Filter frame

[0001] 1. Field of the Invention

[0002] The present invention pertains to distal protection catheters for filtering embolic debris. More precisely, the present invention pertains to distal protection filters including a refinement to the filter frame.

[0003] 2. Description of the Related Art

[0004] Heart disease is a major problem in the United States and throughout the world. Conditions such as atherosclerosis result in blood vessels becoming blocked or narrowed. This blockage can result in lack of oxygenation of the heart, which has significant consequences since the heart muscle must be well oxygenated in order to maintain its blood pumping action.

[0005] Occluded, stenotic, or narrowed blood vessels may be treated with a number of relatively non-invasive medical procedures including percutaneous transluminal angioplasty (PTA), percutaneous transluminal coronary angioplasty (PTCA), and atherectomy. Angioplasty techniques typically involve the use of a balloon catheter. The balloon catheter is advanced over a guidewire such that the balloon is positioned adjacent a stenotic lesion. The balloon is then inflated and the restriction of the vessel is opened. During an atherectomy procedure, the stenotic lesion may be mechanically cut away from the blood vessel wall using an atherectomy catheter.

[0006] During angioplasty and atherectomy procedures, embolic debris can be separated from the wall of the blood vessel. If this debris enters the circulatory system, it could block other vascular regions including the neural and pulmonary vasculature, both of which are highly undesirable. During angioplasty procedures, stenotic debris may also break loose due to manipulation of the blood vessel. Because of this debris, a number of devices, termed distal protection devices, have been developed to filter out this debris.

[0007] The present invention pertains to distal protection filter assemblies. More particularly, the present invention pertains to distal protection filter frames. A filter frame may include a plurality of struts or ribs and a crown or mouth portion. The crown portion may be adapted and configured to have a distal protection filter coupled thereto.

[0008] A number of different mandrels may be used to manufacture the filter frame. For example, a mandrel may include a proximal region, a distal region, and a middle region. In addition, the mandrel may include grooves for holding the filter frame in place. Further, the mandrel may include openings leading to a guidewire channel or a screw dip rod.

[0009] FIG. 1 is a cross sectional view of a distal protection filter disposed within the vasculature of a patient;

[0010] FIG. 2 is a perspective view of a filter frame for use with a distal protection filter;

[0011] FIG. 3 is a flattened plan view of the filter frame;

[0012] FIG. 4 is a perspective view of an alternate filter frame for use with a distal protection filter;

[0013] FIG. 5 is a flattened plan view of the alternate distal protection filter frame;

[0014] FIG. 6 is a perspective view of a mandrel for use in forming a distal protection filter frame;

[0015] FIG. 7 is a perspective view of an alternate mandrel for use in forming a distal protection filter frame;

[0016] FIG. 8 is a cross sectional view taken through line 7-7 of the mandrel shown in FIG. 7; and

[0017] FIG. 9 is a perspective view of a second alternate mandrel for use in forming a distal protection filter frame.

[0018] The following description should be read with reference to the drawings wherein like reference numerals indicate like elements throughout the several views. The detailed description and drawings illustrate example embodiments of the claimed invention.

[0019] FIG. 1 is a cross sectional view of a distal protection filter disposed within the vasculature of a patient. When performing any one of a number of differing intravascular procedures, embolic debris may drift away from the treatment site and, potentially, obstruct downstream vascular regions. These obstructions could lead to adverse medical conditions and/or tissue damage. A strategy that may help prevent embolic debris from causing problems downstream of an intravascular procedure may include the use of a distal protection filter 10. Distal protection filter 10 includes a filter frame 12 having a filter material 14 coupled thereto.

[0020] Filter frame 12 may be comprised of metal such as nickel-titanium alloy or stainless steel and configured to have one or more struts 18 coupled to an elongate shaft or guidewire 20, and a crown defining mouth portion 22 coupled to filter material 14. Frame 12 may be self-expanding so that frame 12 will expand to engage and generally conform to the internal lumen a blood vessel 16 when being delivered (e.g., from a delivery catheter or sheath).

[0021] Distal protection filter material 14 may be coupled to guidewire 20 proximate a distal end of guidewire 20. Filter material 14 and guidewire 20 may generally comprise a number of configurations known to those skilled in the appropriate art. Filter material 14 may be comprised of a polyurethane sheet and include at least one opening that may be, for example, formed by known laser techniques. The holes or openings are sized to allow blood flow therethrough but restrict flow of debris or emboli floating in the body lumen or cavity.

