Patent Application
20240081898
The present technology relates generally to devices and methods for removing obstructions from body lumens. Some embodiments of the present technology relate to devices and methods for removal of clot material from blood vessels.
Many medical procedures use medical device(s) to remove an obstruction (such as clot material) from a body lumen, vessel, or other organ. An inherent risk in such procedures is that mobilizing or otherwise disturbing the obstruction can potentially create further harm if the obstruction or a fragment thereof dislodges from the retrieval device. If all or a portion of the obstruction breaks free from the device and flows downstream, it is highly likely that the free material will become trapped in smaller and more tortuous anatomy. In many cases, the physician will no longer be able to use the same retrieval device to again remove the obstruction because the device may be too large and/or immobile to move the device to the site of the new obstruction.
Procedures for treating ischemic stroke by restoring flow within the cerebral vasculature are subject to the above concerns. The brain relies on its arteries and veins to supply oxygenated blood from the heart and lungs and to remove carbon dioxide and cellular waste from brain tissue. Blockages that interfere with this blood supply eventually cause the brain tissue to stop functioning. If the disruption in blood occurs for a sufficient amount of time, the continued lack of nutrients and oxygen causes irreversible cell death. Accordingly, it is desirable to provide immediate medical treatment of an ischemic stroke.
To access the cerebral vasculature, a physician typically advances a catheter from a remote part of the body (typically a leg) through the abdominal vasculature and into the cerebral region of the vasculature. Once within the cerebral vasculature, the physician deploys a device for retrieval of the obstruction causing the blockage. Concerns about dislodged obstructions or the migration of dislodged fragments increases the duration of the procedure at a time when restoration of blood flow is paramount. Furthermore, a physician might be unaware of one or more fragments that dislodge from the initial obstruction and cause blockage of smaller more distal vessels.
Many physicians currently perform thrombectomies (i.e. clot removal) with stents to resolve ischemic stroke. Typically, the physician deploys a stent into the clot in an attempt to push the clot to the side of the vessel and re-establish blood flow. Tissue plasminogen activator (“tPA”) is often injected into the bloodstream through an intravenous line to break down a clot. However, it takes time for the tPA to reach the clot because the tPA must travel through the vasculature and only begins to break up the clot once it reaches the clot material. tPA is also often administered to supplement the effectiveness of the stent. Yet, if attempts at clot dissolution are ineffective or incomplete, the physician can attempt to remove the stent while it is expanded against or enmeshed within the clot. In doing so, the physician must effectively drag the clot through the vasculature, in a proximal direction, into a guide catheter located within vessels in the patient's neck (typically the carotid artery). While this procedure has been shown to be effective in the clinic and easy for the physician to perform, there remain some distinct disadvantages to using this approach.
For example, one disadvantage is that the stent may not sufficiently retain the clot as it pulls the clot to the catheter. In such a case, some or all of the clot might remain in the vasculature. Another risk is that, as the stent mobilizes the clot from the original blockage site, the clot might not adhere to the stent as the stent is withdrawn toward the catheter. This is a particular risk when passing through bifurcations and tortuous anatomy. Furthermore, blood flow can carry the clot (or fragments of the clot) into a branching vessel at a bifurcation. If the clot is successfully brought to the end of the guide catheter in the carotid artery, yet another risk is that the clot may be “stripped” or “sheared” from the stent as the stent enters the guide catheter.
In view of the above, there remains a need for improved devices and methods that can remove occlusions from body lumens and/or vessels.
Mechanical thrombectomy (i.e., clot-grabbing and removal) has been effectively used for treatment of ischemic stroke. Although most clots can be retrieved in a single pass attempt, there are instances in which multiple attempts are needed to fully retrieve the clot and restore blood flow through the vessel. Additionally, there exist complications due to detachment of the clot from the interventional element during the retrieval process as the interventional element and clot traverse through tortuous intracranial vascular anatomy. For example, the detached clot or clot fragments can obstruct other arteries leading to secondary strokes. The failure modes that contribute to clot release during retrieval are: (a) boundary conditions at bifurcations; (b) changes in vessel diameter; and (c) vessel tortuosity, amongst others.
