Patent Description:
Stents and stent-grafts may be utilized to radially support a variety of tubular passages in the body, including arteries, veins, airways, gastrointestinal tracts, and biliary tracts. The preferred method of placing these devices has been to use specialized delivery systems to precisely place and deploy a device at the site to be treated. These delivery systems allow the practitioner to minimize the trauma and technical difficulties associated with device placements. Attributes of delivery systems include: low profile; ability to pass through introducer sheaths; ability to negotiate tortuous vasculature, smoothly and atraumatically; protection of constrained devices; and ability to accurately position and deploy the device.

Stents or stent-grafts may be deployed and plastically deformed by using an inflatable balloon (e.g., balloon expandable stents) or to self-expand and elastically recover (e.g., "self expandable" stents) from a collapsed or constrained delivery diameter to an expanded and deployed diameter. Some stents are designed to elastically recover by being manufactured at their functional diameter out of a material that has elastic recovery properties, and then radially compressed to be mounted on a delivery catheter.

These stent and stent-graft devices may be held, compressed, or constrained in the delivery configuration prior to and during delivery to a target location. The devices may be held in this compressed state for a prolonged period of time (e.g., after manufacture and prior to use). Different mechanisms or devices may be used to hold the stent and stent-graft devices in a delivery state and be removed to allow expansion of the stent and stent-graft devices at the target location.

<CIT> is directed to a thin tubular multiple filament (film or fiber) structure that can hold high internal pressures. When desired, an extension of the filaments can be pulled in any direction to unfurl the structure. This device is useful for self expanding stent or stent graft delivery systems, balloon dilatation catheters, removable guide wire lumens for catheters, drug infusion or suction catheters, guide wire bundling casings, removable filters, removable wire insulation, removable packaging and other applications.

The invention is directed to a method of forming a constraining mechanism for an implantable medical device according to claim <NUM> and a system for forming a constraining mechanism for an implantable medical device according to claim <NUM>.

Refinements of the inventions are described in the dependent claims.

Persons skilled in the art will readily appreciate that various aspects of the present disclosure can be realized by any number of methods and apparatus configured to perform the intended functions. It should also be noted that the accompanying drawing figures referred to herein are not necessarily drawn to scale, but may be exaggerated to illustrate various aspects of the present disclosure, and in that regard, the drawing figures should not be construed as limiting.

Various aspects of the present disclosure are directed toward apparatuses, systems, and methods that include forming or manufacturing a constraining mechanism. The constraining mechanisms are configured to hold, compress, or constrain an implantable medical device (e.g., a stent, stent-graft, balloon, or other expandable medical device) in a delivery configuration prior to and during delivery to a target location. In certain instances, the constraining mechanism includes one or more fibers.

The constraining mechanisms, in accordance with the various aspects of the present disclosure, may be formed or manufactured directly on the implantable medical device. The fiber or fibers are knit, sewn, or interlocked to form the constraining mechanisms. Thus, the fiber or fibers are knit, sewn, or interlocked together about or around the implantable medical device. As noted above, the implantable medical devices are reduced, collapsed, or constrained to a reduced (delivery) diameter by the constraining mechanism for delivery into a target location into a patient where it is deployed or expanded to a deployed diameter (larger than the reduced diameter). As a result, and in certain instances, the fiber or fibers are interlocked, knit or sewn on the implantable medical device while the device is in the reduced (delivery) diameter.

Certain prior constraining mechanisms that use fibers are knit or interlocked prior to being applied to or arranged about an implantable medical device. The prior constraining mechanisms are formed as a separate component and added as a separate step in a manufacturing process. Compared to these prior constraining mechanisms, for example, the processing steps are reduced by way of forming the fiber constraining mechanism directly on the implantable medical device. Eliminating a step in the process may decrease the opportunity for errors or failures in the loading process such as improper constraining mechanism arrangement or damage to the implantable medical device (e.g., bent stent struts, broken stent struts, fiber tangles, improper constraining mechanism length such as fiber length, improper layering of the fiber).

<FIG> is a top plan view of a catheter <NUM> with a constraining mechanism <NUM>, according to some embodiments. As shown in <FIG>, the constraining mechanism <NUM> is configured to constrain an expandable medical device <NUM> to a delivery configuration. The constraining mechanism <NUM> may include one or more fibers <NUM> arranged about the expandable medical device <NUM> to maintain the constraining mechanism <NUM> in a constrained configuration.

