Patent Application
20160220265
1. Field of the Invention
The present invention pertains to intravascular medical devices. More particularly, the present invention pertains to devices for isolating, capturing, and removing blood clots from a blood vessel, while protecting against any distal embolization of clot fragments. This same system may also be used to safely and effectively retrieve obstructions, such as coils, balloons, or catheter fragments dislodged during interventional procedures, from the blood stream. The same system may further be used to remove obstructions from ducts and other cavities of the body, such as, for example, foreign bodies or stones from the urinary or the biliary tracts.
2. Background of the Art
The present invention pertains generally to thrombus collection and removal. The process of thrombosis may produce a clot in a patient's vasculature. Such clots may occasionally be harmlessly dissolved in the blood stream. At other times, however, such clots may lodge in a blood vessel or embolize to a downstream tissue or organ where they can partially or completely occlude the flow of blood. If the partially or completely occluded vessel provides blood to sensitive tissue such as the brain or heart, for example, serious tissue damage may result. Stroke, heart attack, deep vein thrombosis and pulmonary embolism are well-known examples of functional impairment associated with vascular thrombosis.
Deep vein thrombosis (DVT) can result from a clot that forms in one of the large veins of the leg leading to venous hypertension and inflammation. The longer the occlusion remains, the more risk of damaging the valves of the vein that normally stop blood from flowing backwards. A confluence of symptoms comprised of chronic pain, swelling, skin ulcerations and pain can develop that can markedly reduce the quality of life. A rapid, direct method to remove clots in the leg, with minimal lytic drugs, is needed to treat DVT patients. Catheter-based thrombectomy devices may answer this need, but most current clot removal devices still require the use of lytics as an integral part of the procedure.
Pulmonary embolism (PE) is a serious complication that can arise in DVT patients when a piece of clot breaks off in the leg and travels through the right heart to the lung, where it blocks the pulmonary artery, or one of its branches. If the clot is large, patients may experience shortness of breath, chest pain, low blood pressure, and even death. PE is the single most common cause of preventable hospital mortality, and the most frequent cause of death associated with childbirth. There is currently no good treatment modality for PE. Dissolving clot using a lytic drug may be used, but it may be too slow for some patients. Surgical removal of the clot is not commonly performed. A catheter-based system that removes the clot from the blocked vessel with immediate restoration of blood flow would be highly desirable.
Stroke can result from an acute reduction of blood flow to a region of the brain. About 85% of strokes are ischemic, wherein a blood clot in an artery of the brain interrupts blood flow, resulting in death or injury of brain cells. Depending on where the clot forms, the resulting dysfunction of the brain can lead to physical or mental disabilities, or even death. When symptoms of stroke are observed, immediate intervention is required to minimize tissue damage. For the past two decades, the favored approach has been to treat a stroke patient with clot dissolving lytic drugs, such as recombinant tissue plasminogen activator, streptokinase, or heparin. However, these drug do not immediately dissolve the blood clot and generally are useful only when administered within a short time period after onset of stroke symptoms.
Mechanical thrombectomy devices that function as removeable stents (“stentrievers”) have recently been used for ischemic stroke. Some reports indicates that stentrievers have removed clot within minutes suggesting the possibility of a new standard of care for selected stroke patients. Other reports point out, however, that stentriever devices are unable to open 25-30% of blocked vessels in the brain.
A rapid, direct method to remove clots, with minimal lytic drugs, is much needed. Most current thrombectomy devices still use some combination of clot fragmentation and aspiration with lytics.
Published U.S. Patent Application 2005/0038447 describes A medical device for removing clots from a blood vessel, comprising: a first longitudinally-oriented spine having a distal end; a pushing member coupled to the proximal end of the first longitudinally-oriented spine and extending proximally therefrom; and a clot-grabbing basket generally disposed between and coupled to the first longitudinally-oriented spine.
Published U.S. Patent Application 2004/0138692 discloses an embolus extractor, comprising: an elongated shaft having a proximal end and a distal end; first and second struts, each strut having a proximal end and a distal end coupled to the distal end of the shaft; the first and second struts having a first position and a second position, wherein in the first position, the distal ends and the proximal ends of the struts are spaced at a first distance, and in the second position the distal ends and the proximal ends of the struts are spaced at a second distance, the second distance being less than the first distance; and third and fourth struts, each strut coupled to one of the first and second struts via a proximal end and distal end.
Published U.S. Patent Application 2004/0098023 discloses a vasoocclusive device, comprising: a core member; and a fibrous structure carried by the core member, the fibrous structure comprises one or more strands of nanofibers. The vasoocclusive device may provide the fibrous structure in a product generated at least in part by an electrospinning process comprises the steps of: supplying a polymer solution through a needle; electrostatically charging the needle; electrostatically charging a metal plate that is placed at a distance from the needle, the metal plate having a charge that is opposite that of the needle, thereby sending a jet of the polymer solution towards the metal plate; and collecting the fibrous structure from the metal plate.
Published U.S. Patent Application 2004/0039435 discloses a self-expanding, pseudo-braided device embodying a high expansion ratio and flexibility as well as comformability and improved radial force. The pseudo-braided device is particularly suited for advancement through and deployment within highly tortuous and very distal vasculature. Various forms of the pseudo-braided device are adapted for the repair of aneurysms and stenoses as well as for use in thrombectomies and embolic protection therapy. There are a variety of ways of discharging shaped coils and linear coils into a body cavity.
Other ways to release the coil at a specifically chosen time and site are disclosed in U.S. Pat. No. 5,354,295 and its parent, U.S. Pat. No. 5,122,136, both to Guglielmi et al., describe an electrolytically detachable embolic device. A variety of mechanically detachable devices are also known. Various examples of these devices are described in U.S. Pat. No. 5,234,437, to Sepetka, U.S. Pat. No. 5,250,071 to Palermo, U.S. Pat. No. 5,261,916, to Engelson, U.S. Pat. No. 5,304,195, to Twyford et al., U.S. Pat. No. 5,312,415, to Palermo, and U.S. Pat. No. 5,350,397, to Palermo et al. Various configurations have been used to remove calculi from the biliary or urinary system. See, for instance, U.S. Pat. No. 5,064,428. Additionally, devices having various configurations have been used to remove objects from the vasculature. For example, surgical devices comprising one or more expandable and collapsible baskets have been described for removing or piercing a thrombus in the vasculature. See, U.S. Pat. No. 6,066,149. U.S. Pat. No. 5,868,754 describes a three prong-shaped device for capturing and removing bodies or articles from within a vessel. U.S. Pat. Nos. 5,895,398 and 6,436,112 to Wensel disclose a clot and foreign body removal device comprising a clot capture coil connected to an insertion mandrel within a catheter. The clot capture coil disclosed by Wensel is made out of a material with shape memory which allows it to be deformed within the catheter and then reformed to its original coil configuration when the coil is moved outside of the catheter lumen. The Wensel invention also provides for a biphasic coil which changes shape upon heating or passing an electric 25 current, wherein the coil can be used to ensnare and corkscrew a clot in a vessel, which is then extracted from the vessel by moving the clot capture coil and catheter proximally until the clot can be removed. According to the Wensel invention, foreign bodies are similarly captured by deploying the coil distal to the foreign body and moving the clot capture coil proximally until the foreign body is trapped within the coil Published U.S. Patent Application 2004/0225229 describes a device comprising a core wire having a distal end and a proximal end; a catheter shaft having a proximal catheter end, a distal catheter end and a lumen through which the core wire is passed such that the distal end of the core wire extends beyond the distal catheter end; a retrieval element disposed at the distal end of the core wire, the retrieval element movable from a radially contracted position to a radially expanded position; and a first stop element attached to the core wire, the first stop element configured to prevent over-expansion of the retrieval element. Among commercial thrombus-removal systems are at least the following: 1) The MERCI system of Concentric Medical that has a form of a corkscrew or helix spring. In this system, which may use a large 0.018 French microcatheter, the microcatheter tip is first positioned across the thrombus with the help of a guidewire after which the guidewire is exchanged with the system which is deployed distal and into the thrombus. The corkscrew shape of the device facilitates penetration into the thrombus. The thrombus can then be retrieved from the artery into a large 9 French guiding catheter, and removed from the patient's body. 2) The In-Time system of Boston Scientific resembles a clam-shell when compressed, but once the microcatheter is placed through the thrombus and the device extended out of the microcatheter, it expands into 4 strings that form an oval, as with a rugby football. The system is then pulled back to engage and remove the thrombus from the blood vessel. This is similar to the disclosed structure in Published US Application 2004/0138692. 3) Another system, known in the trade as a “lasso” is basically a simple catheter with a wire attached to its end. The wire makes a loop and enters back into the catheter (e.g., a large 0.018 French microcatheter). The operator changes the aspect of the loop by pulling on the wire. This system was originally conceived to catch foreign bodies. 4) The Catch system of Balt is a stent closed on one end forming a basket that is deployed distal to the thrombus. The operator then pulls the system and retrieves the thrombus. This is similar to the structure in FIG. 7 of U.S. Pat. No. 6,805,684. Although several of the commercial systems are designed to penetrate clot, this may in fact be impossible if the clot is made up of firm fibrin. The device may therefore not penetrate the clot but instead will slide over the thrombus. The process of engagement and retraction of a thrombus may also fractionate the clot, producing distal embolization.
