The present invention relates to medical filters which are intended to be placed inside a blood vessel or other body passage for the purpose of intercepting thrombus or other particulate matter.
Medical filters, including vena cava filters are generally known and are used to intercept unwanted particulate material in blood vessels and the like. It has been found that certain features are desirable in such filters. It is desirable that the filter be designed so that it can be emplaced with minimal trauma to the patient as by percutaneous delivery. It is also desirable that the filter be of a design which can adapt or adjust to the size of the vessel. To function satisfactorily in a blood vessel, a filter must be stable and effective to entrap thrombus, clots or other dangerous coagulations while allowing free flow of blood in the vessel. In some cases it is desirable to have a filter which can be inserted in a vessel for longer term emplacement, i.e. beyond two weeks, and then be removed with minimal trauma to the vessel wall.
While medical filters such as vena cava filters have been known and used for several years, there remains room for improvements in their designs and methods of emplacement and retrieval. Conventionally, such filters are delivered in a compressed form in the lumen of a delivery catheter and are retrieved by using a snare to withdraw the filter into the lumen of a retrieval catheter. However, difficulties continue to be encountered with presently known filters and there remains room for improved designs of filters and their methods of delivery and removal. In particular, there remains a need for filters with improved implantation and retrieval characteristics.
Accordingly, the present invention provides a medical filter which can be inserted in a body passage for a long period of time and then removed if desired with minimal trauma to the cells of the wall off the body passage. The filter of the present invention can be emplaced and retrieved from either femoral or jugular approaches. Furthermore, the design is practical for manufacture and can be economically made.
Further understanding of the present invention will be had from the following description taken in conjunction with the accompanying drawings and appended claims.
In accordance with the present invention, a medical filter for placement inside a body passage such as a vessel comprises:
In accordance with a preferred method of retrieval of the present invention, the medical filter of the present invention is retrieved by steps of:
The following description of the preferred embodiment of the present invention is intended to be merely illustrative in nature, and as such, is not intended to limit in any way the present invention, its application, or uses. Numerous modifications may be made by those skilled in the art without departing from the true spirit and scope of the invention, for example, the preferred embodiment of the present invention is shown in use in a vein but may also be used in other vessels of body passages.
Now referring to
First filter half 14 has a radially centrally located docking station 18 with a plurality of struts 20 extending generally radially outwardly and axially from docking station 18. Struts 20 connect or are integrally formed from one piece with generally parallel longitudinally extending legs 22. Legs 22 have free ends 24 and struts 20. Legs 22 define a first filter basket 26 with its open end open to the left as viewed in
Second filter half 16 has a collar 34 with a plurality of struts 36 extending generally radially outwardly and axially from collar 34. Struts 36 connect or are integrally formed from one piece with generally parallel longitudinally extending legs 38. Legs 38 have free ends 40 and struts 36 and legs 38 define a second filter basket 42 with its open end open to the right as viewed in
Filter baskets 26 and 42 act in opposition to flow of blood through blood vessel 12 and function to trap thrombus in the blood flowing therethrough. Filter halves 14 and 16 of Filter 10 are shown to be generally symmetric in form although it will be appreciated by those skilled in the art that asymmetric forms of filter halves 14 and 16 are within the broad scope of the present invention so long as their form does not interfere with their function as described hereinafter. For example, filter half 14 may have more or fewer legs 22 and/or struts 20 than filter half 16. Of course, filter halves 14 and 16 are not analogous with respect to docking station 18 and stop 28 of first filter half 14 or collar 34 and retrieval hook 44.
Each leg 22 and 38 extends, when not compressed, generally parallel to the longitudinal axis of filter 10, i.e., axially, and is not connected to any strut near blood vessel 12. Thus, each free end 24 and 40 of each leg 22 and 38 may become encapsulated by endothelium cell growth but no strut poses a substantial mechanical interference with the cell growth so as to make it difficult to retrieve filter 10 when retrieved in accordance with the method of this invention. Furthermore, legs 22 and 38 extend in opposite directions to thereby provide stability to filter 10 and resistance to migration of filter 10 in blood vessel 12 in either axial direction Of course, each filter half 14 and 16 is individually freely movable in opposite axial directions for retrieval as provided in the method of the present invention. Thus, in accordance with the present invention, the long narrow legs 22 and 38 stabilize filter 10 without becoming permanently embedded in the vessel wall by endothelium cell growth. While legs 22 and 38 may become covered with cell growth, the shape of the legs and their method of recapture allows the legs to slide out of the cell lining much like a needle would move through a vessel wall. There are no strut connections that connect the ends of legs 22 or 38 to each other at their free ends 24 and 40. Thus each leg 22 and 38 can easily slide out of the cell lining.
Filter 10 may be made of any suitable material and by a variety of methods. For example, Nitinol, stainless steel, elgiloy, cobalt chromium, or suitable polymeric material are suitable materials. Suitable methods of manufacture include cutting a pattern into a tube to enable expansion of the tube into the desired body and struts. Another suitable method is to form the struts and body from separate strips or wires and then to join the respective parts together by suitable methods which are well known in the art. Other materials may be used so long as the material has the desired characteristics of strength, resilience, flexibility, biocompatibility and endurance and is suitable for the particular manufacturing technique employed. It is, of course, required that the material employed be capable of expanding to the desired shape upon ejection from the delivery catheter. Thus, the material must also be sufficiently resilient to accomplish both compression in the delivery catheter and expansion upon ejection from the catheter.
Filter 10 is intended to be initially deployed compressed in a delivery catheter. Referring to
Having described the structure of filter 10, a preferred embodiment of the present invention, further understanding of the unique character and advantages of the present invention will be had by an understanding its method of retrieval.
Now referring to
As illustrated in
Thus, during retrieval of filter 10, first the proximal half of the filter is forced into the inner diameter of the distal half of the filter. As the proximal half end is fully recaptured it folds into the distal implant inner diameter and a stop is reached. The stop leg does not touch the lumen wall, it is shape set to extend to the middle of the implant or lumen. The legs of the proximal half slide out of the vessel lining, as the proximal half is recaptured. Once the proximal half is recaptured the snare pulls the distal (with the recaptured proximal half) inside the catheter.
A filter made in accordance with the present invention is retrievable at any time following implantation and may be implanted and retrieved from either femoral or jugular approaches.
The foregoing description of the preferred embodiments of the present invention is intended to be merely illustrative in nature, and as such, is not intended to limit in any way the present invention, its application, or uses. Numerous modifications may be made by those skilled in the art without departing from the true spirit and scope of the invention. It will be appreciated by those skilled in the art that the present invention is subject to variations and modifications. For example, the filter may be cut from a single tube and have end rings which are integral, i.e., one piece, with the spine and struts. The end rings may be tubular or cut into a serpentine pattern to allow the end rings to expandable to a larger diameter and subsequently compressible to a smaller diameter. This feature allows for very low profile filters when in the compressed stateāan obvious advantage for insertion and removal. Of course, the filter may be tube-based or wire based or a combination.