Abstract:
A catheter for performing a procedure at a treatment site in the lumen of a blood vessel. The catheter includes an elongate tubular shaft having a proximal bend, a distal bend and a hinge element. A distal portion of the shaft includes a window extending through the sidewall of the shaft between the hinge element and the distal end of the elongate tubular shaft. A working element is disposed within the lumen of the elongate tubular shaft and is configured for performing the procedure through the window at the treatment site. The bends and hinge element are configured to urge the window against a wall of the vessel at the treatment site.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     The present invention claims priority to U.S. Ser. No. 12/578,204, filed Oct. 13, 2009, which claims priority to Provisional Application No. 61/122,601, filed on Dec. 15, 2008, and Provisional Application No. 61/104,836, filed on Oct. 13, 2008. The complete disclosure of each of the above-listed patent applications is hereby incorporated by reference for all purposes. 
    
    
     BACKGROUND 
     Atherectomy catheters are used to remove material from a blood vessel to open the lumen of the blood vessel and improve blood flow through the vessel. 
     Atherectomy catheters generally have cutters positioned at or near the distal end of the catheter. Some atherectomy catheters are designed to cut along only one portion of their distal circumference. Such ‘directional atherectomy’ catheters must be manipulated such that the cutter is positioned adjacent to the material to be cut. Such manipulation can involve urging the cutter against one side of a blood vessel so that material can be cut, and can involve rotating the proximal region of the catheter shaft so as cause rotation of the distal region of the catheter and thereby position the distally located directional cutter adjacent to material to be cut. 
     The present invention is directed to devices and methods for manipulating and urging a cutting element of an atherectomy catheter such that the cutter is positioned adjacent to the material to be cut. 
     SUMMARY 
     The present invention provides a manipulator which is used with an atherectomy catheter to rotate, translate, or both rotate and translate the catheter. The atherectomy catheter may have a cutting element that is able to extend through a window to cut material of interest. The manipulator can be actuated using one hand only. 
     In another aspect of the invention, an atherectomy catheter is provided with a pre-formed distal region. The pre-formed distal region urges the atherectomy catheter cutter into forcible contact with the inner wall of a vessel. When the cutting element encounters tissue, forces that tend to deflect the cutting element away from the tissue are resisted by the pre-formed distal region of the catheter. 
     In one aspect the invention is a catheter for performing a procedure at a treatment site in the lumen of a blood vessel, the blood vessel having a diameter D at the treatment site. The catheter comprises an elongate tubular shaft having distal and proximal ends and a sidewall defining a lumen, the elongate tubular shaft having a proximal bend, a distal bend and a hinge element, the proximal bend defining a first angle greater than zero, the distal bend defining a second angle greater than the first angle, the hinge element being spaced proximally of the distal end of the elongate tubular shaft and distally of the distal bend, the distal bend being positioned between the proximal bend and the hinge element, a distal portion of the elongate tubular shaft extending between the hinge element and the distal end of the elongate tubular shaft and a mid portion of the elongate tubular shaft extending between the hinge element and the proximal bend, the distal portion including a window extending through the sidewall between the hinge element and the distal end of the elongate tubular shaft. The catheter further includes a working element disposed within the lumen of the elongate tubular shaft, the working element configured for performing the procedure through the window at the treatment site, the first and second angles being selected to form a maximum excursion of the elongate tubular shaft between the proximal bend and the hinge element greater than diameter D such that the window is urged against a wall of the vessel at the treatment site. The proximal and distal bends may be configured to lie within a first plane and the hinge element may configured to permit bending of the distal portion with respect to the mid portion only in the first plane. The first and second angles may selected to urge the window against the wall of the vessel at a force in the range of about 0.05 to 0.5 pounds. The first angle may be in the range of about 90° to 150° and the second angle may be in the range of about 100° to 180°. A length from the proximal bend to the distal bend may be greater that a length from the distal bend to the hinged element. A length between the proximal and distal bends may be in the range of about 0.5 to 2.0 inches and a length between the distal bend and the hinge element may be in the range of about 0.375 to 0.625 inches. The maximum excursion may be in the range of about 3 to 40 mm. 
