member adapted to bias the dilator in the inserting position, such as the biasing members  150  and  325  shown in  FIGS. 2 and 3 , respectively. As shown in  FIG. 4 , biasing member  525  may be a rubber band that biases together the distal portions  514 , 614  when in the closed position, where first and second retaining ribs  520 , 521 ;  620 , 621  are sized to retain biasing member  525  therebetween at a location just distal of the hinge portions  512 , 612 . The first and second proximal retaining ribs  520 , 620  and the first and second distal retaining ribs  521 , 621  mate to form retaining ribs that completely encircle the dilator  500  when the dilator  500  is disposed in the insertable position.  
         [0052]     A first handle  530  is disposed on the first proximal portion  522  and is generally circular in shape and sized to accommodate the inserting practitioner&#39;s finger or thumb during use of the dilator  500 . Preferably, a part of the first handle  530  is fixedly connected to the first proximal portion  522  and a first support bar  532  joined to first handle  530  extends to a point on the first dilator portion  510  located between the first proximal portion and the first hinge portion  512 , but may extend to any point on the first dilator portion  510 . The support bar  532  is preferably fixedly connected to both the first dilator portion  510  and the first handle  530  and may also be sized to eliminate any space between the first support bar  532 , the first proximal portion  522  and the first handle  530 . A second handle  630  is disposed on the second proximal portion  622 . Preferably, the second handle  630  is identical to first handle  530 , with a second support bar  632  extending to a point on the second dilator portion  610 , located between the second proximal portion  622  and the second hinge portion  612 , but may extend from the second handle  630  to any point on the second dilator portion  610 . The support bar  632  is preferably fixedly connected to both the second dilator portion  610  and the second handle  630  and similarly may also be sized to eliminate any space between the second support bar  632 , the second proximal portion  622  and the second handle  630 . Those skilled in the art will recognize that other handle configurations may be utilized to facilitate the operation of the dilator  500 . Those skilled in the art will also recognize that each of the first dilator portion  510  and the second dilator portion  610  may each be of unitary construction or constructed as an assembly.  
         [0053]     Optionally, the first proximal portions  522 , 622  of the proximal ends  506 , 606  of the two portions  510 , 610  may be oriented at a wider angle β where β is about 45 degrees, for the convenience of the practitioner, but the angle could be up to 50 degrees or so or less than 45 degrees. Providing the two dilator proximal ends  506 , 606  initially at such an angle provides a clearance for insertion of the catheter itself into the passageway between the distal ends  514 , 614  and through the distal tip  504  of the dilator which will then force open the distal ends  514 , 614  upon frictional engagement with the inner surfaces thereof adjacent the distal dilator tip  504 , with the handle defined by proximal ends  506 , 606  being a means to steady the dilator.  
         [0054]     A fourth embodiment is disclosed in FIGS.  6  to  23 , of dilator assembly  700 . Dilator  700  is made of several components: first and second proximal or handle portions  702 , 704 ; first and second distal portions  706 , 708  defining a longitudinal passageway  710  therethrough; and first and second hub sections  712 , 714  (shown as integral with distal portions  706 , 708 , respectively) to which the proximal and distal portions are joined.  FIG. 6  is an isometric view of dilator assembly  700 , shown in its pivoted-open position;  FIG. 7  is an enlarged isometric view of the hub connection;  FIGS. 8 and 9  are top and side views of the dilator assembly  700 .  
         [0055]     First and second proximal or handle portions  702 , 704  are mirror images of each other, and first handle portion  702  is shown in an isometric view ( FIG. 10 ), a top view ( FIG. 11 ), a side view ( FIG. 12 ) and an end view ( FIG. 13 ). FIGS.  11  to  13  illustrate the complex angle of the proximal end portion  716  with respect to the distal end portion  718  of first handle portion  702 . Similarly angled is proximal end portion  720  from distal end portion  722  of second handle portion  704 . Angle γ in  FIG. 11  may be about 16 degrees; angle δ in  FIG. 12  may be about 27 degrees; and the angle ε in  FIG. 13  may be about 30 degrees, as is illustrated. Extending from the distal portions  718 , 722  are connection sections  724 , 726  of first and second handle portions  702 , 704  each containing a pair of bores therethrough through which screws  730  will extend to join handle portions  702 , 704  to respective first and second hub sections  712 , 714 , by being threaded into aligned bores  732  (see FIGS.  15  to  22 ) thereof.  
