Abstract:
Inventive catheters are disclosed which employ a variety of devices for preventing unwanted motion of the catheter tip. These methods include the use of a slidably mounted annular shim located in the tip of the catheter which may frictionally engage the guidewire element, and an annular brush with bristles. In the later case, the extent of the frictional engagement between the tip and the guidewire is determined by the orientation of the bristles. The present invention is also directed to a catheter in which unwanted motion is prevented by the presence of a tension/compression cable extending from the proximal end of the catheter shaft to the distal end of the catheter shaft. In the unlocked position, the tension/compression cable has slack in it while in the engaged position, the cable is either under tension or under compression.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional application from U.S. application Ser. No. 09/105,321, filed Jun. 26, 1998, now U.S. Pat. No. 6,117,140 the contents of which is hereby incorporated by reference 
    
    
     BACKGROUND OF THE INVENTION 
     In the treatment of diseases of the cardiovascular system, a variety of treatment devices are delivered by a catheter to a desired location in a bodily vessel. These treatment devices include balloons, stents and optical fibers carrying laser light. 
     In typical PTCA procedures, a guiding catheter is percutaneously introduced into the cardiovascular system of a patient and advanced through the aorta until the distal end is in the ostium of the desired coronary artery. Using fluoroscopy, a guide wire is then advanced through the guiding catheter and across the site to be treated in the coronary artery. An over the wire (OTW) balloon catheter is advanced over the guide wire to the treatment site. The balloon is then expanded to reopen the artery. The OTW catheter may have a guide wire lumen which is as long as the catheter or it may be a rapid exchange catheter wherein the guide wire lumen is substantially shorter than the catheter. Alternatively, a fixed wire balloon may be used. This device features a guide wire which is affixed to the catheter and cannot be removed. 
     To help prevent arterial closure, repair dissection, or prevent restenosis, a physician can implant an intravascular prosthesis, or a stent, for maintaining vascular patency inside the artery at the lesion. The stent may either be a self-expanding stent or a balloon expandable stent. For the latter type, the stent is often delivered on a balloon and the balloon is used to expand the stent. The self-expanding stents may be made of shape memory materials such as nitinol or constructed of regular metals but of a design which exhibits self expansion characteristics. 
     Catheters are also used to deliver optical fibers carrying laser light to provide controlled delivery of a laser beam for treatment of atherosclerotic disease. 
     It is often desirable to provide a retractable sheath as a cover over a treatment device until the treatment device is positioned. At that point, the retractable sheath is removed and the treatment device delivered to the desired location. 
     Consequently, as the retractable sheath of a catheter is retracted to allow for deployment of a stent or other treatment device, the tip of the catheter has a tendency to move. In particular, where the catheter traverses a twisted, curved pathway, a portion of the catheter, including the tip, upon retraction of the sheath, will have a tendency to move either to the inside of the curve or to the outside of the curve from its position in the center of the pathway resulting in the tip moving forward. This movement of the tip can complicate the precise deployment of a stent or other treatment device as the practitioner cannot be certain of the exact location of the catheter tip as the treatment device is deployed. 
     In an effort to address this difficulty, the present invention is directed toward a catheter in which the movement of the tip associated with retraction of the catheter is eliminated via a locking means. Two principal approaches are used to accomplish this goal. In one approach, the guidewire is locked to the tip prior to retraction of the sheath. In the other approach, the catheter shaft exhibits a controllable variable flexibility. Motion of the tip is prevented by increasing the rigidity of the catheter prior to retraction of the sheath. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is a catheter in which undesired motion may be reduced or eliminated. Such a catheter is embodied by a lockable treatment device delivery catheter comprising an inner tube, a guidewire element carried within the inner tube and extending from the proximal end of the inner tube to the distal end of the inner tube, a tip mounted over the inner tube at the distal end of the inner tube and a motion arresting device frictionally engaging the tip of the catheter with the guidewire to prevent proximal and/or distal motion of the tip when engaged. 
     Several specific embodiments of the motion arresting device including a shim slidably mounted within the tip and a brush mounted within the tip are disclosed. In both cases, the motion arresting device is mounted concentrically about the guidewire element. In the former case, the shim is slidably mounted so that when in use the shim slides from a region of the tip with a larger inner diameter to a region with a lower inner diameter, thereby applying an inward force to the shim which then frictionally engages the proximal region of the tip and the guide wire, fixing one to the other. In the latter case, an annular brush having bristles directed radially inward is mounted concentrically over the guidewire. As the guidewire is moved relative to the bristles, the orientation of the bristles changes (either from proximal to distal or vice versa). As the bristles reorient, the force required to continue the reorientation increases to the point where the guidewire is effectively locked to the tip. 
