Abstract:
An atherectomy device is provided wherein a catheter has a cutting region including plurality of slotted tubular members interconnected by flexible segments. Each slotted tubular member includes cutting edges that sever occlusive material from the interior of a vessel when the cutting region is rotated. The flexible segments may be formed by cutting windows in a tapered hollow tubular member, or may comprise bellows-shaped tubes or helical coils, or may comprise one or more tubular segments and may include a lumen that allows suction to be drawn through the device, or to permit the delivery of contrast agents, dyes, fluids or drugs to the operative site. A guide catheter also may be provided for positioning the cutting region of the atherectomy device at the operative site.

Description:
RELATED APPLICATION 
     This application is a continuation-in-part of commonly assigned application Ser. No. 09/158,038, filed Sep. 21, 1998 now U.S. Pat. No. 6,019,722. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to apparatus for removing occlusive material from the interior of a vessel or stent to restore bloodflow therethrough. 
     BACKGROUND OF THE INVENTION 
     A number of atherectomy devices have been developed to remove occlusive material, such as plaque and cellular overgrowths, from the interior of a vessel to restore blood flow through the vessel. While many of these previously known devices have been widely accepted for use in interventional procedures, such devices continue to have drawbacks that limit the applicability of the devices in certain circumstances. 
     U.S. Pat. No. 4,979,951 to Simpson describes a device wherein a distal region carries a housing having an elongated slot. A cutting member disposed within the housing reciprocates past the slot to sever material protruding into the housing. A drawback of the Simpson device is that it is useful only in arteries large enough to accommodate the housing. In addition, that device cannot be used to remove occlusive material from the walls of tortuous vessels, because the device is incapable of conforming adequately to a curved vessel wall. 
     U.S. Pat. No. 5,366,464 to Belknap describes an atherectomy device formed from a tapered helical coil covered with a polymeric sheath. A plurality of elongated slots are formed in the helical coil so that the severed ends of adjacent turns of the coil form a flexible cutting edge. While the Belknap device offers the advantages of conforming to tortuous anatomy, and being able to access smaller vessels, it has been determined that the device is prone to failure during use. Specifically, the sheath material in the vicinity of the windows is incapable of sustaining the high torque loads imposed during operation of the device. 
     U.S. Pat. No. 4,020,847 to Clark describes a rotating cutter device including a slotted cylindrical member disposed at the end of a helical coil. The length of the slotted cylindrical member may make it difficult for the device to pass through or remove occlusive material in tortuous anatomy, or to insert the cutting device into smaller arteries. 
     In view of the foregoing, it would be desirable to provide an atherectomy device that permits occlusive material to be removed from tortuous and small diameter vessels, and which overcomes the disadvantages of previously known devices. 
     It further would be desirable to provide an atherectomy device capable of being configured to excise occlusive material from tapered arteries. 
     It still further would be desirable to provide an atherectomy device that enables occlusive material to be removed from vessels having a tortuous anatomy. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of this invention to provide an atherectomy device that permits occlusive material to be removed from tortuous and small diameter vessels, and which overcomes the disadvantages of previously known devices. 
     It is another object of the present invention to provide an atherectomy device capable of being configured to excise occlusive material from tapered arteries. 
     It is a further object of this invention to provide an atherectomy device that enables occlusive material to be removed from vessels having a tortuous anatomy. 
     These and other objects of the present invention are accomplished by providing an atherectomy device comprising a catheter having a cutting region including plurality of slotted tubular members interconnected by flexible segments. Each slotted tubular member includes cutting edges that sever occlusive material from the interior of a vessel when the cutting region is rotated. The flexible segments may be formed by cutting windows in a tapered hollow tubular member, or may comprise bellows-shaped tubes or helical coils. Alternatively, flexible segments may be formed by linking together a plurality of individual tubular segments using a hinge-like structure that may be freely angularly displaced. The flexible segments may be coated with a flexible polymeric material to allow suction to be drawn through the device, or to permit the delivery of contrast agents, dyes, fluids or drugs to the operative site. A guide catheter may be used for positioning the cutting region of the atherectomy device at the operative site. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments, in which: 
     FIG. 1 is a perspective view of an illustrative embodiment of an atherectomy device constructed in accordance with the principles of the present invention; 
     FIG. 2 is a detailed perspective view of the cutting region of the atherectomy device of FIG. 1; 
     FIG. 3 is a further detailed perspective view of the slotted tubular member of the cutting region of FIG. 2; 
     FIG. 4 is a detailed perspective view of the cutting region of an alternative embodiment of an atherectomy device of the present invention; 
     FIG. 5 is a detailed side sectional view of the cutting region of FIG. 4 taken along view line  5 — 5  of FIG. 4; 
     FIG. 6 is a detailed perspective view of the cutting region of another alternative embodiment of an atherectomy device of the present invention; 
     FIG. 7 is a further detailed perspective view of tubular segments of the cutting region of FIG. 6; 
     FIG. 8 is an further detailed perspective view of an alternative embodiment of tubular segments of the cutting region of FIG. 6; 
     FIG. 9 is a further detailed perspective view of a tubular member of the cutting region of FIG. 6; and 
     FIG. 10 is a detailed perspective view of the cutting region of still another alternative embodiment of an atherectomy device of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides an atherectomy device capable of negotiating and removing plaque from curved and tapered vessels, without suffering from the drawbacks of previously known devices. More particularly, an atherectomy device constructed in accordance with the principles of the present invention comprises two or more slotted tubular members connected by flexible tubular segments, so that the slotted tubular members may pass through, and sever occlusive material from, tortuous vessels. In addition, the flexible segments may be tapered to permit a cutting region of the atherectomy device to be advanced to remove occlusive material from tapered vessels. 
