Patent Document

FIELD OF THE INVENTION 
     The present invention relates to devices deployable in a vessel of the body such as a distal protection device deployable in a blood vessel. In one of its more particular aspects, the invention relates to the positioning of a guidewire or filter within human vasculature. 
     BACKGROUND OF THE INVENTION 
     Any intervention into human vasculature can give rise to the need for capturing and retrieving debris, such as grumous matter, emboli, or thrombi, from the affected vessel. Filters of various types have found use, for example, in trapping blood clots and other debris released into the bloodstream. Many filters, however, can be only partially effective in capturing the debris from surgical or catheterization interventions because deployment of the filter within the blood vessel may not provide complete filtration. That is, a filter may not effect filtration across the full cross-section of the blood flow through the vessel. This may result from failing to maintain an optimum fit of the filter within the vessel wall. Where a filter basket is used, another cause for concern is that the basket may not always be fully opened upon deployment within the vessel. 
     Specifically, filters are traps that have been designed to be used to collect dislodged matter, such as grumous matter, emboli or thrombi, during procedures such as stent installation in coronary saphenous vein grafts. Such filters or traps serve to provide protection from distal embolization that might result in a major adverse coronary event or other acute complication. Embolization of debris which might be released during such procedures and the resulting sequellae have been described in reports documenting major adverse cardiac event rates. Such events include acute myocardial infarction, revascularization and even death. 
     In order to address such acute embolic-related complications, distal filtration and protection devices have been developed. Such devices have been designed to work with existing interventional modalities. Such devices provide debris-filtering protection during invasive procedures and are intended to prevent complications of particulate embolization. 
     Such distal filtration and protection devices are typically deployed at a location along a vessel of the body at a desired location. Such deployment is performed by extending the device outwardly from the distal end of a catheter. In order to facilitate deployment, the device to be deployed typically has components made from a shape-memory or highly elastic material. Consequently, they are able to be collapsed within the catheter and, upon being urged outwardly beyond the distal end of the catheter, they reassume their uncollapsed shape. 
     Nevertheless, performance of such filtration and protection devices is less than perfect. One significant drawback is the general lack of rigidity of the device. While shape-memory materials are used and the device, once released from the catheter, tends to assume an intended uncollapsed configuration, the path of the vessel within which it is intended to be installed can be tortuous. The guidewire upon which the device is installed, therefore, tends to alternately engage opposite sides of the internal vessel wall as the vessel sinuates back and forth. This circumstance can cause the filtration/protection device to become at least partially collapsed between the guidewire and the internal vessel wall. This can result in at least a portion of the mouth of the device being closed and not fully covering the cross-section of the vessel. At least a portion of flow through the vessel can, then, bypass the device. 
     At least one other circumstance might result in the filtration/protection device becoming at least partially collapsed and a commensurate closure of at least a portion of the mouth of the device. When the guidewire carries a percutaneous transluminal coronary angioplasty (PTCA) balloon, stent or IVUS catheter, the radial position of the guidewire within the internal vessel can be altered from a desired generally central location. When the guidewire is displaced in this manner, the device can become partially collapsed, as discussed above, with commensurate partial or complete closure of the mouth of the device. Again, at least a portion of flow through the vessel can, thereby, bypass the device. 
     It is to these problems and dictates of the prior art that the present invention is directed. It is an improved distal protection device deployable in a blood vessel which facilitates maximization of desired filtration/protection. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a distal protection device which can be deployed to fit optimally within a blood vessel or other human vasculature. 
     Another object of this invention is to provide a distal protection device having a filter basket which is maintained in the fully opened configuration after deployment and during use. 
     Other objects and advantages of the present invention will become apparent from the following detailed disclosure and description. 
     The distal protection device of the present invention is provided with a self-expanding member, shown, in one embodiment, as a loop, that creates a radial force against a vessel wall to control the lateral position of a filter at a desired location in a blood vessel. The self-expanding loop functions to maintain open a proximal opening on a distal protection device such as a filter basket. The loop creates a radial force on the device&#39;s guidewire at or near the proximal end of the distal protection device, pushing the guidewire and filter carried by the guidewire against the vessel wall. Any debris formed as a result of proximal intervention, such as by PTCA or stenting, is thereby caused to enter the proximal opening of the basket. Prior to the present invention, the guidewire could be so positioned as to keep the proximal end of the filter basket from opening fully in various tortuous anatomy, resulting in failure to capture debris intended to be captured by the basket. 