     In another embodiment, the invention provides a variably flexible catheter. The variable flexibility is achieved by the inclusion of a tension-compression cable in the catheter. The tension-compression cable is anchored at the distal end of the catheter and preferably in a retractable sheath, where present. Increased rigidity is achieved by placing the tension-compression either in tension or in compression from a relaxed state. This increased rigidity may be exploited to prevent undesired motion of the catheter tip. 
     The present invention is also directed to a method of delivering a treatment device such as a stent to a desired bodily location using the inventive devices. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 show a longitudinal cross-section of an inventive catheter. 
     FIG. 2 a  shows an enlarged view of the circled region  2  of the catheter in FIG.  1 . 
     FIG. 2 b  show a further enlarged schematic of FIG. 2 a.    
     FIG. 3 shows an enlarged view of the circled region  3  of the catheter in FIG.  1 . 
     FIG. 4 shows the shim in longitudinal cross-sectional view. 
     FIG. 5 shows the shim of FIG. 4 in transverse cross-sectional view along line  5 — 5 . 
     FIG. 6 shows the shim of FIG. 4 in perspective view. 
     FIG. 7 shows an enlarged view of the circled region  7  of the catheter in FIG.  1 . 
     FIG. 8 is a schematic drawing of the tip of the catheter of FIG. 1 with the motion arresting device engaged. 
     FIG. 9 shows another embodiment of the inventive catheter. 
     FIG. 10 shows an enlarged longitudinal cross-section view of the circled region  10  of the catheter in FIG. 9 with the brush in the unlocked position. 
     FIG. 11 shows a perspective, cross-sectional view of the brush used in the catheter of FIG.  9 . 
     FIG. 12 shows a schematic cross-sectional view of the tip of the catheter of FIG. 9 with the bristles of the brush in the locked position. 
     FIG. 13 shows another embodiment of the inventive catheter. 
     FIG. 14 shows an enlarged view of the circled region  14  of the catheter in FIG.  13 . 
     FIG. 15 shows an enlarged view of a portion of the distal end of another embodiment of the inventive catheter. 
     FIG. 16 shows a catheter in rapid exchange form. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While this invention may be embodied in many different forms, there are described in detail herein specific preferred embodiments of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. 
     FIG. 1 shows a longitudinal cross-section of an inventive catheter generally at  110  having proximal  111  and distal  112  ends. The catheter comprises an inner tube  114  having a proximal end  118  and a distal end  122 . Carried within inner tube  114  is a guidewire element  126 , which is shown in FIGS. 2 a,b . Guidewire element  126  extends beyond distal end  122  of inner tube  114 . Catheter  110  further comprises a tip  130  mounted over distal end  122  of inner tube  114 . Tip  130  has a proximal region  134  and a intermediate region  138  distal to and adjacent to proximal region  134 . The inner diameter of intermediate region  138  exceeds the inner diameter of proximal region  134  of tip  130  and the inner diameter of distal region  135  of the tip so as to accommodate a motion arresting device  142 . Motion arresting device  142  frictionally engages tip  130  with guidewire element  126  to prevent proximal and/or distal motion of the tip when engaged. As shown in FIGS. 1,  2   a,b  and  4 - 8 , motion arresting device  142  is a tapered shim  142  slidably mounted in tip  130 . Shim  142  is controlled by a shim pullwire  146  attached thereto extending to a shim actuator  148  at proximal end  111  of catheter  110 . Shim  142  is shown in longitudinal cross-sectional view in FIG.  4  and in transverse cross-sectional view along line  5 — 5  in FIG.  5 . Shim  142  is further shown in perspective view in FIG.  6 . As seen in the figures, shim  142  is preferably in the form of a collet with fingers  144 . As seen in FIG. 1, shim  142  is not in contact with guidewire element  126  and as such, the shim is not engaged. 
