Restraint system and related methods

Abstract

To provide a good system for delivering implantable medical devices. Various aspects of the present disclosure are directed to apparatus, systems, and methods including an implantable medical device and a removable restraint 102. The removable restraint includes at least two interlocking strands 112 having different strand characteristics that can be positioned and configured to releasably restrain the implantable medical device.

Description

Technical Field

[0001] Cross-Reference to Related Applications This application claims the benefit of Provisional Application No. 62 / 741,937, filed Oct. 5, 2018, and also claims the benefit of Provisional Application No. 62 / 737,040, filed Sep. 26, 2018, the entire contents of both of which are referenced herein for all purposes and incorporated into this specification.

[0002] Field The present disclosure generally relates to apparatuses, systems, and methods including a cover used for delivery of an implantable medical device. More specifically, the present disclosure relates to apparatuses, systems, and methods including a cover for constraining an expandable implantable medical device during delivery of the device. Background Art

[0003] Background Stents and stent-grafts can be used to radially support various tubular pathways in the body, including arteries, veins, airways, the gastrointestinal tract, and the biliary tract. Preferred methods for placing these devices use specialized delivery systems to accurately position and deploy the device at the treatment site. These delivery systems allow the practitioner to minimize trauma and technical difficulties associated with device placement. Attributes of delivery systems include low profile, the ability to pass through an introducer sheath, the ability to navigate a tortuous vasculature smoothly and atraumatically, protection of the constrained device, and the ability to accurately position and deploy the device.

[0004] A stent or stent-graft may be expanded and plastically deformed to deploy from a collapsed or constrained delivery diameter to an expanded and deployed diameter by using an inflatable balloon (e.g., a balloon-expandable stent), or may self-expand and elastically recover (e.g., a self-expandable stent).

[0005] These stents and stent graft devices may be held, compressed, or constrained in the delivery configuration before and during delivery to the target location. [Overview of the project]

[0006] Abstract In one example ("Example 1"), the delivery system includes an implantable medical device and a removable restraint configured to be positioned around the implantable medical device and to be releasably restrained, the removable restraint comprising at least two interlock strands, the first interlock strand having different strand properties from a second interlock strand, the first interlock strand comprising an unfolding line configured to release the removable restraint in response to a force applied to the unfolding line.

[0007] In another example ("Example 2"), in addition to the delivery system of Example 1, the ratio of the delivery diameter of the implantable medical device to the unfolded diameter is less than 0.3.

[0008] In another example ("Example 3"), in addition to any one of the delivery systems in Examples 1-2, the different strand characteristics include strand thickness.

[0009] In another example ("Example 4"), in addition to one of the delivery systems from Examples 1-2, the different strand characteristics include strand denier.

[0010] In another example ("Example 5"), in addition to one of the delivery systems from Examples 1-2, the different strand characteristics include a strand friction coefficient.

[0011] In another example ("Example 6"), in addition to any one of the delivery systems in Examples 1-2, the different strand properties include strand material.

[0012] In another example ("Example 7"), in addition to one of the delivery systems from Examples 1-2, the different strand characteristics include strand stiffness.

[0013] In another example ("Example 8"), in addition to any one of the delivery systems in Examples 1 to 7, the implantable medical device has a radial force at the delivery diameter of the implantable medical device, and the two interlock strands are adapted to be removed by a knitting force applied to the deployment line, with the ratio of the radial force to the knitting force being approximately 100 to approximately 500.

[0014] In another example ("Example 9"), in addition to the delivery system of Example 8, the ratio of the radial force to the nit force is approximately 170 to approximately 475.

[0015] In another example ("Example 10"), in addition to the delivery system of Example 8, the ratio of the radial force to the nit force is approximately 225 to approximately 450.

[0016] In another example ("Example 11"), in addition to the delivery system of Example 8, the ratio of the radial force to the nit force is approximately 200 to approximately 425.

