Abstract:
A telescoping catheter is adapted to provide improved support and protection for a drive cable by providing, in addition to an outer sheath and a telescoping sheath, an inner sheath surrounding the drive cable. The outer sheath has a relatively larger diameter, to allow for a flared end of the telescoping sheath to pass freely within the outer sheath. The inner sheath protects and supports the drive cable when the telescoping catheter is extended and the drive cable would otherwise only be protected and supported by the outer sheath having a diameter too large to provide the desired amount of support and protection for the drive cable.

Description:
FIELD OF THE INVENTION  
       [0001]     The field of the invention relates to medical devices, and more particularly to telescoping catheters such as those used to conduct ultrasonic imaging.  
       BACKGROUND OF THE INVENTION  
       [0002]     In the medical arts, catheters are frequently used to diagnose and treat various disorders in a patient, such as clogged or blocked blood vessels. A catheter is introduced into a blood vessel of a patient by, for example, making an incision in the patient over the blood vessel and inserting the catheter into the blood vessel of the patient. A catheter operator such as a physician then maneuvers the catheter through the blood vessels of the patient until the catheter is properly situated to diagnose or treat the disorder. Since maneuvering a catheter within a patient can sometimes be a difficult task, requiring a high degree of care and time taken to change the position of the catheter, a type of catheter known as a telescoping catheter is frequently used to perform these diagnoses and treatments.  
         [0003]     Conventional telescoping catheters include two basic components which are designed to telescope in relationship to each other. The first component includes a drive cable with a medical device such as an ultrasonic transducer or other imaging device mounted on the distal end of the cable. The proximal end of the cable is attached to a housing at the proximal end of the catheter. This housing contains components adapted to interface the drive cable with a power source, as well as other components, such as a flush port for introducing liquid solutions into the catheter, or other components useful to aid a physician or other operator in effectively and efficiently using the catheter to diagnose and treat a patient.  
         [0004]     A proximal portion of the drive cable is covered by a flexible proximal sheath, which is attached to the proximal end of the catheter. This proximal sheath shields the drive cable from the external environment, thereby preventing contaminants from entering the patient via the catheter. The sheath also provides support for the drive cable, to restrain the drive cable from excessive flexing, bending, or other undesirable changes in location or angle.  
         [0005]     The second component includes a flexible distal sheath which covers the distal portion of the drive cable. The distal end of the distal sheath may be sealed shut to prevent the distal end of the drive cable from contacting the patient directly, or it may be open, to allow the distal end of the drive cable to protrude out through the distal sheath and into the patient. This distal sheath also shields the drive cable from the external environment and provides support for the drive cable, as described above.  
         [0006]     The proximal sheath and drive cable are adapted to telescope in relationship to the distal sheath. The telescoping relationship allows the catheter operator to move the first component including the medical device proximally and distally within the catheter, without having to move the entire catheter within the patient. This allows the catheter operator to easily change the location of the medical device within the patient.  
         [0007]     In order to prevent the interior of the catheter from being exposed to the external environment, conventional telescoping catheters are designed to stop the telescoping movement of the proximal sheath away from the distal sheath before the proximal end of the distal sheath disengages from the distal end of the proximal sheath. For example, where the proximal sheath telescopes inside the distal sheath, the proximal end of the distal sheath may have a lip or detent extending inwardly, to catch against a corresponding lip, detent or flare on the distal end of the proximal sheath, and thereby prevent the proximal and distal sheaths from disengaging from each other. Alternatively, where the distal sheath telescopes inside the proximal sheath, the distal end of the proximal sheath may have a lip or detent extending inwardly, to catch against a corresponding lip, detent or flare on the proximal end of the distal sheath.  
