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 non-ideally implanted 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 member and delivered via a delivery catheter to an aneurysm. During delivery, the embolic coil can be engaged to the delivery member's implant engagement/deployment system (referred to herein equivalently as an "engagement 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 engagement/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 engagement systems include premature release of a coil and movement of the delivery member due to push back from densely packed treatment sites.

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

<CIT> discloses a detachment system for delivering an implantable medical device to a target location of a body vessel with a generally hollow distal tube. The distal tube has a proximal end, a distal end, and a compressible portion of the distal tube itself axially movable from a compressed condition to an elongated condition, between the proximal and distal ends. Also included is a generally hollow proximal tube having a proximal end and a distal end, a coupling disposed between the proximal end of the distal tube and the distal end of the proximal tube, joining the proximal and distal tubes, and an engagement system engaging and deploying 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.

It is an object of the present invention to provide systems, devices, and methods to meet the above-stated needs. In some examples presented herein, separation of coil windings within an embolic coil is reduced or prevented with a stretch resistant fiber that is positioned within the lumen of the coil. Reducing or preventing the separation of coil windings can in some cases prevent an implanted portion of a partially implanted coil from being tangled with implanted coils and thereby make it possible to more easily reposition and/or extract some or all of the coil. In some examples presented herein, during delivery of the embolic coil the distal end of the pull wire is supported by an engagement/detachment feature (referred to herein equivalently as "engagement feature", "detachment feature", or "key") affixed to the proximal end of the embolic coil. The support provided by the key can in some cases reduce the likelihood that the embolic coil is prematurely released. In some examples presented herein, the embolic implant can have a highly flexible proximal portion. The flexibility of the embolic implant can in some cases reduce the force on the delivery member due to push back from densely packed treatment sites and thereby reduce movement of the delivery member due to the push back.

To meet some or all of the needs, an implant having an embolic coil, a stretch resistant fiber extended through the coil, and a detachment feature / key at the coil's proximal end is provided. The stretch resistant fiber can be effective to limit separation of windings of the embolic coil. The key can provide an attachment for securing the embolic coil to an engagement system of a delivery tube and for securing the stretch resistant fiber at the proximal end of the embolic coil.

An example method for treating an aneurysm can include one or more of the following steps presented in no particular order, and the method can include additional steps not included here. Some or all of an implant having an embolic coil and a stretch resistant fiber can be positioned within the aneurysm. A portion of the embolic coil can be retracted from the aneurysm. The portion can be inhibited from lengthening by the stretch resistant fiber when the portion is retraced from the aneurysm. The embolic coil can be bent, and the stretch resistant fiber can limit separation of the windings of the embolic coil at the bend.

The stretch resistant fiber can be positioned to extend within a lumen of the embolic coil. The stretch resistant fiber can under tension along a majority of the length of the stretch resistant fiber.

The implant can be secured to a delivery system with a key engaged to the stretch resistant fiber. To secure the implant to the delivery system, a loop wire of the delivery system can be positioned through the key, and a pull wire can be positioned through an opening in the loop wire. When the implant is secured to the delivery system, the pull wire can be supported by the key both in the proximal direction from the loop wire and the distal direction from the loop wire.

During delivery and/or positioning of the implant, the key can be visualized radiographically.

The key can be released from the delivery system, thereby releasing the implant from the delivery system. When the implant is released, the key can remain attached to the implant.

An example embolic implant can include an embolic coil, a detachment feature, and a stretch resistant fiber. The detachment feature can be affixed to the embolic coil at the proximal end of the embolic coil. The stretch resistant fiber can be engaged to the detachment feature, extend through the lumen of the embolic coil, and can be affixed to the embolic coil at the distal end of the embolic coil. Configured thusly, the stretch resistant fiber can be effective to limit separation of windings of the embolic coil as the embolic coil is reshaped.

The stretch resistant fiber can be a suture. The stretch resistant fiber can be inelastic.

The detachment feature can be radiopaque.

The detachment feature can have an opening through which the stretch resistant fiber passes. The opening can extend proximally from a proximal end of the embolic coil.

The detachment feature can have a singular opening that is sized to receive a loop wire of a mechanical delivery system and through which the stretch resistant fiber passes.

According to the invention, the detachment feature has two separate openings: a first opening through which the stretch resistant fiber passes and a second opening sized to receive a loop wire of a mechanical delivery system. The first opening is at least partially positioned within the lumen of the embolic coil. The second opening is at least partially positioned in the proximal direction from the proximal end of the embolic coil.