[0017] In another example ("Example 12"), the delivery system includes an implantable medical device and a removable restraint configured to be positioned around the implantable medical device and to be releasably restrained, the removable restraint comprising at least two interlock strands, the at least two interlock strands comprising a first interlock strand and a second interlock strand, the first interlock strand and the second interlock strand differing from each other in at least one strand characteristic.

[0018] In another example ("Example 13"), in addition to the delivery system of Example 12, the first interlock strand has strand characteristics different from the second of at least two interlock strands.

[0019] In another example ("Example 14"), in addition to any one of the delivery systems in Examples 12-13, the first interlock strand is a deployment line configured to release the removable restraint in response to a force applied to the deployment line.

[0020] In another example ("Example 15"), the expandable medical device includes an implantable medical device having a delivery diameter, an unfolding diameter, and a radial force at the delivery diameter, a removable restraint attached to the implantable medical device at its delivery diameter, the removable restraint comprising a plurality of interlock strands in the form of warp knits, the removable restraint being configured to be remotely removed when an unfolding force is applied to the unfolding line, the plurality of interlock strands comprising a first strand and a second strand, the first strand and the second strand differing from each other in at least one strand characteristic, and the ratio of the radial force to the unfolding force being approximately 150 to approximately 500.

[0021] In another example ("Example 16"), in addition to the delivery system of Example 15, the different strand characteristics include at least one of strand thickness, strand denier, strand friction coefficient, strand material, and strand stiffness.

[0022] In another example ("Example 17"), in addition to the delivery system of Example 16, the different strand characteristic is the strand thickness, where the difference between the cross-sectional diameter of the first strand and the cross-sectional diameter of the second strand is approximately 0.0025 square inches.

[0023] In another example ("Example 18"), in addition to the delivery system of Example 16, said different strand property is strand thickness, and the strand thickness of said first strand and said second strand differs by from about 0.0005 inches to about 0.008 inches.

[0024] In another example ("Example 19"), in addition to the delivery system of any one of Examples 15 to 18, the ratio of the delivery diameter of said implantable medical device to the deployed diameter thereof is about 0.3.

[0025] In another example ("Example 20"), in addition to the delivery system of any one of Examples 15 to 19, the ratio of said radial force to said knitting force is less than about 450. Brief Description of the Drawings

[0026] Brief Description of the Drawings The accompanying drawings are included to provide a further understanding of the present disclosure, are incorporated in and constitute a part of the present specification, illustrate embodiments, and together with the description, serve to explain the principles of the present disclosure.

[0027] [Figure 1] Figure 1 is a top view of a delivery system including a catheter with a removable restraint according to an embodiment.

[0028] [Figure 2] Figure 2 is a side view of an implantable medical device including a removable restraint according to an embodiment.

[0029] [Figure 3] Figure 3 is a schematic diagram of interlocked strands according to an embodiment.

[0030] [Figure 4] Figure 4 is an end view of a removable restraint showing an exemplary knot row according to an embodiment.

[0031] [Figure 5] Figure 5 is an end view of a removable restraint body showing an exemplary row of knots according to an embodiment.

[0032] [Figure 6] Figures 6A to 6B are images of the delivery system in a delivery configuration and a semi-deployed configuration, respectively, according to the embodiment.

[0033] [Figure 7] Figure 7 is a graph comparing the knitting force required for the development of implantable medical devices. [Modes for carrying out the invention]

[0034] In terms of the range of measurement as used herein, “about” and “near” are interchangeable and are used to refer to a measured value, which includes and may include a measured value that is reasonably close to the stated measured value, but may differ by a reasonably small amount, as will be understood and readily apparent to those skilled in the art, due to measurement errors, differences in calibration of the measuring and / or manufacturing equipment, human error in reading and / or setting the measured value, adjustments made to optimize performance and / or structural parameters considering differences in measured values ​​related to other components, specific implementation scenarios, inaccurate adjustment and / or handling of the object by person or machine, etc.

