Patent Publication Number: US-6902572-B2

Title: Anchoring mechanisms for intravascular devices

Description:
FIELD OF THE INVENTION 
     The present invention pertains to anchoring mechanisms for intravascular devices. More specifically, the present invention relates to anchoring mechanisms for limiting travel of an intravascular device along an elongated member disposed within a body vessel. 
     BACKGROUND OF THE INVENTION 
     Medical procedures to treat occlusive vascular diseases, such as angioplasty, atherectomy and stent deployment, routinely involve the insertion and subsequent removal of various intravascular devices. In an angioplasty procedure, for example, a physician will typically advance a guidewire having an attached embolic protection filter to a desired location within the body, and subsequently deploy a balloon catheter to dislodge embolic debris or thrombus from a lesion. In some instances, the physician may wish to deploy more than one device during the procedure. For example, if the first embolic protection filter becomes occluded with debris dislodged during the angioplasty procedure, the physician may wish to replace the occluded filter with a second filter while maintaining guidewire position. 
     SUMMARY OF THE INVENTION 
     The present invention relates to anchoring mechanisms for releasably securing an intravascular device to a guidewire disposed within the vasculature of a patient. In an exemplary embodiment of the present invention, an anchoring mechanism may comprise a leaf spring actuatable between an unlocked position and a locked position. The leaf spring may comprise a normally flat, flexible body having at least one opening configured to receive and grip the elongated member at one or more contact regions defined by the opening. In certain embodiments, the flexible body may comprise a first flat region, a second flat region, and a bend region therebetween configured to permit bending of the first flat region relative to the second flat region. In other embodiments, the flexible body may comprise a multiple leaf spring having several alternating bend regions connecting several flat regions together in alternating fashion. 
     The leaf spring may include one or more indentations to impart a particular degree of flexibility to the leaf spring. In certain embodiments, for example, the leaf spring may include an indentation region at or near each bend region to permit greater flexion of the leaf spring at the bend region and reduce the spring&#39;s profile. A proximal and/or distal flat region of the leaf spring configured to align perpendicularly to the elongated member may be employed to ensure proper alignment of the leaf spring along the elongated member. 
     In use, the leaf spring can be attached directly to an intravascular device, allowing the intravascular device to be releasably secured to the elongated member. Alternatively, the leaf spring can be formed as a separate member and used as a stopper mechanism to limit travel of the intravascular device along the elongated member. A locking tube slidably disposed about the elongated member may be utilized to actuate the leaf spring between the locked and unlocked positions within the body. In certain exemplary embodiments, the locking tube may include a bendable locking tab configured to permit the operator to withdraw the locking tube and engage the leaf spring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an anchoring mechanism in accordance with an exemplary embodiment of the present invention, wherein the anchoring mechanism comprises a single leaf spring; 
         FIG. 2  is a view of the leaf spring along line  2 — 2  in  FIG. 1 ; 
         FIG. 3  is a partial cross-sectional view showing the leaf spring in a unlocked position along the elongated member; 
         FIG. 4  is a partial cross-sectional view showing the leaf spring in a locked position along the elongated member; 
         FIG. 5  is a perspective view of an anchoring mechanism in accordance with another exemplary embodiment of the present invention, wherein the anchoring mechanism comprises a multiple leaf spring; 
         FIG. 6  is a partial cross-sectional view showing the multiple leaf spring in an unlocked position along the elongated member; 
         FIG. 7  is a partial cross-sectional view showing the multiple leaf spring in a locked position along the elongated member; 
         FIG. 8  is a partial cross-sectional view of an inner locking tube and delivery sheath in accordance with an exemplary embodiment of the present invention; 
         FIG. 9  is another partial cross-sectional view of the inner locking tube and delivery sheath of  FIG. 8 , showing the inner locking tube withdrawn proximally; 
         FIG. 10  is another partial cross-sectional view of the inner locking tube and delivery sheath of  FIG. 8 , showing the delivery sheath withdrawn proximally. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description should be read with reference to the drawings wherein like reference numerals indicate like elements throughout the several views. The detailed description and drawings illustrate exemplary embodiments of the claimed invention. The drawings, which are not necessarily to scale, depict several embodiments and are not intended to limit the scope of the invention. Although examples of construction, dimensions, materials and manufacturing processes are illustrated for the various elements, those skilled in the art will recognize that many of the examples provided have suitable alternatives that may be utilized. 
