Embolic filter frame having looped support strut elements

[0095] As shown in FIG. 15, a 0.9 mm nitinol tube 104, with a wall thickness of approximately 0.09 mm (obtained from SMA Inc, San Jose, Calif.) was laser cut by Laserage Technologies Inc, Waukegan, Ill., to form a frame configuration of a single, undulating, integral, 6 apex ring. The frame included radiopaque marker housings 106 at each distal apex and tether or strut elements 34 extending from each proximal apex 108 and converging at the opposite end in a "collar" 46 of uncut parent material. This frame was then lightly grit blasted at 30 psi with 20-micron silicon carbide media in a grit blasting machine (Model MB1000 available from Comco Inc, Burbank, Calif.). The frame was then gently slid up a tapered mandrel until it achieved a functional size of approximately 6mm.

[0096] The frame and mandrel were then subjected to an initial thermal treatment to set the geometry in an initial, tapered (conical) configuration in an air convection oven (Carbolite Corporation, Sheffield, England). The frame was quenched in ambient temperature water and removed from the mandrel, resulting in a non-inverted frame.

[0097] Shown in FIG. 16 is the non-inverted frame 110 having support struts 34, a central collar 46, apexes 108, and radiopaque marker housings 106. The frame portion distal to the apexes 108 form a filter element support portion 32. The frame was then placed on a second mandrel, designed to constrain the outside of the frame while allowing the inversion of the tether elements back upon themselves. Once constrained in the proper configuration, the tooling and frame were subjected to a second thermal treatment to set the final frame geometry and to set the nitinol transition to an appropriate temperature. The resulting inverted frame is depicted in FIG. 17.

[0098] Shown in FIG. 17 is an inverted frame 112 having six looped support struts 34a, apexes 108, radiopaque housings 106, and an integral central collar 46. The frame portion distal to the apexes 108 form a filter element support portion 32.

[0099] One skilled in the art will appreciate that variances in the filter frame material(s), dimensions, geometry, and/or processing can all be made to create alternate embodiments with varying desirable properties. For example, the relative position of the central collar 46 to the apexes 108 can be varied according to FIGS. 5C and 5D.

[0100] The frame (now at functional size and preferred geometry) was then lightly coated with fluorinated ethylene propylene (FEP) powder (e.g., FEP 5101, available from DuPont Corp, Wilmington, Del.) by first stirring the powder in a kitchen blender (Hamilton Beach Blendmaster) after the powder was mixed into a "cloud," the frame was lowered into the blender for approximately 5 seconds (enough time for FEP to build up onto the surface of the frame). The frame, coated with FEP powder, was placed in an air convection oven (Grieve Oven, The Grieve Corporation, Round Lake, Ill.) set at 320.degree. C. for approximately one minute followed by air cooling to room temperature.

[0101] A typical filtering media was made by laser perforating one layer of a thin, polytetrafluoroethylene (PTFE) membrane using a 10-watt CO.sub.2 laser. The membrane thickness measured about 0.0002" (0.005 mm) and had tensile strengths of about 49,000 psi (about 340 KPa) in a first direction and of about 17,000 psi (about 120 KPa) in a second direction (perpendicular to the first direction). The tensile measurements were performed at 200 mm/min. load rate with a 1" (2.5 cm) jaw spacing. The membrane had a density of about 2.14 g/cm.sup.3. The laser power and shutter time parameters were adjusted to allow the laser to consistently create uniform 0.004" (0.1 mm) diameter holes in the membrane. The hole pattern geometry was then adjusted to create a pattern with uniform hole size, uniform hole spacing, and uniform strength throughout the pattern. This perforated pattern was then folded on itself and heat-sealed using a local heat source (Weber soldering iron, EC2002M, (available through McMaster Carr, Santa Fe Springs, Calif.)) into a pattern which would result in a conical shape. The conical flat pattern was then trimmed with scissors, inverted, and mounted upon the FEP powder coated NiTi frame and attached though the application of localized heat (the heat causing the FEP coating on the frame to re-melt and flow onto the surface of the filter sack thus providing a biocompatable thermoplastic adhesive).

[0102] A guide wire component was then inserted into the collar end of the frame and a small amount of instant adhesive (Loctite 401, Loctitie Corp, Rocky Hill, Conn.) was applied and dried to adhere and create a smooth transition from the guide wire to the outer diameter (OD) of the frame collar. One skilled in the art will realize that attachment of the filter to the guide wire could be accomplished by adhesion, welding, soldering, brazing, a combination of these, or a number of other methods.

[0103] The resulting embolic filter is as shown and described above with respect to FIG. 1 et seq.

[0104] A further embodiment of the present invention is illustrated in FIGS. 18A through 18C. In this embodiment the filter assembly 30 includes a frame 31 that is slidably mounted to the support wire 36. This attachment may be accomplished through a variety of means, including by providing a collar 46 that is sized slightly larger than the support wire 36 to allow the collar to move relative to the support wire when in use. Stops 114a, 114b are provided on the support wire 36 to limit the range of relative movement between the filter assembly 30 and the support wire 36. Constructed in this manner, the filter assembly 30 has exceptional longitudinal compliance relative to the support wire in that the support wire can freely move between the stops 114 without translating longitudinal or rotational movement to the filter assembly. The full range of proximal and distal movement of the filter assembly 30 relative to the stops 114 is shown in FIGS. 18B and 18C.

[0105] While particular embodiments of the present invention have been illustrated and described herein, the present invention should not be limited to such illustrations and descriptions. It should be apparent that changes and modifications may be incorporated and embodied as part of the present invention within the scope of the following claims.