Patent Publication Number: US-2005131344-A1

Title: Low-profile valve contained within a catheter lumen

Description:
TECHNICAL FIELD  
      This invention relates generally to biomedical devices that are used for treating vascular conditions. More specifically, the invention relates to a low-profile catheter valve that is contained within the central lumen of a catheter used as a guidewire.  
     BACKGROUND OF THE INVENTION  
      Guidewires are conventionally used to guide medical instruments to a desired treatment location within a patient&#39;s vasculature. In a typical procedure, the clinician forms an access point for the guidewire by creating an opening in a peripheral blood vessel, such as the femoral artery. The highly flexible guidewire is then introduced through the opening and is advanced by the clinician through the patient&#39;s blood vessels until the guidewire extends across a vessel segment to be treated. A treatment catheter, such as a balloon catheter for a percutaneous transluminal coronary angioplasty (PTCA), may then be inserted over the guidewire and similarly advanced through vasculature until it reaches the treatment site.  
      In certain treatment procedures, it is desirable to serially advance and withdraw a number of different treatment catheters over a single guidewire that has been placed in a particular location. Typically, a first treatment catheter is advanced over the guidewire, withdrawn, and then fully removed from the portion of the guidewire that extends out of the patient&#39;s vessel. The guidewire is then available to act as a guide for a different treatment catheter.  
      It is sometimes advantageous to equip the distal end of a guidewire with at least one inflatable balloon, either to provide temporary occlusion of a vessel or to anchor the guidewire within a vessel. Anchoring the guidewire helps to prevent the guidewire from being displaced from its position while treatment catheters are advanced or withdrawn over the placed guidewire. An occlusion guidewire can be used as “distal protection” to prevent debris generated during vessel treatment from moving with the flowing blood to embolize distally.  
      A permanent inflation manifold, of the type used with conventional catheters having an inflatable balloon, would prevent treatment catheters from being exchanged one for another over an occlusion guidewire. Therefore, a removable inflation manifold and a valve to maintain the balloon in the inflated state are desirable for an occlusion guidewire. U.S. Pat. No. 5,167,239 to Cohen et al. discloses one such device. However, the valve apparatus used by the Cohen device is relatively bulky, having an outer diameter in its preferred embodiment of 0.0355 inches. As can be readily appreciated, the diameter of the valve on a guidewire dictates the inner diameter and, consequently, the outer diameter of a treatment catheter introduced over the valve. Therefore, it would be desirable to provide a low-profile catheter valve that overcomes the aforementioned and other disadvantages.  
     SUMMARY OF THE INVENTION  
      One aspect of the present invention is a low-profile catheter valve, comprising a catheter, an elastomeric plug, and a hollow stem. The catheter has at least one stop extending into the central lumen of the catheter adjacent to the catheter&#39;s proximal end. At least a portion of the elastomeric plug is received within the central lumen of the catheter and seated against the stop. The hollow stem is slidably received within the central lumen of the catheter.  
      The elastomeric plug has a channel in fluid communication with the central lumen of the catheter. An axial force applied to the elastomeric plug via the stem compresses the plug and closes the channel. The stem is maintained in a position within the catheter by interference between the stem and the catheter.  
      Another aspect of the present invention is a system for treating a vascular condition, comprising a catheter, an elastomeric plug, a hollow stem, and an inflatable balloon. The catheter has at least one stop extending into the central lumen of the catheter adjacent to the catheter&#39;s proximal end. At least a portion of the elastomeric plug is received within the central lumen of the catheter and seated against the stop. The hollow stem is slidably received within the central lumen of the catheter. The balloon is operably attached to a distal portion of the catheter.  
      The elastomeric plug has a channel in fluid communication with the central lumen of the catheter that allows inflation or deflation of the balloon through the central lumen. An axial force applied to the elastomeric plug via the stem compresses the plug and closes the channel to maintain inflation of the balloon. The stem is maintained in a position within the catheter by interference between the stem and the catheter.  
      The aforementioned and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings, which are not to scale. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIGS. 1A and 1B  show longitudinal cross-sectional views of one embodiment of a low-profile catheter valve, in accordance with the present invention;  
       FIGS. 2A and 2B  show longitudinal cross-sectional views of another embodiment of a low-profile catheter valve, in accordance with the present invention;  
       FIG. 3  is a longitudinal cross-sectional view of an adaptor used to manipulate the low-profile catheter valve of  FIG. 1 , showing the adaptor in a first position; and  
       FIG. 4  is an illustration of one embodiment of a system for treating a vascular condition, in accordance with the present invention; 
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS  
      One aspect of the present invention is a low-profile catheter valve. One embodiment of the valve, in accordance with the present invention, is illustrated in  FIGS. 1A and 1B  at  100 . Valve  100  comprises catheter  110 , elastomeric plug  120 , and hollow stem  130 . Catheter  110  includes stop  112 , which extends into central lumen  114  of catheter  110 , and indentations  116 . Plug  120  has a bore running through the plug to form channel  122 , which is in fluid communication with central lumen  114 . A perforated plate, washer  126 , is also included in valve  100 .  
