Implant delivery assembly with distal protection structure - Patent application

Abstract

To provide an implant delivery system for delivering self-expanding implants that facilitates protection of the implants while avoiding or minimizing an increase in resistive or frictional force through a delivery catheter.SOLUTION: A delivery system for deploying a medical implant 200 includes an elongate delivery wire assembly slidably disposed within a delivery catheter lumen 125, the delivery wire assembly having an implant loading region configured for seating the implant when the delivery wire assembly is constrained within the delivery catheter lumen and the implant is in a compressed delivery configuration.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The presently disclosed invention relates generally to minimally invasive assemblies used in the delivery of medical implants. More specifically, the present disclosure relates to a delivery assembly for delivering a medical implant, such as a tubular stent or flow diverter, to a target implantation site in a patient's vasculature. [Background technology]

[0002]

[0002] The use of endovascular implants, such as stents, stent grafts, flow diverters, aneurysm occlusion devices, and inferior vena cava filters, has become an effective method for treating many types of vascular diseases. Generally, a suitable endovascular implant device is navigated through a patient's vascular system to a target implantation site using a delivery system, such as a catheter having a delivery lumen, that is inserted into the vascular system. Currently available delivery devices can be used to access virtually any target site in a patient's vascular system, including the coronary arteries, cerebral vessels, and peripheral vasculature.

[0003]

[0003] A minimally invasive delivery device comprises a catheter that is percutaneously introduced into a patient's vascular system via a guidewire, and the open distal end of the catheter is navigated to the target implantation site using well-known techniques. A medical implant is then deployed through the catheter's delivery lumen in a compressed (i.e., reduced diameter) delivery configuration and then introduced into the lumen of the blood vessel through the catheter's distal end opening. For example, a self-expanding implant, such as a stent, is delivered in a resiliently compressed state while constrained within a tubular catheter delivery lumen, and then resiliently expands to engage the inner wall of the blood vessel upon deployment from the catheter's open distal end. The expanded and enlarged stent supports and reinforces the vessel wall, thereby maintaining the vessel open and free of obstruction.

[0004]

[0004] Medical implants come in a variety of sizes and shapes. For example, stents and some flow diverters typically assume an expanded, substantially tubular configuration when deployed within a patient's vasculature. Furthermore, medical implants can be made from a variety of materials, including polymers (e.g., non-bioerodible and bioerodible plastics) and metals. Medical implants can be made from shape-memory or superelastic materials, such as shape-memory metals (e.g., shape-memory nitinol) and polymers (e.g., polyurethane). Such shape-memory implants can be induced (e.g., by temperature, electric or magnetic fields, or light) to assume a specific shape (e.g., a radially expanded shape) after delivery to a treatment site. Superelastic embolic materials, such as superelastic nitinol, can assume a certain shape after delivery without the need for an inducing stimulus. Other commonly used materials include stainless steel, platinum, and Elgiloy. Drug delivery implants can carry bioactive or therapeutic agents and / or the surface of the device can be coated with bioactive or therapeutic agents. Commonly used medical implants, such as stents, stent grafts, and flow diverters, may be constructed from multiple filaments (e.g., wires) braided or woven into a predetermined (e.g., tubular) shape, or may be made from laser-cut tubes.

[0005] Known delivery systems include retention sleeves to control release or covers to protect the implant ends during deployment, as described (for example) in U.S. Patent Nos. 6,478,814, 6,830,575, and 8,591,566. Such sleeves / covers include wings or separate members, are more difficult to manufacture, and can increase the resistance and friction forces exerted by the device assembly as it is pushed through the delivery catheter, negatively affecting the overall performance of the delivery system.

