Abstract
A method of creating an arteriovenous (AV) fistula between first and second vessels includes inserting a catheter comprising a proximal member and a distal member into the first vessel so that the distal member comes into contact with a selected anastomosis site. Creating an aperture between the first and second vessels advancing the distal member into the second vessel. Clamping the first and second vessels together using the proximal and distal members. Applying energy to a heating member on one of the proximal and distal members to further cut the first and second vessels and shape the aperture. The step of applying energy to the heating member further cauterizes and welds an edge of the aperture in order to create the desired fistula between the first and second vessels.
Claims
1. A method of creating an arteriovenous (AV) fistula between first and second vessels comprising: inserting a catheter comprising a proximal member and a distal member into the first vessel so that the distal member comes into contact with a selected anastomosis site; creating an aperture between the first and second vessels; advancing the distal member into the second vessel; clamping the first and second vessels together using the proximal and distal members; and applying energy to a heating member on one of the proximal and distal members to further cut the first and second vessels and shape the aperture, the step of applying energy to the heating member further cauterizing and welding an edge of the aperture in order to create the desired fistula between the first and second vessels.
2. The method as set forth in claim 1, further comprising dispersing heat away from the heating member using a heat spreader.
3. The method as set forth in claim 2, wherein the heat spreader comprises a conductive material disposed on one of the proximal and distal members.
4. The method as set forth in claim 3, wherein the conductive material is disposed below the heating member.
5. The method set forth in claim 2, further comprising creating a heat gradient across a face of one of the proximal and distal members to weld the first and second vessels together.
6. The method as set forth in claim 1, wherein applying energy to the heating member elongates the aperture.
7. The method as set forth in claim 1, wherein applying energy to the heating member causes the proximal member to move closer to the distal member.
8. The method as set forth in claim 1, wherein applying energy to the heating member comprises applying RF energy.
9. The method as set forth in claim 1, wherein advancing the distal member comprises moving the distal member distally relative to the proximal member so that the distal member is spaced a greater distance from the proximal member after the advancing step is performed than it is before the advancing step is performed.
10. The method as set forth in claim 9, further comprising retracting the distal member toward the proximal member to clamp the first and second vessels together.
11. The method as set forth in claim 10, wherein advancing the distal member is performed by advancing a tubular structure distally from an outer tube comprising the proximal member, and retracting the distal member is performed by withdrawing the tubular structure proximally into the outer tube.
12. The method as set forth in claim 10, wherein the catheter comprises first and second heating members, the first heating member being disposed on the proximal member and the second heating member being disposed on the distal member, wherein the first and second heating members are prevented from coming into contact with each other when the distal member is fully retracted.
13. The method as set forth in claim 9, wherein the catheter is rotated during the advancing step.
14. The method as set forth in claim 1, further comprising applying tension to the heating member to seat the heating member against one of the first and second vessels.
