Patent Description:
Aneurysms can be intravascularly treated by delivering a treatment device to the aneurysm to fill the sac of the aneurysm with embolic material and/or block the neck of the aneurysm to inhibit blood flow into the aneurysm. When filling the aneurysm sac, the embolic material can promote blood clotting to create a thrombotic mass within the aneurysm. When treating the aneurysm neck without substantially filling the aneurysm sac, blood flow into the neck of the aneurysm can be inhibited to induce venous stasis in the aneurysm and facilitate natural formation of a thrombotic mass within the aneurysm.

In some current treatments, multiple embolic coils are used to either fill the aneurysm sac or treat the entrance of the aneurysm neck. A common challenge among embolic coil treatments is that implanted coils and implanted portions of partially implanted coils can become entangled and difficult to reposition. In some instances, a physician may not be able to retract a partially implanted coil and may be forced to position the coil in a non-ideal location. Improperly positioning embolic coils at the aneurysm neck can potentially have the adverse effect of impeding the flow of blood in the adjoining blood vessel, particularly if the entrance and/or sac is overpacked. If a portion of the improperly placed coil becomes dislodged, it can enter the neighboring blood vessel and promote clot formation, which can ultimately lead to an obstruction that is tethered to the aneurysm and therefor extremely difficult to treat. Conversely, if the entrance and/or sac is insufficiently packed, blood flow can persist into the aneurysm.

In some current treatments, an embolic coil is attached to a tubular delivery device and delivered via a delivery catheter to an aneurysm. During delivery, the embolic coil can be engaged to the delivery member's implant detachment/deployment system (referred to herein equivalently as an "detachment system" or "deployment system"). When the embolic coil is in position, the deployment system can release the coil, the coil can be left implanted, and the delivery member can be retracted. Some treatments utilize a mechanical detachment/deployment system that can be actuated by a physician to release the implant by pulling one or more wires or other elongated members referred to generically herein as a "pull wire. " Some of the challenges that have been associated with delivering and deploying embolic coils with delivery members having mechanical detachment systems include premature release of a coil due to premature movement of the pull wire proximally, thereby releasing the coil before the system is at the treatment site. This is exacerbated because of the system moves through tortuous vasculature to the treatment site.

There is therefore a need for improved methods, devices, and systems to facilitate implantation of embolic coils and other implants facing similar challenges.

The disclosure of <CIT> provides a detachment system for delivering an implantable medical device to a target location of a body vessel that has a generally hollow distal tube. The distal tube includes a proximal end, a distal end, and a compressible portion of the tube itself, between the proximal and distal ends which is axially movable from a compressed to an elongated condition. A generally hollow proximal tube has a proximal end and a distal end. An engagement system engages and deploys the implantable medical device engaged at the distal end of the distal tube. The engagement system moves the compressible portion to the compressed condition when engaging the implantable medical device, and deploys the implantable medical device and releases the compressible portion to the elongated condition.

The disclosure of <CIT> relates to embolic implants for use in the minimally-invasive treatment of aneurysms and other vascular disorders.

In some examples presented herein, premature proximal movement or translation of a pull wire can be decreased by providing a loop wire that twists one or more times around the pull wire, thereby providing a greater amount of friction against the pull wire.

A detachment system for delivering an implantable medical device to a target location of a body vessel can include a tubular body comprising a lumen extending therethrough and a compressed distal tube. The detachment system can include a loop wire comprising a first end attachment and a second end attachment affixed to the tubular body. The loop wire can further include a loop opening positioned proximate a distal end of the compressed distal tube. The detachment system can include a pull wire extending through the lumen and through the loop opening. The loop wire can include a twist such that that the loop wire is twisted at least one time around the pull wire to increase friction between the loop wire and the pull wire.

The loop wire can be twisted a single time around the pull wire, while in other examples the loop wire can be twisted a plurality of times around the pull wire. Additional twists can increase the friction/tightness of the junction between the pull wire and the loop wire.

The loop wire can include a friction coating proximate the pull wire to increase the friction between the pull wire and loop wire.