In order to reduce complications arising from catheter-based procedures to remove blood clots, a number of devices have been developed to enable physicians to place devices that function as filters distal to the blood clot undergoing retraction to minimize downstream embolization of clot fragments.
U.S. Pat. No. 4,619,246 to Molgaard-Nielsen et al. discloses a collapsible filter basket. The basket includes a woven mesh but does not operate on a guide wire.
U.S. Pat. No. 4,723,549 to Wholey et al. discloses a filter which is expanded based upon inflation of a balloon acting as a donut mounted to expanding frame members of the filter disposed about the guide wire.
U.S. Pat. No. 5,053,008 to Bajaj discloses a filter which is expanded based upon inflation of a tubular balloon.
U.S. Pat. No. 5,108,419 to Reger et al. discloses a filter for capturing particles of plaque which includes a laterally collapsible bag with a plurality of longitudinally displaced filter cones. The bag has a draw-string about its mouth which opens and closes the bag both laterally and longitudinally.
U.S. Pat. No. 5,549,626 to Miller et al. discloses a filter deployed from the inside of a hollow tube by axial movement of an inner catheter. The filter is a mesh-like collapsible basket made of radially expandable materials which can be compressed in the lumen of an outer catheter and radially expand when the basket extends beyond the distal end of the catheter.
U.S. Pat. No. 5,695,519 to Summers et al. discloses a wire, which controllably moves forwards and sideways to open and close a generally conical filter by acting on the filter's mouth.
U.S. Pat. No. 5,810,874 to Lefebvre discloses a filter including strips that are radially opened by moving an inboard ring towards an outboard ring. The filter can be detached from the guide wire.
U.S. Pat. No. 5,814,064 to Daniel et al. discloses a filter system which utilizes various types of inflatable ribs, tubes or struts and a second filter system wherein the filter material is deployed by longitudinal movement of a push-pull wire relative to a generally static distal end of a tube.
U.S. Pat. No. 5,911,734 to Tsugita et al. discloses a conical mesh filter with a proximal end strut structure connected to the distal end of a guide wire. When the distal end of the slit outer sleeve is pulled proximally, the slitted region buckles radially outward to provide an egg beater filter. The expanded cage can be draped with filter mesh.
PCT Published Patent Application WO 96/01591 discloses a concave filter deployed by axially shortening the distance between the filter mouth and the filter apex (attached to a distal end of a guide wire). The filter mouth is sprung open by tethers fixed at one end to a static tube. A rod extends through the filter to its apex. The filter opens based upon the relative position of the filter apex on the rod and the static tube.
The above systems have various practical disadvantages. Currently available systems can also be difficult to guide or deploy at the site of the thrombus, or may be traumatic to the blood vessel, and some systems are quite expensive. In addition, most of these systems have large diameter profiles not which effectively prevents their deployment in small caliber blood vessels. All references cited herein are incorporate by reference in their entirety for the content of their disclosure.
A device capable of isolating, capturing, and facilitating the removal of a thrombus in blood vessels (or stones in biliary or urinary ducts, or foreign bodies) uses a soft coil mesh with the aid of a pull wire to engage the surface of a thrombus, and remove the captured thrombus. The mechanical thrombectomy device is positioned by MRI or angiography guided percutaneous transluminal catheter delivery within the lumen of the blood vessel directly adjacent to the thrombus. The soft coil mesh is formed by an elongated microcoil element that forms the helical elements of a macrocoil element having an adjustable stiffness which provides reliable dynamic compliance matching with the viscoelastic properties of the thrombus undergoing removal. The microcoil elements further provide a relatively elastic effect to the helical element forming the macrocoil that allows for control of gripping forces on the thrombus while reducing non-rigid circumferential contact of the device with vessel endoluminal surfaces. The use of multiple coil mesh elements, delivered through a single lumen or multiple lumen catheters, preferably with separate control of at least one end of each coil, provides a firm grasp on a distal side of a thrombus, facilitating non-disruptive or minimally disruptive removal of the thrombus upon withdrawal of the device. One aspect of the present invention is to provide a mechanical thrombectomy system that can reliably and safely navigate tortuous blood vessels to the site of an intracranial or extracranial thrombus. A second aspect of the present invention is to provide a mechanical thrombectomy device that can reliably and securely entrap a soft or hard thrombus without fragmenting the thrombus or damaging the intima of the blood vessel. A third aspect of this invention is to provide a mechanical thrombectomy device that is biocompatible, visible on both X-ray and MR imaging, and compatible with standard medical catheters. A further aspect of this invention is to provide a mechanical thrombectomy device that can safely and completely remove thrombus of any density from any blood vessel in the human body.
A still further aspect of the invention is the provision of a single macrocoil that may be displaced from a carrier on the distal and proximal sides of a thrombus to engage the thrombus from the distal and proximal sides, respectively. Another further aspect of the invention is the provision of multiple macrocoils that may be separately displaced from a carrier on the proximal and the distal sides of the thrombus to engage the thrombus from the proximal and distal sides, respectively. Another further aspect of the invention is the provision of a macrocoil that may be displaced from a carrier on the distal side of a thrombus and a separate thrombus support that may be positioned the proximal side of the thrombus to engage the thrombus from both the distal and proximal sides. A still further aspect of the present invention is the provision of eyelets that may be displaced on the distal side of the thrombus to facilitate engagement of the thrombus using the macrocoil. Another object of the present invention is to provide a controllably deployed entrapping mesh for capturing clotted blood in a blood vessel. A still further object of this invention is to provide for a distal dilatation braid or net mounted on a guidewire that is movably disposed in a delivery catheter.
The following description should be read with reference to the drawings wherein like reference numerals indicate like elements throughout the several views. The detailed description and drawings illustrate example non-limiting specific embodiments of the generic claimed invention.
For a number of reasons, it may be desirable to capture and/or remove clots from the vasculature. The blood vessel can be essentially any vessel or even a duct of the urinary or biliary tracts. The device may include two or more longitudinal wires, for example a guidewire, a push wire and a pull wire, as well as other functional wires (e.g., conductive wires for other features provided with the device, such as a resistive wire to enable heating of the coils, if conductive/resistive.
The basket member or region of soft coils is attached to or otherwise coupled with the wires. In general, the device (wires and soft coil material) can be advanced through the vasculature to a suitable location, for example past or adjacent to a clot, and expanded (when past or adjacent to the clot), so that the clot may be captured in the soft coils, upon operator action, and the captured clot can be removed from the vasculature. The device may be configured to shift between a first generally collapsed configuration and a second generally expanded configuration, especially by the elastic memory of the coil material, and the guidance imposed by the at least two wires. In at least some embodiments, shifting between these configurations includes the longitudinal movement of one or both of the wires relative to one another. Movement of the wires may occur in either the proximal or distal direction and, in the case of both wires moving, may be in the same or opposite directions. Shifting may also result in one or both of the wires moving somewhat laterally (especially with distally controlled wires on the coil material (e.g., with materials that bend when heated, or the like, and a heating element attached thereto) so that the wires become closer or move apart from one another. Shifting between the collapsed and expanded configurations may occur in a number of differing manners. For example, the device or portions thereof may be made of a shape memory material (such as nickel-titanium alloy or oriented coils) that can assume a predefined shape when unconstrained or when subjected to particular thermal conditions. According to this embodiment, the device can be manufactured to be “self-expanding” (when the longitudinal distension and restraint by the wires is removed) so that it can be delivered in a collapsed configuration, then shift to the expanded configuration when a constraint is removed (e.g., the distal ends of the two wires brought closer together) or when the device is subject to the natural thermal conditions within the blood vessel. Alternatively, shifting may occur by mechanically moving one or both of wires. Moving the wires may occur in a number of different ways such as by moving one or other of the wires attached to the distal or proximal end of the coil material on the device.