     Referring now to FIG. 1, a first illustrative embodiment of an atherectomy device constructed in accordance with the principles of the present invention is described. Device  10  comprises hollow guide catheter  11  having proximal end  12  and distal end  13 . Flexible cutting region  14  extends from distal end  13  of catheter  11 , and is coupled via flexible drive cable  15  to controller  16 . Controller  16  comprises a motor and circuitry, actuated by footpedal  17 , that rotates and/or longitudinally reciprocates drive cable  15  and cutting region  14 , as is per se known. Controller  16  may be configured as described, for example, in U.S. Pat. No. 5,366,464 to Belknap, which is incorporated herein by reference. 
     Catheter  11  may include one or more ports  18  for inducing suction to aspirate severed material from the operative site, as described hereinbelow. Drive cable  15  and flexible cutting region  14  preferably include a central lumen that accepts guide wire  19 , to assist in percutaneously and transluminally inserting atherectomy device  10 . Drive cable  15  may comprise, for example, a helical metal wire coil. Drive cable  15  preferably is coupled to cutting region  14  at a position within guide catheter  11 , proximal of distal end  13 , and is capable of transmitting rotation, and optionally, reciprocating motion, to cutting region  14 . 
     Referring now to FIGS. 2 and 3, cutting region  14  is described, and includes tubular members  20  and  21  and tip  22  interconnected by flexible segments  23 ,  24  and  25 . Flexible segment  23  is coupled at its proximal end, for example, by welding, friction fit, or threads, to a distal end of drive cable  15 , and at its distal end to tubular member  20 . Flexible segment  24  couples tubular member  20  to tubular member  21 , and flexible segment  25  couples tubular member  21  to tip  22 . Tip  22  includes aperture  26  through which guide wire  19  passes. 
     Each of flexible segments  23 - 25  comprises a tube, preferably tapered, in which windows  27  have been cut, for example, by chemical etching, or laser or electron beam cutting, to create a flexible lattice of hoops  28  interconnected by cross-members  29 . Flexible segments  23 - 25  may be integrally formed with tubular members  20  and  21  and tip  22 , or may be separately formed and joined by techniques per se known. Applicant has determined that by adjusting the wall thickness and length of the flexible segments and tubular members, the area of windows  27  and the number of cross-members  29 , a flexible segment having a desired degree of strength and flexibility may be obtained. Alternatively, flexible segments  23 - 25  may comprise sections of helical coil or bellows-shaped tube. 
     Tubular members  20  and  21 , and tip  22 , may be separately formed and coupled by conventional techniques, e.g., welding, threads, friction fit, etc., between flexible segments  23 - 25 , or may be integrally formed with flexible segments  23 - 25 . Each of tubular members  20  and  21  is formed from a single-piece hollow tube by cutting slots  30  that extend for a portion of the circumference of the tubular member, and include sharpened cutting edges  31 . Cutting edges  31  also may be formed to extend beyond the exterior surface of the tubular member, as shown in FIG. 3, to provide device  10  with a cutting diameter larger than that of the tubular member. Each tubular member  20  and  21  may have a uniform diameter, or may be tapered from one end to the other to match the diameters of the flexible segments to which the tubular member is coupled. 
     Guide catheter  11  may comprise a material typically used in catheter construction, such as polyethylene, polypropylene or urethane. Flexible segments  23 - 25 , tubular members  20  and  21 , and tip  22  preferably are formed from a high strength metal or metal alloy, such as stainless steel or nickel titanium. Alternatively, high strength plastic materials may be used for some or all of these components. Flexible segments  23 - 25  also may comprise metal, metal alloy or high strength plastic tapered helical coil sections. 
     In accordance with the principles of the present invention, the relative lengths of the tubular members and the flexible segments may be selected so that cutting region  14  is capable of bending within, and therefore removing occlusive material from, a vessel having a predetermined radius. In particular, previously known atherectomy devices such as described in the above-mentioned patents to Simpson and Clark are impracticable to use in curved vessels. The present invention, however, enables a series of relatively short tubular members, interconnected by short flexible segments, to be assembled that provides a very flexible device. 