The loop wire and the pull wire can be movable to release the implantable medical device from the detachment system.

The twist can inhibit premature detachment of the implantable medical device by inhibiting proximal translation of the pull wire due to frictional resistance provided by the loop wire via the twist.

The tubular body can include a flexible coil disposed in a proximal direction from the compressed distal tube. The loop wire can inhibit elongation of the flexible coil when looped over the pull wire.

The detachment system can include a key affixed to the implantable medical device proximate a proximal end of the implantable medical device. The detachment system can include a stretch resistant fiber engaged to the key, extended through an implant lumen of the implantable medical device, and affixed to the implantable medical device proximate a distal end of the implantable medical device. The key can include a distal opening therethrough, wherein the stretch resistant fiber passes through the distal opening. The key can include a proximal opening therethrough. The key can include a bridge separating the distal opening and the proximal opening. The bridge can support a portion of the pull wire in a distal direction from the loop opening. The twist can be positioned on the loop wire proximal to the bridge.

The pull wire can be weaved across the bridge such that the pull wire passes from a first side of the key, through the proximal opening to a second side of the key and across the bridge, and through the distal opening to the first side of the key.

A detachment system for delivering an implantable medical device to a target location of a body vessel can include a pull wire extending through a tubular body of the detachment system. The detachment system can include a loop wire looped over the pull wire at a distal end of the loop wire and twisted at least once around the pull wire. A twist in the loop wire can inhibit premature detachment of the implantable medical device by inhibiting proximal translation of the pull wire relative to a loop opening in the distal end of the loop wire.

The detachment system can include a compressed distal tube. The tubular body can include a flexible coil disposed in a proximal direction from the compressed distal tube. The loop wire can inhibit elongation of the flexible coil when looped over the pull wire.

The detachment system can include a key affixed to the implantable medical device proximate a proximal end of the implantable medical device. The detachment system can include a stretch resistant fiber engaged to the key, extended through an implant lumen of the implantable medical device, and affixed to the implantable medical device proximate a distal end of the implantable medical device. The key can include a distal opening therethrough, wherein the stretch resistant fiber can pass through the distal opening. The key can include a proximal opening therethrough. The key can include a bridge separating the distal opening and the proximal opening. The bridge can support a portion of the pull wire in a distal direction from the loop opening. The twist can be positioned on the loop wire proximal to the bridge.

A method for constructing a detachment system with an embolic implant and optionally deploying the implant, wherein the method for deploying the implant does not form part of the present invention, can include providing a tubular body comprising a lumen extending therethrough and a compressible distal tube. The method can include affixing a loop wire to the tubular body. The method can include compressing the compressible distal tube. The method can include positioning a loop opening in the loop wire proximate a distal end of the compressible distal tube such that the loop wire is extended through the lumen. The method can include extending a pull wire through the lumen. The method can include extending the loop opening through a key of an implantable medical device. The method can include twisting the loop wire around the pull wire at least one time. The method can include extending a distal end of the pull wire through the loop opening of the twisted loop wire.

The method to deploy the implant does not form part of the present invention and can include inhibiting, via frictional resistance of the twisted loop wire around the pull wire, translation of the pull wire through the loop wire while the implantable medical device is delivered through vasculature to a treatment site. The method can include overcoming frictional resistance such that the pull wire translates proximally and releases the implantable medical device at the treatment site.

The above and further aspects of this disclosure are further discussed with reference 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 principles of the disclosure. The figures depict one or more implementations of the inventive systems and devices, by way of example only, not by way of limitation.