As described above, all or portions of the device (including but not limited to the coil materials and the wires) may be manufactured from polymeric, metallic, natural (e.g., gut wires), synthetic, or composite materials. Preferred materials tend to be polymeric, metallic, composite or mixtures or combinations of these materials. A conventional medical structural material such as nickel titanium alloy may be employed. However, any suitable material may be used including metals, metal alloys, polymers, etc. Some examples of suitable metals and metal alloys include stainless steel, such as 304V, 304L, and 316L stainless steel; linearelastic or super-elastic nitinol or other nickel-titanium alloys, nickel-chromium alloy, nickelchromium-iron alloy, cobalt alloy, tungsten or tungsten alloys, MP35-N (having a composition of about 35% Ni, 35% Co, 20% Cr, 9.75% Mo, a maximum 1% Fe, a maximum 1% Ti, a maximum 0.25% C, a maximum 0.15% Mn, and a maximum 0.15% Si), hastelloy, monel 400, inconel 825, or the like; or other suitable material. Some examples of suitable polymers may include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM), polybutylene terephthalate (PBT), polyether block ester, polyurethane, polypropylene (PP), polyvinylchloride (PVC), polyether-ester (for example a polyether-ester elastomer such as ARNITEL® available from DSM Engineering Plastics), polyester (for example a polyester elastomer such as HYTREL® available from DuPont), polyamide (for example, DURETHAN® available from Bayer or CRISTAMID® available from Elf Atochem), elastomeric polyamides, block polyamide/ethers, polyether block amide (PEBA, for example available under the trade name PEBAX®, silicones, polyethylene (PE), Marlex high-density polyethylene, Marlex low-density polyethylene, linear low density polyethylene (for example REXELL®), polyethylene terephthalate (PET), polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polysulfone, nylon, perfluoro(propyl vinyl ether) (PFA), other suitable materials, or mixtures, combinations, copolymers thereof, polymer/metal composites, and the like. In some embodiments, portions of or all of the device can be blended with a liquid crystal polymer (LCP). For example, the mixture can contain up to about 5% LCP.
In some embodiments, a coating, for example a lubricious, a hydrophilic, a protective, or other type of coating may be applied over portions or the entire device. Hydrophobic coatings such as fluoropolymers provide a dry lubricity which improves device exchanges. Lubricious coatings improve steerability and improve lesion crossing capability. Suitable lubricious polymers are well known in the art and may include silicone and the like, hydrophilic polymers such as polyarylene oxides, polyvinylpyrolidones, polyvinylalcohols, hydroxy alkyl cellulosics, algins, saccharides, caprolactones, and the like, and mixtures and combinations thereof. Hydrophilic polymers may be blended among themselves or with formulated amounts of water insoluble compounds (including some polymers) to yield coatings with suitable lubricity, bonding, and solubility. Some other examples of such coatings and materials and methods used to create such coatings can be found in U.S. Pat. Nos. 6,139,510 and 5,772,609, which are incorporated herein by reference. In some embodiments, the sheath or coating may be applied over basket region. This may provide extra surface area to contain clots that might be captured therein. The sheath or polymeric layer coating may be formed, for example, by coating, electrophoresis, by extrusion, co-extrusion, interrupted layer co-extrusion (ILC), or fusing several segments end-to-end. The layer may have a uniform stiffness or a gradual reduction in stiffness from the proximal end to the distal end thereof. The gradual reduction in stiffness may be continuous as by ILC or may be stepped as by fusing together separate extruded tubular segments. The outer layer may be impregnated with a radiopaque filler material to facilitate radiographic visualization. Those skilled in the art will recognize that these materials can vary widely without deviating from the scope of the present invention. The device, or portions thereof, may also be coated, plated, wrapped or surrounded by, doped with, or otherwise include a radiopaque material. For example, the wires or coils may be made from a radiopaque material or may include a radiopaque marker member or coil coupled thereto. Radiopaque materials are understood to be materials capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique during a medical procedure. This relatively bright image aids the user of the device in determining its location. Some examples of radiopaque materials can include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloy, plastic material loaded with radiopaque filler, and the like. An important practical concern in thrombectomy procedures is the accuracy of the navigational process used to direct the endovascular placement of a thrombectomy device 30 relative to the location of a thrombus. Magnetic resonance imaging can play an important role in localizing and characterizing the thrombus and in optimizing the positioning of the thrombectomy device. High-speed, high-resolution MR imaging can now be combined with conventional X-ray fluoroscopy and digital subtraction angiography (DSA) capability in a single hybrid imaging unit. New generations of MR scanners provide frequently updated images of the anatomical structures of interest. This real-time imaging capability makes it possible to use high-speed MR imaging to direct the movement of catheters and other components of the thrombectomy system to specific endovascular locations, and thereafter observe the effects of specific interventional procedures. MR imaging is also valuable in assessing the presence and size of an intracranial thrombus and in characterizing its age and composition. A growing body of evidence suggests that a combination of MR imaging and neurologic symptoms may in fact have prognostic predictive value in assessing patient outcome. During formation of a thrombus, the blood contains a mixture of oxyhemoglobin, deoxyhemoglobin and methemoglobin that is usually equal to that of arterial blood. As the thrombus ages, however, the concentration of paramagnetic hemoglobin and methemoglobin within the clot also changes resulting in a characteristic appearance on MR images that reflects the age and stability of the clot.
Observation of these MR imaging changes can be clinically useful in evaluating the potential utility of various alternative interventions, such as, for example, drug thrombolytic therapy versus mechanical thrombectomy. The catheter tip on thrombectomy devices described in the prior art is difficult to see on MRI because of inadequate contrast with respect to surrounding tissues and structures. This makes accurate localization difficult and degrades the quality of the diagnostic information obtained from the image. Thus, one objective of this invention is to provide an MR-compatible and visible device that significantly improves the efficacy and safety of thrombus removal using MR guidance. For example, to enhance compatibility with MRI imaging systems, it may be desirable to make portions of the device in a manner that would impart a degree of MRI compatibility. For example, the device, or portions thereof, may be made of a material that does not substantially distort the image and create substantial artifacts (artifacts are gaps in the image). Certain ferromagnetic materials, for example, may not be suitable because they may create artifacts in an MRI image. The device, or portions thereof, may also be made from a material that the MRI machine can image. Some materials that exhibit these characteristics include, for example, tungsten, Elgiloy, MP35N, nitinol, and the like, and others.
Any material that might be added to the structure of a pliable catheter to make it MR visible must not contribute significantly to the overall magnetic susceptibility of the catheter, or imaging artifacts could be introduced during the MR process. It is also important that thrombectomy devices used under MR guidance are MR-compatible in both static and time-varying magnetic fields. Examples of such biocompatible and MR-compatible materials which could be used to practice the invention include elastomeric hydrogel, nylon, teflon, polyamide, polyethylene, polypropylene, polysulfone, ceramics, cermets steatite, carbon fiber composites, silicon nitride, and zirconia, plexiglass, and poly-ether-ether-ketone. Although the mechanical effects of the magnetic field on ferromagnetic devices 10 present the greatest danger to patients through possible unintended movement of the devices, tissue and device heating may also result from radio-frequency power deposition in electrically conductive material located within the imaging volume. Consequently, all cables, wires, and devices positioned within the MR imaging system must be made of materials that have properties that make them compatible with their use in human tissues during MR imaging procedures. Many materials with acceptable MR-compatibility, such as ceramics, composites and thermoplastic polymers, are electrical insulators and do not produce artifacts or safety hazards associated with applied electric fields. Some metallic materials, such as copper, brass, magnesium and aluminum are also generally MR-compatible, viz. large masses of these materials can be accommodated within the imaging region without significant image degradation. Guidewires for the catheter component of the thrombectomy system are usually made of radiopaque material so that their precise location can be identified during a surgical procedure through fluoroscopic viewing. Exemplary of guidewires used under X-ray viewing is the guidewire disclosed by LeVeen, U.S. Pat. No. 4,448,195, in which a radiopaque wire can be identified on fluoroscopic images by metered bands placed at predetermined locations. U.S. Pat. No. 4,922,924, awarded to Gambale et al. discloses a bifilar arrangement whereby radiopaque and radiotransparent filaments are wrapped on a mandril to form a bifilar coil which provides radiopaque and radiotransparent areas on the guide wire. U.S. Pat. No. 5,375,596 to Twiss et al. discloses a method for locating catheters and other tubular medical devices using an integrated system of wire transmitters and receivers. Initial attempts to position and visualize endovascular devices such as catheters in MR imaging were based on passive susceptibility artifacts produced by the device when exposed to the magnetic field. Magnetic susceptibility is a quantitative measure of a material's tendency to interact with and distort an applied magnetic field. U.S. Pat. No. 4,827,931, to Longmore and U.S. Pat. Nos. 5,154,179 and 4,989,608 to Ratner disclose the incorporation of paramagnetic material into endovascular devices to make the devices visible under MR imaging. U.S. Pat. No. 5,211,166 to Sepponen similarly discloses the use of surface impregnation of various “relaxants”, including paramagnetic materials and nitrogen radicals, onto surgical instruments to enable their MR identification. An improved method for passive MR visualization of implantable medical devices has been disclosed by Werne in U.S. Pat. No. 5,744,958. In the method of the invention disclosed by Werne, an ultra-thin coating of conductive material comprising 1-10% of the theoretical skin depth of the material being imaged is applied. By using a coating of 2,000-25,000 angstroms thickness, Werne has found that the susceptibility artifact due to the metal is negligible due to the low material mass. At the same time, the eddy currents are limited due to the ultra-thin conductor coating on the device. However, these patents do not provide for artifact-free MR visibility in the presence of rapidly alternating magnetic fields, such as would be produced during echo-planar MR imaging pulse sequences used in real-time MR guided thrombectomy procedures. Nor do these patents teach a method for monitoring with MR-visible catheters the outcomes of therapeutic interventions, such as, for example, removal of a thrombus from the intracranial circulation followed by therapeutic drug delivery into brain tissues. Thus, there is a continuing need to develop an MR-compatible and visible thrombectomy device that does not obscure surrounding anatomy, and thereby compromise the physician's ability to perform the intervention.