     In another aspect the invention is a catheter for performing a procedure at a treatment site in the lumen of a blood vessel. The catheter includes an elongate tubular shaft having distal and proximal ends and a sidewall defining a lumen, the elongate tubular shaft having a curved distal portion with a continuously decreasing radius of curvature, the continuously decreasing radius of curvature being oriented in a first plane from a proximal end of the distal portion to the distal end of the elongate tubular shaft, the distal portion including a hinge element spaced proximally of the distal end of the elongate tubular shaft, the hinge element dividing the distal portion into a distal segment between the hinge element and the distal end of the elongate tubular shaft and a proximal segment between the hinge element and the proximal end of the distal portion, the hinge element being configured to permit the distal segment to bend with respect to the proximal segment only in the first plane, the distal segment including a window extending through the sidewall between the hinge element and the distal end of the elongate tubular shaft. The catheter further includes a working element disposed within the lumen of the elongate tubular shaft, the working element configured for performing the procedure through the window at the treatment site, the continuously decreasing radius of curvature being selected to urge the window against a wall of the vessel at the treatment site during use. The curved distal portion may form a continuous curve in the range of about 90° to 720°. A maximum curve diameter of the curved distal portion may be in the range of about 3 mm to 50 mm. 
     In a further aspect the invention is a method of performing a procedure at a treatment site in the lumen of a blood vessel. The method comprises providing an elongate tubular shaft having distal and proximal ends and a sidewall defining a lumen, the elongate tubular shaft having a proximal bend, a distal bend and a hinge element, the proximal bend defining a first angle greater than zero, the distal bend defining a second angle greater than the first angle, the proximal and distal bends being oriented in a first direction, the hinge element being spaced proximally of the distal end of the elongate tubular shaft and distally of the distal bend, the distal bend being positioned between the proximal bend and the hinge element, a distal portion of the elongate tubular shaft extending between the hinge element and the distal end of the elongate tubular shaft and a mid portion of the elongate tubular shaft extending between the hinge element and the proximal bend, the distal portion including a window extending through the sidewall between the hinge element and the distal end of the elongate tubular shaft. The method farther includes advancing the elongate tubular shaft through the lumen of the vessel to the treatment site; orienting the elongate tubular shaft in a position where the proximal and distal bends cause the distal portion of the elongate tubular shaft to bend with respect to the mid portion of the elongate tubular shaft at the hinge element in a second direction opposite the first direction to urge the window against a wall of the vessel in a desired location at the treatment site; and performing a procedure through the window at the treatment site with a working element disposed within the lumen of the elongate tubular shaft while the window is urged against the wall of the vessel. The hinge element may be configured to permit bending of the distal portion with respect to the mid portion only in the first and second directions. 
     In a further aspect the invention is a method of performing a procedure at a treatment site in the lumen of a blood vessel comprising providing an elongate tubular shaft having distal and proximal ends and a sidewall defining a lumen, the elongate tubular shaft having a curved distal portion with a continuously decreasing radius of curvature, the continuously decreasing radius of curvature being oriented in a first direction from a proximal end of the distal portion to the distal end of the elongate tubular shaft, the distal portion including a hinge element spaced proximally of the distal end of the elongate tubular shaft, the hinge element dividing the distal portion into a distal segment between the hinge element and the distal end of the elongate tubular shaft and a proximal segment between the hinge element and the proximal end of the distal portion, the hinge element being configured to permit the distal segment to bend with respect to the proximal segment only in the first direction and a second direction opposite the first direction, the distal segment including a window extending through the sidewall between the hinge element and the distal end of the elongate tubular shaft. The method further includes advancing the elongate tubular shaft through the lumen of the vessel to the treatment site; orienting the elongate tubular shaft in a position where the continuously decreasing radius of curvature of the curved distal portion causes the distal segment to bend with respect to the proximal segment at the hinge element in the second direction to urge the window against a wall of the vessel in a desired location at the treatment site; and performing a procedure through the window at the treatment site with a working element disposed within the lumen of the elongate tubular shaft while the window is urged against the wall of the vessel. 
