Patent Description:
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.

The invention is defined by independent claims <NUM> and <NUM>. No methods of surgery or treatment are claimed. 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 treatment systems of the present technology provide an interventional element and a current generator configured to positively charge the interventional element during one or more stages of a thrombectomy procedure. For example, the current 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 treatment system includes a core member extending between the current generator and the interventional element. A delivery electrode may be integrated into the core member and/or interventional element, and the treatment system further includes a return electrode that may be disposed at a number of different locations. For example, the return electrode can be a needle, a grounding pad, a conductive element carried by a one or more catheters of the treatment system, a guide wire, and/or any other suitable conductive element configured to complete an electrical circuit with the delivery electrode and the extracorporeally positioned current generator. When the interventional element is placed in the presence of blood (or any other electrolytic medium) and voltage is applied at the terminals of the current generator, current flows along the core member to the interventional element, through the blood, and to the return electrode, thereby positively charging at least a portion of the interventional element and adhering clot material thereto.

One approach to delivering current to an interventional element is to conduct current along a core member coupled to a proximal end of the interventional element. However, the inventors have discovered that this approach can lead to disadvantageous concentration of electrical charge along a proximal portion of the interventional element, with insufficient charge density in more distal portions of the interventional element (e.g., along some or all of the working length of the interventional element). This is particularly true of an interventional element having a proximal portion that tapers to a connection point with the core member. This concentration of current in the proximal portion can reduce the efficacy of electrostatic enhancement of clot adhesion, as the mechanical clot engagement occurs primarily at a location distal to the region at which the charge density is greatest. Additionally, when used in an aqueous chloride environment such as the blood, hydrogen and chlorine gas bubbles can form along the surface of the interventional element in areas with high surface charge density (e.g., along a proximal portion of the interventional element).

The treatment systems and methods of the present technology can overcome these and other problems by varying features of the interventional element to achieve the desired electrical properties. For example, in some embodiments, some or all of the interventional element can be surface treated, coated, or otherwise modified to alter its electrical properties. The electrical properties of the interventional element can be varied spatially across different regions of the interventional element so as to improve the electrical charge distribution over its surface during use in the body. In some embodiments, a proximal region of the interventional element can be at least partially electrically insulated such that the distal region is more electrically conductive than the proximal region. This variation in conductivity can help achieve a more desirable charge distribution across the interventional element, and can avoid the undesirable concentration of electrical charge at a proximal region as described above. In various embodiments, some or all of the interventional element can be electrically insulated by surface treating, coating, or otherwise modifying the interventional element to reduce its electrical conductivity.

According to some aspects of the present technology, electrochemical anodization can be utilized to alter the electrical properties of the interventional element. For example, anodization can be used to increase a thickness of the naturally occurring oxide layer disposed over the interventional element. As the oxide layer thickness increases, the surface conductivity of the interventional element decreases, thereby at least partially electrically insulating that portion of the interventional element. In some embodiments, anodization can be used to achieve varying thicknesses of an oxide layer over the surface of the interventional element, such as by having a thicker oxide layer in a proximal region and a thinner oxide layer in a distal region. By tuning the thickness of the oxide layer over the interventional element, a favorable electrical charge distribution can be achieved (e.g., by achieving a more uniform charge distribution and/or by concentrating charge distribution into distal regions or along the working length of the interventional element).

Additionally or alternatively to insulating a portion of the interventional element, the distal region (or any other suitable portion of the interventional element) can be coated, surface treated, or otherwise modified to increase its conductivity. For example, a distal region can be coated with gold or other highly conductive materials so as to increase the electrical conductivity of the distal region.

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 drawings.

Background art: <CIT> and <CIT> disclose a thrombectomy system <CIT> discloses a tissue localizing device.

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.

The present technology provides devices, systems, and methods for removing clot material from a blood vessel lumen. Although many of the embodiments are described below 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 treatment systems and methods of the present technology may be used to remove emboli from corporeal 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 treatment 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, etc.).

<FIG> illustrates a view of an electrically enhanced treatment system <NUM> according to one or more embodiments of the present technology. As shown in <FIG>, the treatment system <NUM> can include a current generator <NUM> and a treatment device <NUM> having a proximal portion 40a configured to be coupled to the current generator <NUM> and a distal portion 40b configured to be intravascularly positioned within a blood vessel (such as an intracranial blood vessel) at a treatment site at or proximate a thrombus. The treatment device <NUM> includes an interventional element <NUM> at the distal portion 10b, a handle <NUM> at the proximal portion 10a, and a plurality of elongated shafts or members extending therebetween. For example, in some embodiments, such as that shown in <FIG>, the treatment device <NUM> includes a first catheter <NUM> (such as a balloon guide catheter), a second catheter <NUM> (such as a distal access catheter or aspiration catheter) configured to be slidably disposed within a lumen of the first catheter <NUM>, a third catheter <NUM> (such as a microcatheter) configured to be slidably disposed within a lumen of the second catheter <NUM>, and a core member <NUM> configured to be slidably disposed within a lumen of the third catheter <NUM>. In some embodiments, the treatment device <NUM> does not include the second catheter <NUM>. The first catheter <NUM> can be coupled to the handle <NUM>, which provides proximal access to the core member <NUM> that engages the interventional element <NUM> at a distal end thereof. The current generator <NUM> may be coupled to a proximal portion of one or more of the core member <NUM>, the third catheter <NUM>, the second catheter <NUM>, and/or the first catheter <NUM> to provide an electrically charged environment at the distal portion 40b of the treatment device <NUM>, as described in more detail below.

In some embodiments, the treatment system <NUM> includes a suction source <NUM> (e.g., a syringe, a pump, etc.) configured to be fluidly coupled (e.g., via a connector <NUM>) to a proximal portion of one or more of the first catheter <NUM>, the second catheter <NUM>, and/or the third catheter <NUM> to apply negative pressure therethrough. In some embodiments, the treatment system <NUM> includes a fluid source <NUM> (e.g., a fluid reservoir, a syringe, pump, etc.) configured to be fluidly coupled (e.g., via the connector <NUM>) to a proximal portion of one or more of the first catheter <NUM>, the second catheter <NUM>, and/or the third catheter <NUM> to supply fluid (e.g., saline, contrast agents, a drug such as a thrombolytic agent, etc.) to the treatment site.

According to some embodiments, the current generator <NUM> can include an electrical generator configured to output medically useful electric current. <FIG> are schematic views of different embodiments of the current generator <NUM>. With reference to <FIG>, the current generator <NUM> can include a power source <NUM>, a first terminal <NUM>, a second terminal <NUM>, and a controller <NUM>. The controller <NUM> includes a processor <NUM> coupled to a memory <NUM> 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 <NUM> to deliver electric current according to certain parameters provided by the software, code, etc. The power source <NUM> of the current generator <NUM> 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 current generator <NUM> 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 current generator <NUM> can provide a voltage of about <NUM> volts to about <NUM> volts and a current of about <NUM> mA to about <NUM> mA.

<FIG> illustrates another embodiment of the current generator <NUM>, in which the controller <NUM> of <FIG> is replaced with drive circuitry <NUM>. In this embodiment, the current generator <NUM> can include hardwired circuit elements to provide the desired waveform delivery rather than a software-based generator of <FIG>. The drive circuitry <NUM> can include, for example, analog circuit elements (e.g., resistors, diodes, switches, etc.) that are configured to cause the power source <NUM> to deliver electric current via the first and second terminals <NUM>, <NUM> according to the desired parameters. For example, the drive circuitry <NUM> can be configured to cause the power source <NUM> to deliver periodic waveforms via the first and second terminals <NUM>, <NUM>.