[0035] The embodiments described above are merely examples and should not be read to limit or otherwise narrow any scope of the concepts of the invention provided otherwise by this disclosure. Although several examples are disclosed, further embodiments will become apparent to those skilled in the art from the following detailed description, which illustrates exemplary examples. Accordingly, the drawings and detailed description should be considered illustrative rather than restrictive.

[0036] Detailed explanation Those skilled in the art will readily understand that various aspects of this 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 drawings referenced herein are not necessarily drawn to a fixed scale and may be exaggerated to illustrate various aspects of this disclosure; in this respect, the drawings should not be construed as limiting.

[0037] Various aspects of this disclosure relate to apparatus, systems, and methods for forming or manufacturing restraint mechanisms. The restraint mechanism is configured to hold, compress, or restrain an implantable medical device (e.g., a stent, stent graft, balloon, or other expandable medical device) in a delivery configuration before and during delivery to a target location. In certain examples, the restraint mechanism comprises one or more fibers.

[0038] Restraint mechanisms according to various aspects of this disclosure can be formed or manufactured directly on an implantable medical device. One or more fibers are woven, sewn, or interlocked to form a restraint mechanism. Thus, one or more fibers are woven, sewn, or interlocked together around or periphery of an implantable medical device. As described above, the implantable medical device is contracted, folded, or restrained to a contracted (delivery) diameter by a restraint mechanism for delivery to a target location to the patient, where it is unfolded or expanded to an unfolded diameter (larger than the contracted diameter).

[0039] Figure 1 is a top view of a delivery system 10 including a catheter 100 with a removable restraint 102, according to several embodiments. As shown in Figure 1, the removable restraint 102 is configured to restrain an implantable medical device 104 to the delivery configuration. The removable restraint 102 may include one or more fibers 106 arranged around the device 104 to maintain the removable restraint 102 in the restraint configuration.

[0040] A removable restraint 102 is positioned along the length of the device 104. The removable restraint 102 is also positioned circumferentially around the device 104 and can substantially cover the device 104 for delivery. One or more fibers 106 are positioned within the lumen (not shown) of the catheter 100 and may extend toward the proximal end of the catheter 100 which is positioned outside the patient during the delivery of the device 104. One or more fibers 106 include a proximal end 108 to which the user can apply tension to release the removable restraint 102 and deploy the device 104.

[0041] In certain examples, one or more fibers 106 are released in a manner similar to a rip cord, such that the interlocking portion (e.g., overlapping fibers or knots) is sequentially released along the length of the device 104. As described in more detail below, the removable restraint 102 is formed by directly interlocking one or more fibers 106 on the device 104. The device 104 can be a stent, stent graft, balloon, or similar device.

[0042] Figure 2 is a side view of a device 104 including a removable restraint 102 according to an embodiment. As shown, the device 104 includes a delivery diameter D1 and an unfolding diameter D2 (not shown) that is larger than the delivery diameter D1. The removable restraint 102 is positioned around the device 104 at the delivery diameter D1. As shown, the removable restraint 102 includes at least two interlock strands in the form of a warp knit. For example, the removable restraint 102 may include a first interlock strand 110 and a second interlock strand 112. The first interlock strand and / or the second interlock strands 110, 112 act, for example, as an unfolding line 120, which is configured to release the removable restraint 102 and, in response to a knitting force applied to the unfolding line 120, release the device 104 from the delivery diameter D1 to the unfolding diameter D2.

[0043] Device 104 may have a desired unfolded diameter D2 of, for example, about 5 mm to 15 mm, or 6 mm to 9 mm, or 6 mm to 12 mm, and a delivery diameter D1 smaller than the unfolded diameter D2. For example, in some cases, the ratio of the delivery diameter D1 of device 104 to the unfolded diameter D2 (not shown) of 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.