[0006]

[0006] Therefore, there is a continuing need to provide an implant delivery system for delivering self-expanding implants that facilitates protection of the implant while avoiding or minimizing increased resistance or frictional forces through the delivery catheter. Summary of the Invention

[0007]

[0007] In one embodiment of the disclosed invention, a delivery system is provided for deploying an implant at a target site within the vasculature of a mammal, the implant having a compressed delivery configuration and an expanded deployed configuration, the delivery system comprising a delivery catheter having a lumen and an elongated delivery wire assembly at least partially disposed within the lumen of the delivery catheter, the delivery wire assembly being translatable relative to the delivery catheter, a distal portion of the delivery wire assembly including the implant being restrained within the lumen of the delivery catheter, and an implant loading region configured to seat the implant when the implant is in the compressed delivery configuration. The delivery wire assembly includes an implant distal protection structure including a central portion coupled distally to the implant loading region of the delivery wire assembly and a peripheral portion extending proximally from the central portion to at least partially cover a distal end portion of the implant when the distal portion of the delivery wire assembly including the implant and implant distal protection structure is constrained within the delivery catheter lumen, the peripheral portion of the implant distal protection structure remaining extending proximally when the implant assumes an expanded configuration after being released from the delivery catheter lumen and no longer covered by the implant distal end protection feature.

[0008] In various embodiments, the peripheral portion of the implant distal protective structure can be comprised of a plurality of circumferentially spaced petal-like portions extending from a central portion. By way of non-limiting example, in one embodiment, the peripheral portion of the implant distal protective structure consists of three petal-like portions substantially equally spaced around the delivery wire assembly.

[0009]

[0009] In one embodiment, when the distal portion of the delivery wire assembly, including the implant and the implant distal protective structure, is constrained within the delivery catheter lumen, the implant distal protective structure covers approximately 20 percent of the total length of the implant.

[0010]

[0010] In another embodiment, when the distal portion of the delivery wire assembly including the implant and the implant distal protective structure is constrained within the delivery catheter lumen, the implant distal protective structure covers approximately 10 percent to approximately 20 percent of the total length of the implant.

[0011]

[0011] In yet another embodiment, when the distal portion of the delivery wire assembly including the implant and the implant distal protective structure is constrained within the delivery catheter lumen, the implant distal protective structure covers approximately 5 percent to approximately 10 percent of the total length of the implant.

[0012]

[0012] In yet another embodiment, when the distal portion of the delivery wire assembly including the implant and the implant distal protection structure is constrained within the delivery catheter lumen, the implant protection member covers less than about 5 percent of the total length of the implant.

[0013]

[0013] The central portion of the implant distal protection structure may be fixedly attached to the delivery wire assembly such that the implant distal protection structure cannot rotate relative to the delivery wire assembly. In an alternative embodiment, the central portion of the implant distal protection structure is attached to the delivery wire assembly such that the implant distal protection structure can rotate relative to the delivery wire assembly.

[0014] Other and further aspects and features of the embodiments of the invention disclosed herein will become apparent from the following detailed description, taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a side view of an implant delivery system constructed in accordance with one embodiment of the disclosed invention. [Figure 2]

[0016] 2A-E are partial cutaway side, perspective, and exploded views of the delivery wire assembly of the implant delivery system of FIG. 1, showing in greater detail the portion of the system that includes the implant distal protection structure. [Figure 3]

[0017] FIG. 3 is an elevated end view of the implant distal protection structure shown in FIG. 2E, with the implant distal protection structure fully open. [Figure 4]

[0018] 4A-D are cutaway, side, and perspective views of an implant distal protection structure with a delivery wire assembly loaded into a delivery catheter 120, according to one embodiment of the disclosed invention. [Figure 5]

[0019] 5A-D' are side and perspective views of an implant distal protection structure during delivery and deployment of the implant at a target site in the vasculature using the implant delivery system of FIGS. 1-4. DETAILED DESCRIPTION OF THE INVENTION

[0016]

[0020] For the following definitions of terms, these definitions shall be applied unless a different definition is given in the claims or elsewhere in this specification.

[0017]

[0021] As used herein, all numerical values, whether explicitly stated or not, are intended to be modified by the term "substantially" or "about." The terms "substantially" and "about" refer to a range of numbers that one of ordinary skill in the art would consider equivalent to a recited parameter, structure, or value (i.e., having the same function or result). In many cases, the terms "about" and "substantially" include numbers that are rounded to the nearest significant figure. The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

[0018]

[0022] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is used generally in its sense, including "and / or," unless the content clearly dictates otherwise.