An example system can include the example embolic implant having the detachment feature with two separate openings and a mechanical delivery system including a loop wire and a pull wire. The stretch resistant fiber can pass through one of the two openings, and the loop wire can pass through the other of the two openings. The pull wire can be positioned through an opening in the loop wire, thereby securing the implant to the mechanical delivery system with the loop wire. The detachment feature can further include a bridge positioned between the two openings of the detachment feature, and the bridge can support a portion of the pull wire that is in the distal direction from the loop opening in the loop wire.

The detachment feature can have a proximal portion disposed proximally from the lumen of the embolic coil and a distal portion disposed within the lumen. The proximal portion can have a width that measures greater than the inner diameter of the embolic coil lumen, and the distal portion can have a width that measures about equal to the inner diameter of the embolic coil lumen.

A method for constructing or designing an embolic implant according to the invention comprises the following steps. A detachment feature is cut from a flat sheet material. Two openings are cut in the detachment feature. A stretch resistant fiber is threaded through an first opening in the detachment feature. The stretch resistant fiber is extended through a lumen of an embolic coil. The detachment feature is affixed at one end of the embolic coil. The stretch resistant fiber is affixed at the other end of the embolic coil. Tension is provided along the stretch resistant fiber between the detachment feature and the second end of the embolic coil.

A portion of a mechanical deployment system can be extended through an opening in the detachment feature to engage the detachment feature to a delivery tube. The mechanical deployment system can be extended through the same opening through which the stretch resistant fiber is threaded or an opening in the detachment feature that is separate from the opening through which the stretch resistant fiber is threaded.

The detachment feature can be cut from a radiopaque flat sheet material.

A distal portion of the detachment feature can be inserted within the lumen of the embolic coil and a proximal portion of the detachment feature can be extended proximally from the proximal end of the embolic coil. The embolic coil and the detachment feature can be selected such that the proximal portion of the detachment feature is wider than the inner diameter of the embolic coil's lumen and the distal portion of the detachment feature is about equal to the inner diameter of the embolic coil's lumen.

To affix the detachment feature to the embolic coil, the detachment feature can be welded to the embolic coil.

The above and further aspects of this invention 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 invention. The figures depict one or more implementations of the inventive devices, by way of example only, not by way of limitation.

An object of the present invention is to attain more precise and repeatable implant detachment. More specifically, it is an object of the present invention to facilitate implantation of embolic coils and other implants facing challenges such as partially implanted implants becoming difficult to reposition, delivery systems shifting position due to push back during implantation, and/or implants releasing prematurely. To meet some or all of these needs, example implants can include a stretch resistant fiber to limit stretching and other deformation of the embolic portion (e.g. embolic coil) of the implant and a detachment feature to which the stretch resistant fiber can be secured and to which a delivery system can detachably attach.

To facilitate repositioning of the implant, the stretch resistant fiber can extend through the embolic coil and limit separation of windings of the coil when the coil is bent and pulled. By limiting the separation of the windings, the embolic coil is less likely to become tangled when partially implanted and less likely to be stretched or otherwise deformed when retracted when partially implanted. The embolic coil can thereby be more easily repositioned. In some examples, the detachment feature can include two separate openings, one for securing the stretch resistant fiber, and another for being engaged to an engagement system. The dual opening detachment feature can reduce potential manufacturing challenges to provide for reliable stretch resistant fiber positioning and therefore more reliably provide implants that can be more easily repositioned.

To reduce effects of push back during implantation, the detachment feature can be sized and affixed to the embolic coil to provide an embolic coil implant with a highly flexible proximal section. An embolic coil implant having a highly flexible proximal section can reduce push back force on the delivery tube and thereby mitigate the effects of the delivery tube shifting. Additionally, or alternatively, the detachment feature can be sized to mate with a delivery tube having a highly flexible distal section, and the highly flexible distal section of the delivery tube can mitigate the effects of the delivery tube shifting. When an embolic coil implant having a highly flexible proximal section is mated to a delivery tube having a highly flexible distal portion, the combination of the flexible distal section of the delivery tube and the flexible proximal section of the implant can further mitigate the effects of delivery tube shifting.