15. The method as set forth in claim 1, further comprising capturing tissue cut from the first and second vessels.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is an isometric view of an embodiment of a catheter device constructed in accordance with the principles of the present invention;
[0033] FIGS. 2-8 are schematic sequential views illustrating a method for creating a fistula performed in accordance with the principles of the present invention, and using an apparatus like that illustrated in FIG. 1 and disclosed herein;
[0034] FIG. 9 is a schematic view illustrating an elongate aperture formed between two adjacent vessels to create the fistula, particularly highlighting the welded edges of the aperture;
[0035] FIG. 10 is a cross-sectional view of a handle portion of the embodiment shown in FIG. 1;
[0036] FIG. 11 is an isometric view similar to FIG. 1, illustrating an alternative embodiment of the invention;
[0037] FIG. 12 is an isometric view of yet another alternative embodiment of the present invention;
[0038] FIG. 13 is an isometric view of still another alternative embodiment of the present invention, wherein a distal toggle member forming part of the device is extended;
[0039] FIG. 14 is an isometric view similar to FIG. 13, wherein the distal toggle member is retracted;
[0040] FIG. 15 is an isometric view of yet another alternative embodiment of the present invention; and
[0041] FIGS. 16-18 are schematic sequential views illustrating a method for creating a fistula using the apparatus of FIG. 15.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0042] Referring now particularly to the drawings, there is shown in FIG. 1 a bi-polar tapered tip catheter embodiment 10, which comprises an elongate outer tube 12 having an outer diameter that can range from 3 F-12 F. It may be manufactured from a variety of materials, either polymer or metallic. It comprises a central lumen 14, within which a tubular structure 16 for attaching a tip 18 may slide. There are separate lumina that run down the elongated core of the outer tube 12 for wiring to power electrodes or heating elements 20, 22 (proximal and distal, respectively), disposed on aligned tapered faces of the respective elongate outer tube 12 and distal tip 18, and to also measure the temperature during the coaptation and cutting processes. In this configuration, the catheter is powered using bipolar energy to the distal RF electrode 22 and the proximal RF electrode 20. The system can also be used in a monopolar configuration by grounding the patient and applying energy to one or both of the RF electrodes to increase the length of the coaptation. The RF electrodes cut at matching angles to increase the surface area of the coaptation and fistula size relative to the catheter diameter. These angles can be adjusted to achieve the desired fistula sizing. The RF electrodes are only electrically conductive on the front faces to maximize energy density. The electrodes are oval-shaped, and are adapted to cut an anastomosis which is larger than the diameter of the shaft 16.
[0043] The apparatus shown and described above in connection with FIG. 1 will now be further described in conjunction with an explanation of a particular method by which the system 10 may be used to create an AV fistula. This method is illustrated more particularly in FIGS. 2-9.
[0044] To begin the inventive method of creating an AV fistula, the practitioner selects an appropriate procedural site having each of a first vessel 26 and a second vessel 28 in close proximity to one another. In currently preferred approaches, the first vessel 26 comprises a vein, and the second vessel 28 comprises an artery, but the is not necessarily limited to this arrangement. As illustrated in FIG. 2, one presently preferred location is the hand 30 of a patient. Then, generally employing principles of the Seldinger technique, as shown in FIG. 2, the first vessel 26 is punctured by a needle 32, which is inserted therein, for the purpose of introducing an access sheath into the site. Then, using suitable techniques, such as the technique described in Provisional U.S. Application Ser. No. 61/354,903, filed on Jun. 15, 2010 and herein expressly incorporated by reference, in its entirety, a guidewire 34 is inserted into the patient, from the first vessel 26 into the second vessel 28, as shown in FIG. 3.
[0045] The guidewire 34 creates an access path for the catheter 10. The catheter 10 is inserted into the patient by loading a proximal end of the guidewire 34 into the tip 18, which is fabricated to be flexible and tapered. The catheter 10 is advanced further into the patient, tracking over the guidewire 34, until the tapered dilating distal tip 18 comes into contact with the selected anastomosis site. The device 10 can be tracked over the guidewire with the distal tip extended (as shown in FIG. 5) or retracted (as shown in FIG. 4). The distal tip 18 is extended and further advanced into the second vessel 28 (FIG. 5) by advancing the central tubular structure 16 distally from the outer tube 12, thereby dilating the fistula, so that the distal tip 18 is in the second vessel 28, and the tube 12 is in the first vessel 26, with its distal tapered surface contacting the inner wall of the first vessel 26. If resistance is felt, the entire system can be rotated to reduce the friction. At this juncture, the opening formed in the wall of the second vessel 28 has recovered back to a small diameter, and fits tightly around the shaft 16, as shown.
[0046] After the distal tip 18 is advanced into the second vessel 28, as illustrated in FIG. 6, a slight tension is applied to the distal RF electrode 22 to seat it against the vessel wall. The blunt shape of the proximal end of the distal tip 18 prevents the distal tip from pulling back through the vessel wall. The proximal end of the device 10, namely the outer tube 12, is then advanced to close the spacing between the tube and tip 18, until the walls of the first and second vessels 26, 28, respectively, are captured between the facing blunt surfaces of each of the outer tube 12 and distal tip 18.
