Patent Application
20080147110
The present invention relates to an embolic protection device for use in percutaneous procedures and, more particularly, to an improved embolic protection device having a filter mounted on a rotatable tubular member for filtering bodily fluids flowing through a vessel of a patient.
Various surgical and intravenous treatments have been developed for treating and/or removing obstructions such as plaque in stenosed regions of vessels of a patient. In balloon angioplasty, a balloon placed on the distal end of a catheter is inflated, usually with a fluid, in order to dilate the stenosed region of the vessel thereby improving fluid flow. In addition a stent may be placed in the stenosed region of the vessel in order to reduce the occurrence and severity of restenosis of the vessel. In an atherectomy or thrombectomy, a rotating blade or other similar cutting device can be used to remove plaque in a stenosed region. Surgery may also be used to remove plaque and improve fluid flow in the vessel. All of these treatments result in the production of small particles of plaque or other materials resulting in emboli that can travel in the direction of fluid flow in the vessel and block smaller vessels downstream of the stenosis resulting in stroke, tissue damage or other problems.
In order to prevent such an occurrence various embolic protection devices have been suggested that place a filter distal to the stenosed region before and/or during the angioplasty, stenting, atherectomy or other emboli producing procedure. One type of filter is a woven wire mesh filter. Another type of filter is a polymeric material with filter pores placed on or around a filter frame often made of a self-expanding shape-memory metal such as a nickel-titanium alloy known as nitinol. These filter elements are mounted on the distal end of a guidewire or other elongated member which is used to place the filter into the vessel of the body through an external opening in the body containing the vessel. In some systems a guidewire is first inserted into the lumen of the vessel and is directed past a lesion or other are of interest. After insertion of the guidewire a filter element is pushed along the wire past the lesion or other area of interest where it is deployed. For example, U.S. Pat. No. 6,179,859 issued to Bates et al. and entitled “Emboli Filtration System and Method of Use” describes a filter that is restrained in a delivery sheath until it is placed in the vessel.
In another type of embolic protection system the guidewire and filter element are simultaneously inserted into the lumen of the vessel and the filter element is directed past the lesion or other area of interest where it is deployed. For example, in U.S. Pat. No, 6,468,291 issued to Bates et al. and entitled “Emboli Filtration System Having Integral Strut Arrangement and Methods of Use” such an embolic protection device is disclosed.
Filter elements are usually mounted on one or more collars either at the distal end, the proximal end or both. These collars are then either fixed to the guidewire or are allowed to travel between one or more stops placed on the guidewire to allow longitudinal movement of the filter basket in relation to the guidewire. The proximal and distal collars of the filter basket may be allowed to rotate on the guidewire to provide rotational movement of the basket relative to the guidewire.
In such embolic protection devices when the guidewire, particularly a guidewire with an embolic protection device, is tracking through a tortuous artery, the guidewire and/or the delivery sheath restraining the embolic protection device is pushed against the vessel wall causing friction between the vessel wall and the device. If a full-length delivery sheath is used, the delivery sheath pushes against the vessel wall which would cause friction between the delivery sheath and the internal guidewire. This friction reduces the torque response of the guidewire. The torque response is defined here as the number of degrees rotated on the proximal end of the wire and the response on the distal end of the wire measured by the number of degrees the distal end of the wire rotates. If this friction were reduced, then the response of the torque response would be improved. Therefore, it would be desirable to have an embolic protection device that would enable the user to accurately navigate the embolic protection device through tortuous arteries and other vessels and provide improved torque response.
It is also desirable to provide an embolic protection device that allows the guidewire to be rotated independent of the basket. Compared with the distal end of the typical guidewire which is approximately 1.1 Fr in size, the profile of the basket is relatively much larger at around 3-4 Fr for a 6.0 mm basket. When the proximal end of the guidewire is rotated, it takes a relatively large amount of energy to rotate the distal end of the basket. This results in a delay in the response of the distal end when the torque is applied on the proximal end, which is undesirable. In some instances, the distal end does not rotate when the proximal end is rotated thereby storing the energy over the length of the wire. As additional torque is applied, the energy exceeds the frictional forces necessary to start rotating the basket at which time the basket/guide wire “whips” (defined here as uncontrolled rotation of the distal end of the basket/guide wire). This again is undesirable since the physician is unable to control the location of the guide wire tip to guide the tip of the guidewire into a vessel. By having the guide wire move independent of the basket, the phenomenon of guide wire tip “whip” can be significantly reduced.
The present invention generally relates to an embolic protection device for capture and removal of emboli from a fluid flowing in a vessel. More particularly, the invention relates to the distal end of the guidewire on which the filter element of such a device is placed. In the present invention a portion of the distal section of the central guidewire or guidewire core is covered by a tubular member that is free to rotate around the guidewire core. The tubular member may be a coil wire tube made of multiple strands of wire that is wound to form a tubular section. By putting such a tubular member or “sleeve” on the guidewire core that is not attached to the guidewire core itself, the sleeve would push against the tortuous vessel wall while letting the wire rotate freely inside the tubular member.
The present invention results in increased torque response of the guidewire and an improved ability to navigate the guidewire through tortuous vessels. Independent longitudinal movement of the basket with respect to the guidewire means that small movements of the guidewire will not result in the displacement of the basket. The distal section of the wire is well supported by the tubular member thereby preventing kinking of the wire. The tubular member gives more stiffness compared with a polymeric sleeve but yet flexible to track through tortuous vessels and provides additional support to reduce the occurrence of wire prolapse when tracking a stent deployment system over the guidewire.