     With respect to FIGS. 4 and 5, an alternative embodiment of the atherectomy device of the present invention is described. Atherectomy device  35  is constructed as described above for the embodiment of FIG.  1 . In addition, the components of the cutting region, except slots  30  and cutting edges  31 , include cover  36  comprising a flexible plastic or elastomeric material, such as polyethylene, urethane, or nylon. Cover  36  also may be impregnated with or coated with a lubricious material, such as polytetrafluoroethylene, to reduce abrasion of the vessel walls in the areas not contacted by cutting edges  31 . 
     In FIG. 5, atherectomy device  35  includes lumen  37 , which may be coupled by suitable means to port  18  of guide catheter  11 . Lumen  37  may comprise a tube formed of materials typically used in catheter construction, and may be used to aspirate severed material from the operative site, to inject contrast agents, dyes, fluids (e.g., saline), or drugs to the operative site, or combinations thereof. 
     Referring now to FIGS. 6-9, an alternative embodiment of the atherectomy device of the present invention is described. Atherectomy device  40  is constructed as described above for the embodiment of FIG.  1 . Atherectomy device  40  includes first and second tubular members  41   a  and  41   b , respectively, flexible segments  51  and  52  each comprised of a plurality of tubular segments  43 , and tip  44 . Tip  44  couples to the distal end of second tubular member  41   b , and includes aperture  42  through which guide wire  19  passes. 
     Tubular segments  43  connect to one another to form flexible segments  51  and  52 . Flexible segment  51  connects first and second tubular members  41   a  and  41   b . Flexible segment  52  couples at its proximal end, for example by welding, friction fit, or threads, to a distal end of drive cable  15 , and connects at its distal end to a proximal end of first tubular member  41   a.    
     Tubular segments  43  and first and second tubular members  41   a  and  41   b  transmit torque and conform to the tortuosity of curved vessels without exerting bending forces on the vessel walls. Specifically, because tubular segments  43  are connected by freely moveable structures that act as hinges, no continuous bending force is required to retain a give angular relationship between successive elements. Consequently, the segments freely conform to vessel tortuosity without imposing a counteracting bending force on the vessel wall. As a result, atherectomy device  40  requires less insertion force than previously known atherectomy devices. 
     As shown in FIG. 7, each of tubular segments  43  comprises first tubular portion  46  having first diameter D 1  and hinge portions  47  (illustratively tabs), second tubular portion  48  having second diameter D 2 , narrower than the first diameter, hinge portions  49  (illustratively holes or indents), and tapered section  50  coupling first tubular portion  46  to second tubular portion  48 . Tubular segments  43  may be formed from a single-piece hollow tube by cutting slots in one end of the tube, for example by chemical etching, or laser or electron beam cutting, to form hinge portions  47  that are then crimped radially inward from exterior surface  51  of the tube. Hinge portions  49  then may be cut in the other end of the tube, for example by chemical etching, or laser or electron beam cutting. Finally, tapered section  50  may be formed, for example by swaging the tube, to narrow the diameter of second tubular portion  48 . 
     Still referring to FIG. 7, a plurality of tubular segments  43  may be flexibly linked together to form flexible segments  51  and  52 . In particular, hinge portions  47  in first portion  46  of one tubular segment  43  align with and may be flexibly engaged with hinge portions  49  in second tubular portion  48  of preceding tubular segment  43 , hinge portions  47  and  49  forming hinge-like structures that may be readily angularly displaced without continued application of a bending force. For example, hinge portions  47  may snap into hinge portions  49  to flexibly link two tubular segments. A plurality of tubular segments  43  therefore may be so linked to form flexible segments  51  and  52 . Although three tubular segments  43  are shown flexibly linked in FIG. 7, a greater or fewer number of tubular segments may be so linked. 
     As shown in FIG. 8, tubular segments  43  alternatively may be formed from a single-piece hollow tube by cutting slots in one end of the tube to form hinge portions  60  that are then crimped radially outward from exterior surface  61  of the tube. Hinge portions  62  then may be cut in the other end of the tube. To link tubular segments  43  together, hinge portions  60  of one tubular segment  43  align with and may be flexibly engaged with hinge portions  62  in succeeding tubular segment  43 . Although three tubular segments  43  are shown flexibly linked in FIG. 9, a greater or fewer number of tubular segments may be so linked. 