[0047] A controlled tension is maintained between the distal tip 18 and proximal outer tube 12, and at this juncture, with the vessel walls securely clamped, energy is applied to the RF electrodes 20, 22 (FIG. 7). As the electrodes weld and cut the vessels, the electrodes will move closer to one another. When fully retracted, the system 10 is designed so that the two electrodes 20, 22 cannot come into direct contact with one another, thus preventing the electrodes from shorting. A variety of RF energy profiles may be applied to achieve the desired coaptation and cutting. For example, during the coaptation phase, a tapered sine wave may be applied to maximize coagulation without cutting through the tissue. The energy may also be adjusted based upon the impedance of the tissue. Different pulse widths or duty cycles may be used to minimize the heat transferring into adjacent tissues. The hot wire is an oval shape and cuts an anastomosis larger than the diameter of the shaft 16. Within the oval shape of the cutting elements, there is a cavity for capturing the tissue that has been cut. The outer sliding tube is usable to push the tissue off the heater in case there is a sticking problem due to the heat.
[0048] Regarding the tissue welding process, more particularly, the RF energy functions to burn and fuse or weld the vessels together, creating an elongate aperture 36 (FIG. 8) through the opposing walls of each of the first and second vessels, as well as any intervening tissue. As formed, the elongate aperture 36 will typically resemble a slit. However, as pressurized flow 38 begins to occur through the slit or aperture 36, which creates a communicating passage between the first vessel and the second vessel, the aperture widens responsive to the pressure, taking the shape of an ellipse as it opens to form the desired fistula. This effect is illustrated in FIG. 9. The edges 40 of the aperture are cauterized and welded. FIG. 9 illustrates the weld from the venous (first vessel) side. As shown, the cut area corresponds to the shape of the wire. It can be of multiple shapes, such as round, oval, a slit, or a combination as shown. The area outside of the cut has been welded due to the flat face of the catheter in the vein (first vessel) being larger than the cutting wire. The heat from the wire is also preferably spread over this area by a conductive material that is below the heater, as will be described below. This creates a temperature gradient, which is a particularly advantageous feature of the present invention.
[0049] Tissue welding of the type intended to occur in the practice of these inventive methods is discussed in U.S. Pat. No. 6,908,463, to Treat et al., which is herein expressly incorporated by reference, in its entirety.
[0050] FIG. 10 is a cross-sectional view of a handle portion 42 of the embodiment shown in FIG. 1. This is one possible approach for actuating the extension and retraction of the distal tip 18 relative to the elongate outer tube 12, as discussed above, though many other suitable configurations may be used alternatively. A trigger 44 is slideably disposed on the handle 42, slidable distally through a slot 46 in the direction of arrow 48, and then retractable in the reverse direction. A spring 50 within the handle controls pressure, and a locking mechanism functions to lock the trigger 44 in the retracted state.
[0051] Alternative cutting approaches, such as resistive heat (hot wire), ultrasonic, laser, or mechanical approaches, may be used instead of RF energy, if desired. For example, FIG. 11 illustrates an alternative embodiment, wherein a catheter 110 comprises an elongate outer tube 112 having a central lumen 114, a tubular structure 116, and a flexible and tapered distal tip 118. In this embodiment, a single resistive heating wire 152 is used to provide the tissue heating, cutting, and welding function described above. Additionally, an RF configuration applying only monopolar energy, to either the venous or arterial sides, may be employed. A combination of RF energy and resistance heating may also be used. The tip 118, in this embodiment, tracks over the guidewire and dilates the anastomosis site, as in the previousembodiment. The tapered faces of the members 112 and 118 align. The single hot wire 152 down the face cuts a slit in the vessel walls, and the faces are tapered to assist in removing the device.
