Patent Application
20050251198
The invention relates generally to intravascular filter membranes and methods of their formation. In particular, the invention relates to methods of molding intravascular filter membranes having a plurality of integrally formed apertures.
Heart and vascular disease are major problems 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.
Occluded, stenotic or narrowed blood vessels may be treated with a number of relatively non-invasive medical procedure 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 in the vessel is opened. During an atherectomy procedure, the stenotic lesion may be mechanically or otherwise cut away from the blood vessel wall using an atherectomy catheter.
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. During angioplasty procedures, stenotic debris may also break loose due to manipulation of the blood vessel.
Because of this debris, a number of devices, such as intravascular filters, have been developed to filter out debris. A need remains for improved intravascular filters and filter membranes. A need remains for improved methods of manufacture of intravascular filters and filter membranes.
The present invention is directed to methods of molding intravascular filter membranes, the resulting intravascular filter membranes having a plurality of integrally formed apertures, and filters utilizing such filter membranes.
Accordingly, an example embodiment of the invention can be found in a method of forming a filter membrane using a mold assembly. The mold assembly includes a mold having a mold surface and a die having a die surface. The mold assembly includes a plurality of protrusions that extend from at least one of the mold surfaces or the die surface. A molten material is placed within a portion of the mold, and the die is then inserted into the mold such that the protrusions span a distance between the die surface and the mold surface. The molten material is allowed to solidify, thereby forming a filter membrane that includes a plurality of integrally formed apertures.
Another example embodiment of the invention can be found in an assembly adapted for forming a filter membrane. The assembly includes a mold having a mold surface that defines an at least partially conical cavity. A plurality of protrusions extend outwardly from the mold surface, each of the protrusions having a protrusion length. The assembly also includes a die that has a die surface that is complementary to the mold surface and is configured such that when the die is inserted into the mold, the protrusions extending from the mold surface contact the die surface.
Another example embodiment of the invention can be found in a filter membrane that is formed by a particular process. A mold having a mold surface and a plurality of protrusions extending outwardly from the mold surface is provided. A complementary die having a die surface is also provided. A molten material is provided within a portion of the mold and the die is extended into the mold such that the protrusions contact the die surface. The molten material is allowed to solidify, thereby forming a filter membrane having a plurality of integrally formed apertures.
Another example embodiment of the invention can be found in a filter assembly that includes a support loop and a filter membrane having a proximal region and a distal region. The support loop is integrally molded into the proximal region of the filter membrane, and the filter membrane includes a plurality of integrally formed apertures. A distal waist is integrally molded into the distal region of the filter membrane.
The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:
For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.
All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure.
The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).
As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
The following description should be read with reference to the drawings wherein like reference numerals indicate like elements throughout the several views. The drawings, which are not necessarily to scale, depict illustrative embodiments of the claimed invention.
In some embodiments, the filter membrane 12 can be formed from at least one of polyether block amide, olefin/ionomer copolymers, nylon, polyurethane, polyethylene terephthalate, polyvinyl chloride, polyethylene naphthalene dicarboxylate and mixtures or copolymers thereof.
The filter membrane 12 can be porous, having pores 14 that are configured to permit blood flow while retaining embolic material of a desired size. The filter membrane 12 can have a mouth 16 and a closed end 18 and is capable of moving between an open state and a closed state. The mouth 16 can be sized to occlude the lumen of the body vessel in which the filter may be installed, thereby directing all fluid and any emboli into the filter with emboli retained therein.
A support hoop 20 can be attached to the filter membrane 12 at or proximate to the mouth 16. The support hoop 20 can be attached to the filter membrane 12 through melt bonding or other suitable means. In some embodiments, as discussed in greater detail hereinafter, the support loop 20 can be integrally molded within the filter membrane 12. The support hoop 20 has an expanded state and a compressed state. The expanded state of the support hoop 20 is configured to urge the mouth 16 to its full size, while the compressed state permits insertion into a small lumen.
The support hoop 20 can be made from a flexible metal such as spring steel, from a super-elastic elastic material such as a suitable nickel-titanium alloy, or from other suitable material. The support hoop 20 can be a closed hoop made from a wire of uniform diameter, it can be a closed hoop made from a wire having a portion with a smaller diameter, it can be an open hoop having a gap, or it can have another suitable configuration.
A strut 22 can be fixedly or slideably attached to and extend from the support hoop 20. An elongate member 24 can be attached to and extend from the strut 22. The elongate member 24 can be attached to the strut 22 at an angle or the strut 22 can have a small bend, either at a point or over a region. The strut 22 can be attached to the support hoop 20 at a slight angle such that when the elongate member 24, the strut 22, and the support hoop 20 are in an unconstrained position, the elongate member 24 can generally extend perpendicular to the support hoop 20.
In the unconstrained position, the elongate member 24 can also lie along an axis which passes through the center of the region created by the support hoop 20. This may help position the support hoop 20 in contact with the wall of a vascular lumen or it may help in enhancing predictability or reliability during deployment. In some embodiments, the elongate member 24 can terminate at the strut 22. In other embodiments, the elongate member 24 can extend through the filter membrane 12, as shown. Whether or not the elongate member 24 extends through the filter membrane 12, it may be fixedly or slideably/rotatably attached to the filter membrane 12.
The filter membrane 12 can include a waist 26 at a closed end 28. In some embodiments, the waist 26 can be integrally formed with the filter membrane 12. In other embodiments, the filter membrane 12 can be further processed to form the waist 26. In some embodiments, integrally forming the waist 26 with the filter membrane 12 can reduce the outer diameter of the filter device when in a compressed state, increase the reliability and uniformity of the bond between the filter membrane and the elongate member, and reduce the number of steps or components needed to form the filter device.
