Abstract:
A mechanism can include a step feature guidewire having a guidewire with a proximal end, a distal end, and a diameter. A self-expanding element can be disposed approximate to the distal end of the guidewire and can have at least two states which include a contracted diameter and an expanded diameter. The self-expanding element can be expandable under its inherent proprieties, based at least on its original shape and the nature of the materials that make up the element. Further, the expanded diameter can be approximately 70% to 280% of the guidewire diameter. While the guidewire is designed for passing through a body lumen while treating a patient, the expanded diameter is less than any body lumen diameter the guidewire is determined to pass through.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a self-expanding feature that can be integrated into a distal aspect of a guidewire to facilitate the crossing of a previously deployed device in the vasculature with a catheter or microcatheter. 
       BACKGROUND 
       [0002]    Crossing a previously deployed intravascular stent with a catheter over a guidewire presents a challenge, especially during neurovascular procedures. Often it is not possible to advance a catheter over the guidewire because of a ledge formed between the outer diameter of the guidewire and the outer diameter of the catheter.  FIG. 1A  illustrates a microcatheter  2  with a guidewire  4 , therethrough, hung up on a stent strut  6 .  FIG. 1A  is a forward view of the catheter  2  over the wire  4  crossing through the stent cell  10  and getting caught on the stent struts  6  (as in the case of an aneurysm coiling procedure) because of the difference in diameters of the guidewire  4  and the catheter  2 .  FIG. 1B  illustrates the ledge  8 , as the difference between the outer diameter of the guidewire  4  and the outer diameter of the microcatheter  2 . The ledge  8  distance can actually be greater as the guidewire  4  can be displaced from a center axis of the microcatheter  2 , creating even more of a gap.  FIG. 1C  illustrates the above problem. The stent cell  10  is placed within a body lumen (not illustrated) and the guidewire  4  is guided through the lumen. The microcatheter  2  is then advanced along the guidewire  4  and gets hung up on the stent strut  6  at the ledge  8 . 
         [0003]    Prior art attempts to solve this problem included “rounding” or “beveling” the tip of the catheter to facilitate tracking over the struts of the device. Additionally, a multi-catheter configuration has been tried in which catheters of progressively smaller diameters are inserted coaxially inside each other to minimize the ledge. 
         [0004]    What is needed is a simple mechanism to prevent the ledge  8  from catching on the stent strut  6  while still being able to advance the guidewire  4  and microcatheter  2 . 
       SUMMARY 
       [0005]    A mechanism to help prevent the ledge of the prior art can include a step feature guidewire having a guidewire with a proximal end, a distal end, and a diameter. A self- expanding element can be disposed approximate to the distal end of the guidewire and can have at least two states which include a contracted diameter and an expanded diameter. The self-expanding element can be expandable under its inherent proprieties, based at least on its original shape and the nature of the materials that make up the element. Further, the expanded diameter can be approximately 70% to 280% of the guidewire diameter. While the guidewire is designed for passing through a body lumen while treating a patient, the expanded diameter is less than any body lumen diameter the guidewire is determined to pass through. 
         [0006]    Examples of the self-expanding element can be one of pear shaped, ovoid, and elliptical when at its expanded diameter. These can act as a “ramp” to get the catheter over any obstacle in the body lumen, e.g. a previously implanted stent. Also, the self-expanding element can include a plurality of deformable leafs. In another example of a step feature guidewire, a bump can be disposed on the guidewire under the self-expanding element and the self-expanding element is slideable along the guidewire. In this configuration, the bump can limit the slidability of the self-expanding element. This can be because when the self-expanding element has expanded to the expanded diameter, a length of the self-expanding element decreases, and the bump limits the decrease in length and thus the expanded diameter. 
         [0007]    Other examples have the combination of a steerable catheter and guidewire system that have a catheter having a catheter inner diameter forming a guidewire lumen and a catheter outer diameter. A guidewire can have a proximal end, a distal end, and a guidewire diameter. A self-expanding element can be disposed approximate to the distal end of the guidewire, and when the self-expanding element is disposed within the catheter, the self-expanding element has a contracted diameter. Here, the self-expanding element collapses in size and shape to enter the catheter to either be delivered to its target location in the body lumen or removed from the catheter so other tools can be disposed through the guidewire lumen. Alternately, when the self-expanding element is disposed outside the catheter, the self-expanding element has an expanded diameter, which is reached because it&#39;s expandable under its inherent proprieties. 