As noted above, the current generator <NUM> may be coupled to a proximal portion of the core member <NUM>, and/or a proximal portion of the third catheter <NUM>, the second catheter <NUM>, and/or first catheter <NUM> to provide an electric current to the interventional element <NUM>. For example, in some embodiments, both terminals of the current generator <NUM> are coupled to the core member <NUM> such that the core member <NUM> functions as both a delivery electrode or conductive path (i.e., transmitting current from the current generator <NUM> to the treatment site) and a return electrode or conductive path (i.e., transmitting current from the treatment site to the current generator <NUM>) (described in greater detail below with reference to <FIG>). In other embodiments, the return electrode can be separate from the core member <NUM>. For example, the return electrode can be carried by one or more of the third catheter <NUM>, the second catheter <NUM>, and/or first catheter <NUM>. In some embodiments, the return electrode can be provided via one or more external electrodes <NUM> (<FIG>), such as a needle puncturing the patient or a grounding pad applied to the patient's skin. In some embodiments, the return electrode can be an insulated guide wire having an exposed, electrically conductive portion at its distal end.

<FIG> is a side schematic view of a portion of the treatment device <NUM> shown in <FIG>. The system <NUM> can include multiple (e.g., two or more), distinct conductive paths or channels for passing electrical current along the system <NUM>. The interventional element <NUM> can serve as one electrode (e.g., the delivery electrode) in electrical communication with a conductive path integrated into the core member <NUM>. Another of the conductive paths of the system <NUM> can be in electrical communication with another electrode (e.g., a return electrode). The various embodiments of the core member <NUM> can be sized for insertion into a bodily lumen, such as a blood vessel, and can be configured to push and pull a device such as the interventional element <NUM> along the bodily lumen.

As noted above, the interventional element <NUM> can serve as the delivery electrode and be electrically coupled to a positive terminal of the current generator <NUM> (<FIG>). As shown in <FIG>, in some embodiments, the core member <NUM> can include an elongate conductive shaft <NUM> (e.g., a pushwire) extending along the length of the core member <NUM>. The shaft can be in electrical communication with the current generator <NUM> (<FIG>) at its proximal end and the interventional element <NUM> at its distal end. The shaft can be insulated along at least a portion of its length, with exposed portions permitting electrical communication with the current generator <NUM> and the interventional element <NUM>.

The return electrode(s) can assume a variety of configurations in different embodiments. For example, in some embodiments, the return electrode is an external electrode <NUM> (<FIG>), such as a needle or grounding pad that is applied to a patient's skin. The needle or grounding pad can be coupled via one or more leads to the current generator <NUM> to complete the electrical circuit. In some embodiments, the return electrode is carried by a surrounding catheter (e.g., third catheter <NUM>, second catheter <NUM>, and/or first catheter <NUM>), as described in more detail below.

According to some embodiments, for example as shown in <FIG>, the catheters <NUM>, <NUM>, and <NUM> can each be formed as a generally tubular member extending along and about a central axis and terminating in a respective distal end <NUM>, <NUM>, and <NUM>. According to some embodiments, the third catheter <NUM> is generally constructed to track over a conventional guidewire in the cervical anatomy and into the cerebral vessels associated with the brain and may also be chosen according to several standard designs that are generally available. Accordingly, the third catheter <NUM> can have a length that is at least <NUM> long, and more particularly may be between about <NUM> and about <NUM> long. Other designs and dimensions are contemplated.

The second catheter <NUM> can be sized and configured to be slidably receive the third catheter <NUM> therethrough. As noted above, the second catheter <NUM> can be coupled at a proximal portion to a suction source <NUM> (<FIG>) such as a pump or syringe in order to supply negative pressure to a treatment site. The first catheter <NUM> can be sized and configured to slidably receive both the second catheter <NUM> and the third catheter <NUM> therethrough. In some embodiments, the first catheter <NUM> is a balloon-guide catheter having an inflatable balloon or other expandable member that can be used to anchor the first catheter <NUM> with respect to a surrounding vessel. As described in more detail below with respect to Figures 6A-<NUM>, in operation the first catheter <NUM> can first be advanced through a vessel and then a balloon can be expanded to anchor the first catheter <NUM> in place and/or arrest blood flow from areas proximal of the balloon. Next, the second catheter <NUM> can be advanced through the first catheter <NUM> until its distal end <NUM> extends distally beyond the distal end <NUM> of the first catheter <NUM>. The second catheter <NUM> can be positioned such that its distal end <NUM> is adjacent a treatment site (e.g., a site of a blood clot within the vessel). The third catheter <NUM> may then be advanced through the second catheter <NUM> until its distal end <NUM> extends distally beyond the distal end <NUM> of the second catheter <NUM>. The interventional element <NUM> may then be advanced through the third catheter <NUM> for delivery to the treatment site.

According to some embodiments, the bodies of the catheters <NUM>, <NUM>, and <NUM> 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.

According to some embodiments, an electrode <NUM> is provided at a distal end region of the third catheter <NUM>. The electrode <NUM> can form an annular ring that extends entirely circumferentially about the central axis of the third catheter <NUM>. Alternatively or in combination, the electrode <NUM> can extend less than entirely circumferentially around the third catheter <NUM>. For example, the electrode <NUM> may be entirely disposed on one radial side of the central axis. By further example, the electrode <NUM> may provide a plurality of discrete, noncontiguous electrode sections about the central axis. Such sections of the electrode <NUM> 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 the sections to function independently if desired. The electrode <NUM> can be a band, a wire, or a coil embedded in the wall of the third catheter <NUM>. According to some embodiments, the electrode <NUM> can be longitudinally separated from the distal end <NUM> of the third catheter <NUM> by a non-conductive portion of the third catheter <NUM>. Alternatively, a distal portion of the electrode <NUM> can extend to the distal end <NUM> of the third catheter <NUM>, such that the electrode <NUM> forms a portion of the distal end <NUM>. According to some embodiments, an inner surface of the electrode <NUM> can be flush with an inner surface of the third catheter <NUM>. Alternatively or in combination, the inner surface of the electrode <NUM> can extend more radially inwardly relative to the inner surface of the third catheter <NUM> (e.g., providing a "step"). Alternatively or in combination, the inner surface of the electrode <NUM> can extend less radially inwardly relative to the inner surface of the third catheter <NUM> (e.g., be recessed into the body). According to some embodiments, the electrode <NUM> can be surrounded radially by an outer section of the third catheter <NUM> to provide insulation from an external environment. In some embodiments, an outer surface of the electrode <NUM> can be flush with an outer surface of the third catheter <NUM> and can provide an exposed, radially outwardly facing electrode surface. In such instances, a radially inner section of the third catheter <NUM> can provide insulation from the environment within the lumen of the third catheter <NUM>.

The electrode <NUM> can include one or more rings, one or more coils or other suitable conductive structures, and can each form at least one surface (e.g., an inner surface or an outer surface) that is exposed and configured for electrical activity or conduction. The electrode <NUM> can have a fixed inner diameter or size, or a radially expandable inner diameter or size. In some embodiments, the electrode <NUM> is a "painted" electrode. The electrode can include platinum, platinum alloys (e.g., <NUM>% platinum and <NUM>% tungsten, <NUM>% platinum and <NUM>% iridium), gold, cobalt-chromium, stainless steel (e.g., <NUM> or <NUM>), nitinol, and combinations thereof, or any suitable conductive materials, metals or alloys.

In some embodiments, the electrode <NUM> can be a separate expandable member coupled to an outer surface of the third catheter <NUM>, for example a braid, stent, or other conductive element coupled to an outer surface of the distal portion of the third catheter <NUM>. In some embodiments, the electrode can be part of a flow-arrest element such as an expandable braid coupled to an occlusion balloon.

