Abstract:
Apparatus and methods are provided for use in removing thrombus from a vessel, wherein a vascular device comprises an thrombectomy element for excising or ablating thrombus and a vascular filter for capturing emboli generated during removal of the thrombus. The vascular filter comprises a support hoop having an articulation region connected near a distal end of a guide wire, and a blood permeable sac affixed to the support hoop so that the support hoop forms a mouth of the blood permeable sac. In a preferred embodiment, the thrombectomy element comprises a second support hoop and blood permeable sac attached to the guide wire proximal of the vascular filter support hoop.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 09/364,064 filed Jul. 30, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to apparatus and methods for removing thrombus from within a vascular system and filtering emboli generated by the procedure. More particularly, the present invention provides a low profile self-expanding vascular device with thrombectomy element and filter useful for the removal of thrombus and for capturing emboli generated during the thrombectomy procedure. 
     BACKGROUND OF THE INVENTION 
     Many percutaneous procedures for the removal of thrombus have been proposed. However, the procedures often dislodge material from the vessel walls. This dislodged material, known as emboli, enters the bloodstream, and may be large enough to occlude smaller downstream vessels, potentially blocking blood flow to tissue. The resulting ischemia poses a serious threat to the health or life of a patient if the blockage occurs in critical tissue, such as the heart, lungs, or brain. 
     Numerous previously known methods and apparatus have been proposed to reduce the risk of embolism. U.S. Pat. No. 5,833,644 to Zadno-Azizi et al., for example, describes the use of a balloon-tipped catheter to temporarily occlude flow through a vessel from which a stenosis is to be removed. Stenotic material removed during a treatment procedure is evacuated from the vessel before the flow of blood is restored. A drawback of such previously known systems, however, is that occlusion of antegrade flow through the vessel may result in damage to the tissue normally fed by the blocked vessel. 
     U.S. Pat. No. 5,814,064 to Daniel et al. describes an emboli filter system having a radially expandable mesh filter disposed on the distal end of a guide wire. The filter is deployed distal to a region of stenosis, and any interventional devices, such as an angioplasty balloon or stent delivery system, are advanced along the guide wire. The filter is designed to capture emboli generated during treatment of the stenosis while permitting blood to flow through the filter. Similar filter systems are described in U.S. Pat. No. 4,723,549 to Wholey et al. and U.S. Pat. No. 5,827,324 to Cassell et al. 
     One disadvantage of radially expandable filter systems such as described in the foregoing patents is the relative complexity of the devices, which typically comprise numerous parts. Connecting more than a minimal number of such parts to a guide wire generally reduces the ability of the guide wire to negotiate tortuous anatomy and increases the profile of the device in its delivery configuration. Consequently, it may be difficult or impossible to use such devices in small diameter vessels such as are commonly found in the carotid artery and cerebral vasculature. Moreover, such filter devices are generally incapable of preventing material from escaping from the filter during the process of collapsing the filter for removal. 
     International Publication No. WO 98/39053 describes a filter system comprising an elongated member, a radially expandable hoop and a cone-shaped basket. The hoop is affixed to the elongated member, and the cone-shaped basket is attached to the hoop and the elongated member so that the hoop forms the mouth of the basket. The filter system includes a specially configured delivery catheter that retains the mouth of the basket in a radially retracted position during delivery. 
     While the filter system described in the foregoing International Publication reduces the number of components used to deploy the cone-shaped basket, compared to the radial strut-type filter elements described hereinabove, it too has drawbacks. Chief among these, it is expected that it will be difficult to reduce the diameter of the radially expandable hoop to its retracted position. In particular, as the hoop is contracted through smaller radii of curvature, the stiffness of the hoop is expected to increase dramatically. This increased stiffness prevents the hoop from being contracted more tightly, and is expected to result in a delivery profile too large to permit use of the device in critical regions of the body, such as the smaller coronary arteries, carotid arteries, and cerebral vasculature. 
