US20050222607A1 - Snare - Google Patents

Abstract

An intravascular snare device for use in capturing debris found in blood vessels. The snare device is fabricated from a tube and includes longitudinally and circumferentially extending members. The snare device specifically embodies structure that provides enhanced radial opening and angular resistance to collapse.

Description

BACKGROUND OF THE INVENTION
• The present invention relates generally to intravascular snare devices and systems and more particularly, devices which can be used to capture embolic material or thrombi found in blood vessels.
• The intravascular snare device and system of the present invention is particularly useful when performing balloon angioplasty, stenting procedures, laser angioplasty or atherectomy in critical vessels where the release of embolic debris into the bloodstream can occlude the flow of oxygenated blood to the brain or other vital organs, which can cause devastating consequences to the patient. The snare device is also suited for the removal of clots adhering to vessel walls. While the snare device and system of the present invention is particularly useful in the cerebral vasculature and neurovasculature, the invention can be used in conjunction with any vascular interventional procedure in which there is an embolic risk.
• A variety of non-surgical interventional procedures have been developed over the years for opening stenosed or occluded blood vessels in a patient caused by the build up of plaque or other substances on the wall of the blood vessel. Such procedures usually involve the remote introduction of the interventional device into the lumen of the artery, usually through a catheter. In typical carotid PTA procedures, a guiding catheter or sheath is percutaneously introduced into the cardiovascular system of a patient through the femoral artery and advanced, for example, through the vasculature until the distal end of the guiding catheter is in the common carotid artery. A guidewire and a dilatation catheter having a balloon on the distal end are introduced through the guiding catheter with the guidewire sliding within the dilatation catheter. The guidewire is first advanced out of the guiding catheter into the patient's carotid vasculature and is directed across the arterial lesion. The dilatation catheter is subsequently advanced over the previously advanced guidewire until the dilatation balloon is properly positioned across the arterial lesion. Once in position across the lesion, the expandable balloon is inflated to a predetermined size with a radiopaque liquid at relatively high pressures to radially compress the atherosclerotic plaque of the lesion against the inside of the artery wall and thereby dilate the lumen of the artery. The balloon is then deflated to a small profile so that the dilatation catheter can be withdrawn from the patient's vasculature and the blood flow resumed through the dilated artery. As should be appreciated by those skilled in the art, while the above-described procedure is typical, it is not the only method used in angioplasty.
• Another procedure is laser angioplasty which utilizes a laser to ablate the stenosis by super heating and vaporizing the deposited plaque. Atherectomy is yet another method of treating a stenosed blood vessel in which cutting blades are rotated to shave the deposited plaque from the arterial wall. A vacuum catheter is usually used to capture the shaved plaque or thrombus from the blood stream during this procedure.
• In the procedures of the kind referenced above, abrupt reclosure may occur or restenosis of the artery may develop over time, which may require another angioplasty procedure, a surgical bypass operation, or some other method of repairing or strengthening the area. To reduce the likelihood of the occurrence of abrupt reclosure and to strengthen the area, a physician can implant an intravascular prosthesis for maintaining vascular patency, commonly known as a stent, inside the artery across the lesion. The stent is crimped tightly onto the balloon portion of the catheter and transported in its delivery diameter through the patient's vasculature. At the deployment site, the stent is expanded to a larger diameter, often by inflating the balloon portion of the catheter.
• Prior art stents typically fall into two general categories of construction. A first type of stent is expandable upon application of a controlled force, as described above, through the inflation of the balloon portion of a dilatation catheter which, upon inflation of the balloon or other expansion means, expands the compressed stent to a larger diameter to be left in place within the artery at the target site. A second type of stent is a self-expanding stent formed from, for example, shape memory metals or super-elastic nickel-titanum (NiTi) alloys, which will automatically expand from a compressed state when the stent is advanced out of the distal end of the delivery catheter into the body lumen. Such stents manufactured from expandable heat sensitive materials allow for phase transformations of the material to occur, resulting in the expansion and contraction of the stent.
• The above minimally invasive interventional procedures, when successful, avoid the necessity of major surgical operations. However, there is one common problem which can become associated with all of these types of procedures, namely, the potential release of embolic debris into the bloodstream that can occlude distal vasculature and cause significant health problems to the patient. For example, during deployment of a stent, it is possible that the metal struts of the stent can cut into the stenosis and shear off pieces of plaque which become embolic debris that can travel downstream and lodge somewhere in the patient's vascular system. Pieces of plaque material can sometimes dislodge from the stenosis during a balloon angioplasty procedure and become released into the bloodstream. Additionally, while complete vaporization of plaque is the intended goal during a laser angioplasty procedure, quite often particles are not fully vaporized and thus enter the bloodstream. Likewise, not all of the emboli created during an atherectomy procedure may be drawn into the vacuum catheter and, as a result, enter the bloodstream as well.
• When any of the above-described procedures are performed in the carotid arteries, cerebral vasculature, or neurovasculature, the release of emboli into the circulatory system can be extremely dangerous and sometimes fatal to the patient. Naturally occurring debris can also be highly dangerous to a patient. That is, debris which travels through the blood vessel as a natural result of bodily functions and not as a result of an intervention procedure. Debris that is carried by the bloodstream to distal vessels of the brain can cause these cerebral vessels to occlude, resulting in a stroke, and in some cases, death. Therefore, although cerebral percutaneous transluminal angioplasty has been performed in the past, the number of procedures performed has been limited due to the justifiable fear of causing an embolic stroke should embolic debris enter the bloodstream and block vital downstream blood passages.