The control wire(s) used to practice the present invention may be produced from any number of suitable materials having reasonable strength in tension, e.g., stainless steels, carbon fibers, engineering plastics, tungsten alloys, variously in the form of a multi-strand cable or single strand thread. Preferably, however, the wire may be made from a “so-called” super-elastic alloy. These alloys are characterized by an ability to transform from an austenitic crystal structure to a stress-induced martensitic (SIM) structure and to return elastically to the austenitic crystal structure (and the original shape) when the stress is removed. A typical alloy is nitinol, a nickel-titanium alloy, which is commercially available and undergoes the austenite-SIM-austenite transformation at a variety of temperature ranges. These materials are described, for instance in U.S. Pat. Nos. 3,174,851 and 3,351,463. These alloys are especially suitable because of their capacity to elastically recover almost completely to the initial configuration once the stress is removed. Since this is so, the size of the actual wire may be made fairly small, e.g., as small as 0.005 inches in diameter or smaller, and the resulting device is able to access very small regions of the body. The wire may also vary in diameter along its length, for example have a larger diameter at the proximal end as compared to the distal end or vice versa. The wires can have a proximal section and a distal section. The proximal section preferably has a uniform diameter of at least about 0.0001 inch, or about 0.005 to 0.025 inches, preferably 0.0010 to 0.018 inches. Commercially available wires with a material (wire) diameter of 0.008 mm and a loop diameter of 1 mm are available as microcoil materials. Optionally, the distal section that may extend beyond the catheter may have different (more or less) flexibility than the proximal section. Typically, both sections will extend from the distal and proximal ends of the catheter lumen. The wire may have a middle section having a diameter intermediate between the diameter of the two portions of the wire adjoining the middle section or the middle section may be continuously tapered, may have a number of tapered sections or sections of differing diameters, or may be of a uniform diameter along its length and be tapered at or near the distal section. The entire wire may be between about 50 and 300 cm, typically between about 175 to 190 cm in length. The wire may be wrapped to form a coil section or may be independently attached to a coil. The overall length of the pusher wire, pull wire, and soft coil mesh may extend through a catheter and the wires and catheter inserted into the vasculature. The catheter and wires (with attached soft coil) may extend proximal or distal to the site of the clot or the catheter may be positioned and the wires extend to the site from the catheter. The configurable soft coil component of the device is positioned near the target thrombus site, and the wires position and control the positioning and attitude of the soft coil capture components.
The coil product may be provided in packaging as a loop of the coil in wrapping, such as bubble wrap, packets, paperboard supporting a cover, and any other format of packaging that protects the device and preferably keeps the device in antiseptic conditions. For example, the device is intended for one time, sterile use. It could be inserted into a rigid polyethylene tube Carrier. The Carrier will be inserted into a Tyvek/polyethylene pouch pre-sealed on three sides. The pouch will then be heat-sealed closed and a label placed on the clear polyethylene film. The sealed pouch along with an Instruction for Use will be inserted into an appropriately sized carton. The carton label, similar to the pouch label, will be applied over the edge of the carton to allow label information to be displayed on the front, side, and back panels.
One major embodiment of this technology is for a Mechanical Retrieval Device (Device) that is a single use medical device. The Device is intended to be used to safely and effectively remove obstructions from blood vessels in the human body. One embodiment of the Device comprises thin wire coils placed within a microcatheter having a small internal diameter (0.024″ or less). A guide catheter of larger diameter is positioned using angiography guidance into the blood vessel that contains the obstruction. The microcatheter may be inserted through the guide catheter and led by a microguidewire to pass between the obstruction and the lumen wall. The microguidewire is retracted and soft platinum coils are passed through the microcatheter on the distal side of the obstruction. The microguidewire is then retracted further to permit platinum or stainless steel coils to be placed on the proximal side of the obstruction. Portions of the coils then wrap around the obstruction, producing a mesh that prevents fragmentation of the obstruction. The mesh and knot are tightened mechanically using a pull string and the mesh and obstruction are pulled back toward the end hole of the guide catheter. Whenever possible, the obstruction is pulled into the guide catheter and out of the body. If the obstruction is too large to be removed through the guide catheter, the guide catheter and obstruction are withdrawn together. Among the benefits of this type of system is that the Device design is intended to allow easier access into anatomically difficult locations because it is pushed out of a microcatheter. Other devices such as those delivering laser, ultrasound, or photo-acoustical energy may be too stiff to access tortuous blood vessels, and too large to pass through a small microcatheter.
The Device can remove both soft and hard obstructions including blood clots and catheter fragments and coils. Other types of devices that are small enough to pass through a microcatheter are typically indicated for removal of soft materials such as an acute thrombus, and might be able to snare a foreign body. By comparison, our Device can fully enmesh and remove a hard object, such as a fibrin-laden thrombus. The Device can also remove soft materials, such as acute thrombus which becomes adherent to the coils of the Device. The Device is also designed to enmesh and retrieve a coil or catheter fragment 5 dislodged during an intravascular procedure. The Device features a series of soft platinum coils that may come into contact with the walls of blood vessels. Our preclinical studies indicate that these coils will not damage blood vessel walls, a crucial feature when working in arteries in the head and heart. The Device is similar in general design to a vascular guidewire.
A sketch of the Device design is shown below in
Proximal to the eyelet section, the coil element may be pre-shaped to form a spiraled coil shape. These coils, along with the user activated distal loops, are used to capture and retrieve a blood clot or other obstruction.
One example of a major outside diameter of the device is 0.021″ at the eyelet locations and is designed so that it can be inserted through a microcatheter with an internal lumen of 0.024″. The entire length of the device may be 175 cm. A general principle of operation for systems according to the present technology is shown in
An alternative description of elements for the practice of the present technology is as a medical device for removing a thrombus from a blood vessel comprising at least one microcatheter lumen having a length between a distal end and a proximal end, the at least one microcatheter lumen having within the at least one microcatheter lumen at least one region of a positionable and deployable macrocoil. The deployable macrocoil is deployable from the distal end of the microcatheter lumen and positionable about a shaped structure within a blood vessel distally located with respect to the length of the lumen. This device should have the macrocoil is conformable about the shaped structure because of flexibility and conformability in the macrocoil provided by microcoils within the macrocoil. The shaped structure usually comprises a thrombus within the blood vessel. The conformability is necessary because there is no uniform or unique shape for all thrombi. A method of capturing a solid object within a vessel in a patient would include inserting a medical device for removing a solid object from a vessel, the device comprising the device described directly above. The method would insert the medical device into a blood vessel so that a the microcatheter lumen is not beyond the solid object, deploy a first at least one deployable macrocoil beyond the solid object to provide a distal engaging element beyond the solid object and deploy a capture element for the shaped structure that is not beyond the solid object to form a proximal engaging structure for the solid object comprising the distal macrocoil and the capture element on relatively opposite sides of the solid object. This is clearly illustrated in
Another description of a method of capturing a solid object within a vessel in a patient comprising inserting the medical device described above would include: inserting the microcatheter lumen into a patient so that a first at least one deployable microcoil region or segment is beyond the solid object and a second at least one other microcoil region or segment is not beyond the solid object, using the first at least one deployable macrocoil beyond the solid object to provide a distal engaging element of a microcoil segment beyond the solid object and deploying the second at least one other microcoil segment not beyond the solid object to form a proximal engaging structure for the solid object. This method may include steps after forming the distal engaging structure and the proximal engaging structure, including withdrawing the medical device to withdraw the solid object from the vessel or move the solid object within the vessel. An alternatively described device for retrieval of objects from within vessels of patients would include: a length of microcoil having approximately helical turns continuously or within adjacent sections of the length of microcoil and the helical turns have an average diameter, at least some of the continuous length or the segments in the length of microcoil having eyelets that extend beyond the average diameter, and a core wire passing through at least some adjacent eyelets from a distal end to a proximal end of the length of microcoil, the core wire being restrained near the distal end of the length of microcoil. This device would prefer having the average diameter of the helical turns as less than 0.050 inches. The device would be carried within a lumen of a microcatheter wherein the lumen internal diameter is greater than the average diameter of the helical turns of the length of microcoil. The device would operate by tension applied on the proximal end of the core wire causing the length of microcoil to form loops outside of the average diameter of the length of microcoil.
