Patent Publication Number: US-2022211529-A1

Title: Constraining mechanisms for selective deployment and associated methods

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a national phase application of PCT Application No. PCT/US2019/031780, internationally filed on May 10, 2019, which is herein incorporated by reference in its entirety for all purposes. 
    
    
     FIELD 
     The present disclosure relates to apparatuses, systems, and methods that include constraints used in delivery of implantable medical devices. More specifically, the present disclosure relates to apparatuses, systems, and methods that include constraints for selective deployment of an expandable device during device delivery. 
     BACKGROUND 
     Stents and stent-grafts may be utilized to radially support a variety of tubular passages in the body, including arteries, veins, airways, gastrointestinal tracts, and biliary tracts. The preferred method of placing these devices has been to use specialized delivery systems to precisely place and deploy a device at the site to be treated. These delivery systems allow the practitioner to minimize the trauma and technical difficulties associated with device placements. Attributes of delivery systems include: low profile; ability to pass through introducer sheaths; ability to negotiate tortuous vasculature, smoothly and atraumatically; protection of constrained devices; and ability to accurately position and deploy the device. 
     Stents or stent-grafts may be deployed and plastically deformed, such as by using an inflatable balloon, or to self-expand, such as through elastic recovery, from a collapsed or constrained delivery diameter to an expanded and deployed diameter. Some stents are designed to elastically recover by being manufactured at their functional diameter out of a material that has elastic recovery properties, and then radially compressed to be mounted on a delivery catheter. 
     These stent and stent-graft devices may be held, compressed, or constrained in the delivery configuration prior to and during delivery to a target location. 
     SUMMARY 
     According to one example (“Example 1”), a medical device deployment apparatus includes at least one constraining fiber configured to form a warp knit surrounding a medical device, the warp knit being configured to separate and be removed to deploy the medical device; and wherein the at least one constraining fiber include a first series of loops forming the warp knit with at least one of the first series of loops including a first portion forming a knot and a second portion arranged in addition to the knot. 
     According to another example (“Example 2”), further to the apparatus of Example 1, the warp knit includes a second constraining fiber including a second series of loops and the first series of loops and the second series of loops form a knot row. 
     According to another example (“Example 3”), further to the apparatus of Example 2, the first portion of the series of loops and the second portion of the series of loops are arranged through the second series of loops. 
     According to another example (“Example 4”), further to the apparatus of Example 3, the second portion of the first series of loops includes a second loop. 
     According to another example (“Example 5”), further to the apparatus of Example 3, the second portion of the first series of loops includes a length of the at least one constraining fiber extending beyond a length of the at least one constraining fiber forming the knot. 
     According to another example (“Example 6”), further to the apparatus of Example 5, the length of the at least one constraining fiber is rotated relative to the knot. 
     According to another example (“Example 7”), further to the apparatus of Example 2, wherein each of the knots in the knot row are formed by the first series of loops and the second series of loops with each of the first series of loops including a second portion arranged in addition to the knots. 
     According to another example (“Example 8”), further to the apparatus of Example 1, the at least one of the first series of loops including the first portion forming the knot is arranged at a distal end of the warp knit. 
     According to another example (“Example 9”), further to the apparatus of Example 1, the at least one of the first series of loops including the first portion forming the knot is configured as to resist premature deployment of the medical device. 
     According to one example (“Example 10”), a method of releasably constraining a medical device includes forming a warp knit to surround a medical device using at least one constraining fiber, the warp knit being configured to separate and be removed to deploy the medical device and including a first series of loops; and forming a knot within the warp knit with at least one of the first series of loops including a first portion and a second portion arranged in addition to the knot. 
     According to another example (“Example 11”), further to the method of Example 10, forming the knot includes forming the knot at a distal end of the warp knit. 
     According to another example (“Example 12”), further to the method of Example 10, forming the knot includes forming a slip knot with the second portion being a length arranged in excess of the slip knot. 
     According to another example (“Example 13”), further to the method of Example 10, forming the knot includes forming the second portion in a second loop. 
