Surgery – Instruments – Internal pressure applicator
Reexamination Certificate
2000-07-05
2002-05-21
Recla, Henry J. (Department: 3731)
Surgery
Instruments
Internal pressure applicator
C128S899000
Reexamination Certificate
active
06391045
ABSTRACT:
This invention relates to blood filters, and more particularly to filters designed to be implanted in a human vena cava and the like.
BACKGROUND OF THE INVENTION
Vena cava filters are designed to capture emboli and prevent them from migrating via the blood stream into the pulmonary arteries. A vena cava filter is typically placed via a catheter inserted through a puncture in a vein. For insertion, the filter is collapsed within the catheter and is released after the catheter has accessed the vena cava.
Known vena cava filters in collapsed form have required relatively large diameter catheters and correspondingly large puncture openings which has limited the access point generally to the largest veins, i.e. the femoral and jugular veins. The relatively large puncture wound has at times produced complications.
SUMMARY OF THE INVENTION
The present invention provides filters of small collapsed construction that are self-centering in the human vena cava over the considerable range of diameters of vena cava that exist. The invention also provides a high degree of consistency and repeatability in placement of the filter and secure anchoring of the filter to the vein wall to ensure no movement, particularly during the acute phase, until tissue growth over the anchors occurs to make the filter more secure.
The invention has various aspects which individually contribute improvement, and which, in select combinations, enable a smaller collapsed form and improved performance to be achieved.
Specifically, in one important respect, a vena cava filter is provided which, by separation of the filtering and anchoring functions into two or more sets of legs or struts, enables small diameter collapse of each set, in a construction which is desirably short and in which the axially spaced wall contact of the sets achieves self-centering over a wide range of vena cava sizes. Secure anchoring is also achieved at a precise location against movement in either direction as a result of firm engagement of the anchoring devices.
According to one principle of the invention a set of filter-wires is provided, which is to achieve the clot capturing function, capable of deploying over a wide range of cone angles dependent upon the size of the vena cava. These filter-wires extend generally upstream from a central region of connection, to wall-engaging free ends. The filter-wires of the set desirably have a general helical matching configuration that presents an effective clot-capturing aspect, in a construction that is readily collapsible into a small compass. From the axis also extends a collapsible strut structure which supports wall-engaging anchors or projections that securely engage the vessel wall at a location or locations spaced axially from the region of contact of the free ends of the filter-wires. Because nearly all of the filtering action is accomplished by the set of helical filter-wires, the design of the strut structure need not deal with its filtering aspect. While other cross-sections are operable in certain circumstances, the struts are preferably of rectangular transverse cross-section, i.e. of strip form, the long dimension of this cross-section arranged circumferentially, and the struts extend at, effectively, a steeper angle relative to the longitudinal axis than do filter-wires. This steepness favorably affects their force-applying capability at the vena cava wall. Other strut cross-sections including oval and even circular can, however, be employed under certain circumstances.
The strut structures in certain preferred embodiments diverge to their wall-contacting points in the opposite axial direction to that of the filter-wires in order to achieve the self-centering effect. Because of the strip-form construction they can readily support multiple anchors or projections along their respective lengths in the outer regions to provide firm anchoring capability in both small and large vena cava. In another preferred form, the strut structure extends in the same axial direction as does the filter wire structure, but at a steeper effective angle to achieve firm anchoring at a location spaced axially from the wall contact region of the filter-wires. Again this structure achieves a secure self-centering function over a wide range of vena cava sizes. The self-centering performance of preferred embodiments is assisted by employment of linear axially parallel wall-engaging elements supported by the strut structure. These are particularly beneficial in embodiments in which the strut structure diverges in the same direction as the filter-wires, but also have applications in a “ski-like” single support point configuration in which the strut structure diverges in the opposite direction from that of the set of filter-wires.
A parallelogram-like strut support of opposite ends of linear wall-engaging elements is an important feature in certain preferred embodiments. It enables the linear wall elements to maintain their parallel relationship to the axis of the filter, thus centering the filter over a range of sizes. This novel parallelogram support, while contributing significantly to the performance capability in combination with one of more sets of helical filter-wires, also has merit in its own right in which the support struts are constructed and arranged themselves to have a filtering function, or in which such strut structure is combined with other filtering arrays.
While presently preferred to be constructed of elastic metals such as nickel titanium alloy operating in the linear portion of the stress/strain curve, other materials can be used to advantage. Other materials of metallic or polymeric nature, including super-elastic metal, shape memory metal, and newly developing materials, may be used to advantage. Surface treatments of the filter-wires and supports can contribute to their effectiveness. Following the concepts provided herein, it becomes possible to form vena cava filters sufficiently small that in certain cases they may be introduced less invasively through smaller veins when access to the femoral or jugular vein is not possible.
These and other objects and features of the invention will be understood from the following summary of certain specific features of the invention and from the detailed description of presently preferred embodiments in connection with the drawings.
According to one aspect of the invention, there is provided a vascular filter for placement in a blood vessel for preventing the movement of emboli in the blood stream of a human. The filter includes a set of filter-wires that diverge from a central region in a given direction along the blood vessel forming an emboli-capturing array, the filter-wires having portions that engage the vessel wall, and an anchoring assembly defined by at least one set of struts joined centrally with said set of filter-wires. Portions of the anchoring assembly are constructed and arranged to engage the wall of the blood vessel in a manner anchoring the filter in position, the region of the anchoring being spaced from the region of contact of the set of filter wires with said vessel wall.
In preferred embodiments, the anchoring assembly includes anchoring formations supported by the struts and disposed for engagement with the walls of the blood vessel, each of the formations comprising at least one pointed projection to engage wall tissue and anchor the strut thereto.
In certain preferred embodiments each anchoring formation comprises at least a pair of pointed projections, the projections of the pair being oriented in opposite directions along the blood vessel, each being angled to penetrate wall tissue, the pair being effective in resisting dislodgement of the strut in either direction along the vessel. Also, in preferred embodiments the wall-engaging formations supported by the struts are constructed and arranged to maintain generally linear contact with the vessel walls.
In preferred embodiments of this aspect of the invention the filter-wires of the set are helically configured and arranged to form an effective clot-capturing array that
Kim Hannah S.
Nott Sepideh H.
Sandock David L.
Boston Scientific Corporation
Crompton Seager & Tufte LLC
Lewis William W.
Recla Henry J.
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