System and method for occluding a vascular cavity

Abstract

A system for forming an occlusive structure within a vascular cavity, the system comprising : a filament delivery assembly configured to advance a filament through a microcatheter into the vascular cavity; a cutting assembly disposed coaxially relative to the microcatheter, the cutting assembly comprising : (i) a gripping mechanism comprising a resilient element configured to radially engage the filament; and (ii) a cutting element positioned proximal to the gripping mechanism; wherein the system is configured such that : (a) withdrawal of the microcatheter relative to the cutting assembly causes the gripping mechanism of the cutting assembly to engage the filament; and (b) proximal movement of the filament relative to the cutting element tensions the filament against the cutting element to sever the filament.

Description

[0001] SYSTEM AND METHOD FOR OCCLUDING A VASCULAR CAVITY

[0002] Reference To Pending Prior Patent Application

[0003] This patent application claims benefit of pending prior U. S . Provisional Patent Application Serial No .

[0004] 63 / 788, 960, filed 04 / 15 / 2025 by Machiel van der Leest et al . for SYSTEM AND METHOD FOR TREATING A VASCULAR CAVITY BY FILLING THE VASCULAR CAVITY AND / OR SHIELDING THE VASCULAR CAVITY (Attorney' s Docket No . MVL-1 PROV) .

[0005] The above-identified patent application is hereby incorporated herein by reference .

[0006] Field Of The Invention

[0007] This invention relates to a novel embolization device for the occlusion of vascular lumens (e . g. , arteries, veins, lumens of the sinus system, etc . ) and cavities, and to the treatment of vascular pathologies in general, and more particularly to novel systems and methods for occluding aneurysms in both arterial and venous structures . The novel system of the present invention is configured for use via either an endovascular or percutaneous approach.

[0008] More specifically, the present invention relates to the treatment of neurovascular conditions, in particular, for the treatment of endovascular occlusion of fusiform and saccular aneurysms, parent artery occlusion, and the occlusion of venousdilatations, venous cavities, and draining veins in, for example, dural arteriovenous fistulas and arteriovenous malformations and vein of Galen malformations . In such cases, if desired, the novel system of the present invention may be used in combination with adjunctive devices such as stents, flow diverters or balloons .

[0009] Background Of The Invention

[0010] Aneurysms are one fairly common vascular pathology that can cause significant detrimental health effects (including death) if not properly treated. An aneurysm is, generally speaking, an outward bulging area of a blood vessel wall that is caused by a localized, abnormal weak spot on the blood vessel wall . In certain circumstances, the weak spot on the blood vessel wall can begin to bulge outward, with the result that blood is redirected from the pathway of the blood vessel into the bulge . Over time, the bulge can grow into a hollow, blood-filled structure as more blood is redirected into the interior of the aneurysm, and over time the aneurysm can grow and eventually leak or burst . Inasmuch as some aneurysms are located along major blood vessels such as the aorta, and / or in sensitive, space-limited areas of the body (e . g. , the brain) , the growth of an aneurysm can put pressure on the surrounding anatomy with detrimental effects (e . g. , pressure on a portionof the brain) , or the aneurysm may burst and allow blood into the internal cavities of the body (resulting in death if not immediately addressed by emergency surgical intervention) .

[0011] Aneurysms are traditionally treated by either surgical intervention or watchful waiting (combined with control of blood pressure, etc . , which may help arrest the growth of the aneurysm) . Cerebral aneurysms present a special case due to the difficulty of effecting surgical intervention in the human brain. Surgical approaches to treating cranial aneurysms are generally limited to surgical clipping (i . e . , performing a craniotomy to expose the aneurysm, and then clipping the neck / base of the aneurysm with a surgical clip) , or endovascular coiling, which consists of passing a catheter into the femoral or radial artery, through the aorta, into the brain arteries, and into the aneurysm itself (i . e . , the interior "cavity" of the aneurysm, sometimes hereinafter referred to as the aneurysm "dome" or "sac") . With endovascular coiling, a plurality of separate platinum coils are inserted into the aneurysm to initiate a clotting reaction that, if successful, fills the aneurysm dome and prevents its rupture .

[0012] With current approaches using endovascular coiling, in order to achieve complete filling of the aneurysm sac, multiple coils (e . g. , platinum coils) are typically required. However, the process ofdelivering a plurality of coils to the aneurysm dome (sometimes hereinafter also referred to as the aneurysm "sac") can be time-consuming and may lead to both increased procedural duration and increased radiation exposure .

[0013] In addition, the metallic coils typically employed by prior art endovascular coiling approaches can obscure visualization of the surrounding brain tissue and the aneurysm neck, making it challenging to visualize the aneurysm / surrounding anatomy on followup imaging studies (e . g. , CT or MRI scans) . This limited visibility can make it difficult to assess the efficacy of coil placement within the aneurysm sac and the presence of residual aneurysm and / or to delineating pathologies (e . g. bleedings, enema, vascular structures) arising close to the coil mass . Furthermore, the high radio opacity of metal coils may complicate the visualisation and treatment of further aneurysms of the intracranial arteries, present in approximately 20-25% of all patients .

[0014] Since increased procedural time is generally associated with higher cost and higher complication rates for the procedure, and since such procedures normally must be performed under radiologic guidance (with increased radiation exposure to the patient and, potentially, to personnel performing the procedure) , there exists a need for new and improved systems and methods which shorten the length of the procedure .

[0015] MVL-1Furthermore, the metallic coils typically employed by prior art endovascular coiling approaches are not specifically sized and shaped to the anatomy of the patient . Therefore, if the metallic coil placed into an aneurysm is too large, the metallic coil can put pressure on the wall of the aneurysm, which could rupture the aneurysm. Alternatively, if the metallic coil placed into an aneurysm is too small, the metallic coil could fall out, or protrude out, of the aneurysm and cause damage to other areas of the vascular system.

[0016] Thus there is a need for a new and improved system and method for filling the dome of an aneurysm with an occlusion-inducing material, which system and method permits the surgeon to insert as much of the material as necessary to fill the volume of the dome of the aneurysm, and such that the material used to fill the dome of the aneurysm can be selectively cut by the surgeon once deployed into the dome of the aneurysm .