• Medical devices have been developed to attempt to deal with the problem created when debris or fragments that naturally occur or that enter the circulatory system following vessel treatment utilizing any one of the above-identified procedures. One approach which has been attempted is the cutting of any debris into minute sizes which pose little chance of becoming occluded in major vessels within the patient's vasculature. However, it is often difficult to control the size of the fragments which are formed, and the potential risk of vessel occlusion still exists, making such a procedure in the carotid arteries a high-risk proposition.
• In addition, the retrieval of fragmented clot may be incomplete, also resulting in emboli and distal occlusions, and further, access through tortuous lumens may prove difficult. Laser-based disruption devices employ the photo-acoustic effect to fragment clot. Local disruption may open up a proximal occlusion but also may cause significant distal emboli.
• Other techniques which have been developed to address the problem of removing embolic debris include the use of catheters with a vacuum source which provides temporary suction to remove embolic debris from the bloodstream. However, as mentioned above, there have been complications with such systems since the vacuum catheter may not always remove all of the embolic material from the bloodstream, and a powerful suction could otherwise cause problems to the patient's vasculature. Other techniques which have had some limited success include the placement of a filter or trap downstream from the treatment site to capture embolic debris before it reaches the smaller blood vessels downstream. However, there have been problems associated with conventional filtering systems as well. In particular, certain previously developed filtering devices do not optimize the area for embolic collection. That is, conventional filtering devices may not present a collection device that spans the entity of the vessel or it may include supporting structure that itself impedes emboli collection. Certain other devices do not embody sufficient angular resistance to collapse.
• Moreover, thrombectomy and foreign matter removal devices have been disclosed in the art. However, in addition suffering from the same disadvantages as certain conventional filter devices, such devices have been found to have structures which are either highly complex or lacking in sufficient or effective expansion and retraction capabilities. Disadvantages associated with the devices having highly complex structure include difficulty in manufacturability as well as use in conjunction with microcatheters. Other less complex devices can pull through clots due to in part to the lack of experience in using the same or otherwise lack an expanded profile that is adequate in capturing clots or foreign bodies.
• Furthermore, in current interventional radiology practice, the need arises to remove a variety of objects from intraluminal spaces. Among these are embolic coils, guidewire tips, distal catheter segments, thrombus and other vascular emboli, few of which can be readily removed with current devices. Thrombo-embolic materials can be friable, amorphous, and/or lubricious in nature contributing to this difficulty. Most current therapies rely on grasping, fragmenting, or dissolving the blood-based obstructions. Among the grasping devices are the loop snares and the wire basket snares. These devices may have limited effectiveness, due in part to the lack of encapsulation. Objects are difficult to grasp within these devices, and friable objects, e.g. blood-based blockages, tend to fragment when grasped or pulled, introducing multiple emboli.
• Lytic drugs are also used to dissolve blood-based obstructions. These typically have the disadvantages of lengthy treatment/infusion times to remove the obstruction (>3 hrs.), production of emboli, and the potential for systemic iatrogenic bleeding as a side effect of the drug usage. Also, these drugs are not typically effective in removing obstructions that are not blood-based.
• What has been needed is a reliable intravascular snare device and system for use when treating blood vessels. The snare devices should be capable of capturing any naturally occurring embolic debris or that which may be released into the bloodstream during an interventional treatment, while minimizing the area occupied by structure supporting the device, and safely containing the debris until the snare device is removed from the patient's vasculature. The devices should embody an expanded profile that presents a consistent radial opening that completely occupies the vessel at the repair site as well as structure for effectively resisting collapse. Moreover, such devices should be relatively easy to deploy and remove from the patient's vasculature and also should be capable of being used in narrow and very distal vasculature such as the cerebral vasculature. The following invention addresses these needs.
SUMMARY OF THE INVENTION
• Briefly and in general terms, the present invention is directed towards snares for removing undesired material or objects and restoring patency of blood vessels. The snare is a linked or monolithic framework of thin struts that is radially expansible. The snare of the present invention embodies a structure that provides a consistent radial opening as well as improved radial and angular resistance to collapse. That is, as the device is pulled such as through a vessel, the entrance thereto will not fall back or tip over. Moreover, the snare device maintains clearance in its interior space along its length allowing the material or objects to enter and be captured.
• In one aspect of the invention, the snare is manufactured from a tubular element to form struts (members run both generally longitudinally and generally circumferentially) with very small widths and thicknesses and rings (circumferential members) with very small widths and thicknesses but large expansion ratios. The body of the snare device is defined by a plurality of openings bounded by generally longitudinally and generally circumferentially extending members. A proximally extending member is attached to an elongate push member and the assembly is contemplated to be used in conjunction with a generally tubular delivery catheter.
• Overall, the intent of the invention is to provide a structure that has the capacity to engage and retain naturally occurring or foreign bodies while having a minimal profile that can traverse easily and repeatably through a standard microcatheter across tortuous anatomy. The device embodies superior flexibility to be deployed and retrieved consistently across difficult anatomy while being able to retain captured material. The inner diameter of the device is heat-set to a pre-determined size. It is envisioned that there be a family of devices that have varying strut lengths, thicknesses, flexibility, and diameters as deemed appropriate for the specific type of vascular or non-vascular setting for which the device is to be used.
