Patent Application
20070156168
The invention relates generally to intraluminal distal protection devices for capturing particulate in the vessels of a patient. More particularly, the invention relates to a filter for capturing emboli in a blood vessel during an interventional vascular procedure.
Catheters have long been used for the treatment of diseases of the cardiovascular system, such as treatment or removal of stenosis. For example, in a percutaneous transluminal coronary angioplasty (PTCA) procedure, a catheter is used to insert a balloon into a patient's cardiovascular system, position the balloon at a desired treatment location, inflate the balloon, and remove the balloon from the patient. Another example is the placement of a prosthetic stent that is placed in the body on a permanent or semi-permanent basis to support weakened or diseased vascular walls to avoid closure or rupture thereof.
These non-surgical interventional procedures often avoid the necessity of major surgical operations. However, one common problem associated with these procedures is the potential release into the bloodstream of embolic debris that can occlude distal vasculature and cause significant health problems to the patient. For example, during deployment of a stent, it is possible for the metal struts of the stent to 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. Further, pieces of plaque material can sometimes dislodge from the stenosis during a balloon angioplasty procedure and become released into the bloodstream.
Medical devices have been developed to attempt to deal with the problem created when debris or fragments enter the circulatory system during vessel treatment. One technique includes the placement of a filter or trap downstream from the treatment site to capture embolic debris before it reaches the smaller blood vessels downstream. The placement of a filter in the patient's vasculature during treatment of the vascular lesion can collect embolic debris in the bloodstream.
It is known to attach an expandable filter to a distal end of a guidewire or guidewire-like member that allows the filtering device to be placed in the patient's vasculature. The guidewire allows the physician to steer the filter to a downstream location from the area of treatment. Once the guidewire is in proper position in the vasculature, the embolic filter can be deployed to capture embolic debris. Some embolic filtering devices utilize a restraining sheath to maintain the expandable filter in its collapsed configuration. Once the proximal end of the restraining sheath is retracted by the physician, the expandable filter will transform into its fully expanded configuration. The restraining sheath can then be removed from the guidewire allowing the guidewire to be used by the physician to deliver interventional devices, such as a balloon angioplasty catheter or a stent delivery catheter, into the area of treatment. After the interventional procedure is completed, a recovery sheath can be delivered over the guidewire using over-the-wire techniques to collapse the expanded filter (with the trapped embolic debris) for removal from the patient's vasculature. Both the delivery sheath and recovery sheath should be relatively flexible to track over the guide wire and to avoid straightening the body vessel once in place.
Another distal protection device known in the art includes a filter mounted on a distal portion of a hollow guidewire or tube. A moveable core wire is used to open and close the filter. The filter is coupled at a proximal end to the tube and at a distal end to the core wire. Pulling on the core wire while pushing on the tube draws the ends of the filter toward each other, causing the filter framework between the ends to expand outward into contact with the vessel wall. Filter mesh material is mounted to the filter framework. To collapse the filter, the procedure is reversed, i.e., pulling the tube proximally while pushing the core wire distally to force the filter ends apart. A sheath catheter may be used as a retrieval catheter at the end of the interventional procedure to reduce the profile of the “push-pull” filter, as due to the embolic particles collected, the filter may still be in a somewhat expanded state. The retrieval catheter may be used to further collapse the filter and smooth the profile thereof, so that the filter guidewire may pass through the treatment area without disturbing any stents or otherwise interfering with the treated vessel.
However, regardless of how a distal protection filter is expanded during a procedure, i.e., sheath delivered or by use of a push-pull mechanism, a crossing profile of the collapsed filter is to be at a minimum to reduce interference between the filter and other interventional devices or in-placed stents. As well, a compact filter profile is beneficial in crossing severely narrowed areas of vascular stenosis.
In existing devices, the main factors contributing to the crossing profile are the wire diameter of the filter material and the marker band outer diameter. The filter material is generally inserted at each end underneath marker bands and then glued in place. Adequate space between marker bands and the filter material is required for the glue to wick around the filter material and under the marker bands, increasing the thickness in this area. Thus, what is needed is a reduced diameter method to secure the filter material to an underlying surface with a marker band surrounding the filter material.
The present invention is a filtering device having a braided embolic filter for collecting debris in a body lumen during an intravascular procedure. A filter proximal neck portion is attached to a proximal shaft and a filter distal neck is attached to a distal support shaft. The proximal shaft is slidably disposed about a core wire and the distal support shaft is attached to the core wire. Relative longitudinal movement between the proximal shaft and the core wire moves the filter ends closer together to expand the filter or moves the filter ends farther apart to collapse the filter.
The proximal and distal neck portions comprise wires of the braided filter with interstices (spaces) there between. A radiopaque polymer marker band is disposed about the proximal neck portion of the filter and is melt bonded to the proximal shaft through the interstices between the wires, thereby securing the proximal neck portion to the proximal shaft without substantially adding wall thickness, or overall diameter to the neck portion. A second radiopaque polymer marker band is disposed about the distal neck portion of the filter and is melt bonded to the distal support shaft through the interstices between the wires, thereby securing the distal neck portion without substantially adding wall thickness, or overall diameter to the neck portion.