[0017] Summary Of The Invention

[0018] The present invention comprises a new and improved system and method for filling a body cavity or occluding an arterial lumen, such as the dome of an aneurysm, with an occlusion-inducing material, which system and method permits the surgeon to insert as much of the material as necessary to fill the volume

[0019] MVL-1of the cavity or lumen (e . g. , the dome of an aneurysm) , and such that the material used to fill the cavity or lumen can be selectively cut by the surgeon once deployed into the dome of the aneurysm.

[0020] In a preferred form of the invention, there is provided a system for forming an occlusive structure within a vascular cavity, the system comprising:

[0021] a filament delivery assembly configured to advance a filament through a microcatheter into the vascular cavity;

[0022] a cutting assembly disposed coaxially relative to the microcatheter, the cutting assembly comprising:

[0023] (i) a gripping mechanism comprising a resilient element configured to radially engage the filament; and

[0024] (ii) a cutting element positioned proximal to the gripping mechanism;

[0025] wherein the system is configured such that :

[0026] (a) withdrawal of the microcatheter relative to the cutting assembly causes the gripping mechanism of the cutting assembly to engage the filament; and (b) proximal movement of the filament relative to the cutting element tensions the filament against the cutting element to sever the filament .

[0027] In another preferred form of the invention, there is provided apparatus for positioning within a vascular cavity for occluding the vascular cavity, the apparatus comprising:

[0028] MVL-1a filament configurable between:

[0029] (i) a substantially linear configuration for delivery to the vascular cavity; and

[0030] (ii) an occluding configuration that forms an occluding structure upon advancement of the filament into the vascular cavity;

[0031] wherein advancement of the filament into the vascular cavity causes the filament to deform into a plurality of apposing folds of the filament along a boundary of the vascular cavity, whereby to conform to dimensions of the vascular cavity, and further wherein continued advancement of the filament into the vascular cavity forms concentric layers accumulating from the boundary of the vascular cavity toward a center of the vascular cavity.

[0032] In another preferred form of the invention, there is provided a method for forming an occlusive structure within a vascular cavity, the method comprising :

[0033] advancing a filament through a microcatheter into the vascular cavity to form the occlusive structure within the vascular cavity;

[0034] withdrawing the microcatheter relative to a coaxial cutting assembly to engage the filament with a gripping mechanism;

[0035] applying tension to the filament to move the filament against a cutting element; and

[0036] MVL-1severing the filament against the cutting element .

[0037] Brief Description Of The Drawings

[0038] These and other obj ects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein:

[0039] Fig. 1 is a schematic view showing two existing approaches to treating vascular defects and or malformations in the anatomy;

[0040] Figs . 2A-2C are schematic views showing a novel delivery and cutting system configured to fill a cavity in the anatomy with a filling material;

[0041] Figs . 2D-2F are schematic views showing the novel delivery and cutting system of Figs . 2A-2C configured to fill a cavity in the anatomy with a filling material without the use of a stent or balloon catheter;

[0042] Figs . 3-5 show exemplary materials and properties for the filling material of the system of Fig. 2 ;

[0043] Figs . 6 and 7A-7C are schematic views showing further aspects of the novel system of Figs . 2A-2F, formed in accordance with the present invention;

[0044] MVL-1Figs . 8 and 9 are schematic views showing the novel system of Figs . 2A-2F being used to fill a model aneurysm;

[0045] Figs . 9A-9E are schematic views showing a novel telescopic loading tool for loading a filament into a cavity in the anatomy;

[0046] Figs . 10, 11A-11C, 12, 13A-13D and 14 are schematic views showing further aspects of the novel system of Figs . 2A-2F, formed in accordance with the present invention;

[0047] Figs . 15-21 show an exemplary filling procedure for a model aneurysm using the novel system of Figs .

[0048] 2A-2F;

[0049] Figs . 22-31 show a further exemplary filling procedure for a model aneurysm using the novel system of Figs . 2A-2F; and

[0050] Fig. 32 is a schematic view showing aspects of the filling material of the system of Figs . 2A-2F, formed in accordance with the present invention.

[0051] Detailed Description Of The Preferred Embodiments The present invention comprises a new and improved system and method for filling a body cavity or occluding an arterial lumen, such as the dome of an aneurysm, with an occlusion-inducing material, which system and method permits the surgeon to insert as much of the material as necessary to fill the volume of the cavity or lumen (e . g. , the dome of an

[0052] MVL-1aneurysm) , and such that the material used to fill the cavity or lumen can be selectively cut by the surgeon once deployed into the dome of the aneurysm.

[0053] More broadly, the present invention comprises the provision and use of an implantable medical device that can fill substantially any void (i . e . , space) located within the body. The space to be filled can be a cavity resulting from trauma, disease, congenital defects, or post-surgical interventions . The space to be filled can be a normal or pathological physiological structure for which filling can lead to an intended therapeutic effect (conduit

[0054] f illing / occlusion versus cavity filling) . The filling of the space can be intended to restore structural integrity, support tissue regeneration, to deliver therapeutic agents in cases where tissue loss or damage has occurred or to obstruct a conduit . The filling of these cavities can be done by a non-invasive endovascular procedure such as a percutaneous procedure utilizing a small entry portal in a major artery, as will be apparent to one of skill in the art in view of the present disclosure . By way of example but not limitation, in a representative endoscopic procedure, a catheter or delivery needle can be inserted in the body through a minimally invasive procedure so as to allow accessing the cavity from outside the body.

[0055] MVL-1The present invention finds particular utility in treating vascular defects and or malformations (e . g. , peripheral, cranial aneurysm, fistulas, etc . ) . Some exemplary vascular defects are intracranial aneurysms and pathological saccular or fusiform dilations of intracranial arteries . Three different working principals have been generally described and are often applied in combination for effecting such treatment . A first approach generally comprises filling of the aneurysmal cavity (i . e . , packing) . A second approach generally comprises effecting flow diversion within the harbouring vessel . A third approach generally comprises effecting flow diversion within the aneurysm cavity. Each of the treatment approaches is generally achieved by applying coiling and / or stenting / f low diversion, where a catheter is guided through the blood vessel to deliver a coil and / or stent / flow diverter that can either fill the aneurysm sac or shield it from the blood flow thus preventing it from rupturing. See Fig. 1.

[0056] The present invention generally comprises a novel system and method for effecting flow redirection and / or cavity filling.

[0057] The present invention may be utilized to effect flow redirection in a manner similar to a flow diverter, i . e . , the present invention comprises a dense three-dimensional mesh which redirects blood flow, leading to increased stasis and thrombosis

[0058] MVL-1within the arterial or venous cavity, as will hereinafter be discussed in further detail . See Fig.

