Patent Description:
Walls of the vasculature, particularly arterial walls, may develop areas of pathological dilatation called aneurysms that often have thin, weak walls that are prone to rupturing. Aneurysms are generally caused by weakening of the vessel wall due to disease, injury, or a congenital abnormality. Aneurysms occur in different parts of the body, and the most common are abdominal aortic aneurysms and cerebral (e.g., brain) aneurysms in the neurovasculature. When the weakened wall of an aneurysm ruptures, it can result in death, especially if it is a cerebral aneurysm that ruptures.

Aneurysms are generally treated by excluding or at least partially isolating the weakened part of the vessel from the arterial circulation. For example, conventional aneurysm treatments include: (i) surgical clipping, where a metal clip is secured around the base of the aneurysm; (ii) packing the aneurysm with small, flexible wire coils (micro-coils); (iii) using embolic materials to "fill" an aneurysm; (iv) using detachable balloons or coils to occlude the parent vessel that supplies the aneurysm; and (v) intravascular stenting.

Intravascular stents are well known in the medical arts for the treatment of vascular stenoses or aneurysms. Stents are prostheses that expand radially or otherwise within a vessel or lumen to support the vessel from collapsing. Methods for delivering these intravascular stents are also well known.

Conventional methods of introducing a compressed stent into a vessel and positioning it within an area of stenosis or an aneurysm include percutaneously advancing a distal portion of a guiding catheter through the vascular system of a patient until the distal portion is proximate the stenosis or aneurysm. A second, inner catheter and a guidewire within the inner catheter are advanced through the distal portion of the guiding catheter. The guidewire is then advanced out of the distal portion of the guiding catheter into the vessel until the distal portion of the guidewire carrying the compressed stent is positioned at the point of the lesion within the vessel. The compressed stent is then released and expanded so that it supports the vessel at the point of the lesion. <CIT> discloses a stent delivery system that includes an elongate core member sized for insertion into a blood vessel.

According to the invention, there is provided a stent delivery system, comprising: a core assembly sized for insertion into a corporeal lumen, the core assembly configured for advancing a stent toward a treatment location in the corporeal lumen, the core assembly comprising: a longitudinally extending tube having a lumen and a helical cut extending along the tube; and an elongate wire extending through the tube lumen, the wire having an intermediate portion disposed distal to the tube; and a stent carried by the intermediate portion, wherein the tube is affixed to the wire at proximal and distal portions of the tube.

Preferably, the wire extends proximal to a proximal end of the tube.

Preferably, a distal portion of the tube is affixed with respect to the wire.

Preferably, a restraint is coupled to the wire, and wherein the distal portion of the tube is welded to the restraint.

Preferably, the system further comprises a catheter having a lumen configured to receive the core assembly therethrough.

Preferably, the tube is sized to substantially fill the lumen of the catheter.

Preferably, the tube fills at least about <NUM>% of the lumen of the catheter.

Preferably, the proximal and distal portions of the tube are fixed, thereby preventing compression or elongation of the tube.

Preferably, the tube has a wall thickness of between about <NUM>-<NUM> microns.

Preferably, the tube has a longitudinal length of between about <NUM>-<NUM>.

Preferably, the wire has a diameter that tapers distally toward a distal end of the wire.

Preferably, a segment of the intermediate portion of the wire has a substantially constant diameter along its length.

Preferably, the wire has a constant-diameter segment that overlaps a distal end of the tube.

Preferably, the constant-diameter segment is between about <NUM>-<NUM> inches (<NUM>-<NUM>).

Preferably, the system further comprises a restraint coupled to the wire and affixed to a distal end of tube.

Preferably, the tube is configured to bend preferentially before the wire.

Preferably, the system further comprises a catheter configured to receive the core assembly therethrough, and wherein a bending stiffness of the tube is configured to match a bending stiffness of the catheter.

Preferably, the bending stiffness of the tube is less than <NUM>% of the bending stiffness of the catheter along at least a distal portion of the tube.

Preferably, the distal portion of the tube spans at least <NUM> inches (<NUM>) from a distal end of the tube.

Additional features and advantages of the present technology will be set forth in the description below, and in part will be apparent from the description, or may be learned by practice of the subject technology. The advantages of the present technology will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the present technology as claimed.

Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on illustrating clearly the principles of the present technology. For ease of reference, throughout this disclosure identical reference numbers may be used to identify identical or at least generally similar or analogous components or features.

Conventional medical device delivery systems may include a core member or core assembly configured to carry a medical device through a catheter. The core assembly can be a single continuous wire, or in some embodiments the core assembly can be a multi-member construction in which a wire segment is connected end-to-end to a tubular segment. For example, the core assembly can include a proximal wire, a tube (e.g., a hypotube) connected at its proximal end to a distal end of the proximal wire, and a distal wire connected at its proximal end to a distal end of the tube. As compared to a solid wire which must be made thinner or of smaller diameter to become more flexible, tubes provide the advantage of having a consistent and relatively larger outer diameter which occupies a greater portion of the catheter lumen, which can reduce kinking or buckling of the catheter along its length in certain use environments. Tubes can also be precisely tailored to have the desired flexibility at different portions along their length, for example, by varying the pitch of a helically extending cut at different segments of the tube, without need to vary or reduce the tube diameter.

However, tubular core assemblies are susceptible to compression and/or elongation during navigation through the catheter. This is particularly true of tubes having one or more helically extending cuts along the length of the tube. Such elongation or compression can disadvantageously alter the performance characteristics of the core assembly, such as flexibility, column strength, and navigability. Additionally, elongation and compression can cause the clinician to lose the desired responsiveness during operation of the delivery system, because movements made by the clinician at the proximal end of the core assembly do not translate in a one-to-one manner with movement of the core assembly in the distal portion of the delivery system.

For example, as the core assembly is advanced distally, one portion of the core assembly may resist movement (for example, due to frictional engagement with an inner wall of the catheter) more than another portion of the core assembly. If a distal portion of the core assembly resists distal movement to a greater degree than a proximal portion of the core assembly, then the distal portion and the proximal portion will move closer towards one another, resulting in compression or buckling of the core assembly and a reduction in its overall length. If, instead, the proximal portion of the core assembly resists proximal movement to a greater degree than the distal portion, then the proximal and distal portions will move further apart, resulting in elongation of the core assembly and an increase in its overall length. In some instances, the tubular core assembly may simultaneously be subject to both compression in some portions and elongation in other portions. Embodiments of the present technology provide a core assembly that offers the benefits of a tubular member while reducing the risk of compression or elongation. For example, the core assembly can include a longitudinally extending wire or shaft, and a tube (e.g., a hypotube having a helically extending cut) surrounding the wire along a portion of the length of the wire. The tube is affixed to the wire at proximal and distal portions of the tube, thereby restricting the ability of the tube to elongate or compress with respect to the wire.