[0052] Now with reference to FIG. 12, a heat spread catheter 210 is illustrated. The catheter 210 comprises a resistive heating element 252, which is employed in a manner similar to that described above in connection with the FIG. 11 embodiment. However, in this embodiment, a conductive material 254 is disposed beneath the heating element 252. In one configuration, this conductive material 254 comprises aluminum, though other conductive bio-compatible materials may also be used. In operation, this conductive material 254 functions to create a heat gradient from the heating element 252, for the purpose of improving the welding function, as described above.
[0053] In this embodiment, similar to the foregoing embodiments, the tip 218 tracks over the guidewire and dilates the anastomosis site. The tapered faces of each of the members 212 and 218 align, for clamping the vessel walls. The hot wire 252 is an oval shape and has vertical strips 256 on both sides of the artery. The hot wire cuts an anastomosis larger than the diameter of the shaft 216. Under the hot wire 252, the heat conductive material 254 pulls heat away from the hot wire so that there is a temperature gradient across the face, with the temperature being hottest in the center and cooling as the distance outwardly from the center increases.
[0054] The hot wire 252 (heater) is raised above the spreader 254 to increase pressure on the tissue, to thereby assist in the cutting process. Inside the hot wire, there is a cavity to capture the tissue that has been cut. The profile of the distal tip 218 aligns with the edge of the heater when retracted. It is a lower profile than the heat spreader, so that it can be retracted back through the fistula. This also increases the pressure directly on the heater surface to assist in cutting function.
[0055] FIGS. 13 and 14 illustrate still another embodiment 310, comprising a distal toggle member 358. The cutting elements in this embodiment are substantially identical to those shown and described in connection with FIG. 12. As in prior, the toggle 358 tracks over the guidewire into the artery. When retracted (FIG. 15), the toggle captures the artery and pulls against the vein. The hot wire is an oval shape, has vertical strips 356 on both sides of the artery, and cuts an anastomosis larger than the diameter of the shaft 316. Under the hot wire 352, there is a heat conductive material 356 that pulls heat away from the hot wire so that there is a temperature gradient across the face. The hot wire is raised above the heat spreader to increase pressure on the tissue to help it cut through. Inside the hot wire there is a cavity to capture the tissue that has been cut.
[0056] The profile of the toggle 358 aligns with the edge of the heater when retracted. It is of a lower profile than the heat spreader so that it can be retracted back through the fistula. This also increases the pressure directly on the heater surface and helps it cut. Heating elements may also be disposed on the toggle surface to work in conjunction with the heater 352 to cut and weld tissue.
[0057] Pivotable toggles and their functionality are discussed in Provisional U.S. Application Ser. No. 61/354,903, filed on Jun. 15, 2010 and already herein expressly incorporated by reference. Those teachings generally apply to this toggle embodiment, regarding the particulars as to how the toggle is used to enter and then retract the second vessel toward the first vessel.
[0058] In FIGS. 15-18, there is shown a different cutting approach. In this embodiment, the cutting device 410 comprises a shaft 460 having a distal portion 462. The distal portion comprises a side port 464, from which extends a heater wire 466 which is supported by a flexible clamp 468, preferably fabricated from nitinol or similar material. The heater wire may be resistive or utilize any other energy source as described above.
[0059] As shown in FIGS. 16-18, access to the anastomosis site is gained by methods as described above and the function of this device, once in place, is to manipulate the wire 466, using the flexible clamp 468 and suitable actuation mechanisms in order to create a fistula of a desired configuration. Specifically, as shown in FIG. 16, the tip tracks over the guidewire 34 and dilates the anastomosis site, as in previously described approaches. The catheter 410 is advanced so that the clip 466 is all the way in the artery 28, and then pulled back to capture the arterial wall under the clip, as illustrated in FIG. 17. The wire is then activated to heat, and then drawn back, which cuts through the arterial and venous walls. The hot wire is then pulled back (FIG. 18), and pulls down the clip portion through the vessel walls.
[0060] Accordingly, although an exemplary embodiment and method according to the invention have been shown and described, it is to be understood that all the terms used herein are descriptive rather than limiting, and that many changes, modifications, and substitutions may be made by one having ordinary skill in the art without departing from the spirit and scope of the invention.