     As shown in FIG. 1, catheter  110  further comprises an optional proximal catheter shaft  150  having a proximal end  154  and a distal end  158 . Inner tube  114  is carried within proximal catheter shaft  150  and extends beyond distal end  158  of proximal catheter shaft  150 . Also shown in FIG. 1 is an optional treatment delivery device, in this case a stent  162 , mounted over distal end  122  of inner tube  114 . Shown covering stent  162  is an optional retractable sheath  166  slidably mounted on distal catheter shaft  194 . Retractable sheath  166  is retractable from a fully extended position (as shown) in which the treatment device, stent  162 , is covered by the retractable sheath and a fully retracted position (not shown) in which the treatment device, stent  162 , is exposed. As seen in FIG. 1, tip  130  abuts retractable sheath  166 , in the fully extended position. Retractable sheath  166  may be retracted by pulling on sheath pullwire  169  which is attached to pull collar  167  which, in turn, is attached to retractable sheath  166 . Sheath pullwire  169  extends to the proximal end of the catheter. 
     At the proximal end of the catheter is an optional manifold structure, shown generally at  180 , with slide mechanism  182  as is known in the art. Slide mechanism  182  is connected to sheath pullwire  169  in a known manner for retracting sheath  166  by moving the slide mechanism. 
     Also shown in FIG. 1 are marker band  164  and bumper  170  as are known in the art. 
     In use, tip  130  is locked to guidewire element  126  by pulling shim pullwire  146  proximally thereby sliding shim  142  in a proximal direction. While shim  142  is in intermediate region  138  of tip  130 , it slides freely because the inner diameter of the tip in the intermediate region exceeds the outer diameter of the shim. As shim  142  enters proximal region  134 , the shim becomes wedged therein because the maximum outer diameter of the tip exceeds the inner diameter of the proximal region of the tip as shown in FIG.  5 . 
     The shim should be flexible enough to deform inward. The shim may be made of a flexible material which can deform inward so as to engage the guidewire element. The material may be flexible. Alternatively, the shim may be made of a rigid material which is constructed and arranged to collapse inward. An example of the latter is a collet. The tip, however, must be rigid, relative to the shim. Suitable materials from which the shim may be made include olefinics, polyurethanes, polyesters, styrenics and polyamides and combinations thereof. 
     Shim pullwire  146  may be welded to the shim or alternatively, may be heat welded to the plastic where the shim is formed of plastic or may be adhesively bonded to the shim or otherwise connected thereto. 
     Guidewire element  126  may consist solely of a guidewire or may comprise a guidewire as well as a guidewire sheath or tube in which the guidewire is carried. Where the guidewire element has a protective sheath bonded or otherwise affixed to the guidewire and the sheath and guidewire slide in unison, the shim will simultaneously engage the guidewire and sheath. Where, on the other hand, the guidewire element comprises a guidewire slidably carried within the lumen of a tube, the tube must be deformable inward so that the shim may engage the guidewire through the tube. 
     In the embodiment of FIG. 1, as shown in FIG. 7, the catheter further comprises an accordion assembly  190  extending from the distal end  158  of proximal catheter shaft  150  to the proximal end  192  of distal catheter shaft  194 . 
     In another embodiment of the invention, as shown in FIGS. 9-12, catheter  210  having proximal  211  and distal  212  ends comprises an inner tube  214  having a proximal end  218  and a distal end  222 . Carried within inner tube  214  is a guidewire element  226 . Guidewire element  226  extends beyond distal end  222  of inner tube  214 . Catheter  210  further comprises a tip  230  mounted over distal end  222  of inner tube  214 . Catheter  210  further comprises a motion arresting device  242  frictionally engaging tip  230  with guidewire element  226  to prevent proximal and/or distal motion of the tip when engaged. As shown in FIG. 10, an expanded view of the circled region in FIG. 9, motion arresting device  242  comprises a an annular brush  244  therein, the brush having bristles  245 . Annular brush  244  is mounted within tip  230  concentrically about guidewire element  226 . Bristles  245  extend from brush  244  to guidewire element  226  and frictionally engage at least a portion of the guidewire element. A cross-sectional perspective view of brush  244  with bristles  245  is shown in FIG.  11 . 
     As shown in FIG. 9, catheter  210  further comprises an optional catheter shaft  250  having a proximal end  254  and a distal end  258 . Inner tube  214  is carried within catheter shaft  250  and extends beyond distal end  258  of catheter shaft  250 . Also shown in FIG. 8 is an optional treatment delivery device, a stent  262 , mounted over distal end  222  of inner tube  214 . Shown covering stent  262  is an optional retractable sheath  266  mounted on distal end  258  of catheter shaft  250 . Retractable sheath  266  is retractable from a fully extended position (as shown) in which the treatment device, stent  262 , is covered by the retractable sheath and a fully retracted position in which the treatment device, stent  262 , is exposed. As seen in FIG. 9, tip  230  abuts retractable sheath  266 , in the fully extended position. 