Certain blood components, such as platelets and coagulation proteins, display negative electrical charges. The systems of the present technology provide an interventional element and a signal generator configured to positively charge the interventional element during one or more stages of a thrombectomy procedure. For example, the signal generator may apply a constant or pulsatile direct current (DC) to the interventional element. The positively charged interventional element attracts negatively charged blood components, thereby improving attachment of the thrombus to the interventional element and reducing the number of device passes or attempts necessary to fully retrieve the clot. In some aspects of the present technology, the system includes an interventional element with a proximally positioned electrical engagement portion and a distally positioned mechanical engagement portion. The electrical engagement portion can include a plurality of discrete electrodes (e.g., conductive bands or other suitable structures), and the mechanical engagement portion can include an expandable member such as a self-expandable stent or basket. In operation the electrodes can be disposed within or radially adjacent a thrombus and the expandable member can be disposed at least partially distal to the thrombus. By supplying electrical current to the electrodes and/or the expandable member, the interventional element can engage the thrombus, allowing it to be removed from the blood vessel.
The present technology is illustrated, for example, according to various aspects described below. Various examples of aspects of the present technology are described as numbered clauses for convenience. These are provided as examples and do not limit the present technology. It is noted that any of the dependent clauses may be combined in any combination, and placed into a respective independent clause. The other clauses can be presented in a similar manner.
Clause 1. A treatment system comprising: a signal generator comprising a first electrical terminal; and a treatment device comprising: an axially elongated electrically conductive core member comprising a proximal end portion configured to be placed in electrical communication with the first electrical terminal and a distal end portion configured to be positioned proximate a thrombus within a lumen of a blood vessel at a treatment site; and an interventional element comprising the distal end portion of the core member, the interventional element further comprising: an electrical engagement portion including a plurality of discrete electrodes spaced apart from one another along the axial direction and configured such that the electrodes are in electrical communication with the conductive core member; and an expandable distal member coupled to the core member and disposed distal to the electrical engagement portion, the expandable distal member configured to expand from a low-profile state into an expanded state into apposition with a wall of the blood vessel at the treatment site when in an unconstrained state, wherein in the expanded state the expandable distal member is configured to engage a thrombus.
Clause 2. The system of any one of the preceding Clauses, further comprising a negative electrode in electrical communication with the signal generator, wherein the signal generator, the treatment device, and the negative electrode together form an electrical circuit.
Clause 3. The system of any one of the preceding Clauses, wherein the first electrical terminal is positive, the signal generator further comprising a second electrical terminal that is negative.
Clause 4. The system of any one of the preceding Clauses, wherein, when current is supplied via the signal generator, the interventional element is positively electrically charged to promote adhesion of a thrombus thereto.
Clause 5. The system of any one of the preceding Clauses, wherein the core member comprises at least one of: a flexible conductive wire and an electrically insulative coating along at least a portion of a length of the flexible conductive wire; or a conductive tube and an electrically insulative coating along at least a portion of a length of the conductive tube.
Clause 6. The system of any one of the preceding Clauses, wherein the electrodes comprise portions of the conductive wire or the conductive tube that are uninsulated.
Clause 7. The system of any one of the preceding Clauses, wherein the electrical engagement portion has a radially outermost dimension that tapers distally such that a radially outermost dimension of a distally located electrode is smaller than a radially outermost dimension of a proximally located electrode, and wherein the distal taper increases flexibility of the electrical engagement portion.
Clause 8. The system of any one of the preceding Clauses, wherein the electrodes comprise annular or semi-annular conductive elements extending at least half-way around a circumference of the core member.
Clause 9. The system of any one of the preceding Clauses, wherein the electrodes comprise conductive bands disposed over an outer surface of the core member.
Clause 10. The system of any one of the preceding Clauses, wherein the bands are separated from one another by electrically insulated regions of the electrical engagement portion, and wherein radially outer surfaces of the bands extend beyond radially outer surfaces of the insulated regions, thereby providing an enlarged surface area of the electrical engagement portion.
Clause 11. The system of any one of the preceding Clauses, wherein the expandable distal member comprises a stent or a basket.
Clause 12. The system of any one of the preceding Clauses, wherein the expandable distal member comprises a plurality of radiopaque markers coupled to the expandable distal member such that radial distances between the markers is greater when the expandable distal member is in the expanded state than when the expandable distal member is in the low-profile state.
Clause 13. A medical device comprising: an electrically conductive core member comprising a proximal end portion and a distal end portion, opposite the proximal end; and an interventional element comprising the distal end portion of the core member, the interventional element further comprising: a plurality of discrete electrodes spaced apart from one another along the core member, each of the electrodes extending about the core member distal end portion; and an expandable member disposed distal to the electrodes, the expandable distal member configured to expand from a low-profile state into an expanded state into apposition with a wall of the blood vessel at the treatment site when in an unconstrained state, wherein in the expanded state the expandable distal member is configured to engage a thrombus.