[0019]

[0023] As used herein and in the appended claims, the terms "proximal" and "proximally" (and the like) refer to the relative position, position or direction of a structure, or movement of an implant delivery system outward from a patient's body, and the terms "distal" and "distal" (and the like) refer to the relative position, position or direction of a structure, or movement of an implant delivery system extending deeper into a patient's body.

[0020]

[0024] Various embodiments of the disclosed invention are described below with reference to the drawings. The drawings are not necessarily drawn to scale, the relative scale of selected elements may be exaggerated for clarity, and elements of similar structure or function are represented by like reference numerals throughout the figures. It should also be understood that the drawings are intended only to facilitate description of the embodiments and are not intended as an exhaustive description of the disclosed invention or as limiting its scope, which is defined solely by the appended claims and equivalents thereof.

[0021]

[0025] Moreover, each illustrated embodiment of the disclosed invention(s) need not have all of the described features, and any feature, aspect, or advantage described in connection with a particular embodiment is not necessarily limited to that embodiment and may be implemented in other embodiments even if not so indicated.

[0022]

[0026] FIG. 1 illustrates an implant delivery system 100 configured in accordance with one embodiment of the disclosed invention. The implant delivery system 100 generally comprises an elongated tubular delivery catheter 120 having a proximal end portion 130, a distal end portion 160, and a lumen 125 extending therebetween, the lumen 125 of the delivery catheter communicating with the respective open proximal and distal ends of the delivery catheter 120. The delivery catheter 120 is coaxially disposed within and movable relative to an outer sheath 180, which is used to assist in positioning the distal end portion 160 of the delivery catheter 120 in a target portion of the vasculature. The proximal end portion 130 of the delivery catheter 120 comprises a fluid port 150 (distal to a proximal opening of the outer sheath 180 through which the delivery catheter 120 is inserted) which is used to introduce fluid into the lumen 125. The fluid delivery port 150 remains outside the patient's body for access by a physician / operator when the implant delivery system 100 is inserted into the patient's vasculature. The distal portion 160 of the delivery catheter 120 is sized and dimensioned to access remote locations within the vasculature, such as within the neurovasculature, and may have a smaller diameter (or profile) than the proximal portion 130.

[0023]

[0027] Implant delivery system 100 further includes implant delivery wire assembly 300 (described in detail below with respect to FIGS. 2A-E ), which includes a core wire 350 that is advanced through delivery catheter lumen 125, carrying implant 200 (not shown in FIG. 1 ) at its distal end portion for delivery to a target site in the patient's vasculature. As shown in FIG. 1 , core wire 350 is inserted through a proximal end opening of delivery catheter 120 and pushed through delivery lumen 125 such that an atraumatic distal tip portion (e.g., a soft coil member) 380 attached to the distal end of core wire 350 extends from the distal end opening of delivery catheter 120.

[0024]

[0028] The outer sheath 180 of the implant delivery system 100 can be introduced into the vasculature over a previously introduced guidewire (not shown) (known as an over-the-wire configuration), or it can be introduced in the well-known "rapid-exchange" configuration, in which the guidewire extends from a guidewire port (not shown) through only the distal portion of the outer sheath 180. The delivery catheter 120 is then introduced through the outer sheath, either over the guidewire or not, also as is well known. The outer sheath 180 has a radiopaque marker 355 adjacent its open distal end to aid in positioning the sheath at a target location in the vasculature.

[0025]

[0029] The delivery catheter 120 can be constructed from a suitable polymeric material, metal, and / or alloy, such as polyethylene, stainless steel, or other suitable biocompatible material, or a combination thereof. In some cases, the proximal portion 130 can include a reinforcing layer, such as a braided or coiled layer, to enhance pushability. The delivery catheter 120 can include one or more transition regions between the proximal portion 130 and the distal portion 160. The distal end portion 160 can have an outer diameter smaller than that of the proximal portion 130 to reduce the profile of the distal end portion 160 and facilitate navigation of the distal end portion 160 extending from the distal opening of the outer sheath 180 through tortuous vasculature. The proximal end portion 130 may be formed from a stiffer material than the distal portion 160 of the delivery catheter 120 so that the proximal end portion 130 has sufficient pushability to advance through the patient's vasculature, while the distal portion 160 may be formed from a more flexible material so that the distal portion 160 maintains flexibility to more easily track over a guidewire to access remote locations in tortuous regions of the vasculature. As best seen in FIG. 2A , a tapered radiopaque marker 455 and an atraumatic tip 457 are each disposed near the distal end opening 452 of the delivery catheter 120.