         [0008]     In order to accommodate the lip, detent or flare on the end of the innermost of the two sheaths, and still allow the two sheaths to telescope in relationship to each other, the internal diameter of the outermost of the two sheaths must be large enough to allow the lip, detent or flare to travel unimpeded along the inside of the outermost of the two sheaths. Therefore, the internal diameter of the outermost of the two sheaths is substantially larger than the external diameter of the drive cable extending along the inside of both of the sheaths.  
         [0009]     When the telescoping catheter is fully compressed, this does not pose a problem, as the innermost of the two sheaths, whose internal diameter is only slightly larger than the external diameter of the drive cable, provides the desired support for the drive cable. However, as the telescoping catheter is being extended, the innermost sheath is retracted from covering the drive cable, leaving only the outermost sheath to provide support and protection to the drive cable. Since this outermost sheath is substantially larger in internal diameter than the external diameter of the drive cable, the drive cable is substantially unsupported and unprotected within the catheter.  
         [0010]     Therefore, there is a need for an improved telescoping catheter.  
       SUMMARY OF THE INVENTION  
       [0011]     An improved telescoping catheter includes an additional sheath around the drive cable, inside the formerly innermost sheath of the catheter body, which additional sheath extends along the portion of the drive cable which would be otherwise exposed when the innermost sheath is retracted from the drive cable during extension of the telescoping catheter. The additional sheath provides the needed support and protection for the drive cable even when the telescoping catheter is extended.  
         [0012]     Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     In order to better appreciate how the above-recited and other advantages and objects of the present inventions are obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof, which are illustrated in the accompanying drawings. It should be noted that the components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views. However, like parts do not always have like reference numerals. Moreover, all illustrations are intended to convey concepts, where relative sizes, shapes and other detailed attributes may be illustrated schematically rather than literally or precisely.  
         [0014]      FIG. 1  depicts a catheter in accordance with an example embodiment of the invention.  
         [0015]      FIG. 2A  depicts a side view of the distal telescoping component of the catheter of an example embodiment of the invention.  
         [0016]      FIG. 2B  depicts a side view of the proximal telescoping component of the catheter of an example embodiment of the invention.  
         [0017]      FIG. 3  depicts a side view of the catheter of an example embodiment of the invention, with the catheter partially extended.  
         [0018]      FIG. 4  depicts a side view of the catheter of an example embodiment of the invention, with the catheter extended.  
         [0019]      FIG. 5  depicts a cross-section of the catheter of  FIG. 3 .  
         [0020]      FIG. 6  depicts a spacer used in the catheter of an example embodiment of the invention.  
         [0021]      FIG. 7  depicts the distal telescoping component of the catheter of an example embodiment of the invention, including the spacer of  FIG. 6 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]     An example embodiment of an improved telescoping catheter  10  is shown in  FIG. 1  and described as follows. The catheter  10  includes a proximal end  20  and a member located distally from the proximal end  20 , such as a hub  30 . A drive cable  40  extends from the proximal end  20  of the catheter  10  along to and through the hub  30 . The cable  40  extends past the hub  30 , and the distal end (not shown) of the cable  40  is typically tipped with some form of medical device (not shown), such as an imaging head, an ultrasonic transducer, a light imaging device, a cutting head, or some other device. The particular device chosen for the tip of the distal end of the cable  40  is a design choice depending on the desired function for the catheter  10 , and is not limited by the invention.  
         [0023]     The cable  40  is adapted to be maneuvered within the sheaths  50 ,  60 ,  70  of the catheter  10  as desired by an operator of the catheter  10 , such as an imaging technician or a physician. For example, the cable  40  may rotate an imaging device such as an ultrasound imaging device or a light imaging device, to allow images to be taken of portions of the patient&#39;s body. Additionally, the cable  40  may be extended or retracted distally or proximally to reposition the imaging device or other medical device.  