     In another aspect the invention is a device for manipulating the shaft of a catheter comprising a body portion having a lumen sized to receive the shaft of the catheter, and a shaft engaging member having first and second shaft engaging surfaces enclosed within the body portion, the shaft engaging member having a locked position in which the first and second shaft engaging surfaces are configured to engage the shaft to lock the body on the shaft and an unlocked position in which the body is free to rotate and axially translate over the elongate tubular shaft. The shaft engaging surfaces may be biased in either the locked or the unlocked position. 
     In a further aspect the invention is a catheter for accessing a site on the wall of a blood vessel. The catheter includes an elongate tubular shaft having distal and proximal ends and a sidewall defining a lumen, the elongate tubular shaft having a first bend, a second bend spaced a predetermined distance distally of the first bend and a window extending through the sidewall, the window being positioned distally of the second bend and proximally of the distal end of the elongate tubular member, the first bend defining a first angle greater than zero, the second bend defining a second angle greater than the first angle, the first and second angles and the predetermined distance being selected to urge the window against the site on the wall of the blood vessel during use. The elongate tubular shaft may further include a hinge element spaced proximally of the window and distally of the second bend. Further, the catheter may include a working element disposed within the lumen of the elongate tubular shaft, the working element configured for performing a procedure through the window at the site on the wall of the blood vessel. The elongate tubular shaft may include a distal portion between the hinge element and the distal end of the elongate tubular shaft and the hinge element may be configured as a pivot point about which the distal portion bends. Further, the distal portion may have a longitudinal axis and the hinge element may be configured such that when the window is urged against the site on the wall of the blood vessel during nest the distal portion is positioned such that the longitudinal axis of the distal portion is substantially parallel to a longitudinal axis of the blood vessel. 
     In another aspect the invention is a catheter for performing a procedure at a treatment site in the lumen of a blood vessel comprising an elongate tubular shaft having distal and proximal ends and a sidewall defining a lumen, the elongate tubular shaft having a proximal bend, a distal bend and a hinge element, the proximal bend defining a first angle greater than zero, the distal bend defining a second angle greater than the first angle, the hinge element being spaced proximally of the distal end of the elongate tubular shaft and distally of the distal bend, the distal bend being positioned between the proximal bend and the hinge element, a distal portion of the elongate tubular shaft extending between the hinge element and the distal end of the elongate tubular shaft and a mid portion of the elongate tubular shaft extending between the hinge element and the proximal bend, the distal portion including a window extending through the sidewall between the hinge element and the distal end of the elongate tubular shaft, the proximal bend, distal bend and hinge element being configured to urge the window against a wall of the vessel at the treatment site. The catheter may include a working element disposed within the lumen of the elongate tubular shaft, the working element configured for performing the procedure through the window at the treatment site when the window is urged against the wall of the blood vessel during use. 
     These and other aspects of the invention will become apparent from the following description of the preferred embodiments, drawings and claims. The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a schematic plan view of one embodiment of a shaft manipulator in accordance with principles of the present invention. 
         FIG. 1B  illustrates an isometric view of the shaft manipulator illustrated in  FIG. 1A . 
         FIGS. 1C and 1D  illustrate cross sectional views along line A-A of the shaft manipulator illustrated in  FIG. 1A . 
         FIG. 2A  illustrates a schematic plan view of another embodiment of a shaft manipulator in accordance with principles of the present invention. 
         FIG. 2B  illustrates an isometric view of the shaft manipulator illustrated in  FIG. 2A . 
