Patent Publication Number: US-2022218372-A1

Title: Electrically enhanced retrieval of material from vessel lumens

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 16/949,849, filed Nov. 17, 2020, which is a continuation of U.S. patent application Ser. No. 16/024,367, filed Jun. 29, 2018, which claims the benefit of priority to U.S. Provisional Application No. 62/688,636, filed Jun. 22, 2018, the contents of each of which are incorporated by reference herein in their entirety. 
    
    
     TECHNICAL FIELD 
     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 electrically enhanced removal of clot material from blood vessels. 
     BACKGROUND 
     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&#39;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. 
     SUMMARY 
     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 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. 
     While applying a current to positively charge the interventional element can improve attachment of the thrombus to the interventional element, the inventors have discovered particularly effective waveforms and power delivery parameters for promoting thrombus attachment. It is important to provide sufficient current and power to enhance clot-adhesion without ablating tissue or generating new clots (i.e., the delivered power should not be significantly thrombogenic). The clot-adhesion effect appears to be driven by the peak current of the delivered electrical signal. Periodic (e.g., pulse-width modulated or pulsed direct current) waveforms can advantageously provide the desired peak current without delivering excessive total energy. In particular, non-square periodic waveforms can be especially effective in providing the desired peak current without delivering excessive total energy or electrical charge to the interventional element. In some embodiments, the overall charge delivered can be between about 30-1200 mC, the total energy delivered can be between about 120-24,000 mJ, and/or the peak current delivered can be between about 0.5-5 mA. In at least some embodiments, the duration of energy delivery can be between 30 seconds and 5 minutes, and in some embodiments no more than 2 minutes. 
     The treatment systems and methods of the present technology can further improve adhesion of the clot to the interventional element by varying features of the interventional element. For example, in some embodiments, some or all of the interventional element 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 interventional element may be coated with the conductive material while a non-working length of the interventional element may be coated with an insulative material. 
     Treatment systems and methods disclosed herein may also improve clot adhesion by modifying the environment at the treatment site. For example, the inventors have observed that blood flow at the treatment site reduces adhesion forces between clot material and the interventional element, even when the interventional element is positively charged. To address this loss of adhesion, the present technology provides systems and methods for arresting blood flow at the treatment site at least while supplying electrical energy to the treatment site. In addition, the present technology provides systems and methods for infusing certain fluids (such as saline and/or contrast) at the treatment site at least during energy delivery to improve conductivity at the treatment site for electrically enhanced clot adhesion. 
     Many of the treatment systems of the present technology include an aspiration catheter for applying negative pressure at the treatment site to secure the clot against a distal portion of the aspiration catheter (and/or other component of the treatment system). Aspiration also helps capture any newly formed clots to reduce the risk of downstream embolism. Suction may be applied before, during, and/or after supplying electrical energy to the interventional element. In some embodiments, a distal portion of the aspiration catheter may be configured for electrically enhanced clot adhesion such that clot engagement and retrieval may be performed without a separate interventional element. For example, in some aspects of the technology, the aspiration catheter may include a delivery electrode at its distal tip that is configured to be positively charged by the current generator. A return electrode may be disposed at a number of different locations, such as the aspiration catheter or another component of the treatment system (such as a guide catheter). Securement of the clot to the aspiration catheter via suction may be enhanced by the additional adhesion forces generated when the delivery electrode is positively charged. 
     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 (1, 2, 3, etc.) 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, e.g., clause (1, 23, 35, etc.). The other clauses can be presented in a similar manner. 
     Clause 1. A thrombectomy system, comprising:
         a power source having a positive terminal;   an elongated member having a proximal end coupled to the power source and a distal end configured to be positioned within a blood vessel at or near a thrombus; and   an interventional element carried at the distal end of the elongated member and coupled to the positive terminal of the power source, wherein the interventional element includes a first metallic material and a second metallic material disposed on the first metallic material along at least a portion of the interventional element, and wherein the power source is configured to deliver a current to the interventional element to positively charge the interventional element and promote adhesion of the thrombus thereto.       

     Clause 2. The thrombectomy system of Clause 1, wherein the power source is configured to be extracorporeally positioned while the interventional element is positioned at or near the thrombus. 
     Clause 3. The thrombectomy system of Clause 1 or Clause 2, wherein an electrical conductivity of the second metallic material is greater than an electrical conductivity of the first metallic material. 
     Clause 4. The thrombectomy system of any one of Clauses 1 to 3, wherein the first metallic material is a superelastic alloy and the second metallic material is gold. 
     Clause 5. The thrombectomy system of any one of Clauses 1 to 4, wherein the first metallic material has a surface including an outward-facing portion that faces away from a central lumen of the interventional element, and wherein the second metallic material is disposed on the first metallic material only at the outward-facing portion and not at a remaining portion of the surface. 
     Clause 6. The thrombectomy system of any one of Clauses 1 to 5, wherein the interventional element comprises a working length portion and a non-working length portion, the working length portion being configured to interlock, capture, and/or engage a thrombus. 
     Clause 7. The thrombectomy system of Clause 6, wherein a distal terminus of the working length portion is proximal of a distal terminus of the interventional element. 
     Clause 8. The thrombectomy system of Clause 6 or Clause 7, wherein the working length portion is spaced apart from a distal terminus of the interventional element. 
     Clause 9. The thrombectomy system of any one of Clauses 6 to 8, wherein the non-working length portion is disposed between a distal end of the elongated member and a proximal end of the working length portion. 
     Clause 10. The thrombectomy system of any one of Clauses 6 to 9, wherein the second metallic material has a greater conductivity than the first metallic material and is disposed on the first metallic material only along the working length portion of the interventional element and not along the non-working length portion. 
     Clause 11. The thrombectomy system of any one of Clauses 6 to 10, wherein the second metallic material has a greater conductivity than the first metallic material and is disposed on the first metallic material only along the working length portion of the interventional element and not along (i) the non-working length portion and (ii) a distal-most region of the interventional element. 
     Clause 12. The thrombectomy system of any one of Clauses 6 to 11, wherein the non-working length portion is covered by a non-conductive and/or insulative material such that the non-working length portion is not in electrical contact with the surrounding media when the interventional element is deployed within a blood vessel. 
     Clause 13. The thrombectomy system of any one of Clauses 6 to 11, wherein the non-working length portion and a region of the interventional element distal of the working length portion are covered by a non-conductive and/or insulative material such that the non-working length portion and the region are not in electrical contact with the surrounding media when the interventional element is deployed within a blood vessel. 
     Clause 14. The thrombectomy system of any one of Clauses 6 to 11, wherein the second metallic material is selectively disposed on the first metallic material such that the delivered current is concentrated along the working length portion. 
     Clause 15. The thrombectomy system of any one of Clauses 1 to 14, wherein the power source is configured to deliver direct current to the interventional element. 
     Clause 16. The thrombectomy system of any one of Clauses 1 to 15, wherein the power source is configured to deliver pulsatile current to the interventional element. 
     Clause 17. The thrombectomy system of any one of Clauses 1 to 16, wherein the current is a constant current having an amplitude of between about 0.5 mA and about 5 mA. 
     Clause 18. The thrombectomy system of any one of Clauses 1 to 17, wherein the interventional element comprises a thrombectomy device. 
     Clause 19. The thrombectomy system of any one of Clauses 1 to 18, wherein the interventional element comprises a stent retriever. 
     Clause 20. The thrombectomy system of any one of Clauses 1 to 19, wherein the interventional element comprises a removal device. 
     Clause 21. The thrombectomy system of any one of Clauses 1 to 20, wherein the interventional element is a mesh. 
     Clause 22. The thrombectomy system of any one of Clauses 1 to 21, wherein the interventional element is a laser-cut stent. 
     Clause 23. A thrombectomy system, comprising:
         a power source having a positive terminal;   a first catheter;   a second catheter configured to be slidably received through a lumen of the first catheter;   an elongated member configured to be slidably received through a lumen of the second catheter, the elongated member having a proximal end coupled to the power source and a distal end configured to be positioned within a blood vessel at or near a thrombus; and   an interventional element carried at the distal end of the elongated member and coupled to the positive terminal of the power source, wherein the interventional element includes a first metallic material and a second metallic material disposed on the first metallic material along at least a portion of the interventional element, and wherein the power source is configured to deliver a current to the interventional element to positively charge the interventional element and promote adhesion of the thrombus thereto.       

     Clause 24. The thrombectomy system of Clause 23, wherein the first catheter includes a flow arrest element configured to expand within the vessel lumen and at least partially arrest blood flow proximal of the thrombus. 
     Clause 25. The thrombectomy system Clause 23 or Clause 24, wherein the first catheter is a guide catheter and the second catheter is a microcatheter. 
     Clause 26. The thrombectomy system of any one of Clauses 23 to 25, wherein the thrombectomy system further includes a third catheter configured to be slidably received through the lumen of the first catheter. 
     Clause 27. The thrombectomy system of Clause 26, wherein the second catheter is configured to be slidably received within a lumen of the second catheter. 
     Clause 28. The thrombectomy system of Clause 26, wherein the first catheter is a guide catheter and the third catheter is a distal access catheter. 
     Clause 29. The thrombectomy system of Clause 26, wherein the first catheter is a guide catheter, the second catheter is a microcatheter, and the third catheter is a distal access catheter. 
     Clause 30. The thrombectomy system of Clause 26, wherein the third catheter is an aspiration catheter. 
     Clause 31. The thrombectomy system of Clause 26, wherein the first catheter is a balloon guide catheter and the third catheter is a distal access catheter. 
     Clause 32. The thrombectomy system Clause 26, wherein the first catheter is a guide catheter and the third catheter is a distal access catheter, wherein the distal access catheter includes a flow arrest element configured to expand within the vessel lumen and at least partially arrest blood flow proximal of the thrombus. 
     Clause 33. The thrombectomy system of Clause 32, wherein the distal access catheter is an aspiration catheter. 
     Clause 34. The thrombectomy system of any one of Clauses 26 to 33, wherein:
         the first catheter includes a flow arrest element configured to expand within the vessel lumen and at least partially arrest blood flow proximal of the thrombus, and   the third catheter is an aspiration catheter configured to apply negative pressure at the treatment site.       

