Abstract:
A microtube guide has a microtube combined with a free-floating and removable core. The microtube is generally hollow with a tube shaft and a distal ring, the tube shaft and the distal ring formed from flexible plastic. The distal ring is conformable to the core and straightenable for insertion into a patient&#39;s body, and deploys when the core is withdrawn to form a loop. The core is received by the microtube and is configured to advance into the distal ring to cause a diameter of the distal ring to expand, retract, or straighten. The distal ring diameter is thus adjustable by the user.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to Provisional Patent Application U.S. Ser. No. 62/340,111, entitled “Microtube Guide” and filed on May 23, 2016, which is fully incorporated herein by reference. This application further is a continuation-in-part of, and claims priority to, U.S. Non-Provisional application Ser. No. 15/445,272, entitled “TAVR Valve Guidewire and Guidetube with Adjustable Distal Loop,” and filed on Feb. 28, 2017, which claims priority to U.S. Provisional Patent Application Ser. No. 62/301,270, entitled “TAVR Valve Guidewire and Guidetube with Adjustable Distal Loop” and filed on Feb. 29, 2016. These patent applications are fully incorporated herein by reference. 
     
    
     BACKGROUND AND SUMMARY 
       [0002]    Guidewires, tiny wires designed to navigate vessels within the body, are used in a vast array of medical procedures. After a guidewire is advanced to its desired treatment site, the guidewire acts as a guide that larger catheters can rapidly follow for advancement to the treatment site. 
         [0003]    Most currently-used guidewires are constructed of a solid wire or fixed core or slightly-movable core wrapped with wire. These wires have a set flexural strength (flexural modulus) that may vary in different segments of the wire, but the flexural strength at any one segment of the guidewire cannot be changed or adjusted after manufacture or during use in a patient. 
         [0004]    A microtube guide according to the present disclosure is a unique “hybrid” concept that uses a microcatheter as the outer component of the guide and a free and movable central core as the inner component of the guide. The distal end of the microcatheter is closed, not open as in a typical catheter. 
         [0005]    The central core may be tapered for a portion of its distal end, and by adjusting the depth of core insertion into the microcatheter, the stiffness of that segment of the guide may be adjusted. The depth of core insertion or retraction can also be used to change the configuration of the guide. 
         [0006]    Because the central core drives the stiffness of the guide, cores can be exchanged for other cores having different stiffness, distal taper, or even core wire shape—all with the same outer tube (microcatheter). The core exchange can even be done during the procedure while the outer component of the guide is in the patient. The guide of the present disclosure thus provides the capability of changing wire support during a procedure without having to exchange the device. 
         [0007]    Being able to adjust the depth of the core can change the configuration of the microtube guide. The shape of the distal end of the central core can be formed as desired by the thermoset process of the polyimide or other manufacturing processes. Advancing or retracting the core can vary this shape of the distal end. Exchanging the core for a stiff or softer, long taper or short taper, distal end can also change the guide&#39;s distal configuration or transport performance of the desired device. 
         [0008]    In addition, having the outer surface of the device being a smooth microcatheter construction and not a wire wrapped core (as are most of our present guidewires) is be less traumatic to the human tissues. In use with heart TAVR procedures, this characteristic should help prevent wire perforations of the heart or other damage. 
         [0009]    In some embodiments, these “hybrid” devices will be constructed of a polyimide (or similar substance) microcatheter with or without braid as an outer component. Unlike currently-used microcatheters, the distal end will not be open to the patient. The size (OD) will vary upon the device application—coronary, peripheral, structural heart, cerebral, etc. The inner core will typically be a PTFE coated stainless steel wire or nitinol (but not limited to these). 
         [0010]    Adjustment collars of the microtube may be used to hold the core position within the microtube, as discussed herein. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  depicts a microcatheter guide according to an exemplary embodiment of the present disclosure. 
           [0012]      FIG. 2  depicts an exemplary core of the microcatheter guide according to an embodiment of the present disclosure. 
           [0013]      FIG. 3  depicts the guide of  FIG. 1 , showing the adjustment capability of the guide. 
           [0014]      FIG. 4  depicts an exemplary adjustment collar for adjusting the guide. 