Clause 14. The device of any one of the preceding Clauses, wherein the core member comprises at least one of: an electrically conductive flexible wire and an electrically insulative coating along at least a portion of its length; or an electrically conductive tube having an electrically insulative coating along at least a portion of its length.
Clause 15. The device of any one of the preceding Clauses, wherein the electrodes are separated from one another by regions of the core member covered with the electrically insulative coating.
Clause 16. The device of any one of the preceding Clauses, wherein the core member distal end portion comprises a radially outermost dimension that tapers distally such that a radially outermost dimension of distally located electrode is smaller than a radially outermost dimension of proximally located electrode, and wherein the distal taper increases flexibility of the electrical engagement portion.
Clause 17. The device of any one of the preceding Clauses, wherein the electrodes comprise annular or semi-annular conductive elements extending at least half-way around a circumference of the core member.
Clause 18. The device of any one of the preceding Clauses, wherein the electrodes comprise conductive bands disposed over an outer surface of the core member.
Clause 19. The device of any one of the preceding Clauses, wherein the bands are separated from one another by insulated regions, and wherein radially outer surfaces of the bands extend beyond radially outer surfaces of the insulated regions.
Clause 20. The device of any one of the preceding Clauses, wherein the expandable member comprises a stent or a basket.
Clause 21. The device of any one of the preceding Clauses, wherein the expandable member includes a plurality of radiopaque markers coupled to the expandable distal member such that radial distances between the markers is greater when the expandable distal member is in the expanded state than when the expandable distal member is in the low-profile state.
Clause 22. A method for retrieving clot material from within a vessel lumen of a patient with a medical device comprising an electrically conductive core member having an interventional element coupled to a distal portion thereof and a plurality of discrete electrodes spaced apart from one another along a length of the core member, and an expandable member disposed distal to the electrodes, the method comprising: positioning the interventional element within the vessel lumen at or near the clot material, such that the electrical engagement portion of the interventional element is adjacent the clot material and the expandable member of the interventional element is disposed distal to the clot material; expanding the expandable member within the vessel lumen such that at least a portion of the expandable member contacts a wall of the vessel; delivering electrical current to the electrical engagement portion in order to cause adhesion of the clot material to the interventional element; and proximally retracting the interventional element through the vessel.
Clause 23. The method of any one of the preceding Clauses, further comprising ceasing delivery of the electrical current to the electrical engagement portion before proximally retracting the interventional element.
Clause 24. The method of any one of the preceding Clauses, wherein the electrical current is delivered to the electrical engagement portion while proximally retracting the interventional element.
Additional features and advantages of the present technology are described below, and in part will be apparent from the description, or may be learned by practice of the present technology. The advantages of the present technology will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Many aspects of the present technology can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on illustrating clearly the principles of the present disclosure.
As shown in
According to some embodiments, the signal generator 102 can include an electrical generator configured to output medically useful electric current. The signal generator 102 can include a power source, one or more electrical terminals for coupling to the treatment device 104, an electrode, or other component, and a suitable controller. The controller can include, for example, a processor coupled to a memory that stores instructions (e.g., in the form of software, code or program instructions executable by the processor or controller) for causing the power source to deliver electric current according to certain parameters provided by the software, code, etc. The power source of the signal generator 102 may include a direct current power supply, an alternating current power supply, and/or a power supply switchable between a direct current and an alternating current. The power source may therefore comprise a battery, transformer, rectifier, a connection to electrical mains or service grid, or any other suitable source of AC or DC electrical power. The signal generator 102 can include a suitable controller that can be used to control various parameters of the energy output by the power source or generator, such as intensity, amplitude, duration, frequency, duty cycle, and polarity. For example, the signal generator 102 can provide a voltage of about 2 volts to about 28 volts and a current of about 0.5 mA to about 20 mA. In some embodiments, the signal generator 102 is configured to deliver current to the interventional element 200 for about 1 minute to about 5 minutes, about 1 minute to about 3 minutes, or at least 2 minutes.
In some embodiments, the signal generator 102 can utilize drive circuitry rather than a processor. For example, the drive circuitry can include hardwired circuit elements to provide the desired waveform delivery (or a constant current) rather than a software-based generator. The drive circuitry can include, for example, analog circuit elements (e.g., resistors, diodes, switches, etc.) that are configured to cause the power source to deliver electric current via the first and second terminals according to the desired parameters. For example, the drive circuitry can be configured to cause the power source to deliver periodic waveforms.