     At the proximal end of the catheter is a manifold structure  280  with slide mechanism  282  as is known in the art. Slide mechanism  282  is connected to a pull wire (not shown) similar to sheath pullwire  169  shown in FIG. 3 in a known manner for retracting sheath  266  by moving the slide proximally. 
     In order to more fully understand the operation of the motion arresting device, brush  244  is shown in a perspective cut-away view in FIG.  11 . Bristles  245  are more clearly seen to extend from the brush inward. A schematic drawing of tip  230  is shown in FIG. 12 in which bristles  245 , engaging guidewire element  226  are shown oriented in the proximal direction. As long as guidewire  226  is moved in a proximal direction relative to the rest of the catheter, guidewire element  226  will meet a fixed resistance from the brush. When it is desired to lock guidewire element  226  in place, the motion of guidewire element  226  is reversed relative to the catheter at which point bristles  245  begin to reorient, as shown in FIG. 10 thereby resulting in an increased resistance to motion resulting from the interaction of the bristles with the guidewire element thereby locking the guidewire to the tip. Note that FIG. 10 does not represent a locked position, but rather an intermediate position. Of course, if enough force is applied to the guidewire element, the guidewire and tip may be unlocked with the orientation of the bristles reversing entirely so as to be facing in the distal direction at which point, the guidewire element will face a constant, but reduced resistance to distal motion, thereby disengaging the tip from the guidewire element. The guidewire element may again be locked by again reversing the direction of motion of the guidewire element so as to partially reorient the bristles. In a more general way, when the bristles are oriented proximally, the guidewire may be moved with little resistance in the proximal direction but will be more resistant to motion in the distal direction. Similarly, when the bristles are oriented distally, the guidewire may be moved freely in the distal direction but will be resistant to motion in the proximal direction. In each case, a larger force will be required to initiate motion of the guidewire in a direction opposite the orientation of the bristles than to initiate motion in the direction in which the bristles are oriented. 
     While the bristles shown in FIG. 11 are annular elements whose thickness tapers from the outer radius of the annulus to the inner radius, the brushes need not be tapered inward and may consist of a series of spaced annuli of uniform thickness. Moreover, the bristles need not be annular but may rather consist of a series of flexible elements extending inward from the interior surface of the tip. 
     Brush  244  and bristles  245  may be made of suitable materials including olefinics, polyurethanes, polyesters, styrenics, polyamides and combinations thereof. Most importantly, it is desirable that the bristles not be made of a material which will scratch, nick or otherwise mar guidewire element  226 . 
     As in the previous embodiment, guidewire element  226  may consist isolely of a guidewire or may further comprise a protective guidewire sheath. Where the guidewire element has a protective sheath bonded or otherwise affixed to the guidewire and the sheath and guidewire slide in unison, the shim will simultaneously engage the guidewire and sheath. 
     Another embodiment of the invention is shown in FIG. 13. A lockable treatment device delivery catheter, shown generally at  310 , comprises an inner tube  314  having proximal  318  and distal  322  ends. Inner tube is carried in a catheter shaft  350  having proximal  354  and distal  358  ends, and extends beyond the distal end of the catheter shaft. The catheter further comprises a guidewire element (not shown) carried within inner tube  314  and extending from proximal end  318  of inner tube  314  to distal end  322  of inner tube  314 . Mounted over inner tube  314  at distal end  322  of inner tube  314  is a tip  330 . A retractable sheath  366  having proximal  367  and distal  368  ends is slidably mounted on distal catheter shaft  394  retracting from a fully extended position in which a treatment device  362  (shown here as a stent) is covered by the retractable sheath and a fully retracted position in which treatment device  362  is exposed. Retractable sheath  366  may be retracted by pulling on sheath pullwire  369  which is attached to pull collar  365  which, in turn, is attached to retractable sheath  366 . Sheath pullwire  369  extends to the proximal end of the catheter. Tip  330  abuts retractable sheath  366  in the fully extended position. 
     Finally, catheter  310  comprises a motion arresting device comprising a locking cable  342  extending from proximal end  354  of catheter shaft  350  to proximal end  367  of retractable sheath  366 . At least a portion of locking cable  342  is carried within catheter shaft  350 . As shown in FIG. 14, locking cable  342  is anchored in retractable sheath  366 , to bumper  370 . For the sake of clarity it should be noted that pullwire  369  and locking cable  342  appear to merge into one in FIG.  14 . This is an artifact of the figure. In reality, the two are separate and distinct. 