       FIG. 1  is a perspective view of an anchoring mechanism  10  in accordance with an exemplary embodiment of the present invention. Anchoring mechanism  10  comprises a leaf spring  12  having a number of openings  14 , 16  configured to slidably and rotationally receive an elongated member  18  such as a guidewire or guide catheter therethrough. Leaf spring  12  comprises a preset curved, flexible body  20  that can be deformed when the elongated member  18  is inserted through the openings  14 , 16  in an over-under configuration, and when a compressive force is applied to the ends of the leaf spring  12 , as indicated by arrow F in FIG.  1 . 
     Leaf spring  12  can be actuated between an unlocked position and a locked position to prevent travel of an intravascular device (not shown) along the elongated member  18 . Leaf spring  12  may be utilized as either a proximal or distal stop to prevent or limit movement of an intravascular device along the elongated member  18 , or can be attached to or formed integrally with an intravascular device and used as a means to directly secure the intravascular device to the elongated member  18 , as shown, for example, in FIG.  3 . In the exemplary embodiment illustrated in  FIG. 1 , leaf spring  12  is shown as a separate member configured to act as a proximal or distal stop to limit travel of an intravascular device (e.g. an embolic protection filter or probe) along the elongated member  18 . 
     Flexible body  20  may include a first flat region  22 , a bend region  24 , and a second flat region  26 . The first flat region  22  of flexible body  20  is distally sloped relative to the longitudinal axis of the elongated member  18 , and includes a first opening  14 . The second flat region  26  of flexible body  20 , in turn, is proximally sloped relative to the longitudinal axis of the elongated member  18 , and includes a second opening  16 . The first and second flat regions  22 , 26  of flexible body  20  are configured to bend or flex about bend region  24  when subjected to an inwardly directed force F acting parallel to the longitudinal axis of the elongated member  18 , orienting the first and second openings  14 , 16  in a direction that causes the leaf spring  12  to disengage from the elongated member  18 . 
     The leaf spring  12  may be formed of any number of suitable biocompatible materials, including metals, metal alloys, polymers, or combinations thereof. For example, leaf spring  12  may comprise a metal or metal alloy such as stainless steel (e.g. type 304 or 316), platinum, titanium, tantalum, or other suitable materials. Examples of suitable polymeric materials include polyethylene terapthalate (PET), polytetraflouroethylene (PTFE), polyurethane (Nylon) fluorinated ethylene propylene (FEP), polyurethane, polypropylene (PP), polyvinylchloride (PVC), polyether-ester, polyester, polyamide, elastomeric polyamides, block polyamide/ethers, polyether block amide (PEBA), silicones, polyethylene, polyether-ether ketone (PEEK), polyimide (PI), and polyetherimide (PEI). Polyether block amide (PEBA) is commercially available from Atochem Polymers of Birdsboro, Pa. under the trade name PEBAX. 
     In certain embodiments, leaf spring  12  may be formed of a superelastic or linear elastic material such as nickel-titanium alloy, allowing the leaf spring  12  to undergo substantial bending with relatively little strain. A leaf spring  12  comprising a superelastic material may permit greater flexion of the leaf spring  12 , particularly in applications where the leaf spring  12  is repeatedly bent between the locked and unlocked positions. 
     As further shown in  FIG. 1 , leaf spring  12  may have an undulating shape formed by an indented region  28  of the flexible body  20 . The reduction in width at the indented region  28  can be selected to impart a particular degree of flexibility to the leaf spring  12  at the bend region  24 , depending on the particular application. For example, the width of the flexible body  18  at the indented region  28  can be relatively small in comparison to the width of the first and second flat regions  20 , 26 , allowing greater flexion of the leaf spring  12  about the bend region  24 . 
       FIG. 2  is a view of the leaf spring  12  along line  2 — 2  illustrated in  FIG. 1 , showing an end view of the leaf spring  12  in the unlocked position. As shown in  FIG. 2 , opening  14  may be elliptical in shape, having a major axis A and a minor axis B. Two contact regions  30 , 32  on the major axis A of opening  14  are configured to contact the elongated member  18  in the locked position, but are sufficiently spaced apart such that, when the leaf spring  12  is longitudinally compressed, a small clearance  34  is formed between each contact region  30 , 32  and the elongated member  18  allowing the elongated member  18  to pass therethrough. Opening  16 , which is indicated by a phantom line in  FIG. 2 , may be dimensioned similarly as opening  14 , providing a second set of contact regions on the second flat region  26  of flexible body  20 . 
     The dimensions of the openings  14 , 16  can be selected to permit the passage of variously dimensioned elongated members  18 . For example, the diameter of the openings  14 , 16  may be configured to receive an elongated member having an outer diameter, for example, of 0.008-0.037 inches, and more specifically 0.014-0.018 inches, corresponding to the size of many conventional guidewires used in the art. Moreover, while openings  14 , 16  are depicted as being elliptical in shape, those of skill in the art will recognize that other configurations are possible. 