     Clause 35. A method, comprising:
         intravascularly delivering an interventional element to a treatment site within a blood vessel, wherein the interventional element comprises a first metallic material and a second metallic material disposed on the first metallic material; and   while the interventional element is positioned at the treatment site, producing a positive charge along at least a portion of the interventional element via a power source coupled to the interventional element at an extracorporeal location.       

     Clause 36. The method of Clause 35, further comprising concentrating the positive charge along a working length of the interventional element, wherein a proximal end of the working length is distal of a proximal end of the interventional element and a distal end of the working length is proximal of a distal end of the interventional element. 
     Clause 37. The method of any one of Clauses 35 to 36, wherein producing a positive charge includes delivering a direct current to the interventional element from the power source. 
     Clause 38. The method of any one of Clauses 35 to 37, wherein producing a positive charge includes delivering a pulsatile current to the interventional element from the power source. 
     Clause 39. The method of any one of Clauses 35 to 38, wherein an electrical conductivity of the second metallic material is greater than an electrical conductivity of the first metallic material. 
     Clause 40. The method of any one of Clauses 35 to 39, wherein the second metallic material is gold. 
     Clause 41. The method of any one of Clauses 35 to 40, wherein producing a positive charge includes delivering a current to the interventional element, the current having an amplitude of between about 0.5 mA and about 5 mA. 
     Clause 42. The method of any one of Clauses 35 to 41, wherein producing a positive charge includes delivering a current to the interventional element, the current having an amplitude of about 2 mA. 
     Clause 43. The method of any one of Clauses 35 to 42, wherein the interventional element comprises a thrombectomy device. 
     Clause 44. The method of any one of Clauses 35 to 43, wherein the interventional element comprises a stent retriever. 
     Clause 45. The method of any one of Clauses 35 to 44, wherein the interventional element comprises a removal device. 
     Clause 46. The method of any one of Clauses 35 to 45, wherein the interventional element is a laser-cut stent or a mesh. 
     Clause 47. A method, comprising:
         intravascularly delivering an interventional element to a treatment site within a blood vessel at or near a thrombus; and   while the interventional element is positioned at the treatment site and engaging the thrombus: (a) delivering a fluid to the treatment site, and (b) while at least some of the fluid is being delivered, applying a positive charge to the interventional element, thereby promoting adhesion of the thrombus to the interventional element.       

     Clause 48. The method of Clause 47, wherein an ion concentration of the fluid is greater than an ion concentration of blood. 
     Clause 49. The method of any one of Clauses 47 to 48, wherein the fluid is saline. 
     Clause 50. The method of any one of Clauses 47 to 48, wherein the fluid is contrast. 
     Clause 51. The method of any one of Clauses 47 to 50, wherein delivering the fluid to the treatment site increases an electrical conductivity at the treatment site. 
     Clause 52. The method of any one of Clauses 47 to 51, wherein delivering the fluid occurs while blood is flowing at the treatment site. 
     Clause 53. The method of any one of Clauses 47 to 51, wherein delivering the fluid occurs while blood flow is partially arrested at the treatment site. 
     Clause 54. The method of any one of Clauses 47 to 51, wherein delivering the fluid occurs while blood flow is completely arrested at the treatment site. 
     Clause 55. The method of any one of Clauses 47 to 54, further comprising expanding a flow arrest element within the blood vessel proximal of the treatment site before or while delivering the fluid. 
     Clause 56. The method of any one of Clauses 47 to 55, wherein the interventional element includes a first material and a second material disposed on the first material along at least a portion of the interventional element, wherein the second material is different than the first material. 
     Clause 57. The method of any one of Clauses 47 to 55, wherein the interventional element includes a first metallic material and a second metallic material disposed on the first metallic material along at least a portion of the interventional element, and wherein a conductivity of the second metallic material is greater than a conductivity of the first metallic material. 
     Clause 58. The method of Clause 57, wherein the second metallic material is gold. 
     Clause 59. The method of any one of Clauses 47 to 58, wherein applying a positive charge includes delivering an electric current to the interventional element from a power source positioned at an extracorporeal location. 
     Clause 60. The method of Clause 59, wherein the current is delivered while the interventional element is positioned at the treatment site. 
     Clause 61. The method of any one of Clauses 59 to 60, wherein the current has an amplitude of between about 0.5 mA and about 5 mA. 
     Clause 62. The method of any one of Clauses 59 to 61, wherein the current is a direct current. 
     Clause 63. The method of any one of Clauses 59 to 62, wherein the amplitude of the current remains generally constant. 
     Clause 64. The method of any one of Clauses 59 to 63, wherein the current is delivered for at least 30 seconds, at least 1 minute, or at least 2 minutes. 
     Clause 65. The method of any one of Clauses 47 to 64, wherein the interventional element comprises a thrombectomy device. 
     Clause 66. The method of any one of Clauses 47 to 65, wherein the interventional element comprises a stent retriever. 
     Clause 67. The method of any one of Clauses 47 to 66, wherein the interventional element comprises a removal device. 
     Clause 68. The method of any one of Clauses 47 to 67, wherein the interventional element is a mesh. 
     Clause 69. The method of any one of Clauses 47 to 68, wherein the interventional element is a laser-cut stent. 
     Clause 70. The method of any one of Clauses 47 to 69, wherein the fluid is delivered through a distal access catheter. 
     Clause 71. The method of any one of Clauses 47 to 70, wherein the fluid is a liquid. 
     Clause 72. A method, comprising:
         intravascularly delivering thrombectomy device to a treatment site within a blood vessel at or near a thrombus;   positioning a catheter at the treatment site such that a distal end of the catheter is proximal of the thrombus; and   while the thrombectomy device is positioned at the treatment site and engaging the thrombus: (a) delivering a fluid through the catheter to the treatment site, wherein delivering the fluid increases an electrical conductivity at the treatment site; and (b) while at least some of the fluid is being delivered, delivering current to the thrombectomy device, thereby promoting adhesion of the thrombus to the thrombectomy device.       

     Clause 73. The method of Clause 72, wherein an ion concentration of the fluid is greater than an ion concentration of blood. 
     Clause 74. The method of any one of Clauses 72 to 73, wherein the fluid is saline. 
     Clause 75. The method of any one of Clauses 72 to 73, wherein the fluid is contrast. 
     Clause 76. The method of any one of Clauses 72 to 74, wherein delivering the fluid occurs while blood is flowing at the treatment site. 
     Clause 77. The method of any one of Clauses 72 to 74, wherein delivering the fluid occurs while blood flow is partially arrested at the treatment site. 
     Clause 78. The method of any one of Clauses 72 to 74, wherein delivering the fluid occurs while blood flow is completely arrested at the treatment site. 
     Clause 79. The method of any one of Clauses 72 to 78, wherein delivering current to the thrombectomy device positively charges the thrombectomy device. 
     Clause 80. The method of any one of Clauses 72 to 79, wherein the thrombectomy device comprises a braid. 
     Clause 81. The method of any one of Clauses 72 to 80, wherein the thrombectomy device comprises a stent retriever. 
     Clause 82. The method of any one of Clauses 72 to 81, wherein the thrombectomy device comprises a removal device. 
     Clause 83. The method of any one of Clauses 72 to 82, wherein the thrombectomy device is a mesh. 
     Clause 84. The method of any one of Clauses 72 to 83, wherein the thrombectomy device is a laser-cut stent. 
     Clause 85. A thrombectomy system, comprising:
         a catheter having a distal portion configured to be positioned adjacent to a thrombus in a blood vessel;   an electrode disposed at the distal portion of the catheter, the electrode configured to be electrically coupled to an extracorporeal power supply; and   an interventional element configured to be delivered through a lumen of the catheter, the interventional element configured to be electrically coupled to the extracorporeal power supply.       