• In a presently preferred embodiment, the snare device is self-expanding and includes a midsection that forms a generally tubular profile. The proximally extending member projects from a sidewall defining the generally tubular portion to thereby provide a substantially unobstructed radial opening at the proximal end of the snare. A terminal (i.e., distal) end of the snare device can be closed so as to form a pocket for receiving emboli or thrombotic debris. In the event it is desirable to employ a snare device manufactured from a tube embodying both proximal and distal open ends, a woven basket can be attached to the distal end of the device.
• The cut tube snare device can assume a number of forms. In one presently contemplated aspect, the snare device of the present invention embodies first and second end portions, a pair of longitudinally spaced rings and a midsection defined by helically extending members. In another aspect, the intravascular snare device has a midsection defined by generally parallel longitudinally extending members. In other aspects, the snare device includes a single convoluted ring or alternatively a body defined by a truncated stirrup-like structure. In yet another embodiment, the snare device has a midsection including almond-shaped apertures as viewed perpendicular to the axis of the snare.
• Moreover, the present invention embodies a tip for an endovascular device including an atraumatic soft coil for preventing damage to tissue and facilitates advanceability. The tip further includes multiple layers of coiled material to enhance these objectives as well as to provide stiffness variations.
• These and other objects and advantages of the invention will become apparent from the following more detailed description, when taken in conjunction with the accompanying drawings of illustrative embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a side view, partially in cross-section, of a vessel occluded by debris and a superior portion of a delivery catheter and intravascular snare assembly of the present invention positioned proximate the debris;
• FIG. 2 is a side view, partially in cross-section, of the intravascular snare ofFIG. 1 deployed within the vessel;
• FIG. 3 is a plan view depicting an unrolled pattern of an intravascular snare of the present invention;
• FIG. 4 is a plan view, depicting an unrolled pattern of an alternate embodiment of an intravascular snare of the present invention;
• FIG. 5 is a plan view, depicting an unrolled pattern of a further alternate embodiment of an intravascular snare of the present invention;
• FIG. 6 is a plan view, depicting an unrolled pattern of a fourth embodiment of an intravascular snare of the present invention;
• FIG. 7 is a plan view, depicting an unrolled pattern of a fifth embodiment of an intravascular snare of the present invention;
• FIG. 8 is a perspective view of the embodiment depicted inFIG. 7;
• FIG. 9 is another perspective view of the embodiment depicted inFIG. 7;
• FIG. 10 is an end on view from a proximal end viewpoint of the embodiment depicted inFIG. 7;
• FIG. 11 is an end on view from a distal end viewpoint of the embodiment depicted inFIG. 7;
• FIG. 12 is a side view, depicting an elongate member of the present invention;
• FIG. 13 is a side view, partially in cross-section, depicting a plurality of coils configured about a distal end portion of the elongate members in combination with a snare device of the present invention;
• FIG. 14 is a cross-sectional view, taken along lines14-14 depicting the assembly ofFIG. 13;
• FIG. 15 is a side view, partially in cross-section, depicting a distal end portion of a tip of the snare device of the present invention;
• FIG. 16 is a cross-sectional view, taken along lines16-16 ofFIG. 15, depicting a portion of the assembly ofFIG. 13;
• FIG. 17 is a cross-sectional view, taken along lines17-17 ofFIG. 15, depicting the assembly ofFIG. 13;
• FIG. 18 is a plan view, depicting a portion of an unrolled pattern of yet another embodiment of an intravascular snare of the present invention;
• FIG. 19 is a perspective side view, depicting one step of a manufacturing process used to produce the snare device ofFIG. 16;
• FIG. 20 is a perspective bottom view, depicting one step of a manufacturing process used to produce the snare device ofFIG. 16;
• FIG. 21 is a side view, depicting an assembled snare device ofFIG. 4 of the present invention including a braided structure for capturing emboli; and
• FIG. 22 is a perspective view, depicting one manner of attachment of the braided structure ofFIG. 21 to a loop.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Referring now to the drawings, and in particularFIGS. 1 and 2, there is shown the snare device of the present invention. Thesnare device20 is adapted to provide more consistent and improved radial opening as well as enhanced angular resistance to collapse. Moreover, thesnare device20 of the present invention is configured to facilitate the maintenance of clearance in its interior space along its length allowing the material or objects to enter and be captured. Furthermore, since it is contemplated that thesnare device20 be manufactured from a tubular member to form elements with very small widths and thicknesses, the device is thus more easily packed to a relatively smaller diameter and inherently embodies high longitudinal flexibility.
• The snare device20 (FIG. 2) of the present invention includes abody22 having aproximal end portion24 and adistal end portion26. Theproximal end portion24 is intended to be affixed to a terminal end portion of an elongate member30 (described in more detail below). In a presently preferred embodiment, thebody22 of thesnare device20 is generally tubular with a proximally directedopening32 and a generally closedterminal end34 to thereby form a basket for receiving embolus, stones, thrombus and foreign bodies found in vasculature or other body cavities.
• Thesnare device20 for intravascular uses is contemplated to be used in conjunction with a generallytubular delivery catheter40, such as a microcatheter. Additionally, it is contemplated that a conventional guide catheter (not shown) be used in combination with thedelivery catheter40 loaded with asnare device20. The guide catheter is employed to provide a guide within a patient's vasculature through which thedelivery catheter40 is inserted. A proximal end of the guide includes a “Y” adapter fitted with sealing, hemostatic valves. Thesnare device20 is intended to be self-expandable, however, it is possible to employ an expandable member such as a balloon catheter (not shown) to radially expand a snare device that is not self-expandable, but rather must be deformed to assume an expanded configuration.
• In use, thebody22 of asnare device20 is placed proximally in a compressed configuration coaxially within an internal bore of the generallytubular delivery catheter20. The longitudinally extendingelongate member30 which is attached to theproximal end24 of thebody22, is likewise coaxially received within thedelivery catheter40. Both thebody22 andelongate member30 are slidable within thedelivery catheter40 and accordingly, thedelivery catheter40 and thesnare device20 can be displaced longitudinally with respect to each other.