As is shown in
Experimentation with the Thrombus Removal System has been conducted in order to remove both soft and very firm clot from the arterial lumens of multiple arteries (renal, subclavian, common and internal carotid arteries) in the pig model. Soft clot was only a few hours old. Hard clot was made by allowing a pig's blood to stand for four days. The firm, fibrin-containing portion separated from the plasma, and the hard clot embolized into the selected artery of a second pig. Both complex three-dimensional and less complex two-dimensional platinum coils were used in these experiments, including coil structures that were not designed for use in thrombectomy procedures, but rather being the commercially available types used to fill cerebral aneurysms. These coils have a variable cross-sectional diameter and length, and are attached to a stainless steel pusher wire. A commercially available microcatheter with an inner lumen of 0.018 inch was passed beyond the thrombus, particularly between the intima and the thrombus (non-occluded space between the thrombus and the walls) in the case of a firm thrombus, with the aid of a commercially available 0.014 inch microguidewire. A thin nylon line (0.006 inch) was attached to the distal end of a coil, and the coil/string complex gently passed into a microcatheter, to a point distal to the thrombus. Alternatively, the coil/string complex was preloaded into the microcatheter that was passed without the aid of a microguidewire past the distal end of the thrombus. The coils were pushed from the microcatheter, which was progressively pulled back until it was proximal to the thrombus and clot extraction attempted, as previously described. 10 Soft clot tended to be removed easily from the arteries studied because the clot adhered to the meshwork of the coil and the pulling wire. However, initial experiments with single coils of different sizes, including both 3-D and 2-D coils, demonstrated the inability to consistently and successfully extract the firm clot with this method, even when the coil had formed a mesh around the thrombus and the nylon string was pulled as much as possible to tighten the mesh around the clot. Rather, the coil sometimes simply unraveled from around the thrombus, sliding back into the more proximal microcatheter. It was apparent that in those failed circumstances the loops of the coil were simply wrapping around the clot without becoming tightly engaged, and that such a non-structured mesh was insufficient to overcome the combination of forces keeping the thrombus in place, including friction between the thrombus and the intima and blood flow pushing the embolus distally. However, intertwining and/or overlapping of the loops along the distal aspect of the thrombus, as one would tie a shoelace, kept the distal mesh in place without allowing the entire coil complex to unravel. In subsequent experiments, two microcatheters were passed distal to the firm clot, each positioned in the same manner as previously described. The distal end of a 3-D coil was pushed into the arterial lumen from the first microcatheter, then the distal end of a second coil, either a 2-D or a 3-D configuration, was pushed forward from the second microcatheter, allowing loops of the two coils to intertwine. By “two coils” in this description, it is meant that there are two masses of coils, one each delivered from a microcatheter, although the term includes two coil masses emanating from two lumens of a single microcatheter, as opposed to requiring two completely distinct microcatheters. Further coils were extended to make a complex, random mesh, then the nylon strings were pulled so that a tight “cap” or “knot” was formed on the distal surface of the clot. The microcatheters were partially withdrawn and as more coils were pushed from the microcatheter, they passively encircled the middle portions of the clot. The process was continued, with more coils (at least a total of two and up to six coils would be used in a preferred range of mesh applications) placed proximal to the clot. The nylon strings was then pulled tightly to form a tight meshwork encircling the entire clot so that little or no fragmentation would occur.
Using this technique, it was possible to successfully extract firm clots from all blood vessels embolized without evidence of fragmentation on subsequent post-extraction angiography. Coils having diameters equal to or slightly larger than that of the arterial lumen appeared to make the best distal meshwork and, therefore, the most stable macrocoil constructs. By then passively encircling the clot, there was no tendency for the distal “cap” to simply slide from the top over the side of the clot. Post-extraction angiography and post-mortem examination, including microscopy, did not demonstrate any evidence of vascular injury. This was the expected result, given the extensive experience of using these soft platinum coils within the vascular system without producing vascular dissection or vasospasm. Another way of generally describing articles and methods according to the practice of the technology originally disclosed herein includes a medical device for removing a thrombus from a blood vessel, comprising: a) two microcatheter lumens, each lumen containing: b) a macrocoil thrombus engaging component having a length with a proximal end and a distal end, the length of the macrocoil comprising microcoils that allow the length of the macrocoil to be extendable; c) a first wire capable of providing force on the distal end of the macrocoil; d) a second wire capable of providing force on the proximal end of the macrocoil. The device may have at least two lumens on distinct microcatheters, and the at least two lumens may be attached to a single catheter.
A method may be practiced for using the device wherein for at least one macrocoil thrombus engaging coil, a microguidewire is passed through at least one of the lumens to help place the microcatheter distal to the thrombus; the microguidewire is removed; a macrocoil pull-string system comprising push-pull capability is passed through the at least one of the lumens; the macrocoil pull-string system is passed distal to the clot; the pull-string system is used to form an at least partially enclosing distal meshwork on the distal surface of the thrombus, passively encircling mesh around the clot; the pull string is pulled to tighten the meshwork; the macrocoils may have internal structures including loops and other random attachments to facilitate the formation of a tight meshwork; and at least a portion of the device is progressively withdrawn so that the meshwork becomes more tightly engaged with the clot. The method of using the device may be practiced wherein the at least one set of microcoils of at least one macrocoil exhibits a conformation memory of an amorphous shape with overlapping structure resisting complete elongation when ends of the at least one macrocoil are stressed. The conformation memory may form at least one structure selected from the group consisting of knots, loops, multiple crossovers, kinks and snags to reduce excessive slipping of macrocoils, which slipping would allow liner extension of macrocoil material.
The method may have the at least one structure assist in forming a network comprising the at least one macrocoil engaging a distal surface of the thrombus. The method may be practiced so that the at least one macrocoil encircles or conforms to the surface of the distal side of the thrombus as the at least one macrocoil is extended from the microcatheter. The method may use a pull-string to tighten the at least one macrocoil against the distal side of the thrombus. A dual lumen catheter or two separate catheters may deploy a single macrocoil mesh with controls on both ends, or two separate meshes, each with one or two separate end controls of the macrocoil mesh in each lumen. Examples of the end control elements are a pull wire or push pull wire attached to either end of the macrocoil mesh. A thrombus usually has a potential space between the thrombus and the wall of the vessel, allowing the soft macrocoil mesh to passively slid between the surface of the thrombus and the vessel wall. It is to be noted that the deployed macrocoil mesh has no clearly defined shape (such as a basket, box, pyramidal coil complex, or the like) so that the macrocoil mesh may conform to any surface, such as that of the thrombus, as it passively surrounds that surface. Proximal ends of the controlling wires or strings may be used to control the location, deployment, tension, withdrawal and other movement of the macrocoil mesh by appropriately pushing, pulling, twisting, orienting, reorienting, positioning or otherwise moving those proximal ends. Passively encircling the clot reduces the chance of unwanted fragmentation of the thrombus and subsequent embolization of the fragment to vital tissues.
Where there is the deployment of two separate microcatheters, each with a separate macrocoil mesh element, each macrocoil mesh element may have separate end controls extending from each microcatheter, respectfully. Two mesh elements may integrate into a mass on the distal side of a thrombus. Push-pull guidance wire combinations are provided for the respective pairs of macrocoil elements.
In the use of a dual lumen catheter system deploying two macrocoil meshes with separate end controls for each mesh coming out of each lumen of the microcatheter, the distal ends of the mesh, the end controls may operate as push-pull wires, guidance wires, orientation elements, positioning elements, current carrying conductors (as when heating the microcoils in the macrocoil mesh) and the like. The end controls may be the same or different in the construction of the device to assure their ability to perform the ultimately desired tasks. Both end controls aid in the formation of a knot or tight tangle of the distal ends of each macrocoil mesh over the distal aspect of the thrombus, in the passive encirclement of the mid and proximal portions of the thrombus, and in the tightening of the meshwork around the surface of the thrombus. It is to be noted that the dashed lines for catheters shown behind thrombus in some of the illustrations are not intended to limit the images to catheters passing through the thrombus, and in fact as clearly described herein, the location of the catheters is preferably adjacent to a thrombus. In this regard, it is one of the many novel aspects of the present technology that may be practiced according to these teachings that the catheters are intentionally passed adjacent to and not through a thrombus. It is also novel to pass multiple catheters adjacent to a thrombus in a single medical procedure according to the technology described herein.
There are numerous considerations of materials and properties that can be discussed herein to provide general and specific assistance to the design of instruments for various locations and procedures. The composition of the microcoils forming the macrocoil mesh may be any material that will retain its structural integrity during the expected length of an extended procedure, with safeguards built in for overextended periods of the coils being within an environment that may deteriorate or dissolve them. For example, if a standard procedure were expected to take 1-2 hours, it would be appropriate if the coils would remain intact in the operational environment for at least 24 hours and retain their physical properties. The microcoil material can be allowed to breakup or even dissolve after that time, in the event that there is a problem during the procedure, such as if a coil breaks or separates from the mesh. Typically, the microcoil material will have essentially unaffected properties during the operation. Useful materials may be metals, alloys, plastics (polymeric materials), composites, ceramics and the like. The properties of the microcoil material are intended to provide the macrocoil mesh with resilient properties through the extensibility of the microcoils and macrocoils, and not necessarily elasticity in the material of the wire forming the various coils. The material of the wire may in fact be clearly inelastic within standards for metal wire, plastic wire, ceramic wire and composite wire, for example, having less than 20% or 10% elongation at breaking point for the wire.