     Clause 86. The system of Clause 85, wherein the electrode is in electrical communication with a conductive lead extending proximally along the catheter. 
     Clause 87. The system of Clause 86, wherein the conductive lead is disposed within a wall of the catheter. 
     Clause 88. The system of Clause 86, wherein the conductive lead is disposed along an external surface of the catheter. 
     Clause 89. The system of any one of Clauses 85 to 88, wherein the electrode comprises a conductive band extending at least partially circumferentially around the distal portion of the catheter. 
     Clause 90. The system of Clause 89, wherein the conductive band is disposed on an inner surface of the catheter. 
     Clause 91. The system of Clause 89, wherein the conductive band is disposed on an outer surface of the catheter. 
     Clause 92. The system of any one of Clauses 85 to 91, wherein the electrode comprises a stent engaged with an inner surface of the catheter. 
     Clause 93. The system of any one of Clauses 85 to 92, wherein the catheter comprises an aspiration catheter. 
     Clause 94. The system of any one of Clauses 85 to 93, wherein the catheter comprises a distal access catheter. 
     Clause 95. The system of any one of Clauses 85 to 93, wherein the catheter comprises a guide catheter. 
     Clause 96. The system of any one of Clauses 85 to 93, wherein the catheter comprises a balloon guide catheter. 
     Clause 97. The system of any one of Clauses 85 to 96, wherein the catheter is a first catheter and the system further comprises a second catheter, wherein the first catheter is configured to be slidably disposed within a lumen of the second catheter. 
     Clause 98. The system of any one of Clauses 85 to 96, wherein the catheter is a first catheter and the system further comprises a second catheter, wherein the second catheter is configured to be slidably disposed within a lumen of the first catheter. 
     Clause 99. The system of any one of Clauses 85 to 98, wherein the catheter is a microcatheter. 
     Clause 100. The system of any one of Clauses 85 to 96, wherein the catheter is a first catheter and the system further comprises a second catheter and a third catheter, wherein the first catheter is configured to be slidably disposed within a lumen of the second catheter, and the second catheter is configured to be slidably disposed within a lumen of the third catheter. 
     Clause 101. The system of any one of Clauses 85 to 100, wherein the electrode comprises a conductive band extending at least partially circumferentially around the distal portion of the catheter. 
     Clause 102. The system of Clause 101, wherein the conductive band is disposed on an inner surface of the catheter. 
     Clause 103. The system of Clause 101, wherein the conductive band is disposed on an outer surface of the catheter. 
     Clause 104. The system of any one of Clauses 85 to 103, further comprising a suction source configured to supply negative pressure through the catheter to aspirate a region adjacent to the distal portion of the catheter. 
     Clause 105. The system of any one of Clauses 85 to 104, wherein the catheter is an aspiration catheter having a proximal portion configured to be fluidically coupled to a suction source. 
     Clause 106. The system of any one of Clauses 85 to 105, further comprising a power supply having positive and negative terminals, the electrode being coupled to the negative terminal and the interventional element being coupled to the positive terminal. 
     Clause 107. The system of any one of Clauses 85 to 106, wherein, when the interventional element and the distal portion of the catheter are in the presence of an electrolytic medium and voltage is supplied to the first and second electrical terminals, current flows from the interventional element to the electrode. 
     Clause 108. The system of any one of Clauses 85 to 107, wherein a proximal end of the interventional element is coupled to a distal end of a core member, the core member extending proximally through the catheter. 
     Clause 109. The system of Clause 108, wherein the core member comprises an electrically conductive wire extending along its length. 
     Clause 110. The system of Clause 109, wherein the core member comprises an insulative coating surrounding the wire along at least a portion of its length. 
     Clause 111. The system of any one of Clauses 85 to 110, wherein the interventional element is electrically conductive. 
     Clause 112. The system of any one of Clauses 85 to 111, wherein the interventional element comprises a thrombectomy device. 
     Clause 113. The system of any one of Clauses 85 to 112, wherein the interventional element comprises a stent retriever. 
     Clause 114. The system of any one of Clauses 85 to 113, wherein the interventional element comprises a removal device. 
     Clause 115. The system of any one of Clauses 85 to 114, wherein the interventional element comprises a catheter. 
     Clause 116. The system of any one of Clauses 85 to 115, wherein a portion of the interventional element is coated with a conductive material. 
     Clause 117. The system of Clause 116, wherein the conductive material comprises gold. 
     Clause 118. The system of any one of Clauses 85 to 117, wherein a portion of the interventional element is coated with a non-conductive material. 
     Clause 119. The system of Clause 118, wherein the non-conductive material comprises parylene. 
     Clause 120. A medical device delivery system, comprising:
         a medical device coupled to a distal end of an elongate shaft, the shaft configured to be electrically coupled to a first terminal of a power supply; and   an elongate tubular member configured to receive the shaft therethrough, the tubular member having an electrode disposed at a distal portion thereof and a conductive lead electrically coupled to the electrode, the conductive lead extending along a length of the tubular member and configured to be electrically coupled to a second terminal of the power supply.       

     Clause 121. The system of Clause 120, wherein the shaft and the conductive lead are configured to be coupled to first and second terminals, respectively, of an extracorporeal power supply. 
     Clause 122. The system of any one of Clauses 120 to 121, wherein the shaft comprises a conductive element in electrical communication with the medical device 
     Clause 123. The system of any one of Clauses 120 to 122, wherein the medical device is electrically conductive. 
     Clause 124. The system of any one of Clauses 120 to 123, wherein the conductive lead is disposed within a wall of the tubular member. 
     Clause 125. The system of any one of Clauses 120 to 123, wherein the conductive lead is disposed along an external surface of the tubular member. 
     Clause 126. The system of any one of Clauses 120 to 125, wherein the electrode comprises a conductive band extending at least partially circumferentially around the distal portion of the tubular member. 
     Clause 127. The system of Clause 126, wherein the conductive band is disposed on an inner surface of the tubular member. 
     Clause 128. The system of Clause 126, wherein the conductive band is disposed on an outer surface of the tubular member. 
     Clause 129. The system of any one of Clauses 120 to 128, wherein the electrode comprises a stent engaged with an inner surface of the tubular member. 
     Clause 130. The system of any one of Clauses 120 to 129, wherein the tubular member comprises an aspiration catheter. 
     Clause 131. The system of any one of Clauses 120 to 129, wherein the tubular member comprises a guide catheter. 
     Clause 132. The system of any one of Clauses 120 to 131, further comprising a suction source configured to supply negative pressure through the tubular member to aspirate a region adjacent to a distal portion of the tubular member. 
     Clause 133. The system of any one of Clauses 120 to 132, wherein the tubular member is an aspiration catheter having a proximal portion configured to be fluidically coupled to a suction source. 
     Clause 134. The system of any one of Clauses 120 to 133, further comprising a power supply having positive and negative terminals, the electrode being coupled to the negative terminal and the shaft being coupled to the positive terminal. 
     Clause 135. The system of Clause 134, wherein, when the medical device and the distal portion of the tubular member are in the presence of an electrolytic medium and voltage is supplied to the positive and negative terminals, current flows from the medical device the electrode. 
     Clause 136. The system of any one of Clauses 120 to 135, wherein the shaft comprises an electrically conductive wire extending along its length. 
     Clause 137. The system of Clause 136, wherein the shaft comprises an insulative coating surrounding the wire along at least a portion of its length. 
     Clause 138. The system of any one of Clauses 120 to 137, wherein the medical device comprises a thrombectomy device. 
     Clause 139. The system of any one of Clauses 120 to 138, wherein the medical device comprises a stent retriever. 
     Clause 140. The system of any one of Clauses 120 to 139, wherein the medical device comprises a removal device. 
     Clause 141. The system of any one of Clauses 120 to 140, wherein the medical device comprises a catheter. 
     Clause 142. The system of any one of Clauses 120 to 141, wherein a portion of the medical device is coated with a conductive material. 
     Clause 143. The system of Clause 142, wherein the conductive material comprises gold. 
     Clause 144. The system of any one of Clauses 120 to 143, wherein a portion of the medical device is coated with a non-conductive material. 
     Clause 145. The system of Clause 144, wherein the non-conductive material comprises parylene. 
     Clause 146. A method, comprising:
         disposing a distal portion of a catheter adjacent to a treatment site in the body, the catheter comprising an electrode disposed in the distal portion and coupled to a first electrical terminal of a power supply;   advancing an interventional element through the catheter to the treatment site, the interventional element coupled to a second electrical terminal of a power supply; and   supplying electric current to the second electrical terminal.       

     Clause 147. The method of Clause 146, further comprising ceasing the supplying of electric current to the second electrical terminal after a first time period. 
     Clause 148. The method of Clause 147, further comprising, after ceasing the supplying of electric current, proximally retracting the core member with respect to the catheter. 
     Clause 149. The method of any one of Clauses 147 to 148, wherein the first time period is less than about 5 minutes. 
     Clause 150. The method of any one of Clauses 147 to 149, wherein the first time period is less than about 2 minutes. 
     Clause 151. The method of any one of Clauses 146 to 150, wherein the electrode is coupled to the first electrical terminal via a conductive lead extending proximally along the catheter. 
     Clause 152. The method of Clause 151, wherein the conductive lead is disposed within a wall of the catheter. 
     Clause 153. The method of Clause 151, wherein the conductive lead is disposed along an external surface of the catheter. 
     Clause 154. The method of any one of Clauses 146 to 153, wherein the electrode comprises a conductive band extending at least partially circumferentially around the distal portion of the catheter. 
     Clause 155. The method of Clause 154, wherein the conductive band is disposed on an inner surface of the catheter. 
     Clause 156. The method of Clause 154, wherein the conductive band is disposed on an outer surface of the catheter. 
     Clause 157. The method of any one of Clauses 146 to 156, wherein the electrode comprises a stent engaged with an inner surface of the catheter. 
     Clause 158. The method of any one of Clauses 146 to 157, further comprising supplying negative pressure through the catheter to aspirate a region adjacent to the treatment site. 
     Clause 159. The method of any one of Clauses 146 to 158, wherein the treatment site in the body is proximate to or adjacent to a thrombus in a blood vessel. 
     Clause 160. The method of any one of Clauses 146 to 159, further comprising, after advancing the interventional element through the catheter, expanding the interventional element adjacent to a thrombus in a blood vessel. 
     Clause 161. The method of any one of Clauses 146 to 160, wherein the interventional element comprises a thrombectomy device. 
     Clause 162. The method of any one of Clauses 146 to 161, wherein the interventional element comprises a stent retriever. 
     Clause 163. The method of any one of Clauses 146 to 162, wherein the interventional element comprises a removal device. 
     Clause 164. The method of any one of Clauses 146 to 163, wherein the interventional element is coupled to the second electrical terminal of the power supply via a conductive pushwire. 
     Clause 165. The method of any one of Clauses 146 to 164, further comprising:
         arresting blood flow at the treatment site; and   after arresting the blood flow, supplying the electric current to the second electrical terminal.       

     Clause 166. The method of Clause 165, further comprising:
         ceasing the supplying of electric current to the second electrical terminal after a first time period; and   after ceasing the supplying of electric current, restoring blood flow at the treatment site.       

     Clause 167. The method of any one of Clauses 165 to 166, wherein arresting the blood flow comprises expanding a balloon of a balloon-guide catheter at a position proximal to the treatment site. 
     Clause 168. An aspiration device, comprising:
         an aspiration catheter having a distal end configured to be positioned adjacent to a thrombus in a blood vessel and a proximal end configured to be fluidically coupled to a suction source;   an electrode disposed at a distal portion of the aspiration catheter; and   a conductive lead coupled to the electrode and extending along a length of the catheter, the lead configured to be coupled to a positive terminal of an extracorporeal power supply.       