         FIGS. 2C and 2D  illustrate cross sectional views along line A-A of the shaft manipulator illustrated in  FIG. 2A . 
         FIGS. 3A and 3B  illustrate schematic plan views of another embodiment of a shaft manipulator in accordance with principles of the present invention. 
         FIGS. 4A and 4B  illustrate schematic plan views of yet another embodiment of a catheter in accordance with principles of the present invention. 
         FIGS. 5A to 5C  illustrate schematic plan views of a further embodiment of a catheter in accordance with principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the embodiment of  FIGS. 1A to 1D , the present invention is directed to a device for manipulating a catheter shaft. The invention is described in connection with an atherectomy catheter but may be used with any other catheter. 
     The atherectomy catheter  20  has a working element  22  such as a cutting element. The cutting element may extend through a window  24  in a shaft  26  of the catheter. As can be appreciated, the working element can be any other element such as an RF element, a visualization element or an implant delivery element. Typically catheter  20  may have a working diameter of 3 Fr to 7 Fr and have a working length of 60 cm to 180 cm. 
     The orientation of the working element  22  may be manipulated by rotating the shaft  26  so that a handle  28  can remain stationary while the shaft is rotated. The shaft may be rotatable in increments or may be adjustable to any angular orientation. In some embodiments the shaft is coupled to the handle in a manner which permits rotation of the shaft relative to the handle upon application of a modest torque to the shall. In other embodiments the shaft is rotationally fixed to the handle in a manner which does not permit rotation of the shaft relative to the handle upon application of a modest torque to the shaft. 
     Shaft manipulator  10  is rotatably and slidably coupled to shaft  26  and configured for one-handed use. Manipulator  10  is comprised of body  12  having lumen  11 , buttons  14 , springs  16  and pivot pins  18 . Buttons  14  are further comprised of arms  14   c  having holes therein for pivot pins to slidably fit through. Body  12  and buttons  14  may be made from polycarbonate, nylon, or other materials and may be injection molded or otherwise fabricated into the desired configuration. Body  12  may be molded in two halves and the halves bonded together by ultrasound, snap fit, adhesives, or other means following assembly of buttons, pivot pins and springs into body. In one embodiment two halves of body  12  are delineated by line A-A in  FIG. 1B . Faces  14   a ,  14   b  of button  14  may be textured for increased friction against shaft  26  or the fingers of an operator or both. Springs  16  and pivot pins  18  may be comprised of metal such as steel, spring steel, or other metals, or engineering polymer such as polyester, liquid crystal polymer, nylon, or other polymers. 
     Manipulator  10  is normally in an unlocked ( FIG. 1C ) position with springs  16  extended so as to force faces  14   a  of buttons  14  away from shaft  26 . The manipulator is normally unlocked to permit the user to easily move manipulator  10  to any desired position along the shaft. For example, the user may move the manipulator with one hand to an exposed, distal portion of the shaft such as a portion of the shaft near an incision or near an introducer sheath while the other hand holds the handle  28 . Once the manipulator is positioned at the desired location along the shaft, rotation or translation (or both) of shaft  26  may be accomplished by pressing faces  14   b  of buttons  14  towards each other ( FIG. 1D ) with one hand of the user followed by rotation or translation (or both) of manipulator  10  with the same hand. 
     Use of the catheter and manipulator of  FIGS. 1A to 1D  is now described. Catheter  20  is introduced into the patient in any known manner. When the user desires to manipulate the catheter, the user grasps manipulator  10  and moves it to an appropriate location for manipulating the catheter. The user then locks the manipulator onto the shaft by pressing on faces  14   b  so as to overcome force of springs  16  and move faces  14   a  into frictional contact with shaft  26 . The manipulator is then rotated, translated, or both to effect rotation, translation, or both of cutter  22  into contact with tissue such as atheroma. In some embodiments cutter  22  is extended outside of window  24  in a radial direction and catheter  20  is advanced through the vessel with cutter  22  extended to cut atheroma. In some embodiments atheroma is directed into interior of catheter by cutter  22 . 