     In one embodiment, the invention includes an element which serves to maintain the filter basket, when deployed, laterally on a defined side of the guidewire. Also included in this embodiment is a collapsible, quasi-rigid loop, or other type of spacer, carried proximate a mouth of the filter basket. The loop or other spacer member is positioned along the guidewire at or proximate the mouth of the filter basket so as to extend laterally on the same side of the guidewire as does the filter basket. Axial alignment of the loop or spacer and filter basket is achieved, in this embodiment, by rigidly fixing the spacer to the element which serves to maintain the filter basket on the defined side of the guidewire, or rigidly fixing the spacer to the guidewire by a separate securing element axially spaced from the filter basket affixation element, but with the spacer axially aligned with the filter basket. It will be understood that the specific loop or other spacer used is provided with a dimension on the side of the guidewire on which it deploys sufficient so as to engage an inner surface of the vessel at a particular circumferential location and, concurrently, urge the guidewire against the inner surface of the vessel at a location generally diametrically opposite that of the location engaged by the spacer. 
     The self-expanding loop can, as discussed above, be positioned on the guidewire at a location at or proximate the opening of the filter basket or embedded in the braid of the filter basket at or near its proximal end. It will be understood, in view of this disclosure, that the self-expanding loop or other spacer can be made, in one embodiment, to extend on the same lateral side of the guidewire as does the filter basket even when they both rotate concurrently. This can be accomplished by having the spacer attached to an element by which the filter basket is fixed to the guidewire, having the spacer interwoven into the mouth of the filter basket, or having the spacer tethered to the mouth of the filter basket so that, as the filter basket moves rotationally within the vessel of the body, the spacer will commensurately be moved so that substantial axial alignment is maintained. 
     The loop, while relatively rigid when expanded, is collapsible along with the filter basket for insertion into a delivery catheter. Insertion can be readily accomplished by either front-loading or back-loading. The loop expands upon deployment at a desired treatment location during a medical procedure such as a coronary intervention. 
     The loop can be constructed in a generally circular shape or can be formed in various “C”, “J” or spiral configurations, as desired. A continuous loop is preferred. 
     The loop may extend generally perpendicular to the guidewire when expanded, since, in that position, it exerts the greatest radial force, being deployed perpendicular to the vessel wall, and provides an optimal fit within the vessel. However, although perpendicular deployment is preferred, an adequate radial force can be generated by expansion of the loop at any angle between 45 degrees and 90 degrees relative to the axis of the guidewire. 
     The loop can be constructed of a single small diameter wire, such as a nitinol wire, or cable, coil, or stranded cable. It can be radiopaque or covered by a radiopaque material, if desired, to enable the viewing of the proximal opening of the distal protection device when deployed during a procedure. 
