Abstract:
A vascular filter for temporary or permanent implantation within a body vessel to filter particulates or thrombus in the blood stream, is capable of being converted some time after initial implantation into a tubular stent. In this configuration, the stent tends to hold the vessel open without any significant filtering effect. The convertible filter/stent may have a tubular metal mesh structure. Also, the device may form one or more filter lattices when in the filter configuration.

Description:
This application is divisional of U.S. patent application Ser. No. 09/342,876, which filed Jun. 29, 1999 claims the benefit of U.S. Provisional Application No. 60/090,968 filed Jun. 29, 1998. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     1. Technical Background 
     The present invention relates generally to medical devices, and more particularly to a vascular medical device. 
     2. Discussion 
     Vascular filters may be used for a variety of therapeutic applications, including implantable vena cava filters for capturing thrombus, or for distal protection during a vascular procedure. 
     Numerous different vascular filters are known of various types and designs. Prior filters are generally designed for either temporary use, such as may be provided on a catheter or provided with a mechanism for retrieving, the filter, or for permanent implantation. Either a permanent or a temporary filter maybe preferred for a specific situation, given the specific therapeutic conditions and the properties of the filter. 
     The present invention relates to a filter system including a vascular filter that can be placed inside a body passage or cavity, such as a blood vessel, through a catheter consisting of a tubular basic body with a distal end, a proximal end and a catheter lumen extending in between the ends. The vascular filter can be received in a compressed state inside the catheter lumen, and the catheter is provided with an ejection device which can be used to eject the vascular filter from the distal end of the catheter. 
     Vascular filters of the type that are implanted in a patient&#39;s body vessel are often made of an elastic or so-called “memory” material. The vascular filter is positioned by using an ejection member to push the filter from the open distal tip of the catheter into the blood vessel. 
     Many prior vascular filters expand resiliently from the compressed state inside the catheter lumen to an enlarged or deployed state, when released or deployed at the desired site for treatment. 
     However, it is desirable to provide a filter capable of being implanted for a selectively variable duration. For example, a vascular filter according to the present invention might have a design such that the filter is deployed through a catheter, and then the filter may be transformed at a selected time later to provide an open “through lumen”. 
     The present invention provides a novel vascular filter having a hybrid configuration, which is capable of being transformed to provide a through lumen at a time selected later. 
     Accordingly, it is desirable to provide a vascular filter capable of being implanted in an initial “filtering” configuration. The device may be monitored periodically for a time, until the physician decides to convert the implanted filter into a stent, for example. The filter is thus designed to selectively metamorphose into a second stent or graft configuration, providing a resilient tubular scaffold having and tending to maintain an open lumen through the body passageway. 
     Of course, the present invention relates broadly to vascular filters that are convertible into an open lumen device. The present invention may therefore be practiced in a multitude of different designs and variations which will occur to an average practitioner in the art. 
     These and various other objects, advantages and features of the invention will become apparent from the following description and claims, when considered in conjunction with the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic side elevational view of a convertible vascular filter, arranged according to one embodiment of the principles of the present invention; 
     FIGS. 2 and 3 are diagrammatic side elevational views of the convertible vascular filter, showing operation of the device during transformation; 
     FIG. 4 is a diagrammatic side elevational view of the vascular filter of FIG. 1, after transformation into a stent; 
     FIG. 4A is an axial longitudinal view of the stent of FIG. 4; 
     FIG. 5 shows a convertible vascular filter arranged according to the principles of the present invention in an initial filter configuration before being trasformed into a stent configuration; 
     FIG. 6 shows the vascular filter of FIG. 5, after a catheter has snared a proximal end hook of the filter; and 
     FIG. 7 shows the vascular filter of FIG. 6, after the proximal end of the filter has been opened, and illustrating the distal end hook being snared; 
     FIG. 8 shows the vascular filter of FIG. 7, after a catheter has snared a distal end hook of the filter; 
     FIG. 9 shows the convertible vascular filter of FIGS. 5-8, after being transformed into a tubular stent; 
     FIG. 10 is a partial view of the catheter and snare system of FIGS. 5-8 in greater detail; 
     FIG. 11 is a side elevational view of yet another embodiment of a convertible vascular filter, arranged according to the present invention; and 
     FIG. 12 is a side elevational view of the vascular filter of FIG. 11, showing the filter being converted into a stent by inflating the end portions with a balloon catheter. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description of the preferred embodiments of the present invention is merely illustrative in nature, and as such it does not 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. 