To reduce instances of premature deployment, the detachment feature can include a bridge to support a pull wire. The detachment feature can be detachably attached to a mechanical engagement/deployment system on a delivery tube. The detachment feature can include an opening through which a loop wire of a mechanical engagement system can pass. In some examples, the detachment feature can further include a bridge positioned distally from the opening on which a distal portion of the pull wire can rest. The bridge can inhibit the pull wire from deforming due to the engagement with the loop wire and can therefore reduce the likelihood that the implant is prematurely released due to bending of the pull wire.

<FIG> is an illustration of an implant 10a including an embolic coil <NUM> with a lumen <NUM> therethrough, a detachment feature 18a, and a stretch resistant fiber <NUM>. Portions of the coil <NUM> and welds <NUM> as illustrated in a cut-away view for the purposes of illustration. The detachment feature 18a can partially be positioned within the lumen <NUM> of the coil <NUM> and can extend out of the coil <NUM>. The detachment feature 18a can include a distal opening 24a through which the stretch resistant wire <NUM> is looped, and a proximal opening 22a sized to receive a loop wire or other engagement mechanism of a mechanical implant engagement system. The detachment feature 18a can include a bridge 28a positioned between the distal opening 24a and the proximal opening 22a. The detachment feature 18a can include a proximal tab <NUM> sized to fit within a lumen of a delivery tube. The stretch resistant fiber <NUM> can be secured at an end of the embolic coil <NUM> opposite the end to which the detachment feature 18a is attached with a weld <NUM> or other appropriate attachment.

The detachment feature 18a can be tapered as it extends further within the lumen <NUM> of the embolic coil <NUM> to allow the embolic coil <NUM> to have additional flexibility where the embolic coil <NUM> surrounds the tapered region. According to the invention, the detachment feature 18a has a substantially flat profile, providing even greater flexibility in directions into and out of the plane of the image.

The detachment feature 18a can be sufficiently secured with attachments <NUM> to the coil <NUM> without fusing any windings of the coil <NUM> (as illustrated) or by fusing a small number of windings (e.g. <NUM> or fewer windings). Compared to known solutions wherein typically ten or more windings are soldered together (with limited control over the number of fused windings), the attachments <NUM> to the coil <NUM> can be realized with significantly fewer fused coil windings. By reducing the number of windings that are fused, the proximal section of the implant 10a can have increased flexibility compared to known designs which rely on fusing windings from the proximal end of the embolic coil.

<FIG> is an illustration of an alternatively constructed implant 10b having elements as described in relation to <FIG> with like reference numbers indicating like elements. Portions of the coil <NUM> and welds <NUM> as illustrated in a cut-away view for the purposes of illustration. Compared to the implant 10a illustrated in <FIG>, the implant 10b can have an alternative detachment feature 18b having a single opening 26b that provides an opening to which a mechanical engagement system can engage and through which the stretch resistant fiber <NUM> can be looped. The detachment feature 18b illustrated in <FIG> also lacks the extended tapered region of the detachment feature 18a illustrated in <FIG>. Although the tapered region of the detachment feature 18a illustrated in <FIG> can provide for a more flexible proximal section of the implant 10a compared to the implant 10b in <FIG>, the detachment feature 18b illustrated in <FIG> can nevertheless provide greater flexibility over known embolic coil implants by providing flexibility in directions into and out of the plane of the image by virtue of being flat and provide increased flexibility over designs which rely on fusing windings from the proximal end of the embolic coil by virtue of the low profile attachments <NUM>.

<FIG> through <FIG> illustrate a sequence of steps for constructing the implants 10a and 10b illustrated in <FIG> illustrate the stretch resistant fiber <NUM> being passed through the detachment features 18a, 18b. The detachment features 18a, 18b can be laser cut from a flat sheet material. The flat sheet material is preferably a radiopaque material that can be welded or otherwise affixed to the embolic coil <NUM>.

<FIG> illustrates the dual opening detachment feature 18a having a proximal portion <NUM> that is sized to engage a mechanical engagement system and/or delivery tube. The proximal portion <NUM> is illustrated as having a width W1. The dual opening detachment feature 18a can have a distal portion <NUM> that is sized to fit within the lumen <NUM> of the embolic coil. The distal portion <NUM> can have a wider section having a width W2 that is about as wide as the inner diameter of the embolic coil <NUM> and a tapered section having a width W3 that is significantly narrower than the inner diameter of the embolic coil <NUM>. The detachment feature 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.

