Multiple layer filamentary devices for treatment of vascular defects

Abstract

Braid-balls suitable for aneurysm occlusion and/or parent vessel occlusion/sacrifice (e.g., in treating neurovascular defects) are disclosed. Especially for aneurysm treatment, but also for either one of the aforementioned treatments, the form of the ball is very important. In particular, the density of the device is paramount in applications where braid itself is intended to moderate or stop blood flow—allowing thrombosis within a volume formed by the ball.

Description

FIELD OF THE INVENTION

The present invention is directed to braid-balls suitable for aneurysm occlusion and/or parent vessel occlusion/sacrifice (e.g., in treating neurovascular defects).

BACKGROUND

Especially for aneurysm treatment, but also for either one of the aforementioned treatments, the form of the ball is very important. In particular, the density of the device is paramount in applications where braid itself is intended to moderate or stop blood flow—allowing thrombosis within a volume formed by the ball.

According to the present invention, braid-ball type implants are provided in braid of sufficient density is provided to moderate blood flow within the volume of the implant. Upon thrombosis, flow thereto is stopped. Alternatively, a blood-barrier covering can be applied to the filamentary structure to immediately stop blood flow into the vascular site, in which the implant volume is set.

In either case, to form thrombosis within the volume of the ball, the filaments of the braid matrix permit filling of the implant with blood when emplaced at a vascular treatment site. This blood then thromboses due to the flow-disruption effect(s).

Unlike Nitinol tube-cut cages that may be suitable for (or assist) in coil retention, the ball devices are adapted to work alone—or in combination with each other to effect a complete treatment. As such, high density braid/mesh is typically required. Namely, braid having at least about 48 ends, typically set at about 90 degrees or greater, in diameters from about 4 to about 8 mm may be employed. At larger diameters (e.g., about 6 to 12 or more), more wire ends (e.g., 64, 72 and upwards) may be employed in forming the balls.

Suitable braid for constructing the balls may be obtained from Secant Medical, Inc. Wire diameters may be in the range of about 0.001 to about 0.003 inches, depending on desired delivery profile (which is typically less than about 0.050 inches). The braid forming the balls may incorporate only one size wire, or may be formed with multiple sizes.

The wire is preferably superelastic NiTi alloy. The metal may be a binary alloy or a ternary alloy to provide additional radiopacity. Alternatively, radiopaque platinum fibers may be included in the braid, or the wire may comprise platinum or gold cord Nitinol DFT. Otherwise, wraps or bands (preferably Pt) used to secure the braid wire may serve as the sole radiopaque feature(s).

In any case, the construction approaches described herein enable producing these useful devices. Whether comprising braid alone, or incorporating some further blood-barrier covering (such as a thin urethane film as may be applied by Hantel, Inc. or others) the use of braid presents numerous challenges in managing the termination of multiple wires and in forming the desired structures.

Also included in the invention are detachable implant pushers that utilize a resistance wire heater to thermally sever a suture associated with the implant to effect release. As distinguished from known approaches where an implant is retained by a loop connected back to a delivery system pusher that is withdrawn with the devilry system, the present invention contemplates a leave-behind tether.

Further details, variations, modification and optional features of the invention may be appreciated by review of any of the incorporated patent applications. However, the priority date and subject matter included in the appended claims rely solely on the subject matter filed in U.S. Provisional Patent Application Nos. 61/046,670 and 61/046,594, the earliest patent applications (each filed Apr. 21, 2008) one which U.S. patent application Ser. No. 12/427,620 relies. Selected figures from the '670 and '594 application and all of text from the '594 application—all—incorporated by reference in the parent application hereto is reproduced herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph taken from U.S. Provisional Patent Application No. 61/046,670 (incorporated herein by reference) demonstrating actual reduction to practice of a single-layer braid ball device made according to the present invention;

FIGS. 2A and 2B are side-sectional views of the braid ball in isolation and in use, respectively;

FIG. 3 illustrates a suture-melt resistance heater pusher for implant delivery;

FIGS. 4A-4F illustrate a production path of one implant embodiment encompassed by the current invention; and

FIGS. 5A and 5B are side-sectional views illustrating proximal-flap braid ball implant variations deployed within bifurcation aneurysm locations.

DETAILED DESCRIPTION OF THE INVENTION

Implants

Referring to the figures, a filamentary implant 2 is formed out of braid to treat vascular sites. Interwoven filaments 4 form a braid matrix 6 that define a self-expandable occlusion device.

As single layer of the braid is provided in which ends of the braid are secured and managed to provide an atraumatic interface. Specifically, ties 10 (as illustrated in FIG. 1) or bands 12 (as illustrated in FIGS. 2A and 2B) secure filament the ends 14 of the braid from which the implant is constructed.