     According to another example (“Example 14”), further to the method of Example 10, the knot is configured as to resist premature deployment of the medical device 
     According to another example (“Example 15”), further to the method of Example 10, the warp knit includes a second constraining fiber including a second series of loops and the first series of loops and the second series of loops form a knot row. 
     According to one example (“Example 16”), a deployment apparatus includes an implantable medical device; a constraint configured to releasably constraint the implantable medical device in a constrained configuration, the constraint including: a first row of knots formed by a first constraining fiber interwoven with a second constraining fiber surrounding the medical device in the constrained configuration, and a second row of knots formed by the second constraining fiber interwoven with a third constraining fiber surrounding the medical device in the constrained configuration, the first row of knots including a distal knot formed by a first loop of the first constraining fiber and a second loop of the second constraining fiber with the second loop including a first portion forming the knot and a second portion arranged in addition to the knot. 
     According to another example (“Example 17”), further to the apparatus of Example 16, each of the knots in the second knot row are formed by a first series of loops and a second series of loops with each of the second series of loops including a first portion forming the knot and a second portion arranged in addition to the knots. 
     According to another example (“Example 18”), further to the apparatus of Example 16, the second portion includes a second loop. 
     According to another example (“Example 19”), further to the apparatus of Example 16, the distal knot is configured as to resist premature deployment of the medical device. 
     According to another example (“Example 20”), further to the apparatus of Example 16, the second portion includes a length of fiber extending beyond a length of the third constraining fiber forming the distal knot. 
     The foregoing Examples are just that, and should not be read to limit or otherwise narrow the scope of any of the inventive concepts otherwise provided by the instant disclosure. While multiple examples are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative examples. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature rather than restrictive in nature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments, and together with the description serve to explain the principles of the disclosure. 
         FIG. 1  is a top plan view of a delivery system including a catheter with a constraint, in accordance with an embodiment; 
         FIG. 2  is a side view of an implantable medical device including a constraint, in accordance with an embodiment; 
         FIG. 3  is an illustration of an example deployment apparatus, in accordance with an embodiment; 
         FIG. 4  is an illustration of an example deployment apparatus, in accordance with an embodiment; 
         FIG. 5A  is an image of a delivery system in a delivery configuration, in accordance with an embodiment; and 
         FIG. 5B  is an image of the delivery system, shown in  FIG. 5A , in a semi-deployed configuration, in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Definitions and Terminology 
     As the terms are used herein with respect to ranges of measurements “about” and “approximately” may be used, interchangeably, to refer to a measurement that includes the stated measurement and that also includes any measurements that are reasonably close to the stated measurement, but that may differ by a reasonably small amount such as will be understood, and readily ascertained, by individuals having ordinary skill in the relevant arts to be attributable to measurement error, differences in measurement and/or manufacturing equipment calibration, human error in reading and/or setting measurements, adjustments made to optimize performance and/or structural parameters in view of differences in measurements associated with other components, particular implementation scenarios, imprecise adjustment and/or manipulation of objects by a person or machine, and/or the like. 
     This disclosure is not meant to be read in a restrictive manner. For example, the terminology used in the application should be read broadly in the context of the meaning those in the field would attribute such terminology. 
     With respect terminology of inexactitude, the terms “about” and “approximately” may be used, interchangeably, to refer to a measurement that includes the stated measurement and that also includes any measurements that are reasonably close to the stated measurement. Measurements that are reasonably close to the stated measurement deviate from the stated measurement by a reasonably small amount as understood and readily ascertained by individuals having ordinary skill in the relevant arts. Such deviations may be attributable to measurement error or minor adjustments made to optimize performance, for example. In the event it is determined that individuals having ordinary skill in the relevant arts would not readily ascertain values for such reasonably small differences, the terms “about” and “approximately” can be understood to mean plus or minus 10% of the stated value. 
     Certain terminology is used herein for convenience only. For example, words such as “top”, “bottom”, “upper,” “lower,” “left,” “right,” “horizontal,” “vertical,” “upward,” and “downward” merely describe the configuration shown in the figures or the orientation of a part in the installed position. Indeed, the referenced components may be oriented in any direction. Similarly, throughout this disclosure, where a process or method is shown or described, the method may be performed in any order or simultaneously, unless it is clear from the context that the method depends on certain actions being performed first. 