<FIG> illustrates a single opening detachment feature 18b having a proximal portion <NUM> that is sized to engage a mechanical engagement system and/or delivery tube. The proximal portion <NUM> is illustrated having a width W1. The single opening detachment feature 18b can have a distal portion 34b narrower than the proximal portion <NUM> and sized to fit within the lumen <NUM> of the coil <NUM>. The single opening detachment feature 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.

After the detachment feature 18a, 18b is formed, the stretch resistant fiber <NUM> can be threaded through the distal opening 24a of the dual opening detachment feature 18a or the single opening 26b of the single opening detachment feature 18b.

<FIG> is an illustration of the free ends of the stretch resistant fiber <NUM> being inserted into the proximal end <NUM> of the embolic coil <NUM>. At the step illustrated in <FIG>, the stretch resistant fiber <NUM> can be looped through a detachment feature 10a, 10b such as illustrated in <FIG>.

<FIG> is an illustration of the free ends of the stretch resistant fiber <NUM> exiting the lumen <NUM> of an embolic coil <NUM> at the distal end <NUM> of the embolic coil <NUM>.

<FIG> are illustrations of detachment features 18a, 18b being inserted into the lumen <NUM> of an embolic coil <NUM>. After exiting the distal end <NUM> of the embolic coil <NUM>, the free ends of the stretch resistant fiber <NUM> can be further pulled as indicated by the arrow in <FIG> to move the detachment feature 18a, 18b into the lumen <NUM> of the embolic coil <NUM> at the proximal end <NUM> of the embolic coil <NUM> as illustrated in <FIG> and as indicated by the arrows. Before entry of the detachment feature 18a, 18b into the lumen <NUM> of the embolic coil <NUM>, the embolic coil can have an inner diameter D as indicated in <FIG>. The proximal portion <NUM> of the detachment feature 18a, 18b can be sized to have a width over at least a portion of the distal portion <NUM> that is about equal to the inner diameter D for a snug fit. Alternatively, or additionally, at least a portion of the distal portion <NUM> can have a width that is larger than the diameter D to create an interference fit. Alternatively, or additionally, at least a portion of the distal portion <NUM> can have a width that is smaller than the diameter D to allow for greater flexibility of the coil <NUM> near the proximal end <NUM> of the coil <NUM>.

<FIG> are illustrations of the detachment features 10a, 10b with the distal portion <NUM> fully inserted into the lumen <NUM> of the embolic coil <NUM> and the detachment feature 18a, 18b affixed to the embolic coil <NUM> with welds <NUM> or other attachment. In both <FIG>, the detachment feature 18a, 18b 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 D of the lumen <NUM> of the embolic coil <NUM>.

<FIG> is an illustration of the stretch resistant fiber <NUM> affixed to the distal end of the embolic coil <NUM>. After affixing the detachment feature 18a, 18b, or at least positioning the detachment feature 18a to 18b as illustrated in <FIG>, the stretch resistant fiber <NUM> can be pulled tight to reduce slack in the fiber <NUM> and/or create tension in the fiber <NUM>, and the fiber <NUM> can be affixed with a weld <NUM> or other attachment. After the fiber <NUM> is attached, the fiber can be substantially stretch resistant as to resist significant elongation due to forces applied to the embolic coil <NUM> during preparation for treatment, during delivery of the implant 10a, 10b, during positioning of the implant in a treatment site, during retraction of the implant, and during deployment of the implant. In other words, the stretch resistant fiber <NUM> can be effective to limit lengthening of the embolic coil <NUM> when the embolic coil <NUM> is retracted from an aneurysm, and the stretch resistant fiber <NUM> can be effective to limit separation of the windings within the embolic coil <NUM> when the embolic coil <NUM> is bent.

<FIG> illustrate a time sequence wherein the embolic coil <NUM> is allowed to stretch as a result of a non-optimal stretch resistant fiber <NUM> placement. <FIG> illustrates a non-optimal fiber <NUM> placement within the single opening detachment feature 18b. The fiber <NUM> can become looped over a section of the detachment feature 18b that is not optimal such that movement of the fiber <NUM> as illustrated in <FIG> can cause the fiber <NUM> to disengage from the non-optimal position, and as illustrated in <FIG>, can allow the embolic coil <NUM> to stretch at least until the fiber <NUM> again becomes engaged to the detachment feature 18a. A manufacturing challenge is therefore to prevent the fiber <NUM> from being positioned at a non-optimal location such as illustrated in <FIG> when the attachment step illustrated in <FIG> is performed. If, after manufacturing is complete, the fiber <NUM> becomes dislodged from the non-optimal location as illustrated in <FIG>, when the implant 10b is manipulated, such as while being repositioned during a treatment, the embolic coil <NUM> can elongate as illustrated in <FIG> or otherwise deform.