According to some embodiments, the electrode <NUM> can be electrically connected to the current generator <NUM> via a conductive lead <NUM>. The conductive lead <NUM> can extend proximally along or within the wall of the third catheter <NUM> to or beyond the proximal end of the third catheter <NUM>. The conductive lead <NUM> can include more than one conductive path extending within the walls of the third catheter <NUM>. According to some embodiments, the conductive lead <NUM> can form a helical coil along or within at least a portion of the third catheter <NUM>. Alternatively or in combination, the conductive lead <NUM> can form a braided, woven, or lattice structure along or within at least a portion of the third catheter <NUM>. In some embodiments, the conductive lead <NUM> can be a conductive element (e.g., a wire, coil, etc.) wrapped around an external surface of the third catheter <NUM>. In such instances, the conductive lead <NUM> can be coated with an insulative material along at least a portion of its length. The insulative material can be, for example, Parylene, PTFE, or other suitable insulative material.

In some embodiments, the second catheter <NUM> and/or the first catheter <NUM> can be similarly equipped with corresponding electrodes instead of or in addition to the third catheter <NUM> or the core member <NUM>. For example, the second catheter <NUM> may include an electrode <NUM> disposed at a distal end region of the second catheter <NUM>. The electrode <NUM> can be electrically connected to the current generator <NUM> (<FIG>) via a conductive lead <NUM> which extends proximally along the second catheter <NUM>. The configuration of the electrode <NUM> and the corresponding conductive lead <NUM> can be similar to any of the variations described above with respect to the electrode <NUM> and the conductive lead <NUM> of the third catheter <NUM>.

In some embodiments, the first catheter <NUM> includes an electrode <NUM> disposed at a distal end region of the first catheter <NUM>. The electrode <NUM> can be electrically connected to the current generator <NUM> (<FIG>) via a conductive lead <NUM> which extends proximally along the first catheter <NUM>. The configuration of the electrode <NUM> and the corresponding conductive lead <NUM> can be similar to any of the variations described above with respect to the electrode <NUM> and the conductive lead <NUM> of the third catheter <NUM>.

In various embodiments, the system can include any combination of the electrodes <NUM>, <NUM>, and <NUM> described above. For example, the system may include the electrode <NUM> and the corresponding conductive lead <NUM> of the third catheter <NUM>, while the second catheter <NUM> and the first catheter <NUM> may be provided with no electrodes or conductive leads therein. In other embodiments, the system may only include the electrode <NUM> of the second catheter <NUM>, while the third catheter <NUM> and the first catheter <NUM> may be provided with no electrodes or conductive leads therein. In still other embodiments, the system may include only the electrode <NUM> of the first catheter <NUM>, while the third catheter <NUM> and the second catheter <NUM> are provided with no electrodes or corresponding conductive leads therein. In some embodiments, any two of the catheters <NUM>, <NUM>, or <NUM> can be provided with electrodes and corresponding leads, while the remaining catheter may have no electrode or conductive lead therein.

In the configuration illustrated in <FIG>, one or more of electrodes <NUM>, <NUM>, or <NUM> can be coupled to a negative terminal of the current generator <NUM>, while the interventional element <NUM> can be coupled to the positive terminal of the current generator <NUM> via the core member <NUM>. As a result, when voltage is applied at the terminals and the interventional element <NUM> placed in the presence of blood (or any other electrolytic medium), current flows from the interventional element <NUM>, through the blood or medium, and to the return electrode. The return electrode may a conductive element carried by one or more of the catheters <NUM>, <NUM>, or <NUM> as described above, or the core member <NUM>, or in some embodiments the return electrode can be an external electrode <NUM> (<FIG>) such as needle or grounding pad.

In some embodiments, one or more catheters carrying an electrode can be used without an electrically coupled interventional element <NUM>. In various embodiments, the interventional element <NUM> may be omitted altogether (as in Figures 6A-6B described below), or the interventional element <NUM> may be included but may not be electrically coupled to the current generator <NUM>. In such cases, a catheter-based electrode (e.g., the electrode <NUM> carried by the third catheter <NUM>, the electrode <NUM> carried by the second catheter <NUM>, or the electrode <NUM> carried by the first catheter <NUM>) can function as the delivery electrode, and a separate return electrode can be provided either in the form of another catheter-based electrode (either carried by the same catheter or carried by another catheter) or as an external electrode (e.g., a needle or grounding pad). In instances in which a single catheter carries two electrodes, one electrode may be provided on an exterior surface of the catheter while the other electrode may be provided on an inner surface of the catheter. For example, the second catheter <NUM> may include a delivery electrode in the form of a conductive band disposed on an inner surface of the catheter <NUM>, in addition to a return electrode in the form of a conductive band disposed on an outer surface of the catheter <NUM>.

As described in more detail in <FIG>, in some embodiments the return electrode can be integrated into the core member <NUM> of the treatment system <NUM>, such that the core member <NUM> carries two separate conductive paths along its length. <FIG> is a side schematic cross-sectional view of a portion of the treatment system shown in <FIG>, in accordance with some embodiments. As shown in <FIG>, the core member <NUM> includes an elongate conductive shaft <NUM> and an elongate tubular member <NUM> having a lumen through which the shaft <NUM> extends. The shaft <NUM> has a distal portion <NUM>, and the tubular member <NUM> has a distal portion <NUM>. Both the shaft <NUM> and the tubular member <NUM> are electrically conductive along their respective lengths. In some embodiments, the positions of the shaft <NUM> and the tubular member <NUM> are fixed relative to one another. For example, in some embodiments the shaft <NUM> is not slidable or rotatable with respect to the tubular member <NUM> such that the core member <NUM> can be pushed or pulled without relative movement between the shaft <NUM> and the tubular member <NUM> and/or other individual components of the core member <NUM>.

In some embodiments, the shaft <NUM> can be a solid pushwire, for example a wire made of Nitinol, stainless steel, or other metal or alloy. The shaft <NUM> may be thinner than would otherwise be required due to the additional structural column strength provided by the surrounding tubular member <NUM>. The tubular member <NUM> can be a hollow wire, hypotube, braid, coil, or other suitable member(s), or a combination of wire(s), tube(s), braid(s), coil(s), etc. In some embodiments, the tubular member <NUM> can be a laser-cut hypotube having a spiral cut pattern (or other pattern of cut voids) formed in its sidewall along at least a portion of its length. The tubular member <NUM> can be made of stainless steel (e.g., <NUM> SS), Nitinol, and/or other alloy. In at least some embodiments, the tubular member <NUM> can have a laser cut pattern to achieve the desired mechanical characteristics (e.g., column strength, flexibility, kink-resistance, etc.).

The core member <NUM> can also include an adhesive or a mechanical coupler such as a crimped band or marker band <NUM> disposed at the distal end of the core member <NUM>, and the marker band <NUM> can optionally couple the distal end of the core member <NUM> to the interventional element <NUM>. The marker band <NUM> can be radiopaque, for example including platinum or other radiopaque material, thereby enabling visualization of the proximal end of the interventional element <NUM> under fluoroscopy. In some embodiments, additional radiopaque markers can be disposed at various locations along the treatment system <NUM>, for example along the shaft <NUM>, the tubular member <NUM>, or the interventional element <NUM> (e.g., at the distal end, or along the length, of the interventional element <NUM>).

In at least some embodiments, the core member <NUM> also includes a first insulating layer or material <NUM> extending between the shaft <NUM> and the surrounding tubular member <NUM>. The first insulating material <NUM> can be, for example, PTFE (polytetrafluoroethylene or TEFLON™) or any other suitable electrically insulating coating (e.g., polyimide, oxide, ETFE-based coatings, or any suitable dielectric polymer). In some embodiments, the first insulating material <NUM> extends along substantially the entire length of the shaft <NUM>. In some embodiments, the first insulating material <NUM> separates and electrically insulates the shaft <NUM> and the tubular member <NUM> along the entire length of the tubular member <NUM>. In some embodiments, the first insulating material <NUM> does not cover the proximal-most portion of the shaft <NUM>, providing an exposed region of the shaft to which the current generator <NUM> (<FIG>) can be electrically coupled. In some embodiments, for example, the first insulating material <NUM> terminates proximally at the proximal terminus of the shaft, and the current generator <NUM> (<FIG>) can electrically couple to the shaft <NUM> at its proximal terminus, for example using a coaxial connector.