         [0024]     The catheter  10  further includes a first sheath  50  fastened to the proximal end  20  of the catheter  10 . The first sheath  50  extends distally from the proximal end of the catheter  10 , surrounding a proximal portion of the cable  40 . The first sheath  50  extends distally into the open proximal end of a second sheath  60 , and terminates in a flared end  70 . The flared end  70  is adapted to abut a corresponding detent  65  on the proximal end of the second sheath  60 , to prevent the first sheath  50  from disengaging from the second sheath  60 . Since the external diameter of the flared end  70  is greater than the internal diameter of the second sheath  60  as narrowed by the detent  65 , the flared end  70  is prevented from passing proximally past the detent  65 . In alternative embodiments, the first sheath  50  may terminate in a detent, a lip, or some other structure adapted to engage with a corresponding detent or other structure on the proximal end of the second sheath  60 . Still other means of preventing the first sheath  50  from disengaging from the second sheath  60  may be used.  
         [0025]     The second sheath  60  is attached to the proximal end of the hub  30 , and extends proximally along the catheter  10 , surrounding a distally located portion of the cable  40  as well as a third sheath  80 , as discussed below. The second sheath  60  terminates in the proximally located detent  65 . This detent  65  may be located directly on the proximal end of the second sheath  60 , or it may be located on a structure attached to the proximal end of the second sheath  60 , such as a receptacle  75 . The detent  65  is adapted to engage the flared end  70 , to prevent the second sheath  60  from disengaging from the first sheath  50 , as discussed above. The internal diameter of the second sheath  60  is large enough to allow the flared end  70  of the first sheath  50  to freely move proximally and distally within the second sheath  60 .  
         [0026]     The third sheath  80  is attached to the distal end of the hub  30 , and extends proximally along the catheter  10 , surrounding the cable  40 . The third sheath  80  extends through the hub  30 , along the lumen formed by the second sheath  60 , penetrating into the lumen formed by the first sheath  50 , and terminating within the first sheath  50 . The diameter of the lumen within the third sheath  80  is large enough to allow the cable  40  to freely move proximally and distally within the third sheath  80 , yet small enough to provide improved support and protection to the rapidly rotating cable  40 , and small enough (e.g. closely surrounding the cable  40 ) to allow the first sheath  50  to freely move proximally and distally along the third sheath  80  and within the second sheath  60 . For example, if the cable  40  is 0.018 inches in diameter, the third sheath  80  may be 0.031 inches in diameter. In one representative example embodiment, polymer tubing such as polyetheretherketone (PEEK) tubing or 0.035″×0.031″ MicroLumen™ Polyimide tubing is used to form the third sheath  80 .  
         [0027]     Turning to FIGS.  2 A-B, side views of the two telescoping components of the improved telescoping catheter  10  are shown. In  FIG. 2A , the cable  40  extends distally through the receptacle  75 , past the detent  65 , and onwards through the hub  30  and out to the distal end of the catheter  10 . The third sheath  80  forms a lumen for the cable  40 , and extends proximally from the distal end of the hub  30  (or an attachment luer) through the hub  30 , through the receptacle  75 , past the detent  65  and into the open distal end of the first sheath  50 , terminating within the lumen formed by the first sheath  50 . The second sheath  60 , including the attached receptacle  75 , begins where the second sheath  60  is attached to the hub  30 , and extends proximally along the cable  40  and third sheath  80 , ending with the receptacle  75  attached to the proximal end of the second sheath  60 . The space between the second sheath  60  and the third sheath  80 , which allows the passage of the flared end  70  of the first sheath  50 , can be seen in this view.  
         [0028]     In  FIG. 2B , the cable  40  extends distally from the proximal end  20  of the catheter  10 , and onwards towards the distal end of the catheter  10 . The first sheath  50  is attached to the proximal end  20  of the catheter  10  and extends distally along the cable  40 , towards the distal end of the catheter  10 . The first sheath  50  also forms a lumen for the cable  40 . The increased diameter of the flared end  70  of the first sheath  50  can be seen in this view.  