Deployment of the at least one wire (with macrocoil mesh therein) may be from a single lumen on a catheter, multiple lumens on a single catheter, single lumens on multiple catheters, multiple lumens on multiple catheters, and 1, 2, 3, 4, 5 6 or more catheters or microcatheters may be used in the process. The multiple coils may remain separate and distinct when deployed, may incidentally overlap, may intentionally overlap, may tangle with each other, may grip each other or otherwise interact. For example, when the distal ends of the macrocoils are extended from the microcatheter lumens (one microcatheter with two lumens or two separate microcatheters with one lumen each), they will overlap to produce a knot, tangle, or other firm connection. In addition, one or more of loops (the macrocoil loops) may engage each other to form a loose, incidental lock or slip resistant engagement between one or more macrocoils. Design may be built into the macrocoils, such as spikes (less preferred because of potential wall irritation), hooks and loops, posts, and hooks alone to produce a tighter mesh network and to decrease the likelihood of coil loops being extended to relatively ineffectual linearity when one end control is firmly pulled in attempting to position the mesh against the surface of a thrombus. There are many other variants that may be provided in the practice of the present technology. Among the variations to be considered is the use of actual knot-tying techniques using multiple macrocoil/microcoil structures according to the present descriptions. In the knot-tying format, two distinct macrocoils are fed from a single lumen, at least two separate lumens, or at least two adjacent lumens, such that a first macrocoil forms a loop with an opening large enough for a straight segment of a second macrocoil to pass through the opening, then passing at least one second macrocoil through the opening, and adjusting the local relative positions of the now at least two macrocoils so that a knot-like arrangement of the coils occurs. The interaction and engagement of the individual macrocoils of the at least two macrocoils also acts to provide a supporting structure and capability to the system. This feature is more than superficially beneficial. When prior art capture systems are analyzed, they are found to be essentially one-size-fits-all, with only minimum variability in the size of the capture device allowed because of the more defined structure of the capture, as can be noted in Rosenbluth (U.S. Pat. No. 6,511,492), where a variety of cage and net structures are provided. Especially with the cage structures, the likelihood of a thrombus being disrupted during insertion and retraction is very high, especially with the more rigid elemental constructions in the pyramidal coil and cage structures. The relatively fixed size of the capture portion means that the system will use a single size for a large thrombus or a small thrombus. The potential for damage or inoperability varies among the range of size of the potential thrombus, and might require an attempt to provide distinct capture systems with advanced knowledge (which may be erroneous) of the specific size and shape of the thrombus. The present technology, because of the flexibility and conformability of the macrocoil/microcoil structure, can be used on an extremely wide variation in size of thrombi, and the coils will themselves conform to the size of whatever thrombus is present. The pull strings aid in altering the position of the distal tip of one or more macrocoils, so that the formation of the knot is facilitated. The pull string also tightens the mesh work distal to the thrombus. Finally, after macrocoils are passively looped around the mid and proximal aspects of the clot, the pull string aids in tightening the entire construct to decrease the chance of clot fragmentation.
The presently described technology includes a medical device for removing a thrombus from a blood vessel. The device may comprise at least one microcatheter lumen, the at least one microcatheter lumen having at least two regions of a deployable macrocoil therein, each macrocoil segment being capable of separate deployment along a length of the macrocoil, and each of the at least two deployable macrocoils, when deployed, being capable of being withdrawn from a location by withdrawal of the lumen. The device may have at least one macrocoil segment comprises a macrocoil thrombus engaging component having a length with a proximal end and a distal end, the length of the macrocoil segment comprised of microcoils that allow the length of the macrocoil segment to be extendable and flexible. The device may also have at least two macrocoil segments comprise a macrocoil thrombus engaging component having a length with a proximal end and a distal end, the length of the macrocoil segment comprised of microcoils that allow the length of the macrocoil segment to be extendable and flexible 30 An alternative structure may comprise a medical device for removing a thrombus from a blood vessel having at least one microcatheter lumen, the at least one microcatheter lumen having at least one region of a distally positioned deployable macrocoil therein with respect to a length of the lumen and a shaped structure proximally positioned with respect to the length of the lumen. For example, the shaped structure may comprise a porous basket element, a porous coil of a different structure than the first macrocoil, a preformed shape or another porous deployable coil structure. The present technology also includes, a method of capturing a solid object within a vessel in a patient comprising inserting a medical device for removing a solid object from a vessel, the device comprising at least one microcatheter lumen, the at least one microcatheter lumen having at least one region of a distally positioned deployable macrocoil therein with respect to a length of the lumen and a shaped structure proximally positioned with respect to the length of the lumen, the inserting done so that a first at least one deployable microcoil is beyond the solid object and the shaped structure is not beyond the solid object, deploying the first at least one deployable microcoil beyond the solid object to provide a distal engaging element beyond the solid object and deploying the shaped structure not beyond the solid object to form a proximal engaging structure for the solid object. In this method after forming the distal engaging structure and the proximal engaging structure, the device itself or portions thereof may be withdrawn to withdraw the solid object from the vessel or move the solid object within the vessel. Another method of capturing a solid object within a vessel in a patient comprises inserting a medical device for removing a solid object from a vessel. The device would then comprise at least one microcatheter lumen, the at least one microcatheter lumen having at least two regions of a deployable macrocoil therein, each macrocoil segment being capable of separate deployment along a length of the macrocoil, and each of the at least two deployable macrocoils, when deployed, being capable of being withdrawn from a location by withdrawal of the lumen, the inserting being done so that a first at least one deployable microcoil is beyond the solid object and a second at least one other microcoil is not beyond the solid object, deploying the first at least one deployable microcoil beyond the solid object to provide a distal engaging element beyond the solid object and deploying the second at least one other microcoil not beyond the solid object to form a proximal engaging structure for the solid object. Also in this method, after forming the distal engaging structure and the proximal engaging structure, withdrawing the device or a portion thereof to withdraw the solid object from the vessel or move the solid object within the vessel while the solid object is secured distally and proximally along the direction of movement. Additionally, as noted elsewhere, the conformability of the macrocoil system of the described technology offers the potential for reduced disruption of a thrombus and the generation of floating clots that could cause a stroke.
Although there is never a guarantee, at least the potential is there for reducing the likelihood of such potentially disastrous events. Animal and bench experiments have been performed using the Device. Studies were performed that investigated the removal of both soft and very firm fibrin-laden clot material from the arterial lumens of multiple blood vessels (renal, subclavian, external and internal carotid arteries) in the pig model. Soft clot was only a few hours old. Hard clot was made by allowing a pig's blood to stand for 4-6 days. The firm, fibrin-containing portion separated from the plasma, and the hard clot was embolized into the selected artery of a second pig.
Methodology Summary Study I. A commercially available microcatheter with an inner lumen of 0.018″ was passed beyond the thrombus, specifically between the intima and the thrombus (non-occluded space between the thrombus and the walls). In the case of a firm thrombus, the process was aided by a commercially available 0.014″ microguidewire. A thin nylon line (0.006″) was attached to the distal end of a coil and the coil/string complex gently passed into a microcatheter to a point 15 distal to the thrombus. Alternatively, the coil/string complex was preloaded into the microcatheter that was passed without the aid of a microguidewire past the distal end of the thrombus. The coils were pushed from the microcatheter, which was progressively pulled back until it was proximal to the thrombus and clot extraction attempted, as previously described. Summary Study I Soft clot tended to be removed easily from the arteries studied because the clot adhered to the meshwork of the coil and the pulling wire of the Device. However, initial experiments with single coils of different sizes, including both 3-D and 2-D coils, demonstrated the inability to consistently and successfully extract the firm clot with this method, even when the coil had formed a mesh around the thrombus and the nylon string was pulled as much as possible to tighten the mesh around the clot. Rather, the coil sometimes simply unraveled from around the thrombus, sliding back into the more proximal microcatheter. It was apparent in those failed circumstances that the loops of the coil were simply wrapping around the clot without becoming tightly engaged and that such a non-structured mesh was insufficient to overcome the combination of forces keeping the thrombus in place, including friction between the thrombus and the intima and blood flow pushing the embolus distally. However, intertwining and/or overlapping of the loops along the distal aspect of the thrombus, as one would tie a shoelace, kept the distal mesh in place without allowing the entire coil complex to unravel.