     Description of Various Embodiments 
     Persons skilled in the art will readily appreciate that various aspects of the present disclosure can be realized by any number of methods and apparatus configured to perform the intended functions. It should also be noted that the accompanying drawing figures referred to herein are not necessarily drawn to scale, but may be exaggerated to illustrate various aspects of the present disclosure, and in that regard, the drawing figures should not be construed as limiting. 
     Various aspects of the present disclosure are directed toward apparatuses, systems, and methods that include forming or manufacturing a constraint. The constraining mechanisms are configured to hold, compress, or constraint an implantable medical device (e.g., a stent, stent-graft, balloon, filter, or other expandable medical device) in a delivery configuration prior to and during delivery to a target location. In certain instances, constraints may include one or more fibers that are arranged together. The fibers may be interwoven, stitched, or otherwise interlocked together circumferentially about the device. To remove the constraint, one or more of the fibers may be unknitted or disrupted from the other fibers in the constraint. 
     Constrained devices may store energy as a result of being constrained in a diameter smaller than a natural or deployed diameter. Thus, the devices may exhibit a radial displacement force against the constraint. During deployment of constrained devices, the radial force may force unknitting of the constraint without user involvement such that the constraint self un-knitts. The aspects of the present disclosure, however, eliminate this premature deployment. As discussed in further detail below, the constraint may include a pattern or knot structure that lessens premature deployment. 
       FIG. 1  is a top plan view of a catheter  100  with a constraint  102 , according to some embodiments. As shown in  FIG. 1 , the constraint  102  is configured to constraint an implantable medical device  104  to a delivery configuration. The constraint  102  may include one or more fibers  106  arranged about the implantable medical device  104  to maintain the constraint  102  in a constrained configuration. 
     The constraint  102  is arranged along a length of the implantable medical device  104 . The constraint  102  is also circumferentially arranged about the implantable medical device  104  and may substantially cover the implantable medical device  104  for delivery. The one or more fibers  106  may be arranged within a lumen (not shown) of the catheter  100  and extend toward a proximal end of the catheter  100  that is arranged external to a patient during delivery of the implantable medical device  104 . The one or more fibers  106  include a proximal end  108  that a user may apply tension to in order to release the constraint  102  and deploy the implantable medical device  104 . 
     In certain instances, the one or more fibers  106  release similar to a rip cord such that interlocking portions (e.g., overlapping fibers or knots) sequentially release along the length of the implantable medical device  104 . As is explained in greater detail below, the constraint  102  is formed by interlocking together the one or more fibers  106  directly on the implantable medical device  104 . The constraint  102  may be knitted together and then subsequently arranged about a constrained device or the constraint  102  is formed directly on the implantable medical device  104 . The expandable medical device  104  may be a stent, stent-graft, a balloon, or a similar device. 
       FIG. 2  is a side view of the device  104  including the constraint  102 , in accordance with an embodiment. As shown, the device  104  includes a delivery diameter D 1  and a deployed diameter D 2  (not shown) that is larger than the delivery diameter D 1 . The removable constraint  102  is attached to the device  104  at its delivery diameter D 1 . As shown, the constraint  102  includes at least two constraining fibers in the form of a warp knit. For example, the constraint  102  may include a first constraining fiber  110  and a second constraining fiber  112 . The first and/or the second constraining fiber(s)  110 ,  112  may operate, for example, as a deployment line  120  configured to release the constraint  102  and transition the device  104  from the delivery diameter D 1  to the deployed diameter D 2  in response to a force applied to the deployment line  120  (which may be coupled to one or more of the knot rows  114  as discussed in further detail below). 
     The device  104  may have a desired deployed diameter D 2  from about 5 mm-15 mm, or 6 mm-9 mm, or 6 mm-12 mm, 10 mm-20 mm, 15 mm-30 mm, 25 mm-45 mm, for example, and a delivery diameter D 1  that is less than the deployed diameter D 2 . For example, in some instances, a ratio of the delivery diameter D 1  of the device  104  to the deployed diameter D 2  (not shown) of the device  104  is less than about 0.3, less than about 0.29, less than about 0.28, less than about 0.27, or less than about 0.26. For reference, the term “diameter” is not meant to require a circular cross-section, and is instead to be understood broadly to reference a maximum transverse cross-sectional dimension of a device  104 . 