     In view of the foregoing disadvantages of previously known apparatus and methods, it would be desirable to provide an integrated vascular device with a thrombectomy element and a vascular filter that overcomes such disadvantages of previous vascular filters while simultaneously removing thrombus. 
     It also would be desirable to provide a vascular device that is capable of being contracted to a small delivery profile, thus permitting use of the device in small vessels. 
     It further would be desirable to provide a vascular device that is capable of being contracted to a sufficiently small profile that it may be retrieved using the guide wire lumen of previously known treatment devices, and without the need for specialized delivery catheters. 
     It still further would be desirable to provide a vascular device that reduces the risk of emboli released during thrombectomy from escaping from the device when the device is collapsed and removed. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the present invention to provide a vascular device that overcomes disadvantages of previously known thrombectomy/embolectomy devices and vascular filters, and employs few components. 
     It also is an object of this invention to provide a vascular device that is capable of being contracted to a small delivery profile, thus permitting use of the device in small vessels. 
     It is a further object of the present invention to provide a vascular device that is capable of being contracted to a sufficiently small profile that it may be retrieved using the guide wire lumen of previously known treatment devices, and without the need for specialized delivery catheters. 
     It is another object of this invention to provide a vascular device that reduces the risk of emboli or thrombus removed from the vessel wall escaping from the device when the device is collapsed and removed. 
     These and other objects of the present invention are accomplished by providing an integrated vascular device having a thrombectomy element and a vascular filter. The vascular filter comprises a blood permeable sac affixed at its perimeter to a support hoop having an articulation region. The support hoop is attached in a distal region of an elongated member, such as a guide wire, and supports a proximally-oriented mouth of the sac when the filter is deployed in a vessel. In accordance with the principles of the present invention, the support hoop includes one or more reduced-thickness articulation regions that enable the support hoop to be contracted to very small radii of curvature without the problems of increased stiffness and kinking of previously known filters. 
     The support hoop preferably has a curved profile that prevents the articulation region, when folded, from damaging the wall of the vessel. This feature also permits the device to effectively contact the walls of the vessel and reduce emboli or thrombus removed from the vessel wall from bypassing the sac. The articulation region when combined with a support hoop having a curved profile, causes the sides of the support hoop to fold inwards towards one-another when the vascular device is collapsed into a sheath for removal. This in turn closes the mouth of the sac and reduces the potential for emboli or thrombus to be released from the vascular device during removal. 
     Advantageously, use of an articulation region permits the vascular filter of the present invention to be contracted to very small diameters, thereby enabling the use of delivery catheters having diameters as small as 3 Fr. Moreover, the vascular filter of the present invention may be retracted within the guide wire lumen of conventional treatment devices, such as angioplasty catheters and stent delivery systems, thereby obviating the need to re-insert a specialized delivery catheter to remove the integrated vascular device. 
     The thrombectomy element of the integrated vascular device of the present invention preferably is attached to the elongated member proximal to the vascular filter, or may comprise a separate catheter. In a preferred embodiment, the thrombectomy element is similar in construction to the vascular filter, and may be retracted independently. Alternatively, the thrombectomy element may be any conventional atherectomy device used in conjunction with the vascular filter and may be advanced and retracted either in conjunction or independently of the vascular filer. 
     Methods of using the integrated vascular device of the present invention are provided. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and advantages of the present invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
     FIGS. 1A and 1B are, respectively, a side sectional of a previously known vascular filter contracted within a delivery sheath and an end view of that vascular device deployed in a vessel; 
     FIGS. 2A and 2B are, respectively, a perspective view of a vascular filter constructed in accordance with the principles of the present invention in a deployed state, and a detailed view of the articulation region of the device of FIG. 2A; 
     FIG. 3 is a perspective view of the vascular filter of the present invention in a folded configuration, prior to removal; 
     FIG. 4 is a plan view of the vascular filter of FIG. 2A; 
     FIGS. 5A-5B are, respectively, side-sectional views depicting the integrated vascular device of the present invention disposed within a delivery sheath, and in a deployed state; 
     FIGS. 6A-6E are side-sectional views depicting a method of deploying, using and retrieving the integrated vascular device of the present invention; and 
     FIGS. 7A-7B are, respectively, side-sectional views depicting an alternative embodiment of the integrated vascular device disposed within a delivery sheath, and in the deployed state. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1A and 1B, some of the disadvantages associated with previously known vascular filters, such as the emboli filters described in the above-mentioned International Publication WO 98/39053, are described. The vascular filter comprises guide wire  10  having hoop  12  coupled to its end. Filter sac  14  is affixed to hoop  12 , so that when delivery catheter  16  is retracted proximally and guide wire  10  is held stationary, hoop  12  radially expands to contact the walls of a vessel. 