[0059] 1 .

[0060] The present invention may also be utilized to effect cavity filling, i . e . , progressive packing of the cavity which induces thrombosis, as will hereinafter be discussed in further detail . See Fig.

[0061] 1 .

[0062] Looking now at Figs . 2A-2C, the present invention comprises a system 5 configured to fill an aneurysm with a filling material 10.

[0063] More particularly, system 5 generally comprises a catheter (preferably a microcatheter 15) slidably disposed within a delivery catheter (e . g. , guiding catheter 20) , and a cutting catheter 70, as will hereinafter be discussed in further detail . In one form of the invention, system 5 also comprises a guidewire 22 and a balloon or stent catheter 23 which can be used to maintain blood flow through a body lumen during delivery of the monofilament into a body cavity or to provide therapy adjacent to the body cavity to be filled by filling material 10.

[0064] Filling material 10 preferably comprises a single filling element (e . g. , polymer (mono) filament) , to be differentiated from the plurality of coils used in prior art systems . Filling material 10 can be used to fill the aneurysm at different filling densities .

[0065] MVL-1Filling material 10 can be cut in situ at any given point thus allowing, for example :

[0066] (i) the forming of a 3-dimensional spherical mesh structure from the artery or cavity wall inwards;

[0067] (ii) the forming of a personalized flow diversion device (i . e . , specifically sized to the patient being treated) ;

[0068] (iii) the personalization of the filling density (i . e . , specific to the patient being treated) ;

[0069] (iv) a reduced intervention time;

[0070] (v) reduced exposure to radiation (e . g. , X-ray) ; (vi) reduced procedural cost; and

[0071] (vii) improved follow-up visibility by using polymeric material for filling the aneurysm in angiography, CT and MRI .

[0072] Looking now at Figs . 3-5, in one preferred embodiment of the present invention, filling material 10 comprises a polymer filament comprising any biocompatible material . Providing filling material 10 in the form of a polymer filament provides an advantage over other materials in that safely cutting the length intraoperatively is facilitated by the use of polymer filament, as will hereinafter be discussed in further detail .

[0073] Filling material 10 may be manufactured in various diameters and / or cross-sectional shapes to accommodate various target cavities . Filling material 10 may be extruded with different cross-sectional

[0074] MVL-1shapes and diameters for better filling or buckling during filling of the cavity, as will hereinafter be discussed in further detail . Filling material 10 may also comprise a composite material, e . g. , a multilumen extruded radio-opaque filler or coating. The extrusion process may also be used to give certain structural properties to filling material 10. By way of example but not limitation, the extrusion process may be used to control macro structural properties of filling material 10 such as dimensions, shape, size, etc . By way of further example but not limitation, the extrusion process may also be used to control micro structural properties of filling material 10 such as molecular orientation, polymer orientation, crystallinity, etc .

[0075] It should also be appreciated that, if desired, the distal end of filling material 10 may be preshaped, or softened, so as to not injure the aneurysm wall upon insertion into the aneurysm.

[0076] It should also be appreciated that, if desired, filling material 10 may be treated so as to assume a pre-determined "buckling" or "folding" profile (e . g. , cross-section, diameter, stiffness, thermal condition, etc . ) , whereby to optimize the filling of, and conformation to, the aneurysm geometry to enable the formation of a 3-dimensional spherical mesh structure from the artery or cavity wall inwards . Where filling material 10 comprises an extruded polymer, the filling

[0077] MVL-1material preferably comprises material selected from the group consisting of MRI-compat ible polymers, nonferromagnetic metal alloys, and other materials compatible with medical imaging e . g. , polypropylene (PP) , polyamide (PA) , polyvinylidene fluoride (PVDF) , polyethylene terephthalate (PET) , etc . See Figs . 3 and 4 .

[0078] Alternatively and / or additionally, if desired, filling material 10 may comprise a radio-opaque material or filling material 10 may comprise a radioopaque coating (e . g. , radio-opaque salts, Barium sulfate (BaSO4) , B1OCO3, Tungsten, Tantalum, etc . ) . Stated differently, if desired, filling material 10 may (i) be made entirely out of a radio-opaque material, (ii) be made out of a combination of a radio-opaque material and a non-radio-opaque material, or (iii) comprise a radio-opaque coating disposed over a non-radio-opaque material . See Fig. 5.

[0079] By way of further example but not limitation, in a preferred embodiment of the present invention, filling material 10 is configured to have the following properties :

[0080] (i) being stable or biodegradable;

[0081] (ii) having a diameter range of 0.010-0.500 mm; (iii) having shape memory effects to facilitate filling of the aneurysm;

[0082] (iv) being capable of gelling in situ or being thermally or light-set in situ;

[0083] MVL-1(v) having a surface texture or porosity for enhancing hemostasis and clotting;

[0084] (vi) having a straight, pre-shaped, curved, coiled, or oval shape;

[0085] (vii) having variable stiffness or variable diameter or variable macro and micro-structural (crystallinity orientation) properties; and

[0086] (viii) having pre-determined "buckling" or "folding" behavior for filling the aneurysm with a specific filling pattern (e . g. , outside to inside or outer part to inner part, inside to outside or inner part to outer part, top to bottom, etc . ) or a random filling pattern.

[0087] In one form of the present invention, filling material 10 may comprise a polymer monofilament (e . g. , a polymer endless monofilament) for use in treating intracranial aneurysms . By way of example but not limitation, filling material 10 comprises a material selected from the group consisting of MRI-compatible polymers, non-f erromagnetic metal alloys, and other materials compatible with medical imaging (e . g. , polypropylene (PP) , polyamide (PA) , polyvinylidene fluoride (PVDF) , polyethylene terephthalate (PET) , etc . ) . If desired, filling material 10 may also comprise a radio-opaque filler or filling material 10 may comprise a radio-opaque coating (e . g. , radioopaque salts, Barium sulfate (BaSCg) , BiOCO3, Tungsten, Tantalum, etc . ) .

[0088] MVL-1Looking back at Figs . 2A-C, microcatheter 15 generally comprises an elongated body 25 having a distal end 30, a proximal end 35, and a lumen 40 extending therebetween. Proximal end 35 of body 25 comprises a hub 45 having a loading device 50 connected or inserted thereto for facilitating movement of filling material 10 from loading device 50, through lumen 40 of microcatheter 15, and out distal end 30 of microcatheter 15, as will hereinafter be discussed in further detail .