           [0015]      FIG. 5  depicts a partial view of the guide showing an adjustment collar installed over the core to set the distance the core is advanced within the microtube. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 1  depicts a microtube guide  100  comprising a microtube  101  combined with a free-floating and removable core  102  according to the present disclosure. The microtube  101  is a hollow microcatheter, formed from plastic in one embodiment. A proximal opening  107  of the microtube  101  receives the core  102 , which slides within the microtube  101  to advance and retract in the direction indicated by directional arrow  120 . 
         [0017]    The microtube  101  comprises a generally straight main shaft  103  that is hollow to receive the core  102 . The microtube  101  further comprises an expandable distal loop  105 . The distal loop  105  is disposed at a distal end  106  of the microtube  101 . The distal end  106  of the microtube is closed in the illustrated embodiment, and not open like typical microcatheters. 
         [0018]    The guide further comprises a proximal core end  104 , which in the illustrated embodiment is a section of microcatheter tubing that is fixed to the core  102 . The outer diameter of the proximal end is generally the same as the outer diameter of the microtube  101 . When the guide is initially being fed into a patient&#39;s vessels, the core  102  may be fully advanced within the microtube  101 , i.e., such that there is not an exposed section of core  102  as is shown in  FIG. 2 . The proximal core end  104  being formed from microcatheter tubing of the same diameter as the microtube  101  provides a smooth, gap-free outer surface of the guide  100  when the guide is being fed into the patient. 
         [0019]    The main shaft  103  of the microtube  101  is formed from kink-resistant, thin-walled, semi-rigid plastic tube that is 0.035 inches in outer diameter in one embodiment. In other embodiments, the main shaft  103  is formed with braided steel within the plastic of the guidetube (polyimide braid, for example). 
         [0020]    In one embodiment, the distal loop  105  is slightly larger in cross-sectional diameter than the main shaft  103 , and formed from kink-resistant, semi-rigid plastic tubing that is the range of 0.045-0.054 inches in outer diameter. A transition portion (not shown) between the main shaft  103  and the distal loop  105  transitions the main shaft  103  to the distal loop  105  in one embodiment. In this regard, the main shaft  103  may be fused to the distal loop  105  at the transition portion. 
         [0021]    The distal loop  105  being larger in diameter than the main shaft  103  helps to prevent excessive forward advancement of the valve delivery system (not shown) that delivers the replacement valve. In addition, the distal loop  105  being larger in diameter may simplify forming of the microtube  101 . In this regard, the main shaft  103  may be fit within and be frictionally received by the distal loop  105  prior to fusing of the main shaft  103  to the distal loop  105 . 
         [0022]    The distal loop  105  is softer than the main shaft  103 , and when not acted upon by an external catheter (not shown) or the core  102 , the distal loop forms a loop as shown. In the illustrated embodiment, the body of the distal loop makes about one and one half loops. An outer diameter of the distal loop in this configuration may be about 3.0 centimeters. 
         [0023]    When the core  102  is advanced such that its tip  122  (shown in dashed line) enters the distal loop  105 , the tip  122  contacts an inner surface  123  of the distal loop  105  and causes the diameter of the distal loop  105  to increase. By advancing or retracting the core  102 , the size of the distal loop  105  may be enlarged or decreased. Further, the distal loop  105  may fully straighten upon advancement of the core  102  as well. 
         [0024]    Although  FIG. 1  illustrates a distal loop  105  that extends downwardly from the guide, in other embodiments, the loop may be disposed horizontally to the microtube  101 , i.e., perpendicular to the microtube  101 , or otherwise oriented differently. 
         [0025]      FIG. 2  depicts an enlarged view of an exemplary core  102  according to an embodiment of the present disclosure. The core  102  is advanced through the proximal opening  107  ( FIG. 1 ) of the microtube  101 . 
         [0026]    The core  102  comprises a main shaft  110  and a tapered distal end  111 . The main shaft  110  and the distal end  111  are formed from flexible polytetrafluoroethylene (PTFE) coated stainless steel in one embodiment. In this embodiment, the distal end  111  is smaller in diameter than the main shaft  110  and tapers from the diameter of the main shaft  110  to a distal tip  112 . The distal tip  112  is received by the proximal opening  107  ( FIG. 1 ) of the microtube  101  ( FIG. 1 ) and advances into the distal loop  105  ( FIG. 1 ) of the microtube  101 . 
         [0027]    As discussed above with respect to  FIG. 1 , the core  102  further comprises a proximal core end  104  that is a section of microcatheter tubing fixed to the main shaft  110  of the core  102 . An adjustment section  113  of the core  102  is disposed adjacent to the proximal core end  104 . In the illustrated embodiment, the adjustment section  113  is shown as textured (e.g., etched). The texture in the adjustment section may help the core  102  grip the inside of the microtube  101  ( FIG. 1 ). 