• A typical procedure will now be described. In order to restore patency in a vessel, the snare device/delivery catheter assembly42 is introduced into a patient's vasculature using conventional means such as the Seldinger technique. Sometimes, a cutdown is made to gain access to the patient's vasculature. Using standard endovascular techniques, the emboli in the vasculature is located. The emboli is crossed with thedelivery catheter40 and an appropriate guidewire (not shown). If the vessel is occluded, contrast is injected distal to the occlusion to map the distal vessels. Thetip26 of thedelivery catheter40 is positioned one device length or slightly more beyond the emboli. The guidewire is removed and thesnare device20 is loaded through a rear hub (not shown) of thedelivery catheter20 with the assistance of a conventional introducer sheath (not shown). Thesnare device20 is advanced 30-40 cm and the introducer sheath is then removed.
• Next, thesnare device20 is advanced until thetip26 of the basket is at the distal end of thedelivery catheter40. Thesnare device20 is held in place and thecatheter40 retracted to allow the device to expand. Holding thesnare device20 in place, thecatheter40 is pulled back until it is proximal to the emboli46. The entire system is drawn back holding relative positions between thesnare device20 and thecatheter40, allowing theemboli40 to enter thesnare device20. This step can be assisted with a “stuttering” technique where thesnare device20 is drawn out a small amount, perhaps 1-2 mm, then theelongate member30 is advanced back perhaps 2 mm to flare the mouth of thesnare device20, assisting clot entry. Then the system is drawn out another 1 mm. This is repeated until thedevice20 has traversed a distance about its own length.
• If the emboli is foreign in origin, such as a coil, the basket can be moved back and forth past the coil in an iterative attempt to engage the coil in the struts of the basket. When this has occurred, thecatheter40 can be advanced and pinch the coil, locking it into one of the openings of the basket. If the emboli is not radiopaque, its position can be checked by a contrast injection. Also, theradiopaque tip26 ofsnare device20 can be observed during this process. A pulsing motion indicates restored flow.
• Thesystem42 is then drawn back until the distal end of a proximal device marker coil (described below) is at the tip of the guide. At this point, a large syringe, perhaps 60 cc, is attached to the guide catheter at the “Y” adapter on the hub. The guide catheter is aspirated as thesnare device20 andclot46 are drawn into the guide. Aspiration is maintained until thesnare device20 is fully into the “Y” adapter of the guide catheter, but thesnare device20 is not yet drawn through the hemostatic valve. The “Y” adapter is detached and removed with the snare device in it, allowing a moment of bleed back through the guide to flush any loose clot. Optionally, then a second “Y” arm is attached to prevent excessive bleed back. The guide is then flushed with saline and the entire procedure repeated as required to remove further emboli.
• The manner in which thebody portion22 of thesnare device20 self-expands within vasculature and the resultant expansion profile provides a number of advantages. In particular, thebody22 expands to conform to therepair site44. That is, the generally tubular profile of thebody portion22 substantially conforms to the walls defining theblood vessel49. Alternatively, thesnare device20 can be sized such that upon full expansion it has a diameter smaller than the diameter of the vessel if desired. Moreover, the expansion of thebody22 facilitates the maintenance of clearance in its interior space along its length allowing the material or objects to enter and be captured and specifically provides a substantially unobstructed access to the proximally directed opening32 to thebody22. Significantly, as thebody22 self-expands,members50,51 leading to theopening32 to thebody22 are angled or oriented so as to be adjacent the walls defining theblood vessel49 and are therefore substantially removed from the flow path to thereby provide anunobstructed opening32.
• In its expanded state, thesnare device20 is particularly well-suited to remove embolic orthrombotic debris46 from theblood vessel49. As stated, thesnare device20 can be withdrawn proximally so that thedebris46 can be captured by thebody22 of thesnare device20. Alternatively, a separate pusher mechanism (not shown) can be employed to push thedebris46 within the basket defined by thebody portion22. Once the debris has been captured, thesnare device20 anddelivery catheter40 can be removed from the patient's vasculature or thesnare device20 containing thedebris46 can first be pulled within the guide catheter (not shown) and then theassembly42 removed from thetarget repair site44. Also, just the proximal portion can be cinched down to lock the debris without being fully pulled into thedelivery catheter40.
• It is to be understood, however, that thrombus or other blood-based material captured within the snare may be eliminated in a variety of ways. For example, the material may be drawn into the guide catheter with the aide of a vacuum applied to the guide catheter, and removed from the body. Also, these materials may be removed from the occluded vessel and allowed to dissolve under natural or induced lytic processes. Alternately, the blood-based material may be inserted into other vasculature more tolerant of occlusion and released.
• Referring now toFIG. 3, there is shown onepreferred pattern52 of thesnare device20 of the present invention. As will be developed further below, it is contemplated that thesnare pattern52 be cut from a tubular member using a laser. As best seen in its flattened or unrolled state, thesnare pattern52 composes abody22 including proximal anddistal end portions24,26, amidsection54 and anelongate member30 extending proximally from theproximal end portion24.
• Theproximal end portion24 includes members orleashes50 which lead to and aid in defining an opening to thebody22, when in its as cut configuration. The proximal end portion further embodies a pair ofconnectors51 extending at an angle from theleashes50 to thereby accomplish offsettingelongate member70 from a central axis of the as cuttubular body22 ofsnare device20 as best seen inFIGS. 2 and 8. Theconnectors51, in turn, converge to form a proximally directedtab53 that is connected to theelongate member30. Theleashes50 andconnectors51 define a centrally located, generally diamond-shapedaperture56, having a first length, that is substantially sandwiched between two parallelogram-shaped,proximal apertures58 having a relatively shorter second length. A proximalconvoluted ring60 defined bymembers61 arranged in a generally sinusoidal pattern is located distally adjacent theproximal end portion24. Thering60 provides for optimal radial opening of the basket-like body22.
