System for forming a fistula

Abstract

A system for forming a fistula includes a first catheter, a second catheter, one or more magnetic field sensors, a user output device, and a control unit. The first catheter includes a fistula forming element and one or more first catheter magnetic elements. The second catheter includes one or more second catheter magnetic elements. The one or more magnetic field sensors are configured to output a magnetic field signal. The control unit is configured to determine a separation distance between the first catheter and the second catheter based on the magnetic field signals from the one or more magnetic field sensors, and output a ready signal using the user output device in response to determining that the separation distance between the first catheter and the second catheter is a predetermined distance or less.

Description

Technical Field

[0001] The present specification relates generally to systems and methods for forming a fistula, and more particularly to systems and methods for forming a fistula using a first catheter and a second catheter, wherein a magnetic field sensor allows determination of the proper position of the catheters for forming the fistula. Background Art

[0002] Fistula is usually a passage formed between two internal organs. Forming a fistula between two blood vessels can have one or more beneficial functions. For example, forming a fistula between an artery and a vein can provide a passage into the vascular system for hemodialysis patients. Specifically, forming a fistula between an artery and a vein allows blood to flow quickly between blood vessels while bypassing capillaries. Then a needle, a catheter or other cannula can be inserted into a blood vessel near the fistula to extract blood from the circulatory system, pass it through a dialysis machine, and then return it to the body. The accelerated flow provided by the fistula can provide effective hemodialysis. Usually, the formation of a fistula requires surgical dissection of the target vein, transecting and moving the vein to perform surgical anastomosis to the artery. These fistulas typically have a first failure rate of about 30-60% (failure before the patient receives dialysis), and the fistula needs 1 to 12 months (e.g., 4-8 weeks) to be available for dialysis. It may be useful to find an improved method for forming a fistula between two blood vessels. Summary of the invention

[0003] These and additional features provided by the embodiments described herein will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings.

[0004] In one embodiment, a system for forming a fistula includes a first catheter configured to be advanced through a first tube, a second catheter configured to be advanced through a second tube, one or more magnetic field sensors, a user output device configured to output a ready signal, and a control unit communicatively coupled to the one or more magnetic field sensors and the user output device. The first catheter includes a fistula forming element and one or more first catheter magnetic elements. The second catheter includes one or more second catheter magnetic elements. The one or more first catheter magnetic elements and the one or more second catheter magnetic elements are configured to attract / pull the first catheter and the second catheter together. The one or more magnetic field sensors are configured to output a magnetic field signal indicating the magnitude of a magnetic field generated between the one or more first catheter magnetic elements and the one or more second catheter magnetic elements. The control unit is configured to receive magnetic field signals from the one or more magnetic field sensors, determine the separation distance of the first catheter and the second catheter based on the magnetic field signals from the one or more magnetic field sensors, and output a ready signal using the user output device in response to determining that the separation distance of the first catheter and the second catheter is a predetermined distance or less, wherein the ready signal indicates the correct alignment and position of the first catheter and the second catheter to form a fistula using the fistula forming element.

[0005] In another embodiment, a system for forming a fistula includes a first catheter configured to be advanced through a first tube, a second catheter configured to be advanced through a second tube, a detector / probe configured to be positioned outside a treatment site, a user output device configured to output a ready signal, and a control unit communicatively coupled to one or more magnetic field sensors and the user output device. The first catheter includes a fistula forming element and one or more first catheter magnetic elements. The second catheter includes one or more second catheter magnetic elements. The one or more first catheter magnetic elements and the one or more second catheter magnetic elements are configured to attract the first catheter and the second catheter together. The detector is configured to be positioned outside the treatment site and includes one or more magnetic field sensors configured to output a magnetic field signal indicating the magnitude of a magnetic field generated between the one or more first catheter magnetic elements and the one or more second catheter magnetic elements. The control unit is configured to receive magnetic field signals from one or more magnetic field sensors, determine a separation distance between the first catheter and the second catheter based on the magnetic field signals from the one or more magnetic field sensors, and output a ready signal using a user output device in response to determining that the separation distance between the first catheter and the second catheter is a predetermined distance or less, wherein the ready signal indicates proper alignment and position of the first catheter and the second catheter to form a fistula using a fistula forming element.

[0006] In yet another embodiment, a method for forming a fistula comprises: advancing a first catheter through a first tube, wherein the first catheter comprises a fistula forming element and one or more first catheter magnetic elements; advancing a second catheter through a second tube, wherein the second catheter comprises one or more second catheter magnetic elements; aligning the one or more first catheter magnetic elements with the one or more second catheter magnetic elements; using one or more magnetic field sensors to detect a magnetic field generated between the one or more first catheter magnetic elements and the one or more second catheter magnetic elements; determining a separation distance between the first catheter and the second catheter based on magnetic field signals from the one or more magnetic field sensors; generating a ready signal using a user output device in response to determining that the separation distance between the first catheter and the second catheter is a predetermined distance or less, wherein the ready signal indicates correct alignment and position of the first catheter and the second catheter; and forming a fistula using the fistula forming element in response to the ready signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The embodiments illustrated in the drawings are illustrative and exemplary in nature and are not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments may be understood when read in conjunction with the following drawings, in which like structures are represented by like reference numerals, and in which:

[0008] Figure 1 Depicted is a system for forming a fistula according to one or more embodiments shown and described herein;

[0009] Figure 2 schematically depicts a system for forming a fistula according to one or more embodiments shown and described herein;

[0010] Figure 3 schematically illustrates magnetic field lines according to one or more embodiments shown and described herein;