Specific details of several embodiments of the present technology are described herein with reference to <FIG>. Although many of the embodiments are described with respect to devices, systems, and methods for delivery of stents and other medical devices, other applications and other embodiments in addition to those described herein are within the scope of the present technology. Further, embodiments of the present technology can have different configurations, components, and/or procedures than those shown or described herein. Moreover, embodiments of the present technology can have configurations, components, and/or procedures in addition to those shown or described herein and these and other embodiments may not have several of the configurations, components, and/or procedures shown or described herein without deviating from the present technology.

As used herein, the terms "distal" and "proximal" define a position or direction with respect to a clinician or a clinician's control device (e.g., a handle of a delivery catheter). For example, the terms, "distal" and "distally" refer to a position distant from or in a direction away from a clinician or a clinician's control device along the length of device. In a related example, the terms "proximal" and "proximally" refer to a position near or in a direction toward a clinician or a clinician's control device along the length of device. The headings provided herein are for convenience only and should not be construed as limiting the subject matter disclosed.

<FIG> depict embodiments of medical device delivery systems that may be used to deliver and/or deploy a medical device, such as but not limited to a stent, into a hollow anatomical structure such as a blood vessel. The stent can comprise a braided stent or other form of stent such as a woven stent, knit stent, laser-cut stent, roll-up stent, etc. The stent can optionally be configured to act as a "flow diverter" device for treatment of aneurysms, such as those found in blood vessels including arteries in the brain or within the cranium, or in other locations in the body such as peripheral arteries. The stent can optionally be similar to any of the versions or sizes of the PIPELINE™ Embolization Device marketed by Medtronic Neurovascular of Irvine, California USA. The stent can alternatively comprise any suitable tubular medical device and/or other features as described herein. In some embodiments, the stent can be any one of the stents described in <CIT>, titled VASCULAR EXPANDABLE DEVICES.

<FIG> is a side cross-sectional view of a medical device delivery system <NUM> configured in accordance with an embodiment of the present technology. The delivery system <NUM> can be configured to carry a stent (or other vascular implant or device) <NUM> thereon to be advanced through a surrounding elongate tube or catheter <NUM> to a target site in a patient, for example, a site within a corporeal lumen <NUM> such as a blood vessel. The catheter <NUM> can slidably receive a core member or core assembly <NUM> configured to carry the stent <NUM> thereon. The depicted catheter <NUM> has a proximal portion <NUM> and an opposing distal portion <NUM> which can be positioned at a treatment site within a patient, and an internal lumen <NUM> extending from the proximal portion <NUM> to the distal portion <NUM>. At the distal portion <NUM>, the catheter <NUM> has a distal opening through which the core assembly <NUM> may be advanced beyond the distal portion <NUM> to expand or deploy the stent <NUM> within the corporeal lumen <NUM>. The proximal portion <NUM> may include a catheter hub (not shown). The catheter <NUM> can define a generally longitudinal dimension extending between the proximal portion <NUM> and the distal portion <NUM>. When the delivery system <NUM> is in use, the longitudinal dimension need not be straight along some or any of its length.

The delivery system <NUM> can be used with any number of catheters. For example, the catheter can optionally comprise any of the various lengths of the MARKSMAN™ catheter available from Medtronic Neurovascular of Irvine, California USA. The catheter can optionally comprise a microcatheter having an inner diameter of about <NUM> inches (<NUM>) or less, and/or an outer diameter of <NUM> French or less near the distal portion. Instead of or in addition to these specifications, the catheter can comprise a microcatheter which is configured to percutaneously access the internal carotid artery, or another location within the neurovasculature distal of the internal carotid artery.

The core assembly <NUM> can generally comprise any member(s) with sufficient flexibility and column strength to move the stent <NUM> or other medical device through the catheter <NUM>. The core assembly <NUM> can therefore comprise a wire, tube (e.g., hypotube), braid, coil, or other suitable member(s), or a combination of wire(s), tube(s), braid(s), coil(s), etc. The embodiment of the core assembly <NUM> depicted in <FIG> is of a multi-member construction, comprising a longitudinally extending shaft or wire <NUM> and an elongate tube <NUM> surrounding at least a portion of the wire <NUM>. An outer layer <NUM>, which can comprise a layer of lubricious material such as PTFE (polytetrafluoroethylene or TEFLON™) or other lubricious polymer, can cover some or all of the tube <NUM> and/or the wire <NUM>.

The wire <NUM> has a proximal portion <NUM> and a distal portion <NUM>, which can optionally include a tip coil <NUM>. The wire <NUM> can be constructed from materials including polymers and metals including nitinol and stainless steels. In some embodiments, the wire <NUM> tapers in the distal direction, having a larger diameter at the proximal portion <NUM> and a smaller diameter at the distal portion <NUM>. The taper may be gradual and continuous along the length of the wire <NUM>, or in some embodiments the taper may vary at different portions of the wire <NUM>. As described in more detail below, in some embodiments the wire <NUM> can include one or more constant-diameter segments in which the wire <NUM> does not taper. Such constant-diameter segments can be useful for utilizing a single wire in combination with tubes <NUM> and stents <NUM> of different lengths.

The wire <NUM> can also include an intermediate portion <NUM> located between the proximal portion <NUM> and the distal portion <NUM>. The intermediate portion <NUM> includes the portion of the core assembly <NUM> onto or over which the stent <NUM> extends when the core assembly <NUM> is in the pre-deployment configuration as shown in <FIG>. The wire <NUM> may include one or more fluorosafe markers (not shown), and such marker(s) can be located on a portion of the wire <NUM> that is not covered by the outer layer <NUM> (e.g., proximal of the outer layer <NUM>). This portion of the wire <NUM> marked by the marker(s), and/or proximal of any outer layer <NUM>, can comprise a bare metal outer surface.

The tube <NUM> extends from a proximal portion <NUM> to a distal portion <NUM> and surrounds the wire <NUM> along at least a portion of the length of the wire <NUM>. In some embodiments, the distal portion <NUM> of the tube <NUM> terminates proximal to the intermediate portion <NUM> of the wire <NUM>, such that during operation, the stent <NUM> is carried by the intermediate portion <NUM> of the wire <NUM> at a position distal to the tube <NUM>.