The constraining mechanism <NUM> is arranged along a length of the expandable medical device <NUM>. The constraining mechanism <NUM> is also circumferentially arranged about the expandable medical device <NUM> and may substantially cover the expandable medical device <NUM> for delivery. The one or more fibers <NUM> may be arranged within a lumen (not shown) of the catheter <NUM> and extend toward a proximal end of the catheter <NUM> that is arranged external to a patient during delivery of the expandable medical device <NUM>. The one or more fibers <NUM> include a proximal end <NUM> that a user may apply tension to in order to release the constraining mechanism <NUM> and deploy the expandable medical device <NUM>.

In certain instances, the one or more fibers <NUM> release similar to a rip cord such that interlocking portions (e.g., overlapping fibers or knots) sequentially release along the length of the expandable medical device <NUM>. As is explained in greater detail below, the constraining mechanism <NUM> is formed by interlocking together the one or more fibers <NUM> directly on the expandable medical device <NUM>. As compared to prior multiple fiber constraining mechanisms which are knitted together and then subsequently arranged about a constrained device, the constraining mechanism <NUM> is formed directly on the expandable medical device <NUM>. The expandable medical device <NUM> may be a stent, stent-graft, a balloon, or a similar device.

<FIG> is an example funnel <NUM> for reducing an implantable medical device <NUM> to a reduced diameter according to some embodiments. The funnel <NUM> is configured to reduce a diameter of an implantable medical device <NUM> from a deployed (or expanded) diameter to a reduced diameter. As shown in <FIG>, the funnel <NUM> includes internal surfaces <NUM> reducing an internal diameter of the funnel <NUM> and a braiding zone <NUM>. The implantable medical device <NUM> is shown with portions in an expanded diameter (between the internal surfaces <NUM> reducing an internal diameter of the funnel <NUM>) and at a reduced diameter (between internal surfaces of the braiding zone <NUM>). The braiding zone <NUM> is described as the landing point for the one or more fibers <NUM> when forming the constraining mechanism <NUM> and consists of an extension of the funnel <NUM> as shown in <FIG>.

In certain instances, the internal surfaces <NUM> of the funnel <NUM> that reduce in diameter may be tapered. In addition, the tapered internal surfaces <NUM> lead directly into the braiding zone <NUM> of the funnel <NUM>. Internal surfaces <NUM> of the braiding zone <NUM> of the funnel <NUM> may be substantially linear. The implantable medical device <NUM> may be loaded into an entry point <NUM> of the funnel <NUM>. When loaded through the entry point <NUM> of and into the funnel <NUM>, the tapered internal surfaces <NUM> forced the implantable medical device <NUM> to a constrained configuration in which the implantable medical device <NUM> has a reduced diameter. The implantable medical device <NUM> has a reduced diameter through the braiding zone <NUM> of the funnel <NUM> and is forced out an exit point <NUM> of the funnel <NUM>.

As shown in <FIG>, external surfaces <NUM> of the funnel <NUM> include a similar taper as the internal surfaces <NUM> of the funnel. The external surfaces <NUM> of the funnel <NUM> at the braiding zone <NUM>, however, also may include a taper that is less than the taper of the remaining portions of the external surfaces <NUM> of the funnel <NUM>. The external surfaces <NUM> of the funnel <NUM> taper until an inflection point <NUM>. At the inflection point <NUM>, the external surfaces <NUM> may transition from a larger taper to less of a taper or where the external surfaces <NUM> may transition from a taper to substantially linear surfaces.

In certain instances, the funnel <NUM> is configured to facilitate arrangement of one or more fibers (that form a constraining mechanism) on the implantable medical device <NUM> for interlocking of the one or more fibers as discussed below with reference to <FIG>. The inflection point <NUM> may serve as landing point for the one or more of the fibers, which may slide down the external surfaces <NUM> toward the exit point <NUM> of the funnel <NUM>. As the implantable medical device <NUM> is forced through the exit point <NUM> of the funnel <NUM>, the one or more fibers slide off the external surfaces <NUM> to engage the implantable medical device <NUM>. In certain instances, the one or more fibers are engaged with the implantable medical device <NUM> under tension to maintain the implantable medical device <NUM> in the reduced diameter.