The core member <NUM> can additionally include a second insulating layer or material <NUM> surrounding the tubular member <NUM> along at least a portion of its length. The second insulating layer <NUM> can be, for example, PTFE or any other suitable electrically insulative coating (e.g., polyimide, oxide, ETFE based coatings or any suitable dielectric polymer). In some embodiments, the distal portion <NUM> of the tubular member <NUM> is not covered by the second insulating layer <NUM>, leaving an exposed conductive surface at the distal portion <NUM>. In some embodiments, the length of the exposed distal portion <NUM> of the tubular member <NUM> can be at least (or equal to) <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more inches (To be considered for the whole description: <NUM> inch ≈ <NUM>,<NUM>). In some embodiments, the length of the exposed distal portion <NUM> of the tubular member <NUM> can be between at least <NUM> and <NUM> inches, or between <NUM> inches and <NUM> inches, or between <NUM> and <NUM> inches, or between <NUM> and <NUM> inches, or about <NUM> inches. This exposed portion of the distal portion <NUM> of the tubular member <NUM> provides a return path for current supplied to the delivery electrode (e.g. the entirety or a portion of the interventional element <NUM>), as described in more detail below. In some embodiments, the second insulating material <NUM> does not cover the proximal-most portion of the tubular member <NUM>, providing an exposed region of the tubular member <NUM> to which the current generator <NUM> (<FIG>) can be electrically coupled. In some embodiments, the second insulating material <NUM> proximally terminates at the proximal terminus of the tubular member <NUM>, and the current generator <NUM> can electrically couple to the tubular member <NUM> at its proximal terminus, for example using a coaxial connector.

The core member <NUM> can also include a retraction marker in the proximal portion of the tubular member <NUM>. The retraction marker can be a visible indicator to guide a clinician when proximally retracting an overlying catheter with respect to the core member <NUM>. For example, the retraction marker can be positioned such that when a proximal end of the overlying catheter is retracted to be positioned at or near the retraction marker, the distal portion <NUM> of the tubular member <NUM> is positioned distally beyond a distal end of the catheter. In this position, the exposed distal portion <NUM> of the tubular member <NUM> is exposed to the surrounding environment (e.g., blood, tissue, etc.), and can serve as a return electrode for the core member <NUM>.

The proximal end of the shaft <NUM> can be electrically coupled to the positive terminal of the current generator <NUM>, and the proximal end of the tubular member <NUM> can be electrically coupled to the negative terminal of the current generator <NUM>. During operation, the treatment system <NUM> provides an electrical circuit in which current flows from the positive terminal of the current generator <NUM>, distally through the shaft <NUM>, the interventional element <NUM>, and the surrounding media (e.g., blood, tissue, thrombus, etc.) before returning back to the exposed distal portion <NUM> of the tubular member, proximally through the tubular member <NUM>, and back to the negative terminal of the current generator <NUM> (<FIG>).

As noted above, the current generator <NUM> (<FIG>) can include a power source and either a processor coupled to a memory that stores instructions for causing the power source to deliver electric current according to certain parameters, or hardwired circuit elements configured to deliver electric current according to the desired parameters. The current generator <NUM> may be integrated into the core member <NUM> or may be removably coupled to the core member <NUM>, for example via clips, wires, plugs or other suitable connectors. Particular parameters of the energy provided by the current generator <NUM> are described in more detail below with respect to Figures 7A-7E.

In certain embodiments, the polarities of the current generator <NUM> can be switched, so that the negative terminal is electrically coupled to the shaft <NUM> and the positive terminal is electrically coupled to the tubular member <NUM>. This can be advantageous when, for example, attempting to attract predominantly positively charged material to the interventional element <NUM>, or when attempting to break up a clot rather than grasp it with an interventional element. In some embodiments alternating current (AC) signals may be used rather than DC. In certain instances, AC signals may advantageously help break apart a thrombus or other material.

Referring still to <FIG>, in some embodiments the interventional element <NUM> can be a metallic or electrically conductive thrombectomy device. The interventional element <NUM> can have a low-profile, constrained or compressed configuration (not shown) for intravascular delivery to the treatment site within the third catheter <NUM>, and an expanded configuration for securing and/or engaging clot material and/or for restoring blood flow at the treatment site. The interventional element <NUM> has a proximal end portion 100a that may be coupled to the core member <NUM> and a distal end portion 100b. The interventional element <NUM> further includes an open cell framework or body <NUM> and a coupling region <NUM> extending proximally from the body <NUM>. In some embodiments, the body <NUM> of the interventional element <NUM> can be generally tubular (e.g., cylindrical), and the proximal end portion 100a of the interventional element <NUM> can taper proximally to the coupling region <NUM>.

In various embodiments, the interventional element <NUM> can take any number of forms, for example a removal device, a thrombectomy device, or other suitable medical device. For example, in some embodiments the interventional element <NUM> may be a stent and/or stent retriever, such as Medtronic's Solitaire' Revascularization Device, Stryker Neurovascular's Trevo® ProVue™ Stentriever, or other suitable devices. In some embodiments, the interventional element <NUM> may be a coiled wire, a weave, and/or a braid formed of a plurality of braided filaments. Examples of suitable interventional elements <NUM> include any of those disclosed in <CIT>, <CIT>, <CIT>, and <CIT>.

In some embodiments, the interventional element <NUM> is a mesh structure (e.g., a braid, a stent, etc.) formed of a superelastic material (e.g., Nitinol) or other resilient or self-expanding material configured to self-expand when released from the third catheter <NUM>. The mesh structure may include a plurality of struts <NUM> and open spaces <NUM> between the struts <NUM>. In some embodiments, the struts <NUM> and spaces <NUM> may be situated along the longitudinal direction of the interventional element <NUM>, the radial direction, or both.

As depicted in <FIG>, the interventional element <NUM> may comprise a working length WL portion and a non-working length NWL portion. The portion of the interventional element <NUM> in the working length WL may be configured to interlock, capture, and/or engage a thrombus. The portion of the interventional element <NUM> in the non-working length NWL may contact thrombotic material in use, but is configured to perform a function that renders it ineffective or less effective than the working length WL portion for interlocking, capturing, and/or engaging with a thrombus. In some embodiments, such as that shown in <FIG>, a distal terminus of the working length WL portion is proximal of the distal terminus of the interventional element <NUM> (i.e., the working length WL portion is spaced apart from the distal terminus of the interventional element <NUM>), and the non-working length NWL portion is disposed between the working length WL and the band <NUM> and/or the distal end of the core member <NUM>.

With continued reference to <FIG>, in some embodiments, the non-working length NWL portion of the interventional element <NUM> can be coated with a non-conductive or insulative material (e.g., Parylene, PTFE, or other suitable non-conductive coating) such that the coated region is not in electrical contact with the surrounding media (e.g., blood). As a result, the current carried by the core member <NUM> to or from the interventional element <NUM> is only exposed to the surrounding media along the working length WL portion of the interventional element <NUM>. This can advantageously concentrate the electrically enhanced attachment effect along the working length WL of the interventional element <NUM>, where it is most useful, and thereby combine both the mechanical interlocking provided by the working length WL and the electrical enhancement provided by the delivered electrical signal. In some embodiments, a distal region of the interventional element <NUM> (e.g. distal of the working length WL) may likewise be coated with a non-conductive material (e.g., Parylene, PTFE, or other suitable non-conductive coating), leaving only a central portion or the working length WL of the interventional element <NUM> having an exposed conductive surface.