     The present invention is thus an improved apparatus for effecting optimum functioning of a distal protection filter basket. The spacer of the present invention makes it likely that the proximal opening of the distal protection device remains fully open while deployed. It expands and positions itself upon deployment. It does not interfere with the operation of the distal protection device, does not interfere with debris capture, and does not interfere with blood flow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view, partly in cross section, of one embodiment of the present invention, the inner wall of a blood vessel shown in phantom; 
     FIG. 2 is a perspective view, partly in cross section, of one embodiment of the present invention, showing the filter basket within a delivery catheter; 
     FIG. 3 is a view similar to FIG. 2, showing the filter basket partially removed from the catheter; 
     FIG. 4 is a view similar to FIGS. 2 and 3, showing the filter basket fully removed from the catheter; 
     FIG. 5 is a view similar to FIGS. 2,  3 , and  4 , showing the filter basket partially repositioned within the catheter; 
     FIG. 6 is a view similar to FIGS. 2,  3 ,  4 , and  5 , showing the filter basket further repositioned within the catheter; 
     FIG. 7 is a view similar to FIG. 4 illustrating a distal protection device, not employing the spacer in accordance with the present invention, deployed in a vessel traversing a tortuous course; 
     FIG. 8 is a view similar to FIG. 7 showing the effects of installing a spacer in accordance with the present invention; 
     FIG. 9 is a cross-sectional view illustrating the fitting of a loop spacer in a blood vessel; 
     FIG. 10 is a view similar to FIG. 9 illustrating the installation of a J-shaped spacer; 
     FIG. 11 is a view similar to FIGS. 9 and 10 illustrating a C-shaped spacer; 
     FIG. 12 is a view similar to FIG. 8 illustrating the installation of a spiral-shaped spacer; 
     FIG. 13 is a view similar to FIGS. 8 and 12 illustrating the installation of a continuous loop spacer interwoven into the mouth of the filter basket; and 
     FIG. 14 is a view similar to FIGS. 8,  12  and  13  illustrating the installation of a continuous-loop spacer which is tethered to the mouth of the filter basket. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings, a preferred distal protection device  10  of the present invention is shown in various stages of its use. FIGS. 1 and 4 show device  10  in its fully deployed state. In one embodiment, basket  12 , which, as seen in various figures, can be generally in the shape of a windsock, is attached to a guidewire  20 , passing through a placement device or stop (i.e., through the lumen of a tube  18 ), by an element  14  attaching basket  12  to guidewire  20  and holding basket  12  to prevent axial and revolutional movement with respect to guidewire  20 . Guidewire  20  is adapted for movement in either the distal direction, shown by arrow  24 , or the proximal direction, shown by arrow  32 . A ferrule  16  attached at the proximal end of basket  12  can enable movement of the proximal end of basket  12  along guidewire  20  in either the distal or proximal directions, as indicated by arrows  30 . When moved in a distal direction, it can, as best seen in FIG. 1, engage stop/tube  18 . It will be understood, however, that ferrule  16  can, if desired, be axially fixed on guidewire  20 . 
     A delivery catheter  22  is shown extending in the proximal direction relative to basket  12  with guidewire  20  passing through the lumen of catheter  22 . FIG. 4 also shows a spacer or loop  28  attached to the proximal end of basket  12  by means of ferrule  16 . In such an embodiment, loop  28 , along with basket  12 , can concurrently float relative to guidewire  20 . When ferrule  16  serves as an element to lock loop  28  with respect to the mouth of basket  12 , loop  28  is positioned so that it is substantially axially aligned with the mouth of the basket  12 . Because of the quasi-rigid nature of loop  28 , it will have the effect of urging ferrule  16  and guidewire  20  against inner wall  36  of the vessel  38 . Radial expansion of loop  28  will facilitate maintenance of the mouth of basket  12  fully opened. 
     It will be understood that, in certain embodiments, a separate element (not shown in the figures) could be used to maintain loop  28  proximate the proximal end of basket  12  and lock loop  28  in general axial alignment with basket  12 . When such a separate element is used, however, it would function to maintain loop  28  at a location about guidewire  20  so that loop  28  is generally axially aligned with basket  12 . Such embodiments can permit positioning of loop  28  at a location proximally spaced from ferrule  16 . Such spacing will enable the vessel of the body in which the basket  12  is deployed to taper to a normal diameter if the loop  28  has caused expansion. 
     Also contemplated by the invention are embodiments illustrated in FIGS. 13 and 14. FIG. 13 illustrates a filter basket  12  wherein the mouth of the basket is, in fact, defined by the loop  28 . In this embodiment, strands of the basket mesh  52  are interwoven about loop  28  to effectively integrate the loop  28  and basket  12 . As loop  28  engages inner wall  36  of vessel  38 , the mouth of the basket, commensurately, occupies substantially the full cross-section of vessel  38 . 
     FIG. 14 illustrates a basket  12  secured to guidewire  20  by means as previously discussed. Loop  28  is shown as being secured to guidewire  20  by an element  56  spaced axially along guidewire  20  from the proximal end or mouth of basket  12 . In this embodiment, element  56  may permit loop  28  to revolve about guidewire  20  independently of basket  12 . Tethers  54  are, however, employed to maintain a substantial axial alignment of loop  28  with the mouth of filter basket  12 . 
     As will be seen, the invention contemplates a number of methods of maintaining a desired relationship between the spacer and the filter basket  12 . What is significant, of course, is that there be a general axial alignment maintained between the two. 