     The shaft manipulator has been described as being in a normally unlocked position, however, in other embodiments the shaft manipulator may be in a normally locked position so that the user exerts pressure on the jaws to open the jaws rather than close the jaws.  FIGS. 2A to 2D  illustrate shaft manipulator  30  which is configured to be in a normally locked position. Manipulator  30  is rotatably and slidably coupled to shaft  26  and configured for one-handed use. Manipulator  30  is comprised of body  32  having lumen  31 , arms  34 , springs  36  and pivot pins  38 . Arms  34  have holes therein for pivot pins to slidably fit through, have faces  34   a  and have ends  34   b  which may be enlarged. Body  32 , arms  34 , faces  34   a , springs  36  and pivot pins  38  may be made from materials, fabricated, and assembled substantially as described above for body  12 , buttons  14 , faces  14   a , springs  16  and pivot pins  38  respectively. 
     Manipulator  30  is normally in a locked ( FIG. 2C ) position with springs  36  extended so as to force faces  34   a  of arms  34  into frictional contact with shaft  26 . The manipulator is normally locked to permit the user to easily rotate or translate (or both) shaft  26 . The user may move manipulator  30  with one hand to any desired position along shaft  26  by pressing arms  34   b  towards each other so as to force faces  34   a  out of contact with shaft  26  ( FIG. 2D ) followed by rotation or translation (or both) of manipulator  30  on shaft  26 . For example, the user may move the manipulator to an exposed, distal portion of the shaft such as a portion of the shaft near an incision or near an introducer sheath. An advantage of using the manipulator is that it may be easily positioned along the shaft and manipulated with one hand while the other hand holds the handle  28 . 
     Use of the catheter and manipulator of  FIGS. 2A to 2D  is now described. Catheter  20  is introduced into the patient in any known manner. When the user desires to manipulate the catheter, the user grasps manipulator  30  and unlocks the manipulator from the shaft by pressing on ends  34   b  so as to move faces  34   a  away from frictional contact with shaft  26 . The user then moves manipulator  30  to an appropriate location for manipulating the catheter. Pressure on ends  34   b  is then removed so as to allow springs  36  to move faces  34   a  into frictional contact with shaft  26 . The manipulator is then rotated, translated, or both to effect rotation, translation, or both of cutter  22  into contact with tissue such as atheroma. In some embodiments cutter  22  is extended outside of window  24  in a radial direction and catheter  20  is advanced through the vessel with cutter  22  extended to cut atheroma. In some embodiments atheroma is directed into interior of catheter by cutter  22 . 
     Referring to the embodiment of  FIGS. 3A and 3B , another catheter  40  is shown for use with a manipulator  45 . Catheter  40  may be similar to catheter  20  described above but may be any other catheter with a working element, having shaft  46  similar to shaft  26  described above or another shaft, in any case with the addition of loop  42 . Manipulator  45  may be comprised of manipulator  10 ,  30  described above or may be another manipulator. Handle  48  may be similar to handle  28  described above but may be any other handle. 
     Catheter  40  includes shaft  46  having a loop  42  positioned between the manipulator and the handle. Loop  42  may be formed of a flexible catheter portion which is designed to form the loop when the shaft is manipulated or may be a pre-shaped loop catheter portion, and when formed is comprised of gap  44 . Shaft  46  is fixedly coupled to handle  48  so that the shaft does not rotate or translate relative to handle. When manipulator  45  is rotated or translated, loop  42  is flexible enough to permit the distal portion of the shaft to be rotated or translated by the manipulator without requiring a change in the orientation or position of the handle. During rotation or translation of shaft  46  relative to handle  48  loop  42  may become larger or smaller in diameter  47  and gap  44  may increase or decrease, or both, to accommodate rotation or translation of shall  46  while allowing handle  48  to remain in an unchanged position. 