In some embodiments, the interventional element <NUM> may include a conductive material positioned on some or all of its outer surface. The conductive material, for example, can be gold and/or another suitable conductor that has a conductivity greater than (or a resistivity less than) that of the material comprising the interventional element <NUM>. The conductive material may be applied to the interventional element <NUM> via electrochemical deposition, sputtering, vapor deposition, dip-coating, and/or other suitable means.

<FIG> is a cross-sectional view of a strut <NUM> of the interventional element <NUM> having a material <NUM> disposed thereon. In various embodiments, the material <NUM> can be electrically insulative or conductive, as the case may be, to achieve the desired electrical properties. In some embodiments, different materials <NUM> can be applied in different portions of the interventional element <NUM>. Moreover, in some embodiments, a given material <NUM> can be deposited with varying thickness across the interventional element <NUM>.

Although the strut <NUM> shown in <FIG> has a generally square or rectangular cross-sectional shape, in some embodiments the interventional element <NUM> includes one or more struts or filaments having other cross-sectional shapes (e.g., circle, oval, etc.). The strut <NUM> has a surface comprised of an outer portion 101a facing away from a lumen or a central longitudinal axis of the interventional element <NUM>, an inner portion 101c facing toward the lumen or central longitudinal axis, and side portions 101b and 101d extending between the outer and inner portions 101a, 101c. In some embodiments, such as that shown in <FIG>, the material <NUM> may be disposed only at the outer portion 101a of the strut <NUM> and the inner and side portions 101b-d may be exposed, or otherwise not in contact with or covered by the material <NUM>. In some embodiments, the material <NUM> may be disposed only on the inner portion 101c of the surface of the strut <NUM>, only on one of the side portions 101b, 101d, or on any combination of the surface portions 101a-d.

<FIG> illustrates another example cross-sectional view in which a strut <NUM> is surrounded on all surface portions 101a-d with a material <NUM>. In such cases, the material <NUM> can be an electrically insulative or conductive coating that is selected, as the case may be, to achieve the desired electrical properties. In some embodiments, the material <NUM> is the result of surface treatment of the interventional element including the strut <NUM>. For example, the interventional element can be anodized to create an oxide layer and/or to increase a thickness of a pre-existing oxide layer over the interventional element (e.g., substantially surrounding strut <NUM>). The thickness of the material <NUM> (e.g., an oxide layer) can impact the local conductivity of the strut <NUM>, for example with a thicker oxide layer providing a lower conductivity than a thinner oxide layer. As such, by controlling the oxide layer and varying its thickness over different portions of the interventional element, a desired overall distribution of electrical conductivity over the surface of the interventional element can be achieved. In at least some embodiments, the material <NUM> can have a relatively greater thickness in a proximal portion of the interventional element (e.g., along some or all of the non-working length NWL and/or a proximal portion of the working length WL) and a relatively smaller thickness a distal portion of the interventional element (e.g., along some or all of the working length WL).

In some aspects of the present technology, the material <NUM> is disposed only on the working length WL portion of the interventional element <NUM> such that the proximal and distal end portions 100a, 100b of the interventional element <NUM> are exposed. In embodiments in which the material <NUM> is electrically conductive, the material can have a lower or even much lower resistance than the underlying material comprising the interventional element <NUM>, and therefore current delivered to the interventional element <NUM> may be concentrated along the working length WL portion. In several of such embodiments, the conductive material <NUM> may be disposed only on the outer portion 101a of the strut surface along the working length WL portion. In other embodiments, the conductive material <NUM> may be disposed on all or a portion of the strut surface along all or a portion of the length of the interventional element <NUM>.

In some embodiments, a first portion of the interventional element <NUM> is covered by a conductive material and a second portion of the interventional element <NUM> is covered by an insulative or dielectric material (e.g., Parylene and/or any other electrically insulative material or polymer). For example, in some embodiments the outer portion 101a of the strut surface is covered by a conductive material while an inner portion 101c of the strut surface is covered by an insulative material. In some embodiments, the working length WL portion of the interventional element <NUM> may be covered by a conductive material while the non-working length NWL portion is covered by an insulative material. In some embodiments, the conductive material may be disposed on all or a portion of the strut surface along all or a portion of the length of the interventional element <NUM>, and the insulative material may be disposed on those portions of the strut surface and/or working length not covered by the conductive material.

<FIG> illustrates a plan view of an interventional element <NUM> having a proximal end portion 100a and a distal end portion 100b. As described previously with respect to <FIG>, the interventional element <NUM> can include a working length WL and a non-working length NWL. As shown in <FIG>, the interventional element <NUM> includes a plurality of regions R1-R7 which are arranged adjacent one another in a proximal-distal direction. As described elsewhere herein, it may be desirable to vary the surface electrical properties of the interventional element among different regions of the interventional element <NUM>. For example, a surface treatment (e.g., anodization), coating, strut geometry, or other feature can be selected and/or varied to achieve varying electrical properties among the different regions. In the illustrated example, a surface electrical conductivity can vary among the different regions R1-R7, for example with a surface conductivity increasing in the distal direction, e.g., such that the surface conductivity in region R7 is greater than that of region R6, which is greater than that of region R5, which is greater than that of region R4, and so on down to region R1 which has the lowest surface conductivity among the regions R1-R7. Accordingly, for an interventional element <NUM> having N regions arranged in the proximal-to-distal direction similar to <FIG>, the surface conductivity SC of any given region Rx can be related to the surface conductivity SC of a proximally-adj acent region Rx-<NUM> by the relation [SCRx > SCRx-<NUM>] where x is a positive integer ranging from <NUM> to N, and SCR1 is no less than zero. In some embodiments, such a gradation can be achieved by varying a thickness of an insulative material disposed over the surface of the interventional element among the different regions R1-R7. For example, the insulative material can have a first thickness in the proximalmost region R1. The insulative material can have a second thickness less than the first in R2, and a third thickness less than the second in R3, etc. In this manner, each subsequent distal region can have a thickness of the insulative material (e.g., an oxide layer, which can optionally be provided by anodization) that is thinner or smaller than the more proximal regions. As a result, the surface electrical conductivity of each region can increase in the distal direction. This arrangement can counteract the tendency for electrical current to concentrate along a proximal portion of the interventional element (e.g., along the non-working length NWL).

Although discrete regions R1-R7 are illustrated here, in other embodiments the thickness of the insulative material can be varied in a continuous fashion without well-defined steps or transitions between adjacent regions. Additionally, the regions R1-R7 shown here are illustrative only, and in various embodiments the interventional element can be subdivided into different numbers or arrangements of regions (e.g., fewer or greater regions, regions arranged along a circumferential direction perpendicular to the proximal-distal variations shown in <FIG>, regions of varying size and shape, etc.) In some embodiments, the thickness of the insulative material may not monotonically increase or decrease along a proximal-distal direction, but rather may be arranged in other fashions. For example, a thickness of the insulative material may be greatest in region R4, with regions R3 and R5 each having lower thicknesses, and regions R2 and R6 lower thicknesses still, and regions R1 and R7 with little or no insulative material thereon. Various other configurations are possible and can be selected to achieve the desired electrical properties of the interventional element.