[0026]

[0030] 2A-E, implant 200, which may be a stent, flow diverter, or other type of vascular implant, is carried on the distal portion of core wire 350. Implant 200 can comprise a variety of biocompatible materials, such as stainless steel, Elgiloy, nickel, titanium, nitinol, shape-memory polymers, or combinations thereof, and can be constructed using well-known techniques by etching or cutting patterns from a tube or sheet of stent material or by weaving / braiding one or more wires or ribbons into the desired shape and pattern. Implant 200 may include additional components welded, bonded, or otherwise engaged to one another and may optionally include non-porous, non-permeable biocompatible materials, covers, etc.

[0027]

[0031] As best shown in Figure 2D, implant 200 is generally tubular, having a proximal portion 220, a distal portion 240, and a lumen 260 extending therebetween. In particular, implant 200 is depicted in Figures 2A-E in a compressed, elongated delivery configuration disposed (i.e., radially constrained) within lumen 125 of delivery catheter 120. Implant 200 is preferably biased to self-expand radially outward to its expanded, deployed configuration when deployed (i.e., no longer radially constrained) from the distal end opening of delivery catheter 120.

[0028] 2A-B, a core wire 350 of a delivery wire assembly 300 is coaxially disposed within a delivery catheter lumen 125, and an implant 200 is coaxially disposed around the core wire 350 and is also constrained within the delivery catheter lumen 125. In particular, the core wire 350 is axially movable relative to the delivery catheter 120, and as the core wire 350 is translated axially through the delivery catheter lumen 125, the delivery wire assembly 300 is configured to engage the implant 200 to deliver the implant 200 to a target implantation site in the vasculature. The interface between the delivery wire assembly 300 and the implant 200 is described in more detail below.

[0029] A radiopaque marker 360 (e.g., a laser-etched radiopaque band or any other suitable marker) is preferably placed along the distal portion of the core wire 350 to aid in positioning the core wire 350 and implant 200 relative to the delivery catheter 120. In the illustrated embodiment, a coil 357 is placed around the core wire 350 to provide structural support just proximal to the implant 200. A radiopaque marker band 360 is placed on the distal portion 358 of the coil 357 to indicate the location of the proximal end portion 220 of the implant 200. An epoxy bond 376 is used to attach the marker 360 to the core wire 350.

[0030] As shown in FIGS. 2B-C, a re-covering pad 370 is placed around the core wire 350 distal to the coil 357, and an implant re-covering bumper 375 is attached to the core wire 350 at the distal end of the re-covering pad 370. An epoxy bond 376 is used to attach the re-covering bumper to the core wire 350. This region of the core wire 350 where the implant 200 is loaded is referred to herein as the implant loading region. In particular, the proximal portion 220 of the implant 200 is placed over the respective re-covering pads 370 and re-covering bumpers 375, and the distal end of the distal portion 240 of the implant 200 is covered by a distal protective structure 500 attached to the core wire 350 and secured between respective proximal and distal locking members 550 ( FIG. 2E ). In most figures, only the distal locking member 550 is shown because the proximal locking member 550 is hidden by the implant distal protective structure 500. However, the proximal locking member is shown in Figure 5C (discussed below). An atraumatic distal tip 380 (e.g., a soft coil member) is attached to the core wire near the distal locking member 550 (Figures 2B, 2E).