         [0029]      FIG. 3  depicts a side view of the two telescoping components of the improved catheter  10 , with the catheter being partially extended. The third sheath  80  extends from the hub  30  along the inside of the lumen formed by the second sheath  60  and into the lumen formed by the first sheath  50 . The second sheath  60  extends from the receptacle  75  to the hub  30 , surrounding the distal portion of the first sheath  50  and the proximal portion of the third sheath  80 . The first sheath  50  extends from the proximal end  20  into the receptacle  75  and terminates at the flared end  70  within the lumen formed by the second sheath  60 . The flared end  70  of the first sheath  50  can pass freely along the catheter  10  between the second sheath  60  and the third sheath  80 .  
         [0030]      FIG. 4  depicts a side view of the two telescoping components of the improved catheter  10 , with the catheter  10  being fully extended. The first sheath  50  is fully retracted from within the second sheath  60 , and the flared end  70 , having slid proximally within the second sheath  60 , abuts the detent  65  within the receptacle  75 . The cable  40  is protected and supported by the third sheath  80  from any undesirable movement within the second sheath  60 . Because of third sheath  80 , the rapidly rotating cable  40  is not left unsupported and unprotected within the large inner lumen of second sheath  60 .  
         [0031]      FIG. 5  depicts a cross section of improved catheter  10  taken at the line A-A′ of  FIG. 3 . The outermost layer of the cross-section is the second sheath  60 . Within the second sheath  60  is the first sheath  50 , and then the third sheath  80 , and finally the cable  40 . The space between the second sheath  60  and the first sheath  50  is to allow for the flared end  70  to pass along the catheter  10  when the telescoping portion of the catheter  10  is being extended or retracted.  
         [0032]     Turning now to  FIG. 6 , an optional spacer  90  may be used to attach the third sheath  80  to the distal end of the hub  30 . The spacer  90  includes four radially-spaced lumens  92 ,  93 ,  94 , and  95 , a central lumen  96 , and an external surface  97 . These radially-spaced lumens allow for the free flow of matter through the spacer  90  while allowing the spacer  90  to provide a convenient attachment point for the third sheath  80 . Thus, the catheter  10  may be flushed with liquids while still providing support and protection for the cable  40 .  
         [0033]     The distal end of the third sheath  80  is attached to the inside of the central lumen  96 , and the spacer  90  is then attached to the distal end of the hub  30  by attaching the external surface  97  of the spacer  90  to the inside of the distal end of the hub  30 . These attachments may be made in a variety of ways, including, for example, a frictional engagement between the third sheath  80  and the spacer  90 , or between the spacer  90  and the hub  30 . Alternatively as another example, a glue or adhesive may be used to affix the third sheath  80  to the spacer  90  or the spacer  90  to the hub  30 .  
         [0034]     Turning to  FIG. 7 , the distal telescoping component of the improved catheter  10  is shown, without the cable  40 . The spacer  90  has been inserted into the distal end of the hub  30 , and the distal end of the third sheath  80  has been attached to the inside of the central lumen  96  of the spacer  90 , thus allowing the free flow of matter along the interior of the catheter  10 , while allowing the third sheath  80  to provide support and protection for the cable  40 .  
         [0035]     In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. For example, the orientation of the various sheaths could be reversed, such that the first sheath is attached to the hub, and the second and third sheaths are attached to the proximal end of the catheter. The telescoping relationship would be preserved, but the outermost second sheath and innermost third sheath would be proximal to the first sheath rather than distal to the first sheath. The sheaths could have cross-sections other than circular, such as elliptical, triangular or some other shape. The cable could be replaced by some other structure in need of being supported and protected, such as a wire or fiber optic channel for delivering electricity or light, including laser light, to the distal end of the catheter. Further, other additional features such as a balloon, stent, drug delivery system, sensor for a medical positioning system, and other features known to those of skill in the art of medical devices may be included as desired. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense, and the invention is not to be restricted or limited except in accordance with the following claims and their legal equivalents.