     Locking cable  342  may be alternatively anchored to any other suitable structure in the distal end of the catheter. FIG. 15 shows another embodiment of the distal end of a catheter identical to that shown in FIGS. 13 and 14 with the exception that locking cable  342  is anchored to positioning collar  343 . In either embodiment, prior to being engaged, locking cable  342  has some slack in it. 
     At the proximal end of the catheter is an optional manifold structure  380  with slide mechanism  382  as is known in the art. Slide mechanism  382  is connected to pullwire  369  in a known manner for retracting sheath  366  by moving the slide proximally. Also shown in FIGS. 14 and 15 are marker bands  364  as are known in the art. 
     In use, locking cable  342  may be engaged to prevent motion of tip  330  by placing the locking cable in tension or by placing the locking cable in compression thereby stiffening the catheter. Ideally, the application of the locking cable will occur as part of the final positioning of the catheter. The catheter may be unlocked by reducing the tension or compression of the cable. 
     While the locking cable may be made of any suitable material such as a metal, the material must be rigid enough so that it does not buckle when placed in compression if used as a compression cable. It is preferable that the locking cable be carried in a tube. Suitable materials for the locking cable include Nitinol and stainless steel. 
     The present invention is not intended to be limit to catheters as shown here in the figures. Other configurations of the catheter are also contemplated for use in conjunction with the present invention including catheters having full length sheaths such as in U.S. Pat. No. 4,875,480 to Imbert, catheters employing the collapsible sheath technique of U.S. Pat. No. 5,534,007 and PCT patent application PCT/US96/07143 and catheters having slidably sealed sheaths and midshaft seals as disclosed in U.S. patent application Ser. No. 08/722,834 filed Sep. 27, 1996, as well as U.S. patent application Ser. No. 09/071,484 filed May 1, 1998. The entire contents of the above-mentioned patents and patent applications are hereby incorporated in their entirety by reference herein. 
     Further, as shown above in the figures, the treatment device may be a stent. A variety of stents are suitable for use with the inventive catheters including self-expanding and balloon expandable stents. In the latter case, a balloon is mounted concentrically over the distal end of the inner tube and at least a portion of the stent mounted over the balloon and concentrically over the inner tube. In the case of the balloon expandable stent, the catheter will further comprise a suitable inflation shaft having a lumen therein for inflating the balloon. Such inflation shafts well known in the art. 
     Other treatment devices in addition to stents are contemplated including a balloon for angioplasty procedures and a laser for laser ablation procedures. 
     The present invention also provides a catheter of variable flexibility. The catheter comprises a catheter shaft having proximal and distal end, an inner tube having proximal and distal ends, extending from the proximal end of the catheter shaft and carried within the catheter shaft, a guidewire element carried within the inner tube and extending from the proximal end of the inner tube to the distal end of the inner tube and a tension-compression cable for altering the flexibility of the catheter, the tension-compression cable anchored to an anchoring element at the distal end of the catheter shaft, the tension-compression cable having a relaxed state in which no tension or compression is applied thereto. The catheter may be made more rigid by applying tension or compression to the cable in its relaxed state. Embodiments of the variably flexible catheter are shown in FIGS. 14 and 15. 
     The invention is also directed to a rapid exchange catheter with a motion arresting device. FIG. 16 shows a rapid exchange catheter generally at  410 . Catheter  410  includes a cather shaft  450  having a guidewire lumen  414  extending at least a portion of the way through the distal end of catheter shaft  450 . Guidewire lumen  414  terminates in a tip  430  located at its distal end. Tip  430  has an opening extending therethrough to accommodate a guidewire. Guidewire  426  enters catheter shaft  450  in guidewire lumen  414  and emerges through the opening in tip  430 . The tip of catheter  410  may be suitably modified to incorporate any of the tip-based motion arresting devices disclosed herein including the shim and the annular brush. 
     Catheter  410  is shown with a stent  462  disposed about guidewire lumen  414 . Stent  462  is covered by retractable sheath  466 . Retractable sheath  466  is affixed to pull collar  467 . Pull collar  467 , in turn, has a pull wire  469  extending proximally therefrom for retracting the sheath. 
     The above Examples and disclosure are intended to be illustrative and not exhaustive. These examples and description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims attached hereto.