[0031]

[0032] FIG. 3 illustrates an implant distal protective structure 500 of a delivery wire assembly 300, according to one embodiment of the disclosed invention. The implant distal protective structure 500 is preferably constructed from a biocompatible material, such as ePTFE. In one embodiment, the implant distal protective structure 500 is made of a thin, substantially uniform layer of ePTFE having a thickness of approximately 0.0152 millimeters (0.0006 inches) and a length L of approximately 0.44 millimeters (0.0173 inches). As shown in FIG. 3, the implant distal protective structure 500 comprises a peripheral portion in the form of three circumferentially spaced petal-like members (or "petals") 520 that meet at a central portion 511 attached to the core wire 350 (FIG. 2E). As shown in FIG. 4A (discussed below), the peripheral petals 520 extend generally radially outward from the central portion 511 and point in a proximal direction when the implant distal protective structure 500 is unconstrained within the delivery catheter 120.

[0032]

[0033] In the illustrated embodiment, the implant distal protection structure 500 is fixedly attached to the core wire 350 by the locking member 550 so that the implant distal protection structure does not rotate relative to the core wire 350. In an alternative embodiment, the implant distal protection structure 500 may be attached to a collar (not shown) that is still fixed in its relative longitudinal position to the core wire 350 by the locking member 550 so that the collar, and therefore the implant distal protection structure 550, can rotate relative to the core wire 350 and the locking member 550.

[0033]

[0034] 4A-D illustrate front-loading of a delivery wire assembly 300 into a delivery catheter 120, according to one embodiment of the disclosed invention. FIG. 4A shows the distal end portion of the delivery wire assembly 300, including an implant distal protective structure 500 and an implant 200, immediately prior to loading into the delivery catheter 120, with the peripheral petals 520 of the implant distal protective structure 500 shown extending generally proximally in a radially unconstrained configuration. The implant 200 is coaxially disposed about a core wire 350 (not shown) and held in a radially constrained delivery configuration by a tubular loading member 390, with the distal end portion 240 of the implant 200 at least partially exposed through a distal end opening of the loading member 390.

[0034]

[0035] The distal end portion of the delivery wire assembly 300, including the implant distal protective structure 500 and the compressed implant 200, is advanced into the delivery catheter 120, and / or the delivery catheter 120 is advanced over the distal portion of the delivery wire assembly 300, such that the peripheral petals 520 of the implant distal protective structure 500 are radially compressed to overlie the distal portion 240 of the implant 200, as shown in FIGS. 4B-C. Once the delivery catheter 120 is positioned over the respective implant distal protective structure 500 and loading member 390, the loading member 390 is retracted, while the implant 200 remains in the compressed delivery configuration within the lumen 125 of the delivery catheter 120, and the peripheral petals 520 of the implant distal protective structure 500 remain compressed over and at least partially cover the distal portion 240 of the implant 200 (FIG. 4D).

[0035]

[0036] Although the disclosed invention is not so limited, the depicted "three-leaf" configuration of the implant distal protection structure 500 is configured to minimize the amount of material covering the distal end of the distal portion 240 of the implant 200, thereby reducing and minimizing the drag or frictional forces imparted by the implant on the inner wall of the delivery catheter 120 as the implant 200 is pushed through the lumen 125. In particular, the inventors of the disclosed invention have found that by employing the depicted three-leaf configuration of the implant distal protection structure 500, the coefficient of friction between the implant 200 and the inner wall of the delivery catheter 120 is in the range of about 0.01 to about 0.04 when there is relative motion between the core wire 350 and the delivery catheter 120.

[0036]

[0037] In various embodiments, the implant distal protective structure 550 can be sized and configured to cover different amounts of the distal portion 240 of the implant 200 when the distal portion of the delivery wire assembly 300, including the implant 200 and the implant distal protective structure 500, is constrained within the delivery catheter lumen 125. By way of non-limiting example, in one embodiment, the implant distal protective structure 500 is sized and configured to cover 20 percent of the total length of the implant 200 when the distal portion of the delivery wire assembly 300, including the implant 200 and the implant distal protective structure 500, is constrained within the delivery catheter lumen 125. In another embodiment, the implant distal protective structure 500 is sized and configured to cover between about 10 percent and about 20 percent of the total length of the implant 200 when the distal portion of the delivery wire assembly 300, including the implant 200 and the implant distal protective structure 500, is constrained within the delivery catheter lumen 125. In yet another embodiment, the implant distal protective structure 500 is sized and configured to cover about 5 percent to about 10 percent of the total length of the implant 200 when the distal portion of the delivery wire assembly 300, including the implant 200 and the implant distal protective structure 500, is constrained within the delivery catheter lumen 125. In yet another embodiment, the implant distal protective structure 500 is sized and configured to cover about 5 percent or less of the total length of the implant 200 when the distal portion of the delivery wire assembly 300, including the implant 200 and the implant distal protective structure 500, is constrained within the delivery catheter lumen 125.