<FIG> show an example funnel <NUM>, constraining mechanism <NUM>, and implantable medical device <NUM> according to some embodiments. The one or more fibers <NUM> may be arranged at an exit point <NUM> of a funnel <NUM> as shown in detail above with reference to <FIG>. As shown in <FIG>, the implantable medical device <NUM> is in a reduced diameter or constrained configuration as it has exited a funnel <NUM>. The funnel <NUM> may include a tapered outer profile at a distal end (e.g., as shown in <FIG>) or may include no outer taper (e.g., as shown in <FIG>). As shown in comparing <FIG> and <FIG>, the funnel <NUM> shown in <FIG> includes an inflection point <NUM> and braiding zone <NUM>, as discussed in further detail above with reference to <FIG> while the funnel <NUM> shown in <FIG> does not include these aspects.

The braider <NUM> and the funnel <NUM> may form a system for forming a constraining mechanism for an implantable medical device delivery. In certain instances, the braider <NUM> is configured to interlock one or more fibers <NUM> along a length of the implantable medical device <NUM> while the implantable medical device <NUM> is in the reduced diameter to form the constraining mechanism. In addition, the one or more fibers <NUM> may be wrapped circumferentially about the implantable medical device <NUM>.

In certain instances, the one or more fibers <NUM> are interlocked using one or more needles <NUM> (or other similar braiding structures such as elongate elements or instruments). The number of needles <NUM> may be equal to the number of fibers <NUM> used by the braider <NUM>. In addition, the one or more fibers <NUM> interlocked together form a constraining mechanism <NUM>. The constraining mechanism <NUM>, as shown in <FIG>, holds the implantable medical device <NUM> in the reduced configuration.

Certain prior constraining mechanisms that use fibers are knit or formed prior to being applied to or arranged about an implantable medical device. The prior constraining mechanisms are formed as a separate component and added as a separate step in a manufacturing process. In addition to the braider <NUM> (and funnel <NUM>) reducing manufacturing steps by interlocking the one or fibers <NUM> directly on the implantable medical device <NUM> while the implantable medical device <NUM> is in the reduced diameter, forming the constraining mechanism <NUM> in this manner allows for a tighter constraint. Prior constraining mechanism, applied to a reduced diameter implantable medical device <NUM> after formation, may allow for the implantable medical device to expand while the prior constraining mechanism is arranged about the implantable medical device. Interlocking the one or more fibers <NUM> directly on the implantable medical device <NUM> minimizes the opportunity for expansion from the reduced diameter. The braider <NUM> and funnel <NUM> capture and constrain the implantable medical device <NUM> in its reduced diameter state. In certain instances, the device can exit the funnel <NUM> at an intermediate diameter and the application of the one or more fibers <NUM> may reduce the diameter to the target profile.

In certain instances, interlocking the one or more fibers <NUM> along the length of the implantable medical device <NUM> includes forming knots by knitting the one or more fibers <NUM> (e.g., as shown in <FIG>). In other instances, interlocking the one or more fibers <NUM> along the length of the implantable medical device <NUM> includes braiding the one or more fibers <NUM> to form the constraining mechanism <NUM> (e.g., as shown in <FIG>). The needles, (or fiber applicator), <NUM> may be automatically actuated to create the desired pattern for the constraining mechanism <NUM>. The needles <NUM> may be move axially and/or rotated about the implantable medical device <NUM> to create knots, seams, or braids staggered about the circumference or the needles <NUM> may be maintained in a single location to create knots, seams, or braids that are aligned (e.g., as shown in <FIG>).

In addition, the braider may interlock the one or more fibers <NUM> bidirectionally. For example, the braider may interlock the one or more fibers <NUM> in a first direction <NUM> to form a first layer of the constraining mechanism <NUM>. The implantable medical device <NUM> may be forced into the braider, from the funnel <NUM>, in the first direction <NUM> (shown in <FIG> and <FIG>) to form the first layer of the constraining mechanism <NUM>. In addition, the one or more fibers <NUM> may be wrapped circumferentially about the implantable medical device <NUM> after or during interlocking the one or more fibers <NUM>. The braider <NUM> may interlock the one or more fibers <NUM> in a second direction <NUM> to form a second layer of the constraining mechanism <NUM>. To form the second layer of the constraining mechanism <NUM>, the implantable medical device <NUM> or the braider <NUM> is moved in the second direction <NUM>.

In certain instances, the one or more fibers <NUM> may be interlocked together while the fibers <NUM> are in tension. The braider <NUM> may mechanically hold the one or more fibers <NUM> in tension during interlocking.

After the constraining mechanism <NUM> is formed, the implantable medical device <NUM> is maintained in the reduced diameter for delivery as noted above. Deploying the implantable medical device <NUM> is accomplished by pulling the end of one or more fibers <NUM> (as shown above with reference to <FIG>) to release or un-knit the constraining mechanism <NUM>.