      In the present embodiment, catheter  110  is a hypotube made of a biocompatible material such as stainless steel or nitinol. Catheter  110  may be a hollow guidewire and may include an inflatable balloon (not shown) operably attached to a distal portion of the catheter. Where catheter  110  is to be used as a guidewire during a procedure such as a conventional percutaneous transluminal coronary angioplasty involving femoral artery access, catheter  110  may be about 120 centimeters to about 300 centimeters long, with a length of about 180 centimeters often being used. The outer diameter of the catheter may range from about 0.010 inches to 0.038 inches, and preferably is 0.014 inches or smaller when the catheter is to be used as a guidewire. Thus, the outer diameter of catheter  110  provides a close sliding fit for a treatment instrument such as an atherectomy catheter, an angioplasty catheter, or a stent delivery catheter, which is inserted over valve  100  and advanced through vasculature.  
      Catheter  110  has stop  112  adjacent to the catheter&#39;s proximal end, i.e., the end that remains outside of the patient during a treatment procedure. The stop in the present embodiment is a single annular indentation swaged into catheter  110  and extending into central lumen  114 . A series of crimped indentations spaced around the circumference of the catheter may also be used.  
      Elastomeric plug  120  is received within central lumen  114  of catheter  110  and is seated against stop  112 . Thus, plug  120  is positioned within the lumen between stop  112  and the proximal end of catheter  110 . Washer  126  is positioned between stop  112  and plug  120  to increase the surface area of the stop and improve the seating of plug  120  against stop  112 . Plug  120  includes channel  122 , which allows a fluid to pass through plug  120  into a distal portion of central lumen  114  when the plug is in an unstressed state as shown in  FIG. 1A .  
      A distal portion of hollow stem  130  is slidably received within central lumen  114  of catheter  110 . That is, stem  130  is passed into the proximal end of catheter  110  and seated against plug  120 .  FIG. 1A  shows valve  100  in an open configuration wherein stem  130  applies little or no axial force against plug  120  such that channel  122  remains in its normally open form. To close valve  100 , as shown in  FIG. 1B , stem  130  is advanced into central lumen  114  until stem  130  applies an axial force against plug  120 , axially compressing plug  120  against stop  112  and closing channel  122 . Plug  120  is fabricated using an appropriate biocompatible material such as a silicone elastomer. The material is chosen to be both compressible when an axial force is applied via stem  130  and resilient to allow plug  120  to resume its unstressed configuration when the force is withdrawn. If a material is chosen that has a tendency to adhere to itself such that channel  122  remains closed after the force is withdrawn, a coating may be applied to the wall of channel  122  to prevent adherence.  
      Stem  130  is maintained in position within catheter  110  by an interference fit between stem  130  and central lumen  114 . In the present embodiment, stem  130  is a nitinol or stainless steel hypotube having an outer diameter smaller than the diameter of central lumen  114 . Interference between stem  130  and catheter  110  is provided by indentations  116  formed in the external wall of catheter  110  and extending into central lumen  114 . These indentations contact the exterior of stem  130 , increasing the frictional force that must be overcome to move stem  130  within the lumen.  
      The frictional force between stem  130  and catheter  110  must be sufficient to ensure that valve  100  is held in a closed configuration. Once stem  130  has been advanced into central lumen  114  to apply axial force against plug  120  and close channel  122 , stem  130  is held in the closed position to maintain the axial force, thereby maintaining the plug in a compressed state and ensuring that valve  100  remains closed. That is, the frictional force between stem  130  and catheter  110  must be greater than the rebound force of elastomeric plug  120  plus any fluid pressure maintained within catheter  110  by plug  120 . The axial force on plug  120  is removed by withdrawing stem  130 , allowing plug  120  to resume its unstressed configuration with channel  122  open.  
      Where catheter  110  is to be used as a guidewire having an inflatable balloon at its distal end, channel  122  allows inflation or deflation of the balloon through central lumen  114 . An axial force applied to stem  130  to compress plug  120  closes channel  122  to maintain inflation.  
      Another embodiment of the low-profile catheter valve, in accordance with the present invention, is illustrated in  FIGS. 2A and 2B  at  200 . Valve  200  comprises catheter  210 , elastomeric plug  220 , and hollow stem  230 . Catheter  210  includes stop  212 , which extends into central lumen  214  of catheter  210 . Plug  220  has a bore running through the plug to form channel  222 , which is in fluid communication with central lumen  214 . A perforated plate, washer  236 , is also included in valve  200 .  
