Inverted embolic protection filter

The present invention relates generally to the field of embolic protection devices. More specifically, the present invention pertains to embolic protection filters having improved blood perfusion characteristics.

Intravascular filters such as embolic protection filters are generally placed within a body lumen, such as an artery or vein, downstream of a therapeutic site to filter embolic debris from the blood stream. Examples of therapeutic procedures employing such filters include angioplasty, atherectomy, thrombectomy and stent placement. In a typical procedure, a guidewire is transluminally inserted into the patient and placed across the site of the lesion. An embolic protection filter is then advanced along the guidewire and placed distal the lesion. A therapeutic device such as a dilatation or atherectomy catheter is then advanced along the guidewire and placed proximal the therapeutic site to perform the procedure. The therapeutic device is then engaged, forcing the embolic debris to become dislodged from the walls of the vessel and flow downstream towards the distal vasculature, where it is collected and stored by the filter.

There are numerous types of interventional devices adapted to collect embolic debris released into the blood stream during a therapeutic procedure. Typically, these devices contain a mesh or microporous membrane attached to a support structure having struts, wires, and/or ribs that support the filter within a blood vessel when deployed. Generally, the shape of these filters include a proximal mouth or opening that tapers distally to a closed end portion. Examples of such configurations include baskets, parachutes, or sleeves. In a typical application, embolic debris enters the proximal end of the device, and flows distally where it is stored at the closed end portion of the filter.

Depending on the amount of embolic debris dislodged from the vessel wall, the embolic protection filter may become partially or fully occluded throughout the course of the therapeutic procedure. As a result of the buildup of embolic debris within the filter, the perfusion of blood through the filter diminishes over time.

The present invention relates generally to the field of embolic protection devices. More specifically, the present invention pertains to embolic protection filters having improved blood perfusion characteristics. In an exemplary embodiment of the present invention, an inverted embolic protection filter comprises a filter frame disposable about a guidewire, a support hoop coupled to a plurality of expandable struts adapted to expand in an outward direction within a body lumen, and an inverted membrane for filtering embolic debris, the inverted membrane having a tapered proximal section and an enlarged diameter distal section. The inverted membrane can be configured such that the perfusion of blood through the filter remains relatively constant irrespective of the amount of embolic debris collected therein.

FIG. 1 is a perspective view of an inverted embolic protection filter in accordance with an embodiment of the present invention showing the filter in a radially deployed position.

FIG. 1 is a perspective view of an inverted embolic protection filter 10 in accordance with an exemplary embodiment of the present invention. As shown in FIG. 1 , embolic protection filter 10 includes a filter frame 12 disposed about a guidewire 14 . Guidewire 14 has a proximal end 16 , a distal end 18 , and a distal stop 20 . Filter frame 12 comprises a first tubular member 22 disposable about guidewire 14 , and a second tubular member 24 disposable about guidewire 14 distal the first tubular member 22 .

In the exemplary embodiment illustrated in FIG. 1 , embolic protection filter 10 is slidably and rotationally disposed about guidewire 14 . The first tubular member 22 and second tubular member 24 each define a lumen (not shown) having an inner diameter that is slightly larger than the outer diameter of the guidewire 14 , thereby permitting the embolic protection filter 10 to freely slide and rotate about the guidewire 14 . An optional coating may be applied to the inner diameter of each tubular member 22 , 24 and/or the guidewire 14 to provide a smooth, lubricious surface to facilitate movement of the embolic protection filter 10 along the guidewire 14 . For example, a polymeric material such as polytetrafluoroethylene (PTFE) can be applied to the tubular members 22 , 24 and/or the outer surface of the guidewire 14 .

In an alternative implementation (not shown), embolic protection filter 10 may be secured to the guidewire 14 prior to insertion into the patient's vessel. In this configuration, the first tubular member 22 is secured to the guidewire 14 , whereas the second tubular 24 is movably disposed along the guidewire 14 . Attachment of the first tubular member 22 to the guidewire 14 may be accomplished by any number of suitable attachment means such as crimping, soldering, bonding, welding, brazing or any combination thereof.

Filter frame 12 can further include a support hoop 26 coupled to a plurality of self-expanding struts 30 . Each of the expandable struts 30 is attached at a proximal portion 32 to the support hoop 26 , and at a distal portion 34 to the second tubular member 24 . The self-expanding struts 30 are biased to self-expand in an outward direction, and can be utilized to deploy the support hoop 26 within a body lumen. In addition, the support hoop 26 may include a preformed shape that facilitates radial deployment (and subsequent removal) of the device within the lumen. For example, the support hoop 26 may include one or more reduced diameter portions disposed about its circumference that permit the support hoop 26 to easily fold or bend into a collapsed position during transport.

To bias the expandable struts 30 in an outward direction, each expandable strut 30 may be pre-formed using a bendable material such as stainless steel or platinum, or a super-elastic material such as nickel-titanium alloy (Nitinol). Nickel-titanium alloy is preferred for its ability to undergo substantial bending or flexing with relatively little residual strain. It is contemplated, however, that other suitable materials can be utilized to bias the expandable struts 30 in an outward direction.