With continued reference to
According to some embodiments, the bodies of the catheters can be made from various thermoplastics, e.g., polytetrafluoroethylene (PTFE or TEFLON®), fluorinated ethylene propylene (FEP), high-density polyethylene (HDPE), polyether ether ketone (PEEK), etc., which can optionally be lined on the inner surface of the catheters or an adjacent surface with a hydrophilic material such as polyvinylpyrrolidone (PVP) or some other plastic coating. Additionally, either surface can be coated with various combinations of different materials, depending upon the desired results.
As shown in
The core member 112 can include an elongate electrically inner body 113 in electrical communication with the signal generator 102 and the interventional element 200. In various examples, the inner body 113 of the core member 112 can include a wire, tube, coil, combinations thereof, or any other suitable structure. The inner body 113 of the core member 112 can be formed of any suitable electrically conductive material, including stainless steel, nitinol, etc. In some embodiments, the inner body 113 can be covered with an electrically insulative material 117 along at least a portion of its length. This insulative material 117 can include an insulative polymer (e.g., Parylene, PTFE) or other suitable material disposed via dip-coating, heat-shrinking, or any other suitable technique. Certain regions of the core member 112 may be uninsulated, for example a proximal end portion can be uninsulated to facilitate connection to the signal generator, and in some implementations the electrodes 206 of the electrical engagement portion 202 can be defined by regions of the core member 112 in which the insulative material 117 is absent, leaving the inner body 113 exposed on a radially outer surface. As shown in
In the illustrated example, the electrodes 206 take the form of ring-like members or bands that extend circumferentially about the core member 112. The electrodes 206 may provide a plurality of discrete, noncontiguous electrode sections about the central axis. Such sections can be in electrical communication with a common conductive path so as to function collectively as a single electrode, or with multiple separate such paths to allow one or more discrete electrodes to function independently if desired. For example, independent functionality of the electrodes may permit more fine-tuned distribution of electrical current at the treatment site. Additionally or alternatively, if the electrodes are electrically isolated from one another, then one or more of the electrodes may serve as an electrical sensor, which may be used to detect the presence or composition of a blood clot. This may permit the clinician to optimize therapy parameters to account for the clot location and/or properties. The electrodes 206 can include bands, rings, wires, or coils coupled to the core member 112, and/or may be defined by exposed portions of the core member 112 (e.g., regions of the conductive inner body 113 not covered by electrically insulative material 117). In addition to the annular configurations of the electrodes 206 shown in
The mechanical engagement portion 204 can include one or more structures that are configured to physically engage, interlock with, or otherwise contact and grasp a thrombus to facilitate its removal. In the illustrated example, the mechanical engagement portion 204 includes an expandable member 210 that is coupled to (and optionally in electrical communication with) the electrical engagement portion 202. Instead of or in addition to the expandable member 210, the mechanical engagement portion 204 can include barbs, hooks, protrusions, or other suitable non-expandable structures configured to engage a thrombus. The expandable member 210 can be, for example, a self-expandable stent, basket, mesh, filter, or other suitable structure. In various embodiments, the expandable member 210 can have a low-profile state for delivery through a microcatheter and an expanded state when it is released from the microcatheter or otherwise deployed at the treatment site. In the expanded state, the expandable member 210 can have a radially outermost dimension that is greater than that of the core member 112 and/or the electrical engagement portion 202. For example, the expandable member 210 can have a radially outermost dimension sized and configured to permit the expandable member 210 to come into contact with the vessel wall.
As illustrated in
The expandable member 210 can have a low-profile, constrained or compressed configuration (not shown) for intravascular delivery to the treatment site within the second catheter 110, and an expanded configuration for securing and/or engaging clot material and/or for restoring blood flow at the treatment site. The expandable member 210 may self-expand from the low-profile configuration to the expanding configuration upon translation from inside of to outside of the second catheter 110. All or a portion of the expandable member 210 can comprise an electrically conductive material. In some embodiments, the expandable member 210 comprises a laser-cut stent, a braid formed of a plurality of wires (e.g., filaments, threads, sutures, fibers or the like) that have been interwoven to form a structure having openings, or any other suitable structure. The expandable member 210 can be composed of metals, polymers, composites, and/or biologic materials. Polymer materials can include Dacron, polyester, polypropylene, nylon, Teflon, polytetrafluoroethylene (PTFE), tetrafluoroethylene, polyethylene terephthalate, polyactic acid (PLA) silicone, polyurethane, polyethylene, polycarbonate, styrene, polyimide, PEBAX, Hytrel, polyvinyl chloride, high-density polyethylene, low-density polyethylene, polyether ether ketone (PEEK), rubber, latex, and/or other suitable polymers known in the art. Other materials known in the art of elastic implants can also be used. Metal materials can include, but are not limited to, nickel-titanium alloys (e.g. Nitinol), platinum, cobalt-chromium alloys, stainless steel, tungsten or titanium. In certain embodiments, metal filaments may be highly polished and/or surface treated to further improve their hemocompatibility.