     Use of the catheter of  FIGS. 3A and 3B  is now described. The catheter is introduced into the patient in any known manner. When the user desires to manipulate the catheter, the user grasps the manipulator and moves it to an appropriate location for manipulating the catheter. The user then locks the manipulator onto the shaft. As the shaft is manipulated, the loop will constrict, expand, or change gap as necessary to accommodate rotation, translation, or both of the shaft while the handle position remains unchanged. In some embodiments cutter  22  is extended outside of window  24  in a radial direction and catheter  20  is advanced through the vessel with cutter  22  extended to cut atheroma. In some embodiments atheroma is directed into interior of catheter by cutter  22 . 
       FIGS. 4A and 4B  illustrate another catheter  50  for use with a manipulator  55 . A distal portion of the shaft is shaped to provide an apposition force to urge the cutting element against the vessel wall. Catheter  50  may be similar to catheter  20  described above but may be any other catheter with a working element, having shaft  56  similar to shaft  26  described above or another shaft, in any case with the addition of jog  51   j  and preformed bends  51   p ,  51   d . Catheter  50  is also comprised of working element  52  and window  54  which may be similar in construction, materials, and function as working element  22  and window  24  respectively. The window  54  is positioned at a radially inner position on the shaft so that the working element  52  is urged against the vessel wall when the catheter is positioned within a vessel. Jog  51   j  and preformed bends  51   p ,  51   d  cooperate to urge working element  52  into contact with material to be cut in a vessel. Manipulator  55  may be comprised of manipulator  10 ,  30  described above or may be another manipulator. Use of manipulator  55  with catheter  50  is optional. Handle  58  may be similar to handle  28  described above but may be any other handle. 
     Catheter shaft  56  includes jog  51   j  and preformed bends  51   p ,  51   d . Jog  51   j  is comprised of a hinge structure that allows distal portion  56   d  of shaft  56  to abruptly bend in relation to mid portion  56   m  of shaft  56 . Catheter structures capable of jog are further described in U.S. patent application Ser. No. 10/896,741, filed Jul. 21, 2004 and published as US 2005/0177068 A1, paragraphs [0092] to [0094], [0100] to [0102], to [0107] and  FIGS. 1 ,  1 A,  2 ,  4 A and  4 B. The entire contents of US Patent Publication US 2005/0177068 are hereby incorporated herein in their entirety. In one embodiment the preformed bends are formed such that the mid portion and the portion of the catheter shall proximal of the mid portion lie within a first plane and the hinge element is configured to permit bending of the distal portion with respect to the mid portion only in the first plane. Preformed bends  51   p ,  51   d  may be formed by constraining distal portion  56   d  in metal molds followed by application of heat to cause catheter  56  to take the shape of the mold, or other means as are known to those of skill in the art. Preformed bend  51   p  has a lesser angle  53   p  than preformed bend  51   d  angle  53   d . Preformed bend  51   p  angles of 90 to 150 degrees are contemplated. In one embodiment preformed bend  51   p  angles are 100 to 120 degrees. In other embodiments angle  53   p  are 95, 105, 110, 115, 125, 130 or 140 degrees. Preformed bend  51   d  angles  53   d  of 100 to 180 degrees are contemplated. In one embodiment preformed bend  51   d  angles are 120 to 140 degrees. In other embodiments angle  53   d  is 110, 130, 150, 160, or 170 degrees. The length from preformed bend  51   p  to preformed bend  51   d  is generally greater than the length from preformed bend  51   d  to jog  51   j . Lengths from preformed bend  51   p  to preformed bend  51   d  of 0.5 to 2.0 inches are contemplated. In one embodiment length from preformed bend  51   p  to preformed bend  51   d  is 1.00 to 1.25 inches. In other embodiments lengths from preformed bend  51   p  to preformed bend  51   d  are 0.75, 1.5 or 1.75 inches. Lengths from preformed bend  51   d  to jog  51   j  of 0.125 to 1.0 inches are contemplated. In one embodiment length from preformed bend  51   d  to jog  51   e  is 0.375 to 0.625 inches. In some embodiments lengths from preformed bend  51   d  to jog  51   j  are 0.25, 0.5, 0.75 or 0.875 inches. The combined bends  51   d ,  51   p  and lengths between bends and between bend and jog cause catheter  56  to have a maximum excursion  56   e  from the unbent portion of catheter  56  to jog  56   j . Generally, catheters of the invention are chosen to have an excursion greater than the diameter of the vessel or conduit that catheter  50  will be used within. Excursions  56   e  of 3 to 40 millimeters are contemplated. In one embodiment excursion  56   e  is 5 to 8 mm. In some embodiments excursions  56   e  are 4, 5, 6, 7, 8, 10, 12, 15, 20, 25, 30 or 35 millimeters. 