     As described hereinabove, one difficulty with such vascular filters is that the hoop used to support the filter sac experiences increased stiffness when contracted to small diameters, i.e., due to the sharp directional change at the tip of the hoop, thereby limiting the minimum delivery profile achievable for such instruments. Although this effect may be reduced by decreasing the thickness of the wire employed in hoop  12 , at the point at which the wire becomes sufficiently thin to accommodate the bending stresses, the wire is too thin to effectively radially expand and urge the filter sac into engagement with the vessel wall. 
     On the other hand, as shown in FIGS. 1A and 1B, the bending stresses imposed upon the hoop of such previously known devices, if drawn within a delivery catheter, may be sufficiently high to result in the formation of kink  18  at the tip of the hoop. This “kinking” effect becomes more severe in sheaths having a small inner diameter. Thus, for example, applicant has observed that when sheaths having inner diameters of 0.035″ or smaller are used, a hoop of nitinol or multi-strand nitinol cable having a diameter of 0.0055 inches will form kink  18 . Kink  18  in turn may apply relatively high localized pressure and friction against wall  17  of sheath  16 , thereby making the vascular filter difficult to deploy. In particular, the kink may impale wall  17  of delivery sheath  16  and may make it difficult or impossible to deploy the vascular filter, especially in tortuous anatomy. 
     In addition, when the filter is subsequently deployed in vessel V, as shown in FIG. 1B, kink  18  may deform the pre-formed shape of hoop  12 , impairing the ability of the filter to seal against the walls of vessel V. This may in turn lead to the presence of gaps G between the perimeter of the hoop and the vessel wall, depending upon the severity of the kink. Consequently, emboli may pass through the gaps with antegrade flow and significantly reduce the efficacy of the filter. Additionally, kink  18  may be sufficiently sharp to damage or dissect the wall of vessel V when the filter is deployed. 
     The vascular filter of the integrated vascular device of the present invention solves the above-described disadvantages, providing a vascular filter with a self-expanding support hoop that is sufficiently thick to radially expand and urge a blood permeable sac into engagement with the vessel wall, but which includes an articulation region that overcomes the problems associated with kinking. In particular, the vascular filter includes a reduced thickness articulation region and a pre-formed curved profile that avoids the difficulties of previously known systems while providing a high degree of efficacy in capturing emboli or thrombus, and ease of deployment and retrieval. 
     Referring now to FIGS. 2A and 2B, vascular filter  20  of the integrated vascular device constructed in accordance with the principles of the present invention comprises guide wire  22 , support hoop  24  having articulation region  26 , and blood permeable sac  28  affixed to support hoop  24 . Sac  28  is coupled to support hoop  24  so that the support hoop  24  forms an opening for the sac. Support hoop  24  preferably is connected to guide wire  22  near distal end  23  of the guide wire. 
     Sac  28  preferably is constructed of a thin, flexible biocompatible material, such as polyethylene, polypropylene, polyurethane, polyester, polyethylene tetraphlalate, nylon or polytetrafluoroethylene, or combinations thereof, and includes openings or pores  30  that permit blood cells to pass through the sac substantially unhindered, while capturing any larger emboli that may be released during a procedure such as angioplasty or stent placement. In a preferred embodiment, sac  28  has openings or pores  30  in a range of about 20 to 400 microns in diameter, and more preferably, about approximately 80 microns. These pores sizes will permit red blood cells (which have a diameter of approximately 5 microns) to easily pass through the sac. If sac  28  comprises a woven material, such as formed from the above-mentioned polymers, the pore size of the sac may be determined as a function of the pattern and tightness of the weave. 