       FIG. 3  is a partial cross-sectional view showing the leaf spring  12  in an unlocked (i.e. compressed) position attached to an embolic protection filter  36 . Embolic protection filter  36  may include an expandable filter membrane  38  coupled to a filter frame  40 . The filter frame  40  may be formed of a wire loop  42  or other suitable support mechanism, and includes a support tube  44 , which in the exemplary embodiment illustrated is attached to a third flat region  46  of the leaf spring  12 . The support tube  44  is slidably and rotationally disposed about the elongated member  18  when leaf spring  12  is in an unlocked position, and releasably secured to the elongated member  18  when in the locked position. 
     As further illustrated in  FIG. 3 , when a compressive force F is applied longitudinally to compress the leaf spring  12  inwardly, the first and second flat regions  22 , 26  bend or flex about bend region  24 , orienting the openings  14 , 16  at a greater angle relative to the longitudinal axis of the elongated member  18 , forming a small clearance  34  between the periphery of the openings  14 , 16  and the outer surface of the elongated member  18 . In this position, the embolic protection filter  36  and attached leaf spring  12  may be moved along the elongated member  18  and placed at a desired location within the patient&#39;s body. In an angioplasty procedure, for example, embolic protection filter  36  can be advanced along the elongated member  18  to a location distal a lesion located within a body lumen. The leaf spring  12  can then be locked onto the elongated member  18 , and a therapeutic device advanced along the elongated member  18  to perform a therapeutic procedure such as percutaneous transluminal coronary angioplasty (PTCA) at a location proximal the embolic protection filter  36 . At the conclusion of the procedure, or when the embolic protection filter  36  becomes occluded, the leaf spring  12  can be disengaged from the elongated member  18  and removed from the body. 
       FIG. 4  is a partial cross-sectional view showing the leaf spring  12  in a locked (i.e. uncompressed) position along the elongated member  18 . In the absence of a compressive force acting on the leaf spring  12 , the first and second flat regions  22 , 26  of flexible body  20  revert to their natural state and frictionally engage the elongated member  18 . As shown in  FIG. 4 , the first flat region  22  slopes distally in a direction more parallel to the longitudinal axis of the elongated member  18 , forming a first set of contact points  48 , 50  about the periphery of the first opening  14 . Similarly, the second flat region  26  slopes proximally in a direction more parallel to the longitudinal axis of the elongated member  18 , forming a second set of contact points  52 , 54  about the periphery of the second opening  16 . In use, the first and second set of contact points  48 , 50 , 52 , 54  grip the elongated member  18 , preventing movement of the elongated member  18  through the first and second openings  14 , 16 . 
     Referring now to  FIG. 5 , an anchoring mechanism  110  in accordance with another exemplary embodiment of the present invention will now be described. Anchoring mechanism  110  comprises a multiple leaf spring  112  having a plurality of openings  162  configured to slidably and rotationally receive an elongated member  118  such as a guidewire or guide catheter. The multiple leaf spring  112  comprises a normally flat, flexible body  158  that can be deflected into a serpentine or saw-tooth shape when compressed in a direction substantially parallel to the longitudinal axis of the elongated member  118 . 
     As with other embodiments described herein, multiple leaf spring  112  may have an undulating shape formed by one or more indented regions  160  of the flexible body  158 . In addition, the materials used to form the multiple leaf spring  112  may selected to impart a particular degree of flexibility to the device. The multiple leaf spring  112  may be formed as a separate member and used as a proximal or distal stop, as shown in  FIG. 5 , or can be attached to or formed integrally with the intravascular device to directly secure the device to the elongated member  118 . 
     The flexible body  158  may comprise a plurality of elongate regions  166  each having an opening  162  configured to slidably receive the elongated member  116  in an unlocked position, and frictionally engage the elongated member  118  in a locked position. Each opening  162  can be configured similar to the openings  14 , 16  depicted in  FIG. 2 , defining two contact regions along the major axis of the opening  162  that grip the elongated member  118  when multiple leaf spring  112  is in the locked position. 
     Flexible body  158  further comprises a number of bend regions  164  connecting the several elongate regions  166  together in alternating fashion such that each alternating elongate region  166  runs substantially parallel to each other. Each elongate region  166  is configured to bend in either a proximal or distal direction relative to the bend region  164 , assuming a serpentine or saw-tooth shape when allowed to revert to its uncompressed (i.e. locked) position. In the exemplary embodiment illustrated in  FIG. 5 , flexible body  158  comprises eight alternating bend regions  164 . However, it should be recognized that any number of bends  164  and/or elongate regions  166  may be utilized. 