     When catheter  50  is positioned inside a vessel V of diameter D less than unconstrained excursion  56   e , preformed bends  51   p  and  51   d  are forced to assume angles larger than their undeflected preformed angles while jog  51   j  allows distalmost portion of catheter  50  to become oriented along inner wall of vessel V. This cooperation between jog  56   j  and bends  51   p ,  51   d  forces or urges window  54  into contact with inner wall of vessel V as preformed bends attempt to restore their undeflected preformed angles. Preformed bend  51   d  maintains apposition force of cutter  52  and window  54  against the inner wall of vessel V at the low end of vessel diameters. As vessel diameter increases preformed bend  51   p  eventually starts to apply apposition force to the catheter tip as well. Urge forces of 0.05 to 0.5 lbs are contemplated. In one embodiment the urge force is 0.1 lbs. In some embodiments the urge force is 0.075, 0.2, 0.3 or 0.4 lbs. Working element  52 , such as a cutter, can be extended through window  54  to contact material to be cut, such as atheroma. During cutting, cutting forces tending to deflect cutter away from inside surface of vessel will be resisted by the urge forces produced as described above. The distal portion of shaft  56  can be rotated, translated, or both by manipulator  55  (if used) to assure that window  54  is circumferentially oriented so as to contact the material to be cut. 
     Use of the catheter of  FIGS. 4A and 4B  is now described. A catheter  50  having excursion  56   e  greater than the inside diameter of vessel V is chosen. Optionally, the catheter is introduced over a guidewire into the patient in any known manner to a location in vessel V where material is to be removed. The catheter, when introduced over a guidewire, tends to straighten somewhat and follow the guidewire to the location. Preformed bends  51   p ,  51   d  in cooperation with jog  51   j  urge window  54  against inner wall of vessel V. In some embodiments cutter  52  is extended outside of window  54  in a radial direction and catheter  50  is advanced through the vessel with cutter  52  extended to cut atheroma. In some embodiments atheroma is directed into interior of catheter by cutter  52 . Optionally, when the user desires to manipulate the catheter, the user grasps manipulator  55  and moves it to an appropriate location for manipulating the catheter. The user then locks the manipulator onto shaft  56  and rotates, translates, or both the shaft while handle  58  position remains unchanged. 
       FIGS. 5A to 5C  illustrate another catheter  60  for use with a manipulator  65 . A distal portion of the shaft is shaped to provide an apposition force to urge the cutting element against the vessel wall. Catheter  60  may be similar to catheter  20  described above but may be any other catheter with a working element, having shaft  66  similar to shaft  26  described above or another shaft, in any case with the addition of jog  61   j  and continuously decreasing radius curve  61 . Jog  61   j  may be similar in construction, materials, and function to jog  51   j . Catheter  60  is also comprised of working element  62  and window  64  which may be similar in construction, materials, and function as working element  22  and window  24  respectively. Working element  62  is positioned at a radially inward position on the shaft so that the working element  62  is urged against the vessel wall when the catheter is positioned within a vessel. Jog  61   j  and continuously decreasing radius curve  61  cooperate to urge working element  62  into contact with material to be cut in a vessel. Manipulator  65  may be comprised of manipulator  10 ,  30  described above or may be another manipulator. Use of manipulator  65  with catheter  60  is optional. Handle  68  may be similar to handle  28  described above but may be any other handle. 