     As shown in FIG. 9, first and second tubular members  41   a  and  41   b  each comprise first tubular portion  53  having hinge portions  54  and slots  58 , second tubular portion  55  having hinge portions  56 , and tapered section  57  coupling the first and second tubular portions. Hinge portions  54  align with and may be flexibly engaged with hinge portions  49  of a proximally-located tubular segment  43 , and hinge portions  47  of a distally-located tubular segment  43  align with and may be flexibly engaged with hinge portions  56 . It will of course be appreciated that first tubular portion  53  alternatively may include hinge portions  56 , and second tubular portion  55  alternatively may include hinge portions  54 . 
     Hinge portions  47  and  49 , and  60  and  62  may take any of a number of forms. For example, the hinge portions may comprise circumferential ridges that engage corresponding recesses in adjacent tubular segments. Alternatively, tubular segments may have tabs at either end, with alternating tubular segments having holes or indents at either end. Other combinations also are possible, as long as adjacent tubular segments have hinge portions that freely interengage. Similarly, hinge portions  54  and  56  may take any of a number of forms, as long as the hinge portions freely interengage with the hinge portions of adjacent tubular segments. 
     Referring again to FIG. 9, first tubular portion  53  also includes slots  58  that extend partially around the circumference of the tubular member, and include sharpened cutting edges  59 . Cutting edges  59  also may be formed to extend beyond the exterior surface of the tubular member to provide device  10  with a cutting diameter larger than that of the tubular member. First and second tubular members  41   a  and  41   b  may be formed from a single-piece hollow tube similar to tubular segments  43 , described above, and by additionally cutting slots  58  in first portion  53 . 
     First and second tubular members  41   a  and  41   b  and tubular segments  43  preferably are formed from a high-strength metal or metal alloy, such as stainless steel or nickel titanium. Alternatively, first and second tubular members  41   a  and  41   b  and tubular segments  43  may be formed from high strength plastic materials. 
     Referring now to FIG. 10, another alternative embodiment of the atherectomy device of the present invention is described. Atherectomy device  63  is constructed as described above for the embodiment of FIG.  1 . Atherectomy device  63  includes tapered tubular members  64   a - 64   d , tapered tubular segments  65   a - 65   d , and tapered tip  66 . Tapered tip  66  couples to the distal end of tapered tubular segment  65   d , and includes aperture  67  through which guide wire  19  passes. 
     Although not shown in FIG. 10, similar to tubular segments  43  (described above) each of tapered tubular members  64   a - 64   d  and tapered tubular segments  65   a - 65   d  comprise first and second portions having hinge portions that permit tapered tubular members  64   a - 64   d  and tapered tubular segments  65   a - 65   d  to be flexibly linked together. 
     Additionally, tapered tubular members  64   a - 64   d  and tapered tubular segments  65   a - 65   d  may be formed from a single-piece tapered hollow tube by cutting slots in one end of the tube, for example by chemical etching, or laser or electron beam cutting, to form hinge portions that are then crimped radially inward (or outward) from the exterior surface of the tube. Hinge portions then may be cut in the other end of the tube, for example by chemical etching, or laser or electron beam cutting. Finally, the tapered section may be formed, for example by swaging the tube, to narrow the diameter of the second portion. 
     Tapered tubular members  64   a - 64   d  and tapered tip  66  include slots  68  that extend partially around the circumference of the tapered tubular member and tapered tip, and include sharpened cutting edges  69 . Cutting edges  69  also may be formed to extend beyond the exterior surface of the tubular member to provide device  10  with a cutting diameter larger than that of the tubular member. 
     Tapered tubular segments  65   a - 65   d  connect tapered tubular members  64   a - 64   d  to one another. As shown in FIG. 10, tapered tubular segment  65   a  connects tapered tubular members  64   a  and  64   b , tapered tubular segment  65   b  connects tapered tubular members  64   b  and  64   c , tapered tubular segment  65   c  connects tapered tubular members  64   c  and  64   d , and tapered tubular segment  65   d  connects tapered tubular member  64   d  to tapered tip  66 . Tapered tubular segment  64   a  couples at its proximal end, for example by welding, friction fit, or threads, to a distal end of drive cable  15 . 
     Tapered tubular segments  65   a - 65   d  may be connected together to form chains of flexible segments (similar to flexible segments  51  and  52  in FIG. 6) that are used to connect tapered tubular members. Additionally, as with atherectomy device  40 , tapered tubular members  64   a - 64   d  and tapered tubular segments  65   a - 65   d  transmit torque and conform to the tortuosity of curved vessels without exerting bending forces on the vessel walls. 
     Tapered tubular members  64   a - 64   d  and tapered tubular segments  65   a - 65   d  preferably are formed from a high-strength metal or metal alloy, such as stainless steel or nickel titanium. Alternatively, tapered tubular members  64   a - 64   d  and tapered tubular segments  65   a - 65   d  may be formed from high strength plastic materials. 
     Although preferred illustrative embodiments of the invention are described above, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the invention, and the appended claims are intended to cover all such changes and modifications that fall within the true spirit and scope of the invention.