• Thedistal end portion26 of thesnare pattern52 includes members orleashes66 which define an open ended, distally directedtriangle68 sandwiched between a pair of two, parallelogram-shaped,distal apertures70. A distalconvoluted ring72 defined bymembers73 arranged in a generally sinusoidal pattern is located proximally adjacent thedistal end portion26. Thering72 additionally provides for maximal radial opening of the body27. Distally directedextensions78 project, in a parallel fashion, from pairs of convergingleashes66.
• Themidsection54 of thesnare pattern52 includes a plurality of generally parallel longitudinally extendingmembers84, each of which are joined at an angle and at one end, respectively, to theproximal ring60. The other end of these members are joined at an angle to thedistal ring72.
• In its as cut form, the terminal ends80,82 of the parallelogram-shaped,distal apertures70 are joined together to form a substantially closed basket. This structure can be joined using soldering or by employing a coil (described hereinbelow) that is wrapped about adjacent structures to form a soft tip. Distally directedextensions78 may be trimmed to a desired length. Thelongitudinally extending members84, while maintaining a parallel relationship, each define a helical pattern to thereby form a generallytubular midsection54. The helical configuration provides flexibility around bends as well as good foreign body containment. Themembers50 form a tapered opening to the generallytubular midsection54 with theelongate member30 extending proximally from a sidewall defined by themidsection54. It is contemplated that the resultant tubular structure, in an undeformed state, includes a longitudinal axis that is parallel to both theelongate member30 and the distally directedprojections78.
• In an alternative embodiment of a snare pattern90 (FIG. 4), the proximal end anddistal end portions24,26 also includemembers50,51,66 which define proximal and distal parallelogram-shapedapertures58,70 as well as a diamond-shapedaperture56 and an open endedtriangle68. Thissecond snare pattern90 also similarly includes proximal anddistal rings60,72 as well as distally directedextensions78, each of which are joined to one of the distal parallelogram-shapedapertures70. Moreover, themidsection54 of thepattern90 includes a plurality of parallel, longitudinally extendingmembers84 which are joined to the structure defining the proximal anddistal end portions24,26. This embodiment differs from the first embodiment, however, in that the longitudinally extending members are not helically configured when thepattern90 is in its as cut form. Rather, while defining a sidewall of a generallytubular midsection54, each of thelongitudinally extending members84 are parallel to a longitudinal axis of the resultanttubular snare device20. Being so arranged, themidsection54 possesses the necessary flexibility to traverse sharp bends in anatomy as well as the capability of being packed into a small profile with minimal bulk.
• Further, it is to be recognized that as with the first embodiment, a substantial closed-ended basket is formed by joining via conventional means the terminal ends78 of thesnare pattern90. Additionally, a tapered opening to a generallytubular midsection54 is provided by theproximal end portion24 where theelongate member30 extends proximally from a sidewall defined by themidsection54.
• Although each of the proximal anddistal rings60,72 are shown as embodying a four crown design, fewer or more crowns are contemplated. Moreover, there need not be aleash50, extending from each crown. It is necessary, however, that as with the ring design depicted, the modified pattern also result in rings that provide complete open deployment consistently and reliably. To wit, such rings do not fall back. That is, there is no angular deflection when the structure is pulled into a clot or foreign body.
• Turning now toFIG. 5, in yet another embodiment of thesnare device20 of the present invention, athird snare pattern100 includes a plurality of almond-shapedapertures102 configured both circumferentially and longitudinally along thesnare pattern100. Each almond-shaped aperture includescurved members104 shared by adjacent circumferential and longitudinal almond-shapedapertures102.
• Thethird snare pattern100 additionally includes anelongate member30 extending proximally from a pair of converging, undulatingmembers105 that lead to a first pair of circumferentially spaced, almond-shapedapertures106 defined bycurved members104. Each of the first pair of circumferentially spaced, almond-shapedapertures106 are joined and share a portion of asidewall104 of two of four almond-shaped apertures defining afirst ring108 of almond-shaped apertures. In a presently preferred embodiment, a series of three additional nested rings110 of almond-shapedapertures102, though fewer or more are contemplated, complete amidsection54 of thethird snare pattern100. Extending from terminal ends112 of each almond-shapedaperture102 of the distalmost ring110, is a distally directedextension114.
• In its manufactured form, thethird snare pattern100 has amidsection54 that defines a generally tubular shape and a closed basket is formed by joining the terminal ends112 of the most distal ring ofapertures110. Again, the terminal ends may be joined using soldering, laser welding, adhesive, shrink wrap, or by employing a coil configured about adjacent structure.
• Additionally, the resultant structure includes a tapered opening to thetubular midsection54 where theelongate member30 extends proximally from a sidewall defining thetubular midsection54 and where theelongate member30 and distally directedmembers114 are each parallel to a longitudinal access of theresultant snare device20. The distally directedmembers114 can be trimmed to a desired length. An additional feature of this embodiment (andFIG. 7 described below) is that the curved transitions fromtab53 to converging, undulatingmembers105 enhances ease of retrieval of the device into a microcatheter.
• In a fourth embodiment (FIG. 6), thesnare device20 embodies asnare pattern120 that includes a singleconventional ring122 defined by a continuous set ofinterconnected members124. Theinterconnected members124 are composed of straight struts that together define a central lumen in the manufactured form. Themembers124 converge at ends thereof to form four proximal and distal crowns orvertices126,127 on each side of thering122. Thering122 serves as acentral body128 of thesnare device20.
• Asingle member130 extends from each of the fourcrowns126,127 of the ring in both proximal and distal directions. Proximally, the fourmembers130 converge into twomembers132, which again converge into asingle member134. This singleproximal member134 serves as a tab for attachment to theelongated member30.
• Extending from each of themembers130 projecting from thedistal crowns127 is a single distally directedextension136. The distally directedextensions136 can be configured to form an atraumatic tip as described herein below.
