Surgery – Instruments – Internal pressure applicator
Reexamination Certificate
1998-01-16
2001-08-14
Recla, Henry J. (Department: 3731)
Surgery
Instruments
Internal pressure applicator
C606S159000
Reexamination Certificate
active
06273900
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to blood clot filtering.
BACKGROUND
Blood clots that form in the lower part of the body may migrate to the heart and may be subsequently pumped to the lungs. Small clots can be absorbed by the body without adverse effect. However, larger clots can interfere with the oxygenation of blood (e.g., on the order of 3 mm in diameter and 10-30 cm in length) and can possibly cause shock or sudden death.
Many transvenous filtering devices have been developed for installation in the vena cava to prevent especially large clots from reaching the lungs. These filters have fine wires positioned in the blood flow to catch and hold clots for effective lysing in the blood stream. Some of these devices are inserted into the vena cava by dissecting the internal jugular vein in the neck or the femoral vein in the groin, inserting a metallic capsule containing a filtering device to the proper position in the vena cava, and releasing the filtering device into the vena cava. More recently, filters have been designed for percutaneous introduction into the vasculature.
SUMMARY
In one aspect, the invention features a filter sized and constructed to be compressed and passed through the vasculature of a patient to be anchored against an inner wall surface of a blood vessel for capturing blood clots in a blood stream passing therethrough. The filter comprises: an anchoring portion comprising a generally cylindrical self-expanding body formed from resilient material, the generally cylindrical body having proximal and distal ends and defining an axial direction and having a structure of variable size diameter expandable from a low-profile compressed condition to a larger profile expanded condition, wherein the resilient material urges the generally cylindrical body to radially expand and to thereby apply anchoring radial force against the inner wall surface of the blood vessel; and a generally conical filtering portion axially aligned with the generally cylindrical body having an open proximal end coupled to the distal end of the anchoring portion and having an apical distal end, the anchoring portion and the filtering portion being substantially non-overlapping to achieve a low profile compressed condition for delivery of the filter through the vasculature.
Embodiments of the invention may include one or more of the following features. The generally conical filtering portion is preferably formed from a plurality of elongated strands arranged to form a generally conical structure to guide blood clots in the blood stream flowing there past to the apical distal end of the generally conical filtering portion for lysing. The elongated strands forming the generally conical filtering portion are preferably constructed and arranged to maintain a generally conical shape whether the anchoring portion is in a compressed condition or an expanded condition. The anchoring portion and the filtering portion are preferably constructed and arranged so that the proximal end of the filtering portion conforms to the shape of the cylindrical body of the anchoring portion. The elongated strands are preferably fixedly attached to one another only at the apex of the generally conical filtering portion. The elongated strands may be formed from nitinol (nickel-titanium alloy), plastically deformable material, temperature-sensitive shape memory material with a transition temperature around body temperature, or elastic material having a core formed from radiopaque material. The filter may be coated with a drug for in vivo compatibility. The resilient elongated strands preferably extend from the proximal end of the anchoring portion to the distal apical end of the filtering portion.
The elongated strands of the filtering portion may define a plurality of neighboring filtering cells. The neighboring filtering cells are preferably loosely coupled together at the respective areas of contact between neighboring cells. The neighboring cells are preferably coupled together by helical twisting of portions of respective elongated strands of neighboring cells. The portion of the twisted-together elongated strands are preferably capable of slight mutual separation to accommodate changes in the shapes of the cells from the expanded to the compressed conditions. The generally conical filtering portion preferably comprises at least two rings of cells, wherein the cells of each ring are of substantially equal size and are spaced substantially the same distance from the apical distal end of the filtering portion. The size of the cells in the rings is preferably smaller for cells closer to the apical distal end of the filtering portion than for cells located a greater distance from the apical distal end of the filtering portion.
The elongated strands of the filtering portion may be spirally arranged with respect to one another from the proximal end of the filtering portion to the apical distal end of the filtering portion. The elongated strands are preferably selected to have sufficient rigidity to maintain the generally conical shape of the filtering portion.
The self-expanding anchoring portion preferably comprises a ring of neighboring cells. The cells of the anchoring portion are preferably self-expanding. The cells of the anchoring portion preferably cooperate to urge the generally cylindrical body of the anchoring portion to radially expand from a compressed condition to an expanded condition. The neighboring cells of the anchoring portion are preferably fixedly coupled together at respective areas of contact. The cells of the anchoring portion are preferably formed from one or more resilient elongated strands. When the generally cylindrical body is in a compressed condition, the cells of the anchoring portion are preferably elongated in the axial direction.
In another general aspect, the invention features a blood clot filter comprising: an anchoring portion formed from resilient material having proximal and distal ends and having a generally circular transverse cross-section defining an axial direction, the anchoring portion further having a structure of variable size diameter expandable from a low-profile compressed condition to a larger profile expanded condition, wherein the resilient material urges the anchoring portion to radially expand and to thereby apply anchoring radial force against the inner wall surface of the blood vessel; a filtering portion axially aligned with the generally cylindrical body having an open proximal end coupled to the distal end of the anchoring portion; and one or more hooks fixedly coupled to the anchoring portion formed from compliant material having an original shape that bends under stress yet returns to its original shape when unstressed, said one or more hooks respectively tending to project from the anchoring portion at an acute angle with respect to the axial direction for engagement with a vessel wall, the one or more hooks further being deflectable toward the anchoring portion for achieving a low-profile.
Embodiments of the invention may include one or more of the following features. The hooks are preferably formed from nitinol. The hooks preferably preferentially bend toward and away from the vessel wall engaging portion. The hooks are preferably formed from flat nitinol wire having a width dimension and having a thickness dimension substantially smaller than the width dimension for achieving preferential bending; the flat nitinol wire being oriented so that the thickness dimension of the flat nitinol wire coincides with a radial direction of the anchoring portion. The hooks preferably preferentially bend toward and away from the vessel wall engaging portion.
Among the advantages of the present invention are the following. Because the anchoring portion and the filtering portion have constructions that are optimally designed for their respective functions, the filter can have a low profile while providing a robust design that can readily accommodate different vessel sizes. Furthermore, the anchoring portion serves to center the filtering portion. The filte
Kim Hannah S.
Nott Sepideh H.
Sandock David L.
Soun Naroun
Boston Scientific Corporation
Hoffman & Baron LLP
Ngo Lien
Recla Henry J.
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