     Clause 169. The device of Clause 168, wherein the electrode comprises a conductive band extending at least partially circumferentially around the distal portion of the catheter. 
     Clause 170. The device of Clause 169, wherein the conductive band is disposed on an inner surface of the catheter. 
     Clause 171. The device of any one of Clauses 168 to 170, wherein the conductive lead comprises a wire disposed within a wall of the catheter. 
     Clause 172. The device of any one of Clauses 168 to 170, wherein the conductive lead comprises a wire disposed around an external surface of the catheter. 
     Clause 173. The device of any one of Clauses 168 to 172, further comprising:
         a second electrode; and   a second conductive lead coupled to the second electrode, the second conductive lead configured to be coupled to a negative terminal of the extracorporeal power supply.       

     Clause 174. The device of Clause 173, wherein the second electrode comprises a conductive band disposed at the distal portion of the catheter, and wherein the second conductive lead comprises a wire disposed within a wall of the catheter. 
     Clause 175. The device of Clause 173, wherein the second electrode comprises a conductive band disposed at the distal portion of the catheter, and wherein the second conductive lead comprises a wire disposed around an external surface of the catheter. 
     Clause 176. The device of Clause 173, wherein the second electrode comprises a flow-arrest element coupled to the distal portion of the catheter. 
     Clause 177. The device of Clause 173, wherein the second electrode is physically separate from the catheter. 
     Clause 178. The device of Clause 177, wherein the second electrode comprises a needle. 
     Clause 179. The device of Clause 177, wherein the second electrode comprises a grounding pad. 
     Clause 180. The device of any one of Clauses 168 to 179, further comprising a suction source configured to supply negative pressure through the catheter to aspirate a region adjacent to the distal portion of the catheter. 
     Clause 181. The device of any one of Clauses 168 to 180, further comprising a power supply having positive and negative terminals, the conductive lead being coupled to the positive terminal and a return electrode being coupled to the negative terminal. 
     Clause 182. A method, comprising:
         disposing a distal portion of a catheter adjacent to a treatment site in the body, the catheter comprising a first electrode disposed in the distal portion and coupled to a first electrical terminal of a power supply;   supplying electric current to the first electrical terminal; and   supplying negative pressure through the catheter to aspirate a region adjacent to the treatment site.       