[0037]

[0038] 5A-D' show the implant distal protection structure 500 during delivery of the implant 200 to a target site in the vasculature (not shown) or during deployment at the target site.

[0038]

[0039] 5A illustrates the distal end portion of the delivery wire assembly 300 as the core wire 350 (not visible in FIG. 5A ) is pushed through the delivery catheter lumen 125. The implant 200 and distal implant protective structure 500, shown in a compressed delivery configuration, are constrained within the delivery catheter lumen 125, with the peripheral petals 520 of the implant distal protective structure 500 covering and protecting the distal portion 240 of the implant 200.

[0039]

[0040] Once the distal end portion of the delivery assembly 300 is positioned near the target implantation site, the delivery catheter 120 is retracted proximally relative to the core wire 350, or the core wire 350 is pushed distally relative to the delivery catheter 120, or both, thereby exposing the implant distal protective structure 500 and the implant 200 from the distal end opening 452 of the delivery catheter 120 and allowing the now radially unconstrained implant 200 to radially self-expand, beginning at the distal end portion 240, to the expanded configuration, as shown in FIGS. 5B-5D′. Notably, when the distal end portion 240 of the implant 200 assumes the expanded configuration and is no longer covered by the implant distal protective structure 500, the peripheral petals 520 of the implant distal protective structure 500 remain extending generally proximally (i.e., in the “delivery configuration”).

[0040]

[0041] The implant distal protective structure 500 is preferably configured to exert negligible or otherwise insignificant force on the distal portion 240 of the implant 200 as the implant 200 expands. In some embodiments, the implant distal protective structure 500 can expand radially outward when it is no longer radially constrained by the delivery catheter 120. In any embodiment, the peripheral petals 520 are configured to extend and / or point proximally when the implant distal protective structure 500 remains in the delivery configuration or when it expands outward when it is no longer constrained by the delivery catheter 120; i.e., the individual petals 520 preferably do not evert as the implant 200 expands.

[0041]

[0042] After deploying the implant 200 at the target site, the delivery wire assembly 300 is retracted within the delivery catheter (not shown), and the delivery system 100 is withdrawn from the body, leaving the expanded implant 200 at the target site. In particular, as shown in FIGS. 5D-5D′, the “proximally facing” configuration of the implant distal protection structure 500 and its relatively small size relative to the expanded implant 200 allow the core wire 350 and distal implant protection member 500 to be retracted through the lumen 260 of the implant 200 and into the delivery catheter lumen 125 without interfering with the deployed, expanded implant 200. FIG. 5D′ is an enlarged view of the portion shown in FIG. 5D , better illustrating that the implant distal protection structure 500 substantially retains its delivery configuration even when the delivery catheter 120 no longer constrains the implant distal protection structure 500.

[0042]

[0043] While particular embodiments have been shown and described herein, they are not intended to limit the disclosed invention, and it will be apparent to those skilled in the art that various changes, permutations, and modifications (e.g., various part dimensions, combinations of parts) can be made without departing from the scope of the disclosed invention, which is defined solely by the claims and their equivalents. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. The various embodiments shown and described herein are intended to cover alternatives, modifications, and equivalents of the disclosed invention, which may be included within the scope of the appended claims.