[0044] In some examples, the first interlock strand 110 has at least one strand characteristic that is different from the second interlock strand 112, which is necessary to release the removable restraint 102. It can be added to the development line. This can affect the amount of knitting force. Examples of different strand properties include strand thickness, strand denier, strand friction coefficient, strand material, and / or strand stiffness.

[0045] For example, the first interlock strand 110 may have a first diameter or thickness, and the second interlock strand 112 may have a second diameter or thickness that is larger than the first diameter. In various examples, using a larger diameter or thickness for the second interlock strand 112 helps to increase friction between the first and second interlock strands 110, 112, which in turn helps to maintain the device 104 in a delivery configuration. In some examples where the different strand characteristics are strand diameter or thickness, the first and second interlock strands 110, 112 may have cross-sectional diameters or thicknesses that vary by about 0.0015 cm (0.0006 inches). In other examples, the cross-sectional diameter can vary by approximately 0.0008 cm, 0.0009 cm, 0.0010 cm, 0.0011 cm, 0.0012 cm, 0.0013 cm, 0.0014 cm, 0.0015 cm, 0.0016 cm, 0.0017 cm, 0.0018 cm, 0.0019 cm, 0.0020 cm, 0.0021 cm, 0.0022 cm, or any value in between. Furthermore, the difference in diameter between the first interlock strand and the second interlock strands 110 and 122 can be approximately 0.0005 inches to approximately 0.008 inches. For reference, the term “diameter” should be broadly understood to refer to the maximum cross-sectional dimension or effective diameter of the strand, rather than requiring a circular cross-section.

[0046] For reference, the term "diameter" should be broadly understood to refer to the maximum cross-sectional dimension of the strand, rather than intending to require a circular cross-section.

[0047] In various examples, the first interlock strand 110 may include a first material, and the second interlock strand 112 may include a second material different from the first material (e.g., as a substitute for or as an additional feature of different diameters between strands). In particular cases, the first interlock strand 110 may include a material having a different (e.g., higher or lower) tensile strength compared to the tensile strength of the material of the second interlock strand 112. Additionally or alternatively, the first interlock strand 110 may include a material having a different (e.g., higher or lower) surface roughness compared to the surface roughness of the material of the second interlock strand 112. Furthermore, the first interlock strand 110 may include a material having a different (e.g., higher or lower) tackiness or adhesion to other materials compared to the tackiness or adhesion of the material of the second interlock strand 112. In various examples, the first and second strands 110 and 112 exhibit different static and / or kinetic friction coefficients, with the second strand 112 exhibiting, for example, a relatively higher static and / or kinetic friction coefficient than the first strand 110. From the above, it should be understood that the strands 110 and 112 may include several different properties. For example, the first interlock strand 110 may have a different (e.g., higher or lower) tensile strength and a different (e.g., higher or lower) surface roughness compared to the second interlock strand 112.

[0048] Potential materials for the strands 110 and 112 discussed herein include, for example, polytetrafluoroethylene (PTFE), ePTFE, fluoropolymers such as polyester, polyurethane, and perfluoroelastomers, polytetrafluoroethylene, silicone, urethane, ultra-high molecular weight polyethylene, aramid fibers, and combinations thereof. Other embodiments for the strands 110 and 112 may include high-strength polymer fibers such as ultra-high molecular weight polyethylene fibers (e.g., Spetra®, Dyneema Purity®, etc.) or aramid fibers (e.g., Technora®, etc.). In general, any of the above properties can be evaluated using ASTM or other recognized measurement techniques and standards, as can be understood by those skilled in the art.

[0049] In certain examples, the first interlock strands and the second interlock strands 110, 112 may be made of the same material, but in other embodiments they may be different. For example, one of the strands may contain a filler or core material and may be surface-treated, among other things, by etching, deposition, or crowning or other plasma treatment, and may be coated with a suitable coating material. Using different strand materials for the strands 110, 112, as well as different diameters, may increase friction between the first interlock strands and the second interlock strands 110, 112, which may help maintain the device 104 in a delivery configuration.