     Clause 183. The method of Clause 182, further comprising disposing a second electrode at a position spaced apart from the first electrode, the second electrode coupled to a second electrical terminal of the power supply. 
     Clause 184. The method of Clause 183, wherein the first electrical terminal is positive, and wherein the second electrical terminal is negative. 
     Clause 185. The method of any one of Clauses 183 to 184, wherein the second electrode comprises a needle. 
     Clause 186. The method of any one of Clauses 183 to 184, wherein the second electrode comprises a grounding pad. 
     Clause 187. The method of any one of Clauses 183 to 184, wherein the second electrode comprises a conductive element disposed in the distal portion of the catheter. 
     Clause 188. The method of any one of Clauses 182 to 187, further comprising supplying the electric current to the first electrical terminal while supplying the negative pressure through the catheter. 
     Clause 189. The method of any one of Clauses 182 to 188, further comprising ceasing the supplying of electric current to the first electrical terminal after a first time period. 
     Clause 190. The method of Clause 189, wherein the first time period is less than about 5 minutes. 
     Clause 191. The method of Clause 189, wherein the first time period is less than about 2 minutes. 
     Clause 192. The method of any one of Clauses 182 to 191, wherein the first electrode is coupled to the first electrical terminal via a conductive lead extending proximally along the catheter. 
     Clause 193. The method of Clause 192, wherein the conductive lead is disposed within a wall of the catheter. 
     Clause 194. The method of Clause 192, wherein the conductive lead is disposed along an external surface of the catheter. 
     Clause 195. The method of Clause 182 to 194, wherein the first electrode comprises a conductive band extending at least partially circumferentially around the distal portion of the catheter. 
     Clause 196. The method of Clause 195, wherein the conductive band is disposed on an inner surface of the catheter. 
     Clause 197. The method of Clause 195, wherein the conductive band is disposed on an outer surface of the catheter. 
     Clause 198. The method of any one of Clauses 182 to 197, wherein the first electrode comprises a stent engaged with an inner surface of the catheter. 
     Clause 199. The method of any one of Clauses 182 to 198, wherein the treatment site in the body is proximate to or adjacent to a thrombus in a blood vessel. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE 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. 
         FIG. 1A  shows a perspective view of an electrically enhanced treatment system for retrieving material from a body lumen, in accordance with one or more embodiments of the present technology. 
         FIGS. 1B and 1C  are schematic views of different embodiments of the current generator illustrated in  FIG. 1A . 
         FIG. 2A  is a side schematic view of a portion of the treatment system of  FIG. 1A . 
         FIG. 2B  is a side schematic cross-sectional view of a portion of the treatment system shown in  FIG. 2A . 
         FIG. 3A  illustrates an interventional element with one or more coatings in accordance with embodiments of the present technology. 
         FIGS. 3B and 3C  are charts showing clot detachment forces for interventional elements coated with a conductive material and for non-coated interventional elements, in accordance with the present technology. 
         FIGS. 4A-4G  illustrate a method of removing clot material from a blood vessel lumen using an electrically enhanced treatment system. 
         FIG. 5  is a chart showing clot detachment forces for different interventional element embodiments under different environments. 
         FIGS. 6A-6B  illustrate a method of removing clot material from a blood vessel lumen using electrically enhanced aspiration. 
         FIGS. 7A-7E  illustrate sample waveforms for electrically enhanced removal of material from vessel lumens in accordance with one or more embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     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 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 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.). 
     I. SELECT EMBODIMENTS OF ELECTRICALLY ENHANCED TREATMENT SYSTEMS 
       FIG. 1A  illustrates a view of an electrically enhanced treatment system  10  according to one or more embodiments of the present technology. As shown in  FIG. 1A , the treatment system  10  can include a current generator  20  and a treatment device  40  having a proximal portion  40   a  configured to be coupled to the current generator  20  and a distal portion  40   b  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  40  includes an interventional element  100  at the distal portion  10   b , a handle  16  at the proximal portion  10   a , and a plurality of elongated shafts or members extending therebetween. For example, in some embodiments, such as that shown in  FIG. 1A , the treatment device  40  includes a first catheter  14  (such as a balloon guide catheter), a second catheter  13  (such as a distal access catheter or aspiration catheter) configured to be slidably disposed within a lumen of the first catheter  14 , a third catheter  12  (such as a microcatheter) configured to be slidably disposed within a lumen of the second catheter  13 , and a core member  11  configured to be slidably disposed within a lumen of the third catheter  12 . In some embodiments, the treatment device  40  does not include the second catheter  13 . The first catheter  14  can be coupled to the handle  16 , which provides proximal access to the core member  11  that engages the interventional element  100  at a distal end thereof. The current generator  20  may be coupled to a proximal portion of one or more of the core member  11 , the third catheter  12 , the second catheter  13 , and/or the first catheter  14  to provide an electrically charged environment at the distal portion  40   b  of the treatment device  40 , as described in more detail below. 
     In some embodiments, the treatment system  10  includes a suction source  25  (e.g., a syringe, a pump, etc.) configured to be fluidly coupled (e.g., via a connector  23 ) to a proximal portion of one or more of the first catheter  14 , the second catheter  13 , and/or the third catheter  12  to apply negative pressure therethrough. In some embodiments, the treatment system  10  includes a fluid source  27  (e.g., a fluid reservoir, a syringe, pump, etc.) configured to be fluidly coupled (e.g., via the connector  23 ) to a proximal portion of one or more of the first catheter  14 , the second catheter  13 , and/or the third catheter  12  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  20  can include an electrical generator configured to output medically useful electric current.  FIGS. 1B and 1C  are schematic views of different embodiments of the current generator  20 . With reference to  FIG. 1B , the current generator  20  can include a power source  22 , a first terminal  24 , a second terminal  26 , and a controller  28 . The controller  28  includes a processor  30  coupled to a memory  32  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  22  to deliver electric current according to certain parameters provided by the software, code, etc. The power source  22  of the current generator  20  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  20  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  20  can provide a voltage of about 2 volts to about 28 volts and a current of about 0.5 mA to about 20 mA. 
       FIG. 1C  illustrates another embodiment of the current generator  20 , in which the controller  28  of  FIG. 1B  is replaced with drive circuitry  34 . In this embodiment, the current generator  20  can include hardwired circuit elements to provide the desired waveform delivery rather than a software-based generator of  FIG. 1B . The drive circuitry  34  can include, for example, analog circuit elements (e.g., resistors, diodes, switches, etc.) that are configured to cause the power source  22  to deliver electric current via the first and second terminals  24 ,  26  according to the desired parameters. For example, the drive circuitry  34  can be configured to cause the power source  22  to deliver periodic waveforms via the first and second terminals  24 ,  26 . 
     As noted above, the current generator  20  may be coupled to a proximal portion of the core member  11 , and/or a proximal portion of the third catheter  12 , the second catheter  13 , and/or first catheter  14  to provide an electric current to the interventional element  100 . For example, in some embodiments, both terminals of the current generator  20  are coupled to the core member  11  such that the core member  11  functions as both a delivery electrode or conductive path (i.e., transmitting current from the current generator  20  to the treatment site) and a return electrode or conductive path (i.e., transmitting current from the treatment site to the current generator  20 ) (described in greater detail below with reference to  FIG. 2B ). In other embodiments, the return electrode can be separate from the core member  11 . For example, the return electrode can be carried by one or more of the third catheter  12 , the second catheter  13 , and/or first catheter  14 . In some embodiments, the return electrode can be provided via one or more external electrodes  29  ( FIG. 1A ), such as a needle puncturing the patient or a grounding pad applied to the patient&#39;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. 2A  is a side schematic view of a portion of the treatment device  40  shown in  FIG. 1A . The system  10  can include can include multiple (e.g., two or more), distinct conductive paths or channels for passing electrical current along the system  10 . The interventional element  100  can serve as one electrode (e.g., the delivery electrode) in electrical communication with a conductive path integrated into the core member  11 . Another of the conductive paths of the system  10  can be in electrical communication with another electrode (e.g., a return electrode). The various embodiments of the core member  11  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  100  along the bodily lumen. 
     As noted above, the interventional element  100  can serve as the delivery electrode and be electrically coupled to a positive terminal of the current generator  20  ( FIG. 1A ). As shown in  FIG. 2B , in some embodiments, the core member  11  can include an elongate conductive shaft  211  (e.g., a pushwire) extending along the length of the core member  11 . The shaft can be in electrical communication with the current generator  20  ( FIG. 1A ) at its proximal end and the interventional element  100  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  20  and the interventional element  100 . 
     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  29  ( FIG. 1A ), such as a needle or grounding pad that is applied to a patient&#39;s skin. The needle or grounding pad can be coupled via one or more leads to the current generator  20  to complete the electrical circuit. In some embodiments, the return electrode is carried by a surrounding catheter (e.g., third catheter  12 , second catheter  13 , and/or first catheter  14 ), as described in more detail below. 
     According to some embodiments, for example as shown in  FIG. 2A , the catheters  12 ,  13 , and  14  can each be formed as a generally tubular member extending along and about a central axis and terminating in a respective distal end  201 ,  202 , and  203 . According to some embodiments, the third catheter  12  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  12  can have a length that is at least 125 cm long, and more particularly may be between about 125 cm and about 175 cm long. Other designs and dimensions are contemplated. 
     The second catheter  13  can be sized and configured to be slidably receive the third catheter  12  therethrough. As noted above, the second catheter  13  can be coupled at a proximal portion to a suction source  25  ( FIG. 1A ) such as a pump or syringe in order to supply negative pressure to a treatment site. The first catheter  14  can be sized and configured to slidably receive both the second catheter  13  and the third catheter  12  therethrough. In some embodiments, the first catheter  14  is a balloon-guide catheter having an inflatable balloon or other expandable member that can be used to anchor the first catheter  14  with respect to a surrounding vessel. As described in more detail below with respect to  FIGS. 4A-4G , in operation the first catheter  14  can first be advanced through a vessel and then a balloon can be expanded to anchor the first catheter  14  in place and/or arrest blood flow from areas proximal of the balloon. Next, the second catheter  13  can be advanced through the first catheter  14  until its distal end  202  extends distally beyond the distal end  203  of the first catheter  14 . The second catheter  13  can be positioned such that its distal end  202  is adjacent a treatment site (e.g., a site of a blood clot within the vessel). The third catheter  12  may then be advanced through the second catheter  13  until its distal end  201  extends distally beyond the distal end  202  of the second catheter  13 . The interventional element  100  may then be advanced through the third catheter  12  for delivery to the treatment site. 
     According to some embodiments, the bodies of the catheters  12 ,  13 , and  14  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  204  is provided at a distal end region of the third catheter  12 . The electrode  204  can form an annular ring that extends entirely circumferentially about the central axis of the third catheter  12 . Alternatively or in combination, the electrode  204  can extend less than entirely circumferentially around the third catheter  12 . For example, the electrode  204  may be entirely disposed on one radial side of the central axis. By further example, the electrode  204  may provide a plurality of discrete, noncontiguous electrode sections about the central axis. Such sections of the electrode  204  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  201  can be a band, a wire, or a coil embedded in the wall of the third catheter  12 . According to some embodiments, the electrode  204  can be longitudinally separated from the distal end  201  of the third catheter  12  by a non-conductive portion of the third catheter  12 . Alternatively, a distal portion of the electrode  204  can extend to the distal end  201  of the third catheter  12 , such that the electrode  204  forms a portion of the distal end  201 . According to some embodiments, an inner surface of the electrode  204  can be flush with an inner surface of the third catheter  12 . Alternatively or in combination, the inner surface of the electrode  204  can extend more radially inwardly relative to the inner surface of the third catheter  12  (e.g., providing a “step”). Alternatively or in combination, the inner surface of the electrode  204  can extend less radially inwardly relative to the inner surface of the third catheter  12  (e.g., be recessed into the body). According to some embodiments, the electrode  201  can be surrounded radially by an outer section of the third catheter  12  to provide insulation from an external environment. In some embodiments, an outer surface of the electrode  204  can be flush with an outer surface of the third catheter  12  and can provide an exposed, radially outwardly facing electrode surface. In such instances, a radially inner section of the third catheter  12  can provide insulation from the environment within the lumen of the third catheter  12 . 
     The electrode  204  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  204  can have a fixed inner diameter or size, or a radially expandable inner diameter or size. In some embodiments, the electrode  204  is a “painted” electrode. The electrode can include platinum, platinum alloys (e.g., 92% platinum and 8% tungsten, 90% platinum and 10% iridium), gold, cobalt-chromium, stainless steel (e.g.,  304  or  316 ), nitinol, and combinations thereof, or any suitable conductive materials, metals or alloys. 
     In some embodiments, the electrode  204  can be a separate expandable member coupled to an outer surface of the third catheter  12 , for example a braid, stent, or other conductive element coupled to an outer surface of the distal portion of the third catheter  12 . 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  204  can be electrically connected to the current generator  20  via a conductive lead  205 . The conductive lead  205  can extend proximally along or within the wall of the third catheter  12  to or beyond the proximal end of the third catheter  12 . The conductive lead  205  can include more than one conductive path extending within the walls of the third catheter  12 . According to some embodiments, the conductive lead  205  can form a helical coil along or within at least a portion of the third catheter  12 . Alternatively or in combination, the conductive lead  205  can form a braided, woven, or lattice structure along or within at least a portion of the third catheter  12 . In some embodiments, the conductive lead  205  can be a conductive element (e.g., a wire, coil, etc.) wrapped around an external surface of the third catheter  12 . In such instances, the conductive lead  205  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  13  and/or the first catheter  14  can be similarly equipped with corresponding electrodes instead of or in addition to the third catheter  12  or the core member  11 . For example, the second catheter  13  may include an electrode  206  disposed at a distal end region of the second catheter  13 . The electrode  206  can be electrically connected to the current generator  20  ( FIG. 1A ) via a conductive lead  207  which extends proximally along the second catheter  13 . The configuration of the electrode  206  and the corresponding conductive lead  207  can be similar to any of the variations described above with respect to the electrode  204  and the conductive lead  205  of the third catheter  12 . 
     In some embodiments, the first catheter  14  includes an electrode  208  disposed at a distal end region of the first catheter  14 . The electrode  208  can be electrically connected to the current generator  20  ( FIG. 1A ) via a conductive lead  209  which extends proximally along the first catheter  14 . The configuration of the electrode  208  and the corresponding conductive lead  209  can be similar to any of the variations described above with respect to the electrode  204  and the conductive lead  205  of the third catheter  12 . 