The radiopaque polymer marker bands comprise a radiopaque polymer or a radiolucent polymer doped with a radiopaque material. The marker bands are melt bonded to the underlying surface, preferably with the use of heat shrink tubing and a heat source, wherein the heat simultaneously causes the marker band to melt and the heat shrink tubing to exert a compressive force on the underlying molten marker band material. The heat shrink tubing is subsequently removed.
The foregoing and other features and advantages of the invention will be apparent from the following description of the invention as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and form a part of the specification, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. The drawings are not to scale.
Specific embodiments of the present invention are now described with reference to the figures, where like reference numbers indicate identical or functionally similar elements. The terms “distal” and “proximal” are used in the following description with respect to a position or direction relative to the treating clinician. “Distal” or “distally” are a position distant from or in a direction away from the clinician. “Proximal” and “proximally” are a position near or in a direction toward the clinician.
The present invention is a guidewire apparatus for use in minimally invasive procedures. While the following description of the invention relates to vascular interventions, it is to be understood that the invention is applicable to other procedures where the practitioner desires to capture embolic material that may be dislodged during the procedure. Intravascular procedures such as PTCA or stent deployment are often preferable to more invasive surgical techniques in the treatment of vascular narrowings, called stenoses or lesions. With reference to
Catheter 104 is typically guided to treatment site 106 by a guidewire 118. In cases where the target stenosis is located in tortuous vessels that are remote from the vascular access point, such as coronary arteries 202 shown in
Filter guidewires in accordance with the invention include distally disposed filter 110, which may comprise a tube formed by braided filaments that define pores and have at least one proximally-facing inlet opening 112 that is substantially larger than the pores. Radiopaque markers 114, 116 are disposed about the distal filter end and the proximal filter end to aid in fluoroscopic observation of filter 110 during manipulation thereof. Optionally, at least one of the filaments of braided filter 110 may be a wire having enhanced radiopacity compared to conventional non-radiopaque wires suitable for braided filter 110.
The present invention is directed to a distal protection device, in particular, a filter 110 mounted on filter guidewire 118, which has a reduced profile in its collapsed configuration or state.
In filter guidewire 118, hollow shaft 304 is movably disposed around core wire 302, and includes relatively stiff proximal portion 306 and relatively flexible distal portion 308. Proximal portion 306 may be made from thin walled stainless steel tubing, usually referred to as hypo tubing, although other metals, such as nitinol, can be used. Various metals or polymers can be used to make relatively flexible distal portion 308, although in the present invention a polymer material is preferred for compatibility with marker band 116, as described in more detail below. Distal portion 308 can be made of materials including, but not limited to, polyamide, polyimide, polyurethane, polyethylene, or polyethylene block amide copolymer. The length of distal portion 308 may be selected as appropriate for the intended use of the filter guidewire. In one example, portion 308 may be designed and intended to be flexible enough to negotiate tortuous coronary arteries, in which case the length of portion 308 may be 15-35 cm (5.9-13.8 inches), or at least approximately 25 cm (9.8 inches). In comparison to treatment of coronary vessels, adaptations of the invention for treatment of renal arteries may require a relatively shorter flexible portion 308, and neurovascular versions intended for approaching vessels in the head and neck may require a relatively longer flexible portion 308.
When filter guidewire 118 is designed for use in small vessels, shaft 304 may have an outer diameter of about 0.36 mm (0.014 inch). The general uniformity of the outer diameter may be maintained by connecting proximal portion 306 and distal portion 308 with a lap joint 310. Lap joint 310 may use any suitable biocompatible adhesive such as ultraviolet (UV) light curable adhesives, thermally curable adhesives or so-called “instant” cyanoacrylate adhesives from Dymax Corporation, Torrington, Conn., U.S.A or Loctite Corporation, Rocky Hill, Conn., U.S.A. Lap joint 310 can be formed by any conventional method such as reducing the wall thickness of proximal portion 306 in the region of joint 310, or by forming a step-down in diameter at this location with negligible change in wall thickness, as by swaging. Other joints, such as butt joints may be used to join proximal portion 306 and distal portion 308.