     Support hoop  24  comprises a hoop having a circular or rectangular cross-section that is formed of a super-elastic material, such as a nickel-titanium alloy (“nitinol”). During deployment and retrieval of vascular filter  20 , described hereinafter, support hoop  24  folds in half and collapses to fit within a small diameter delivery sheath. When vascular filter  20  is in a deployed state, as depicted in FIG. 2A, support hoop  24  resumes its pre-formed shape. Support hoop  24  preferably comprises nitinol wire, although it may also be formed from a multistrand nitinol cable, or other super-elastic material. 
     In accordance with the principles of the present invention, support hoop  24  includes reduced-thickness articulation region  26 , illustratively, disposed opposite to point  32  at which support hoop  24  is affixed to guide wire  22 . Support hoop  24  is pre-formed to form a structure having curved regions  34 , so that articulation region  26  preferably is disposed in a portion of the support hoop that is approximately parallel to a vessel wall when vascular filter  20  is deployed. As depicted in FIG. 2B, articulation region  26  includes a region having reduced thickness t 1  compared to thickness t of the remainder of support hoop  24 . Articulation region  26  and curved regions  34  enable support hoop  24  to fold with a pre-determined shape when vascular filter  20  is collapsed to a contracted state for delivery or retrieval. 
     In FIG. 2B, articulation region  26  is depicted as a localized reduction in the thickness of support hoop  24 , as may be achieved, for example, using conventional grinding or etching processes, or electropolishing. Alternatively, support hoop  24  may be continuously tapered along its circumference, so that articulation region  26  results from a more gradual reduction in the wall thickness of the support hoop. Tapering support hoop  24  may permit greater flexibility in the vicinity of articulation region  26 , thus enabling support hoop  24  to fold more easily at the articulation region. Such tapering of the thickness of the support hoop along a portion of its circumference also may reduce the potential for stress-induced fracture typically associated with abrupt changes in diameter. 
     In a preferred embodiment of vascular filter  20  of the integrated vascular device of the present invention, vascular filter  20  easily fits within a delivery sheath having an inner diameter of 0.033″, and more preferably, may be used with a delivery sheath having an inner diameter as small as 0.026″. The deployed diameter of support hoop  24  preferably is approximately 7 mm, while guide wire  22  preferably has a diameter of 0.014″, and tapers at its distal end. The distal end of guide wire  22  also may be tipped with a spring section, or coil tip, such as are per se known. 
     Support hoop  24  preferably is constructed of 0.0055″ nitinol wire tapered (by a grinding process) to 0.0025″ at articulation region  26 . Specifically, articulation region  26  preferably consists of a length about 0.05″ long and having a diameter of 0.0025″, coupled on either side to curved regions  34 . Each of curved regions  34  includes of a length of wire that is tapered from a diameter of 0.055″ to a diameter of 0.0025″ over a length of about 0.025″. Support hoop  24  also may include radiopaque features, such as gold or platinum bands  33 , spaced at intervals around the circumference of support hoop  24 . 
     With respect to FIGS. 3 and 4, additional features of vascular filter  20  are described. FIG. 3 depicts vascular filter  20  of FIG. 3 in a contracted state, while FIG. 4 provides an exaggerated view of the directional change in support hoop  24  caused by the presence of curved regions  34 . In particular, FIG. 4 illustrates how, in a preferred embodiment, curved regions  34  orient articulation region  26  in a direction parallel to the axis of guide wire  22 . 
     Advantageously, use of articulation region  26  and the curved profile of support hoop  24  introduced by curved regions  34  also cause support hoop  24  to fold in half during retrieval. As shown in FIG. 3, support hoop  24  folds in half, effectively closing the mouth of blood permeable sac  28  and preventing the escape of collected emboli or thrombus. This feature also may permit the use of a smaller or shallower sac than would not otherwise be possible, without increasing the risk of material escaping from the filter when the sac is collapsed for retrieval. Use of a smaller or shallower sac also enables vascular filter  20  to be delivered in a smaller delivery sheath, having an inner diameter as small as 0.026″ for the preferred embodiment. 