The tube <NUM> can have a sidewall that is "uncut" or without openings or voids formed therein. Alternatively, the tube <NUM> can have openings, voids, or cuts formed in the sidewall to enhance the flexibility of the tube. This may be done by cutting a series of slots in the sidewall along part or all of the length of the tube, or cutting or drilling a pattern of other openings in the sidewall, or cutting a spiral-shaped void or helical cut in the sidewall. For example, as shown in <FIG>, the tube <NUM> has a helically extending void or cut <NUM> in the sidewall that extends from the proximal portion <NUM> to the distal portion <NUM>. The cut <NUM> can include multiple segments having different pitches, for example the first segment 115a has a lower pitch than the second segment 115b. By varying the pitch in different segments of the cut <NUM>, the bending stiffness of the tube <NUM> can be precisely tailored along the length of the tube <NUM>. Although two segments of the cut <NUM> are illustrated in <FIG>, the tube <NUM> can have a large number of different segments having different pitch dimensions.

In some embodiments, for example where the delivery system is to be used in narrow and/or tortuous vasculature, such as the neurovasculature, the tube <NUM> can be of relatively small outside diameter (e.g., <NUM>" or less, or <NUM>" or less, or <NUM>" or less, or about <NUM>", or about. In some embodiments, the outer diameter of the tube <NUM> can be configured to substantially fill the lumen of the catheter <NUM>. As used herein, "fill" means that an outer diameter of the tube <NUM> extends substantially across the internal diameter of the lumen <NUM> of the catheter <NUM>. In some embodiments, the tube <NUM> fills at least about <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or more of the lumen of the catheter.

The tube <NUM> can have a relatively thin sidewall thickness (e.g., <NUM> microns or less, <NUM> microns or less, <NUM> microns or less, or <NUM> microns or less, or between about <NUM> and <NUM> microns). The tube <NUM> can also have a relatively long overall length (e.g., <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, between about <NUM> and <NUM>, or about <NUM>). Instead of or in addition to any one or combination of such dimensions, the tube <NUM> can have a relatively long cut length (the length of the portion of the tube <NUM> in which opening(s), void(s), spiral(s), or cut(s) <NUM> is/are present) of <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, or about <NUM>.

A relatively long, small-diameter, and/or thin-walled spiral-cut tube offers certain advantages for use in the core assembly <NUM> in narrow and/or tortuous vasculature, such as the neurovasculature. The tube <NUM> can be made highly flexible (or inflexible as the case may be) where necessary by use of an appropriate spiral pitch, and the column strength or "pushability" of the tube <NUM> can be maintained largely independent of its flexibility, as the diameter of the tube <NUM> can remain constant along its length. The combination of high flexibility and pushability can facilitate easier navigation into difficult, tortuous vascular locations.

In various embodiments of the tube <NUM>, the helical or spiral cut <NUM> can be relatively long and continuous. For example, the tube <NUM> can have such a helical or spiral cut <NUM> over any of the various cut lengths specified above or elsewhere herein for the tube <NUM>. A tube <NUM> having such a helical or spiral cut <NUM> can also have any one or combination of the various outside diameters, sidewall thicknesses, and/or overall lengths specified above or elsewhere herein for the tube <NUM>. The helical or spiral cut can extend along the entire length of the tube, or nearly the entire length, e.g. the entire length except for a small uncut portion at the distal and/or proximal end, as shown in <FIG> with regard to the distal end where the spiral cut is terminated with a stress relief hole.

The long contiguous or continuous helical or spiral cut <NUM> can be implemented using any number of techniques. In one approach, two or more longitudinally adjacent spirals, cuts, slots or voids can be formed contiguously or continuously in the sidewall of the tube <NUM> and joined at their adjacent ends by connection aperture(s) to form a spiral or helical cut, slot, or void that is contiguous or continuous along the overall length or along the cut length of the tube <NUM>. In some embodiments, the individual spirals, cuts, slots, or voids can be about <NUM> in length, or <NUM> or less in length. These need not be uniform in length along the tube or cut length; for example, the first or last spiral, cut, slot, or void can be made somewhat shorter in order to achieve a cut length that is not an even multiple of the length of the individual spirals.

In some embodiments, one or more terminal apertures may be employed in the spiral or helical cut, slot, or void. In still other embodiments of the tube <NUM>, a spiral or helical cut, slot, or void is employed with terminal aperture(s) at one or both terminal ends and no connecting apertures along the cut length. One or multiple such spirals may be formed in the sidewall of a single tube <NUM>. Where employed, the terminal aperture(s) can serve as a stress relief or measure against sidewall crack formation at the end(s) of the spiral.

Instead of or in addition to a spiral cut <NUM> that is contiguous or continuous over a relatively long overall length or cut length of the tube <NUM>, the pitch of the spiral can be controlled precisely over a long overall length or cut length. For example, the pitch of the spiral cut <NUM> can vary over the cut length such that a pitch of a specific magnitude can prevail along a relatively short segment of the cut length, for example <NUM> or less, <NUM> or less, <NUM> or less, or about <NUM>. In this manner, the spiral pitch can be finely adjusted in small increments of the cut length thereby facilitating superior control over the mechanical properties of the tube <NUM> (e.g., bending stiffness, column strength) in various portions of the tube. Therefore, the tube <NUM> can have a pitch that varies in magnitude (including a specific "first pitch magnitude") along the overall length or cut length of the tube, and the first pitch magnitude can prevail along a first segment of the cut length. The first segment can have a length (measured along the longitudinal dimension of the tube <NUM>) of <NUM> or less, <NUM> or less, <NUM> or less, or about <NUM>. The magnitude of the pitch can change from the first magnitude at one or both ends of the first segment. The first segment can be located (e.g., in a contiguous or continuous void) anywhere along the cut length, including location(s) relatively far from the endpoints of the cut length, e.g., more than <NUM> away, more than <NUM> away, or more than <NUM> away from an endpoint of the cut length.

Instead of or in addition to achievement of a particular pitch magnitude in one or more short segments of the cut length (and/or a spiral that is contiguous or continuous over a relatively long overall length or cut length of the tube <NUM>), the pitch magnitude can be controlled precisely so that it can vary in relatively small increments. (The pitch can be expressed in mm/rotation. ) For example, the pitch can vary in magnitude by <NUM>/rotation or less, <NUM>/rotation or less, <NUM>/rotation or less, or <NUM>/rotation or less. This provides another manner in which the spiral can be finely controlled to facilitate desired mechanical properties in various portions of the tube <NUM>. Therefore, the tube <NUM> can have a pitch that varies in magnitude (including a specific "first pitch magnitude") along the overall length or cut length of the tube, and the first pitch magnitude can prevail along a first segment of the cut length. The magnitude of the pitch can change from the first magnitude by <NUM>/rotation or less, <NUM>/rotation or less, <NUM>/rotation or less, or <NUM>/rotation or less, at one or both ends of the first segment. The first segment can be located (e.g., in a contiguous or continuous void) anywhere along the cut length, including location(s) relatively far from the endpoints of the cut length, e.g., more than <NUM> away, or more than <NUM> away, or more than <NUM> away from an endpoint of the cut length.