In some embodiments, the expandable member 210 may comprise an open cell framework or body and a coupling region extending proximally from the body. In some embodiments, a distal portion of the expandable member 210 can be generally tubular (e.g., cylindrical), and the proximal portion of the expandable member 210 tapers proximally to the coupling region. The proximal taper to the coupling region can permit a small-diameter coupling region to serve as an attachment point for the expandable member 210 even though a distal portion of the expandable member 210 has a significantly larger diameter than the coupling region. Additionally or alternatively, the proximal taper can facilitate resheathing of the expandable member 210, such as by proximally retracting the expandable member 210 into a surrounding catheter. In some embodiments, the expandable member 210 is a mesh structure formed of a superelastic material (e.g., Nitinol) or other resilient or self-expanding material configured to self-expand when released from the delivery catheter. For example, in some embodiments the expandable member 210 may be a stent and/or stentriever, such as Medtronic's Solitaire™ Revascularization Device, Stryker Neurovascular's Trevo® ProVue™ Stentriever, or other suitable devices. In other embodiments, the expandable member 210 may include a plurality of braided filaments. Examples of a suitable expandable member 210 include any of those disclosed in U.S. Pat. No. 7,300,458, filed Nov. 5, 2007, U.S. Pat. No. 8,940,003, filed Nov. 22, 2010, U.S. Pat. No. 9,039,749, filed Oct. 1, 2010, and U.S. Pat. No. 8,066,757, filed Dec. 28, 2010, each of which is incorporated by reference herein in its entirety.
In some examples, the expandable member 210 can take the form of a basket, filter, or other suitable structure configured to prevent clot material from advancing distally beyond the interventional element 200. In such implementations, the expandable member 210 can be configured to expand into apposition with the vessel wall and define a capture surface configured to prevent the passage of clot material while still allowing some blood flow therethrough.
In some embodiments, some or all of the expandable member 210 is formed by drawn-filled tube (“DFT”) wires having a radiopaque core (e.g., platinum, tantalum, gold, tungsten, etc.) surrounded by a superelastic material (e.g., Nitinol, a cobalt-chromium alloy, etc.). The radiopaque core may comprise about 5% to about 50% (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%) of the total-cross-sectional area of the individual wires.
The systems and methods of the present technology can include one or more features of the expandable member 210 to facilitate adhesion of the clot to the expandable member 210. For example, in some embodiments, some or all of the expandable member 210 can be coated with one or more highly conductive materials, such as gold, to improve clot adhesion. In some aspects of the present technology, a working length of the expandable member 210 may be coated with the conductive material while a non-working length of the expandable member 210 may be coated with an insulative material. As used herein, a “working length” can refer to a portion of the expandable member 210 configured to engage with a thrombus, and a “non-working length” can refer to those portions of the expandable member 210 that are not configured to engage with a thrombus (e.g., a proximally tapering region that is not intended to engage with a thrombus). In any case, a portion of the expandable member 210 may be coated with an insulative material. In some instances, insulative coating can improve resistance to corrosion of the expandable member 210. The insulative coating can also serve to focus electrical current to non-insulated regions, thereby achieving higher current density in desired portions which may enable improved clot adhesion.
The core member 112 and the interventional element 200 together may comprise a delivery electrode or conductive path, e.g., for transmitting current from the signal generator 102 to the treatment site. A second electrode or conductive path, e.g., for transmitting current from the treatment site to the signal generator 102, can be provided via any suitable approach, such as utilizing a return electrode carried by a catheter, or one or more external electrodes 132 (
In some embodiments, the treatment device 104 can be configured such that, when voltage is applied via the signal generator 102 and the interventional element 200 is placed in the presence of blood (or any other electrolytic medium), current flows from the interventional element 200, through the blood or medium, and to the negative electrode(s). Positive current delivered to the interventional element 200 can attract negatively charged constituents of the clot material, thereby enhancing the grip of the interventional element 200 on the clot material. This enables the interventional element 200 to be used to retrieve the clot material with reduced risk of losing grip on the thrombus or a piece thereof, which can migrate downstream and cause additional vessel blockages in areas of the brain that are more difficult to reach. In some examples, the polarity can be reversed, thereby negatively charging the interventional element 200. This can be useful to, for example, attract positively charged material to the interventional element 200 and/or to break up the clot material.
