Patent Application
20090099590
The present invention relates to an embolic protection device for use in percutaneous procedures and, more particularly, to an improved embolic protection device for filtering bodily fluids flowing through a vessel of a patient by providing a strain relief between the filter frame and the distal end of the device to provide easier access of the device distal to the treatment site.
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 area 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.
In an embolic protection device 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 guidewire in relation to the filter. The proximal and distal collars of the filter basket may be allowed to rotate on the guidewire to provide rotational movement of the guidewire relative to the filter.
In an embolic protection device, the guidewire and/or the delivery sheath restraining the embolic protection device is pushed through the vessel. Ideally, the performance of the embolic protection device and guidewire system should be the same as a guidewire alone. In many embolic protection devices when the filter is captured within its delivery sheath the device is relatively stiff at the distal end of the filter. The guidewire, however, usually has a very flexible coil tip so as to be atraumatic and maneuverable. The transition between the stiff distal end of the filter and the flexible coil tip of the guidewire is prone to kinking. It would, therefore, be desirable to provide an embolic protection device that could reduce kinking at this transition in order to provide a more maneuverable and useful device.
It would also be desirable to have an embolic protection device wherein the strain relief could be easily changed or “tuned” in order to accommodate differences between various filters, guidewires and atraumatic guidewire tips.
The filter frame and filter have a larger diameter than the central guidewire core thereby causing a step transition between the guidewire core and the filter frame at the distal end. This step transition can cause problems within the vessel during implementation of the device. Furthermore, it would be desirable to have an embolic protection device in which there is a smooth transition between the atraumatic distal tip and the filter frame.
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 filter frame, particularly the transition of the distal end of the filter frame to the guidewire or core wire that is used to guide the embolic protection device into place. In the present invention a portion of the distal section or distal collar of the filter frame is cut in various configurations in order to provide an integrated strain relief element in this transition area.
The strain relief element may also be tapered so as to provide a smooth transition between the guidewire or core wire and the filter frame so as to avoid a problematic step transition. The strain relief element may be covered with a sleeve, such as a polymeric sleeve, to create an atraumatic transition.
The strain relief element of the present invention can be “tuned” by changing the cut pattern, the pitch of the cut and how the pitch varies to the distal end of the filter frame. Additionally, because the strain relief element is integral to the filter frame there is less chance of the strain relief element breaking away from the embolic protection device and thereby causing a hazard in the patient.
The strain relief element may be a single spiral cut or double spiral cut pattern or may have an interlocking castellated pattern.
Referring to
A tubular member 110 may be 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 core 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-phenylenocoxy-1,4-phenylene-carbonyl-1,4-phenylene. PEEK is a linear aromatic polymer that is semi-crystalline.
Tubular member 110 floats freely on the guidewire core 102 and is not attached to the guidewire core 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.
Tubular member 110 may also be significantly shorter at its proximal end or may be left out altogether provided that the longitudinal motion limiter 140 is moved near the proximal end of a shorter tubular member 110 or near the proximal end of the proximal collar 130 of filter frame 128. If there is no tubular member 110 then the interior diameter of proximal collar 120 and distal collar 134 should be sized so as to float freely on guidewire core 102. Alternatively, filter frame 128 may be fixed to the guidewire core 102 through any known means such as soldering, brazing, adhesive bonding or other fixation means. Fixation of the filter frame 128 will prevent rotation of the filter frame around guidewire core 128 and obviates the need for longitudinal motion limiter 140.
A longitudinal motion limiter 140 is a polymer sleeve or other motion limiting device attached to the core guidewire core 102 to prevent migration of the tubular member 110 toward the proximal end of the guidewire core 102. Attachment of the polymer sleeve may be by any appropriate bonding means. Alternatively, guidewire core 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.
The distal end of filter frame 128 ends in a proximal collar 134. As will be discussed in detail herein proximal collar 134 has an integral strain relief element 136 which can have a variety of configurations. Strain relief element 136 provides a tunable amount of flexibility depending on the pattern cut into the element. An optional sleeve 150 is a tapered polymeric sleeve or a tapered coil that provides an atraumatic transition between the distal end 106 of the guidewire core 102 and the filter 120. Strain relief element may also be covered by a polymeric sleeve 150 as shown in
Other types of filter elements can be substituted for the filter 120 of
In
An alternative cut pattern for distal strain relief element 136 is shown in
An alternative cut pattern for distal strain relief element 136 is shown in
An alternative cut pattern for distal strain relief element 136 is shown in
The filter frame 128 is typically made of a nickel-titanium (Nitinol) alloy cylinder having a thickness of between 0.002 and 0.010 inch. The various patterns for strain relief as well as the struts of the filter frame are cut into the cylinder using a laser. Integration of the strain relief reduces the manufacturing steps of making a separate component for the strain relief and then attaching the strain relief element to the distal collar of the filter frame. The spiral is formed by laser cutting and then is heat set around a mandrel of suitable diameter causing the remaining material to form (within limits) to the outer diameter of the mandrel. This provides the required inner diameter of the distal (or proximal) leg. The shape could be changed to form a gradual taper by using a tapered mandrel.
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.