     Referring to the drawings, in FIG. 1 a vascular fiter  10  according to the present invention has been illustrated. According to the specific embodiment shown in FIGS. 1-4, the filter  10  has several longitudinal ribs  12  supporting a first and second filter element or lattice  14  and  16 . For the sake of drawing clarity, all of the ribs and the wires of filter elements have not been illustrated. Of course, there may be many filter elements or lattices, arranged in whatever preferred design is selected. In the arrangement shown in FIGS. 1-4, the filter elements  14  and  16  have a minimal number of converging wires. 
     One benefit of a design having more than one filter element coupled by longitudinal ribs is that the vascular filter  10  tends to deploy and align itself properly with the axis of the body passage or blood vessel. 
     In addition, the filter may be provided with a set of circumferential resilient supports, adapted to both hold the vascular filter in place, and also to ultimately hold open the body passage when the filter is converted into a stent. 
     As shown in FIG. 1, the filter elements  14  and  16  are held together by removable clamps  22 . The clamps  22  are locked by pins  26 , and both the pins  26  and clamps  22  have removal hooks  18  and  20  attached. 
     Before the filter is delivered and deployed in the patient&#39;s body, it is first loaded into a delivery catheter. In the distal tip of the catheter, at least one vascular fiter is initially arranged in a compressed state. As an alternative, it is also possible that the filter is pushed along the entire length of the catheter from its proximal end to its distal end, after the catheter distal end has been advanced to the desired position. Preferably the filter is packed, in a compressed state, in transport packaging forming a covering. The vascular filter may be ejected from the distal tip of the catheter by a pushing wire and introduced into a blood vessel. Due to the release from the radially compressive force imposed by the catheter lumen at the distal tip of the catheter, the vascular filter will tend to expand resiliently to obtain an expanded shape. Liquid inside the blood vessel can pass through in an unimpeded fashion, but thrombus will tend to be intercepted by one of the two filter lattices. 
     An advantage of this configuration is that it provides two filter elements for intercepting thrombus moving inside a blood vessel, which may be more effective than one. In addition, due to the configuration of the ribs which extend along the internal wall of the blood vessel, no free ends are presented which might damage the internal wall of the blood vessel. The configuration of the vascular filter according to the embodiment illustrated is consequently designed so as to minimize any distress or damage to the blood vessel inside of which it has been arranged. As filter elements have been arranged on either side of the ribs and consequently a symmetrical shape has been obtained, there is no difference in the performance of the filter regarding the direction from which this vascular filter  10  has been placed inside the blood vessel. 
     As has been illustrated, the grid shape of each of the filters is such that each of the ribs is connected with a number of the components of these filters. Furthermore, each of the ribs is connected with both filters on either side. Due to this configuration, an added safety feature is that the filter has a fail-safe design. 
     In addition, tipping over or misaligmnent of either filter is less likely due to the more or less tubular shape into which the ribs have been arranged so that positioning of the vascular filter  10  inside the blood vessel can take place with unprecedented stability and reliability. 
     The vascular filter  10  is preferably made of a very resilient material, like nitinol. Following the ejection from the distal tip of the catheter, filter  10  can expand and will be pressed against the internal wall of the blood vessel. 