<FIG> is an example single fiber constraining mechanism according to some embodiments. The constraining mechanism <NUM> may include a portion of a delivery system (e.g., a catheter and expandable medical device as shown in <FIG>). <FIG> shows the constraining mechanism <NUM> in a constrained configuration in which an expandable medical device (not shown) is held to a diameter less than a deployed, expanded or working diameter. The constraining mechanism <NUM> is configured to constrain an expandable medical device to a delivery configuration. In addition, the constraining mechanism <NUM> includes a single fiber <NUM> arranged having a plurality of knots <NUM> to maintain the constraining mechanism <NUM> in a constrained configuration. The plurality of knots <NUM> are configured and arranged such that at least two of the plurality of knots <NUM> are in contact in the constrained configuration.

In certain instances, the single fiber <NUM> forms multiple loops <NUM> arranged circumferentially about the expandable medical device. In addition, and as shown in <FIG>, the multiple loops <NUM> are packed at a density such that at least two of the multiple loops <NUM> are in physical contact. The loops <NUM> are unknotted portions of the single fiber <NUM> between knots of the plurality of knots <NUM>.

The constraining mechanism <NUM> is arranged along a length of the expandable medical device. The constraining mechanism <NUM> is also circumferentially arranged about the expandable medical device and may substantially cover the expandable medical device <NUM> for delivery. The single fiber <NUM> may be arranged within a lumen (not shown) of the catheter and extend toward a proximal end of the catheter <NUM> that is arranged external to a patient during delivery of the expandable medical device. The one or more fibers <NUM> include a proximal end <NUM> that a user may apply tension to in order to release the constraining mechanism <NUM> and deploy the expandable medical device.

<FIG> is an example multi-fiber constraining mechanism <NUM> according to some embodiments. The multi-fiber constraining mechanism <NUM> may be formed by interlocking of multiple fibers together as discussed above with reference to <FIG>. Starting with two fibers, as many fibers as desired and appropriate can be combined in this manner, with the multi-fiber constraining mechanism <NUM> is formed by interlocking the fibers together.

The constraining mechanism <NUM> is arranged along a length of the expandable medical device <NUM>. The constraining mechanism <NUM> is also circumferentially arranged about the expandable medical device <NUM> and may substantially cover the expandable medical device <NUM> for delivery. The single fiber <NUM> may be arranged within a lumen (not shown) of the catheter and extend toward a proximal end of the catheter <NUM> that is arranged external to a patient during delivery of the expandable medical device <NUM>. The one or more fibers <NUM> include a proximal end <NUM> that a user may apply tension to in order to release the constraining mechanism <NUM> and deploy the expandable medical device <NUM>.

The materials used to make the fiber or fibers of the present invention are likewise open to modification and customization for given applications. For most uses discussed herein the fiber or fibers used to form the constraining mechanism <NUM> may include: polytetrafluoroethylene (PTFE); expanded PTFE; silk; thermoplastic threads such as polypropylene; polyamide (nylon); various plastic or metal materials (e.g., stainless steel or nickel-titanium (nitinol) alloy); and bioresorbable materials, such as PLA or PGA. Particularly preferred for use in covering implantable medical devices are polytetrafluoroethylene (PTFE) threads, and especially expanded PTFE threads, such as threads available from W. Gore & Associates, Inc. , Elkton, Md. , under the trademark RASTEX® or sutures available from W. Gore & Associates, Inc. , Flagstaff, Ariz. , under the trademark GORE-TEX®.

Claim 1:
A method of forming a constraining mechanism (<NUM>) for an implantable medical device (<NUM>) delivery, the method comprising:
reducing a diameter of the implantable medical device (<NUM>) from a deployed diameter to a reduced diameter by forcing the implantable medical device (<NUM>) through a funnel (<NUM>) having internal surfaces (<NUM>) reducing in diameter; and
wrapping one or more fibers (<NUM>, <NUM>) circumferentially about the implantable medical device (<NUM>) and the funnel (<NUM>), wherein the funnel (<NUM>) includes a braiding zone (<NUM>) having a length approximately equal to a length of the implantable medical device (<NUM>); and
interlocking the one or more fibers (<NUM>, <NUM>) along a length of the implantable medical device (<NUM>) while the implantable medical device (<NUM>) is in the reduced diameter to form the constraining mechanism (<NUM>).