The waist 26 is a region largely incapable of moving between two states and having a lumen of substantially constant diameter therethrough. The elongate member 24 can extend through and be bonded to the waist 26. This bonding can be heat bonding such as laser bonding, or may be an adhesive or other suitable means.
In other embodiments, the protrusions 40 can be separately formed and then mechanically, thermally or adhesively secured to either the mold surface 34 or the die surface 38. In some embodiments, if the protrusions 40 are formed independently of either the mold 32 or the die 36 to which they will be secured, the protrusions 40 can be attached to either the mold surface 34 or the die surface 38 using an adhesive such as. In other embodiments, the protrusions 40 can be thermally or sonically welded to either of the mold surface 34 or the die surface 38. In some embodiments, the protrusions 40 can be threadedly secured to either of the mold surface 34 or the die surface 38.
The protrusions 40 can be formed having a variety of geometries. In some embodiments, at least some of the protrusions 40 can be cylindrical in shape. In some embodiments, all of the protrusions 40 can be cylindrical. Other suitable geometries include protrusions 40 having an oval, square, rectangular or polygonal cross-section profile. In some embodiments, the protrusions 40 will be cylindrical with a length that ranges from about 0.001 inches to about 0.100 inches and a diameter that ranges from about 0.0005 inches to about 0.0010 inches. The length of the protrusions 40 can, in some embodiments, determine the final thickness of the filter membrane 12.
In some embodiments, at least some of the protrusions 40 can extend from either the mold surface 34 or the die surface 38 in a direction that is substantially perpendicular to either of the mold surface 34 or the die surface 38. In some embodiments, all of the protrusions 40 can extend perpendicularly.
As noted, the mold assembly 30 includes a plurality of protrusions 40. The number of protrusions 40 provided in the mold assembly 30 can vary, depending on the intended use and overall size of the filter membrane 12. For example, if the filter membrane 12 is intended to be used in a portion of a patient's vasculature that has proportionately greater blood flow, it can be advantageous to provide a greater number of pores 14 (
The mold 32, the die 36 and the protrusions 40 can each be formed of any suitable material that is sufficiently stable and solid at the temperatures necessary to melt the material used to form the filter membrane 12. In some embodiments, the mold 32, the die 36 and the protrusions 40 can be formed of any metallic or high temperature polymer. Specific examples of suitable materials include polymers such as PEEK (polyether ether ketone) and metals such as steel and titanium. Especially useful materials include polyurethanes.
As noted, the protrusions 40 can extend from either of the mold surface 34 or the die surface 38.
In some embodiments, the free end 50 can at least partially contact the die surface 54 when the die 52 is fully extended into the mold 44. In some embodiments, there will be a small clearance between the die surface 54 and the free end 50 of each protrusion 48. The small clearance can be a distance sufficient to permit easy insertion of the die 52 into the mold 44, while not permitting molten material (discussed hereinafter) to set between the free end 50 and the die surface 54.
In some embodiments, the mold 44, the protrusions 48 and the die 52 can be made of materials having different compressive strengths. For example, if the protrusions 48 extend from the mold surface 46 as shown in
The mold 44, the protrusions 48 and the die 52 can be formed of any suitable material and having any suitable dimensions as discussed previously with respect to the elements of
As discussed above with respect to
To illustrate an embodiment in which the waist 26 is integrally formed, attention can be turned to
In particular,
In
Once the molten material 80 has been placed in the mold 70, the die 82 can be inserted into the mold 70 as illustrated for example in
In some embodiments, it can be useful to apply at least a portion of the molten material 80 to the die surface 84 prior to inserting the die 82 into the mold 70. A portion of the molten material 80 can be sprayed or coated onto the die surface 84. In some embodiments, the die 82 can be dipped into a supply of the molten material 80 prior to inserting the die 82 into the mold 70. Depending on the viscosity and other properties of the molten material 80, it may be useful to mechanically assist distribution of the molten material 80 within the mold 70. In some embodiments, it can be useful to agitate or spin at least one of the mold 70 and the die 82.
Once the molten material 80 solidifies, the mold 70 and the die 82 can be separated to free the resulting filter membrane 88 illustrated in
The filter membrane 88 includes a proximal region 90 and a distal region 92 including an integrally formed waist 94. The filter membrane 88 includes a plurality of integrally molded apertures 96 configured to selectively pass blood and other similar fluids while impeding undesirable material such as embolic material.
In some embodiments, it can be useful to provide one or more reinforcing ribs (not illustrated in
Moreover,
Previous to die insertion, a quantity of molten material 122 is placed within the mold 110, and a support loop 124 is placed into the mold 110. Once the die 118 has been fully inserted into the mold 110 (as illustrated) such that the die surface 120 is at least partially in contact with the free ends 116 of the protrusions 114, the molten material 122 flows upward to fill in the spaces between and around the mold surface 112, the die surface 120 and the protrusions 114. Once the molten material 122 solidifies, the resulting filter membrane 126 (
As illustrated in
In some embodiments, it may be useful for the apertures formed in the filter membrane to be more closely aligned with blood flow through the particular vasculature in which the filter membrane will be deployed.
In some embodiments, it can be useful for the apertures to have an ovoid cross-sectional profile. As a result of having an ovoid shape, the apertures can provide a more direct flow path through the apertures, even though the apertures may be formed perpendicular or substantially perpendicular to the surface of the mold.
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.