     In a preferred embodiment, the thrombectomy element of the integrated vascular device of the present invention is similar in construction to vascular filter  20  described above, and is connected to guide wire  22  proximal to vascular filter  20 . The thrombectomy element may be retracted independently of vascular filter  20 . Alternatively, the thrombectomy element may be disposed on a separate catheter. 
     Referring now to FIGS. 5A and 5B, the integrated vascular device of the present invention is described. Integrated vascular device  50  comprises guide wire  51 , thrombectomy element  52  including support hoop  53  and blood permeable sac  54 , and vascular filter element  55  including support hoop  56  and blood permeable sac  57 . Filter hoop  56  is attached to guide wire  51  while thrombectomy hoop  53  is attached to ring  58 . Ring  58  is attached to pull wire  59  and has a bore through which guide wire  51  passes. Ring  58  therefore acts as a linear bearing and allows thrombectomy hoop  53  to be moved by pull wire  59  independently of guide wire  51 . Alternatively, thrombectomy element  52  may omit sac  54  and simply comprise a wire hoop; in this case severed thrombus is captured by vascular filter  55 . 
     In FIG. 5A, support hoops  53  and  56  and blood permeable sacs  54  and  56  are contracted to a delivery state within lumen  60  of delivery sheath  61 . Delivery sheath  61  includes nose cone  62  affixed to distal region  63  of guide wire  51 . In FIG. 5B, integrated vascular device  50  is shown deployed in a vessel. As illustrated in FIG. 5B, vascular filter  55  expands to engage the perimeter of the vessel and prevent thrombus from bypassing the blood permeable sac, while thrombectomy element  52  engages the vessel wall proximal of vascular filter  55 . As described hereinbelow, proximal movement of thrombectomy device  52  scrapes thrombus from the wall of the vessel when pull wire  59  pulls ring  58  and support hoop  53  proximally. 
     Referring now to FIGS. 6A-6E, an illustrative method of using the integrated vascular device of the present invention for thrombectomy is described. In FIG. 6A, guide wire  51  is manipulated into position proximal to thrombus T within vessel V using well-known percutaneous techniques. Vascular device  50  of FIGS. 5A and 5B is disposed in its contracted delivery state within the distal end of delivery sheath  61  and the delivery sheath is advanced through the vessel using distal end  63  of guide wire  51 . The sides of support hoops  53  and  56  are folded together and become elongated when drawn within delivery sheath  61 , as described with respect to vascular device  20  of FIGS. 2-4. 
     With respect to FIG. 6B, once delivery sheath  61  is disposed at the desired location proximal to thrombus T within a patient&#39;s vessel V, such as a coronary artery or carotid artery, for example, based on the position of, for example, radiopaque bands under a fluoroscope, integrated vascular device  50  is advanced through thrombus T. Distal end  63  of guide wire  51  is advanced through the lesion, then nose cone  62  gradually increases the diameter of the void within thrombus T so that the remainder of delivery sheath  61  can be advanced far enough that thrombectomy element  52  (still within delivery sheath  61 ) is located distal to thrombus T. 
     With integrated vascular device  50  in position, guide wire  51  is held stationary while delivery sheath  61  is retracted proximally, as seen in FIG.  6 C. Alternatively, delivery sheath  61  may be held stationary while guide wire  51  is advanced. In either case, when vascular device  50  is no longer confined within delivery sheath  61 , support hoops  53  and  56  expand to seal against the walls of the vessel V and deploy blood permeable sacs  54  and  57 , respectively. Blood continues to flow through vessel V in direction A, impeded only by thrombus T. 