When current is supplied to the interventional element 200, electrical current will flow through the blood (or other medium) through exposed surfaces of the interventional element 200 that are electrically conductive. As such, current may flow through the electrodes 206 of the electrical engagement portion 202 but may not flow through the insulative regions 208 separating the electrodes 206 from one another. In some examples, the mechanical engagement portion 204 may not be electrically charged, either by providing an insulative coating over the mechanical engagement portion 204 or by coupling the mechanical engagement portion 204 and the electrical engagement portion 202 in such a way that the mechanical engagement portion 204 is not in electrical communication with the electrical engagement portion 202 and/or the core member 112. For instance, the connection point 213 between the core member 112 and the expandable member 210 can be configured such that electrical current traveling along the core member 112 does not pass through the connection point 213 to the expandable member. Additionally or alternatively, the expandable member 210 can be coated with an electrically insulative material along some or all of its length.
In some embodiments, at least a portion of the mechanical engagement portion 204 is electrically charged by the signal generator 102, such that when current is supplied by the signal generator 102, both the electrodes 206 of the electrical engagement portion 202 and the mechanical engagement portion 204 are electrically charged. In the illustrated example, the electrical engagement portion 202 and the mechanical engagement portion 204 may be charged with the same polarity (e.g., both positively charged, thereby promoting attraction of negatively charged blood constituents). In some examples, however, a separate conductive path can be provided between the signal generator 102 and the mechanical engagement portion 204 such that the electrical engagement portion 202 can be coupled to a first terminal of the signal generator 102 and the mechanical engagement portion 204 can be coupled to a second terminal of the signal generator. In such implementations, the separate conductive path can be provided alongside the core member 112 (e.g., as a separate conductive shaft running alongside the core member 112), within a lumen of the core member 112 (e.g., when the core member 112 comprises a hypotube), or any other suitable configuration.
In some embodiments, as shown in
In the example shown in
In the configuration shown in
Once the interventional element 200 has been released from the catheter 110, and the expandable member 210 is expanded, the expandable member 210 may grip the at least a portion of the clot material CM by virtue of its ability to mechanically interlock with the clot material CM. The signal generator 102, which is electrically coupled to the proximal end of the core member 112, can deliver a current to the interventional element 200 before or after the interventional element 200 has been released from the second catheter 110 into the blood vessel and/or expanded into the clot material CM. The electrical current can promote adhesion of the thrombus to the electrodes 206 of the electrical engagement portion 202 and also to the expandable member 210 (in implementations in which the expandable member 210 is in electrical communication with the signal generator 102). The interventional element 200 can be left in place or manipulated within the vessel V for a desired time period while the electrical signal is being delivered. Positive current delivered to the interventional element 200 can attract negatively charged constituents of the clot material CM to positively charged portions of the interventional element (e.g., the electrodes 206 and/or the expandable member 210), thereby enhancing the grip of the interventional element 200 on the clot material CM. This allows the interventional element 200 to be used to retrieve the clot material CM with reduced risk of losing grip on the thrombus or a piece thereof, which can migrate downstream and cause additional vessel blockages in areas of the brain that are more difficult to reach.
While the interventional element 200 is engaged with the clot material CM, the core member 112 can be pulled proximally until the interventional element 200 with the engaged clot material CM is positioned within a surrounding catheter (e.g., the first and/or third catheter). The catheters, interventional element 200, and associated clot material CM may then be withdrawn from the patient. During this retraction, the interventional element 200 can grip the clot material CM electrically and/or electrostatically. (As used herein with reference to gripping or retrieving thrombus or other vascular/luminal material, or to apparatus for this purpose, “electrical” and its derivatives will be understood to include “electrostatic” and its derivatives.) Accordingly, the interventional element 200 can maintain an enhanced or electrically and/or electrostatically enhanced grip on the clot material CM during retraction. In other embodiments, the signal generator 102 may cease delivery of electrical signals to the interventional element 200 prior to retraction of the interventional element 200 with respect to the vessel V. In some embodiments, the interventional element 200 and clot material CM form a removable, integrated thrombus-device mass wherein the connection of the thrombus to the device is electrically enhanced, e.g., via the application of current as discussed herein.