[0089] In one form of the invention, system 5 comprises a guidewire 22 and a balloon or stent catheter 23 which can be used to maintain blood flow through a body lumen during delivery of filling material 10 into a body cavity or to provide therapy adjacent to the body cavity to be filled by filling material 10.

[0090] Preferably, guidewire 22 and balloon or stent catheter 23 are disposed within guiding catheter 20 and parallel to microcatheter 15, as can be seen in Figs .

[0091] 2A-2C. However, guidewire 22 and balloon or stent catheter 23 could be disposed within a body lumen external to guiding catheter 20.

[0092] In another form of the invention, guidewire 22 and balloon or stent catheter 23 are omitted from system 5. See, for example, Figs . 2D-2F.

[0093] Looking now at Figs . 6 and 7A-7C, loading device 50 is configured to allow precise feeding (i . e . , loading) of the filling material through microcatheter

[0094] MVL-115. Loading device 50 comprises a feeding mechanism 55 which is configured depending upon the type of filling material 10 that it will load. By way of example but not limitation, loading device 50 may comprise a catch-and-grab feature that allows grabbing filling material 10 and feeding it through the microcatheter 15. Loading device 50 may comprise a plurality of catching elements 60 comprising rotating wheels 65 (e . g. , rollers, knurls, etc . ) that can catch filling material 10 and feed it through lumen 40 of microcatheter 15. Catching element 60 can also be used to texture filling material 10 with indentation or barbs that allow filling material 10 to assume a pre-buckling pattern once the filament is inside the aneurysm (i . e . , released from the confinement of microcatheter 15) . See, for example, Fig. 32 which shows a uniform pattern of notches 125 formed along the entire length of filling material 10. Notches 125 are formed by catching element 60 as the filling material is spooled along the knurled wheel and advanced forward within lumen 40 of microcatheter 15.

[0095] Thus, loading device 50 comprises a gear mechanism which allows for :

[0096] (i) precise control over movement of filling material 10 and transfer of filling material 10 from loading device 50 through lumen 40 microcatheter 15 and into the aneurysm;

[0097] MVL-1(ii) accelerating or decelerating the movement and transfer of filling material 10 relative to microcatheter 15;

[0098] (iii) sufficient torgue to feed filling material 10 through lumen 40 of microcatheter 15 and into the aneurysm; and

[0099] (iv) catching elements 60 (e . g. , a knurled wheel) to grab and / or texture filling material 10 as it is fed through microcatheter 15, which texture can initiate buckling areas for filling element 10 when the filament is advanced into the aneurysm (e . g. , notches 125 provide areas along the filament for the filament to "buckle", e . g. , bend or fold after it has been released from lumen 40 of microcatheter 15) .

[0100] And it should be appreciated that loading device 50 may also comprise electrical controls for motorizing the gear mechanism so as to provide for automatic advancement of filling material into a body cavity.

[0101] If desired, loading device 50 may be configured as a fully manual loading device, a fully automated loading device or as a hybrid manual-automatic loading device . If loading device 50 is configured as a hybrid manual-automatic loading device, manual operation may be used for initial loading and positioning of filling material 10 through lumen 40 of microcatheter 15 and into the aneurysm, and automated operation may be used during at least one of

[0102] MVL-1repetitive advancement cycles, sensitive filling phases and / or conditions of increased resistance, where controlled and consistent actuation of the loading device is advantageous .

[0103] It will be appreciated that loading device 50 can be pre-filled with filling material 10 or loading device 50 can be assembled with another element (e . g. , a spool or a preformed knit having a three-dimensional mesh shape such as a ball) for storing filling material 10. Filling material 10 can be spooled on the loading device or on a spool device that can be loaded separately. If desired, filling material 10 may be formed from a shape memory material (e . g. , polymer, Nitinol) that is shape set (e . g. , heat set, creep set) in the form of a ball with smaller folds or loops of the material disposed in the center of the ball, such that the filling material can be configured into a straight configuration for delivery to an aneurysm and then re-formed into the ball once the filling material has been deployed into the aneurysm.

[0104] In order to fill the aneurysm, the distal end of the filling material 10 is passed from loading device 50, through lumen 40 of microcatheter 15. Filling material 10 is passed through lumen 40 of microcatheter 15 until it emerges out of distal end 30 of microcatheter 15 and enters the aneurysm (i . e . , the aneurysm sac) . In order to fill the aneurysm with filling material 10, loading device 50 continues to

[0105] MVL-1feed filling material 10 into the aneurysm (i . e . , the aneurysm sac) . As filling material 10 enters into the aneurysm it buckles (e . g. , folds or bends) along the perimeter of the aneurysm wall . The filling of the aneurysm sac is achieved by continuous buckling of the body of filling material 10 as it conforms itself to the geometry of the interior of the aneurysm to create a 3-dimensional spherical mesh structure . If desired, additional filling of the 3-dimensional spherical mesh might be achieved by further advancement of filling material 10 into the interior of the aneurysm. See, for example, Fig. 8 which shows filling material 10 being passed in the sac of representative aneurysm A, and Fig. 9 which shows an aneurysm sac completely filled with filling material 10.

[0106] To this end, if desired, filling material 10 may comprise a pig tail at the distal end of filling material 10 to guide the initial break into the desired location within the anatomy. Furthermore, filling material 10 may comprise a specific, predetermined spool or knit diameter to shape-set filling material 10 such that filling material 10 assumes the predetermined spool or knit diameter after it is deployed in the anatomy. It should be appreciated that the predetermined spool or knit diameter is preferably equal to (or larger than) the diameter of the cavity in the anatomy into which

[0107] MVL-1filling material 10 is inserted (e . g. , the aneurysm diameter) to ensure wall apposition.