     A proximal flat region  168  of multiple leaf spring  112  is configured to align perpendicularly to the elongated member  118  in both the locked and unlocked positions. The proximal flat region  168  includes an opening having an inner diameter slightly larger than the outer diameter of the elongated member  118 , providing a clearance fit with the elongated member  118 . In use, the clearance fit prevents the proximal flat region  168  from becoming misaligned or tilted about the elongated member  118  as the multiple leaf spring  112  is advanced along the elongated member  118  in the unlocked position. A distal flat region  170  of the flexible body  118  similarly includes an opening through the distal end of the multiple leaf spring  112  that provides a clearance fit when the device is in either the locked or unlocked positions, preventing misalignment of the distal portion of the leaf spring  112 . 
     In any of the embodiments described herein, a centering bushing  172  may be used to further ensure that the leaf spring  12 , 112  is centered relative to the elongated member. In the embodiment of  FIG. 5 , for example, multiple leaf spring  112  may include a centering bushing  172  comprising a tubular shaft section  174  having an outer diameter configured to fit within the opening formed through proximal flat region  168 , and an inner diameter configured to slidably receive the elongated member  118 . A flanged section  176 , illustrated in  FIG. 6 , can be used to fixedly secure the centering bushing  172  to the proximal flat region  168 . 
       FIG. 6  is a partial cross-sectional view of multiple leaf spring  112 , showing the multiple leaf spring  112  in an unlocked position along the elongated member  118 . In an unlocked position shown in  FIG. 6 , the several elongate regions  166  are aligned at a greater angel relative to the longitudinal axis of the elongated member  118 , forming a small clearance  178  between the periphery of each opening  162  and the outer surface of the elongated member  118 . 
     In a locked position illustrated in  FIG. 7 , the elongate regions  166  are allowed to expand longitudinally to their natural state and frictionally engage the elongated member  118 . Each elongate region  166  slopes in alternating fashion in either a distal or proximal direction, orienting the respective openings  162  in a direction more parallel to the longitudinal axis of the elongated member  118 . The change in alignment of the openings  162  caused by the expansion of the multiple leaf spring  112  creates several sets of contact regions  180  between the periphery of each opening  162  and the outer surface of the elongated member  118 . In use, the contact regions  180  grip the elongated member  118 , preventing movement of the elongated member  118  through the openings  162 . 
     Referring now to  FIG. 8 , an anchoring mechanism  210  in accordance with another exemplary embodiment of the present invention will now be described in the context of a therapeutic procedure employing an embolic protection filter  236 . Anchoring mechanism  210  comprises a multiple leaf spring  212  similar to that discussed above with respect to  FIGS. 5-7 , but further including a joint  282  at the distal flat region  270  connecting the multiple leaf spring  212  to a support tube  244  of the embolic protection filter  236 . Joint  282  may be formed by soldering, welding, brazing, adhesive or other suitable bonding process and may be rotatable and/or slidable on an elongate member  218 . 
     A delivery sheath  284  used to transport the embolic protection filter  236  in a collapsed position through the patient&#39;s vasculature is shown withdrawn proximally, with the filter membrane  236  in an expanded position. An inner locking tube  286  can be utilized to advance the multiple leaf spring  212  and embolic protection filter  236  along elongated member  218  (e.g. a guidewire) placed within the body. Inner locking tube  286  has a proximal section (not shown), a distal section  288 , and an inner lumen  290  configured to slidably receive the elongated member  218 . A distal segment  292  of the inner locking tube  286  has an enlarged inner diameter configured to constrain the multiple leaf spring  212  within a portion of the inner lumen  290 . A locking tab(s)  294  on the inner locking tube  286  is configured to bend in an outward direction and engage the inner surface of the delivery sheath  284 , maintaining the multiple leaf spring  212  in the unlocked position. 
     To engage the multiple leaf spring  212  and releasably secure the embolic protection filter  236  to the elongated member  218 , inner locking tube  286  can be withdrawn proximally, causing the multiple leaf spring  212  to revert to its natural (i.e. uncompressed) state, as shown in FIG.  9 . Once the multiple leaf spring  212  engages the elongated member  218 , the inner locking tube  286  and delivery sheath  284  can be retracted proximally along the elongated member  218  and removed from the body. 
     In an alternative method illustrated in  FIG. 10 , the inner locking tube  286  can be held stationary while the delivery sheath  284  is withdrawn proximally. As the delivery sheath  284  is withdrawn, the locking tab  294  at the distal end  288  of the distal segment  292  bends in an outward direction to permit withdrawal of the inner locking tube  286  in the proximal direction. The inner locking tube  286  and delivery sheath  284  can then be retracted proximally along the elongated member  218  and removed from the patient&#39;s body, if desired.