• In a fifth embodiment (FIG. 7), thesnare device20 has apattern140 similar to that of the fourth embodiment. In particular, this pattern also includes aconvoluted ring142 defined of a continuous set ofinterconnected members144. Theinterconnected members144 are composed of straight sections that together form a central lumen146 (seeFIGS. 8-11) in the manufactured form. The members converge at terminal ends thereof to form four proximal anddistal crowns147,148 on each side of thering142, which serves as acentral body150 of thedevice20. In this embodiment, however,alternative crowns147,148 at each end of thering142 are offset longitudinally from each other. Thus, every other interconnectingmember144 has a different length.
• As with the fourth embodiment, asingle member152 extends from each of the fourcrowns147,148 in both proximal and distal directions. Further, the fourmembers152 connected to theproximal crowns147 converge into twomembers154, each of which again converge to form aproximal tab156. At the distal end of thedevice20, adjacent pairs of thesingle members152 converge to asingle extension158. Again, the terminal ends158 may be joined using soldering, laser welding, adhesive, shrink wrap, or by employing a coil configured about adjacent structure.
• Referring now toFIG. 12, there is shown one preferred embodiment of theelongated member30 of the present invention. Themember30 embodies a gradual or step-tapered core comprising a proximal section of 304V stainless steel and a distal section of nitinol or an equivalent material for the intended purpose. Aproximal portion160 of themember30 has a generally constant cross-sectional profile and afirst diameter161. At a transition point162, themember30 begins to taper in a gradual and consistent, alternatively in a step-tapered manner, from thefirst diameter161 to asecond diameter163 along adistal end portion164.
• As shown inFIGS. 13 and 14, a pair of longitudinally adjacent arrangedcoils166,168 are employed to attach aproximal tab174 of asnare device20 to thedistal end portion164 of theelongate member30. The first,proximal coil166 is contemplated to be composed of 304V stainless steel, the first coil being soldered to theelongate wire30 near itstapered portion170. Thesecond coil168 is contemplated to be comprised of about 90% platinum and 10% iridium alloy. Thissecond coil168, which serves as a radiopaque marker, is soldered to theelongate member30 near adistal end portion172 of thefirst coil166. Alternatively, thesecond coil168 is soldered to thefirst coil166. Aproximal tab174 of thesnare device20 is contained within thesecond coil168 and is soldered176 to theelongate member30.
• Turning now toFIGS. 15-17, one presently preferred embodiment of adistal tip portion180 of thesnare device20 of the present invention is described. Thedistal tip portion180 is comprised of two partiallycoaxial coils182,184, the combination of which retains the extensions projecting from the body of thesnare device20. The combination also provides a soft atraumatic tip with variable stiffness from softest distally to stiffer proximally.
• Theinner coil182 is comprised of nitinol or equivalent material, and begins at aproximal location186 and extends to adistal location188. The nitinolinner coil182 provides kink resistance as well as creates a smooth stiffness transition from the tip of the basket portion of thesnare device20. Theouter coil184 is coaxially configured about adistal portion190 of theinner coil182 and is preferably comprised of 90% platinum and 10% iridium alloy or an equivalent combination of materials. As such, theouter coil184 can operate as a radiopaque marker.
• Thedistal tip portion180 further includes a roundedterminal end192 that provides a blunt atraumatic surface. Theterminal end192 embodies a soldered joint which acts in retaining the helical configuration of theouter coil184.
• With reference toFIGS. 18-20, a brief summary of the process used to manufacture thesnare devices20 of the present invention is provided, with a specific focus on a sixth embodiment of the present invention. As shown inFIG. 18, the sixth embodiment is relatively similar to a truncated third embodiment and defines a general stirrup-shapedpattern220. Thisstirrup pattern220 also includes a proximally directedtab221 and a pair of divergingmembers222 extending from thetab221. Configured at eachterminal end224 of the divergingmembers222 is a single almond-shapedaperture226 defined bycurved members228. Thecurved members228 further includeapices229,230 defining outer edges of thecurved member228. Moreover, joined to adistal end232 of each almond-shapedopening226 is a distally directedextension234.
• It is contemplated that thesnare devices20 of the present invention be cut from a tube235 (FIGS. 19 and 20) using conventional means such as a laser. In particular, a specific pattern is programmed into the laser device and the laser is activated to cut the desired pattern into thetubular element235. The excess tubular components are removed, thereby leaving a manufactured structure such as thestirrup snare pattern220 shown inFIGS. 19 and 20, corresponding to the desired pattern. In a presently preferred embodiment, a super elastic material such as nitinol is a material of choice for thesnare device20. Thereafter, post-processing such as surface treatment, burr removal and deformation of the manufactured structure is performed. Heat treating is also performed for sizing the device.
• In particular, post-processing steps include taking an as-cut device and bead blast the device with aluminum oxide blasting media. The device is then inspected under a microscope for residual slag. If slag remains, the device is bead blasted again. Thereafter, the device is heat-treated in a molten salt bath without expanding. The device is subsequently heat-expanded in a molten salt bath mounted on a suitable size mandrel. After heat expansion, surface oxidation is removed in an aqua regia bath. When nitinol is the material of choice, the nitinol is etched with HF solution to desired softness or strut size. The device is then mounted on a guidewire.
• In the case of thestirrup pattern220, the post-processing may include deforming thepattern220 and then joining together thedistal end members234 as well asadjacent apices229,230 for the purpose of achieving a closed basket for receiving debris found in vasculature. Being so configured, the pair of divergingmembers222 define an opening to the resultant basket and theelongate member30 extends from a sidewall defined by the pocket. Alternatively,distal end members234 can be left apart and a basket attached to them as described below.
• It is contemplated that certain circumstances may dictate other forms of asnare device20. In particular, it is contemplated that a braided structure can be attached to a distal end portion of any of the previously described snare patterns. A braid can also be attached along the length of the body of the snare device. As shown inFIG. 21, onesuch braided structure250 can be attached to, for example, adistal end portion26, as well as thebody snare pattern90. In such a case, rather than terminating with distally directedmembers78, thesnare device20 can includeterminal apices252 formingloops254.