       FIG. 3  is an illustration of an example deployment apparatus, in accordance with an embodiment.  FIG. 3  shows aspects of the deployment apparatus including at least one constraining fiber  110 . In certain instances, the at least one constraining fiber  110  is looped onto itself to form a knit row  114 . In other instances, the at least one constraining fiber  110  includes a first constraining fiber  110  and a second constraining fiber  112 . For ease of illustration, the description of  FIG. 3  will refer to the first constraining fiber  110  and the second constraining fiber  112 . 
     In certain instances, the at least one constraining fiber  100  is arranged configured to form a warp knit surrounding a medical device. The warp knit is configured to separate and be removed to deploy the medical device. In addition, the at least one constraining fiber  100  may include a first series of loops forming the warp knit with at least one of the first series of loops  318  (one highlighted for ease of illustration) including a first portion  320  forming a knot  326  and a second portion  322  arranged in addition to the knot  326 . 
     In certain instances, the first constraining fiber  110  and the second constraining fiber  112  may form a constraint  102 . At a distal end of the constraint  102  (e.g., at a distal end of the knot row  114 ), the distal knot  326  may be formed by loops of the at least one constraining fiber  110  (or the first constraining fiber  110  and the second constraining fiber  112 ). In certain instances, the second constraining fiber  112  including a second series of multiple loops  324  (one highlighted for ease of illustration) and the first series of loops  318  and the second series of loops  324  form the knot row  114 . 
     As shown in  FIG. 3 , the first portion  320  of the series of loops  318  and the second portion  322  of the series of loops  318  are arranged through the second series of multiple loops  324 . The first portion  320  and the second series of multiple loops  324  may form knots in the knot row  114 . In certain instances, the distal knot  326  may include the first portion  320  of the series of loops  318  and the second portion  322  of the series of loops  318  with remaining knots in the knot row  114  not including the excess length of the second portion  322  of the series of loops  318 . For example, the first portion  320  of the series of loops  318  is of a length to form a knot with the second series of multiple loops  324 . The additional length provided by the second portion  322  of the series of loops  318  (in addition to the length for forming a knot) requires additional displacement of constraining fiber material to unknit the knot  326 . The additional displacement facilitates and resists premature deployment of the constraint  102 . In response to tension applied to a deployment line or the at least one constraining fiber  110 , the warp knit un-knits. The additional length provided by the second portion  322  of the series of loops  318  increases friction within needed to un-knit the knot  326  (or multiple knots in the knot row  114  having the additional length provided by the second portion  322  of the series of loops  318 ), which resists premature deployment. 
     In certain instances, the second portion  322  of the series of loops  318  includes a second loop with the first portion  318  being a first loop. In certain instances, the second portion  322  of the series of loops  318  (or the length in addition to the knot  326 ) is rotated or twisted relative to the knot  326 . In addition, the first series of loops  318  including the first portion  320  which form the knot  326  may be configured as to resist premature deployment of the medical device. 
       FIG. 4  is an illustration of an example deployment apparatus, in accordance with an embodiment. The constraint  102  is shown as a sheet of interwoven fibers, however, the constraint  102  may be arranged circumferentially about an implantable medical device. The constraint  102  can include a first constraining fiber  110  and a second constraining fiber  112  as described above with reference to  FIG. 3 . For example and as shown in  FIG. 4 , the constraint  102  includes a first constraining fiber  110 , a second constraining fiber  112 , a third constraining fiber  438 , and a fourth constraining fiber  440 . The constraining fibers  110 ,  112 ,  438 ,  440  may be arranged together to form multiple knot rows  114 ,  442 ,  444 ,  446 . In certain instances, the number of constraining fibers  110 ,  112 ,  438 ,  440    may be equal to the number of knot rows  114 ,  442 ,  444 ,  446 . In addition, the constraining fibers  110 ,  112 ,  438 ,  440  may be interwoven or interlocked with one another to form the knot rows  114 ,  442 ,  444 ,  446 . 