[0011] Figure 4 depicts a graph illustrating the relationship between magnetic force and distance, and

[0012] Figure 5 A system for forming a fistula including an external probe according to one or more embodiments shown and described herein is schematically illustrated. DETAILED DESCRIPTION

[0013] Embodiments provided herein relate to systems and methods for forming fistulas. Systems according to the present disclosure generally include a first catheter configured to be advanced through a first tube / first vessel and a second catheter configured to be advanced through a second tube / second vessel. At least one of the first catheter and the second catheter includes a fistula forming element, such as an electrode. In addition, the first catheter and the second catheter include one or more magnetic elements configured to attract the first catheter and the second catheter to each other. By attracting the first catheter and the second catheter together, the tissues of the first and second tubes can be impacted between them, and the operation of the fistula forming element can be used to form an opening (i.e., a fistula) between the first and second tubes. However, ensuring the correct alignment and distance of the first and second catheters relative to each other may be challenging. For example, fluoroscopy can be used to indicate the position of the first and second catheters. However, perspective provides visual feedback in a two-dimensional plane, which may be difficult to ensure correct three-dimensional alignment.

[0014] The present concept involves the use of one or more magnetic field sensors that detect the magnetic field generated between the magnetic elements of the first and second catheters. Based on the detected magnetic field, the control unit can determine the distance and / or alignment of the first and second catheters. When the appropriate distance and alignment have been reached, the control unit can output a signal that reminds the operator that the first and second catheters are correctly positioned to form a fistula. In some embodiments, when the control unit determines that the first and second catheters are not positioned within the appropriate distance from each other or are otherwise not correctly aligned, the control unit can be operated to prevent the operation and / or actuation of the fistula formation element. Various embodiments of the test device and the operation of the test device will be described in more detail herein.

[0015] Any suitable catheter or catheters may be used to form a fistula using the methods and / or systems described herein. The systems and methods described herein may be used in conjunction with U.S. patent applications such as “DEVICES AND METHODS FOR FORMING A FISTULA,” filed on November 16, 2011, and serial number 13 / 298,169, U.S. patent application serial number 14 / 052,477, filed on November 8, 2019, and serial number 14 / 214,503, entitled “FISTULA FORMATION DEVICES AND METHODS THEREFOR,” filed on March 14, 2014, and serial number 14 / 657,997, entitled “Fistula Formation Devises and Methods Therefor,” filed on September 17, 2015, and serial number 14 / 657,997, entitled “Fistula Formation Devises and Methods Therefor,” filed on July 20, 2017, and serial number 14 / 657,997, entitled “Fistula Formation Devises and Methods Therefor,” filed on July 20, 2017, and serial number 14 / 657,997, entitled “Fistula Formation Devises and Methods Therefor,” filed on July 20, 2017, and serial number 14 / 657,997, entitled “Fistula Formation Devises and Methods Therefor,” filed on July 20, 2017, and serial number 14 / 657,997, entitled “Fistula Formation Devises and Methods Therefor,” filed on July 20, 2017, and serial number 14 / 657,997, entitled “Fistula Formation Devises and Methods Therefor,” filed on AFISTULA” and one or more of the devices described in U.S. patent application serial number 15 / 406,755 and U.S. patent application serial number 16 / 024,241, filed on June 29, 2018, entitled “SYSTEMS AND METHODS FOR ADHERING VESSELS”, each of which is incorporated herein by reference in its entirety.

[0016] In some variations, a fistula may be formed using a first catheter placed in a first vessel (eg, an artery) and a second catheter placed in a second vessel (eg, a vein). Figure 1 A variation of a system 100 that can be used to form a fistula between a first tube and a second tube is shown. As shown therein, the system 100 can include a first catheter 110 and a second catheter 112. The first catheter 110 can include a catheter body 114 and a fistula forming element 132. The fistula forming element 132 can be advanced or biased out of an opening 130 in the catheter body 114. For example, the fistula forming element 132 can be positioned adjacent to the end / tip 113 of the first catheter 110 and can extend from the sidewall 115 of the first catheter 110 of the catheter body 114. In other embodiments, the fistula forming element 132 cannot move relative to the catheter body 114.

[0017] The fistula forming element 132 can be any device operable to form an opening between a first tube (e.g., a vein) and a second tube (e.g., an artery). For example, the fistula forming element 132 can be any cutting, puncturing and / or ablating device, such as a knife, a needle and / or an electrode. In the illustrated embodiment, the fistula forming element 132 includes an electrode 134. An electric current can be passed through the electrode 134 to ablate or otherwise remove tissue in contact with the electrode 134. In some variations, the first catheter 110 can have an insulating housing 131 (e.g., a ceramic housing, etc.) within the catheter body 114, which can help protect other components of the first catheter 110 from heat that may be generated by the electrode 134 during tissue removal / ablation. In embodiments, the electrode 134 can be selectively moved from a position where the electrode 134 is retained or otherwise maintained within the catheter body 114 to a position where the electrode 134 extends away from the sidewall 115 of the catheter body 114 (e.g., such as Figure 2 ). After tissue ablation, the electrode 134 can also be selectively moved back to the retracted / low profile position (the same or a different position than the previous retracted position). In some variations, the electrode 134 can be biased toward the extended position when not otherwise constrained by the catheter body 114.