[0108] Turning now to Figs . 22-31, Figs . 22-31 show system 5 being used to pass filling material 10 into a model aneurysm having a generally spherical shape such that filling material 10 assumes a generally spherical shape and fills the aneurysm from the interior surface of the tissue defining the aneurysm towards the center of the aneurysm. To achieve the generally spherical shape, filling material 10 may be configured to assume a three-dimensional geometry (e . g. , a sphere, a knit, etc . ) when filling material 10 is unrestrained prior to being fed into loading device 50 for deployment into the anatomy. Once filling material 10 has been deployed into the anatomy (e . g. , by being unloaded from loading device 50 and passed into the anatomy) , filling material 10 is preferably configured to assume its predetermined, unrestrained geometry within the anatomical space into which it is deployed (e . g. , in the dome of an aneurysm) . With this form of the invention, by pre-configuring filling material 10 so as to assume a three-dimensional (e . g. , spherical) geometry after being passed into the anatomy, it is possible to pass filling material 10 into an anatomical structure such that filling material 10 thereafter assumes a spherical geometry having a diameter equal to, or slightly greater than, the diameter of the anatomical structure into which it is

[0109] MVL-1passed (e . g. , a diameter greater than the sphere that defines an aneurysmal dome) . This results in filling material 10 being apposed against the surface of the wall defining the anatomical structure under the force of the resiliency of filling material 10.

[0110] In another form of the present invention, and looking now at Figs . 9A-9E, an alternative loading device is provided. The alternative loading device comprises a telescoping loading tool 150 that is configured for manual and / or automated cyclic advancement of filling material 10 through the lumen of a catheter .

[0111] More particularly, telescoping loading tool 150 comprises a proximal tube 155 and a distal tube 160. Proximal tube 155 comprises a gripping mechanism 165 for gripping filling material 10 to distally advance filling material 10 into lumen 40 of microcatheter 15. In Figs . 9A-9E, proximal tube 155 is shown as an outer shaft sliding over distal tube 160 (i . e . , an inner shaft) . However, proximal tube 155 could be configured to slide inside distal tube 160 (i . e . , proximal tube 155 could be configured as an inner shaft sliding inside of an outer shaft) .

[0112] In use, telescoping loading tool 150 may be used as follows to distally advance filling material 10.

[0113] With outer shaft 155 in a proximal position, gripping mechanism 165 is squeezed together to capture filling material 10 between at least one gripping

[0114] MVL-1interface of gripping mechanism 165. Outer shaft 155 is then advanced distally to advance filling material 10 within inner shaft 160. Gripping mechanism 165 is then released causing gripping mechanism 165 to release filling material 10 and outer shaft 155 is retracted proximally with respect to inner shaft 160. This cycle is then repeated, as necessary, to advance filling material into a body cavity.

[0115] Telescoping loading tool 150 provides the following advantages over loading device 50 and other prior art loading devices :

[0116] (i) the reduced risk of the filling material buckling proximal to entry into lumen 40 of microcatheter 15;

[0117] (ii) improved control of axial force transmission during loading of filling material into lumen 40 of microcatheter 15; and

[0118] (iii) enhanced procedural consistency, particularly through tortuous or high-resistance pathways .

[0119] If desired, telescoping loading tool 150 may be configured as a fully manual loading device, a fully automated loading device or as a hybrid manualautomatic loading device . If telescoping loading tool 150 is configured as a hybrid manual-automatic loading device, manual operation may be used for initial loading and positioning of filling material 10 through lumen 40 of microcatheter 15 and into the aneurysm,

[0120] MVL-1and automated operation may be used during at least one of repetitive advancement cycles, sensitive filling phases and / or conditions of increased resistance, where controlled and consistent actuation of the loading device is advantageous .

[0121] If desired, any combination of loading device 50 and telescoping loading tool 150 could used to load filling material 10 through lumen 40 of microcatheter 15.

[0122] Looking now at Figs . 10-14 , when the aneurysm is sufficiently filled with the desired density of filling material 10, filling material 10 is cut so as to release the portion of filling material 10 that has filled the aneurysm from the remainder of filling material 10 extending proximally towards loading device 50 through lumen 40 of microcatheter 15. In one embodiment of the invention, cutting of filling material 10 is effected via selective movement of a cutting catheter 70 that is disposed coaxially over microcatheter 15.

[0123] More particularly, cutting catheter 70 comprises a distal end 75, a proximal end 80, and a lumen 85 extending therebetween which is sized to slidably receive microcatheter 15. In a preferred embodiment of the invention, cutting catheter 70 (or at least a distal portion thereof) comprises a laser cut hypotube in order to provide sufficient column strength and flexibility to cutting catheter 70 to navigate the

[0124] MVL-1tortuous path of vasculature in the human anatomy, as will be appreciated by one of skill in the art in view of the present disclosure . Distal end 75 of cutting catheter 70 comprises a cutting tip 90 configured to catch and cut filling material 10. If desired, cutting catheter 70 may be provided with a radioopaque coating (e . g. , radio-opaque salts, Barium sulfate (BaSO4) , BiOCO3, Tungsten, Tantalum, etc . ) along a portion of its length.

[0125] In a preferred embodiment of the present invention, and looking now at Fig. 14, cutting tip 90 preferably comprises a grasping bill 95 comprising at least one resilient leaf 100, and preferably a plurality of resilient leaves 100. If desired, the shaft of cutting catheter 70 can be formed so as to have portions which are more flexible than other portions of the shaft . By way of example but not limitation, distal end 75 of the shaft of cutting catheter 70 can be formed to be highly flexible while the remainder of the shaft of cutting catheter 70 can be less flexible . See, for example, Fig. 11B which shows distal end 75 comprising a highly flexible portion 91 (which is similar to the design of a guidewire) disposed distally of a less flexible portion 92 (which comprises a laser cut hypotube) . In this way, cutting catheter 70 is provided with the flexibility needed to navigate the tortuous path of vasculature in the human anatomy while still providing

[0126] MVL-1sufficient column strength to support microcatheter 15 (and filling material 10) during delivery of filling material 10 into a body cavity.

[0127] Alternatively, if desired, and looking now at Fig. 12 cutting tip 90 may comprise a "cutting crown" 102 having a plurality of grasping prongs 103.

[0128] In a further embodiment of the present invention, and looking now at Figs . 13A-13D, cutting tip 90 may be formed out of a resilient shape memory alloy (e . g. , Nitinol) which is configured to "center and collapse" around filling material 10 as microcatheter 15 is retracted proximally relative to cutting catheter 70. In one form of the invention, as shown in Figs . 13A and 13B, cutting tip 90 comprises a spring finger 93 and a V-blade 94, wherein only spring finger 93 is formed out of a resilient shape memory alloy. In another form of the invention, as shown in Fig. 13C, spring finger 93 and V-blade 94 are both formed out of a resilient shape memory alloy. In this way, and looking at Fig. 13D, when filling material 10 and microcatheter 15 are disposed within lumen 85 of cutting catheter 70, and microcatheter 15 is pulled proximally through lumen 85 of cutting catheter 70 to expose filling material 10 (or cutting catheter 70 is pushed distally forward beyond distal end 30 of microcatheter 15) , distal end 75 of cutting catheter 75 centers and collapses around filling material 10.