     In various embodiments, the system can include any combination of the electrodes  204 ,  206 , and  208  described above. For example, the system may include the electrode  204  and the corresponding conductive lead  205  of the third catheter  12 , while the second catheter  13  and the first catheter  14  may be provided with no electrodes or conductive leads therein. In other embodiments, the system may only include the electrode  206  of the second catheter  13 , while the third catheter  12  and the first catheter  14  may be provided with no electrodes or conductive leads therein. In still other embodiments, the system may include only the electrode  208  of the first catheter  14 , while the third catheter  12  and the second catheter  13  are provided with no electrodes or corresponding conductive leads therein. In some embodiments, any two of the catheters  12 ,  13 , or  14  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. 2A , one or more of electrodes  204 ,  206 , or  208  can be coupled to a negative terminal of the current generator  20 , while the interventional element  100  can be coupled to the positive terminal of the current generator  20  via the core member  11 . As a result, when voltage is applied at the terminals and the interventional element  100  placed in the presence of blood (or any other electrolytic medium), current flows from the interventional element  100 , 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  12 ,  13 , or  14  as described above, or the core member  11 , or in some embodiments the return electrode can be an external electrode  29  ( FIG. 1A ) 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  100 . In various embodiments, the interventional element  100  may be omitted altogether (as in  FIGS. 6A-6B  described below), or the interventional element  100  may be included but may not be electrically coupled to the current generator  20 . In such cases, a catheter-based electrode (e.g., the electrode  204  carried by the third catheter  12 , the electrode  206  carried by the second catheter  13 , or the electrode  208  carried by the first catheter  14 ) 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  13  may include a delivery electrode in the form of a conductive band disposed on an inner surface of the catheter  13 , in addition to a return electrode in the form of a conductive band disposed on an outer surface of the catheter  13 . 
     As described in more detail in  FIG. 2B , in some embodiments the return electrode can be integrated into the core member  11  of the treatment system  10 , such that the core member  11  carries two separate conductive paths along its length.  FIG. 2B  is a side schematic cross-sectional view of a portion of the treatment system shown in  FIG. 2A , in accordance with some embodiments. As shown in  FIG. 2B , the core member  11  includes an elongate conductive shaft  211  and an elongate tubular member  212  having a lumen through which the shaft  211  extends. The shaft  211  has a distal portion  210 , and the tubular member  212  has a distal portion  218 . Both the shaft  211  and the tubular member  212  are electrically conductive along their respective lengths. In some embodiments, the positions of the shaft  211  and the tubular member  212  are fixed relative to one another. For example, in some embodiments the shaft  211  is not slidable or rotatable with respect to the tubular member  212  such that the core member  11  can be pushed or pulled without relative movement between the shaft  211  and the tubular member  212  and/or other individual components of the core member  11 . 
     In some embodiments, the shaft  211  can be a solid pushwire, for example a wire made of Nitinol, stainless steel, or other metal or alloy. The shaft  211  may be thinner than would otherwise be required due to the additional structural column strength provided by the surrounding tubular member  212 . The tubular member  212  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  212  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  212  can be made of stainless steel (e.g., 304 SS), Nitinol, and/or other alloy. In at least some embodiments, the tubular member  212  can have a laser cut pattern to achieve the desired mechanical characteristics (e.g., column strength, flexibility, kink-resistance, etc.). 
     The core member  11  can also include an adhesive or a mechanical coupler such as a crimped band or marker band  220  disposed at the distal end of the core member  11 , and the marker band  220  can optionally couple the distal end of the core member  11  to the interventional element  100 . The marker band  220  can be radiopaque, for example including platinum or other radiopaque material, thereby enabling visualization of the proximal end of the interventional element  100  under fluoroscopy. In some embodiments, additional radiopaque markers can be disposed at various locations along the treatment system  10 , for example along the shaft  211 , the tubular member  212 , or the interventional element  100  (e.g., at the distal end, or along the length, of the interventional element  100 ). 
     In at least some embodiments, the core member  11  also includes a first insulating layer or material  222  extending between the shaft  211  and the surrounding tubular member  212 . The first insulating material  222  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  222  extends along substantially the entire length of the shaft  211 . In some embodiments, the first insulating material  222  separates and electrically insulates the shaft  211  and the tubular member  212  along the entire length of the tubular member  212 . In some embodiments, the first insulating material  222  does not cover the proximal-most portion of the shaft  211 , providing an exposed region of the shaft to which the current generator  20  ( FIG. 1A ) can be electrically coupled. In some embodiments, for example, the first insulating material  222  terminates proximally at the proximal terminus of the shaft, and the current generator  20  ( FIG. 1A ) can electrically couple to the shaft  211  at its proximal terminus, for example using a coaxial connector. 
     The core member  11  can additionally include a second insulating layer or material  224  surrounding the tubular member  212  along at least a portion of its length. The second insulating layer  224  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  218  of the tubular member  212  is not covered by the second insulating layer  224 , leaving an exposed conductive surface at the distal portion  218 . In some embodiments, the length of the exposed distal portion  218  of the tubular member  212  can be at least (or equal to) 1, 2, 3, 4, 5, 6, or more inches. In some embodiments, the length of the exposed distal portion  218  of the tubular member  212  can be between at least 1 and 10 inches, or between 2 inches and 8 inches, or between 3 and 7 inches, or between 4 and 6 inches, or about 5 inches. This exposed portion of the distal portion  218  of the tubular member  212  provides a return path for current supplied to the delivery electrode (e.g. the entirety or a portion of the interventional element  100 ), as described in more detail below. In some embodiments, the second insulating material  224  does not cover the proximal-most portion of the tubular member  212 , providing an exposed region of the tubular member  212  to which the current generator  20  ( FIG. 1A ) can be electrically coupled. In some embodiments, the second insulating material  224  proximally terminates at the proximal terminus of the tubular member  212 , and the current generator  20  can electrically couple to the tubular member  212  at its proximal terminus, for example using a coaxial connector. 
     The core member  11  can also include a retraction marker in the proximal portion of the tubular member  212 . The retraction marker can be a visible indicator to guide a clinician when proximally retracting an overlying catheter with respect to the core member  11 . 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  218  of the tubular member  212  is positioned distally beyond a distal end of the catheter. In this position, the exposed distal portion  218  of the tubular member  212  is exposed to the surrounding environment (e.g., blood, tissue, etc.), and can serve as a return electrode for the core member  11 . 
     The proximal end of the shaft  211  can be electrically coupled to the positive terminal of the current generator  20 , and the proximal end of the tubular member  212  can be electrically coupled to the negative terminal of the current generator  20 . During operation, the treatment system  10  provides an electrical circuit in which current flows from the positive terminal of the current generator  20 , distally through the shaft  211 , the interventional element  100 , and the surrounding media (e.g., blood, tissue, thrombus, etc.) before returning back to the exposed distal portion  218  of the tubular member, proximally through the tubular member  212 , and back to the negative terminal of the current generator  20  ( FIG. 1A ). 
     As noted above, the current generator  20  ( FIG. 1A ) 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  20  may be integrated into the core member  11  or may be removably coupled to the core member  11 , for example via clips, wires, plugs or other suitable connectors. Particular parameters of the energy provided by the current generator  20  are described in more detail below with respect to  FIGS. 7A-7E . 
     In certain embodiments, the polarities of the current generator  20  can be switched, so that the negative terminal is electrically coupled to the shaft  211  and the positive terminal is electrically coupled to the tubular member  212 . This can be advantageous when, for example, attempting to attract predominantly positively charged material to the interventional element  100 , 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. 
     II. SELECT EMBODIMENTS OF INTERVENTIONAL ELEMENTS FOR USE WITH THE TREATMENT SYSTEMS DISCLOSED HEREIN 
     Referring still to  FIGS. 2A and 2B , in some embodiments the interventional element  100  can be a metallic or electrically conductive thrombectomy device. The interventional element  100  can have a low-profile, constrained or compressed configuration (not shown) for intravascular delivery to the treatment site within the third catheter  12 , and an expanded configuration for securing and/or engaging clot material and/or for restoring blood flow at the treatment site. The interventional element  100  has a proximal portion  100   a  that may be coupled to the core member  11  and a distal portion  100   b . The interventional element  100  further includes an open cell framework or body  226  and a coupling region  228  extending proximally from the body  226 . In some embodiments, the body  226  of the interventional element  100  can be generally tubular (e.g., cylindrical), and the proximal portion  100   a  of the interventional element  100  can taper proximally to the coupling region  228 . 
     In various embodiments, the interventional element  100  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  100  may be a stent and/or stent retriever, such as Medtronic&#39;s Solitaire™ Revascularization Device, Stryker Neurovascular&#39;s Trevo® ProVue™ Stentriever, or other suitable devices. In some embodiments, the interventional element  100  may be a coiled wire, a weave, and/or a braid formed of a plurality of braided filaments. Examples of suitable interventional elements  100  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 embodiments, the interventional element  100  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  12 . The mesh structure may include a plurality of struts  101  and open spaces  103  between the struts  101 . In some embodiments, the struts  101  and spaces  103  may be situated along the longitudinal direction of the interventional element  100 , the radial direction, or both. 
     As depicted in  FIG. 2A , the interventional element  100  may comprise a working length WL portion and a non-working length NWL portion. The portion of the interventional element  100  in the working length WL may be configured to interlock, capture, and/or engage a thrombus. The portion of the interventional element  100  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. 2A , a distal terminus of the working length WL portion is proximal of the distal terminus of the interventional element  100  (i.e., the working length WL portion is spaced apart from the distal terminus of the interventional element  100 ), and the non-working length NWL portion is disposed between the working length WL and the band  220  and/or the distal end of the core member  11 . 
     In some embodiments, the non-working length NWL portion of the interventional element  100  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  11  to the interventional element  100  is only exposed to the surrounding media along the working length WL portion of the interventional element  100 . This can advantageously concentrate the electrically enhanced attachment effect along the working length WL of the interventional element  100 , 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  100  (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  100  having an exposed conductive surface. 
     In some embodiments, the interventional element  100  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  100 . The conductive material may be applied to the interventional element  100  via electrochemical deposition, sputtering, vapor deposition, dip-coating, and/or other suitable means.  FIG. 3A , for example, is a cross-sectional view of a strut  101  of the interventional element  100  having a conductive material  301  disposed thereon. Although the strut  101  shown in  FIG. 3A  has a generally square or rectangular cross-sectional shape, in some embodiments the interventional element  100  includes one or more struts or filaments having other cross-sectional shapes (e.g., circle, oval, etc.). 
     As shown in  FIG. 3A , the strut  101  has a surface comprised of an outer portion  101   a  facing away from a lumen of the interventional element  100 , an inner portion  101   c  facing toward the lumen, and side portions  101   b  and  101   d  extending between the outer and inner portions  101   a ,  101   c . In some embodiments, such as that shown in  FIG. 3A , the conductive material  301  may be disposed only at the outer portion  101   a  of the strut  101  and the inner and side portions  101   b - d  may be exposed or otherwise not in contact with or covered by the conductive material  301 . In some embodiments, the conductive material  301  may be disposed only on the inner portion  101   c  of the surface, only on one of the side portions  101   b ,  101   d , or on any combination of the surface portions  101   a - d.    
     In some aspects of the present technology, the conductive material  301  is disposed only on the working length WL portion of the interventional element  100  such that the proximal and distal portions  100   a ,  100   b  of the interventional element  100  are exposed. Because the conductive material  301  has a much lower resistance than the underlying material comprising the interventional element  100 , current delivered to the interventional element  100  concentrates along the working length WL portion. In several of such embodiments, the conductive material  301  may be disposed only on the outer portion  101   a  of the strut surface along the working length WL portion. In other embodiments, the conductive material  301  may be disposed on all or a portion of the strut surface along all or a portion of the length of the interventional element  100 . 
     In some embodiments, a first portion of the interventional element  100  is covered by the conductive material  301  and a second portion of the interventional element  100  is covered by an insulative or dielectric material (e.g., Parylene). For example, in some embodiments the outer portion  101   a  of the strut surface is covered by a conductive material while an inner portion  101   c  of the strut surface is covered by an insulative material. In some embodiments, the working length WL portion of the interventional element  100  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  301  may be disposed on all or a portion of the strut surface along all or a portion of the length of the interventional element  100 , and the insulative material may be disposed on those portions of the strut surface and/or working length not covered by the conductive material. 
       FIGS. 3B and 3C  demonstrate the improved adhesion strength between clot material and the interventional element  100  as a result of the conductive material. The charts of  FIGS. 3B and 3C , for example, show detachment forces for gold-coated and non-coated (“SS”) interventional elements  100  that received electric current while exposed to sheep&#39;s or pig&#39;s blood, respectively. For these experiments, a blood clot was manufactured by mixing fibrinogen, blood, thrombin and calcium chloride. A representative interventional element was immersed or deployed in contact with the blood clot to mimic clinical deployment and positive charge was applied to it for a specified duration. The whole assembly was immersed in blood and flow was applied at 150 mL/min. The composition of the manufactured blood clot and the parameters of the applied energy (e.g., duration, amplitude, etc.) were generally the same for all samples in both experiments. The assembly (blood clot and interventional element) was then removed from the experimental setup and the blood clot was detached from the interventional element using a lap-shear test with an Instron. The detachment force was measured and is reported in the charts. In both charts, the average detachment force for the gold-coated samples is at least two times the average detachment force for the non-coated samples. 
     III. SELECT METHODS OF USE 
       FIGS. 4A-4G  illustrate a method of removing clot material CM from the lumen of a blood vessel V using the treatment system  10  of the present technology. As shown in  FIG. 4A , the first catheter  14  can be advanced through the vasculature and positioned within the blood vessel such that a distal portion of the first catheter  14  is proximal of the clot material CM. As shown in  FIG. 4B , the second catheter  13  may be advanced through the first catheter  14  until a distal portion of the second catheter  13  is at or proximal to the clot material CM. Next, the third catheter  12  may be advanced through the second catheter  13  so that a distal portion of the third catheter  12  is positioned at or near the clot material CM. In some embodiments, the third catheter  12  may be positioned such that a distal terminus of the third catheter  12  is distal of the clot material CM. The interventional element  100  may then be advanced through the third catheter  12  in a low-profile configuration until a distal terminus of the interventional element  100  is at or adjacent the distal terminus of the third catheter  12 . 