[0018] Although in Figure 1 A fistula forming element 132 including an electrode 134 is shown in the figure, but it should be understood that embodiments may include a catheter having any suitable fistula forming element 132 (e.g., one or more electrodes / electrocautery mechanisms, one or more mechanical cutting mechanisms such as blades, spray guns, needles, etc., one or more chemical devices, cryogenic-cautery devices, laser ablation devices, combinations thereof, etc.), such as those described in more detail in U.S. patent application serial number 13 / 298,169, U.S. patent application serial number 14 / 052,477, U.S. patent application serial number 14 / 214,503, U.S. patent application serial number 14 / 657,997, U.S. patent application serial number 15 / 406,755 and U.S. patent application serial number 16 / 024,241, which have been incorporated by reference herein, and may be operated in any manner as described therein.

[0019] The second catheter 112 can have any suitable element or combination of elements to facilitate the formation of a fistula between it and the first catheter 110. For example, the second catheter 112 can include a catheter body 114 having a recess 136 extending therein. The recess 136 can be coated with an insulating material (not shown) that can act as a stop to receive and contact the electrode 134 (or other fistula forming element 132) of the first catheter 110 without damaging one or more components of the second catheter 112. Additionally or alternatively, the second catheter 112 can include one or more fistula forming elements that can be the same as or different from the fistula forming elements of the first catheter 110.

[0020] Each in first conduit 110 and second conduit 112 comprises one or more alignment elements, and it can help conduit to be positioned in vascular system.One or more alignment elements help to make two conduits (and the relevant blood vessel together with them) closer, thereby can form fistula between relevant blood vessel.Additionally or alternatively, one or more alignment elements can be used for one or more conduits to be positioned in the specific rotation configuration relative to blood vessel and / or other conduits.Additionally or alternatively, one or more alignment elements can be used for one or more conduits to be positioned axially in one or more blood vessels.For example, one or more alignment elements can be configured to form element 132 of fistula relative to first pipe and second pipe positioning conduit, so that fistula formation element 132 actuation causes fistula formation between two pipes.

[0021] One or more alignment elements can include one or more magnetic elements (e.g., magnetic elements 120 and / or 122). Examples of magnet arrangements for use with catheters described herein can be found in U.S. Patent Application Serial No. 13 / 298,169, U.S. Patent Application Serial No. 14 / 052,477, U.S. Patent Application Serial No. 14 / 214,503, U.S. Patent Application Serial No. 14 / 657,997, U.S. Patent Application Serial No. 15 / 406,755, and U.S. Patent Application Serial No. 16 / 024,241, which are incorporated herein by reference. These magnetic alignment elements can be attracted to one or more additional elements (e.g., one or more portions of the second catheter 112, one or more magnets or other components placed outside the body) to help position or align the catheter in the tube. For example, one or more magnets placed outside the body can interact with the magnetic alignment components of the catheter to help facilitate the catheter to move forward through the vascular system. Additionally or alternatively, one or more magnetic elements of the first conduit 110 can interact with one or more magnetic elements of the second conduit 112 to attract the first conduit 110 and the second conduit 112 toward each other and / or bias the first conduit 110 and the second conduit 112 toward a particular rotational alignment and / or axial alignment.

[0022] For example, in Figure 1 In the variation of the system 100 shown, the first catheter 110 may include one or more first catheter magnetic elements 120 and the second catheter 112 may include one or more second catheter magnetic elements 122. These magnetic elements 120, 122 may be configured to bias the axial positioning of the first catheter 110 and the second catheter 112 so that the opening 130 of the first catheter 110 is axially aligned with the recess 136 of the second catheter 112. The magnetic elements 120, 122 may also be configured to bias the rotational positioning of the first catheter 110 and the second catheter 112 so that the opening 130 of the first catheter 110 faces the recess 136 of the second catheter 112. Thus, the one or more magnetic elements 120, 122 may be used to help position the first catheter 110 and the second catheter 112 within the respective vessels (e.g., arteries / veins) so that the electrode 134 may extend from the opening 130 toward the recess 136 of the second catheter 112 during fistula formation.

[0023] The one or more first catheter magnetic elements 120 may include one or more magnets or magnetic arrays located distally and / or proximally of the fistula forming element 132. For example, the one or more first catheter magnetic elements 120 may be positioned proximally and distally of the fistula forming element 132, such that one or more magnets or magnetic arrays are positioned on either side of the fistula forming element 132. Similarly, the one or more second catheter magnetic elements 122 may include one or more magnets or magnetic arrays located distally and / or proximally of the recess 136. For example, the one or more second catheter magnetic elements 122 may be positioned proximally and distally of the recess 136 and correspond to the one or more first catheter magnetic elements 120. The one or more first catheter magnetic elements 120 and the one or more second catheter magnetic elements 122 may include temporary magnets, permanent magnets, and / or electromagnets.

[0024] In some embodiments, the first catheter 110 and / or the second catheter 112 may include one or more markers 117 for visualizing their advancement and positioning. In some variations, the marker 117 can be directly visualized. In other variations, the marker can be indirectly visualized (e.g., via ultrasound, fluoroscopy, and / or X-ray visualization). The marker 117 can be located anywhere within the catheter relative to the catheter, such as on one or more surfaces of the catheter. In some variations, one or more portions of the catheter can be made of echogenic or radiographic materials. The marker can be attached to the catheter by any suitable method, such as by mechanical attachment (e.g., embedded in a portion of the catheter, circumferentially attached, etc.), adhesive bonding, welding, soldering, combinations thereof, etc. For example, in the above Figure 1 In the variation of the system 100 shown, each of the first catheter 110 and the second catheter 112 can include one or more markers 117. These markers 117 can be visualized during the advancement and / or positioning of the first catheter 110 and the second catheter 112 to confirm that the catheters are correctly positioned within the blood vessel. For example, in the variation where the opening 130 of the first catheter 110 is axially aligned with the recess 136 of the second catheter 112 and / or the opening 130 of the first catheter 110 is rotationally aligned relative to the recess 136 of the second catheter 112, the one or more markers 117 can be used to confirm such positioning of the first catheter 110 and the second catheter 112 with the first and second tubes by one or more visualization techniques (e.g., ultrasound, fluoroscopy, and / or X-ray) before fistula formation.