[0129] MVL-1Looking now at Fig. 14, at least one cutting blade 105 comprising a V-shaped cutting slot 110 is mounted to cutting tip 90 which comprises a clam shell grasping bill 95. At least one transverse slot 115 is preferably formed in cutting tip 90 extending generally transverse to the plane defined by cutting blade 105, whereby to provide a hinge 120 where each resilient leave 100 mounts to cutting tip 90.

[0130] When microcatheter 15 is pulled proximally backwards through cutting catheter 70 to expose filling material 10 (or cutting catheter 70 is pushed distally forward beyond distal end 30 of microcatheter 15) , resilient leaves 100 clamp down onto filling material 10, whereby to allow cutting tip 90 to come into contact with, and latch onto, filling material 10. Filling material 10 is then cut by moving filling material 10 proximally (i . e . , reversing feeding mechanism 55 of loading device 50) while maintaining cutting catheter 70 in its position. After cutting filling material 10, cutting catheter 70, microcatheter 15 and any remaining filling material 10 disposed inside microcatheter 15 are removed from the vasculature .

[0131] Thus, it will be seen that cutting catheter 70 provides at least one of the following:

[0132] (i) a shaft having at least one portion that is highly flexible while still providing the necessary torque or column strength to support microcatheter 15

[0133] MVL-1and filling material 10 during delivery of filling material 10 into a body cavity and to support catheter 70 during the proximally-directed pulling of filling material 10 against cutting tip 90;

[0134] (ii) a cutting tip 90 for cutting the filling material using a cutting crown 102 or a V-shaped cutting slot 110 and cutting blade 105 (i . e . , a guillotine mechanism) ;

[0135] (iii) a clam shell grasping bill 95 configured for catching and grasping filling material 10, wherein the clam shell grasping bill may be formed from a shape memory Nitinol which can be configured to push the filling material against cutting blade 105 of cutting tip 90; and

[0136] (iv) a cutting mechanism which can be activated in situ.

[0137] In use, and looking now at Figs . 15-21, system 5 is generally deployed in the human body as follows .

[0138] First, guiding catheter 20 is inserted into an artery (e . g. , the cervical artery) and advanced distally so as to allow intraluminal access from outside the body. If it is desired to use a guidewire and balloon or stent catheter to maintain blood flow through guiding catheter 20 during deployment of filling material into a body cavity or to provide therapy adjacent to the body cavity to be filled by filling material 10, guidewire 22 may be inserted into guiding catheter 20 and advanced distally until the

[0139] MVL-1distal tip of the guidewire is disposed adjacent the aneurysm. Cutting catheter 70, having microcatheter 15 disposed in lumen 85 of cutting catheter 70, is mounted on a guidewire (e . g. , disposed over a guidewire) inserted into guiding catheter 20, adjacent to guidewire 22 (i . e . , alongside guidewire 22) and positioned such that distal end 30 of microcatheter 15 is disposed just outside the base of the aneurysm to be filled with filling material 10.

[0140] Microcatheter 15 is then advanced distally until distal end 30 of microcatheter 15 is positioned in the aneurysmal sac (Fig. 15) . The guidewire is then withdrawn from the microcatheter lumen (i . e . , proximally) . Since microcatheter 15 is disposed within cutting tip 90, resilient leaves 100 of clam shell grasping bill 95 are radially expanded to accommodate microcatheter 15 (and filling material 10) through cutting tip 90.

[0141] Next, loading device 50 (or telescoping loading tool 150) is actuated in order to feed filling material 10 distally through lumen 40 of microcatheter 15 and into the aneurysm (i . e . , into the aneurysmal sac) (Figs . 16-20) . When the aneurysmal sac is sufficiently filled with filling material 10 (i . e . , so as to achieve the desired mesh structure and density) , microcatheter 15 is pulled proximally through lumen 85 of cutting catheter 70. As distal end 30 of microcatheter 15 is pulled proximally through distal

[0142] MVL-1end 75 of cutting catheter 70, resilient leaves 100 of clam shell grasping bill 95 contract to clamp down on filling material 10. Filling material 10 is then moved proximally, e . g. , by manually retracting filling material 10, reversing feeding mechanism 55 (or telescoping loading tool 150) , such that filling material 10 passes into V-shaped cutting slot 110 and into contact with cutting blade 105, whereby filling material 10 is cut by cutting blade 105 at the base of the aneurysm (Fig. 21) .

[0143] Thus, system 5 allows the surgeon to cut (or release) filling material 10 in situ (i . e . , cutting can be done inside the vessel at the base of the aneurysm with cutting blade 105 of cutting catheter 70) or, alternatively, cutting can be done outside of the body with the remainder of the filling material fed into the aneurysm (or within the vascular cavity, e . g. , within a venous pouch) .

[0144] In one exemplary method, novel system 5 may be used for treating a dural arteriovenous fistula or malformations . When novel system 5 is used to treat dural arteriovenous fistula or malformations, filling material 10 is fed through microcatheter 15 and into the fistula or malformation (venous or arterial) . The fistula or malformation can be filled randomly or orderly with filling material 10 and then filling material 10 can be cut in situ using cutting catheter 70. After the filling material 10 is cut,

[0145] MVL-1microcatheter 15, cutting catheter 70 and guiding catheter 20 are removed from the cerebral vasculature .

[0146] In another exemplary method, novel system 5 may be used for occluding a parent artery. When novel system 5 is used to occlude a parent artery, filling material 10 is fed through microcatheter 15 and into the occlusion. The occlusion can be filled randomly or orderly with filling material 10 and then filling material 10 can be cut in situ using cutting catheter 70. After the filling material 10 is cut, microcatheter 15, cutting catheter 70 and guiding catheter 20 are removed from the cerebral vasculature .

[0147] It will be appreciated that the present invention makes several significant improvements over the systems and methods of the prior art .