      In the present embodiment, catheter  210  comprises a stainless steel or nitinol hypotube. A cylindrical structure is bonded by a method such as welding or adhesive bonding to the interior wall of catheter  210 , extending into central lumen  214  to form stop  212 .  
      Plug  220  comprises an appropriate biocompatible elastomer that is compressed when an axial force is applied to the plug via stem  230 . Plug  220  is shown in an unstressed state in  FIG. 2A  with channel  222  open, and compressed in  FIG. 2B  with channel  222  closed. Washer  236  is positioned between plug  220  and stem  230  to increase the area of plug  220  to which the axial force is applied.  
      Stem  230  is maintained in position within catheter  210  by interference between the stem and the catheter. In the present embodiment, the interference between stem  230  and catheter  210  is provided by waves formed in stem  230 . The waves contact the walls of central lumen  214 , holding the stem in a desired position.  
      It will be apparent to one skilled in the art that interference between a stem and a catheter may be provided in a wide variety of ways, including varying the shape or size of either or both of the catheter and the stem, or by forming a variety of patterns of indentations in the external wall of the catheter. Indentations or other structures in the catheter and the stem may also be designed to interlock to provide the desired interference.  
      An adaptor may be used to apply and withdraw the axial force.  FIG. 3  illustrates at  300  one embodiment of an adaptor in accordance with the present invention. The valve of  FIGS. 1A and 1B  is shown in place in the adaptor, with like elements sharing like numbers in  FIGS. 1A and 1B  and  FIG. 3 .  
      Adaptor  300  is shown removably mounted about a proximal portion of catheter  110 . Adaptor  300  is movable between a first position in which hollow stem  130  applies an axial force to plug  120  and a second position in which the force is withdrawn. The adaptor is in fluid communication with a fluid delivery device through opening  340 . Seal  350  engages the circumference of catheter  110  to establish a fluid-tight chamber surrounding the proximal end of catheter  110 . Additional seals and gaskets may be used to ensure that the adaptor itself is fluid tight, especially around switch  360 .  
       FIG. 3  shows adaptor  300  in the first position, with an axial force applied to plug  120  via stem  130 . The axial force is supplied by means of switch  360 , which includes rack  362  and internal wheel  364 . Wheel  364  is in contact with a portion of stem  130  that extends beyond the proximal end of catheter  110 . The wheel is fabricated using a material having a high coefficient of friction to engage the outer surface of stem  130  and communicate the axial force from switch  360  to stem  130 .  
      Moving switch  360 , and thereby rack  362 , in the direction of the proximal end of catheter  110  rotates wheel  364  counterclockwise, providing a forward motion to stem  130  that compresses plug  120  and closes channel  122 . The amount of axial force applied to plug  120  is predetermined by the axial freedom of movement of switch  360 . Stem  130  is maintained in position by interference between the stem and the catheter. Thus, once stem  130  has been advanced to compress plug  120  and close channel  122 , stem  130  is retained in the closed position, thereby maintaining plug  120  in a compressed state and ensuring that channel  122  remains closed. Adaptor  300  may then be removed to allow a treatment instrument to be advanced over catheter  110 .  
      To reopen channel  122 , adaptor  300  is again removably mounted about a proximal portion of catheter  110 , and the direction of switch  360  is reversed, thereby providing a reverse motion to stem  130  that withdraws the axial compression force and allows plug  120  to resume its unstressed state with channel  122  open.  
       FIG. 3  shows just one example of an adaptor that may be used to operate valve  100 . One skilled in the art will recognize that a wide variety of adaptors are appropriate for operating valve  100 , valve  200 , and other embodiments of a low-profile valve in accordance with the present of the invention.  
      Another aspect of the present invention is a system for treating a vascular condition. One embodiment of the system, in accordance with the present invention, is illustrated in  FIG. 4  at  400 . System  400  comprises catheter  410 , elastomeric plug  420 , hollow stem  430 , and inflatable balloon  440 . Catheter  410  includes stop  412 , which extends into central lumen  414  of catheter  410 . Plug  420  has a bore running through the plug to form channel  422 , which is in fluid communication with central lumen  414 .  
      In the present embodiment, catheter  410  is a hollow guidewire comprising a hypotube made of a biocompatible material such as stainless steel or nitinol. Where catheter  410  is to be used as a guidewire for other catheters in a conventional percutaneous transluminal coronary angioplasty procedure involving femoral artery access, catheter  410  may be about  120  centimeters to about 300 centimeters long, with a length of about 180 centimeters often being used. The outer diameter of the catheter may range from about 0.010 inches to 0.038 inches, and preferably is 0.014 inches in outer diameter or smaller when used as a guidewire for other catheters. Thus, the outer diameter of catheter  410  provides a close sliding fit for a treatment instrument such as an atherectomy catheter, an angioplasty catheter, or a stent delivery catheter, which is inserted over system  400  and advanced through vasculature.  