<FIG> is a schematic illustration of anodizing an interventional element <NUM> in accordance with the present technology. Anodization is a process for surface treating a metallic material to create and/or increase a thickness of an overlying oxide layer. As shown, an anodization system <NUM> includes an interventional element <NUM> and a cathode <NUM> each at least partially submerged in an electrolyte solution <NUM>. The interventional element <NUM> is electrically coupled to the positive terminal of a power supply <NUM> and the cathode <NUM> is electrically coupled to the negative terminal of the power supply <NUM>, such that a voltage is applied between the interventional element <NUM> and the cathode <NUM>. Upon application of voltage via the power supply <NUM>, oxygen ions are released from the electrolyte to combine with atoms of interventional element material at the surface thereof, thereby forming a metal-oxide layer over the surface of the interventional element (at least any portion of the interventional element that is immersed or submerged within the electrolyte <NUM>). In the case of an interventional element <NUM> made of Nitinol, a resulting oxide layer can include a Ti-Ni-O oxide (e.g., Ti<NUM>Ni<NUM>O). In many instances, oxidation may naturally occur in the presence of air such that a pre-anodized interventional element <NUM> already includes a thin film of a metal-oxide layer. In such instances, an anodization process can result in a controlled increase in the thickness of the naturally occurring oxide layer over the interventional element <NUM>.

The rate of growth of the oxide layer can be driven by a number of factors, including the size, material composition, and relative placement of the cathode <NUM> within the electrolyte solution <NUM>, as well as the material composition and volume of the electrolyte solution <NUM>. Additionally, the rate of growth of the oxide layer can be driven by the voltage applied via the power source <NUM> and the amount of time that anodization is performed (e.g., the amount of time that voltage is applied and/or the amount of time that the interventional element <NUM> is immersed within the electrolyte <NUM>). By moving the interventional element <NUM> into and out of the electrolyte <NUM>, it is possible to anodize one portion (e.g., proximal end portion 100a) to a greater extent than another portion (e.g., distal end portion 100b). By gradually removing the interventional element <NUM> from the electrolyte <NUM>, the portions removed earlier will generally have thinner oxide layers than the portions removed later. This can be used to achieve discrete "steps" with different oxide thicknesses by moving the interventional element <NUM> by discrete amounts and then leaving it in position for a period of time before moving it further. Alternatively, a more continuous gradient or transition can be achieved by slowly but continuously moving the interventional element <NUM> out of the electrolyte <NUM>, thereby producing a gradually increasing thickness of the oxide layer along the axis by which the interventional element <NUM> was removed from the electrolyte <NUM>. In the illustrated example, the interventional element <NUM> can be removed along the distal-proximal direction, such that the proximal end portion 100a can have a thicker oxide layer than the distal end portion 100b. In some embodiments, at least a portion of the interventional element <NUM> is not immersed within the electrolyte <NUM> (e.g., the distal end portion 100b), and therefore is not subject to anodization, while other portions of the interventional element <NUM> are anodized.

In various embodiments, the thickness of the oxide layer can range from <NUM> (i.e., in some regions there may be no oxide layer formed at all) to about <NUM> (from <NUM> to about <NUM> Angstroms) or more. The thickness of the oxide layer can be driven at least in part by the voltage applied via the power supply <NUM>, with increasing voltage resulting in increasing thickness of the oxide layer. Additionally, in some embodiments the oxide layer can have an apparent color that varies with thickness, for example appearing more silver or brown at lower thicknesses and yellow, pink, blue, and green at greater thicknesses. In some embodiments this can permit visual inspection for non-destructive evaluation of an oxide layer thickness.

Any suitable materials for the cathode <NUM> and electrolyte solution <NUM> can be selected to achieve the desired performance. Example materials for the cathode <NUM> include conductive metals such as platinum, aluminum, stainless steel, titanium, and alloys thereof, or any other suitable material. In some embodiments, the electrolyte <NUM> can be selected to be substantially non-corrosive to the interventional element <NUM>, which as noted above may be made of Nitinol or other suitable metallic material. Any suitable electrolyte <NUM> can be used. Examples include H<NUM>SO<NUM>, Na<NUM>SO<NUM>, CH<NUM>COOH, H<NUM>PO<NUM>, and HF.

The resulting oxide layer can take the form of an amorphous surface layer that still allows for electron exchange, albeit at a lower level than the bare underlying metal of the interventional element <NUM> due to inherent insulative characteristics of the amorphous surface layer. This resistance and alteration to the electron exchange will vary depending on the oxide layer thickness. In some embodiments, to achieve a current density distribution that is more uniform across the surface of the interventional element, or even to allow for increased current density at a more distal portion of the interventional element, the anodization process can be performed in a manner such that the interventional element <NUM> is gradually removed from the anodizing electrolyte <NUM> to form the desired charge gradient and/or conductivity gradient (e.g., with a greater thickness in a proximal portion of the interventional element <NUM> than in a distal portion of the interventional element <NUM>).

The addition of the oxide layer can also reduce the production of hydrogen and chlorine by-product bubbles when current is applied to the interventional element while in the presence of aqueous chloride media such as blood. As noted previously, hydrogen and chlorine gas bubbles can form when surface charge is concentrated over a small area of the interventional element while in the presence of blood. By using an oxide layer of varying thickness to achieve a more uniform or otherwise favorable surface charge distribution, the production of hydrogen and chlorine gas bubbles can be reduced or eliminated. In addition to achieving the desired electrical properties, anodization can increase the corrosion resistance of the interventional element <NUM>.

<FIG> illustrate additional embodiments of interventional elements <NUM>, <NUM>, <NUM> that can be configured to carry electrical current for use in thrombectomy procedures or other suitable applications. In various embodiments, the interventional elements <NUM>, <NUM>, and <NUM> can be coupled to core members and provided with electrode arrangements, current generator configurations, etc. that can be similar to the various embodiments of the interventional element <NUM> and associated electrode arrangements described herein, except as otherwise specified. For example, any of the interventional elements <NUM>, <NUM>, <NUM> shown herein can include a surface treatment (e.g., anodization) or coating to modify the electrical properties of its surface to achieve the desired overall electrical properties. In various embodiments, a proximal region or other non-working length of the interventional elements <NUM>, <NUM>, <NUM> can be coated or surface-treated to decrease a surface conductivity in those region(s). This arrangement can favorably distribute more surface charge to distal regions and/or working lengths of the interventional elements <NUM>, <NUM>, <NUM>.

As shown in <FIG>, the interventional elements can take a number of different forms while benefiting from the electrically enhanced adhesion to clot material provided by the appropriate surface properties (e.g., by anodizing and/or coating some or all of the interventional element). For example, with respect to <FIG>, the interventional element <NUM> is a clot retrieval device with an inner tubular member <NUM> and a multi-segment outer expandable member <NUM> having a greater diameter than the inner tubular member. The outer member <NUM> can have radially outwardly extending struts <NUM> defining inlet mouths <NUM> configured to receive clot material therein. With respect to <FIG>, the interventional element <NUM> is another example of a clot retrieval device, in this instance comprising a plurality of interlinked cages 701a-e having an atraumatic leading surface <NUM>. Each of the cages 701a-e can be configured to expand radially outwardly to engage a thrombus. <FIG> illustrates another example interventional element <NUM> in the form of a clot retrieval device, here comprising a coiled or helical member <NUM> configured to be expanded into or distal to a thrombus, thereby engaging the thrombus between turns of the coil <NUM> and facilitating removal from the body. In addition to these illustrative examples, the interventional element can take other forms, for example a removal device, a thrombectomy device, a retrieval device, a braid, a mesh, a laser-cut stent, or any suitable structure.

<FIG> illustrate a method of removing clot material CM from the lumen of a blood vessel V using the treatment system <NUM> of the present technology. As shown in <FIG>, the first catheter <NUM> can be advanced through the vasculature and positioned within the blood vessel such that a distal portion of the first catheter <NUM> is proximal of the clot material CM. As shown in Figure 4B, the second catheter <NUM> may be advanced through the first catheter <NUM> until a distal portion of the second catheter <NUM> is at or proximal to the clot material CM. Next, the third catheter <NUM> may be advanced through the second catheter <NUM> so that a distal portion of the third catheter <NUM> is positioned at or near the clot material CM. In some embodiments, the third catheter <NUM> may be positioned such that a distal terminus of the third catheter <NUM> is distal of the clot material CM. The interventional element <NUM> may then be advanced through the third catheter <NUM> in a low-profile configuration until a distal terminus of the interventional element <NUM> is at or adjacent the distal terminus of the third catheter <NUM>.