         [0028]      FIG. 3  depicts the guide  100  of  FIG. 1 , showing an exposed section  121  of the main shaft  110  of the core  102  between the microtube  101  and the proximal core end  104  of the guide  100 . The proximal core end  104  is fixed to the main shaft  110  of the core  102 , and the core  102  is received by and slides within the microtube  101 . In a method for operating the guide  100 , the user (not shown) advances the core  102  within the microtube  101  until the core  102  expands the distal loop  105  to the desired diameter. When the core  102  has been advanced as desired, the exposed section  121  of core  102  will be a length “L” as indicated in  FIG. 3 . At this point, a collar  130  ( FIG. 4 ) of the same length “L” may be placed onto the exposed section  121 , fitting over the core  102  between a lower end  135  of the proximal core end  104  and the proximal opening  107 . The collar  130  serves to fix the core  102  within the microtube  101  such that it cannot advance further into the microtube  101 . 
         [0029]      FIG. 4  depicts an enlarged view of an exemplary collar  130  as discussed above with respect to  FIG. 3 . The collar  130  comprises a generally semi-cylindrical (“C”-shaped) section of microtubing of a length “L,” with a slit  131  that is sized so that the collar  130  can fit over the main shaft  110  ( FIG. 3 ) of the core  102  ( FIG. 3 ). The collar  130  further comprises a proximal collar end  132  and a distal collar end  133 . When the collar  130  is installed on the guide  100  ( FIG. 3 ), the proximal collar end  132  is adjacent to and contacts the lower end  135  ( FIG. 3 ) of the proximal core end  104  ( FIG. 3 ), and the distal collar end  133  is adjacent to and contacts the proximal opening  107  ( FIG. 3 ) of the microtube  101  ( FIG. 3 ). The collar  130  may be any of various lengths “L,” which lengths are determined by the lengths desired for the user to get the desired advancement of the core  102  within the microtube  101 . Thus multiple collar lengths are available depending on the length desired by the user. 
         [0030]      FIG. 5  depicts a partial view of the guide  100  with the collar  130  installed on the guide  100  to temporarily fix the length of the core  102  (shown in dashed line) that is advanced within the microtube  101 . The collar  130  has an outer diameter that is generally the same as the microtube  101  and the proximal core end  104  of the core  120 , such that when the collar  130  is installed, the outer surfaces of the proximal core end  104 , the collar  130 , and the microtube  101  are generally flush. 
         [0031]    In an exemplary operation of the guide  100 , the core  102  may initially be fully advanced into the microtube  101  such that the microtube  101  is generally straight, with no looped distal end. In this configuration, the lower end  135  of the proximal core end  104  is adjacent to and contacts the proximal opening  107  of the microtube  101 . Two users (not shown) may be required to hold the guide  100  during installation and use due to the length of the guide  100 . One user typically holds the proximal core end  104  of the core  102  while the other user maneuvers the distal end of the guide  100  into the patient. When the guide  102  is used in a TAVR procedure, for example, after the distal end of the microtube  101  crosses the valve, the person holding the proximal core end  104  may hold it steady while the other person advances the microtube  101  slightly to deploy the distal end  105  into a loop as discussed herein. When the distal end  105  is deployed as desired, a collar  130  of the desired length “L” can be installed in the now-exposed space between the lower end  135  of the proximal core end  104  and the proximal opening  107  of the microtube  101 . 
         [0032]    In other embodiments, the microtube (not shown) may not have a distal ring. Rather, the microtube may conform to a shape and stiffness of a core (not shown) that has some other shape. 
         [0033]    This disclosure may be provided in other specific forms and embodiments without departing from the essential characteristics as described herein. The embodiments described are to be considered in all aspects as illustrative only and not restrictive in any manner. 
         [0034]    The terms “first,” “second,” and the like are used herein to describe various features or elements, but these features or elements should not be limited by these terms. These terms are used only to distinguish one feature or element from another feature or element. Thus, a first feature or element discussed below could be termed a second feature or element, and similarly, a second feature or element discussed below could be termed a first feature or element without departing from the teachings of the present disclosure. Further, the presence of a “first” or “second” feature or element (or the like) does not imply the presence of any additional such feature or element.