[0025] However, as described above, such visualization techniques may be erroneous. For example, although the first catheter 110 and the second catheter 112 may appear aligned under two-dimensional fluoroscopy, the first catheter 110 and the second catheter 112 may not be aligned in three-dimensional space. As will be described in more detail below, instead of one or more markers 117 and / or in addition to one or more markers 117, the system 100 may include one or more magnetic field sensors 116, which can be used to determine the alignment and / or positioning of the first catheter 110 and the second catheter 112 relative to each other.

[0026] Figure 2 Modules of system 100 are schematically shown, which may be communicatively coupled to each other via communication path 102. System 100 generally includes control unit 104, one or more magnetic field sensors 116, and user output device 140. In yet other embodiments, system 100 may also include power supply 160 and / or security devices such as locking mechanism 150.

[0027] The various electronic components of the system 100 are communicatively coupled to each other via a communication path 102. The communication path 102 may be a bus that connects the various components of the system 100. The communication path 102 may be formed by any medium capable of transmitting a signal, such as a wire, a conductive trace, an optical waveguide, etc. In addition, the communication path 102 may be formed by a combination of media capable of transmitting a signal. In some embodiments, the communication path 102 includes a combination of conductive traces, wires, connectors, and buses that cooperate to allow electrical signals to be transmitted between various components such as processors, memories, sensors, input devices, output devices, and communication devices. In addition, it should be noted that the term "signal" refers to a waveform (e.g., electrical, optical, magnetic, mechanical, or electromagnetic) that can propagate through a medium, such as DC, AC, a sine wave, a triangle wave, a square wave, vibrations, etc.

[0028] The control unit 104 may be any type of computing device and include one or more processors and one or more memory modules. The one or more processors may include any device capable of executing machine-readable instructions stored on a non-transitory computer-readable medium, such as those stored on one or more memory modules. Thus, each of the one or more processors may include a controller, an integrated circuit, a microchip, a computer, and / or any other computing device.

[0029] One or more memory modules of the control unit 104 are communicatively coupled to one or more processors. One or more memory modules may be configured as volatile and / or non-volatile memory, and thus may include random access memory (including SRAM, DRAM, and / or other types of RAM), flash memory, secure digital (SD) memory, registers, compact disks (CDs), digital versatile disks (DVDs), and / or other types of non-transitory computer-readable media. Depending on the particular embodiment, these non-transitory computer-readable media may reside within the control unit 104 and / or outside the control unit 104. The one or more memory modules may be configured to store logic instructions (i.e., machine-readable instructions) that, when executed by the one or more processors, allow the control unit 104 to, for example, determine a separation distance between the first catheter 110 and the second catheter 112 and / or an alignment of the first catheter 110 and the second catheter 112 and output a ready signal (e.g., using the user output device 140) in response to determining that the separation distance between the first catheter 110 and the second catheter 112 is within a predetermined threshold. In some embodiments, the logic instructions executed by the one or more processors may prevent operation of the fistula formation element 132 if the separation distance is determined to be greater than a predetermined threshold (e.g., greater than about 2 mm, greater than about 1.5 mm, greater than about 1 mm, or other predetermined threshold distance) or if the control unit 104 determines that the first catheter 110 and the second catheter 112 are otherwise misaligned.

[0030] As described above, the system 100 includes one or more magnetic field sensors 116. One or more magnetic field sensors 116 provide alignment information of the first conduit 110 and the second conduit 112 relative to each other. The magnetic field sensor 116 may include any device configured to output a magnetic field signal indicating the magnitude of the magnetic field, such as the force of the magnetic field. Such magnetic field sensors 116 may include, but are not limited to, Hall effect sensors, magnetoresistive sensors, micro-electromechanical systems (MEM) magnetic field sensors 116, superconducting quantum interference devices (SQUID) sensors, and the like. Figure 3 Magnetic field lines are schematically shown between the first conduit magnetic element 120 and the second conduit magnetic element 122. As the first conduit magnetic element 120 moves closer to the second conduit magnetic element 122, the magnetic attraction force between the first conduit magnetic element 120 and the second conduit magnetic element 122 increases. Figure 4 The logarithmic relationship between distance 172 on the x-axis and force 171 on the y-axis is graphically shown, as taught by Coulomb's law:

[0031]

[0032] Where F is the attractive force and r is the separation distance between the magnetic elements 120, 122. That is, the attractive force is inversely proportional to the square of the separation distance. The magnetic field signal output by the one or more magnetic field sensors 116 provides a measurement indicating the magnetic attraction between the magnetic elements 120, 122. In operation, the control unit 104 receives the magnetic field signal from the one or more magnetic field sensors 116 and executes logic instructions to determine the separation distance of the first conduit 110 and the second conduit 112 using Coulomb's law above. Once the predetermined separation distance A is reached, the control unit 104 can provide a notification to the operator that the first conduit 110 and the second conduit 112 are correctly positioned.