As described in more detail below, the tube <NUM> can be mounted over the wire <NUM> such that the tube <NUM> is affixed to the wire <NUM>. For example, the tube <NUM> can be affixed to the wire <NUM> at one or more contact points. In one embodiment, the tube <NUM> is affixed to the wire <NUM> at one or more contact points in the proximal portion <NUM> and at one or more contact points in the distal portion <NUM> of the tube <NUM>. The tube <NUM> can be affixed to the wire <NUM> at these contact points by soldering, welding, adhesive, or other suitable fixation technique. In some embodiments, there may be two, three, four, or more contact points at which the tube <NUM> is affixed to the wire <NUM>. In other embodiments, the tube <NUM> may be affixed to the wire <NUM> at only a single contact point. In still other embodiments, the tube <NUM> may not be affixed to the wire <NUM>. As used herein, "affixed" includes both direct and indirection fixation, for example, the wire <NUM> can be directly welded or adhered to the tube <NUM> at a contact point, or the tube can be welded or otherwise attached to an intervening member (e.g., the proximal restraint <NUM>) which in turn is affixed directly to the wire <NUM>.

Affixing portions of the tube <NUM> to the wire <NUM> can reduce or eliminate elongation or compression of the tube <NUM> during operation of the delivery system <NUM>. As noted above, the relatively large diameter of the tube <NUM> can enhance pushability of the core assembly <NUM>. However, the presence of flexibility enhancing cuts (e.g., the helical cut <NUM> extending along the length of the tube) may cause the tube <NUM> to elongate or compress during movement of the core assembly <NUM> with respect to the catheter <NUM>. For example, during distal advancement of the core assembly <NUM>, the distal portion <NUM> of the tube <NUM> may resist movement (for example, due to frictional engagement with an inner wall of the catheter <NUM>) more than the proximal portion <NUM> of the tube <NUM>. As a result, the proximal portion <NUM> and the distal portion <NUM> would move closer towards one another, resulting in compression of the tube <NUM> and a reduction in overall length. If instead the distal portion <NUM> of the tube <NUM> resisted proximal movement to a greater degree than the proximal portion <NUM>, then the proximal portion <NUM> and the distal portion <NUM> would move further apart, resulting in elongation of the tube <NUM> and an increase in its overall length. Both elongation and compression can disadvantageously alter the performance characteristics of the tube <NUM>, and therefore the core assembly <NUM>. For example, elongation or compression can modify the flexibility, column strength, and navigability of the core assembly <NUM>. By affixing the tube <NUM> to the underlying wire <NUM> at one or more contact points, the risk of compression or elongation of the tube <NUM> can be reduced. In some embodiments, proximal and distal ends of the tube <NUM> can be affixed to the wire <NUM>, thereby effectively fixing the overall length of the tube <NUM> and substantially eliminating compression or elongation of the tube <NUM> during operation of the delivery system <NUM>. In other embodiments, the tube <NUM> can be affixed to the wire <NUM> at contact points that are spaced apart from proximal and distal ends of the tube <NUM>.

The system <NUM> can also include a coupling assembly <NUM> or resheathing assembly <NUM> configured to releasably retain the medical device or stent <NUM> with respect to the core assembly <NUM>. The coupling assembly <NUM> can be configured to engage the stent <NUM> via mechanical interlock with the pores and filaments of the stent <NUM>, abutment of the proximal end or edge of the stent <NUM>, frictional engagement with the inner wall of the stent <NUM>, or any combination of these modes of action. The coupling assembly <NUM> can therefore cooperate with the overlying inner surface of the catheter <NUM> to grip and/or abut the stent <NUM> such that the coupling assembly <NUM> can move the stent <NUM> along and within the catheter <NUM>, e.g., distal and/or proximal movement of the core assembly <NUM> relative to the catheter <NUM> results in a corresponding distal and/or proximal movement of the stent <NUM> within the catheter lumen <NUM>.

The coupling assembly <NUM> (or portion(s) thereof) can, in some embodiments, be configured to rotate about the core assembly <NUM>. In some such embodiments, the coupling assembly <NUM> can comprise a proximal bumper or restraint <NUM> and a distal restraint <NUM>. The proximal and distal restraints <NUM>, <NUM> can be fixed to the core assembly <NUM> to prevent or limit proximal or distal movement of the coupling assembly <NUM> along the longitudinal dimension of the core assembly <NUM>. For example, the proximal and distal restraints <NUM>, <NUM> can be soldered or fixed with adhesive to the core wire <NUM>. One or both of the proximal and distal restraints <NUM>, <NUM> can have an outside diameter or other radially outermost dimension that is smaller than the outside diameter or other radially outermost dimension of the overall coupling assembly <NUM> such that one or both of the restraints <NUM>, <NUM> do not contact the inner surface of the stent <NUM> during operation of the system <NUM>. In some embodiments, the proximal restraint <NUM> can be sized to abut the proximal end of the stent <NUM> and be employed to push the stent distally during delivery.

The coupling assembly <NUM> can also include first and second stent engagement members (or device engagement members, or resheathing members) 123a-b (together "engagement members <NUM>") and first and second spacers 125a-b (together "spacers <NUM>") disposed about the core assembly <NUM> between the proximal and distal restraints <NUM>, <NUM>. In the illustrated embodiment, from proximal to distal, the elements of the coupling assembly <NUM> include the proximal restraint <NUM>, followed by the first spacer 125a, the first stent engagement member 123a, the second spacer 125b, the second stent engagement member 123b, and finally the distal restraint <NUM>. In this configuration, the first spacer 125a defines the relative positioning of the first engagement member 123a and the proximal restraint <NUM>. The second spacer 125b defines the relative longitudinal spacing between the first engagement member 123a and the second engagement member 123b.

One or both of the spacers <NUM> can take the form of a wire coil, a solid tube, or other structural element that can be mounted over the core assembly <NUM> to longitudinally separate adjacent components of the coupling assembly <NUM>. In some embodiments, one or both of the spacers <NUM> can be a zero-pitch coil with flattened ends. In some embodiments, one or both of the spacers <NUM> can be a solid tube (e.g., a laser-cut tube) that can be rotatably mounted or non-rotatably fixed (e.g., soldered) to the core assembly <NUM>. The spacers <NUM> can have a radially outermost dimension that is smaller than a radially outermost dimension of the engagement members <NUM> such that the spacers <NUM> do not contact the stent <NUM> during normal operation of the system <NUM>. The dimensions, construction, and configuration of the spacers <NUM> can be selected to achieve improved grip between the coupling assembly <NUM> and the overlying stent <NUM>.