      Catheter  410  has stop  412  extending into central lumen  414  adjacent to the catheter&#39;s proximal end, i.e., the end that remains outside of the patient during a treatment procedure. The stop in the present embodiment is an annular indentation swaged into catheter  410  and extending into central lumen  414 . In an alternative embodiment, stop  412  may comprise multiple individual indentations or one or more structures bonded to the interior wall of the catheter.  
      Elastomeric plug  420  is received within central lumen  414  of catheter  410  and is seated against stop  412 . Thus, plug  420  is positioned within the lumen between stop  412  and the proximal end of catheter  410 . Hollow stem  430  is slidably received within central lumen  414  of catheter  410  and positioned against plug  420 .  
      In the present embodiment, stem  430  is a nitinol or stainless steel hypotube having an outer diameter smaller than the inner diameter of catheter  410 . When stem  430  is advanced within central lumen  414 , the stem applies an axial force to compress plug  420  against stop  412 , thus closing channel  422 . Perforated plates (not shown) may be positioned between stop  412  and plug  420  and between plug  420  and stem  430 , the first plate increasing the surface area of the stop and improving the seating of plug  420  against stop  412  and the second plate increasing the area of plug  420  to which the axial force is applied.  
      Plug  420  is fabricated using an appropriate biocompatible material such as a silicone elastomer. The material is chosen to be both compressible when an axial force is applied via stem  430  and resilient to allow plug  420  to resume its unstressed configuration when the force is withdrawn. If a material is chosen that has a tendency to adhere to itself such that channel  422  remains closed after the force is withdrawn, a coating may be applied to the wall of channel  422  to prevent adherence.  
      Stem  430  is maintained in position within catheter  410  by interference between the stem and the catheter. Interference between stem  430  and catheter  410  is provided by indentations formed in the external wall of catheter  410  and extending into the central lumen. These indentations contact the exterior of stem  430 , increasing the frictional force that must be overcome to move stem  430  within the lumen. It will be apparent to one skilled in the art that interference between a stem and a catheter may be provided in a wide variety of ways. For example, a single annular indentation may be formed in the external wall of the catheter, the indentation extending into the central lumen of the catheter. Alternatively, a variety of catheter and stem shapes and sizes may be used to achieve interference between the catheter and stem.  
      The frictional force between stem  430  and catheter  410  must be sufficient to ensure that the valve is held in a closed configuration. Once stem  430  has been advanced into central lumen  414  to apply axial force against plug  420  and close channel  422 , stem  430  is held in the closed position to maintain the axial force, thereby maintaining the plug in a compressed state and ensuring that the valve remains closed. That is, the frictional force between stem  430  and catheter  410  must be greater than the rebound force of elastomeric plug  420  plus any fluid pressure maintained within catheter  410  by plug  420 . The axial force on plug  420  is removed by withdrawing stem  430 , allowing plug  420  to resume its unstressed configuration with channel  422  open.  
      Inflatable balloon  440  is operably attached to a distal portion of catheter  410 . Inflatable balloon  440  may be made of a suitable material such as thermoplastic polyurethane (TPU) resins, styrene-ethylene-butadiene-styrene (SEBS), PEBAX, or the like. Channel  422  allows inflation of the balloon through central lumen  414 . Inflation is maintained when an axial force is applied to stem  430  to compress plug  420  and close channel  422 . Withdrawing the axial force allows plug  420  to resume its unstressed configuration with channel  422  reopened to permit deflation of balloon  440 .  
      The system as depicted may be operated using an adaptor such as that shown in  FIG. 3 . The adaptor may be removably mounted about a proximal portion of catheter  410 . The adaptor has a seal to engage the circumference of catheter  410 . Engaging the seal establishes a fluid-tight chamber surrounding the proximal end of catheter  410 . The adaptor is movable between a first position in which hollow stem  430  applies an axial force to plug  420  and a second position in which the force is withdrawn. The adaptor is in fluid communication with a fluid delivery device and has a seal to engage the circumference of catheter  410 . When engaged, the seal establishes a fluid-tight chamber surrounding the proximal end of catheter  410 . Additional seals and gaskets may be used to ensure that the adaptor itself is fluid tight. Mechanical stops or other means may be provided to ensure the adaptor applies a predetermined axial force.  
      Although described above in the context of an occlusion guidewire, system  400  may be readily adapted to a wide variety of balloon catheters, including those having additional functionalities, structures, or intended uses.  
      While the embodiments of the invention disclosed herein are presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated in the appended claims, and all changes and modifications that come within the meaning and range of equivalents are intended to be embraced therein.