[0033] In addition, in order to provide increased attraction and alignment, one or more first catheter magnetic elements 120 and one or more second catheter magnetic elements 122 can be arranged to have opposite magnetic poles facing each other. That is, for example, one or more first catheter magnetic elements 120 can be arranged so that the N pole is aligned with the fistula forming element 132 on the catheter body 114 side, and one or more second catheter magnetic elements 120 can be arranged so that the S pole is aligned with the recess 136 for receiving the fistula forming element 132 on the catheter body 114 side, or vice versa. Therefore, in the case where the magnetic poles are not properly aligned for attraction, no magnetic field will be generated or a weaker magnetic field will be generated. Therefore, the magnitude of the magnetic field sensed based on the magnetic field signal can indicate both the distance between the first catheter 110 and the second catheter 112 and the alignment of the first catheter 110 and the second catheter 112.

[0034] During fistula formation, the separation distance between the first conduit 110 and the second conduit 112 should be within a predetermined threshold for forming a fistula. For example, the predetermined threshold can be about 2 mm or less, such as about 1.5 mm or less, 1 mm or less, etc. The predetermined threshold or distance is any distance at which a fistula may be formed using the fistula forming element 132, or any distance at which a fistula may be formed using the fistula forming element 132. For example, the predetermined distance can allow the fistula forming element 132 to fully extend through the wall of the first tube and through the wall of the second tube to contact the recess 136 of the second conduit 112, thereby forming an opening between the first tube and the second tube. Therefore, as will be explained in more detail below, when the control unit 104 determines that the separation distance between the first conduit 110 and the second conduit 112 is 1 mm or less between the portion of the first conduit 110 including the fistula forming element 132 and the portion of the second conduit 110 including the recess 136, then the control unit 104 determines that an appropriate distance and alignment have been achieved between the first conduit 110 and the second conduit 112.

[0035] One or more magnetic field sensors 116 may be mounted to and / or installed within the catheter body 114 of the first catheter 110, the second catheter 112, or both, such as Figure 1 In some embodiments, one or more magnetic field sensors 116 may alternatively be mounted on an external detector 118, such as Figure 5 As shown.

[0036] exist Figure 1 In the illustrated embodiment, one or more magnetic field sensors 116 can be integrated into the first catheter 110 and / or the second catheter 112. That is, one or more magnetic field sensors 116 are advanced through one or more tubes together with the first catheter 110 and / or the second catheter 112. One or more magnetic field sensors 116 can be positioned proximal and / or distal to one or more magnetic elements 120, 122 of the first catheter 110 and / or the second catheter 112. For example, the magnetic field sensor 116 can be mounted on the first catheter 110 at the distal side (e.g., closer to the tip 113) of one or more first catheter magnetic elements 120 and / or fistula forming elements 132. In some embodiments, the magnetic field sensor 116 can be located proximal to one or more first catheter magnetic elements 120 and fistula forming elements 132. In some embodiments, on either side of the fistula forming element 132, the first magnetic field sensor can be associated with the first magnetic element of the first catheter 110, and the second magnetic field sensor can be associated with the second magnetic element of the first catheter 110.

[0037] In some embodiments, the magnetic field sensor 116 can be integrated into only one of the first catheter 110 and the second catheter 112. For example, the second catheter 112 can include a magnetic field sensor 116 mounted on the catheter body 114 of the second catheter 112 at the distal and / or proximal side of one or more magnetic elements 120 and recess 136 of the second catheter 112. In some embodiments, each of the first catheter 110 and the second catheter 112 includes one or more magnetic field sensors 116. It should be noted that additional magnetic field sensors can provide greater sensitivity for alignment and separation distance. The position of one or more magnetic field sensors 116 can be close to one or more first catheter magnetic elements 120 and / or one or more second catheter magnetic elements 122 (e.g., about 10 mm or less from one or more magnetic elements).

[0038] As mentioned above, and with reference to Figure 5In addition to and / or in lieu of any magnetic field sensors 116 mounted to the catheter, one or more magnetic field sensors 116 may be mounted to an external probe 118. The external probe 118 may be a handheld probe or may be mounted to a robotic arm or other fixture configured to hold the probe close to the treatment portion of the patient. For example, Figure 5 A patient's arm 200 is shown with a first catheter 110 positioned within a first tube 202 (e.g., a vein) and a second catheter 112 positioned within a second tube 204 (e.g., an artery). The first catheter 110 and the second catheter 112 are similar to those described above with respect to Figure 1 The first catheter 110 and the second catheter 112 are substantially similar to those described above. The first catheter 110 and the second catheter 112 are advanced through the first and second tubes to the treatment site (e.g., where the fistula is to be formed). When the first catheter 110 and the second catheter 112 are positioned at or approximately positioned at the treatment site, the external detector 118 can be advanced toward the treatment site to detect the magnetic field strength between one or more first catheter magnetic elements 120 of the first catheter 110 and one or more second catheter magnetic elements 120 of the second catheter 112. For example, the external detector 118 can be advanced so as to be within the sensing range of one or more magnetic field sensors 116 of the external detector 118 (e.g., within about 0.5 meters, within about 0.4 meters, about 0.3 meters, etc.). When the first catheter magnetic element 120 and the second catheter magnetic element 122 begin to attract each other, one or more magnetic field sensors 116, whether internal or external, can automatically begin to detect the magnetic attraction between the first catheter 110 and the second catheter 112.

[0039] In some embodiments, one or more magnetic elements 120 of the first conduit 110 and the second conduit 112 may include an electromagnet. In such embodiments, an external magnetic field generator not shown may be used to excite the electromagnet. In addition, the electromagnets of the first conduit 110 and the second conduit 112 may be communicatively coupled to the control unit 104 and output electrical signals indicating their positions in the three-dimensional space within the magnetic field generated by the magnetic field generator to the control unit. For example, each electrical signal may indicate the position of the electromagnet relative to the magnetic field generator. Based on this information, the control unit 104 may execute logic instructions to determine the positions of the first conduit 110 and the second conduit 112 relative to each other. Therefore, one or more magnetic elements 120 of the first conduit 110 and the second conduit 112 may act as a position sensor or a magnetic field sensor 116.