Methodology Summary Study II. In subsequent experiments, two microcatheters were passed distal to the firm clot, each positioned in the same manner as previously described. The distal end of a 3-D coil was pushed into the arterial lumen from the first microcatheter, then the distal end of a second coil. Either a 2-D or a 3-D configuration was pushed forward from the second microcatheter, allowing loops of the two coils to intertwine. By “two coils” in this description, it is meant that there are two masses of coils, each delivered from a microcatheter. The term includes two coil masses emanating from two lumens of a single microcatheter, as opposed to requiring two distinct microcatheters. Further coils were extended to make a complex, random mesh, and then the nylon strings were pulled so that a tight “cap” or “knot” was formed on the distal surface of the clot. The microcatheters were partially withdrawn and as more coils were pushed from the microcatheter, they passively encircled the middle portions of the clot. The process was continued with more coils (at least a total of two and up to six coils would be used in a preferred range of mesh applications) placed proximal to the clot. The nylon strings were then pulled tightly to form a tight meshwork encircling the entire clot so that little or no fragmentation would occur.
Summary Study II Using this technique, it was possible to successfully extract firm clots from all vessels embolized without evidence of fragmentation on subsequent post-extraction angiography. Coils having diameters equal to or slightly larger than that of the vascular lumen appeared to make the best distal meshwork and therefore, the most stable macrocoil constructs. By then passively encircling the clot, there was no tendency for the distal “cap” to slide from the top over the side of the clot. Post-extraction angiography and post-mortem examination, including microscopy, did not demonstrate any evidence of arterial injury.
There are at least three main elements that may be individually or collectively included in the Comprehensive Clot Removal System (CCRS). 1) The original applications assigned to NexGen that are incorporated herein by reference in their entirety (U.S. Ser. No. 11/097,354, filed 1 Apr. 2005, Stephanos Finitsis; and Ser. No. 11/356,321, filed Feb. 16, 2006) applications cover a coil element referred to as MRD (mechanical retrieval device). Along with 1) changes to the MRD, the present technology further includes 2) a clot compression braid, and 3) a distal dilatation element. The internal diameter of the delivery catheter may be on the order of 3 mm or less, such as 2 mm, 1 mm, 0.5 mm, 0.1 mm and even lower. The spacing between adjacent centers of coil wires (e.g., shown as 0.005 inches (0.125 mm) in
In
In
7Q(f) shows an alternative deign and method of actuation where the braid is smaller than the vessel diameter and is expanded using a pull wire to create axial compression resulting in radial expansion.
In
Other variations in the materials, designs and processes may be apparent and obvious to those skilled in the art from the generic teaching and examples provided herein. The present technology describes a mechanical retrieval device, such as a thrombus removing device, a stone-removing device (e.g., gall stone, kidney stone) or plaque removing device (from within pipes, tubes and conduits, as well as fluid flow vessels within a mammal) and methods for using those devices. One embodiment as described and enabled herein may be described in its various aspects as follows. The embodiment of the device may have: a) an extensible array of coils comprising a wire with a helical or linear spring array of coils having an axis common to at least some consecutive coils in the array.
The term extensible means that, if the array of coils (which to the layman might look like a spring door spring) were able to have tension applied at both ends of the array of coils, without anything preventing the stretching or extending of the array of coils, the array of coils would extend or stretch. Although the array of coils may extend or stretch during performance of retrieval of solid blockage that is to be retrieved, it is not essential that the overall length of the coil array actually extends or stretches. This can be seen in the figures where adjacent wires in the windings that form the loops remain in contact (at one position within the loops) with the wires in adjacent loops. Therefore, extension or stretching of the coil itself is quite minimal, although some may exist. b) multiple eyelets are attached to the array of coils and extending away from the common axis, at least some of the multiple eyelets being separated by at least 2, at least 4, at least 6, or at least 10 (or more, e.g., 12, 16, 20 etc.) consecutive coils having a linear common axis to form segments of coils between eyelets; Another way of describing this segmenting of the array of coils along its length is that loops that are formed by retracting segments of multiple windings (individual coils within the coil array) causes loops to form that are at least 110%, preferably at least 120%, at least 130%, at least 140%, 150%, 160%, 200%, 300%, 400%, 500%, 600% and more greater width of the loops than the normal, non-compressed diameter of the windings (individual coils) in the segments of the extensible coil array. c) a core wire passes through the multiple eyelets and the core wire is attached to a distal portion of the series of eyelets on the extensible array of coils. The attachment to a point at or near the distal end itself is important as that attachment allows tension to be placed against the last or later eyelets to enable that the last or later eyelets to be retracted towards an adjacent eyelet having the core wire pass through it. This retraction of the eyelets towards each other forces the segment of coils in the coil array between the retracting eyelets to form a loop. d) the extensible array of coils preferably has within a center area of the extensible array of coils an anti-stretch element in the center area. (See for example, dashed line 122 in
The anti-stretch element my comprise, by way of a non-limiting example, a polymeric fabric, thread, filament or monofilament, and the anti-stretch element may be a fabric, thread or filament comprising at least one component selected from the group consisting of metal, carbon, and polymer. The anti-stretch element may be made of various materials compatible with its use within the human body, such as, by way of non-limiting examples, a metal filament anti-stretch element comprising nickel and titanium or stainless steel, a fluorinated ethylenic polymer (e.g., polytetrafluoroethylene and its copolymers, including Kevlar® polymer), and the anti stretch element may be affixed to the distal end of the extensible array of coils by solder or adhesive. The anti-stretch element may be affixed to the micro-coil and a pull wire at the distal end of the extensible array of coils. The anti-stretch element may be affixed to the extensible array of coils, a pull wire at the distal end of the extensible array of coils, and an radiopaque coil that is attached at or near the distal end of the extensible array of coils and comprises a composition that is different from the composition of the extensible array of coils. The radiopaque coil may have an eyelet on it or not. The mechanical retrieval device may have the anti-stretch element comprise a shaft having of an anti-stretch coil distinct from the extensible array coils, and the anti-stretch coil comprises a wire of an at least three-layer tube having a stiff outer polymer sheath (such as polyimide or PEEK), a fabric (e.g., woven, knitted, or stretchable non-woven, or braided) middle layer of bioacceptable metal (e.g., polymer or composite, such as made of Kevlar® polymer, Stainless steel, or Nitinol™ surgical metal, and a low friction inner polymer layer (such as polyethylene, polysiloxane or polytetrafluoroethylene, polyurethane and copolymers thereof). The anti-stretch element may be affixed to a proximal end of the extensible array of coils and to a tube providing a conduit for the core wire.
Another way of describing the present technology is as a mechanical retrieval device having a width in an relaxed state of the mechanical retrieval device and a length and an axis extending along the length of the relaxed mechanical retrieval device, the mechanical retrieval device comprising an extensible array of coils and a pull wire attached to a distal end of the extensible array of coils, wherein tension applied to the pull wire causes loops to form in sections of the extensible array of coils, the loops expanding the width of the mechanical retrieval device from that of the mechanical retrieval device in its relaxed state, and a covering sock element surrounding the mechanical retrieval device such that when the loops are formed, the sock distends providing a mesh net over the loops with which to catch particles of a solid object being retrieved. That mechanical retrieval device may have distances between the eyelets are varied so that at least some segments of the coils in the distensible array of coils have different numbers of coils in the segments than other segments. This will cause loops of different sizes to be formed from within a single device. The mechanical retrieval device may be formed wherein eyelets are formed on a micro-coil using a continuous winding process, with individual or multiple coils pulled away from the common axis to form the eyelets.
An alternative mechanical retrieval device may also be described comprising: a) an extensible array of coils comprising a wire with a helical or linear spring array of coils having an axis common to at least some consecutive coils in the array; b) multiple eyelets attached to the array of coils and extending away from the common axis, at least some of the multiple eyelets being separated by at least 2 consecutive coils having a linear common axis to form segments of adjacent coils between eyelets; c) a core wire passing through the multiple eyelets and attached to a distal portion of the extensible array of coils; d) the extensible array of coils having within a center area within the coils of the extensible array of coils an anti-stretch element in the center area, the an antistretch element being affixed to the a distal end of the extensible array of coils and resisting extension of the extendable array of coils. The coils tend to form a tunnel within the array of coils. The anti-stretch element is preferably within that “tunnel,” but may also extend along an exterior wall of the array of coils to act as an anti-stretch element; e) wherein upon application of tension to the core wire, tension is applied to distal portion of the extensible array of coils, overcoming any significant resistance of the anti-stretch element (if there is any at all), and apply compressing tension between adjacent eyelets to draw adjacent eyelets together to form loops of coils having ends of loops defined by adjacent eyelets. The anti-stretch element is preferably inside the micro-coil and is affixed to the micro-coil both distally and proximally, and an outer, flexible, conformable, porous sheath (with pores smaller than any open are within at least one loop) that may be sequentially retracted to selectively cover loops formed from the segments, closing large areas of the loops and catching particles that could pass through the open are of the loops. Another description of a mechanical retrieval device within the scope of the present technology may be a series of continuous, approximately linear arrays of coils, at least each series of coils having its common linear longitudinal axis, each series of coil separated from an adjacent series of coils separated by an eyelet comprising a radiopaque material that differentiates eyelets from coils under computerized tomography (CT) and X-Ray imaging. The radiopaque eyelets may be a tube comprising a noble metal or noble metal alloy. The radiopaque eyelets may, for example, comprise silver solder, polymer with radiopaque filler. A method of deploying such a mechanical retrieval device as described herein may have steps that include: positioning the outer sheath at or proximal to eyelets; using the sheath as a fulcrum and forming a loop by drawing at least two eyelets towards each other.