     In FIG. 6D, once vascular device  50  is deployed in vessel V, thrombus T is removed in the following manner. Vascular filter support hoop  53  is rigidly attached to guide wire  51 , while thrombectomy support hoop  53  is attached to pull wire  59  via ring  58 . Thrombectomy element  52  then is retracted proximally to scrape along the wall of the vessel V by motion at the proximal end of pull wire  59 . Thrombus T, located proximal to thrombectomy element  52 , is excised so that it is captured in blood permeable sac  54  during the retraction. 
     With respect to FIG. 6E, once thrombus T has been captured within sac  54 , pull wire  59  is pulled proximally to cause the sides of thrombectomy support hoop  53  to collapse together to close the mouth of sac  28  (see FIG.  3 ). Additional proximal retraction of pull wire  59  causes support hoop  53  and sac  54  to enter within lumen  60  of delivery sheath  61 , restoring normal blood flow to vessel V. Meanwhile, vascular filter  55  is in a position distal to thrombectomy element  52  to trap emboli E, i.e., pieces of plaque dislodged from either thrombus T or the walls of vessel V by thrombectomy element  52 . Once any emboli E have been collected, filter hoop  56  and sac  57  are retracted into delivery sheath  61  by motion at the proximal end of guide wire  51 , in a manner similar to the retraction of hoop  53  and sac  54 . Once guide wire  51  has been fully retracted and nose cone  62  at the distal end  63  of guide wire  51  is again in contact with delivery sheath  61 , the delivery sheath is withdrawn with integrated vascular device  50 , the trapped thrombus T and any trapped emboli E. 
     Advantageously, the compliant design of integrated vascular device  50  permits the device to be contracted to its delivery state within the guide wire lumen of conventional previously known interventional devices. Accordingly, unlike previously known vascular devices, which require removal of the interventional device followed by re-insertion of a specially designed catheter to retrieve the vascular device, the system of the present invention reduces the time, effort and trauma of this additional step. Instead, the vascular device may be readily closed and retrieved upon completion of the interventional procedure. 
     Referring now to FIGS. 7A and 7B, an alternative embodiment of the integrated vascular device of the present invention is described. Integrated vascular device  70  comprises guide wire  71 , thrombectomy element  72  and vascular filter  73  including support hoop  74  and blood permeable sac  75 . Filter hoop  74  is attached to guide wire  71 , while thrombectomy element  72  is disposed to slide along guide wire  71 . Alternatively, thrombectomy element  72  may be disposed on a separate catheter element that extends either through lumen  77  of delivery sheath  78  or is separately disposed proximal to vascular filter  73 . 
     FIG. 7A shows thrombectomy element  72  and vascular filter  73  contracted in a delivery state within lumen  77  of delivery sheath  78 . Delivery sheath  78  includes nose cone  79  affixed to distal region  80  of guide wire  71 . In FIG. 7B, integrated vascular device  70  is shown in the deployed state. Thrombectomy element  72  may comprise any of a family of known thrombectomy, atherectomy, or, alternatively, drug delivery devices suitable for use in conjunction with vascular filter  73 . 
     Specifically, thrombectomy element  72  may comprise any of: a rotary ablation device, such as described in U.S. Pat. Nos. 4,867,156 to Stack et al., 4,990,134 to Auth, and 5,314,407 to Auth et al.; an atherectomy technology, such as described in U.S. Pat. Nos. 5,181,920 to Mueller et al., and 5,074,841 to Ademovic et al.; or a balloon embolectomy technology, such as described in U.S. Pat. Nos. 3,923,065 to Nozick et al., 5,769,871 to Mers Kelly et al., 5,192,290 to Hilal, 5,112,347 to Taheri, and 4,030,503 to Clark III. All of the foregoing patents are incorporated herein by reference. Thrombectomy element  72  may alternatively comprise a wire loop or ring such as alternatively described for the embodiment of FIGS. 5A and 5B, a laser ablation device, a chemical flushing system, etc. 
     Although preferred illustrative embodiments of the present invention are described above, it will be evident to one skilled in the art that various changes and modifications may be made without departing from the invention. It is intended in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the invention.