         [0008]    In examples, the expanded diameter can be approximately 5% to 10% of the catheter outer diameter. As above, the expanded diameter is less than the body lumen diameter and the self-expanding element can be at least one of pear shaped, ovoid, and elliptical when at its expanded diameter. The self-expanding element can be inflatable or can include a plurality of deformable leafs and the contracted diameter permits the guidewire to be completely removed from the catheter. 
         [0009]    Other examples are a method of advancing a steerable guidewire through a body lumen, using the steps of providing the steerable guidewire having a proximal end, a distal end, and a guidewire diameter. The self-expanding element can be disposed proximate the distal end and has a contracted and an expanded diameter. The self-expanding element can be expanded to the expanded diameter, which can be approximately 70% to 280% of the guidewire diameter. 
         [0010]    Examples of the expanding step can further include a step of providing the expanded diameter less than a diameter of a body lumen. Further steps can be providing a catheter having a catheter diameter forming a guidewire lumen and advancing the steerable guidewire through the guidewire lumen. The self-expanding element can be disposed in the catheter with the contracted diameter and then the expanding step can further include disposing the self-expanding element outside the guidewire lumen to reach the expanded diameter. Additionally, the self-expanding element can be retracted into the guidewire lumen, thus changing the expanded diameter to the contracted diameter. 
         [0011]    These and other examples can overcome the challenges in the prior art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    This invention is described with particularity in the appended claims. The above and further aspects of this invention may be better understood by referring to the following description in conjunction with the accompanying drawings, in which like numerals indicate like structural elements and features in various figures. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
           [0013]    The drawing figures depict one or more implementations in accord with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements. 
           [0014]      FIG. 1A  is a top perspective view of a known microcatheter and guidewire caught on a stent strut; 
           [0015]      FIG. 1B  is a side cross-section view of a known microcatheter and guidewire; 
           [0016]      FIG. 1C  is a side cross-section view of a known microcatheter and guidewire caught on a stent strut; 
           [0017]      FIG. 2  is a side cross-section view of an example of a step feature for a guidewire of the present invention; 
           [0018]      FIG. 3  is a front view of an example of a step feature for the guidewire of the present invention; 
           [0019]      FIG. 4  is a cross-section view along line A-A of  FIG. 2 ; 
           [0020]      FIG. 5  is a cross-section view along line B-B of  FIG. 2 ; 
           [0021]      FIG. 6  is a cross-section view along line C-C of  FIG. 2 ; 
           [0022]      FIGS. 7A-7D  are side cross-section views of an example of a steerable guidewire being deployed and retracted; 
           [0023]      FIG. 8  is a side cross-section view of an example of a microcatheter and guidewire of the present invention avoiding being caught on a stent strut; and 
           [0024]      FIG. 9  is a flow chart of an example of a method of using a step feature for a guidewire. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant teachings. However, it should be apparent to those skilled in the art that the present teachings may be practiced without such details. In other instances, well known methods, procedures, components, and/or circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present teachings. 
         [0026]      FIGS. 2-6  illustrate an example of a step feature for a guidewire  100  of the present invention. The guidewire  100  can have a core  102 , which extends the length of the guidewire  100 , and a proximal end  104  and a distal end  106 . The guidewire  100  and core  102  can be made of any material known to those of skill in the art for guidewires. The guidewire  100  has a guidewire diameter  108  so it can be directed through any size body lumen or passageway for a mammal. In one example, the guidewire  100  can be sized for neurovascular procedures. In another example, the guidewire diameter  108  is typically uniform across the length of the guidewire  100 . 