         [0056]     First and second hub sections  712 , 714  are joined at a hinge  734 , and are pivotable with respect to hinge  734  within a limited range, such as about ten degrees, by manipulation of first and second handles  702 , 704 , opening and closing first and second distal portions  706 , 708  and their passageway portions  710   a ,  710   b.    
         [0057]     Referring now to  FIGS. 14 and 19 , first and second distal portions  706 , 708  are seen in isometric views to include elongated first and second semi-cylindrical sections  736 , 738  and tapered first and second distal end sections  740 , 742  that extend to respective first and second distal tips  744 , 746  that together form a distal tip  750  of the dilator device  700  when in the closed position, as shown in  FIGS. 8 and 9 . Distal tip  750  preferably defines an aperture that may be as small as 0.046 inches (1.17 mm), but it could be smaller depending on the gauge of the guide wire to be used, needing only be large enough to accommodate the diameter of a guide wire extending therethrough. When the dilator assembly  700  is pivoted to its open position, the lateral opening between the respective distal tips  744 , 746  may be as large as about 0.200 to 0.300 inches (5.1 to 7.6 mm). Further details of distal portions  706 , 708  are seen in top and side views  FIGS. 15, 16 ,  20  and  21 , end views  FIGS. 17 and 22  and enlarged hub views  FIGS. 18 and 23 .  
         [0058]     First and second hub sections  712 , 714  are seen, in FIGS.  14  to  23 , to have side walls  752 , 754  that surround and define the proximal end of passageway  710 . Beveled interior surfaces  764  of proximal ends  756 , 758  diverge to define a lead-in to facilitate insertion thereinto of the distal tip of a catheter assembly into passageway  710 , and the beveled surfaces may be each at a respective angle of about 5 degrees from axial. The proximal ends  756 , 758  of the side walls also define the pivoting mechanism. As shown in the Figures, the pivoting mechanism comprises two portions aligned with each other on opposing sides of the passageway  710  to define a pivot axis transverse to the passageway  710 . On each side a pivot portion comprises a cylindrical embossment  760  (see  FIG. 18 ) that is rotatably received within a substantially circumferential seat  762  (see  FIG. 23 ); the two cylindrical embossments  760  are integral portions of hub section  714 , projecting from side walls  754 , while the two seats  762  are integrally defined into the side walls  752  of hub section  712 . As shown in  FIGS. 18 and 23 , beveled surfaces  766  of proximal ends  756  of side walls  752  are at an angle of about 5 degrees and will abut beveled surfaces  768 , also at an angle of about 5 degrees, of proximal ends  758  of side walls  754  when the dilator assembly  700  is pivoted into its open position, so that the abutting beveled surfaces could serve as a stop to limit the size of opening.  
         [0059]     With reference now to  FIGS. 7, 14  and  19 , it may be seen that the passageway  710  extending along first and second distal portions  706 , 708  is oval/rectangular in cross-section, thus being able to accommodate catheters that are round having a diameter about equal to the narrower dimension, but also being able to accommodate double catheters such as the SCHON CATH® catheter sold by AngioDynamics, Queensbury, N.Y. The distal tip can be opened to a width selected by the practitioner to be sufficient for the catheter to extend therepast through the venectomy and into the vasculature of the patient.  
         [0060]     It is preferable in the embodiment of dilator assembly  700  for at least the handles to be of rigid material such as stainless steel. The stainless steel could also be used for the distal portions. Other materials that may be useful include nylon 6/6, of which the hub sections could be made, in which cases the screws  760  could be rivets. An option with this embodiment is that the handles and hub sections could be sterilized for re-use, with an array of different sizes of dilator portions that range in size for use with catheters of varying diameters.  
         [0061]     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.