One or more optional processes may be performed before, during, and/or after deployment of the interventional element 200. For example, in some methods of the present technology, a guidewire (not shown) may be advanced to the treatment site and pushed through the clot material CM until a distal portion of the guidewire is distal of the clot material CM. The guidewire may be advanced through one or more of the first, second, and/or third catheters, and one or more of the catheters may be advanced over the guidewire. The guidewire may be insulated along at least a portion of its length (e.g., with parylene, PTFE, etc.), with exposed portions permitting electrical communication with the signal generator 102 and the interventional element 200. For example, in some embodiments a distal portion of the guidewire may be exposed and the guidewire may be positioned at the treatment site such that the exposed portion of the guidewire is distal of the clot material CM. A proximal end of the guidewire may be coupled to the signal generator such that the exposed portion of the guidewire functions as a return electrode. In some embodiments, the guidewire may be coupled to the positive terminal of the power source and the exposed portion functions as a delivery electrode. The guidewire may be used as a delivery or return electrode with any delivery or return electrode carried by any component of the system (e.g., one or more of the first, second, and/or third catheters, the interventional element 200, etc.).
In some methods a fluid may be delivered to the treatment site via the second and/or third catheter while current is being delivered to the interventional element 200. Fluid delivery may occur before or while the interventional element 200 is engaging the thrombus, and may coincide with the entire duration of current delivery or just a portion thereof. Additionally or alternatively, it may be especially beneficial to arrest flow (e.g., via a flow arrest element on the first or second catheter 108, 110) while the interventional element 200 is charged, and while expanding the interventional element 200 within the thrombus and/or when withdrawing the thrombus proximally.
Although the presence of blood flow at the treatment site is believed to reduce adhesion between an electrically charged interventional element and a blood clot, infusion of a fluid having a higher ion concentration than blood can increase the electrical conductivity at the treatment site, thereby providing an improved environment for electrically enhanced clot adhesion as compared to the presence of blood alone. In some embodiments, infusion of the fluid may occur in the presence of blood flow, or without blood flow present (the latter condition being induced, for example, by inflation of an expandable flow-arrest element on a catheter). Suitable fluids include, for example, saline, contrast solution, and other fluids having a higher ion concentration than blood. Additionally, the delivery of fluid at the treatment site may also reduce new clot formation on the interventional element 200, which may occur in the presence of blood and direct or pulsatile electric current.
In some instances aspiration may be applied to the treatment site via an aspiration catheter. For example, following deployment of the interventional element 200, the second catheter 110 can be retracted and removed from the lumen of a third catheter. The treatment site can then be aspirated via the third catheter, for example via a suction source (such as suction source 115) coupled to a proximal portion of the third catheter. In some embodiments, following expansion of the interventional element 200, the treatment site is aspirated concurrently with supplying electrical energy to the interventional element 200 via the signal generator 102. By combining aspiration with the application of electrical energy, any newly formed clots (e.g., any clots formed that are attributable at least in part to the application of electrical energy), or any clot pieces that are broken loose during the procedure, can be pulled into the third catheter, thereby preventing any such clots from being released downstream of the treatment site. As a result, concurrent aspiration may permit the use of higher power or current levels delivered to the interventional element 200 without risking deleterious effects of new clot formation. Additionally, aspiration can capture any gas bubbles formed along the interventional element 200 or other component during application of electrical energy to the interventional element 200, which can improve patient safety during the procedure.
Although the waveforms and other power delivery parameters disclosed herein can be used with the devices and methods described above with respect to
While applying a continuous uniform direct current (DC) electrical signal to positively charge the interventional element and/or catheter can improve attachment to the thrombus, this can risk damage to surrounding tissue (e.g., ablation), and sustained current at a relatively high level may also be thrombogenic (i.e., may generate new clots). For achieving effective clot-grabbing without ablating tissue or generating substantial new clots at the treatment site, periodic waveforms have been found to be particularly useful. Without being bound by theory, the clot-adhesion effect appears to be most closely related to the peak current of the delivered electrical signal. Periodic waveforms can advantageously provide the desired peak current without delivering excessive total energy or total electrical charge. Periodic, non-square waveforms in particular are well suited to deliver a desired peak current while reducing the amount of overall delivered energy or charge as compared to either uniform applied current or square waveforms.
Periodic waveforms that can be used with the devices and methods described above with respect to
The waveform shape (e.g., pulse width, duty cycle, amplitude) and length of time can each be selected to achieve desired power delivery parameters, such as overall electrical charge, total energy, and peak current delivered to the interventional element and/or catheter. In some embodiments, the overall electrical charge delivered to the interventional element and/or catheter can be between about 30-1200 mC, or between about 120-600 mC. According to some embodiments, the total electrical charge delivered to the interventional element and/or catheter may be less than 600 mC, less than 500 mC, less than 400 mC, less than 300 mC, less than 200 mC, or less than 100 mC.