The stent <NUM> can be moved distally or proximally within the overlying catheter <NUM> via the proximal coupling assembly <NUM>. In some embodiments, the stent <NUM> can be resheathed via the proximal coupling assembly <NUM> after partial deployment of the stent <NUM> from a distal opening of the catheter. In embodiments in which the proximal restraint <NUM> is sized to abut the proximal end of the stent <NUM> and employed to push the stent distally during delivery, the first and second stent engagement members 123a-b can be employed to resheath the stent <NUM> after partial deployment, while taking no (or substantially no) part in pushing the stent distally during delivery. For example, the first and second stent engagement members 123a-b can in such embodiments transmit no, or substantially no, distal push force to the stent <NUM> during delivery.

Optionally, the proximal edge of the proximal coupling assembly <NUM> can be positioned just distal of the proximal edge of the stent <NUM> when in the delivery configuration. In some such embodiments, this enables the stent <NUM> to be re-sheathed when as little as a few millimeters of the stent remains in the catheter. Therefore, with stents of typical length, resheathability of <NUM>% or more can be provided (i.e. the stent can be re-sheathed when <NUM>% or more of it has been deployed).

With continued reference to <FIG>, the distal interface assembly <NUM> can comprise a distal engagement member <NUM> that can take the form of, for example, a distal device cover or distal stent cover (generically, a "distal cover"). The distal cover <NUM> can be configured to reduce friction between the stent <NUM> (e.g., a distal portion thereof) and the inner surface of the surrounding catheter <NUM>. For example, the distal cover <NUM> can be configured as a lubricious, flexible structure having a free first end or section 124a that can extend over at least a portion of the stent <NUM> and/or intermediate portion <NUM> of the core assembly <NUM>, and a fixed second end or section 124b that can be coupled (directly or indirectly) to the core assembly <NUM>.

The distal cover <NUM> can have a first or delivery position, configuration, or orientation in which the distal cover can extend proximally relative to the distal tip, or proximally from the second section 124b or its (direct or indirect) attachment to the core assembly <NUM>, and at least partially surround or cover a distal portion of the stent <NUM>. The distal cover <NUM> can be movable from the first or delivery orientation to a second or resheathing position, configuration, or orientation (not shown) in which the distal cover can be everted such that the first end 124a of the distal cover is positioned distally relative to the second end 124b of the distal cover <NUM> to enable the resheathing of the core assembly <NUM>, either with the stent <NUM> carried thereby, or without the stent <NUM>. As shown in <FIG>, the first section 124a of the distal cover <NUM> can originate from the proximal end of the second section 124b. In another embodiment, the first section 124a can originate from the distal end of the second section 124b.

The distal cover <NUM> can be manufactured using a lubricious and/or hydrophilic material such as PTFE or Teflon®, but may be made from other suitable lubricious materials or lubricious polymers. The distal cover can also comprise a radiopaque material which can be blended into the main material (e.g., PTFE) to impart radiopacity. The distal cover <NUM> can have a thickness of between about <NUM>" and about <NUM>' (one inch = <NUM>,<NUM>). In some embodiments, the distal cover can be one or more strips of PTFE having a thickness of about <NUM>".

The distal cover <NUM> (e.g., the second end 124b thereof) can be fixed to the core assembly <NUM> (e.g., to the wire <NUM> or distal tip thereof) so as to be immovable relative to the core assembly <NUM>, either in a longitudinal/sliding manner or a radial/rotational manner. Alternatively, as depicted in <FIG>, the distal cover <NUM> (e.g., the second end 124b thereof) can be coupled to (e.g., mounted on) the core assembly <NUM> so that the distal cover <NUM> can rotate about a longitudinal axis of the core assembly <NUM> (e.g., of the wire <NUM>), and/or move or slide longitudinally along the core assembly <NUM>. In such embodiments, the second end 124b can have an inner lumen that receives the core assembly <NUM> therein such that the distal cover <NUM> can slide and/or rotate relative to the core assembly <NUM>. Additionally, in such embodiments, the distal interface assembly <NUM> can further comprise a proximal restraint <NUM> that is fixed to the core assembly <NUM> and located proximal of the (second end 124b of the) distal cover <NUM>, and/or a distal restraint <NUM> that is fixed to the core assembly <NUM> and located distal of the (second end 124b of the) distal cover <NUM>. The distal interface assembly <NUM> can comprise a radial gap between the outer surface of the core assembly <NUM> (e.g., of the wire <NUM>) and the inner surface of the second end 124b. Such a radial gap can be formed when the second end 124b is constructed with an inner luminal diameter that is somewhat larger than the outer diameter of the corresponding portion of the core assembly <NUM>. When present, the radial gap allows the distal cover <NUM> and/or second end 124b to rotate about the longitudinal axis of the core assembly <NUM> between the restraints <NUM>, <NUM>.

In some embodiments, one or both of the proximal and distal restraints <NUM>, <NUM> can have an outside diameter or other radially outermost dimension that is smaller than the (e.g., pre-deployment) outside diameter or other radially outermost dimension of the distal cover <NUM>, so that one or both of the restraints <NUM>, <NUM> will tend not to bear against or contact the inner surface of the catheter during operation of the core assembly <NUM>. Alternatively, it can be preferable to make the outer diameters of the restraints <NUM> and <NUM> larger than the largest radial dimension of the pre-deployment distal cover <NUM>, and/or make the outer diameter of the proximal restraint <NUM> larger than the outer diameter of the distal restraint <NUM>. This configuration allows easy and smooth retrieval of the distal cover <NUM> and the restraints <NUM>, <NUM> back into the catheter post stent deployment.

In operation, the distal cover <NUM>, and in particular the first section 124a, can generally cover and protect a distal portion of the stent <NUM> as the stent <NUM> is moved distally through a surrounding catheter. The distal cover <NUM> may serve as a bearing or buffer layer that, for example, inhibits filament ends of the distal portion of the stent <NUM> (where the stent comprises a braided stent) from contacting an inner surface of the catheter, which could damage the stent <NUM> and/or catheter, or otherwise compromise the structural integrity of the stent <NUM>. Since the distal cover <NUM> may be made of a lubricious material, the distal cover <NUM> may exhibit a low coefficient of friction that allows the distal portion of the stent to slide axially within the catheter with relative ease. The coefficient of friction between the distal cover <NUM> and the inner surface of the catheter <NUM> can be between about <NUM> and about <NUM>. For example, in embodiments in which the distal cover and the catheter are formed from PTFE, the coefficient of friction can be about <NUM>. Such embodiments can advantageously improve the ability of the core assembly <NUM> to pass through the catheter, especially in tortuous vasculature.