     As shown in  FIG. 4C , the third catheter  12  may be withdrawn proximally relative to the interventional element  100  to release the interventional element  100 , thereby allowing the interventional element  100  to self-expand within the clot material CM. As the interventional element  100  expands, the interventional element  100  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  100  may be expanded distal of the clot material CM such that no portion of the interventional element  100  is engaging the clot material CM while the interventional element  100  is in the process of expanding toward the vessel wall. In some embodiments, the interventional element  100  is configured to expand into contact with the wall of the vessel V, or the interventional element  100  may expand to a diameter that is less than that of the blood vessel lumen such that the interventional element  100  does not engage the entire circumference of the blood vessel wall. 
     Once the interventional element  100  has been expanded into engagement with the clot material CM, the interventional element  100  may grip the clot material CM by virtue of its ability to mechanically interlock with the clot material CM. The current generator  20 , which is electrically coupled to the proximal end of the core member  11 , can deliver a current to the interventional element  100  before or after the interventional element  100  has been released from the third catheter  12  into the blood vessel and/or expanded into the clot material CM. The interventional element  100  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  100  can attract negatively charged constituents of the clot material CM, thereby enhancing the grip of the interventional element  100  on the clot material CM. This allows the interventional element  100  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  12 - 14  and/or one or more of the catheters  12 - 14  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  20  and the interventional element  100 . 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  14 ,  13 ,  12 , the interventional element  100 , etc.). 
       FIGS. 4D-4F  illustrate optional processes that may be performed before, during, and/or after deployment of the interventional element  100 . With reference to  FIG. 4D , in some methods fluid F may be delivered to the treatment site via the second catheter  13  and/or third catheter  12  while current is being delivered to the interventional element  100 . Fluid delivery may occur before or while the interventional element  100  is engaging the thrombus, and may coincide with the entire duration of current delivery or just a portion thereof. 
       FIG. 5  is a chart showing clot detachment forces for different interventional elements of the present technology under different environmental conditions (as indicated along the x-axis). For these experiments, a blood clot was manufactured by mixing fibrinogen, blood, thrombin and calcium chloride. A representative interventional element was immersed or deployed in contact with the blood clot to mimic clinical deployment and positive charge was applied to it for a specified duration. The whole assembly was immersed in blood and flow was applied at 150 mL/min (“Flow”) or 0 mL/min (“No Flow”). The composition of the manufactured blood clot and the parameters of the applied energy (e.g., duration, amplitude, etc.) were generally the same for all samples in both experiments. The assembly (blood clot and interventional element) was then removed from the experimental setup and the blood clot was detached from the interventional element using a lap-shear test with an Instron. The detachment force was measured and is reported in  FIG. 5 . As demonstrated by the chart shown in  FIG. 5 , the inventors have observed that the presence of blood flow at the treatment site reduces adhesion between an electrically charged interventional element and a blood clot by approximately two-fold (see “NiTi (No Flow)” vs. “NiTi (Flow)”, and “NiTi+Gold (No Flow)” vs. “NiTi+Gold (Flow)”).).  FIG. 5  also demonstrates that the adhesion forces for a gold-coated interventional element are at least two times the adhesion forces for a non-coated interventional element (see “NiTi (No Flow)” vs. “NiTi+Gold (No Flow)”, and “NiTi (Flow)” vs. “NiTi+Gold (Flow)”). 
     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, the inventors have also observed that infusion of a fluid F having a higher ion concentration than blood increases 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. The same experimental setup described above was used and the blood was replaced by saline with flow at 150 mL/min. The inventors observed that the adhesive force was approximately 35% higher when saline was infused at the treatment site than it was in the presence of autologous blood alone. In some embodiments, infusion of the fluid F may occur in the presence of blood flow, or without blood flow present (the latter condition being induced, for example, by inflation of the expandable element  401  on the first catheter  14 ). Suitable fluids include, for example, saline, contrast solution, and other fluids having a higher ion concentration than blood. Additionally, the delivery of fluid F at the treatment site may also reduce new clot formation on the interventional element  100 , which may occur in the presence of blood and direct or pulsatile electric current. 
     Referring now to  FIG. 4E , in some instances aspiration may be applied to the treatment site via the second catheter  13 . For example, following deployment of the interventional element  100 , the third catheter  12  can be retracted and removed from the lumen of the second catheter  13 . The treatment site can then be aspirated via the second catheter  13 , for example via a suction source such as a pump or syringe coupled to a proximal portion of the second catheter  13 . In some embodiments, following expansion of the interventional element  100 , the treatment site is aspirated concurrently with supplying electrical energy to the interventional element  100  via the current generator  20 . 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  13 , 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  100  without risking deleterious effects of new clot formation. Additionally, aspiration can capture any gas bubbles formed along the interventional element  100  or marker band  220  ( FIG. 2A ) during application of electrical energy to the interventional element  100 , which can improve patient safety during the procedure. 
     In some embodiments, aspiration is applied while the interventional element  100  is retracted into the second catheter  13 . Aspiration at this stage can help secure the clot material CM within the second catheter  13  and prevent any dislodged portion of the clot material CM from escaping the second catheter  13  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  100  as well as before, during, or after retraction of the interventional element  100  into the second catheter  13 . 
     With reference to  FIGS. 4B-4F , at any time before, during, and/or after deployment of the interventional element  100 , 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  FIGS. 4B-4F , the first catheter  14  may be a balloon guide catheter having a balloon  401  at its distal portion. The balloon  401  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  401 . 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  100  is deployed and eventually withdrawn to remove the thrombus. For example,  FIGS. 4B-4F  show the balloon  401  blocking flow from a portion of the artery proximal of the balloon toward the interventional element  100  and treatment area, while the second catheter  13  and third catheter  12  are positioned at the treatment site ( FIG. 4B ), while the interventional element  100  is expanded within the clot material CM ( FIG. 4C ), while fluid is infused at the treatment site ( FIG. 4D ), and while aspiration is applied at the treatment site ( FIG. 4E ). Although the balloon  401  is shown in an expanded state in each of  FIGS. 4B-4F , it will be appreciated that the balloon  401  may be in an unexpanded state and/or deflated at any time throughout the procedure to allow blood flow. 
     As shown in  FIG. 4F , in some embodiments the flow arrest element may be a balloon  403  coupled to the second catheter  13  (such as a distal access catheter). In such embodiments, the first catheter  14  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  13 . For example, in such embodiments, the first catheter  14  may be a sheath or support catheter. The balloon  403  may be inflated at a location distal of the distal end of the first catheter  14 , 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  100  is deployed and engaging the thrombus CM, electric current may be delivered to the interventional element  100  to positively charge the interventional element  100 , thereby enhancing clot adhesion to the interventional element  100 . As previously discussed with reference to  FIG. 5 , the inventors have observed improved electrically enhanced clot adhesion in the absence of blood flow. As such, it may be especially beneficial to arrest flow (e.g., via a flow arrest element on the first or second catheter  14 ,  13 ) while the interventional element  100  is charged, and while expanding the interventional element  100  within the thrombus and/or when withdrawing the thrombus proximally. 
     With reference to  FIG. 4G , while the interventional element  100  is engaged with the clot material CM, the clot material CM can be removed. For example, the interventional element  100 , with the clot material CM gripped thereby, can be retracted proximally (for example, along with the second catheter  13  and, optionally, the third catheter  12 ). The second catheter  13 , interventional element  100 , 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  100  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  100  can maintain an enhanced or electrically and/or electrostatically enhanced grip on the clot material CM during retraction. In other embodiments, the current generator  20  may cease delivery of electrical signals to the interventional element  100  prior to retraction of the interventional element  100  with respect to the vessel V. In some embodiments, the interventional element  100  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. 
       FIGS. 6A-6B  illustrates another method of removing clot material from the lumen of a blood vessel V using embodiments of the present technology. As shown in  FIG. 6A , a catheter  603  (such as second catheter  13 ) may be advanced through a vessel V to a position adjacent to clot material CM. The catheter  603  can be advanced through a surrounding catheter  604 , for example a balloon-guide catheter having a balloon  601  or other element configured to expand into contact with the vessel wall to secure the catheter  604  in position against the wall of the vessel V and/or to partially or completely arrest flow. In other embodiments, a surrounding sheath or support catheter can be used in place of the catheter  604 . In still other embodiments, the catheter  604  can be omitted and the catheter  603  can be advanced directly through the vessel V to the treatment site. 
     While in the position shown in  FIG. 6A , negative pressure can be supplied to the catheter  603  to aspirate the area adjacent to the clot material CM. For example, the catheter  603  can be fluidically coupled to the suction source  25  ( FIG. 1A ) at a proximal portion of the catheter  603 . Additionally, electrical signals can be supplied to the catheter  603  via the current generator  20  to electrically charge a distal portion of the catheter  603 . For example, as described above with respect to  FIG. 2A , in some embodiments the catheter  603  can be generally similar to second catheter  13  and can include a first electrode  206  disposed at its distal portion. The first electrode can be any electrically conductive element, for example a conductive band extending around an inner or outer surface of the catheter  603 , a stent engaged with an inner surface of the second catheter  603 , etc. The first electrode can be electrically coupled to a conductive lead that extends proximally along the catheter  603  and is coupled at its proximal end to the positive terminal of current generator  20 . The conductive lead can be, for example, a wire, coil, or other conductive element carried by and/or coupled to the catheter  603 . In some embodiments, the conductive lead is embedded within a wall of the second catheter  603 . In other embodiments, the conductive lead is disposed along an external surface of the catheter  603  (e.g., helically wound around the outer surface of the catheter  603  along its length). The conductive lead can be covered with insulative material along a portion of its length, for example parylene, PTFE, or other suitable insulative coating. 
     The negative terminal of the current generator  20  can be coupled to a return electrode to complete the electrical circuit with the first electrode disposed on the catheter  603 . In some embodiments, the return electrode can be an external electrode (e.g., a needle or a grounding pad coupled to the patient&#39;s skin). In other embodiments, the return electrode can be carried by a separate catheter, for example the electrode  208  of the catheter  604  shown in  FIG. 2A . In some embodiments, the return electrode can be carried by the catheter  603  at a position spaced apart from the first electrode. For example, the first electrode can be a conductive element such as a band or ring disposed at a position spaced apart from the first electrode. In some embodiments, the first electrode may be exposed along a radially inner surface of the catheter  603 , while the return electrode may be exposed along a radially outer surface of the catheter  603 . In some embodiments, the return electrode can be a separate expandable member coupled to an outer surface of the catheter  603  (e.g., the balloon  403  of  FIG. 4G  or other expandable member having a conductive element such as a metallic braid therein). 
     When the first and second electrodes are coupled to the positive and negative terminals, respectively, of the current generator  20 , the distal end of the catheter  603  becomes positively charged and attracts negatively charged constituents in the blood and clot material CM. This electrical attraction promotes movement of the clot material CM into the catheter  603 , adhesion of the clot material CM to the inner surface of the catheter  603 , and retention of the clot material CM in the lumen of the catheter  603 . 
     In various embodiments, aspiration can be performed via the catheter  603  before, during, and/or after supplying electrical energy to the first electrode via the current generator  20 . In some embodiments, the electrical signals can continue to be applied while the catheter  603  and attached clot material CM are retracted proximally through the vessel V towards the catheter  604 . In some embodiments, the current generator  20  can cease to supply electrical signals to the first electrode, while negative pressure can continue to be supplied to the catheter  603 . 
     In  FIG. 6B , the clot material CM has been moved to at least partially enter the catheter  603 . In some embodiments, the clot material CM can substantially block the lumen of the catheter  603 , thereby creating a “corking” effect that may be noticeable to a clinician supplying negative pressure to the catheter  603 . Once the catheter  603  is corked with the clot material CM, it becomes increasingly difficult to supply continued negative pressure to the catheter  603 . This corking effect can indicate to a clinician that the clot material CM has been engaged by the catheter  603  and that the clot material CM and catheter  603  can be retracted through the vessel V and into the catheter  604  or other surrounding catheter. In some embodiments, the current generator  20  can continue to supply electrical signals to the catheter  603  and the return electrode during retraction, while in other embodiments the current generator  20  can cease supplying electrical signals during retraction of the catheter  603  and the clot material CM. 
     IV. SELECT EMBODIMENTS OF WAVEFORMS FOR ELECTRICALLY ENHANCED RETRIEVAL 
       FIGS. 7A-7E  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  FIGS. 1A-6B , 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. 7E ) 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. 
       FIGS. 7A-7D  illustrate various periodic waveforms that can be used with the devices and methods described above with respect to  FIGS. 1A-6B , as well as with other devices and techniques.  FIG. 7E  illustrates a continuous uniform DC electrical signal which can also be used in some embodiments. Referring to  FIGS. 7A-7D , electrical power can be delivered according to these waveforms as pulsed direct current.  FIGS. 7A and 7B  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. 7C  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. 7C  delivers additional efficacy compared to the triangular waveform of  FIG. 7B  while nonetheless delivering less overall energy than the square waveform of  FIG. 7A . This is because the delivered energy is proportional to the square of current and the brief high peak in the composite waveform of  FIG. 7C  ensures that current is supplied without dispensing excessive energy.  FIG. 7D  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 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, or no more than 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. 
     Table 1 presents a range of values for power delivery parameters of different waveforms. For each of the conditions set forth in Table 1, a resistance of 1 kohm and a frequency of 1 kHz (for the Square, Triangle, and Composite conditions) was used. The Constant conditions represent a continuous and steady current applied for the duration, i.e. 100% duty cycle. The Peak Current 1 column represents the peak current for the corresponding waveform. For the Composite conditions, the Peak Current 2 column indicates the peak current of the second portion of the waveform. For example, referring back to  FIG. 7C , Peak Current 1 would correspond to the current at the top of the triangular portion of the waveform, while Peak Current 2 would correspond to the current at the top of the square portion of the waveform. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 Total 
                 Total 
               