In some embodiments, the total energy delivered to the interventional element and/or aspiration catheter can be between about 0.75-24,000 mJ, or between about 120-24,000 mJ, or between about 120-5000 mJ. According to some embodiments, the total energy delivered to the interventional element and/or aspiration catheter may be less than 24,000 mJ, less than 20,000 mJ, less than 15,000 mJ, less than 10,000 mJ, less than 5,000 mJ, less than 4,000 mJ, less than 3,000 mJ, less than 2000 mJ, less than 1,000 mJ, less than 900 mJ, less than 800 mJ, less than 700 mJ, less than 600 mJ, less than 500 mJ, less than 400 mJ, less than 300 mJ, or less than 200 mJ, or less than 120 mJ, or less than 60 mJ, or less than 48 mJ, or less than 30 mJ, or less than 12 mJ, or less than 6 mJ, or less than 1.5 mJ.
In some embodiments, the peak current delivered can be between about 0.5-20 mA, or between about 0.5-5 mA. According to some embodiments, the peak current delivered may be greater than 0.5 mA, greater than 1 mA, greater than 1.5 mA, greater than 2 mA, greater than 2.5 mA, or greater than 3 mA.
The duration of power delivery is another important parameter that can be controlled to achieve the desired clot-adhesion effects without damaging tissue at the treatment site or generating new clots. In at least some embodiments, the total energy delivery time can be no more than 1 minute, no more than 2 minutes, no more than 3 minutes, no more than 4 minutes, no more than 5 minutes, or between 1 and 5 minutes. According to some embodiments, the total energy delivery time may be less about 30 seconds, less than about 1 minute, less than about 90 seconds, or less than about 2 minutes. As used herein, the “total energy delivery time” refers to the time period during which the waveform is supplied to the interventional element and/or catheter (including those periods of time between pulses of current).
The duty cycle of the applied electrical signal can also be selected to achieve the desired clot-adhesion characteristics without ablating tissue or promoting new clot formation. In some embodiments, the duty cycle can be between about 5% about 99% or between about 5% to about 20%. According to some embodiments, the duty cycle may be about 10%, about 20%, about 30%, about 40%, or about 50%. In yet other embodiments, a constant current may be used, in which the duty cycle is 100%. For 100% duty cycle embodiments, a lower time or current may be used to avoid delivering excess total energy to the treatment site.
Although many of the embodiments are described herein with respect to devices, systems, and methods for treating a cerebral or intracranial embolism, other applications and other embodiments in addition to those described herein are within the scope of the technology. For example, the systems and methods of the present technology may be used to remove emboli from body lumens other than blood vessels (e.g., the digestive tract, etc.) and/or may be used to remove emboli from blood vessels outside of the brain (e.g., pulmonary, abdominal, cervical, or thoracic blood vessels, or peripheral blood vessels including those within the legs or arms, etc.). In addition, the systems and methods of the present technology may be used to remove luminal obstructions other than clot material (e.g., plaque, resected tissue, foreign material, kidney stones, etc.).
This disclosure is not intended to be exhaustive or to limit the present technology to the precise forms disclosed herein. Although specific embodiments are disclosed herein for illustrative purposes, various equivalent modifications are possible without deviating from the present technology, as those of ordinary skill in the relevant art will recognize. In some cases, well-known structures and functions have not been shown and/or described in detail to avoid unnecessarily obscuring the description of the embodiments of the present technology. Although steps of methods may be presented herein in a particular order, in alternative embodiments the steps may have another suitable order. Similarly, certain aspects of the present technology disclosed in the context of particular embodiments can be combined or eliminated in other embodiments. Furthermore, while advantages associated with certain embodiments may have been disclosed in the context of those embodiments, other embodiments can also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages or other advantages disclosed herein to fall within the scope of the present technology. Accordingly, this disclosure and associated technology can encompass other embodiments not expressly shown and/or described herein.
Throughout this disclosure, the singular terms “a,” “an,” and “the” include plural referents unless the context clearly indicates otherwise. Similarly, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in reference to a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of the items in the list. Additionally, the terms “comprising” and the like are used throughout this disclosure to mean including at least the recited feature(s) such that any greater number of the same feature(s) and/or one or more additional types of features are not precluded. Directional terms, such as “upper,” “lower,” “front,” “back,” “vertical,” and “horizontal,” may be used herein to express and clarify the relationship between various elements. It should be understood that such terms do not denote absolute orientation. Reference herein to “one embodiment,” “an embodiment,” or similar formulations means that a particular feature, structure, operation, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present technology. Thus, the appearances of such phrases or formulations herein are not necessarily all referring to the same embodiment. Furthermore, various particular features, structures, operations, or characteristics may be combined in any suitable manner in one or more embodiments.