     In certain instances, the first row of knots  114  of the constraint  102  may be formed by the first constraining fiber  110  interwoven with the second constraining fiber  112 . As shown, the first constraining fiber  110  are interwoven with the second constraining fiber  112  to form the knot row  114  in a warp knit. 
     In addition, the second row of knots  442  may be formed by the second constraining fiber  112  interwoven with the third constraining fiber  438 . The second constraining fiber  112  may be interwoven with the third constraining fiber  438  to form the row of knots  442 . Further, the third row of knots  444  may be formed by the third constraining fiber  438  interwoven with the fourth constraining fiber  440 , and the fourth row of knots  446  may be formed by the fourth constraining fiber  440  interwoven with the first constraining fiber  110 . 
     In certain instances, each of the knot rows  114 ,  442 ,  444 ,  446  may be a warp knit when the constraint  102  is surrounding the medical device in the constrained configuration. As described above with reference to  FIG. 3 , the constraint  102  may be formed by one or more constraining fiber  110 . To deploy the constraint  102  from the constrained configuration, tension may be applied to one of the constraining fibers  110 . In certain instances, a knot  326  may be formed within the warp knit with at least one of a first series of loops  318  including a first portion  320  and a second portion  322  arranged in addition to the knot  326 . In certain instances, the knot  326  may be at a distal end of the constraint  102  or knot row  114 . The knot  326 , and all knots in the knot row  114 , may be formed with loops  324  (one highlighted for ease of illustration) formed by the second constraining fiber  112 . 
     In certain instances, the second series of loops  324  of the second constraining fiber  112  may also include a first portion  448  and a second portion  450  arranged in addition to the knot  326 . Each of the second portions  322 ,  450  may include a length of the constraining fibers  110 ,  112  that extend beyond a length of the constraining fibers (e.g., first portions  320 ,  448 ) forming the knot  326 . In certain instances, the second series of loops  324  may be a single loop as shown in  FIG. 3 . In addition, each knot in the knot row  114  may include the additional length second portions  322 ,  450 . In other instances, only the first constraining fiber  110  or the second constraining fiber may include the additional length second portions  322 ,  450 . 
     In certain instances, the knots  326  may be a slip knot. In addition, the knot  326  or knots may be configured as to resist premature deployment of the medical device. Further, the other knot rows  442 ,  444 ,  446  may be similarly configured to include excess length in addition to the knots of the knot rows  442 ,  444 ,  446 . 
     The warp knit pattern of the constraint  102  shown in  FIG. 4  (which may include a single knot  326 , multiple knots of a single knot row  114 , single distal knots  326  in multiple knot rows  114 ,  442 ,  444 ,  446 , or multiple knots in multiple knot rows  114 ,  442 ,  444 ,  446  with second portions or excess length) reduces premature deployment or mis deployment when the constraint  102  is un-knit. The excess length or longer loops, for example, require additional displacement in order to un-knit them. The longer loops are created by doubling the loop around the previously created loop of a knot in the knot rows  114 ,  442 ,  444 ,  446 . Once a loop is un-knitted from the double loop, it may be become a twisted loop that can also be un-kitted. In order to un-knit the twisted loop, the loop must be pulled further than a loop made with a single loop. That additional length required to pull the double loop out may require additional circumferential displacement in order to self un-knit the construct and therefore reduce the potential for premature deployment (e.g., self un-kitting or accelerated deployment). 
       FIG. 5A  is an image of a delivery system  10  in a delivery configuration, in accordance with an embodiment.  FIG. 5B  is an image of a delivery system  10  in a semi-deployed configuration, in accordance with an embodiment. As shown, disrupting one of the constraining fibers (e.g., the second constraining fiber  112 , for example) of a knot row initiates unravelling of at least a portion of the constraint  102 , as shown in  FIG. 5B . 
     The inventive concepts of this application have been described above both generically and with regard to specific embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments without departing from the scope of the disclosure. Thus, it is intended that the embodiments cover the modifications and variations of the inventive concepts provided they come within the scope of the appended claims and their equivalents.