[0040] Refer again Figure 2, the system 100 also includes a user output device 140 that is communicatively coupled to the control unit 104 via the communication path 102. The user output device 140 may include any visual, tactile or auditory feedback device that is configured to output a ready signal when the control unit 104 determines that the first catheter 110 and the second catheter 112 are within a suitable distance for forming a fistula and / or have a suitable alignment based on a magnetic field signal from one or more magnetic field sensors 116. For example, the user output device 140 may include a light indicator (e.g., a fluorescent light, an LED light, etc.) mounted on an external detector 118 or a handle of the first catheter 110 and / or the second catheter 112. In response to detecting that the first catheter 110 and the second catheter 112 are correctly positioned relative to each other, the control unit 104 may turn on the light indicator. In some embodiments, when it is determined that the first catheter 110 and the second catheter 112 are correctly positioned, the light indicator may be a green light. In some embodiments, when it is determined that the first catheter 110 and the second catheter 112 are not correctly aligned, the light indicator or a separate indicator light may be a red light. In some embodiments, an audible sound may be emitted from the speaker in response to achievement of proper alignment.

[0041] In some embodiments, the system 100 may include a locking mechanism 150 that prevents actuation of the fistula forming element 132 when it is determined that the first catheter 110 and the second catheter 112 are not properly aligned (e.g., not within a predetermined separation range). For example, the locking mechanism 150 may be communicatively coupled to the control unit 104 via the communication path 102 so as to be operable by the control unit 104. For example, the locking mechanism 150 may be a switch that electrically couples the fistula forming element 132 with the power source 160. The locking mechanism 150 may be positioned to prevent energy from flowing from the power source 160 to the fistula forming element 132 (e.g., the electrode 134) in response to determining that the first catheter 110 and the second catheter 112 are not properly aligned. In some embodiments, the locking mechanism 150 may be positioned to prevent energy from flowing from the power source 160 to the fistula forming element 132 until the control unit 104 determines that the first catheter 110 and the second catheter 112 are properly aligned. Other contemplated locking mechanisms may include, but are not limited to, magnetic locking mechanisms, relays, solenoids, interlocking actuators, and the like.

[0042] In some embodiments, the power source 160 can be communicatively coupled to the control unit 104 such that the control unit 104 can selectively operate the power source 160 (e.g., a battery, an RF generator, an outlet, etc.). In such embodiments, the control unit 104 can be configured to prevent operation of the power source 160 to power the fistula forming element 132 when it is determined that the first catheter 110 and the second catheter 112 are not properly aligned.

[0043] A method of forming a fistula between the first tube 202 and the second tube 204 will now be described. Figure 5 , the method includes advancing the first catheter 110 through the first tube 202 to the treatment site and advancing the second catheter 112 through the second tube 204 to the treatment site. As the one or more magnetic elements 120 of the first catheter 110 and the second catheter 112 approach each other so as to be aligned with each other, one or more magnetic field sensors 116 (e.g., internal or external magnetic field sensors 116) can automatically begin to detect the magnetic field generated between the one or more first catheter magnetic elements 120 of the first catheter 110 and the one or more second catheter magnetic elements 122 of the second catheter 112. The control unit 104 can receive signals from the one or more magnetic field sensors 116 and execute logic instructions to determine the separation distance of the first catheter 110 and the second catheter 112 (e.g., the axial offset distance D of the one or more magnetic elements 120 of the first catheter 110 and the one or more magnetic elements 122 of the second catheter 112). Once it is determined that the separation distance of the first catheter 110 and the second catheter 112 is within a predetermined range (e.g., 1 mm or less) and / or that the correct rotational alignment is achieved, the control unit 104 can generate a ready signal using the user output device 140. At this point, the operator of the system 100 can use the fistula formation element 132 to form a fistula between the first tube and the second tube. For example, the operator can advance the electrode 134 or cause energy to flow through the electrode 134 to ablate tissue of the first tube 202 and the second tube 204 that are impacted between the first catheter 110 and the second catheter 112. As described above, in the event that it is determined that the proper alignment and distance are not achieved, the control unit 104 can operate the locking mechanism 150 or the power supply 160 to prevent fistula formation until proper alignment is achieved.

[0044] In some embodiments, additional visual confirmation means using fluoroscopy, ultrasound, etc. may be used.

[0045] Embodiments may be described with reference to the following numbered clauses, with preferred features listed in the dependent clauses.

[0046] 1. A system for forming a fistula, comprising: a first catheter configured to be advanced through a first tube, the first catheter comprising a fistula forming element and one or more first catheter magnetic elements; a second catheter configured to be advanced through a second tube, the second catheter comprising one or more second catheter magnetic elements, wherein the one or more first catheter magnetic elements and the one or more second catheter magnetic elements are configured to attract the first catheter and the second catheter together; and one or more magnetic field sensors configured to output a magnetic field signal indicating the magnitude of a magnetic field generated between the one or more first catheter magnetic elements and the one or more second catheter magnetic elements. signal; a user output device configured to output a ready signal; and a controller communicatively coupled to the one or more magnetic field sensors and the user output device, wherein the controller is configured to: receive a magnetic field signal from the one or more magnetic field sensors; determine a separation distance between the first catheter and the second catheter based on the magnetic field signals from the one or more magnetic field sensors; and output a ready signal using the user output device in response to determining that the separation distance between the first catheter and the second catheter is a predetermined distance or less, wherein the ready signal indicates that the first catheter and the second catheter are properly aligned and positioned for forming a fistula using the fistula forming element.