[0022] Filter 10 may be generally cone-shaped, and have a proximal and a distal end. The distal end may be a narrow, V-shaped end and is secured to guidewire 20 and/or frame 12. Alternatively, filter 10 may be cylindrical with a relatively rounded distal end. Filter 10 operates between a closed collapsed profile and an open radially-expanded deployed profile for collecting debris in a body lumen. In an expanded profile, the mouth is opened and struts 18 extend radially outwardly to support the mouth. Struts 18 may be coupled to guidewire 20 by a strut coupling member 23. A number of differing configurations of filter material 14 may be substituted without departing from the spirit of the invention.

[0023] In addition, a portion of frame 12 may be comprised of or plated with radiopaque materials. Radiopaque materials are understood to be capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique during an intravascular procedure. This relatively bright image aids the user of distal protection assembly 10 in determining the location of frame 12 with respect to the patient's vascular anatomy. Radiopaque materials may include, but are not limited to, gold, platinum, tungsten alloy, and plastic material loaded with a radiopaque filler.

[0024] FIG. 2 is a perspective view of filter frame 12 for use with distal protection filter material 14. A number of features may be incorporated into filter frame 12. For example, filter frame 12 may be constructed with a geometry that is optimized for essentially complete apposition to the internal wall of blood vessel 16 (i.e., frame 12 conforms to the shape of blood vessel 16) and minimal peak strains within frame 12. Peak strain is understood to be strain at points along frame 12 where force is concentrated. Therefore, peak strain may be minimized by distributing the force evenly throughout frame 12. In addition, frame 12 includes a greater expansion ratio. Expansion ratio is understood to be the ratio of the diameter (or area) of frame 12 between an expanded configuration and a collapsed configuration. Increasing the expansion ratio may allow frame 12 to be collapsed to a generally small profile and still be capable of expanding to conform to the size of a blood vessel. These and other features may allow frame 12 to be delivered with a small profile.

[0025] Struts or ribs 18 may be pre-curved during manufacturing to include a first curved portion 24. When frame 12 is collapsed within a delivery sheath, stress on frame 12 may longitudinally deform or strain frame 12. Curved portion 24 has a constant radius so that when frame 12 is collapsed, stress and/or strain forces are evenly distributed longitudinally throughout frame 12. According to this embodiment, the peak strain within struts 18 and/or frame 12 when frame 12 may be minimized by including curved portion 24.

[0026] Struts 18 and crown portion 22 may be continuous and be joined by a second curved portion 26. Similarly to curved portion 24, portion 26 is also curved to minimize peak strain near crown portion 26. However, the radius of curvature of curved portion 26 may be variable or include portions where the radius varies. In addition, crown portion 22 extends between a distal end 28 and a plurality of strut intersection points 30. Struts 18 may extend from points 30 and be coupled to guidewire 20.

[0027] It should be noted that the number of struts 18 and points 30 can be altered without departing from the scope of the present invention. For example, frame 12 may include two, three, four, five, six, or more points. It is believed that increasing the number of struts 18 and/or points 30 would decrease the expansion ratio of frame 12. For example, increasing the number of points 30 from four to six would increase the inside diameter of frame 12. Different diameter sizes may be favored when performing an intravascular procedure within different blood vessels. FIG. 3 is a flattened plan view of distal protection filter frame 12. When manufacturing frame 12 it may be beneficial to first manufacture a planer version of the appropriate material (e.g., nickel-titanium alloy). The planer version may be formed into the desired shape by disposing frame 12 about a mandrel (examples are shown below in FIGS. 6-9) and coupling opposite ends together, for example by soldering or welding.

[0028] FIG. 4 is a perspective view of an alternate filter frame 112 for use with distal protection filter material 14. Frame 112 is essentially the same in form and function as frame 12 in that frame 112, except that frame 112 further comprises distally-oriented struts 132 in addition to struts 118. Distally-oriented struts 132 extend distally between distal end 128 of crown portion 122 and guidewire 20.

[0029] Struts 132 provide additional support for filter material 14. According to this embodiment, when frame 12 is coupled to filter material 14, struts 132 may be adapted and configured to follow the contour of filter material 14 and provide structural support along the length thereof. At a distal end, struts 132 may be coupled to the distal end of filter material 14 and/or be coupled to guidewire 20. Similarly to FIG. 3, FIG. 5 is a flattened plan view filter frame 112.

[0030] FIG. 6 is a perspective view of a mandrel 34 for use in manufacturing a distal protection filter frame (e.g., frame 12 and frame 112). Mandrel 34 includes a generally tapered or cone-like distal region 36, a middle region 38, and a tapered proximal region 40. In addition, mandrel 34 may include a distal tip 42 and a proximal tip 44 disposed proximate their respective regions. It should be appreciated that although the subsequent discussion is focused upon frame 12 it is similarly applicable to frame 112 Middle region 38 includes grooves 46 adapted and configured for holding at least a portion of filter frame 12. Grooves 46 are curved such that disposing crown portion 22 within grooves 46 may lead to the formation of second curved portion 26. In addition, the transition from the relatively straight middle region 38 to the tapered proximal region 40 may lead to the formation of first curved portion 24, although pre-curving may be desirable if the transition between proximal region 40 and middle region 38 bends more sharply than desired.