Expandable tubular filter 110 is positioned generally concentrically with core wire 302, and is sized such that when it is fully deployed, as shown in
In the embodiment of
Filter 110 includes a proximal neck portion 402 that is attached to distal portion 308 of shaft 304. Proximal marker band 116 is disposed around proximal neck portion 402 of filter 110 and attaches proximal neck portion 402 to distal portion 308, as shown in
In the current example, a distal support shaft 312 is attached to a distal portion of core wire 302. Distal support shaft 312 is preferably a polymer material, such as polyamide, polyimide, polyurethane, polyethylene, or polyethylene block amide copolymer. However, distal support shaft 312 can be made of any material that is compatible with distal marker band 114 such that distal marker band 114 can be melt bonded to distal support shaft 312. A distal neck portion 502 of filter 110 is attached via distal marker band 114 to distal support shaft 312. Distal support shaft 312 can provide a rotatable connection between distal neck portion 502 and core wire 302. Distal support shaft 312 can also provide an intermediate surface for melt bonding distal neck portion 502 about core wire 302 where the surface of core wire 302 itself is incompatible for melt bonding with marker band 114. Distal marker band 114 is disposed around distal neck portion 502 of filter 110 and attaches distal neck portion 502 to distal support shaft 312, as shown in
Filter 110 is deployed by advancing, or pushing shaft 304 relative to core wire 302 such that filter distal and proximal ends 502, 402 are drawn toward each other, forcing the middle, or central section of filter 110 to expand radially. Filter 110 is collapsed by withdrawing, or pulling shaft 304 relative to core wire 302 such that filter distal and proximal ends 502, 402 are drawn apart from each other, forcing the middle, or central section of filter 110 to contract radially. Proximal and distal stops (not shown) may be utilized to limit the relative longitudinal movement between the core wire 302 and the proximal shaft 304.
In the present invention, distal and proximal marker bands 114, 116 serve the dual purpose of aiding in fluoroscopic observation of filter 110 during manipulation thereof and attaching the distal and proximal neck portions 502, 402 to a respective underlying surface, which, in the embodiment of
The marker bands are melt bonded to the underlying surface, preferably with the use of heat shrink tubing (not shown) and a heat source (hot air, radiant heater, laser, etc.) wherein the heat simultaneously causes the marker band to melt and the heat shrink tubing to exert a compressive force on the underlying molten material. The heat shrink tubing is used as a disposable tool that is removed from the assembly after the melt bonded marker band has cooled. The use of heat shrink tubing as a removable tool in a method of simultaneously compressing and melt bonding a thermoplastic tube is known by those of skill in the art of medical catheters and guidewires. An exemplary temperature range for melting a marker band and simultaneously shrinking a heat shrink tube is about 171-210° C. Melt bonding the marker bands onto distal portion 308 and distal support shaft 312 provides the added benefit of significantly reducing the diameter or profile of the bonded neck portions 402, 502. The edges of the marker bands may also be slightly tapered to reduce the likelihood of catching an edge and either damaging the marker bands or the distal protection device during assembly or handling of the distal protection device.
As shown in
Marker bands 114, 116 may be formed of a radiolucent polymer doped with a radiopaque material. For example, the polymer can be any of a variety of suitable polymers, including, but not limited to polyethylene block amide copolymer, polyethylene, linear low density polyethylene, alpha olefin copolymers, polyester, polyamide, thermoplastic polyetherurethane elastomers, thermoplastic polyester elastomers, olefin-derived copolymers, natural and synthetic thermoplastic rubbers like silicone (polydimethylsiloxane/urea copolymer) and isoprene and specialty polymers like ethylene vinyl acetate (EVA) and ionomers, etc. as well as alloys thereof. The polymer must be compatible with the material of the underlying surface, such as distal support shaft 312 and distal section 308 of shaft 304, respectively. The material preferably comprises a low durometer polymer in order to render the marker sufficiently flexible so as not to impair the flexibility of the underlying medical device component to which the finished marker is to be attached. The polymer must also impart sufficient strength and ductility to the marker compound so as to facilitate its extrusion and forming into a marker, its subsequent handling and attachment to a medical device and preservation of the marker's integrity as the distal protection device is flexed and manipulated during use. The material for proximal and distal marker bands can be different and may be selected, in conjunction with the material of the underlying surface, to impart a different flexibility on the particular section of the distal protection device. For example, it is generally desirable to have the more distal sections of the device be more flexible than the proximal portions.
The radiopaque material used to dope the polymer can be any of a number of different metals that are well known to have suitable x-ray attenuation coefficients, and can be used in pure or alloyed form. Commonly used metals include, but are not limited to, platinum, gold, iridium, palladium, rhenium, rhodium, tungsten, tantalum, silver, and tin. Bismuth subcarbonate and barium sulfate are also suitable radiopaque doping agents. Materials for radiopaque polymeric marker bands 114, 116 of the present invention can be those described in U.S. Pat. No. 6,540,721 and U.S. Published Patent Application Publication No. 2005/0064223, both of which are incorporated by reference herein in their entirety.
Although a particular embodiment of a filter device has been shown and described, it will be understood by persons skilled in the relevant art that there are various filter devices that can utilize radiopaque polymer marker bands securing the wires or filaments of a filter to an underlying surface. Such radiopaque polymer marker bands can be utilized, for example, in the various embodiments described in U.S. Pat. Nos. 6,706,055, 3,346,116, 6,818,006, and 6,866,677, all of which are incorporated by reference herein in their entirety.
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of illustration and example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the appended claims and their equivalents. It will also be understood that each feature of each embodiment discussed herein, and of each reference cited herein, can be used in combination with the features of any other embodiment. All patents and publications discussed herein are incorporated by reference herein in their entirety.