An advantage of the dual opening detachment feature 18a is that the stretch resistant fiber <NUM> is less likely to become looped over a non-optimal section of the detachment feature 18a during manufacturing of the implant 10a illustrated in <FIG>.

<FIG> is an illustration of embolic implant(s) <NUM> being delivered through a delivery catheter <NUM> and positioned within an aneurysm A on a blood vessel BV. The implant(s) can loop and bend within the aneurysm sac to form a thrombotic mass. The implant(s) 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> is an illustration of embolic coils <NUM> that lack a stretch resistant fiber <NUM> becoming tangled as overlapping portions of the coils press into each other. This entanglement can make it difficult or impossible for either of the coils <NUM> to be repositioned, which is a known problem with some current embolic coil implants. <FIG> illustrates a portion of the embolic coil <NUM> becoming elongated to a length L2 that is longer than the length L1 of that section illustrated in <FIG> due to a force F. <FIG> illustrates a scenario wherein a physician may try to attempt to retract a tangled partially implanted embolic coil and may be not only unable to retract the coil but also exacerbate the already challenging treatment by now having to position the deformed elongated coil. Entanglement can become more likely when the windings of the embolic coil are separated, for example due to bending, or when the coils are more tightly pressed together due to dense packing.

<FIG> is an illustration of example embolic coils <NUM> each having a stretch resistant fiber <NUM> being prevented from tangling and from elongating according to an aspect of the present invention. Each coil <NUM> is illustrated as having a bent portion <NUM>. The stretch resistant fiber <NUM> can shift within the lumen <NUM> of each coil to allow the coil <NUM> to flex and bend as needed when implanted. The fiber <NUM> can have sufficient tension to limit the amount of separation between windings in the bent portions <NUM>. The separation of the winds can be so limited as to inhibit the windings of two adjacent coils <NUM> from becoming entangled as illustrated in <FIG>. <FIG> also illustrates the force F applied to a portion <NUM> of the coil <NUM> and the portion <NUM> being inhibited from elongating due to tension in the stretch resistant fiber <NUM>. <FIG> illustrates a scenario wherein a physician may successfully retract a partially implanted embolic coil <NUM> having a stretch resistant fiber <NUM> therethrough.

<FIG> is a flow diagram illustrating a method <NUM> including steps that can be conducted as part of an aneurysm treatment using an example implant <NUM>, 10a, 10b such as described herein. In step <NUM>, an implant having an embolic coil and stretch resistant fiber can be positioned at least partially within an aneurysm sac. In step <NUM>, a portion of the embolic coil can be bent. In step <NUM>, as the coil is bent, the stretch resistant fiber can inhibit separation of windings within the bent portion of the embolic coil. In step <NUM>, some or all of the implanted portion of the implant can be retracted from the aneurysm. In step <NUM>, as the implant is retracted, the stretch resistant fiber can inhibit lengthening of the embolic coil.

<FIG> is an illustration of an example embolic implant <NUM> such as either implant 10a, 10b illustrated in <FIG> or otherwise described herein secured to a delivery tube <NUM>. Example delivery tubes and engagement/deployment systems are described in <CIT> and <CIT>. The delivery tube <NUM> can include a notch <NUM> sized to receive the proximal portion <NUM> of the detachment feature <NUM> of the implant <NUM>, and likewise the proximal portion <NUM> of the detachment feature <NUM> can be sized to fit within the notch <NUM> of the delivery tube <NUM>. <FIG> illustrates a side view of the implant <NUM> highlighting the flat profile of the detachment feature <NUM>. As described in relation to <FIG>, the implant <NUM> can have a highly flexible proximal section by virtue of the detachment feature <NUM> being flat and/or by virtue of the detachment feature <NUM> being secured to the coil <NUM> without fusing several coil windings. The detachment feature <NUM> can also be tapered for increased flexibility in directions into and out of the plane of the image. The detachment feature <NUM> can further include a proximal tab <NUM> positioned within the lumen of the delivery tube <NUM>.