As shown in <FIG>, the third catheter <NUM> may be withdrawn proximally relative to the interventional element <NUM> to release the interventional element <NUM>, thereby allowing the interventional element <NUM> to self-expand within the clot material CM. As the interventional element <NUM> expands, the interventional element <NUM> engages and/or secures the surrounding clot material CM, and in some embodiments may restore or improve blood flow through the clot material CM by pushing open a blood flow path therethrough. In some embodiments, the interventional element <NUM> may be expanded distal of the clot material CM such that no portion of the interventional element <NUM> is engaging the clot material CM while the interventional element <NUM> is in the process of expanding toward the vessel wall. In some embodiments, the interventional element <NUM> is configured to expand into contact with the wall of the vessel V, or the interventional element <NUM> may expand to a diameter that is less than that of the blood vessel lumen such that the interventional element <NUM> does not engage the entire circumference of the blood vessel wall.

Once the interventional element <NUM> has been expanded into engagement with the clot material CM, the interventional element <NUM> may grip the clot material CM by virtue of its ability to mechanically interlock with the clot material CM. The current generator <NUM>, which is electrically coupled to the proximal end of the core member <NUM>, can deliver a current to the interventional element <NUM> before or after the interventional element <NUM> has been released from the third catheter <NUM> into the blood vessel and/or expanded into the clot material CM. The interventional element <NUM> 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 <NUM> can attract negatively charged constituents of the clot material CM, thereby enhancing the grip of the interventional element <NUM> on the clot material CM. This allows the interventional element <NUM> 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.

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 catheters <NUM>-<NUM> and/or one or more of the catheters <NUM>-<NUM> 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 current generator <NUM> and the interventional element <NUM>. 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 current 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 treatment system (e.g., one or more of the first-third catheters <NUM>, <NUM>, <NUM>, the interventional element <NUM>, etc.).

<FIG> illustrate optional processes that may be performed before, during, and/or after deployment of the interventional element <NUM>. With reference to <FIG>, in some methods fluid F may be delivered to the treatment site via the second catheter <NUM> and/or third catheter <NUM> while current is being delivered to the interventional element <NUM>. Fluid delivery may occur before or while the interventional element <NUM> is engaging the thrombus, and may coincide with the entire duration of current delivery or just a portion thereof.

Referring now to <FIG>, in some instances, aspiration may be applied to the treatment site via the second catheter <NUM>. For example, following deployment of the interventional element <NUM>, the third catheter <NUM> can be retracted and removed from the lumen of the second catheter <NUM>. The treatment site can then be aspirated via the second catheter <NUM>, for example via a suction source such as a pump or syringe coupled to a proximal portion of the second catheter <NUM>. In some embodiments, following expansion of the interventional element <NUM>, the treatment site is aspirated concurrently with supplying electrical energy to the interventional element <NUM> via the current generator <NUM>. 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 second catheter <NUM>, 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 <NUM> without risking deleterious effects of new clot formation. Additionally, aspiration can capture any gas bubbles formed along the interventional element <NUM> or marker band <NUM> (<FIG>) during application of electrical energy to the interventional element <NUM>, which can improve patient safety during the procedure.

In some embodiments, aspiration is applied while the interventional element <NUM> is retracted into the second catheter <NUM>. Aspiration at this stage can help secure the clot material CM within the second catheter <NUM> and prevent any dislodged portion of the clot material CM from escaping the second catheter <NUM> and being released back into the vessel V. In various embodiments, the treatment site can be aspirated continuously before, during, or after delivering electrical signals to the interventional element <NUM> as well as before, during, or after retraction of the interventional element <NUM> into the second catheter <NUM>.

With reference to <FIG>, at any time before, during, and/or after deployment of the interventional element <NUM>, a flow arrest element may be deployed within the blood vessel proximal of the clot material CM to partially or completely arrest blood flow to the treatment site. For example, as shown in Figures 6B-6F, the first catheter <NUM> may be a balloon guide catheter having a balloon <NUM> at its distal portion. The balloon <NUM> may be configured to inflate or expand into apposition with the surrounding blood vessel wall, thereby at least partially arresting blood flow distal to the balloon <NUM>. In some embodiments, the flow arrest element can have other forms or configurations suitable for partially or completely arresting blood flow within the vessel V.

In some methods, the flow arrest element may be deployed at a location along the blood vessel proximal of the clot material CM (for example, at a proximal portion of the internal carotid artery) and may remain inflated as the interventional element <NUM> is deployed and eventually withdrawn to remove the thrombus. For example, <FIG> show the balloon <NUM> blocking flow from a portion of the artery proximal of the balloon toward the interventional element <NUM> and treatment area, while the second catheter <NUM> and third catheter <NUM> are positioned at the treatment site (<FIG>), while the interventional element <NUM> is expanded within the clot material CM (<FIG>), while fluid is infused at the treatment site (<FIG>), and while aspiration is applied at the treatment site (<FIG>). Although the balloon <NUM> is shown in an expanded state in each of <FIG>, it will be appreciated that the balloon <NUM> may be in an unexpanded state and/or deflated at any time throughout the procedure to allow blood flow.

As shown in <FIG>, in some embodiments the flow arrest element may be a balloon <NUM> coupled to the second catheter <NUM> (such as a distal access catheter). In such embodiments, the first catheter <NUM> may not include a flow arrest element such that flow arrest is achieved via deployment of the flow arrest element coupled to the second catheter <NUM>. For example, in such embodiments, the first catheter <NUM> may be a sheath or support catheter. The balloon <NUM> may be inflated at a location distal of the distal end of the first catheter <NUM>, closer to the thrombus. In some methods, the flow arrest element may be deflated and inflated several times throughout the procedure.

At least while the interventional element <NUM> is deployed and engaging the thrombus CM, electric current may be delivered to the interventional element <NUM> to positively charge the interventional element <NUM>, thereby enhancing clot adhesion to the interventional element <NUM>. As previously discussed, the inventors have observed improved electrically enhanced clot adhesion in the absence of blood flow. As such, it may be especially beneficial to arrest blood flow (e.g., via a flow arrest element on the first or second catheter <NUM>, <NUM>) while the interventional element <NUM> is charged, and while expanding the interventional element <NUM> within the thrombus and/or when withdrawing the thrombus proximally.

With reference to <FIG>, while the interventional element <NUM> is engaged with the clot material CM, the clot material CM can be removed. For example, the interventional element <NUM>, with the clot material CM gripped thereby, can be retracted proximally (for example, along with the second catheter <NUM> and, optionally, the third catheter <NUM>). The second catheter <NUM>, interventional element <NUM>, and associated clot material CM may then be withdrawn from the patient, optionally through one or more larger surrounding catheters. During this retraction, the interventional element <NUM> can grip the clot material CM electrically and/or electrostatically, e.g., via the application of current from a current generator as discussed herein. (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 <NUM> can maintain an enhanced or electrically and/or electrostatically enhanced grip on the clot material CM during retraction. In other embodiments, the current generator <NUM> may cease delivery of electrical current or signals to the interventional element <NUM> prior to retraction of the interventional element <NUM> with respect to the vessel V. In some embodiments, the interventional element <NUM> 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.