An object of the present disclosure is to decrease the occurrence of or ultimately prevent premature detachment of an embolic coil from a detachment system prior to placing the coil at a treatment site, i.e., an aneurysm. More specifically, it is an object of the present disclosure to provide additional support to the junction between a loop wire and a pull wire of the detachment system. Certain current designs for embolic coil delivery systems can include a tubular body having a compressed distal tube that, once released from compression, delivers the embolic coil to a treatment site. Within that distal tube (also referred to herein as a "distal hypotube") runs both a loop wire and a pull wire. The loop wire can extend into a detachment features (also referred to herein as a "key") of the implant and loop onto the pull wire to secure the distal hypotube into its compressed state, while also containing the embolic coil that is attached to the key. One common pitfall to prior designs is that there is a chance that the pull wire can prematurely translate proximally from the loop wire, for example, as a physician is delivering the device through tortuosity and reactive frictional forces cause the pull wire to retract. Premature detachment of the detachment system from the embolic coil can be a significant problem, as the physician no longer controls the timing of the detachment of the embolic coil into the aneurysm. The present devices, systems, and methods provide a solution to early, inadvertent deployment of the embolic coil.

Referring to the figures, <FIG> is an illustration of a delivery/detachment system <NUM> and an implantable medical device <NUM> (which is an embolic coil in the example shown), according to the present invention. The implantable medical device <NUM> is also referred to herein as implant <NUM>. The detachment system <NUM> can include a proximal tube <NUM>, a coiled section <NUM> comprising a support coil <NUM>, a distal tube <NUM>, a sleeve <NUM> surrounding the coiled section <NUM>, a loop wire <NUM> extending through the coiled section <NUM>, and a pull wire <NUM> extending through the coiled section <NUM>. A distal end <NUM> of the pull wire <NUM> can extend at least partially beyond a proximal portion of a key <NUM> (also referred to herein as "detachment feature") of the implant <NUM>. The detachment system <NUM> can have a tubular body <NUM> that is formed by the proximal tube <NUM>, the coiled section <NUM> comprising the support coil <NUM>, and the distal tube <NUM>. When the distal tube <NUM> is compressed, as will be described below for when the distal hypotube <NUM> includes a compressible portion <NUM>, the distal tube <NUM> can be referred to as a compressed distal tube.

A proximal end <NUM> of the proximal tube <NUM> can extend proximally within a delivery member (e.g., catheter <NUM>). A distal end <NUM> of the proximal tube <NUM> can be connected to a proximal end <NUM> of the support coil <NUM>. A distal end <NUM> of the support coil <NUM> can be connected to the distal tube <NUM> at one end, and the implant <NUM> can be connected to the distal tube <NUM> at the distal end <NUM> of the distal tube <NUM>. The proximal tube <NUM> can include a proximal lumen <NUM>, the coiled section <NUM> and support coil <NUM> can include a coil lumen <NUM>, and the distal tube <NUM> can include a distal lumen <NUM>. The proximal lumen <NUM>, coil lumen <NUM>, and distal lumen <NUM> provide a contiguous lumen through which the pull wire <NUM> and loop wire <NUM> pass.

The coiled section <NUM> can be formed primarily of a non-radiopaque material, such as steel, and can include a radiopaque section <NUM> made of a radiopaque material, such as platinum and/or tungsten. The radiopaque section <NUM> can be positioned between a proximal, non-radiopaque section of the support coil <NUM> and a distal, non-radiopaque section of the support coil <NUM>. The radiopaque section <NUM> can be positioned a predetermined distance from a distal end <NUM> of the detachment system <NUM> so that a physician can readily visualize the placement of the distal portion of the system during a treatment procedure. The proximal section, radiopaque section <NUM>, and distal section of the support coil <NUM> can be concentrically welded.