Structures other than the herein-described embodiments of the distal cover <NUM> may be used in the core assembly <NUM> and/or distal interface assembly <NUM> to cover or otherwise interface with the distal portion of the stent <NUM>. For example, a protective coil or other sleeve having a longitudinally oriented, proximally open lumen may be employed. In other embodiments, the distal interface assembly <NUM> can omit the distal cover <NUM>, or the distal cover can be replaced with a component similar to the proximal coupling assembly <NUM>. Where the distal cover <NUM> is employed, it can be connected to the distal tip coil <NUM> (e.g., by being wrapped around and enclosing some or all of the winds of the coil <NUM>) or being adhered to or coupled to the outer surface of the coil by an adhesive or a surrounding shrink tube. The distal cover <NUM> can be coupled (directly or indirectly) to other portions of the core assembly <NUM>, such as the wire <NUM>.

In embodiments of the core assembly <NUM> that employ both a rotatable proximal coupling assembly <NUM> and a rotatable distal cover <NUM>, the stent <NUM> can be rotatable with respect to the core assembly <NUM> about the longitudinal axis thereof, by virtue of the rotatable connections of the proximal coupling assembly <NUM> and distal cover <NUM>. In such embodiments, the stent <NUM>, proximal coupling assembly <NUM>, and distal cover <NUM> can rotate together in this manner about the core assembly <NUM>. When the stent <NUM> can rotate about the core assembly <NUM>, the core assembly <NUM> can be advanced more easily through tortuous vessels as the tendency of the vessels to twist the stent <NUM> and/or core assembly <NUM> is negated by the rotation of the stent <NUM>, proximal coupling assembly <NUM>, and distal cover <NUM> about the core assembly <NUM>. In addition, the required push force or delivery force is reduced, as the user's input push force is not diverted into torsion of the stent <NUM> and/or core assembly <NUM>. The tendency of a twisted stent <NUM> and/or core assembly <NUM> to untwist suddenly or "whip" upon exiting tortuosity or deployment of the stent <NUM>, and the tendency of a twisted stent to resist expansion upon deployment, are also reduced or eliminated. Further, in some such embodiments of the core assembly <NUM>, the user can "steer" the core assembly <NUM> via the tip coil <NUM>, particularly if the coil <NUM> is bent at an angle in its unstressed configuration. Such a coil tip can be rotated about a longitudinal axis of the system <NUM> relative to the stent <NUM>, coupling assembly <NUM> and/or distal cover <NUM> by rotating the distal portion <NUM> of the core assembly <NUM>. Thus the user can point the coil tip <NUM> in the desired direction of travel of the core assembly <NUM>, and upon advancement of the core assembly the tip will guide the core assembly in the chosen direction.

<FIG> is a side view of the core assembly <NUM> of the medical device delivery system <NUM> shown in <FIG>, and <FIG> is a side cross-sectional view of the core assembly <NUM> of <FIG> taken along line 2B-2B. As noted above, the core assembly <NUM> includes an elongate shaft or wire <NUM> and a longitudinally extending tube <NUM> that surrounds the wire <NUM> along at least a portion of the length of the wire <NUM>. The wire <NUM> includes a proximal portion <NUM>, a distal portion <NUM>, and an intermediate portion <NUM> configured to carry the stent <NUM> (<FIG>) thereon. The tube <NUM> is disposed over the wire <NUM> such that the wire <NUM> extends through an inner lumen of the tube <NUM>. The wire <NUM> can have a length greater than a length of the tube <NUM>, such that the wire <NUM> extends proximal to the proximal portion <NUM> of the tube <NUM> and also extends distal to the distal portion <NUM> of the tube <NUM>.

As noted above, the tube <NUM> can have a spiral or helical void or cut <NUM> extending along at least a portion of the length of the tube <NUM>, and the cut <NUM> can include one or more segments 115a, 115b having different pitch dimensions to impart varying bending stiffness to different portions of the tube <NUM> along its length. The cut <NUM> can terminate in an aperture <NUM> formed in the sidewall of the tube <NUM>. The aperture <NUM> can comprise an additional void that is formed (e.g., cut) in the sidewall of the tube <NUM> and is contiguous or continuous with the void or cut <NUM>. The aperture <NUM> can comprise a circle, as shown in <FIG>, or any other suitable shape such as an ellipse or polygon. When employed, the aperture <NUM> can serve as a stress relief or measure against sidewall crack formation at the end of the helical cut <NUM>. In some embodiments, different segments of the cut <NUM> (e.g., first segment 115a and second segment 115b) can be connected by connection apertures, thereby forming a single, contiguous, or continuous void. The connection apertures can be substantially similar to the aperture <NUM>, except that they are positioned between adjacent segments of the cut <NUM> (e.g., between the first segment 115a and the second segment 115b).

The wire <NUM> can have an outer profile that tapers radially inwardly in the distal direction, having a larger outer profile (e.g., diameter) at the proximal portion <NUM> and a smaller outer profile at the distal portion <NUM>. The taper may be gradual and continuous along the length of the wire <NUM>, or in some embodiments the taper may vary at different portions of the wire <NUM>. In the embodiment illustrated in <FIG>, the wire <NUM> can include two (or more) constant-diameter segments: a first constant-diameter segment <NUM> and a second constant-diameter segment <NUM>. Over each of these segments <NUM>, <NUM>, the wire <NUM> can have a substantially uniform (i.e., non-tapered) outer profile. The first constant-diameter segment <NUM> can be positioned to underlie the proximal portion <NUM> of the tube <NUM>, and the second constant-diameter segment <NUM> can be positioned to underlie the distal portion <NUM> of the tube <NUM>. Because the wire <NUM> tapers distally from the first constant-diameter segment <NUM> to the second constant-diameter segment <NUM>, in some embodiments the outer profile (e.g., diameter) of the first constant-diameter segment <NUM> is greater than the outer profile (e.g., diameter) of the second constant-diameter segment <NUM>. In some embodiments, the first constant-diameter segment <NUM> can have a length of between about <NUM>" to <NUM>", <NUM>" to <NUM>", <NUM>" to <NUM>", or about <NUM>". In some embodiments, the second constant-diameter segment <NUM> can likewise have a length of between about <NUM>" to <NUM>", <NUM>" to <NUM>", <NUM>" to <NUM>", or about <NUM>".