         [0027]    Disposed over the guidewire core  102  is a catheter/microcatheter  110 . The catheter  110  has a catheter diameter  112  which is larger than the guidewire diameter  108 , so that the guidewire  100  can pass through the inside  111  of the catheter  110 . As above, the catheter  110  is sized so it can be directed through any size body lumen or passageway for a mammal, and in one example it can be sized for neurovascular procedures. The catheter  110  is made out of materials known to those of skill in the art, and in one example, can be relatively soft and pliable. 
         [0028]    A gap  114  can be formed between the proximal  104  and distal  106  ends of the guidewire  100  over which can be disposed a self-expanding element  116 . The self-expanding element  116  can be designed to expand and contract so as to increase and decrease its diameter. The self-expanding element  116  has a contracted diameter  118  which can be less than the catheter diameter  112  and, in one example, approximately equal to the guidewire diameter  108 . The self-expanding element  116  typically has its contracted diameter  118  when disposed within the catheter  110 . See,  FIG. 7A . The self-expanding element  116  can also have an expanded diameter  120 . The expanded diameter  120  can be greater than the guidewire diameter  108 , and in one example, greater than the catheter diameter  112 . The self-expanding element  116  can take its expanded diameter  120  once deployed from the catheter  110 . See,  FIG. 7B . The expanded diameter  120  is such that it can diminish or remove the ledge  8 , as seen in the prior art. The leaves  124  can act as a “ramp” and this allows the guidewire  100  and catheter  110  to pass over the stent struts  6  of the stent cell  10 , see  FIG. 8 . 
         [0029]    The self-expanding element  116  can be radially expandable from the contracted diameter  118 , in one example where the element  116  is not greater in diameter  118  than the diameter of the guidewire shaft  108 , to the expanded diameter  120 , in which the diameter  120  of the element  116  is greater than that of the guidewire  108 . The self-expanding element  116  can be self-expanding under the influence of its inherent flexibility. 
         [0030]    In one example, the self-expanding element  116  is a multi-leaf element. Each leaf  122  has the ability to flex so it can change shape and then return to its original shape. Thus the leaves  122  flex to allow the self-expanding element  116  to alternate between its contracted diameter  118  and expanded diameter  120 . The self-expanding multi-leaf element  116  may be laser cut from a hypotube or fabricated from wires. The self-expanding element  116  may contain as few as three (3) or as many as twelve (12) leafs  122 . In an example, some or all of the self-expanding multi-leaf element  116  can be radiopaque, allowing the surgeon to determine if the element  116  has been deployed from the catheter  110 . 
         [0031]      FIGS. 3-6  illustrate the self-expanding element  116  in its deployed state.  FIG. 3  illustrates the leaves  122  creating the expanded diameter  120  greater than the catheter diameter  112 .  FIGS. 4-6  illustrate the self-expanding element  116  along the length of the gap  114  and how it can be, in an example, unfixed to the core  102 . In a yet further example, the self-expanding element  116  can also be secured directly to the core  102  near the proximal end  104 . In this configuration the self-expanding clement  116  does not rotate or move axially over the core  102  (except for forward translation) but can be deployed into and out of the catheter  110 . 
         [0032]    In a further example, the self-expanding element  116  can rotate or move axially along the core  102  in the gap  114 . The movement of the self-expanding element within the gap  114  can be controlled by a number of different features. In this example, an expansion/retraction bump  124  can be placed on the core  102  and under the leaves  122 /self-expanding element  116 . The expansion/retraction bumps  124  can have a larger outer diameter than an inner diameter of the leaves  122  on the self-expanding element  116 . This can limit the amount of axial displacement of the self-expanding element  116 . Additionally, one or both of the expansion/retraction bumps  124  may be radiopaque. 