The sleeve <NUM> can cover at least a portion of the flexible section <NUM> to inhibit deformation of the flexible section and/or reduce friction with vasculature and the flexible section <NUM> during intravascular navigation. In some examples, the sleeve <NUM> can cover about <NUM> of the proximal tube <NUM> approximate and/or including the distal end <NUM> of the proximal tube <NUM>. When the detachment system <NUM> is assembled, the coiled section <NUM> and sleeve <NUM> can be more flexible than the distal hypotube <NUM> and the proximal hypotube <NUM>. One way to measure flexibility is to perform a three-point bend test wherein a portion of the detachment system <NUM> is held fixed at two end points, a force is applied perpendicularly to the detachment system <NUM> centrally between the points, and flexibility is quantified by the length of deflection of the detachment system <NUM> caused by the force. When measured this way, in some examples, the coiled section <NUM> and sleeve <NUM> can be about <NUM> times more flexible than the distal hypotube <NUM> and about <NUM> times more flexible than the proximal hypotube <NUM>. In other words, when the three-point test is performed identically on the three sections <NUM>, <NUM>, <NUM>, the coiled section <NUM> can deflect over a length that is about <NUM> time the deflection length of the distal hypotube <NUM> and about <NUM> times the length of deflection of the proximal hypotube <NUM>. Flexibility can be measured in other ways as would be appreciated and understood by a person of ordinary skill in the art. When the detachment system <NUM> is assembled, the coiled section <NUM> and sleeve <NUM> can be more flexible than the distal hypotube and the proximal hypotube as flexibility is determined by other means as would be known to a person of ordinary skill in the art.

The loop wire <NUM> can be attached to the detachment system <NUM> at locations along the tubular body <NUM>. The loop wire <NUM> can include a first end attachment <NUM> to connect the loop wire <NUM> to the wall of the lumen <NUM>, <NUM>, <NUM> and a second end attachment <NUM> to connect an opposite end of the loop wire <NUM> to the wall of the lumen <NUM>, <NUM>, <NUM>. The first end attachment <NUM> and second end attachment <NUM> can be welds, adhesives, or other mechanical fasteners that connect the loop wire <NUM> to the tubular body <NUM>. The first end attachment <NUM> and second end attachment <NUM> can be located along the proximal hypotube <NUM>, as shown in <FIG>, or any other location of the tubular body <NUM>, including along the coiled section <NUM> or the proximal hypotube <NUM>.

The loop wire <NUM> can include a twist <NUM> to provide additional resistance/friction between the loop wire <NUM> the pull wire <NUM>, as described above and shown in <FIG> provides a detailed view of a detachment system <NUM> showing the twist <NUM> in the loop wire <NUM> proximate a detachment feature (i.e., key <NUM>), according to the present invention. In prior system, the loop wire <NUM> is at one side of the pull wire <NUM> proximal to the key <NUM>. After passing a proximal end of the key <NUM>, the loop wire <NUM> loops around the key <NUM> and around the pull wire <NUM> to the other side of the loop wire <NUM>, thereby securing the key <NUM> to the pull wire <NUM>. The key <NUM> (and implant <NUM>) can be deployed from the detachment system <NUM> by translating the pull wire <NUM> proximally, beyond the loop in the loop wire <NUM>. In <FIG>, the first end attachment <NUM> and second end attachment <NUM> are located proximal on the device along tubular body <NUM>. <FIG> provides an example of a loop wire <NUM> that is anchored/attached to the tubular body <NUM> along the distal tube <NUM>. For example, the first end attachment <NUM> and second end attachment <NUM> are positioned along the distal tube <NUM>, which is in accordance with some embodiments.

As described above, one common concern with prior systems is inadvertent proximal translation of the pull wire as the system is deliver through the tortuosity. By twisting the loop wire <NUM> around the pull wire <NUM> one or more times, additional resistance prevents inadvertent proximal translation of the pull wire. Additional details and variations of the twist <NUM> are provided in the discussion of <FIG>. The distal tube <NUM> can be compressed or a portion of the distal tube <NUM> can be compressed such that, once the pull wire <NUM> is removed from the loop at the end of the loop wire <NUM>, the compressed portion of the distal tube <NUM> can expand to deliver the implant <NUM>. <FIG> provide a detailed view of a compressible portion <NUM> of the distal hypotube <NUM>.