     Catheter shaft  66  includes jog  61   j  and continuously decreasing radius curve  61 . Continuously decreasing radius curve  61  may be formed by constraining distal portion  66   d  of catheter shaft  66  in metal molds followed by applying heat to cause distal portion  66   d  to take the shape of the mold, or other means as are known to those of skill in the art. Distal portion  66   d  may curl around at least 90 degrees up to at least 720 degrees.  FIG. 5A  shows the shaft curling about 360 degrees and  FIG. 5B  shows the shaft curling about 720 degrees. In other embodiments distal portion  66   d  curls around 120, 150, 180, 240, 300, 480, or 600 degrees. The maximum curve diameter  63  may vary from 3 mm to 50 mm although the maximum curve diameter may be outside this range depending upon the particular application. In one embodiment the maximum curve diameter is 10 to 12 mm. In other embodiments the maximum curve diameter is 4, 6, 8, 15, 20, 25, 30, or 40 mm. 
     In another embodiment, the continuously decreasing radius curve  61  may be comprised of a number of discrete preformed bends (not shown). As can be appreciated, the number of sections of decreasing radius may vary. For example, catheters having from 2 to 100 sections are contemplated. In other embodiments, the catheter may have 4, 6, 8, 10, 15, 20, 40, 60, 75, or 100 sections. In yet another embodiment, catheter has an infinite number of sections as disclosed by the continuously variable embodiment of  FIGS. 5A to 5C . 
     The continuously decreasing radius is intended to provide a relatively uniform apposition force over a range of vessel diameters. Of course, the actual apposition force may vary considerably during use since vessel geometry and size vary considerably from patient to patient; however, the shape of the shaft tends to provide a uniform force over a range of vessel sizes. 
     When catheter  60  is positioned inside a vessel V of diameter D less than maximum curve diameter  63 , the continuously decreasing radius curve  61  is forced to increase in diameter while jog  61   j  allows distalmost portion of catheter  60  to become oriented along inner wall of vessel V. This cooperation between jog  56   j  and curve  61  forces or urges window  64  into contact with inner wall of vessel V as curve  61  attempts to restore its undeformed diameter. Working element  62 , such as a cutter, can be extended through window  64  to contact material to be cut, such as atheroma. During cutting, cutting forces tending to deflect cutter away from inside surface of vessel will be resisted by the urge forces produced as described above. The distal portion of shaft  66  can be rotated, translated, or both by manipulator  65  (if used) to assure that window  64  is circumferentially oriented so as to contact material to be cut. 
     Use of the catheter of  FIGS. 5A to 5C  is now described. The catheter is introduced over a guidewire into the patient in any known manner to a location where material is to be removed. The catheter, when introduced over a guidewire, tends to straighten somewhat and follow the guidewire to the location. Curve  61  in cooperation with jog  61   j  urge window  64  against inner wall of vessel V. In some embodiments cutter  62  is extended outside of window  64  in a radial direction and catheter  60  is advanced through the vessel with cutter  62  extended to cut atheroma. In some embodiments atheroma is directed into interior of catheter by cutter  62 . Optionally, when the user desires to manipulate the catheter, the user grasps manipulator  65  and moves it to an appropriate location for manipulating the catheter. The User then locks the manipulator onto the shaft  66  and rotates, translates, or both the shaft while handle  68  position remains unchanged. 
     The present invention has been described in connection with preferred embodiments but may, of course, be practiced while departing from the above described illustrative embodiments.