[0031] In use, the planer configurations shown in FIGS. 3 and 5 of frame 12 (and/or frame 112) may be disposed about mandrel 34 such that crown portion 22 or 122 is disposed within groove 46. Struts 18 may extend between middle region 38 and proximal region 40 wherein the transition between regions tapers struts 18 toward the center and can be used to form first curve 24. The proximal ends of struts 18 may be disposed near proximal tip 44 where they may be coupled to guidewire 20. A collar 47 may be slidably disposed along middle region 38 that is adapted and configured to be slid over struts 18 and/or crown portion 22 (or crown portion 122) to hold frame 12 in position. Once held in position, the shape of frame 12 may be set to conform to the shape of the mandrel using methods described below or those known in the art. Following shape setting, frame 12 can be removed from mandrel 34 or it may be coupled with filter material 14, for example by dipping distal region 36 into molten or partially molten filter material 14.

[0032] Heat setting may be used to set the shape of frame 12 (and frame 112). For example, frame 12 may be comprised of a shape memory alloy that can be heat set. Thus, frame 12 may be disposed about mandrel 34 and heated to set the shape of frame 12 to conform to the shape of mandrel 34. According to this embodiment, mandrel 34 (and subsequently described mandrels) may be comprised of materials that would resist heat deformation such as stainless steel. Once heat set, frame 12 deformed to an alternate shape will return to the heat set shape after force used to deform frame 12 is removed. It may be desirable to heat set frame 12 in the expanded configuration such that delivery of filter 10 from within a relatively small delivery sheath permits frame 12 to self-expand when the delivery sheath is withdrawn.

[0033] It should be noted that mandrel 34 may be hollow such that guidewire 20 may pass therethrough with opposing end extending from distal tip 42 and proximal tip 44. This embodiment may simplify the process of coupling struts 18 (or struts 132) to guidewire 20 if desired by establishing proper alignment. This step may similarly achieved independently of mandrel 34.

[0034] When used for frame 112, the above steps occur analogously to what is described above. In addition, struts 132 extend between middle region 38 and distal region 36 wherein struts 132 taper toward the center. The distal ends of struts 132 may be disposed near distal tip 42 where they may be coupled to guidewire 20.

[0035] Once frame 12 or 112 is properly configured, filter material 14 may be coupled thereto. For example, suitable filter materials may be molten or partially molten and frame 12 or 112 may be coupled to filter material 14 by dipping distal region 36 (or 136) into the suitable filter materials 14 as described above. It should be appreciated that a person of ordinary skill in the art would be familiar with suitable filter materials and method for coupling filter material 14 to frame 12.

[0036] FIG. 7 is a perspective view of an alternate mandrel 134 for use in forming a distal protection filter frame. Mandrel 134 is similar to mandrel 34 in that it includes distal region 136, middle region 138, proximal region 140, distal tip 142, and grooves 146. In addition, middle region 138 of mandrel 134 include one or more openings 148 to a guidewire channel 150. Openings 148 may be used for shaping struts or be a place for struts to extending during formation of the filter frame. According to this embodiment, a filter frame may be configured such that struts or ribs 18 pass through openings 148, into a strut channel 152 and come together at an apex 154. Openings 148 may be useful for tapering struts 18 toward guidewire 20. Other than the differences noted above, use of mandrel 134 may be similar to that of mandrel 34. FIG. 8 is a cross sectional view taken through line 7-7 of the mandrel shown in FIG. 7 showing channels 152.

[0037] FIG. 9 is a perspective view of a second alternate mandrel 234 for use in forming a distal protection filter frame. Mandrel 234 is similar to mandrel 34 in form and function in that it includes distal region 236, middle region 238, proximal region 240, distal tip 242, and grooves 246. In addition, middle region 238 of mandrel 234 includes a screw dip rod 256.

[0038] Filter frame 112 may be coupled to mandrel 234 such that crown portion 122 is disposed about middle region 238 and struts 132 are disposed within grooves 246 and extend toward distal tip 242. Screw dip rod 256 may be actuated so as to pass over and hold or set the shape of crown portion 122 into a generally circular configuration. Then, heat may be used to set the shape similarly to what is described above. Struts 132 may be coupled to guidewire 20 that may pass through mandrel 234 and exit therefrom at distal tip 242. Filter material 14 may be formed in a manner similar to what is described above.

[0039] It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the invention. The invention's scope is, of course, defined in the language in which the appended claims are expressed.