<FIG> are illustrations of detachment features (i.e., keys <NUM>) each having a stretch resistant fiber <NUM> therethrough, according to aspects of the present disclosure. <FIG> illustrates a dual opening key 18a having a proximal portion <NUM> that is sized to engage a mechanical detachment system <NUM> and/or delivery tube (e.g., the distal hypotube <NUM>). The proximal portion <NUM> is illustrated as having a width W1. The dual opening key 18a can have a distal portion <NUM> that is sized to fit within a lumen <NUM> of the embolic coil (e.g., implant <NUM>). The distal portion <NUM> can have a wider section having a width W2 that is about as wide as the inner diameter of the implant <NUM> and a tapered section having a width W3 that is narrower than the inner diameter of the implant <NUM>. The dual opening key 18a can have a proximal tab <NUM> that is narrower than the proximal portion <NUM> and is sized to fit within a lumen of a delivery tube (e.g., distal lumen <NUM>). The "dual opening" of the dual opening key 18a can refer to the two separate openings within the face of the key 18a, for example a proximal opening <NUM> and a distal opening <NUM>. A bridge <NUM> can separate the proximal opening <NUM> and the distal opening <NUM>, as illustrated. The bridge <NUM> can be used to support the distal end <NUM> of the pull wire <NUM> when the detachment system <NUM> is in the loaded/pre-deployed state.

<FIG> illustrates a single opening key 18b having a proximal portion <NUM> that is sized to engage a mechanical detachment system <NUM> and/or delivery tube (e.g., the distal hypotube <NUM>). The proximal portion <NUM> is illustrated having a width W1. The single opening key 18b can have a distal portion <NUM> narrower than the proximal portion <NUM> and sized to fit within the lumen <NUM> of the implant <NUM>. The single opening key 18b can have a proximal tab <NUM> that is narrower than the proximal portion <NUM> and sized to fit within a lumen of a delivery tube, as also shown for the dual opening key 18a.

When reference is made herein to a key <NUM>, it will be understood to include a dual opening key 18a or a single opening key 18b. After the key <NUM> is formed, a stretch resistant fiber <NUM> can be threaded through a distal opening <NUM> of the dual opening key 18a or the single opening <NUM> of the single opening key 18b. The stretch resistant fiber, which can be a suture material and the like, can secure the key to the embolic coil portion of the implant. The key <NUM> can include engagement surfaces <NUM> at a distal end of the proximal portion <NUM> of the key <NUM>. This engagement surfaces <NUM> can abut a proximal end <NUM> of the implant <NUM>.

<FIG> are illustrations of keys <NUM> affixed to an embolic coil (e.g., implant <NUM>), according to aspects of the present disclosure. In particular, <FIG> are illustrations of the keys <NUM> with the distal portion <NUM> fully inserted into the lumen <NUM> of the implant <NUM> and wherein the key <NUM> is affixed to the implant <NUM> with welds <NUM> or other attachments. The welds <NUM> can be positioned at locations wherein the engagement surfaces <NUM> of the key <NUM> meets the proximal end <NUM> of the implant <NUM>. In both <FIG>, the key <NUM> is illustrated having a distal portion <NUM> that has a width over at least a portion of the length of the distal portion <NUM> that is about equal to the inner diameter of the lumen <NUM> of the implant <NUM>.

<FIG> is an illustration of embolic coils (e.g., implant <NUM>) being positioned within an aneurysm A, according to aspects of the present disclosure. The detachment system <NUM> is passed through a blood vessels BV to the aneurysm A through a catheter <NUM>. Once positioned, the implant(s) <NUM> can loop and bend within the aneurysm sac to form a thrombotic mass. The implant(s) <NUM> can loop back on themselves and/or loop next to other implants. As the aneurysm A becomes increasingly packed, overlapping portions of the implant <NUM> can press into each other.

<FIG> are illustrations of example loop wire <NUM> variations that increase friction at a pull wire <NUM>. <FIG> specifically show variations of twist <NUM> of the loop wire <NUM> at a distal end <NUM> of the pull wire <NUM>. As stated above, the loop wire <NUM> can extend through the lumen (e.g., lumen <NUM>, <NUM>, <NUM>) of the tubular member on one side of the pull wire <NUM>. After the loop wire passes the proximal end of the key <NUM> (e.g., the proximal extension <NUM>), the loop wire <NUM> can cross over the pull wire <NUM> such and a distal end <NUM> of the loop wire <NUM> forms an opening <NUM> through which the pull wire <NUM> passes.