In the implant variation pictured, the expanded configuration defines an ovoid or roughly spherical shell 18 that is permeable to blood. The braid defining the proximal and distal ends of the implant turns or curves inward to a point where it is secured within the periphery of the shell.

The inversion of the braid provides recessed securement of the braid resulting in atraumatic ends of the implant. The braid filaments optionally extend beyond the securing/securement features in order to define wire filament “tufts” 20 that will further promote thrombosis of blood that enters the ball upon deployment within a patient's vasculature. However configured in regard to braid filament end securement and termination, inset ends of the braid (proximal and distal insets 22/24, respectively) are demonstrated when the implant is in an expanded state to fill an aneurysm 26 off of a vessel 28.

Delivery Systems

FIG. 3 illustrates a detachable catheter/pusher 30, optionally, for use in the present invention. Generally, it includes a resistance wire bridge 32 across insulated conductors 34 (a typical construction). What is unique is that the conductor wires are twinned/twisted along a length of the delivery pusher shaft 38 as shown. This configuration alleviates bending bias/preference. Upon application of voltage, the tip thermally severs the polymer filament (e.g., suture 40) in contact therewith. At least the suture portion is received within the implant 2 (e.g., passing through a braid-securing band 12). The suture is retained in/with the implant upon actuation to release the implant by cutting through the suture with heat. A ball stop 42 that is tied to the suture retains the filament in/with the implant is also illustrated. Finally, pusher 30 is shown received within a typical microcatheter 44 for vascular access, after passage therethough. Note also, other advantageous delivery system are referenced and described in the incorporated patent application.

Methods of Manufacture

Included in the intention is a method of manufacture including tying-off or otherwise securing a second end of a braid within an interior volume of a ball where other approaches would be impracticable. The technique may be employed in creating the balls (be they spherical or ovaloid in cross-section, etc.) out of one continuous section of braid. In so doing, joints and other delivery profile-increasing features are avoided—as well as potential areas for failure. Accordingly, the subject implants are extremely robust and fully recoverable to their aneurysmal shape as is required when they are delivered through a catheter in low profile. Robust shape recovery is required in treatments targeting distal vasculature, especially the tortuous neurovasculature encountered in human brains.

A detailed example of one process path for implant formation is illustrated in FIGS. 4A-4F. As shown in FIG. 4F an final implant 2 may begin as a section 50 of braided material. The tubular braid stock is secured. As shown, it is tied-off with a wire wrap 10. Such action develops an inset region 24 for the implant body. An opposite end of the braid is then captured in a transfer tube 52. The tube is passed through the volume of the implant and secured with a second tie 10 at the other side.

Additional refinement to the shape over that shown in FIG. 4E may be imparted within a shape-setting form 54. Mandrels 56 including stops 58 received through the securement features may be employed to force apposition of the ball to the shape of the form when pulled apart as indicated by arrows. After shape-setting in the form (as appropriate to the selected material—e.g., as in heat setting superelastic Nitinol) the mandrels are removed and the implant shaping is complete as shown in FIG. 4F. However, these additional forming steps are not necessary given that (in point of fact) the implant in FIG. 1 was produced without employing the same.

The implants 70, 72 shown in FIGS. 5A and 5B, respectively, may also be dual layer construction. In which case, they would share their distal configuration with the previous implants 20/40/60 shown in FIGS. 1A-3C of U.S. patent application Ser. No. 12/427,620, filed on Apr. 21, 2009. As shown, they are single-layer devices in which the distal end takes the form of an inset hub 74.

Either way, the implants include unique proximal-end configurations. In addition to a ball or bulbous portion 80, each implant includes a flap 76, 78 intended to improve its blood flow disruption potential. Flap 76 included in implant 70 is intended for intra-aneurysmal use. To deliver it as shown, the ball or bulbous portion is first delivered into the aneurysm sac 2. Then, that portion of the device is compressed while still mounted to pusher 100 to deploy the flap section therein. After final positioning is achieved as shown in FIG. 5A, then the pusher locking member(s) received within hub 42 are released. Finally, the pusher is withdrawn into the delivery catheter 110. To assist in the delivery method, one or more additional radiopaque features (such as a band 50 at the proximal end of ball section 80) may be provided so that deployment can be visualized at each stage.

The implant in FIG. 5B requires no such complication in delivery. Because flap 78 is of a size selected only to fill the aneurysm neck, it can be delivered straight-away. Still, intermediate radiopaque features may be desirable to confirm appropriate fit and/or deployment.

As pictured, the ball-and-disk variation of the implant shown in FIG. 5B may only be applicable to smaller-neck aneurysms as compared to the FIG. 5A “acorn” type variation. Generally, the size of the disc will not be significantly larger than the parent/trunk vessel 6 diameter and or that of the bifurcation region 84. Otherwise, the vasculature will interfere with deployment. As such, the disk may be limited to about 2.5 to about 5 mm in diameter.