These first and second constant-diameter segments <NUM> and <NUM> can provide portions of the wire <NUM> configured to be affixed to corresponding portions of the surrounding tube <NUM>. The tube <NUM> can be affixed to the wire <NUM> at a first contact point <NUM> at the proximal portion <NUM> of the tube <NUM>, and can also be affixed to the wire <NUM> at the second contact point <NUM> at the distal portion <NUM> of the tube <NUM>. The first contact point <NUM> can be positioned at any longitudinal position within the first constant-diameter segment <NUM>, and the second contact point <NUM> can be positioned at any longitudinal position within the second constant-diameter segment <NUM>. Accordingly, the first and second constant-diameter segments <NUM>, <NUM> enable the wire <NUM> to accommodate the first and second contact points <NUM>, <NUM> at a range of different longitudinal positions within the first and second constant-diameter segments, <NUM>, <NUM>, respectively. For example, in various embodiments, the first contact point <NUM> can be positioned at any longitudinal position along the length of the first constant-diameter segment <NUM>, and the second contact point <NUM> can be positioned at any longitudinal position along the length of the second constant-diameter segment <NUM>.

This feature can be useful for utilizing a single configuration of the wire <NUM> in combination with tubes <NUM> and/or stents <NUM> (<FIG>) of different lengths. For example, the intermediate portion <NUM> of the wire <NUM> may accommodate stents having a range of different stent sizes. In the case of longer stents, the proximal end of the stent may extend more proximally along the wire than with a shorter stent. To position the proximal bumper or restraint <NUM> adjacent to the proximal end of the stent, the restraint <NUM> may be placed at different longitudinal positions along the second constant-diameter segment <NUM> depending on the length and position of the stent. With a shorter stent, the restraint <NUM> (along with the distal portion <NUM> of the tube <NUM>) will be positioned more distally than with a longer stent. By moving the restraint <NUM> and the distal portion <NUM> of the tube <NUM> along the second constant-diameter segment <NUM>, the proximal portion <NUM> of the tube <NUM> is also moved along the first constant-diameter segment <NUM> by an equivalent amount. Accordingly, the lengths of the first and second constant-diameter segments <NUM>, <NUM> can provide a range of longitudinal positions over which the first and second contact points <NUM>, <NUM> can be located.

The wire <NUM> and the tube <NUM> can be configured such that, during operation of the delivery system, the tube <NUM> preferentially bends before the wire <NUM>. For example, the sidewall thickness, material section, and helical cut <NUM> of the tube <NUM> can all be varied to provide the desired bending stiffness at different portions along the length of the tube <NUM>. Likewise, the material and dimensions of the wire <NUM> can be varied along the length of the wire <NUM> to provide varied bending stiffness along its length. The relative bending stiffnesses of the wire <NUM> and the tube <NUM> can be configured such that, when bending the core assembly <NUM> (for example, during navigation of tortuous anatomy), the tube <NUM> bends before the wire <NUM>. This allows strain to be borne primarily by the tube <NUM>, which can reduce the load borne by the wire <NUM> and decrease the required delivery force.

As noted above, the tube <NUM> can be affixed to the wire <NUM> along the first constant-diameter segment <NUM> at a first contact point <NUM>. As seen best in <FIG>, the first contact point <NUM> can be at the proximalmost end of the tube <NUM>. The wire <NUM> can be affixed to the tube <NUM> at the first contact point <NUM> via welding, soldering, adhesive, or any other suitable fixation technique. The outer profile (e.g., diameter) of the wire <NUM> can be configured to facilitate fixation of the wire <NUM> to the tube <NUM> at the first contact point <NUM>. For example, in some embodiments, the outer profile of the wire <NUM> is nearly as large as the inner profile of the lumen of the tube <NUM>, such that the wire <NUM> substantially fills the lumen of the tube <NUM> at the first contact point <NUM>. This can facilitate welding, soldering, or otherwise affixing or attaching the wire <NUM> to the tube <NUM>. As the outer profile of the tube <NUM> can be substantially constant along the first constant-diameter segment <NUM>, the tube <NUM> can be affixed to the wire <NUM> at the first contact point <NUM> at any point along the length of the first constant-diameter segment <NUM>.

The tube <NUM> can be affixed to the restraint <NUM> along the second constant-diameter segment <NUM> at a second contact point <NUM>. As best seen in <FIG>, the proximal bumper or restraint <NUM> can be mounted over the wire <NUM> at a longitudinal position within the second constant-diameter segment <NUM> of the wire <NUM>. The restraint <NUM> includes an inner lumen <NUM> configured to receive the wire <NUM> therethrough. The lumen <NUM> can be sized to correspond to an outer profile (e.g., diameter) of the wire <NUM> along the second constant-diameter segment <NUM>. In some embodiments, the restraint <NUM> is welded, soldered, or otherwise fixed with respect to the wire <NUM> such that it cannot rotate or translate with respect to the wire <NUM>. In other embodiments, the restraint <NUM> can be configured to permit rotation and/or translation within a predefined range with respect to the wire <NUM>.

The restraint <NUM> further includes a distal section <NUM> having a first outer profile and a proximal section <NUM> having a second outer profile that is less than the first outer profile. The outer profile of the proximal section <NUM> can be sized and configured to fit within the lumen of the tube <NUM>, while the outer profile of the distal section <NUM> can be sized and configured to abut the distal end of the tube <NUM>. In some embodiments, the outer profile of the distal section <NUM> matches or exceeds the outer profile of the tube <NUM>, such that the distal portion <NUM> of the tube <NUM> cannot move distally beyond the distal section <NUM> of the restraint <NUM>. When the tube <NUM> is positioned over the proximal section <NUM> of the restraint <NUM> (as seen in <FIG>), the proximal section <NUM> can partially overlap the aperture <NUM> within the sidewall of the tube <NUM>. In some embodiments, the proximal section <NUM> does not overlap the aperture <NUM> by more than <NUM>%, more than <NUM>%, more than <NUM>%, more than <NUM>%, or more than <NUM>%. In some embodiments, the proximal section <NUM> does not overlap the aperture <NUM> at all.

The tube <NUM> can be affixed to the restraint <NUM> at the second contact point <NUM> via welding, soldering, adhesive, or any other suitable fixation technique. The outer profile (e.g., diameter) of the restraint <NUM> can be configured to facilitate fixation of the restraint <NUM> to the tube <NUM> at the second contact point <NUM>. For example, in some embodiments, the outer profile of the proximal section <NUM> of the restraint <NUM> is nearly as large as the inner profile of the lumen of the tube <NUM>, such that the proximal section <NUM> of the restraint <NUM> substantially fills the lumen of the tube <NUM> at the second contact point <NUM>. This can facilitate welding, soldering, or otherwise affixing or attaching the restraint <NUM> to the tube <NUM>.