Another method of deploying a self-expanding element that can be compressed, comprising providing the self-expanding element to a site while contained in a catheter in a first compressed state, withdrawing the catheter while expanding the self-expanding element to a larger uncompressed diameter, entraining the payload target of material, and retracting and compressing the expanded self-expanding component with entrained target of material into the catheter. These methods may have further steps and use further structures such as: wherein the self-expanding element comprises an element fabricated into a mesh from a material selected from the group consisting of metal, polymer and/or carbon fiber; 15 wherein a distal end of the mesh is closed over the entrained target payload of material to prevent debris from the entrained target payload from escaping; wherein a mouth is created in the mesh and the mouth is then closed to prevent debris from escaping; wherein an axially rigid component is provided that is capable of applying axial tension and compression causing the diameter to expand or contract to at least 110% of 20 its delivered diameter and capable of receiving a payload of material for subsequent compression and/or removal; wherein the device is capable of compressing and/or removing debris that uses an expandable element to encapsulate the debris and/or compress it either by sliding an outer cannula over the element, retracting the element into a cannula, or by applying axial tension to the element to reduce its diameter; the self-expanding vessel dilating 25 element capable of preventing the wall of a vessel from collapsing by expanding to a diameter approximately equal to the inside diameter of the vessel, that is delivered on an wire (or a tube) where both ends are free to slide axially on the wire (or tube) up to one or more fixed stops on the wire or tube; a self expanding vessel dilating element capable of preventing the wall of a vessel from collapsing by expanding to a diameter approximately equal to the 30 inside diameter of the vessel, that is delivered on an wire (or a tube) where one end is free to slide axially on the wire (or tube) and the other end is fixed on the wire or tube; an expandable vessel dilating element 49 capable of preventing the wall of a vessel from collapsing by expanding to a diameter approximately equal to the inside diameter of the vessel, that is delivered on an wire (or a tube) where both ends are free to slide axially on the wire (or tube) up to one or more fixed stops on the wire or tube; an expandable vessel dilating element 5 capable of preventing the wall of a vessel from collapsing by expanding to a diameter approximately equal to the inside diameter of the vessel, that is delivered on an wire (or a tube) where one end is free to slide axially on the wire (or tube) and the other end is fixed on the wire or tube; wherein one or both ends of the dilating element are radiopaque, the fixed stop is radiopaque, or some combination thereof; wherein a coil made of a noble metal or 10 noble metal alloy is located inside the micro-coil to provide radiopacity. The device may include a functionally integrated compression element and a mechanical removal element. What the term “functionality Integrated” means is that a single structure is used to perform the two described tasks. A method of removing debris includes a compression element and a mechanical removal element. The device may also include a 15 functionally integrated compression element and a distal dilatation element. In this instance, the integrated functions in a single element are performed by the distal dilatation of the element upon release from the catheter (and the element entraining solids, and then the subsequent compression of the entrained solids and any loops within the integrated element as the device is withdrawn and compression pressure is applied by the integrated element. 20 The method for removing debris may include a device using both a compression element and a distal dilatation element. The device may also include a functionally integrated mechanical removal element and a distal dilatation element. A method of removing debris may include a mechanical removal element and a distal dilatation element. The device may also include a functionally integrated compression element, a mechanical removal element, and a distal 25 dilatation element. A method of removing debris includes using a device comprising a compression element, a mechanical removal element, and a distal dilatation element. When a porous sheath overlays the extensible array of coils and upon formation of loops from the extended array of coils, the porous sheath overlays the loops and reduces available flow-through area in the loops.
The present technology includes a mechanical retrieval device in a delivery catheter. The retrieval device for entraining and removing solid obstructions within blood vessels may include:
The mechanical retrieval device in a delivery catheter may be constructed wherein upon projection of all components of the mechanical retrieval device out of the catheter, both the distal expandable and compressible fabric array of coils and the proximal expandable and compressible fabric array expand within said blood vessel. The distal and proximal expandable and compressible fabric arrays may spontaneously expand (as a programmed memory metal), or require tension or pressure (through the guidewire, push wire, pull wire or spring-loaded or vertical accordion element that can be triggered to expand the proximal or distal expandable and compressible fabric array.
The mechanical retrieval device may have the distal or proximal expandable and compressible fabric array made of a fabric array having porosity when expanded that allows blood flow through the distal and proximal expandable and compressible fabric array.
The mechanical retrieval device may have multiple eyelets attached to the array of coils and extending away from the common axis, at least some of the multiple eyelets being separated by multiple consecutive coils having a linear common axis to form segments of coils between eyelets as explained in greater detail above. The mechanical retrieval device in a delivery catheter may have a core wire passing through the multiple eyelets, wherein the core wire is attached to a distal portion of the series of eyelets on the extensible array of coils, the extensible array of coils having a center volume within the extensible array of coils, and within that central volume within the extensible coils an anti-stretch element, wherein upon application of tension to the core wire, tension is applied to distal portion of the extensible array of coils, and the tension applies compressing tension between adjacent eyelets to draw adjacent eyelets together to form loops of the segments of coils, wherein beginning and end of individual loops are defined by adjacent eyelets.
A mechanical retrieval device having a width in a relaxed state of the mechanical retrieval device and a length and an axis extending along the length of the relaxed mechanical retrieval device. The mechanical retrieval device may have:
The mechanical retrieval device should have a), b) and c) present within a single delivery catheter. Upon projection of all components of the mechanical retrieval device out of the delivery catheter, both the distal expandable and compressible fabric array of coils and the proximal expandable and compressible fabric array expand within the blood vessel.
The distal expandable and compressible fabric array and the proximal expandable and compressible fabric array vascular are delivered to their target intravascular sites using a delivery catheter during interventional procedures to remove blood clots. The distal expandable and compressible fabric array minimizes embolization during interventional vascular procedures without compromising blood flow. This device component is low profile in order to reduce dislodging any intravascular plaque or thrombus during delivery of the device with the delivery catheter. The distal expandable and compressible fabric array is placed on a guidewire which is used to guide the operator to the site of clot obstruction in the blood vessel. The guidewire preferably has a soft floppy tip to prevent vessel dissection or damage, and is made of a material to enable it to be visible under x-ray. The distal expandable and compressible fabric array expands to the internal diameter of the blood vessel and traps any clot fragments and other debris during the catheter-based blood clot removal procedure. The device may also be used as a retriever of devices that may have malfunctioned or stones.
Delivery and positioning of the distal expandable and compressible fabric array and the proximal expandable and compressible fabric array are interventional catheter-based procedures typically performed under x-ray fluoroscopy to help guide the user through the vasculature. These device components are introduced in the patient as an ordinary guidewire with a soft floppy tip to prevent vessel dissection or damage. The guidewire is made of a material to enable it to be visible under x-ray, as the guidewire with protective sheath is introduced into the blood vessel. Once the operator navigates the wire through the vessel past the blood clot or other obstruction in the blood vessel, the sheath is removed or drawn proximally towards the user, after which the catheter is withdrawn. The distal expandable and compressible fabric array and the proximal expandable and compressible fabric array are soft enough with minimal wall thickness to fold into the delivery catheter. The material is sufficiently porous to allow blood to flow unimpeded.
The proximal expandable and compressible fabric array is intended for percutaneous access to the peripheral vascular system and is designed to assist in the removal of large clots and other obstructions. It is intended for single use and preferably has a HDPE catheter shaft attached to a braided Nitinol tip that expands as it is deployed from the lumen of a delivery catheter or sheath. The Nitinol braid passively expands to the contour shape of the blood vessel lumen and allows a separate device such as a catheter to be retracted into the braid. Both the Nitinol braid and the other device can then be retracted into the delivery catheter or sheath and removed from the body
The present application claims priority under 35 USC 120 as a continuation in-part application from Reissue application Ser. No. 15/050,442, filed 22 Feb. 2016 and titled “Thrombus Removal Process and System”, based on U.S. Pat. No. 8,603,122, filed 12 Oct. 2007 as U.S. Ser. No. 11/974,490 and Titled “Thrombus Removal Process and System” and U.S. Pat. No. 8,480,697, filed 2 Jun. 2011 as U.S. Ser. No. 13/152,004 and titled “Thrombus Removal Process and System,” and from U.S. Provisional Patent Application Ser. No. 61/340,910, filed 24 Mar. 2010. All applications cited herein are incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61340910 | Mar 2010 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15050442 | Feb 2016 | US |
| Child | 15094188 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11974490 | Oct 2007 | US |
| Child | 15050442 | US |