     When the physician decides to transform the vascular filter into a stent, a catheter may be reinserted to a position near the filter. A guidewire with a hook can be used to pull the hook  20  attached to a locking pin  26 . With the removal of the locking pin  26 , the ends of the filter element collapse together, and the clamp  22  loses its purchase. The clamp  22  and locking pin  26  are then pulled by their attached hooks  18  and  20  out through the catheter, and the members forming filter elements  14  and  16  resiliently expand as in FIGS. 2-3. The resulting configuration is one of a resilient tubular stent  28  defining an open through lumen, as shown in FIGS. 4 and 4A. 
     The locking pin  26  and clamp 22  at the other end of the filter may be accessed and removed by approaching the filter from the other vascular direction. 
     Another embodiment of the present invention is illustrated in FIGS. 5-10. The vascular filter  30  is shown having a “lobster pot” configuration including a number of longitudinal ribs  42 , as well as transverse or circumferential support members. 
     A pair of hooks  38  and  40  are provided at the proximal and distal ends for the filter. The hooks  38  and  40  may of course be formed as a shaped extension of one of the filter wires or ribs  42 . As shown in FIG. 5, both hooks  38  and  40  preferably extend from a center region of a filter element  44  in a proximal direction. This feature offers the advantage of releasing both filter elements  44  into the stent configuration with a catheter approaching the filter from only one direction. 
     The wires of each filter lattice  44  are held together by closing wires  52 . 
     A catheter  32  and snare loop  34  may be used to convert the filter  30  into a stent configuration. After the snare  34  catches the proximal hook  38 , it pulls the hook  38  and the closing wires  52  at the ends of the filter wires into the distal end of the catheter  32 , as shown in FIG.  6 . Inside the catheter distal end are a series of cutting members or knives  50 , adapted to cut the closing wires  52  of the filter  30 . When the closing wires  52  are severed, the filter wires resiliently expand to form the desired tubular stent configuration. Of course, the hooks  38  and  40  are specifically arranged to be flat against the body vessel wall in the stent configuration. 
     As shown in FIGS. 7-8, the distal end of the filter is released in a similar manner, and the resulting stent is shown in FIG.  9 . 
     Yet another embodiment of the present invention is shown in FIGS. 11-12. The vascular filter is a hybrid combination of a central resilient “self-expanding” portion  54  flanked by two “balloon expandable” portions  62 . 
     The self-expanding central portion  54  always tends to resiliently expand, being made for example of nitinol, while the balloon expandable portions  62  tend to remain compressed until forcibly expanded, being made for example of stainless steel. 
     The self-expanding filter portion  54  is permanently affixed to the balloon expandable stent portions  62 , which may be affixed to a pair of hooks or loops  60  for maneuvering the device. The components may be affixed for example by welding. 
     When the physician decides to convert the filter into a stent, the balloon expandable stent or collar portions  62  are forcibly expanded such as by a balloon  66  of a balloon catheter  68 , as shown in FIG.  12 . 
     One advantage of the embodiment of a vascular filter according to the present invention is that the loop  60  may be used to later remove the vascular filter. Loops  60  can thus serve as a target for a hook-shaped extraction element, in order to remove the vascular filter. The hook-shaped extraction body (not shown) may engage the loop, and pull the entire vascular filter back into a catheter enveloping the extraction element. 
     After reading the above, many possible embodiments of a vascular filter that is convertible into a medical device forming an open lumen, other embodiments, and features will occur to one of ordinary skill in the field. All of these are to be considered as falling within the scope of the attached claims. It is for instance possible to use a vascular filter which has a different shape than the one described above. It is also possible to use a more conventional single vascular filter without the double filter feature. The vascular filter also does not need to comprise ribs extending in an axial direction in relation to the blood vessel. 
     It should be understood that an unlimited number of configurations for the present invention could be realized. The foregoing discussion describes merely exemplary embodiments illustrating the principles of the present invention, the scope of which is recited in the following claims. Those skilled in the art will readily recognize from the description, claims, and drawings that numerous changes and modifications can be made without departing from the spirit and scope of the invention