The length of the tubular member should be substantially the same as the length of the flexible distal section of the guidewire core. Not only is the filter basket independent of the guidewire, but also a substantial portion of the distal end of the device including the filter basket is independent of the guidewire core.
Thus, the present invention is directed to an embolic protection device for filtering emboli in a fluid stream of a vessel of a patient comprising a guidewire core having a proximal end and a distal end and a distal portion extending a first distance from a point near the distal end, a tubular member rotatably mounted about substantially all of the distal portion of the guidewire core, said tubular member having a distal end and a proximal end and a filter fixedly mounted near the distal end of the tubular member. A tubular member is mounted along the first distance of the guidewire core, which extends approximately 10-40 centimeters for a 190 centimeter guidewire. More preferably the length of the tubular member at the distal portion should be between 15 and 35 centimeters for a 190 centimeter guidewire.
The tubular member can be a coil wire tube or a polymeric tube. The embolic protection device may have a filter with a proximal collar and a distal collar to which one or more proximal and distal strut are attached and the tubular member terminates under the proximate collar of the filter.
Alternatively, a second tubular member could extend from the proximal collar of the filter to distal collar of the filter. The filter can be of many types include a filter membrane on a filter frame or a wire mesh filter. The filter membrane could be polymeric, thin film or any other known type of filtering material. The filter may be self-actuating or actuated by a number of means including, but not limited to, mechanical compression, inflation members.
Referring to
A tubular member 110 is placed over a portion of guidewire core 102 near its distal end 106. Tubular member 110 is a polymeric tube or coil wire tube. In a preferred embodiment a coil wire tube from Asahi Intec Co., Ltd. is used. Tubular member 110 has a diameter slightly larger than the diameter of the core guidewire 102 at the distal end. The tolerance between the guidewire core 102 and the tubular member 110 is preferably approximately 0.001″ but could be 0.0005 or greater. The tubular member 110 can also be coated with a lubricious coating, such as PTFE, internally and/or externally if desired.
For a tubular member 110 that is a coil wire tube the ends are preferably soldered to prevent the wire from unraveling. Also, the ends of the tubing can be ground down a small amount if necessary to approximately 50% of the original wall thickness.
Tubular member 110 may also be composed of a polymer polymeric blend or a polymer fabric. This would give the same torque characteristics, but would results in less stiffness of the distal end. Polymers that could be used for tubular member 110 include PEEK™ polymer from Victrex plc, polyamide, polyurethane, nylon PTFE and polyethylene, among others. VICTREX PEEK polymer, is a repeat unit that comprises of oxy-1, 4-phenylenoeoxy-1, 4-phenylene-carbonyl-1, 4-phenylene, PEEK is a linear aromatic polymer that is semi-crystalline.
Tubular member 110 floats freely on the core guidewire 102 and is not attached to the core guidewire at any point along its length. Tubular member 110 is of a length, x, that is between approximately 10 and 40 centimeters for a rapid exchange system that would be between 150 to 200 centimeters in length. Preferably tubular member should have a length between 15 and 35 centimeters for such a rapid exchange system. Tubular member 110 should have a length between approximately 15 and 35 centimeters for an over-the-wire system that would be between approximately 280 and 330 centimeters in length. The important attribute of the present invention is that the tubular member 110 extend not only under the proximal end of filter 120 but that it extends a substantial distance proximal the filter 120. Preferably tubular member 110 extends at least approximately 15 centimeters along the guidewire core 102 in the proximal direction. Too long of a tubular member will unnecessarily add to the cost of the device without providing significant added benefit. Additionally, a significantly longer tubular member 110 will result in reduced pushability.
A longitudinal motion limiter 140 is a polymer sleeve or other motion limiting device attached to the core guidewire 102 to prevent migration of the tubular member 110 toward the proximal end of the core guidewire 102. Attachment of the polymer sleeve may be by any appropriate bonding means. Alternatively, core guidewire may be tapered at this point to transition to a larger diameter at the proximal end of the distal portion in order to prevent such migration.
Filter 120 in
Filter membrane 129 is attached to filter frame 128 and may be comprised of a polymeric blend or may also be made of a thin film of nitinol or other similar metal exhibiting memory characteristics. If filter membrane 129 is a polymeric membrane it can be bonded to filter frame 128 or can be molded around the filter frame 128 as part of the manufacturing process. Filter membrane 129 contains a plurality of holes which are sized to provide a path for fluid flow but are not large enough to permit emboli to pass. The preferred hole size is 0.00394″ (0.1 mm) and there are preferably approximately 3100 holes per square centimeter. Distal tip 150 is a tapered polymeric sleeve or a tapered coil that provides an atraumatic transition between the distal end 106 of the core guidewire 104 and the filter 120.
Other types of filter elements can be substitute for the filter 120 of
An additional alternative embodiment is depicted in
The preceding description has been presented with reference to presently preferred embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structure may be practiced without meaningfully departing from the principal, spirit and scope of this invention.
Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and illustrated in the accompanying drawings, but rather should be read consistent with and as support to the following claims which are to have their fullest and fair scope.