While understood better in the context of the implant manufacture steps below, flap 78 may be formed using a simple washer or plate over which the braid is heat set. Otherwise, the forming tool may be curved or dished so that flap 78 better follows the contour of the main implant body.

Flap 76 in the FIG. 5A variation will typically be formed using a concave/convex form in similar fashion. The size of this flap may vary. As shown, its outer extent is roughly the same diameter of the ball portion 80 of the device. It may be smaller and/or cover a lesser extent of the proximal side of implant 70. Generally, flap 76 will cover at least about a third and as much as one-half of body 80. In this way, adequate neck coverage is better insured when employed to treat wide-neck aneurysms.

Methods of Use

Any one of the subject implants is delivered to a target site employing known percutaneous catheter access techniques. The implant may be secured to a pusher (e.g., pusher 30) used to advance it through the access catheter (e.g., microcatheter 44). Upon emplacement at the treatment site (e.g., cerebral aneurysm 26 as illustrated in FIG. 2A), the implant can be detached. With the exemplary system shown in FIG. 3, the suture 40 passing through the proximal end of the implant 2 is severed by melting it using a resistance heater. This retention/release fiber remains in and with the implant.

Claims

1. A method of treating a patient, comprising: providing a device for treatment of a patient's vasculature, comprising:a self-expanding resilient permeable shell having a proximal end, a distal end, a longitudinal axis and further including a plurality of elongate resilient filaments with a woven structure secured relative to each other at proximal ends and distal ends thereof, a radially constrained elongated state configured for delivery within a microcatheter, and an expanded relaxed state with a globular configuration relative to the radially constrained elongated state, and an inner structure of filamentary members disposed within an interior volume of the resilient permeable shell and secured to the permeable shell at an end thereof, the inner structure including a plurality of elongate resilient filaments with a woven structure secured relative to each other at least at the proximal ends thereof, which has a radially constrained elongated state which is shorter than the permeable shell in its radially constrained state and which has an expanded relaxed state relative to the radially constrained state;advancing the device to a treatment site within a patient's vasculature in a constrained elongated state; anddeploying the device within a vascular defect at the treatment site within the patient's vasculature such that the permeable shell and inner structure self-expand to their respective expanded states.

2. The method of claim 1, wherein the filaments of at least one of either the permeable shell or the inner structure comprise at least two different transverse dimensions.

3. A self-expanding implant for treating a patient's vasculature, the implant comprising: a resilient, permeable shell having proximal and distal end portions, an interior volume, a longitudinal axis, and a plurality of elongate, woven filaments secured relative to each other at proximal end portions and distal end portions thereof, the shell having a radially constrained, elongated state configured for delivery within a microcatheter and an expanded state relative to its radially constrained, elongated state; andan inner structure, disposed within the shell interior volume, comprising a plurality of elongate, woven filaments and being secured to the shell at the proximal end portion thereof, the inner structure having a radially constrained, elongated state shorter than the radially constrained, elongated state of the shell, the inner structure having an expanded state relative to its radially constrained, elongated state, wherein when the shell and the inner structure self-expand to their respective expanded states, a free, unsecured end portion of the inner structure is longitudinally separated from an inner surface of the shell distal end portion by an internal gap.

4. The device of claim 3, wherein the inner structure filaments are secured at the distal end portion thereof to form an inner hub.

5. The device of claim 3, wherein filaments of the inner structure comprise a woven structure forming a substantially enclosed volume.

6. The device of claim 3, wherein the proximal and distal end portions comprise respective proximal and distal hubs, the proximal and distal hubs being disposed exterior to the interior volume and being inset into the interior volume.

7. An embolic device for treatment a patient's vasculature, the device comprising: a braided structure having an interior volume and comprising a plurality of wires that are secured relative to each other at proximal and distal end portions of the structure to form respective proximal and distal hubs, the proximal and distal hubs disposed exterior to the interior volume and being inset into the interior volume, the structure being adapted to (i) compress into a compressed state, in which the proximal and distal hubs are longitudinally separated at a first distance, for delivery through a microcatheter and (ii) self-expand into an expanded shape, in which the proximal and distal hubs are longitudinally separated at a second distance, less than the first distance, upon release from constraint.

8. The embolic device of claim 7, wherein the expanded shape comprises a globular shape.

9. The embolic device of claim 7, wherein the braided structure comprises a single layer.

10. The embolic device of claim 7, wherein the braided structure comprises inner and outer layers.

11. The embolic device of claim 10, wherein a distal end portion of the inner layer is spaced apart from a distal end portion of the outer layer.

12. The embolic device of claim 11, wherein filaments of the inner layer converge to an unsecured, inner hub to form an inner structure, and wherein filaments of the outer layer converge to the distal hub, the inner hub being spaced apart from the distal hub along a longitudinal axis of the device.

13. The embolic device of claim 12, wherein the inner structure and the outer layer meet at the proximal hub.