The present detachment system <NUM> can include a twist <NUM> in the loop wire proximal to where the loop wire <NUM> crosses over the pull wire <NUM>. The twist <NUM> causes the loop wire <NUM> to pass around the pull wire at least one time before terminating at the final, distal opening <NUM> of the pull wire <NUM>. This twist <NUM> can be a singular twist, as shown in <FIG>, or the twist <NUM> can be a plurality of twists, as shown in <FIG>. The one or more twists <NUM> can increase the degree of tightness at the distal end <NUM> of the pull wire <NUM>, thereby preventing unwanted proximal translation and resultant premature deployment of the implant <NUM>. As described above, when the key is a dual opening key 18a, the distal end <NUM> of the pull wire <NUM> can be supported by the bridge <NUM> between the proximal opening <NUM> and the distal opening <NUM>. The twist <NUM>, in these examples, can be positioned proximal to the bridge <NUM>, and the opening <NUM> in the loop wire <NUM> can be positioned within the proximal opening <NUM>. When the key is a single opening key 18b, the opening <NUM> of the loop wire <NUM> can be within the singular opening <NUM>.

Referring to <FIG>, example detachment systems <NUM> can include a friction coating <NUM> on the distal end <NUM> of the loop wire <NUM> proximate the opening <NUM> in the loop wire <NUM> through which the pull wire <NUM> extends. The friction coating <NUM> can include a silicone, rubber, synthetic polymer, or other coating to increase friction at the junction between the pull wire <NUM> and the loop wire <NUM>. Alternatively, the distal end <NUM> of the loop wire <NUM> can have a roughened surface, for example by providing hatch marks and the like so as to increase the friction at the junction between the pull wire <NUM> and the loop wire <NUM>. In some examples, the distal end <NUM> of the pull wire <NUM> can also be configured to create additional friction. In certain prior system designs, a low-friction polytetrafluoroethylene (PTFE) coating may be applied to the pull wire <NUM> to decrease friction to enable easier deployment of the implant <NUM>. However, easy deployment can, in some cases, cause inadvertent deployment of the implant. It is contemplated that the distal end <NUM> of the pull wire <NUM> does not include a PTFE coating. In some examples, the distal end <NUM> of the pull wire <NUM> can include a silicone, rubber, synthetic polymer, or other coating to increase friction at the junction between the pull wire <NUM> and the loop wire <NUM>. Alternatively, the distal end <NUM> of the pull wire <NUM> can have a roughened surface, for example by providing hatch marks and the like so as to increase the friction at the junction between the pull wire <NUM> and the loop wire <NUM>.

<FIG> illustrate a sequence of steps for releasing an embolic implant <NUM> from a detachment system <NUM>, according to aspects of the present disclosure. <FIG> is an illustration of the implant <NUM> and delivery tube (e.g., distal hypotube <NUM>) configured for delivery and positioning of the implant <NUM>. <FIG> illustrate releasing the example embolic implant <NUM> from the distal hypotube <NUM>. A portion of the distal hypotube <NUM> is cut away for illustration purposes. The more proximal features of the tubular body <NUM> are not shown in the views.

<FIG> illustrates the detachment system including a pull wire <NUM> and a loop wire <NUM> locked into the key <NUM> of the implant <NUM> (the key shown in <FIG> is a dual opening key 18a, but the illustrations could equally apply to a single opening key 18b or a triple opening key 18c). The distal tube <NUM> can include a compressible portion <NUM>. The loop wire <NUM> can have an opening <NUM> at a distal end <NUM> of the loop wire <NUM>, and the opening <NUM> can be placed through an opening in the key <NUM> (e.g., proximal opening <NUM> in a dual opening key 18a, or the singular opening <NUM> in a single opening key 18b). As described above, the twist <NUM> can be twisted around the pull wire <NUM> proximal to the terminating end, i.e., the opening <NUM> through which the pull wire <NUM> extends. When the pull wire <NUM> is placed through the opening <NUM>, the implant <NUM> is now secure.