• In one presently preferred embodiment,members256 defining afirst end258 of thebraided structure250 can be attached to theloops254 of theterminal apices252 by conventional means. Asecond end260 of thebraided structure250 can remain in an open configuration, or alternatively,members256 defining thesecond end260 can be joined to form a closed elongated tube.
• The snare/braid assembly provides a number of advantages. In particular, such an assembly embodies additional volume for collecting debris from vasculature. Additionally, the braided structure includes sidewalls characterized by a higher density which can, in certain circumstances, be better suited for capturing relatively smaller debris found in vasculature.
• Turning toFIG. 22, it is important that the leadingedges262 of the connection between thebraided structure250 and theloops254 formed in the distal end portions of a snare pattern be as atraumatic as possible. In one presently preferred embodiment, themembers250 defining afirst end258 of thebraided structure250 are configured into a two-legged coil263 routed such thatlegs264 of the coil extend from an outer surface of theloops254 formed in thedistal end portion26. The coil is heat-set to enhance the connection to the snare pattern. It is also contemplated that single-leg coils (not shown) could additionally be used for attachment in the event forces required to unravel the single-leg coil are greater than the force necessary to deploy and retract thebraided structure250. An atraumatic leading end, however, remains an objective, as well as space considerations (i.e., low profile for packing into microcatheter).
• The snare devices of the present invention compared to prior art loop snares each provide improved radial opening since in an expanded state, theelongate member30 is positioned substantially out of the flow path. Additionally, the device embodies improved resistance to radial loads compared to prior art loop snares. Moreover, since less deformation is required to produce a desired snare pattern, in that, angles between members are provided by laser cutting rather than from local deformations, for example, there is improved stress distribution along the snare devices of the present invention compared to prior art loop snares. Additionally, a greater reduction in radial profile can be achieved without sacrificing performance and in particular, the device can be used in conjunction with microcatheters. As such, thesnare devices20 of the present invention can be passed through narrow and tortuous vasculature. The applications of the present invention are more widespread than that of conventional snare devices because of greater retrieval characteristics while retaining the deliverability characteristics.
• The above described invention is principally conceived to be operational for use in engaging for the purpose of displacing and/or removing material either foreign or native to the body, including partial or complete obstructions embolic and/or thrombotic in nature, from intraluminal or extraluminal spaces of the body including but not limited to intravascular and/or intra-arterial regions of the neurovasculature, as well as tubings, stents, or other objects that may or may not be internal to the body. The purpose of the device is to restore functionality of the luminal space or systems dependent on the particular luminal space or as a method of producing any desired effect associated with the removal or displacement of undesirable material.
• The intended delivery of the disclosed invention is by means of a commercially available catheter selected to its ability to access the desired location of engagement. The invention may be optimized for specific locations or uses by means of sizing the individual elements in the design and/or the overall dimensions, as well as selection of materials, mesh configuration, number and relative geometry of component members to meet the requirements of the operational space. Optimizations may include tabs protruding from the sides of members to increase coverage of the open areas between members, offsetting vertices of joints to increase packing efficiency, or providing unconnected distal curved path. There may additionally be variations of the dimensions of length, thickness, and width of distal and proximal tabs for joining basket with delivery wire and distal tip to provide smooth stiffness transitions from tip to basket and basket to delivery wire. Such optimizations are means of adjusting operational attributes including: flexibility, applied circumferential force, engagement effectiveness, deliverability and traversal through tortuous vasculature, and volume of material to be engaged.
• Alternate or additional materials for the basket portion of the device may include a thermoset, elastomer, thermoplastic constituents such as nylon, or other metal either pure or alloyed, as well as composite materials such as a combination of glass, aramid, or carbon in a binding matrix. A secondary mesh of the same or dissimilar material may be added to the basket. The wire portion of the device can alternatively be made from a single metal or combination of metals for kink resistance and high flexibility. Either or both components may be tapered to give a transition in stiffness that is appropriate for the vessel in which the invention is to be delivered. The distal tip of the device may incorporate concentric coils made of nitinol, stainless steel, or other metal or plastic to provide a soft flexible atraumatic end.
• An alternate method of manufacture of the basket portion of the device may be etching, or metal or polymer injection molding. Furthermore, the device may employ any combination of coatings, agents, or features including those of that result from material addition or subtraction to create grooves, bumps, three dimensional patterns, and textures on inner and/or outer surfaces or any combination thereof to promote desired properties such as adherence of materials to be engaged, radiopacity, and low friction between the device and the vessel wall or microcatheter lumen.
• In summary, the invention is deliverable to remote regions of the neurovasculature by gaining access through the use of a guidewire and microcatheter in the vasculature and subsequent deployment of the invention through the lumen of the microcatheter. In a vessel in which flow is impeded or obstructed by material and/or objects including those formed by the body such as blood clot, the device is deployed by withdrawing the microcatheter relative to the wire. Engagement occurs as the system composed of the invention and microcatheter is pulled into the material. After the material has been engaged, removal of the material is accomplished by withdrawing the system into a guide catheter lumen through which the microcatheter is passed with or without simultaneously pulling fluid through the guide lumen.
• Thus, it will be apparent from the foregoing that, while particular forms of the invention have been illustrated and described, various modifications can be made without the parting from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.