[0050] Device 104 has a radial force at the delivery diameter D1. The radial force generally refers to the force caused by device 104 acting on a removable restraint 102 at any point during the deployment of device 104. As described above, the interlock strands 110, 112 are adapted to be detached when a deployment force is applied to the deployment line 120. In some examples, the ratio of this radial force of device 104 to the nit force applied to the deployment line 120 is less than approximately 500. In other examples, the ratio of this radial force of device 104 to the nit force applied to the deployment line 120 is less than approximately 475. Furthermore, the ratio of this radial force of device 104 to the nit force applied to the deployment line 120 can be less than approximately 450. Furthermore, in other examples, the ratio of this radial force of device 104 to the nit force applied to the deployment line 120 is less than approximately 425. Furthermore, the ratio of the radial force to the nit force can be, for example, about 10, 20, 30, 40, 50, 100, 200, 300, 400 (or any number in between) to about 500, about 10, 20, 30, 40, 50, 100, 200, 300, 400 (or any number in between) to about 475, about 10, 20, 30, 40, 50, 100, 200, 300, 400 (or any number in between) to about 450, or about 10, 20, 30, 40, 50, 100, 200, 300, 400 (or any number in between) to about 425.

[0051] Figure 3 is a schematic diagram of the interlock strands of the removable restraint 102 (Figures 1-2) according to an embodiment. The interlock strands (for example, the first interlock strand and the second interlock strands 110, 112 as shown) are generally woven together to form at least one knot row 114. As shown, the knot row 114 is formed from interlock loops formed from the first interlock strand and the second interlock strands 110, 112. For example, the first interlock loop 116 is formed from the first interlock strand 110 and woven together with the second interlock loop 118 formed from the second interlock strand 112. This interlocked loop configuration applies an unfolding force (knit force) to the unfolding line 120. In addition This allows the detachable restraint body 102 (Figures 1-2) to be released.

[0052] In general, the knot rows 114 can be positioned at any location around the removable restraint 102. In certain examples, the interlock strands can form more than one knot row. Figure 4 is an end view of the removable restraint 102 showing an exemplary knot row 114 according to an embodiment. As shown, the first and second interlock strands 110, 112 can form the first knot row 122 and the second knot row 124, positioned at different locations around the removable restraint 102. For example, the knot rows can be spaced about 180 degrees apart from each other, about 90 degrees apart from each other, about 60 degrees apart from each other, or any other distance as needed.

[0053] Figure 5 is an end view of a removable restraint 102 showing an exemplary knot row 114 according to an embodiment. As shown, in some examples, the removable restraint 102 can include more than two interlock strands. For example, the removable restraint 102 can include, for example, a first interlock strand 130, a second interlock strand 132, a third interlock strand 134, and a fourth interlock strand 136. In these examples, the removable restraint 102 can also include a first knot row 140, a second knot row 142, a third knot row 144, and a fourth knot row 146, corresponding to the first through fourth interlock strands 130-136, respectively. Applying force to one of the first through fourth interlock strands 130-136 can initiate the unraveling of the corresponding knot row, thus allowing for the selective deployment of different parts of the removable restraint 102.

[0054] In some examples, at least one of the interlock strands may have different strand properties from the remaining interlock strands. For example, the first, second, and third strands 130, 132, and 134 may have the same strand properties, while the fourth strand 136 may have different strand properties. In other examples, two of the interlock strands may have one strand property, while the remaining strand may have a second strand property different from the first strand property, and so on. In some examples, each of the interlock strands may have different strand properties, if desired, to facilitate the selective deployment of different parts of the removable restraint 102. In a particular example, one of the interlock strands 130, 132, 134, and 136 may have different properties from its adjacent counterparts.