               
                   
                 Peak 
                 Peak 
                 Duty 
                 Duty 
                 Peak 
                 Pulse 
                 Total 
                 Total 
                 Energy 
                 Energy 
               
               
                   
                 Current 1 
                 Current 2 
                 Cycle 1 
                 Cycle 2 
                 Voltage 
                 Width 
                 Time 
                 Charge 
                 (@ R = 1000 
                 (@ R = 50 
               
               
                 Condition 
                 (mA) 
                 (mA) 
                 (%) 
                 (%) 
                 (V) 
                 (ms) 
                 (s) 
                 (mC) 
                 ohm) (mJ) 
                 ohm) (mJ) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Constant 1 
                 2 
                 0 
                 100 
                 0 
                 2 
                 n/a 
                 120 
                 240 
                 480 
                 24 
               
               
                 Constant 2 
                 2 
                 0 
                 100 
                 0 
                 2 
                 n/a 
                 60 
                 120 
                 240 
                 12 
               
               
                 Constant 3 
                 10 
                 0 
                 100 
                 0 
                 10 
                 n/a 
                 60 
                 600 
                 6000 
                 300 
               
               
                 Constant 4 
                 20 
                 0 
                 100 
                 0 
                 20 
                 n/a 
                 60 
                 1200 
                 24000 
                 1200 
               
               
                 Constant 5 
                 10 
                 0 
                 100 
                 0 
                 10 
                 n/a 
                 120 
                 1200 
                 12000 
                 600 
               
               
                 Constant 6 
                 1 
                 0 
                 100 
                 0 
                 1 
                 n/a 
                 120 
                 120 
                 120 
                 6 
               
               
                 Constant 7 
                 0.5 
                 0 
                 100 
                 0 
                 1 
                 n/a 
                 120 
                 60 
                 30 
                 1.5 
               
               
                 Constant 8 
                 0.5 
                 0 
                 100 
                 0 
                 1 
                 n/a 
                 60 
                 30 
                 15 
                 0.75 
               
               
                 Square 1 
                 10 
                 0 
                 10 
                 0 
                 10 
                 0.1 
                 120 
                 120 
                 1200 
                 60 
               
               
                 Square 2 
                 4 
                 0 
                 50 
                 0 
                 4 
                 0.5 
                 120 
                 240 
                 960 
                 48 
               
               
                 Square 3 
                 20 
                 0 
                 10 
                 0 
                 20 
                 0.1 
                 120 
                 240 
                 4800 
                 240 
               
               
                 Square 4 
                 20 
                 0 
                 10 
                 0 
                 20 
                 0.1 
                 60 
                 120 
                 2400 
                 120 
               
               
                 Square 5 
                 10 
                 0 
                 10 
                 0 
                 10 
                 0.1 
                 60 
                 60 
                 600 
                 30 
               
               
                 Triangle 1 
                 10 
                 0 
                 10 
                 0 
                 10 
                 0.1 
                 120 
                 60 
                 1200 
                 60 
               
               
                 Triangle 2 
                 20 
                 0 
                 10 
                 0 
                 20 
                 0.1 
                 120 
                 120 
                 4800 
                 240 
               
               
                 Composite 1 
                 20 
                 1 
                 10 
                 20 
                 20 
                 0.3 
                 120 
                 144 
                 4824 
                 264 
               
               
                 Composite 2 
                 10 
                 2 
                 10 
                 20 
                 10 
                 0.3 
                 120 
                 108 
                 1296 
                 156 
               
               
                   
               
            
           
         
       
     
     As seen in Table 1, 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 4, a peak current of 20 mA corresponds to a total energy delivered of 24,000 mJ, while condition Square 3 delivers a peak current of 20 mA with a total energy of only 4,800 mJ. Conditions Triangle 2 and Composite 1 similarly deliver lower total energy while maintaining a peak current of 20 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 1 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 3 has a peak current of 20 mA and a total charge delivered of 240 mC, while condition Triangle 2 has a peak current of 20 mA but a total charge delivered of only 120 mC, and condition Composite 1 has a peak current of 20 mA and a total charge delivered of only 144 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 1 represents a series of waveforms with a single frequency (1 kHz), 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 1 Hz and 1 MHz, between 1 Hz and 1 kHz, or between 500 Hz to 1 kHz. 
     V. CONCLUSION 
     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.