<FIG> show various electrical waveforms for use with the treatment systems of the present technology. Although the waveforms and other power delivery parameters disclosed herein can be used with the devices and methods described above with respect to <FIG>, the waveforms and other parameters are also applicable to other device configurations and techniques. For example, the return electrode can be provided along the catheter wall, as a separate conductive member extending within the catheter lumen, as a needle electrode provided elsewhere in the body, etc. In each of these device configurations, the power delivery parameters and waveforms can be beneficially employed to promote clot adhesion without damaging surrounding tissue. Additionally, although the waveforms and other power delivery parameters disclosed herein may be used 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 waveforms and power delivery parameters disclosed herein may be used to electrically enhance removal of emboli from body lumens other than blood vessels (e.g., the digestive tract, etc.) and/or may be used to electrically enhance removal of emboli from blood vessels outside of the brain (e.g., pulmonary blood vessels, blood vessels within the legs, etc.).

While applying a continuous uniform direct current (DC) electrical signal (as shown in <FIG>) to positively charge the interventional element and/or aspiration 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 wishing to be 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.

<FIG> illustrate various periodic waveforms that can be used with the devices and methods described above with respect to <FIG>, as well as with other devices and techniques. <FIG> illustrates a continuous uniform DC electrical signal which can also be used in some embodiments. Referring to <FIG>, electrical power can be delivered according to these waveforms as pulsed direct current. <FIG> illustrate periodic square and triangular waveforms, respectively. These two waveforms have the same amplitude, but the triangular waveform is able to deliver the same peak current as the square waveform, with only half of the total charge delivered, and less total energy delivered. <FIG> illustrates another pulsed-DC or periodic waveform which is a composite of a square waveform and a triangular waveform. This superposition of a triangular waveform and a square waveform shown in <FIG> delivers additional efficacy compared to the triangular waveform of <FIG> while nonetheless delivering less overall energy than the square waveform of <FIG>. This is because the delivered energy is proportional to the square of current and the brief high peak in the composite waveform of <FIG> ensures that current is supplied without dispensing excessive energy. <FIG> illustrates yet another non-square waveform, in this case a trapezoidal waveform in which "ramp-up" and "ramp-down" portions at the beginning and end of each pulse provide periods of reduced current compared to square waveforms. In other embodiments, different non-square waveforms can be used, including a superposition of a square waveform with any non-square waveform, depending on the desired power delivery characteristics.

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 <NUM>-<NUM> mC, or between about <NUM>-<NUM> mC. According to some embodiments, the total electrical charge delivered to the interventional element and/or catheter may be less than <NUM> mC, less than <NUM> mC, less than <NUM> mC, less than <NUM> mC, less than <NUM> mC, or less than <NUM> mC.

In some embodiments, the total energy delivered to the interventional element and/or aspiration catheter can be between about <NUM>-<NUM>,<NUM> mJ, or between about <NUM>-<NUM>,<NUM> mJ, or between about <NUM>-<NUM> mJ. According to some embodiments, the total energy delivered to the interventional element and/or aspiration catheter may be less than <NUM>,<NUM> mJ, less than <NUM>,<NUM> mJ, less than <NUM>,<NUM> mJ, less than <NUM>,<NUM> mJ, less than <NUM>,<NUM> mJ, less than <NUM>,<NUM> mJ, less than <NUM>,<NUM> mJ, less than <NUM> mJ, less than <NUM>,<NUM> mJ, less than <NUM> mJ, less than <NUM> mJ, less than <NUM> mJ, less than <NUM> mJ, less than <NUM> mJ, less than <NUM> mJ, less than <NUM> mJ, or less than <NUM> mJ, or less than <NUM> mJ, or less than <NUM> mJ, or less than <NUM> mJ, or less than <NUM> mJ, or less than <NUM> mJ, or less than <NUM> mJ, or less than <NUM> mJ.

In some embodiments, the peak current delivered can be between about <NUM>-<NUM> mA, or between about <NUM>-<NUM> mA. According to some embodiments, the peak current delivered may be greater than <NUM> mA, greater than <NUM> mA, greater than <NUM> mA, greater than <NUM> mA, greater than <NUM> mA, or greater than <NUM> 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 <NUM> minute, no more than <NUM> minutes, no more than <NUM> minutes, no more than <NUM> minutes, or no more than <NUM> minutes. According to some embodiments, the total energy delivery time may be less about <NUM> seconds, less than about <NUM> minute, less than about <NUM> seconds, or less than about <NUM> 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 <NUM>% about <NUM>% or between about <NUM>% to about <NUM>%. According to some embodiments, the duty cycle may be about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, or about <NUM>%. In yet other embodiments, a constant current may be used, in which the duty cycle is <NUM>%. For <NUM>% duty cycle embodiments, a lower time or current may be used to avoid delivering excess total energy to the treatment site.

Table <NUM> presents a range of values for power delivery parameters of different waveforms. For each of the conditions set forth in Table <NUM>, a resistance of <NUM> kohm and a frequency of <NUM> (for the Square, Triangle, and Composite conditions) was used. The Constant conditions represent a continuous and steady current applied for the duration, i.e. <NUM>% duty cycle. The Peak Current <NUM> column represents the peak current for the corresponding waveform. For the Composite conditions, the Peak Current <NUM> column indicates the peak current of the second portion of the waveform. For example, referring back to Figure 7C, Peak Current <NUM> would correspond to the current at the top of the triangular portion of the waveform, while Peak Current <NUM> would correspond to the current at the top of the square portion of the waveform.

As seen in Table <NUM>, the periodic waveforms (Square, Triangle, and Composite conditions) achieve higher peak currents with lower overall charge delivered than the corresponding Constant conditions. For example, in condition Constant <NUM>, a peak current of <NUM> mA corresponds to a total energy delivered of <NUM>,<NUM> mJ, while condition Square <NUM> delivers a peak current of <NUM> mA with a total energy of only <NUM>,<NUM> mJ. Conditions Triangle <NUM> and Composite <NUM> similarly deliver lower total energy while maintaining a peak current of <NUM> mA. Since clot-adhesion appears to be driven by peak current, these periodic waveforms can therefore offer improved clot adhesion while reducing the risk of damaging tissue at the treatment site or promoting new clot formation. Table <NUM> also indicates that the Triangle and Composite conditions achieve higher peak currents with lower overall charge delivered than the corresponding Square conditions. For example, condition Square <NUM> has a peak current of <NUM> mA and a total charge delivered of <NUM> mC, while condition Triangle <NUM> has a peak current of <NUM> mA but a total charge delivered of only <NUM> mC, and condition Composite <NUM> has a peak current of <NUM> mA and a total charge delivered of only <NUM> mC. As such, these non-square waveforms provide additional benefits by delivering desirable peak current while reducing the overall charge delivered to the treatment site.

Although Table <NUM> represents a series of waveforms with a single frequency (<NUM>), in some embodiments the frequency of the pulsed-DC waveforms can be controlled to achieve the desired effects. For example, in some embodiments the frequency of the waveform can be between <NUM> and <NUM>, between <NUM> and <NUM>, or between <NUM> to <NUM>.

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.

Claim 1:
A thrombectomy device comprising:
an interventional element (<NUM>,<NUM>,<NUM>,<NUM>) configured to be advanced intravascularly to a treatment site in a corporeal lumen and to engage a thrombus therein, wherein the interventional element (<NUM>,<NUM>,<NUM>,<NUM>) possesses an inner conductive material and an overlying material that has a lower electrical conductivity than the inner conductive material, characterized by
the overlying material having a thickness gradient that decreases from a first thickness in a proximal portion of the interventional element (<NUM>,<NUM>,<NUM>,<NUM>) to a second non-zero thickness in a distal portion of the interventional element (<NUM>,<NUM>,<NUM>,<NUM>) such that a surface electrical conductivity of the interventional element (<NUM>,<NUM>,<NUM>,<NUM>) has a gradient that increases from the proximal portion of the interventional element to the distal portion of the interventional element (<NUM>,<NUM>,<NUM>,<NUM>), wherein the surface electrical conductivity is greater than zero in the proximal portion.