In the case of a dual opening key 18a, the key can include a bridge <NUM> positioned distally from the loop wire opening <NUM> and positioned to support a distal portion of the pull wire <NUM> that is distal of where the loop wire opening <NUM> wraps around by the pull wire <NUM>. Configured thusly, the bridge <NUM> can support the distal portion of the pull wire <NUM> such that when the loop wire <NUM> tensions against the pull wire <NUM> at the loop opening <NUM>, the bridge <NUM> can inhibit the distal portion of the pull wire <NUM> from deforming. The proximal tab <NUM> of the key <NUM> can be positioned to support a portion of the pull wire <NUM> that is proximal of where the loop wire opening <NUM> is supported by the pull wire <NUM>. The combination of the bridge <NUM> and the proximal tab <NUM> can inhibit the pull wire <NUM> from deforming due to forces applied by the loop wire <NUM>. The distal hypotube <NUM> can be detachably attached to the implant <NUM> as illustrated in <FIG> during delivery of the implant <NUM> through the vasculature and while the implant <NUM> is being positioned at a treatment site. The bridge <NUM> can reduce the likelihood that the implant <NUM> is prematurely released due to bending of the pull wire <NUM> due to forces from the loop wire <NUM>.

<FIG> illustrates the pull wire <NUM> being drawn proximally to begin the release sequence for the implant <NUM>. <FIG> illustrates the instant the pull wire <NUM> exits the opening <NUM> and is pulled free of the loop wire <NUM>. The distal end <NUM> of the loop wire <NUM> falls away and exits the key <NUM>. As can be seen, there is now nothing holding the implant <NUM> to the distal hypotube <NUM>. <FIG> illustrates the end of the release sequence. Here, the compressible portion <NUM> has expanded/returned to its original shape and "sprung" forward. An elastic force E is imparted by the distal end <NUM> of the distal hypotube <NUM> to the implant <NUM> to "push" it away to ensure a clean separation and delivery of the implant <NUM>. The compressible portion <NUM> can be a spiral cut portion of the distal hypotube <NUM>, for example a laser cut spiraled segment that can be compressed when the detachment system <NUM> is loaded.

<FIG> is a flow diagram illustrating a method <NUM> for designing, constructing, or configuring a detachment system <NUM> and implant <NUM>, according to aspects of the present disclosure. Steps <NUM> through <NUM> describe steps to create/construct one or more of detachment systems <NUM> described herein. In step <NUM>, the construction of the detachment system <NUM> can begin with providing a tubular body <NUM> comprising a lumen (e.g., lumen <NUM>, <NUM>, <NUM>) extending therethrough and a compressible distal tube (e.g., distal hypotube <NUM>). In step <NUM>, a loop wire <NUM> can be affixed to the tubular body <NUM>. For example, proximal ends of the loop wire can be attached to the tubular body at a first end attachment <NUM> and a second end attachment <NUM>.

In step <NUM>, the compressible distal tube <NUM> can be compressed into its loaded configuration. At step <NUM>, a loop wire opening <NUM> in the loop wire <NUM> can be positioned proximate a distal end <NUM> of the compressible distal tube such that the loop wire <NUM> is extended through the lumen (e.g., lumen <NUM>, <NUM>, <NUM>). In step <NUM>, the pull wire <NUM> can be extended through the lumen (e.g., lumen <NUM>, <NUM>, <NUM>).

In step <NUM>, the loop opening <NUM> can be extended through a key <NUM> of an implantable medical device <NUM>. In step <NUM>, the loop wire <NUM> can be twisted around the pull wire <NUM> at least one time, thereby creating the loop wire twist <NUM> described herein. In step <NUM>, a distal end <NUM> of the pull wire <NUM> can be extended through the twist <NUM> and loop opening <NUM> of the twisted loop wire <NUM>.