[0148] By way of example but not limitation, the invention utilizes a flexible buckling filament (i . e . , filling material 10) that allows the in situ building of a structured multi-layered (e . g. , spherical) meshlike scaffold (i . e . , a three dimensional structure) inside a cavity of the human body, from the outside inwards (e . g. , from the outermost surface of a spherical pocket (e . g. , an aneurysm) towards the center of the spherical pocket . The human body may have different normal or pathological cavities (the geometry and size of which cavities differ between patients) . Scaffolding these cavities helps to promote and restore structural integrity (e . g. , to the

[0149] MVL-1weakened blood vessel) , support tissue regeneration (e . g. endothelialisation) , to deliver therapeutic agents in cases where tissue loss or damage has occurred, or limit exposure of such a cavity to physiological elements that can promote detrimental effects or pathological tissue development in the cavity. One particular example of such a cavity is a vascular aneurysm. The scaffolding of the cavity is achieved by utilizing filling material 10, a single continuous element that adapts to the cavity geometry and dimensions through buckling. As discussed above, filling material 10 can comprise a monofilament that conforms to the dimensions of the cavity as it is being introduced in the cavity. The conformation to the cavity is achieved through a "buckling" behavior that allows filling material 10 to buckle, whereby to adapt to the shape of the cavity it is scaffolding. It should be appreciated that this is different from prior art systems and methods relying on coiling, which systems and methods utilize filling devices (coils) that do not buckle, but instead self-fold on themselves from shape memory, filled from inside outwards . Furthermore, with such coil-based prior art systems and methods, the filling is quite random and not an ordered structure, in contradiction to the ordered, planned buckling of filling material 10 with the present invention. The buckling behavior of filling material 10 results from a combination of

[0150] MVL-1resistance of the cavity (i . e . , the force applied to filling material 10 by the inside surface of the cavity wall) , compression force applied to the filament (e . g. , torque or pushing force by loading device 50) and the properties of filling material 10, which properties can be adjusted to adapt the buckling behavior . Typically, the surgeon chooses a filling material 10 having specific properties that allow it to buckle as it is being introduced in the cavity of a specific dimension. The properties of filling material 10 can be tailored by selecting for the composition (i . e . , material) of filling material 10, the diameter of filling material 10, etc. By way of example but not limitation, filling material 10 may comprise a polymer or a composite of polymer with another material . The buckling behavior of filling material 10 can be adjusted by controlling for the orientation of the polymer macromolecules in the filling material, the structural profile of the macromolecules making up the filling material, the crystallinity of the filling material, the composition of the polymer of which the filling material is made, etc.

[0151] Alternatively, the surgeon can also selectively tailor a buckling profile for filling material 10 during feeding of the filling material through microcatheter 15 with loading device 50.

[0152] To this end, it should be noted that loading device 50 can produce indentations or micro-defects

[0153] MVL-1that are introduced or imprinted on filling material 10 during loading of filling material 10 into the cavity. See, for example, notches 125 shown in Fig.

[0154] 32. The buckling profile can also be tailored with the torque (or compression force) that is used to introduce filling material 10 into the cavity by loading device 50. Alternatively, or additionally, the buckling profile can be tailored by providing microcatheter 15 such that lumen 40 is sized to have sufficient column strength to avoid buckling of the filling material within lumen 40 of microcatheter 15 and allow buckling only as filling material 10 exits distal end 30 of microcatheter 15 inside the body cavity (e . g. , aneurysm) .

[0155] As filling material 10 is introduced into the body cavity, filling material 10 will encounter resistance (e . g. , from contacting the interior side wall of the body cavity) that will oppose to the continuous filling of the non-buckled filling material 10 into the cavity. To allow continuous filling, filling material 10 is configured to buckle and fold (e . g. , form a loop of material which bends around and crosses itself ) that conforms to the dimensions of the cavity defined by the cavity walls . The buckling behavior allows the creation of multiple folds (e . g. , loops) of filling material 10 within the cavity with each fold or loop conforming to the dimension of the cavity it is buckling inside of . As multiple folds or

[0156] MVL-1loops of filling material 10 form by continuous feeding of the filling material 10 into the cavity, a three-dimensional mesh-like structure is formed that scaffolds the cavity (taking on the shape of the cavity itself by forming a first layer against the wall of the cavity and building multiple layers towards the inside of the cavity) .

[0157] Typically, after an initial number of folds or loops of filling material 10 have been formed within the cavity, filling material 10 will start buckling against the surface of the first and successive layer of folds or loops, allowing a succession of multiple layers of folds or loops to form from the buckling filling material . The mesh-like scaffold will grow through the superposition of multiple folds or loops of filling material 10 creating multiple layers of the buckling filling material inside the cavity and at the aneurysmal neck, leading to a flow diverter-like effect on blood flow. The density of the mesh-like structure is a function of the number of folds or loops of filling material 10 that comprise the scaffold. The building of the scaffold of filling material 10 grows from the outside to the inside of the cavity. As the cavity is being filled by the multiple successive folds or loops of filling material 10, the folds or loops will generally become smaller and smaller ( from the outside of the cavity to the inside of the cavity) . The buckling profile can be

[0158] MVL-1varied along the length of filling material 10 or adapted to allow filling material 10 to buckle continuously as it is being fed inside the cavity, which cavity grows smaller as the loops continue to form and stack on top of one another . When the desired density of mesh-like scaffold is achieved, filling material 10 can be cut .

[0159] When the desired density is achieved from the successive folds or loops of the buckling of filling material 10 within the cavity that is to be filled, the filling material is cut so as to release the portion of the filling that has filled the cavity (e . g. , the aneurysm) from the remainder of the filling material . A scaffold formed from a single, i . e . , continuous buckled filling material 10 remains in the cavity. As discussed above, in one embodiment of the invention, cutting is achieved with cutting catheter 70 positioned over microcatheter 15. Cutting catheter 70 comprises cutting tip 90 that facilitates catching and cutting filling material 10 in the manner discussed above (i . e . , with a shape memory metal) . Cutting tip 90 is activated by pulling microcatheter 15 proximally (i . e . , backwards) through cutting catheter 70, or by pushing cutting catheter 70 distally (i . e . , forward) , thereby allowing cutting tip 90 to come into contact with, and latch onto, filling material 10 (e . g. , via the aforementioned shape memory of cutting tip 90) . With this construction, the

[0160] MVL-1actuation mechanism (i . e . , the cutting of filling material) is performed by moving filling material 10 proximally (i . e . , backwards) through V-shaped cutting slot and onto cutting blade 105. In contrast to prior art devices, no actuation device, and importantly, no heat, is needed to perform the cutting of filling material 10.