Also attached to support hoop 26 are several optional retrieval struts 36 each having a proximal portion 38 and a distal portion 40 . The proximal portion 38 of each retrieval strut 36 is attached to the first tubular member 22 . The distal portion 38 of each retrieval strut 36 , in turn, is attached to the support hoop 26 . The retrieval struts 36 are utilized in the delivery and subsequent retrieval of the embolic protection filter 10 . As with the self-expanding struts 30 , the retrieval struts 36 are biased to self-expand in an outward direction when unconstrained, and provide additional structural support for the embolic protection filter 10 .

Coupled at a proximal end to the first tubular member 22 , and extending distally through the mouth formed by support hoop 26 , is an inverted membrane 44 . In the exemplary embodiment illustrated in FIG. 1 , inverted membrane 44 is substantially conical in shape, having a tapered proximal section 46 that extends distally to an enlarged diameter distal section 48 . The tapered proximal section 46 of inverted membrane 44 is attached to the first tubular member 22 . The enlarged diameter distal section 48 of inverted membrane 44 forms a fold or crease, wherein a length 42 of the inverted membrane 44 folds back and extends proximally towards the support hoop 26 .

Inverted membrane 44 can be comprised of a microporous membrane made from a polymeric material such as polypropylene (PP), polyvinylchloride (PVC), polyamide (nylon), polyurethane, polyester, polyethylene tetraphlalate, polyether-ether ketone (PEEK), polyether block amide (PEBA), polytetrafluoroethylene (PTFE) or any mixture, blend or combination thereof Alternatively, inverted membrane 44 can be formed of a mesh screen comprising several woven or braided wires. These woven or braided wires may be made of any number of suitable biocompatible materials such as stainless steel, nickel-titanium alloy or platinum.

Perfusion of blood through the inverted membrane 44 is accomplished through several openings or pores 52 formed in the mesh screen or microporous membrane. The openings or pores 52 are preferably adapted to filter embolic debris contained in the blood stream while substantially permitting the flow of blood therethrough.

In certain embodiments of the present invention, embolic protection filter 10 may include an anti-inflammatory agent to reduce damage to the patient's vascular tract caused during therapeutic the procedure. Examples of such anti-inflammatory agents include dexamethasone, prednisolone, corticosterone, budesonide, estrogen, sulfasalazine, and mesalamine or any suitable combination or mixture thereof. In other embodiments, the embolic protection filter 10 may contain an anti-thrombogenic coating to prevent the formation of clots within the vasculature. Examples of suitable anti-thrombogenic coatings include heparin (and derivatives thereof), urokinase and dextrophenylalanine proline arginine chloromethylketone.

In use, embolic protection filter 10 is advanced distally along guidewire 14 and placed distal a lesion or other occlusion within the patient's vessel. To facilitate transport of the filter 10 through the vessel, a delivery sheath 15 comprising a tubular member having a reduced profile and an inner lumen adapted to transport the embolic protection filter 10 in a collapsed position is advanced through the vessel along the guidewire 14 . A distal stop 20 disposed about the distal end 18 of guidewire 14 prevents distal movement of the device therebeyond. Once the delivery sheath 15 containing the collapsed filter 10 is in place distal the lesion, the delivery sheath 15 is retracted proximally, causing the embolic protection filter 10 to deploy within the vessel as shown in FIG. 1 . A therapeutic device such as an angioplasty or atherectomy catheter can then be advanced along the guidewire 14 and placed proximal the lesion. The therapeutic device is then engaged within the vessel, forcing the embolic debris to become dislodged and flow downstream towards the embolic protection filter 10 .

As the embolic debris enters the embolic protection filter 10 (as indicated by the arrow in FIG. 1 ), it is initially deposited on the inverted membrane 44 at or near the tapered proximal section 46 . At this location, the velocity of blood flow is generally greatest since it is located at or near the center portion of the vessel. The embolic debris is then deflected distally, where it becomes entrained at or near the fold or crease formed at the enlarged diameter distal section 48 . At the enlarged diameter distal section 48 , the velocity of the blood flow is generally less than at the tapered proximal section 46 since it is located at or near the vessel wall. Since the embolic debris collects at a location where the velocity of blood flow is generally less, the embolic debris entrained within the embolic protection filter 10 does not substantially interfere with the perfusion of blood through the inverted membrane 44 at or near the tapered proximal section 46 . As a result, the flow of blood through inverted membrane 44 remains relatively constant, irrespective of the amount of embolic debris collected by the embolic protection filter 10 .

To retrieve embolic protection filter 10 from the body, the delivery sheath 15 is advanced distally along the guidewire 14 until it is proximal the embolic protection filter 10 . Continued advancement of the delivery sheath 15 distally causes the portion of the inverted membrane 44 along length 42 to re-invert, allowing the inverted membrane 44 , support hoop 26 and support struts 30 to collapse inwardly within the lumen of the delivery sheath 15 . Alternatively, when the optional retrieval struts 36 are employed, continued advancement of the delivery sheath 15 against the retrieval struts 36 causes the support hoop 26 , support struts 30 and the retrieval struts 36 to collapse inwardly within the lumen of the delivery sheath 15 . Once collapsed, the delivery sheath 15 and embolic protection filter 10 containing the collected embolic debris can then be removed from the body.

Having thus described the exemplary embodiments of the present invention, those of skill in the art will readily appreciate that other embodiments may be made and used which fall within the scope of the claims attached hereto. Numerous advantages of the invention covered by this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many respects, only illustrative. Changes may be made in details, particular in matters of shape, size and arrangement of parts without exceeding the scope of the invention.