[0055] As described above, the knot rows can be positioned at any location around the removable restraint 102. In Figure 5, the knot rows are positioned approximately 90 degrees apart from each other, but they can be spaced apart by any amount as desired. For example, the knot rows can be spaced 60 degrees, 45 degrees, or less from each other to achieve a desired unfolded length ratio.

[0056] In some cases, having interlock strands with different properties can reduce the tilt of device 104 before release. For example, interlock strands can reduce the tilt (unfolding angle) of device 104 before the knots of the knot row 114 are released in sequence. The tilt of device 104 can lead to advanced or pre-deployment of device 104 before the intended deployment.

[0057] Figures 6A and 6B are images of the delivery system in a fully deployed and partially deployed configuration, respectively, according to the embodiment. As shown in Figure 6A, the removable restraint 102 is attached to the device 104 at its delivery diameter D1. During deployment, a knitting force is applied to the deployment line 120, releasing the removable restraint 102 by untying the knot row 114, as shown in Figure 5B. Once the removable restraint 102 is released, the device 104 is released to its deployment diameter D2.

[0058] Interlock strands 110 and 112, having different properties, can reduce the tilt of device 104 before release. For example, interlock strands 110 and 112 can reduce the tilt (or unfolding angle) of device 104 before the knots of the knot row 114 are released sequentially. Device 104 begins to expand to a larger diameter after the release of the restraining mechanism 102. Device 104 may have an angle A between the portion held by the restraining mechanism 102 and the expanded portion or the portion beginning to expand. Due to angle A and the force expended by device 104 to unfold to unfold diameter D2, the previous restraint may shift due to the tilt or expansion of the portion of device 104. However, different strand properties can reduce the tilt of device 104 by maintaining the position of each knot relative to device 104 as the knots are released sequentially, thereby reducing unwanted unfolding of device 104 (e.g., accelerated unfolding or pre-unfolding), as described in detail above.

[0059] Figure 7 is a graph comparing the knitting force for the deployment of implantable medical devices as discussed herein. The knitting force is the force applied to the deployment line to remove the knitted loop from within the surrounding knitted loop and to eliminate accelerated deployment. As shown in Figure 7, as the knitting force increases, accelerated deployment (AD) decreases. Methods for achieving increased knitting force are described herein. This is evident when the constrained diameter / expanded diameter ratio is less than 0.3, or when the device has a larger nominal diameter (including 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm and larger, including 25mm, 30mm, 40mm and 50mm).