         [0033]    As illustrated in  FIGS. 7A-7D , while tracking the guidewire  100  inside of a microcatheter  110 , the self-expanding element  116  is constrained as shown on  FIG. 7A . The self-expanding element  116  is located inside the microcatheter  110  by the mechanical interference between the larger distal expansion/retraction bump  124  and the distal self-expanding element leaf  122 . The self-expanding element  116  opens once it is deployed out of the microcatheter  110 , as shown in  FIG. 7B . Alignment of a radiopaque proximal expansion/retraction bump  124   a  with a catheter distal marker  110   a  can indicate that the self-expanding element  116  is fully opened. Once deployed, the guidewire  100  and catheter  110  can be advanced in tandem over the stent cell  10  without the potential for the catheter&#39;s  110  tip getting caught on the stent struts  6 . Compare  FIG. 1C  with  FIG. 8 . Note that the stent cell  10  could have been deployed during a previous procedure, and now the surgeon is performing a second procedure.  FIGS. 7C and 7D  illustrate the self-expanding element  116  collapsing back into the microcatheter  110  by pulling on the guidewire  100  until the self-expanding element  116  is driven inside of the microcatheter  110  by the mechanical interference between the expansion/retraction bump  124 . 
         [0034]    Another example of how the self-expanding element  116  functions is that, in its rest position, the leaves  124  flex to the expanded diameter  120 . In this state, the overall length of the self-expanding element  116  is L. As the leaves  124  are “flattened”, that is to say straightened to a more parallel position, the length of the self-expanding element  116  can be increased to L+. Thus, one or both of the ends of the self-expanding element  116  translate along the core  102 . The self-expanding element  116  can be made from any spring or memory type metal or material. In one example, the material can be a nickel-titanium alloy (e.g. Nitinol). However, any element that can be expanded or contracted and deployed from a catheter can be used as the self-expanding element  116 . Further, an example of the expanded diameter  120  is that it can be 5-10% greater than the catheter diameter  112 . In examples, the expanded diameter  120  can be greater than the outer diameter of the catheter, but not significantly so as to prevent the catheter and guidewire from passing through the chosen body lumen. 
         [0035]    In other examples, the expanded diameter  120  can be compared to the guidewire diameter  108 . The expanded diameter  120  can range between approximately 70% to 280% of the guidewire diameter depending on the combinations of guidewires and catheters. Additionally, the shape of the self-expanding element  116  can be any shape that facilitates the passing of the catheter  110  over a stent strut  6 . Examples of shapes are pear shaped, ovoid, and elliptical. Both the expanded diameter  120  and the shape of the self-expanding element  116  can be such that the leaves  122  are not designed to contact the walls of which ever body lumen the steerable wire  100  is passed through. In an example, the self-expanding element  116  does not assist in “centering” the guidewire/catheter system through the body lumen, on the contrary, the guidewire/catheter system needs some tolerance to the body lumen in order to move around the stent. 
         [0036]    In use, the surgeon is typically aware that the patient has a previously deployed stent in the body lumen through which she needs to pass the guidewire and catheter. The surgeon can then choose to use the step feature for the steerable guidewire of the present invention. The self-expanding element  116  is typically deployed prior to reaching the stent, and its deployment verified using radio, X-ray or fluoroscopy imaging. Once the guidewire and catheter have passed the stent, and the catheter is in position for the new procedure, the surgeon can pull back on the guidewire, collapsing the self-expanding element, and fully remove the guidewire without complications from the element to proceed with the remainder of the surgical procedure. 
         [0037]      FIG. 9  illustrates a method of advancing a steerable guidewire with a step function through a body lumen, which includes the step of providing a catheter  110  having a catheter diameter  112  that can form a guidewire lumen (step  200 ). A steerable guidewire  100  with a proximal end  104  and a distal end  106  having a self-expanding element  116  carried near the distal end  106  thereof can also be provided (step  202 ). The steerable guidewire  100  can be advanced through the guidewire lumen (step  204 ) and both the guidewire and catheter can be manipulated to locate the distal end  106  to a predetermined location in the body lumen (step  206 ). Either before or once an obstacle, such as a stent  6 , is encountered, the steerable guidewire  100  is extended past the catheter  110  to expose the self-expanding element  116  (step  208 ). The self-expanding element  116  can be expanded to its expanded diameter  120  (step  210 ) and the steerable guidewire  100  and catheter can be advanced over the obstacle (step  212 ). The self-expanding element  116  can be contracted by retracting the steerable guidewire  100  back into the catheter  110  (step  214 ). 
         [0038]    While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that the teachings may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all applications, modifications and variations that fall within the true scope of the present teachings.