Claims (15)

1-53. (canceled)

54. A medical device, comprising:

an elongate member, the elongate member having a proximal end portion having a first cross-sectional profile characterized by a first height and a distal end portion having a second cross-sectional profile characterized by a second height, the first height greater than the second height; and

a second device attached to the distal end portion of the elongate member, the second device sized and shaped to collect substances from vasculature.

55. The device ofclaim 54, further comprising a coil surrounding both the elongate member and a portion of the snare device.

56. The device ofclaim 54, further comprising a first coil and a second coil, the first coil positioned about the elongate member proximal of the second coil.

57. The device ofclaim 56, wherein the first coil and second coil are made from different materials.

58. The device ofclaim 57, wherein the second coil is formed from radiopaque material.

59. The device ofclaim 58, wherein the second coil is formed from about 90% platinum and about 10% iridium alloy.

60. The device ofclaim 54, wherein the elongate member is tapered.

61. The device ofclaim 54, wherein the distal end portion of the elongate member is tapered.

62. The device ofclaim 54, wherein the distal end portion of the elongate member includes a transition point at which the elongate member gradually tapers.

63. The device of claim51, wherein the distal end portion of the elongate member includes a transition point at which the elongate member tapers in a step-tapered manner.

64. The device ofclaim 54, wherein the proximal end portion and the distal end portion of the elongate member are formed from different materials.

65. The device ofclaim 64, wherein the proximal end portion is formed from stainless steel.

66. The device ofclaim 64, wherein the distal end portion is formed from nitinol.

67. The device ofclaim 54, wherein the snare device includes a body cut from a tube.

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