[0060] The invention of this application has been described above, both in general and with respect to specific embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made in embodiments without departing from the scope of this disclosure. Accordingly, the embodiments are intended to cover modifications and variations of the invention, insofar as they fall within the scope of the appended claims and equivalent forms thereof. (Appearance) (Aspect 1) Implantable medical devices, and, A removable restraint body configured to be positioned around the implantable medical device and to be releasably restrained, A delivery system including, A delivery system in which the removable restraint comprises at least two interlock strands, including a first interlock strand having different strand characteristics from a second interlock strand, the first interlock strand being a deployment line configured to release the removable restraint in response to a force applied to the deployment line. (Aspect 2) The delivery system according to embodiment 1, wherein the ratio of the delivery diameter of an implantable medical device to its unfolded diameter is less than 0.3. (Aspect 3) The delivery system according to any one of embodiments 1 to 2, wherein the different strand characteristics include strand thickness. (Aspect 4) The delivery system according to any one of embodiments 1 to 2, wherein the different strand characteristics include strand denier. (Appendix 5) The delivery system according to any one of embodiments 1 to 2, wherein the different strand characteristics include the strand friction coefficient. (Aspect 6) The delivery system according to any one of embodiments 1 to 2, wherein the different strand properties include strand material. (Aspect 7) The delivery system according to any one of embodiments 1 to 2, wherein the different strand characteristics include strand stiffness. (Pattern 8) The delivery system according to any one of embodiments 1 to 7, wherein the implantable medical device has a radial force at the delivery diameter of the implantable medical device, and the at least two interlock strands are adapted to be removed by a knitting force applied to the deployment line, and the ratio of the radial force to the knitting force is about 100 to about 500. (Aspect 9) The delivery system according to embodiment 8, wherein the ratio of the radial force to the knitting force is approximately 170 to approximately 475. (Aspect 10) The delivery system according to embodiment 8, wherein the ratio of the radial force to the knitting force is approximately 225 to approximately 450. (Aspect 11) The delivery system according to embodiment 8, wherein the ratio of the radial force to the knitting force is approximately 200 to approximately 425. (Aspect 12) Implantable medical devices, and, A removable restraint body configured to be positioned around the implantable medical device and to be releasably restrained, A delivery system including, A delivery system comprising a removable restraint body including at least two interlock strands, wherein the at least two interlock strands include a first interlock strand and a second interlock strand, and the first interlock strand and the second interlock strand differ from each other in at least one strand characteristic. (Aspect 13) The delivery system according to embodiment 12, wherein the first interlock strand has strand characteristics different from those of the second of at least two interlock strands. (Aspect 14) The delivery system according to any one of embodiments 12 to 13, wherein the first interlock strand is a deployment line configured to release the removable restraint in response to a force applied to the deployment line. (Aspect 15) An implantable medical device having a delivery diameter, an expanded diameter, and radial force at the delivery diameter. A removable restraint attached to the implantable medical device at its delivery diameter, An expandable medical device including, The removable restraint comprises a plurality of interlock strands in the form of warp knits, and the removable restraint is configured to be remotely removed when an unfolding force is applied to the unfolding line. The plurality of interlock strands include a first strand and a second strand, and the first strand and the second strand differ from each other in at least one strand characteristic. An expandable medical device in which the ratio of the radial force to the deployment force is approximately 150 to approximately 500. (Aspect 16) The expandable medical device according to embodiment 15, wherein the different strand characteristics include at least one of strand thickness, strand denier, strand friction coefficient, strand material, and strand stiffness. (Aspect 17) The expandable medical device according to embodiment 16, wherein the different strand characteristic is the strand thickness, where the difference between the cross-sectional diameter of the first strand and the cross-sectional diameter of the second strand is approximately 0.0025 square inches. (Aspect 18) The different strand characteristics are strand thickness, and the strand thicknesses of the first strand and the second strand differ by about 0.0005 inches to about 0.008 inches, in the expandable medical device according to embodiment 16. (Aspect 19) An expandable medical device according to any one of embodiments 15 to 18, wherein the ratio of the delivery diameter of the implantable medical device to the unfolded diameter is approximately 0.3. (Aspect 20) An expandable medical device according to any one of embodiments 15 to 19, wherein the ratio of the radial force to the nit force is less than approximately 450.

Claims

1. Implantable medical devices, and, A removable restraint body configured to be positioned around the implantable medical device and to be releasably restrained, A delivery system including, The removable restraint comprises four interlock strands, the four interlock strands being woven together around or near the implantable medical device to restrain the implantable medical device, the first and second interlock strands of the four interlock strands having the same strand properties, the third and fourth interlock strands having the same strand properties, and the first and second interlock strands having the same strand properties. A delivery system in which the strand properties differ from those of the third and fourth interlock strands, wherein the strand properties are at least one of strand thickness, strand denier, strand friction coefficient, strand stiffness, strand tensile strength, strand tackiness or strand adhesion, and strand surface roughness, and each of the four interlock strands is operable to initiate unraveling of the corresponding knot row via an unraveling force applied to one of the four interlock strands to selectively unravel the portion of the removable restraint.

2. The delivery system according to claim 1, wherein the ratio of the delivery diameter of an implantable medical device to its unfolded diameter is less than 0.

3.