In some embodiments, the tube <NUM> can be affixed directly to the wire <NUM> at the second contact point <NUM>, for example via welding, soldering, adhesive, or other fixation technique. In some embodiments, instead of the restraint <NUM>, the tube <NUM> can be connected to another intervening member which in turn is attached to the wire <NUM>. For example, an attachment member separate from the restraint <NUM> can be affixed to the wire <NUM>, and the tube <NUM> can in turn be affixed to the attachment member at the second contact point <NUM>.

In some embodiments, the wire <NUM> may include only the first constant-diameter segment <NUM> and omit the second constant-diameter segment <NUM>, while in other embodiments the wire <NUM> may include only the second constant-diameter segment <NUM> and omit the first constant-diameter segment. In still other embodiments, the wire <NUM> may omit both the first and second constant-diameter segments <NUM>, <NUM>, instead having a tapering or otherwise varying outer profile in those segments of the wire <NUM>.

Although the first and second contact points <NUM>, <NUM> are shown as being at or near proximal and distal ends of the tube <NUM>, in some embodiments one or more of the first and second contact points can be located at positions spaced apart from the proximal and distal ends of the tube <NUM>. Additionally or alternatively, in some embodiments there may be additional contact points located at other longitudinal locations along the wire. For example, an additional contact point can be provided between the first and second contact points, thereby providing another point of fixation between the tube and the wire and further preventing compression or elongation of the tube with respect to the wire.

<FIG> are graphs of bending stiffness of components of a medical device delivery system, according to some embodiments. Referring to <FIG>, line <NUM> depicts the bending stiffness of a hypotube as a function of distance from its distal end. The bending stiffness generally increases in the proximal direction, such that the distalmost portion (on the left side of the graph) has the lowest bending stiffness, and the proximalmost portion (on the right side of the graph) has the highest bending stiffness. The bending stiffness can increase in a series of step changes. Line <NUM> depicts the bending stiffness of a catheter configured to receive the hypotube therethrough. As with the hypotube, the bending stiffness of the catheter increases with distance from the distal end. However, the catheter has a smaller increase in bending stiffness across its length. Line <NUM> depicts the difference in bending stiffness at each point between the hypotube and the catheter, expressed as a percentage. High degrees of mismatch between the bending stiffness of the catheter and the hypotube can contribute to increased kinking of the catheter, especially when navigating tortuous anatomy such as the neurovasculature. As shown in <FIG>, there is a large increase in line <NUM> between <NUM> and <NUM> inches (<NUM> and <NUM>), reflecting the large difference in bending stiffness between the catheter and the hypotube over this length range. This can disadvantageously lead to kinking or other obstructions that might increase the overall delivery force required to advance the core member or hypotube through the catheter.

To ameliorate these problems, the bending stiffness of the hypotube and/or the catheter can be modified to reduce the difference between the two over at least a portion of their lengths. <FIG> illustrates bending stiffness of components of a delivery system in which the hypotube has been modified to have decreased bending stiffness in the range of <NUM> to <NUM> inches (<NUM> and <NUM>) compared to the hypotube of <FIG>. Referring to <FIG>, line <NUM> again reflects the bending stiffness of the catheter, which is unchanged relative to <FIG>. Line <NUM> depicts the bending stiffness of the hypotube, which is reduced in the range of <NUM> to <NUM> inches (<NUM> and <NUM>) relative to <FIG>. Line <NUM> depicts the percentage difference in bending stiffness between the hypotube and the catheter. As seen in <FIG>, line <NUM> remains low along the <NUM> to <NUM> inch (<NUM> and <NUM>) range, reflecting similar bending stiffnesses of the hypotube and the catheter in this range as compared to <FIG>. Accordingly, by reducing the bending stiffness of the tube in the <NUM> to <NUM> inch (<NUM> and <NUM>) range, the bending stiffness of the hypotube is more nearly matched to that of the catheter. Delivery and resheathing forces were evaluated for the designs illustrated in <FIG>, and it was found that the design of <FIG> resulted in a <NUM>% reduction in delivery force and a <NUM>% drop in resheathing force compared to the design of <FIG>. This demonstrates that delivery system performance can be improved by more closely matching the bending stiffness of the catheter to the bending stiffness of the hypotube along at least a portion of their lengths.

To more closely match the bending stiffness of the tube to the bending stiffness of the catheter, the tube can be configured to have a bending stiffness that is less than <NUM>%, less than <NUM>%, less than <NUM>%, or less than <NUM>% of the bending stiffness of the catheter along at least a distal portion of the tube. In some embodiments, the distal portion of the hypotube spans at least <NUM> inches (<NUM>), at least <NUM> inches (<NUM>), at least <NUM> inches (<NUM>), at least <NUM> inches (<NUM>), at least <NUM> inches (<NUM>), or at least <NUM> inches (<NUM>) from a distal end of the hypotube.

This disclosure is not intended to be exhaustive or to limit the present technology to the precise forms disclosed herein. Although specific embodiments are disclosed herein for illustrative purposes, various equivalent modifications are possible without deviating from the present technology, as those of ordinary skill in the relevant art will recognize. In some cases, well-known structures and functions have not been shown and/or described in detail to avoid unnecessarily obscuring the description of the embodiments of the present technology. Although steps of methods may be presented herein in a particular order, in alternative embodiments the steps may have another suitable order. Similarly, certain aspects of the present technology disclosed in the context of particular embodiments can be combined or eliminated in other embodiments. Furthermore, while advantages associated with certain embodiments may have been disclosed in the context of those embodiments, other embodiments can also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages or other advantages disclosed herein to fall within the scope of the present technology. Accordingly, this disclosure and associated technology can encompass other embodiments not expressly shown and/or described herein.

Claim 1:
A stent delivery system (<NUM>), comprising:
a core assembly (<NUM>) sized for insertion into a corporeal lumen, the core assembly (<NUM>) configured for advancing a stent (<NUM>) toward a treatment location in the corporeal lumen, the core assembly (<NUM>) comprising:
a longitudinally extending tube (<NUM>) having a lumen and a helical cut (<NUM>) extending along the tube (<NUM>); and
an elongate wire (<NUM>) extending through the tube lumen, the wire (<NUM>) having an intermediate portion disposed distal to the tube (<NUM>); and
a stent (<NUM>) carried by the intermediate portion, wherein the tube (<NUM>) is affixed to the wire (<NUM>) at proximal (<NUM>) and distal (<NUM>) portions of the tube (<NUM>).