During an aneurysm occlusion treatment, lack of flexibility of the proximal section of known embolic implants and/or lack of flexibility of a distal portion of a delivery tube can cause the delivery tube to pull back from the treatment site or otherwise move out of position while the implant is being placed in the aneurysm. A delivery tube having a more flexible distal portion and an implant having a more flexible proximal section, alone or in combination, can therefore provide a more stable system for delivering the implant. Flexible structures, however can tend deform or expand when manipulated. The stretch resistant fiber <NUM> and/or detachment feature <NUM> alone or in combination can support the coil <NUM> and inhibit deformation and expansion of the coil <NUM> according to the principles described herein. An object of the present invention is to provide an implant <NUM> having a highly flexible proximal section and/or configured to mate with a delivery tube <NUM> having a highly flexible distal portion.

<FIG> is an illustration of the implant <NUM> and delivery tube <NUM> configured for delivery and positioning of the implant <NUM>. <FIG> are illustrations of a sequence of steps for releasing the example embolic implant <NUM> from the delivery tube <NUM>. A portion of the delivery tube <NUM> is cut away for illustration purposes.

<FIG> illustrates the engagement system including a pull wire <NUM> and a loop wire <NUM> locked into the detachment feature <NUM> of the implant <NUM>. The delivery tube <NUM> can include a compressible portion <NUM> that can be compressed. 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 22a in the detachment feature <NUM>. When the pull wire <NUM> is put through the opening <NUM> the implant <NUM> is now secure.

The detachment feature <NUM> 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> is supported 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> tugs on 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> can 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 delivery tube <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>.

The bridge <NUM> can separate a proximal opening 22a and a distal opening 24a in a dual opening implant as illustrated. It is also contemplated that a single opening implant can be adapted to include a structure that can function to support the distal portion of the pull wire <NUM> similar to as described in relation to the illustrated bridge <NUM>. Alternative bridge structures are therefore intended to be within the scope of the present invention.

<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 locking portion <NUM>. As can be seen, there is now nothing holding the implant <NUM> to the delivery tube <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 delivery tube <NUM> to the medical device <NUM> to "push" it away to ensure a clean separation and delivery of the medical device <NUM>.

<FIG> is a cross sectional illustration of a proximal section of an alternatively constructed implant 10c having elements as described in relation to <FIG> with like reference numbers indicating like elements. Compared to the implant 10a illustrated in <FIG>, the implant 10c illustrated in <FIG> can have an alternative detachment feature 18c. The detachment feature 18c illustrated in FIG. 18c can have a portion with a width D2 sized to fit within a lumen <NUM> of an embolic coil <NUM> having an inner diameter D1. The width D2 of the detachment feature 18c can be larger than the inner diameter D1 of the coil lumen <NUM> so that when the detachment feature 18c is positioned within the lumen <NUM>, a proximal portion of the lumen <NUM> expands to a diameter D2 to accommodate the width D2 of the detachment feature 18c. Configured thusly, the expanded portion of the coil <NUM> can provide a compressive force against the section of the detachment feature having width D2 to help secure the detachment feature 18c to the coil <NUM>.

Compared to the implant 10a illustrated in <FIG>, the bridge 28c can extend proximally from a proximal end of the embolic coil <NUM>. Configured thusly, in some configurations, the pull wire <NUM> need not be inserted into the lumen <NUM> of the embolic coil <NUM> to be supported by the bridge 28c. Limiting the length of pull wire <NUM> that is inserted into the embolic coil <NUM> can increase the flexibility of the proximal section of the embolic coil.

The implant 10c illustrated in <FIG> can be constructed according to the principles illustrated in <FIG> through <FIG>. The implant 10c illustrated in <FIG> can be used according to the principles illustrated in <FIG> and <FIG>.

Claim 1:
An embolic implant (10a) comprising:
an embolic coil (<NUM>) comprising a lumen (<NUM>) therethrough, a proximal end, and a distal end;
a detachment feature (18a) affixed to the embolic coil approximate the proximal end of the embolic coil; and
a stretch resistant fiber (<NUM>) engaged to the detachment feature, extended through the lumen of the embolic coil, and affixed to the embolic coil approximate the distal end of the embolic coil,
wherein the stretch resistant fiber is effective to limit separation of windings of the embolic coil as the embolic coil is reshaped,
wherein the detachment feature has a flat profile;
characterized in that the detachment feature comprises a first opening (24a) therethrough and a second opening (22a) therethrough separated from the first opening,
wherein the stretch resistant fiber passes through the first opening,
wherein at least a portion of the first opening is positioned within the lumen of the embolic coil, and
wherein at least a portion of the second opening is positioned proximally from the proximal end of the embolic coil.