[0161] More particularly, to actuate the cutting of filling material 10, filling material 10 is pulled proximally (i . e . , backwards) e . g. , by reversing feeding mechanism 55 of loading device 50 (or telescoping loading tool 150) while maintaining cutting catheter 70 in position relative to microcatheter 15. Cutting tip 90 has sufficient column strength to resist buckling of cutting catheter 70 during the proximally-directed pulling of filling material 10. This allows the cutting of filling material 10 in site . Cutting catheter 70, microcatheter 15 and any filling material 10 remaining inside lumen 40 of microcatheter 15 is then retracted proximally out of the vasculature .

[0162] As a result, in the case of a scaffold of filling material 10 formed inside the cavity of an aneurysm, the tailored scaffold formed from the single filament (i . e . , filling material 10) buckled at the neck of the aneurysm will act to divert the flow (e . g. , of blood) away from the neck / entrance of the aneurysm, promote thrombosis in the cavity and also allow for cells to

[0163] MVL-1colonize the scaffold formed out of filling material 10 to regenerate tissue inside the aneurysm.

[0164] Modifications

[0165] It should be understood that many additional changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the present invention, may be made by those skilled in the art while still remaining within the principles and scope of the invention.

[0166] MVL-1

Claims

What Is Claimed Is :

1. A system for forming an occlusive structure within a vascular cavity, the system comprising:a filament delivery assembly configured to advance a filament through a microcatheter into the vascular cavity;a cutting assembly disposed coaxially relative to the microcatheter, the cutting assembly comprising:(i) a gripping mechanism comprising a resilient element configured to radially engage the filament; and(ii) a cutting element positioned proximal to the gripping mechanism;wherein the system is configured such that :(a) withdrawal of the microcatheter relative to the cutting assembly causes the gripping mechanism of the cutting assembly to engage the filament; and (b) proximal movement of the filament relative to the cutting element tensions the filament against the cutting element to sever the filament .

2. The system of claim 1, wherein the filament delivery assembly comprises a spooling assembly.

3. The system of claim 1, wherein the filament delivery assembly comprises a telescoping assembly.

4. The system of claim 1, wherein the gripping mechanism comprises a plurality of resilient elements .

5. The system of claim 1, wherein the gripping mechanism comprises a crown of resilient leaf elements .

6. The system of claim 1, wherein the cutting element comprises a V-shaped slot .

7. The system of claim 1, wherein severing the filament occurs distal to a distal end of the microcatheter .

8. The system of claim 1, wherein the filament is configured to transition between:(i) a substantially linear configuration for delivery to the vascular cavity; and(ii) an occluding configuration that forms the occlusive structure upon advancement of the filament into the vascular cavity.

9. The system of claim 8, wherein the filament delivery assembly is configured to modify at least one mechanical property of the filament during advancement of the filament, wherein modifying the filament influences the transition of the filament into the occluding configuration.

10. The system of claim 9, wherein the filament delivery assembly is configured to introduce localized variations in stiffness along the filament .

11. The system of claim 9, wherein the filament delivery assembly is configured to form surface indentations along the filament .

12. The system of claim 9, wherein the filament delivery assembly is configured to modify the filament during advancement to introduce localized variations that define formation of the occlusive structure .

13. The system of claim 8, wherein formation of the occlusive structure is influenced by at least one of (i) compressive loading applied to the filament during advancement of the filament into the vascular cavity, and (ii) resistance from the vascular cavity.

14. The system of claim 1, further comprising a cartridge containing the filament .

15. The system of claim 1, wherein the microcatheter is dimensioned to laterally constrain the filament within the microcatheter .MVL-116. The system of claim 8, wherein advancement of the filament into the vascular cavity causes the filament to deform into a plurality of apposing folds of the filament along a boundary of the vascular cavity, whereby to conform to dimensions of the vascular cavity, and further wherein continued advancement of the filament into the vascular cavity forms concentric layers accumulating from the boundary of the vascular cavity toward a center of the vascular cavity.

17. The system of claim 16 wherein the plurality of apposing folds comprise apposing loops of the filament .

18. Apparatus for positioning within a vascular cavity for occluding the vascular cavity, the apparatus comprising:a filament configurable between:(i) a substantially linear configuration for delivery to the vascular cavity; and(ii) an occluding configuration that forms an occluding structure upon advancement of the filament into the vascular cavity;wherein advancement of the filament into the vascular cavity causes the filament to deform into a plurality of apposing folds of the filament along a boundary of the vascular cavity, whereby to conform toMVL-1dimensions of the vascular cavity, and further wherein continued advancement of the filament into the vascular cavity forms concentric layers accumulating from the boundary of the vascular cavity toward a center of the vascular cavity.

19. The apparatus of claim 18, wherein formation of the occlusive structure is influenced by at least one of (i) compressive loading applied to the filament during advancement of the filament into the vascular cavity, and (ii) resistance from the vascular cavity.

20. The apparatus of claim 18, wherein formation of concentric layers increases confinement of the filament within the vascular cavity and modifies subsequent deformation of the filament within the vascular cavity.

21. The apparatus of claim 18, wherein mechanical properties of the filament are defined by material characteristics .

22. The apparatus of claim 21, wherein the material characteristics include microstructural features uniformly distributed along the filament that influence the formation of the folds of the filament into the occluding configuration.MVL-123. The apparatus of claim 21, wherein the material characteristics comprise polymer chain orientation .

24. The apparatus of claim 21, wherein the filament comprises a radio-opaque material .

25. A method for forming an occlusive structure within a vascular cavity, the method comprising:advancing a filament through a microcatheter into the vascular cavity to form the occlusive structure within the vascular cavity;withdrawing the microcatheter relative to a coaxial cutting assembly to engage the filament with a gripping mechanism;applying tension to the filament to move the filament against a cutting element; andsevering the filament against the cutting element .

26. The method of claim 25, wherein forming the occlusive structure within the vascular cavity comprises advancing the filament into the vascular cavity to cause the filament to deform into a plurality of apposing folds of the filament along a boundary of the vascular cavity, whereby to conform to dimensions of the vascular cavity, and further wherein continued advancement of the filament into theMVL-1vascular cavity further folds the filament into concentric layers accumulating from the boundary of the vascular cavity toward a center of the vascular cavity.

27. The method of claim 25, wherein advancing the filament comprises pushing the filament into the vascular cavity.MVL-1

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