[0047] 2. The system of clause 1, wherein the fistula forming element is positioned near the tip of the first catheter and is extendable from a side wall of the first catheter.

[0048] 3. A system according to any preceding clause, wherein the one or more magnetic field sensors are coupled to at least one of the first conduit and the second conduit.

[0049] 4. A system according to any preceding clause, wherein the one or more magnetic field sensors include a first magnetic field sensor coupled to the first conduit and a second magnetic field sensor coupled to the second conduit.

[0050] 5. A system according to any preceding clause, wherein the user output device comprises an indicator light.

[0051] 6. The system according to any preceding clause, wherein the controller is further configured to prevent operation of the fistula formation element upon determining that the separation distance between the first catheter and the second catheter is greater than the predetermined distance.

[0052] 7. A system according to claim 6, wherein the fistula forming element includes an electrode, which is connected to a power source to energize the electrode, wherein the controller is communicatively connected to the power source, and the controller is configured to operate the power source to prevent the electrode from being energized when it is determined that the separation distance between the first catheter and the second catheter is greater than the predetermined distance.

[0053] 8. A system according to any preceding clause, wherein the one or more magnetic field sensors include at least one of a Hall effect sensor, a magnetoresistive sensor, a micro-electromechanical system sensor and / or a superconducting quantum interference device sensor.

[0054] 9. A system for forming a fistula, comprising: a first catheter configured to be advanced through a first tube, the first catheter comprising a fistula forming element and one or more first catheter magnetic elements; a second catheter configured to be advanced through a second tube, the second catheter comprising one or more second catheter magnetic elements, wherein the one or more first catheter magnetic elements and the one or more second catheter magnetic elements are configured to attract the first catheter and the second catheter together; a detector configured to be positioned outside a treatment site, the detector comprising one or more magnetic field sensors configured to output an indication of a magnetic field between the one or more first catheter magnetic elements and the one or more second catheter magnetic elements a magnetic field signal indicating the magnitude of the magnetic field generated between the first and second catheters; a user output device configured to output a ready signal; and a controller communicatively connected to the one or more magnetic field sensors and the user output device, wherein the controller is configured to: receive the magnetic field signal from the one or more magnetic field sensors; determine the separation distance between the first catheter and the second catheter based on the magnetic field signal from the one or more magnetic field sensors; and output a ready signal using the user output device in response to determining that the separation distance between the first catheter and the second catheter is a predetermined distance or less, wherein the ready signal indicates that the first catheter and the second catheter are correctly aligned and positioned for forming a fistula using the fistula forming element.

[0055] 10. The system of clause 9, wherein the fistula forming element is positioned proximate to the tip of the first catheter and is extendable from a sidewall of the first catheter.

[0056] 11. The system of clause 9 or 10, wherein the user output device comprises an indicator light coupled to the detector.

[0057] 12. The system of any of clauses 9-11, wherein the controller is further configured to prevent operation of the fistula forming element upon determining that the separation distance between the first catheter and the second catheter is greater than a predetermined distance.

[0058] 13. A system according to claim 12, wherein the fistula forming element includes an electrode, which is connected to a power source to energize the electrode, wherein the controller is communicatively connected to the power source, and wherein the controller is configured to operate the power source to prevent the electrode from being energized when it is determined that the separation distance between the first catheter and the second catheter is greater than a predetermined distance.

[0059] 14. The system of any of clauses 9-12, wherein the one or more magnetic field sensors comprise at least one of a Hall effect sensor, a magnetoresistive sensor, a microelectromechanical system sensor, and a superconducting quantum interference device sensor.

[0060] 15. A method for forming a fistula, comprising: advancing a first catheter through a first tube, wherein the first catheter includes a fistula forming element and one or more first catheter magnetic elements; advancing a second catheter through a second tube, wherein the second catheter includes one or more second catheter magnetic elements; aligning the one or more first catheter magnetic elements with the one or more second catheter magnetic elements; using one or more magnetic field sensors to detect a magnetic field generated between the one or more first catheter magnetic elements and the one or more second catheter magnetic elements; determining a separation distance between the first catheter and the second catheter based on magnetic field signals from the one or more magnetic field sensors; generating a ready signal using a user output device in response to determining that the separation distance between the first catheter and the second catheter is approximately a predetermined distance or less, wherein the ready signal indicates proper alignment and position of the first catheter and the second catheter; and forming a fistula using the fistula forming element in response to the ready signal.

[0061] 16. The method of clause 15, further comprising preventing operation of the fistula forming element upon determining that a separation distance between the first conduit and the second conduit is greater than a predetermined distance.

[0062] 17. The method of clause 16, wherein the fistula forming element comprises an electrode coupled to a power source, and operation of the power source is prevented upon determining that the separation distance between the first conduit and the second conduit is greater than a predetermined distance.

[0063] 18. The method of any of clauses 15-17, wherein the one or more magnetic field sensors are coupled to at least one of the first conduit and the second conduit.

[0064] 19. The method of any of clauses 15-18, wherein the one or more magnetic field sensors include a first magnetic field sensor coupled to the first conduit and a second magnetic field sensor coupled to the second conduit.

[0065] 20. The method of any of clauses 15-19, wherein the one or more magnetic field sensors are coupled to a detector positioned external to the treatment site.