     Referring now to FIG. 2, basket  12  is shown completely enclosed within catheter  22 . In FIG. 3 movement of guidewire  20  in the distal direction, indicated by arrow  24 , partially removes basket  12  from catheter  22  as shown by arrows  26 . In FIGS. 5 and 6 arrows  34  show partial retraction of basket  12  and loop  28  into catheter  22  by movement of guidewire  20  in the proximal direction indicated by arrow  32 . 
     FIG. 7 illustrates a distal protection device basket  12  attached to a guidewire  20  extending through a tortuous path of a blood vessel. The device illustrated in FIG. 7 is secured to guidewire  20  by means of element  14  and ferrule  16 , as was described with regard to FIGS. 1-6. In FIG. 7, however, a consequence of traversing the tortuous path of a blood vessel is illustrated. As seen, the guidewire  20  will tend to take the most direct route through the vessel and, alternatively, engage generally diametrically opposite sides of the inner wall  36  of the vessel  38 . As will be able to be seen in viewing FIG. 7, the filter basket  12  can become partially collapsed between the run of the guidewire  20  and the inner wall  36  of the vessel  38 . The possibility would then exist that debris in the stream of flow could bypass the filter basket  12 . 
     FIG. 8 illustrates how use of a loop spacer  28  in accordance with the present invention overcomes this problem. Loop  28  is fixedly attached to element or ferrule  16  so that it will be maintained on the same side of guidewire  20  on which filter basket  12  is maintained. Because of the quasi-rigid nature of the loop  28 , when it is deployed from catheter  22  it will engage a circumferential point on the inner wall  36  of the vessel  38  generally diametrically opposite the point of connection at ferrule  16 . The rigidity of loop  28  will effectively urge guidewire  20  against a circumferential point of inner wall  36 , opposite the location of engagement of the wall by the point of loop  28 , distal with respect to the point of loop  28  (that is, at ferrule  16 ). In consequence, filter basket  12  will be enabled to fully expand and, thereby, afford maximum protection. 
     FIG. 9 illustrates, in cross-section, the functioning of loop spacer  28  with respect to inner wall  36  of vessel  38 . FIGS. 10 and 11 show alternative embodiments of the spacer. FIG. 10 illustrates a generally J-shaped spacer  40 . FIG. 11 illustrates a generally C-shaped spacer  42 . As will be able to be seen in view of this disclosure, in both of these alternative embodiments, ferrule  16  and guidewire  20  will be driven against inner wall  36  of vessel  38  at a circumferential location generally opposite the location at which the spacer engages the wall  36 . As a result, operation of the filter basket  12  will be maximized. 
     FIG. 12 illustrates the functioning of a spiral-shaped spacer  44 . Spiral-shaped spacer  44  is shown as being connected, at a distal end thereof, to ferrule  16 . Such a connection would be substantially rigid so that the orientation of spacer  44  would be at a location so as to be generally axially aligned with the mouth of basket  12 . While, in embodiments wherein ferrule  16  can float axially, spacer  44  will commensurately be allowed to float axially, it will nevertheless be maintained revolutionally about guidewire  20  so as to afford the desired axial alignment with basket  12 . 
     FIG. 12 also illustrates another ferrule  48  which maintains the proximal end of spacer  44  at guidewire  20 . It will be understood that this ferrule  48  may be permitted to float in an axial direction also or be fixedly attached at guidewire  20 . 
     It will be understood that spiral spacer  44  in FIG. 12 can also be maintained, as is true in the case of other embodiments, rigidly with respect to guidewire  20  by elements separate from ferrule  16 . In such a case, this can be accomplished by rigidly securing the independent elements to the guidewire  20  or additionally, for example, tethering spacer  44  to the mouth of the filter basket  28 . 
     Other embodiments of the spacer are also specifically contemplated. For example, a continuous loop bent back on itself in a J-shape or C-shape are also intended to be encompassed within the invention. These particular embodiments are not illustrated in the drawing figures. 
     Although a preferred embodiment has been described, it will be appreciated that the description and disclosure in the instant specification are set forth by way of illustration and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention. Other embodiments can also be used to effect the objects of this invention.

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