3. The delivery system according to any one of claims 1 to 2, wherein the different strand characteristics include strand denier.

4. The delivery system according to any one of claims 1 to 2, wherein the different strand characteristics include the strand friction coefficient.

5. The delivery system according to any one of claims 1 to 2, wherein the different strand properties include strand material.

6. The delivery system according to any one of claims 1 to 2, wherein the different strand characteristics include strand stiffness.

7. The delivery system according to any one of claims 1 to 6, wherein the implantable medical device has a radial force at the delivery diameter of the implantable medical device, and the four interlock strands are adapted to be removed by an unfolding force applied to an unfolding line which is one of the four interlock strands, and the ratio of the radial force to the unfolding force is 100 to 500.

8. The delivery system according to claim 7, wherein the ratio of the radial force to the deployment force is 170 to 475.

9. The delivery system according to claim 7, wherein the ratio of the radial force to the deployment force is 225 to 450.

10. The delivery system according to claim 7, wherein the ratio of the radial force to the deployment force is 200 to 425.

11. Implantable medical devices, and, A removable restraint body configured to be positioned around the implantable medical device and to be releasably restrained, A delivery system including, A delivery system comprising: the removable restraint comprising at least four interlock strands, the at least four interlock strands being woven together around or periphery of the implantable medical device to restrain the implantable medical device, the at least four interlock strands comprising a first set of interlock strands and a second set of interlock strands, the first set of interlock strands and the second set of interlock strands differing from each other in strand properties, the strand properties being at least one of strand thickness, strand denier, strand friction coefficient, strand stiffness, strand tensile strength, strand tackiness or strand adhesion, and strand surface roughness, and each of the interlock strands being operable to initiate unraveling of a corresponding knot row via an unraveling force applied to one of the at least four interlock strands to selectively unravel a portion of the removable restraint.

12. The delivery system according to claim 11, wherein the first set of interlock strands has different strand characteristics from the second set of interlock strands among at least four interlock strands.

13. The delivery system according to any one of claims 11 to 12, wherein the first set of interlock strands is a deployment line configured to release the removable restraints in response to a force applied to the deployment line.

14. An implantable medical device having a delivery diameter, an expanded diameter, and radial force at the delivery diameter. A removable restraint attached to the implantable medical device at its delivery diameter, An expandable medical device including, The removable restraint comprises a plurality of interlock strands in the form of a warp knit, the plurality of interlock strands knitted together around or periphery the implantable medical device to restrain the implantable medical device, and the removable restraint is configured to be remotely removed when an unfolding force is applied to an unfolding line which is one of the plurality of interlock strands. The plurality of interlock strands include a first set of strands and a second set of strands, the first set of strands and the second set of strands differ from each other in their strand properties, the strand properties being at least one of strand thickness, strand denier, strand friction coefficient, strand stiffness, strand tensile strength, strand tackiness or strand adhesion, and strand surface roughness. Each of the plurality of interlock strands is operable to initiate unraveling of the corresponding knot row via an unraveling force applied to one of the plurality of interlock strands in order to selectively unravel the portion of the removable restraint body, An expandable medical device in which the ratio of the radial force to the deployment force is 150 to 500.

15. The expandable medical device according to claim 14, wherein the strand characteristics include strand thickness, wherein the difference between the cross-sectional diameter of the first set of strands and the cross-sectional diameter of the second set of strands is 0.0064 cm (0.0025 inches).

16. The expandable medical device according to claim 14, wherein the strand characteristics include strand thickness, and the strand thicknesses of the first set of strands and the second set of strands differ by 0.0013 cm (0.0005 inches) to 0.020 cm (0.008 inches).

17. The expandable medical device according to any one of claims 14 to 16, wherein the ratio of the delivery diameter of the implantable medical device to the unfolded diameter is less than 0.

3.

18. The expandable medical device according to any one of claims 14 to 17, wherein the ratio of the radial force to the deployment force is less than 450.

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