The steps for creating/constructing the detachment system <NUM> can end after step <NUM>. In some examples, steps <NUM> and <NUM> provide additional steps to inhibit inadvertent proximal translation of the pull wire <NUM> and such that the implant can be deployed. For example, in step <NUM>, not forming part of the present invention, proximal translation of the pull wire <NUM> through the loop wire <NUM> while the implantable medical device <NUM> is delivered through vasculature to a treatment site can be inhibited via frictional resistance of the twisted loop wire <NUM> around the pull wire <NUM>. In step <NUM>, not forming part of the present invention, frictional resistance of the junction between the loop wire <NUM> and pull wire <NUM> can be overcome such that the pull wire <NUM> translates proximally and releases the implantable medical device <NUM> at the treatment site.

In some examples, the key <NUM> can be designed to provide additional friction at the pull wire <NUM> so as to further inhibit premature proximal translation of the pull wire <NUM>. <FIG> provide examples of such a construct, wherein the pull wire <NUM> can be weaved around one or more bridges of the key <NUM>. <FIG> shows a "dual opening" key 18a, as shown and described above with reference to <FIG>. The key 18a can include a bridge <NUM> to separate the proximal opening <NUM> and the distal opening <NUM>, as illustrated. In some examples, the pull wire <NUM> can be weaved around the bridge <NUM> to create additional friction at the junction between the pull wire <NUM> and key 18a. For example and as shown in <FIG>, the pull wire <NUM> can pass over the proximal tab <NUM> of the key 18a at a first side of the key 18a, pass over/under the bridge <NUM> on a second side of the key 18a, weave back to the first side of the key 18a, and rest upon a distal end <NUM> of the key 18a on the first side of the key 18a. In weaving the pull wire <NUM> around the bridge <NUM>, the pull wire <NUM> can have a stronger engagement with the key 18a so as to inhibit inadvertent proximal translation of the pull wire <NUM>.

In some examples, the key <NUM> can include a plurality of bridges to enable more weaving of the pull wire <NUM> and thus provide additional friction. Referring to <FIG>, the key 18c (e.g., a triple-opening key) includes a first bridge <NUM> and a second bridge <NUM>. The first bridge <NUM> creates a first opening <NUM> between the proximal tab <NUM> and the first bridge <NUM>. The second bridge <NUM> creates a second opening <NUM> between the first bridge <NUM> and the second bridge <NUM>, as well as a third opening <NUM> between the second bridge <NUM> and the distal end <NUM> of the key 18c. In this example design, the pull wire <NUM> can weave around the first bridge <NUM> and second bridge <NUM> through the first opening <NUM>, the second opening <NUM>, and the third opening <NUM>. To illustrate, the pull wire <NUM> can pass over the proximal tab <NUM> of the key 18c at a first side of the key 18a, pass over/under the first bridge <NUM> on a second side of the key 18c, pass under/over the second bridge <NUM> on the first side of the key 18c, weave back to the second side of the key 18c, and rest upon a distal end <NUM> of the key 18c on the second side of the key 18c. It will be understood that the weaved pull wire <NUM> described with reference to <FIG> can be used along with the twisting loop wires <NUM> described herein; it will also be understood that the weaved pull wire <NUM> described with reference to <FIG> can be implemented as an alternative to the twisting loop wires <NUM> as a means to increase friction.

Claim 1:
A detachment system (<NUM>) for delivering an implantable medical device (<NUM>) to a target location of a body vessel, the system comprising:
a tubular body (<NUM>) comprising a lumen (<NUM>, <NUM>, <NUM>) extending therethrough and a compressed distal tube (<NUM>);
a loop wire (<NUM>) comprising a first end attachment (<NUM>) and a second end attachment (<NUM>) affixed to the tubular body and further comprising a loop opening (<NUM>) positioned proximate a distal end (<NUM>) of the compressed distal tube; and
a pull wire (<NUM>) extending through the lumen and through the loop opening,
characterised in that the loop wire comprises a twist (<NUM>) such that that the loop wire is twisted at least one time around the pull wire to increase friction between the loop wire and the pull wire.