Claims

1. 1. A delivery system for deploying an intravascular implant, the implant having a compressed delivery configuration and an expanded deployed configuration, the delivery system comprising: a tubular member having a lumen; an elongate delivery assembly partially disposed within the lumen of the tubular member and slidingly translatable relative to the tubular member, the elongate delivery assembly including an implant loading region configured to deploy the implant when a distal portion of the delivery assembly containing the implant is constrained within the lumen of the tubular member such that the implant is in a compressed delivery configuration; an implant distal protection element including a central portion coupled distally to the implant loading region of the elongate delivery assembly and a peripheral portion extending proximally from the central portion to partially cover a distal end portion of the implant when the distal portion of the elongate delivery assembly including the implant and the implant distal protection element is constrained within the lumen of the tubular member; The system is characterized in that the peripheral portion of the implant distal protection element is configured to expand without inverting from a proximal-facing direction to a distal-facing direction when the peripheral portion of the implant distal protection element is no longer constrained by the tubular member.

2. The delivery system of claim 1 , wherein the peripheral portion of the implant distal protection element comprises a plurality of circumferentially spaced petal-like portions extending from the central portion.

3. The delivery system of claim 2 , wherein the peripheral portion of the implant distal protection element is composed of three petal-like portions.

4. 4. The delivery system of claim 2 or 3, wherein the petal-like portions are substantially equally spaced circumferentially around the elongate delivery assembly.

5. The delivery system of claim 1 , wherein the elongate delivery assembly comprises a wire, a coil, or a strand.

6. The delivery system of claim 1 , wherein the tubular member comprises a delivery catheter, a microcatheter, or a cannula.

7. 2. The delivery system of claim 1, wherein the peripheral portion of the implant distal protection element remains extended proximally when the implant assumes an expanded, deployed configuration after the implant is released from the lumen of the tubular member and is no longer covered by the peripheral portion of the implant distal protection element.

8. 2. The delivery system of claim 1, wherein the implant distal protection element covers approximately 20 percent of the total length of the implant when the distal portion of the elongate delivery assembly including the implant and the implant distal protection element is constrained within the lumen of the tubular member.

9. 2. The delivery system of claim 1, wherein the implant distal protection element covers about 10 to about 20 percent of the total length of the implant when the distal portion of the elongate delivery assembly including the implant and the implant distal protection element is constrained within the lumen of the tubular member.

10. 2. The delivery system of claim 1, wherein the implant distal protection element covers about 5 to about 10 percent of the total length of the implant when the distal portion of the elongate delivery assembly including the implant and the implant distal protection element is constrained within the lumen of the tubular member.

11. 2. The delivery system of claim 1, wherein the implant distal protection element covers less than about 5 percent of the total length of the implant when the distal portion of the elongate delivery assembly including the implant and the implant distal protection element is constrained within the lumen of the tubular member.

12. The delivery system of claim 1 , wherein a central portion of the implant distal protection element is fixedly attached to the elongate delivery assembly such that the implant distal protection element is not rotatable relative to the elongate delivery assembly.

13. The delivery system of claim 1 , wherein a central portion of the implant distal protection element is attached to the elongate delivery assembly such that the implant distal protection element can rotate relative to the elongate delivery assembly.

14. 10. The delivery system of claim 1, wherein the implant distal protection element is configured to exert negligible or otherwise insignificant force on a distal portion of the implant when the implant expands from a compressed delivery configuration to an expanded deployed configuration.

15. The delivery system of claim 1 , wherein the implant distal protection element substantially retains the compressed delivery configuration after the implant distal protection element radially expands and is no longer constrained by the tubular member.

16. The delivery system of claim 1 , wherein the implant distal protection element is configured to prevent inversion in a distally facing direction when the implant expands.

17. The delivery system of claim 1 , wherein the implant distal protection element is configured to be pulled back within the tubular member without reversing from the proximal-facing direction to the distal-facing direction.

18. 10. The delivery system of claim 1, wherein the implant distal protection element comprises a biocompatible material having a thickness of approximately 0.0006 inches (0.001524 centimeters) and a length of approximately 0.0173 inches (0.043942 centimeters).

19. 20. The delivery system of claim 18, wherein the peripheral portion of the implant distal protection element consists of three petal-like portions circumferentially spaced about and extending from the central portion.

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