[0066] It should be understood now that the embodiments described herein relate to the use of one or more magnetic field sensors that detect the magnetic field generated between the magnetic elements of the first and second catheters. Based on the detected magnetic field, the control unit can determine the distance and / or alignment of the first and second catheters. When the appropriate distance and alignment have been reached, the control unit can output a signal that reminds the operator that the first and second catheters are correctly positioned for forming fistulas. In certain embodiments, when the control unit determines that the first catheter and the second catheter are not positioned at an appropriate distance from each other or are otherwise incorrectly aligned, the control unit is operable to prevent the actuation of the fistula-forming element. Such systems provide a variety of clinical benefits, including less use or no use of fluoroscopy, because magnetic induction can provide confirmation of both separation distance and rotational alignment. The system can also minimize the subjectivity of the operator when reading fluoroscopic images or other two-dimensional images.

[0067] It is noted that the terms "substantially" and "approximately" may be used herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

[0068] Although specific embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. In addition, although various aspects of the claimed subject matter have been described herein, these aspects need not be used in combination. Therefore, the appended claims are intended to cover all such changes and modifications within the scope of the claimed subject matter.

Claims

1. A system for forming a fistula, comprising: a first catheter configured to be advanced through the first tube, the first catheter comprising a fistula forming element and one or more first catheter magnetic elements; a second catheter configured to be advanced through a second tube, the second catheter comprising one or more second catheter magnetic elements, wherein the one or more first catheter magnetic elements and the one or more second catheter magnetic elements are configured to attract the first catheter and the second catheter together; one or more magnetic field sensors configured to output a magnetic field signal indicative of a magnitude of a magnetic field generated between the one or more first conduit magnetic elements and the one or more second conduit magnetic elements; a user output device configured to output a ready signal; and a controller communicatively coupled to the one or more magnetic field sensors and the user output device, wherein the controller is configured to: receiving a magnetic field signal from the one or more magnetic field sensors; determining a separation distance of the first conduit and the second conduit based on magnetic field signals from the one or more magnetic field sensors; as well as Outputting a ready signal using the user output device in response to determining that the first catheter is separated from the second catheter by a predetermined distance or less, wherein the ready signal indicates proper alignment and position of the first catheter and the second catheter for forming a fistula using the fistula forming element.

2. The system according to claim 1, wherein: The fistula forming element is positioned near the tip of the first catheter and is extendable from a side wall of the first catheter.

3. The system according to claim 1, wherein: The one or more magnetic field sensors are coupled to at least one of the first conduit and the second conduit.

4. The system according to claim 1, wherein: The one or more magnetic field sensors include a first magnetic field sensor coupled to the first conduit and a second magnetic field sensor coupled to the second conduit.

5. The system according to claim 1, wherein: The user output device includes an indicator light.

6. The system according to claim 1, wherein: The controller is further configured to prevent operation of the fistula forming element upon determining that the separation distance between the first conduit and the second conduit is greater than the predetermined distance.

7. The system according to claim 6, wherein: The fistula forming element includes an electrode coupled to a power source to energize the electrode, wherein the controller is communicatively coupled to the power source and is configured to operate the power source to prevent energization of the electrode upon determining that the separation distance between the first catheter and the second catheter is greater than the predetermined distance.

8. The system according to claim 1, wherein: The one or more magnetic field sensors include at least one of a Hall effect sensor, a magnetoresistive sensor, a micro-electromechanical system sensor, and / or a superconducting quantum interference device sensor.

9. A system for forming a fistula, comprising: a first catheter configured to be advanced through the first tube, the first catheter comprising a fistula forming element and one or more first catheter magnetic elements; a second catheter configured to be advanced through a second tube, the second catheter comprising one or more second catheter magnetic elements, wherein the one or more first catheter magnetic elements and the one or more second catheter magnetic elements are configured to attract the first catheter and the second catheter together; a detector configured to be positioned external to a treatment site, the detector comprising one or more magnetic field sensors configured to output a magnetic field signal indicative of a magnitude of a magnetic field generated between the one or more first catheter magnetic elements and the one or more second catheter magnetic elements; a user output device configured to output a ready signal; and a controller communicatively coupled to the one or more magnetic field sensors and the user output device, wherein the controller is configured to: receiving a magnetic field signal from the one or more magnetic field sensors; determining a separation distance of the first conduit and the second conduit based on magnetic field signals from the one or more magnetic field sensors; as well as Outputting a ready signal using the user output device in response to determining that the first catheter is separated from the second catheter by a predetermined distance or less, wherein the ready signal indicates proper alignment and position of the first catheter and the second catheter for forming a fistula using the fistula forming element.

10. The system according to claim 9, wherein: The fistula forming element is positioned near the tip of the first catheter and is extendable from a side wall of the first catheter.

11. The system according to claim 9, wherein: The user output device includes an indicator light coupled to the detector.

12. The system according to claim 9, wherein: The controller is further configured to prevent operation of the fistula forming element upon determining that the separation distance between the first conduit and the second conduit is greater than the predetermined distance.

13. The system according to claim 12, wherein: The fistula forming element includes an electrode coupled to a power source to energize the electrode, wherein the controller is communicatively coupled to the power source, wherein the controller is configured to operate the power source to prevent energization of the electrode upon determining that a separation distance between the first catheter and the second catheter is greater than the predetermined distance.

14. The system according to claim 9, wherein: The one or more magnetic field sensors include at least one of a Hall effect sensor, a magnetoresistive sensor, a micro-electromechanical system sensor, and a superconducting quantum interference device sensor.

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