Device and method for modifying the shape of a body organ

[0001] The present application is a continuation-in-part of U.S. application Ser. No. 10/331,343 filed Dec. 26, 2002, now U.S. Pat. No. 6,793,673; U.S. application Ser. No. 10/142,637 filed May 8, 2002, now U.S. Pat. No. 6,824,562 and U.S. application Ser. No. 10/066,426 filed Jan. 30, 2002, the benefit of the filing dates being claimed under 35 U.S.C. § 120 and the disclosures of which are incorporated by reference.

[0002] The present invention relates to medical devices in general, and in particular to devices for supporting internal body organs.

[0003] The mitral valve is a portion of the heart that is located between the chambers of the left atrium and the left ventricle. When the left ventricle contracts to pump blood throughout the body, the mitral valve closes to prevent the blood being pumped back into the left atrium. In some patients, whether due to genetic malformation, disease or injury, the mitral valve fails to close properly causing a condition known as regurgitation, whereby blood is pumped into the atrium upon each contraction of the heart muscle. Regurgitation is a serious, often rapidly deteriorating, condition that reduces circulatory efficiency and must be corrected.

[0004] Two of the more common techniques for restoring the function of a damaged mitral valve are to surgically replace the valve with a mechanical valve or to suture a flexible ring around the valve to support it. Each of these procedures is highly invasive because access to the heart is obtained through an opening in the patient's chest. Patients with mitral valve regurgitation are often relatively frail thereby increasing the risks associated with such an operation.

[0005] One less invasive approach for aiding the closure of the mitral valve involves the placement of a support structure in the cardiac sinus and vessel that passes adjacent the mitral valve. The support structure is designed to push the vessel and surrounding tissue against the valve to aid its closure. This technique has the advantage over other methods of mitral valve repair because it can be performed percutaneously without opening the chest wall. While this technique appears promising, some proposed supports appear to limit the amount of blood that can flow through the coronary sinus and may contribute to the formation of thrombosis in the vessel. Therefore, there is a need for a tissue support structure that does not inhibit the flow of blood in the vessel in which it is placed and reduces the likelihood of thrombosis formation. Furthermore, the device should be flexible and securely anchored such that it moves with the body and can adapt to changes in the shape of the vessel over time.

[0006] The present invention is an intravascular support that is designed to change the shape of a body organ that is adjacent to a vessel in which the support is placed. In one embodiment of the invention, the support is designed to aid the closure of a mitral valve. The support is placed in a coronary sinus and vessel that are located adjacent the mitral valve and urges the vessel wall against the valve to aid its closure.

[0007] The intravascular support of the present invention includes a proximal and distal anchor and a support wire or reshaper disposed therebetween. The proximal and distal anchors circumferentially engage a vessel in which the support is placed. A support wire is urged against the vessel by the proximal and distal anchors to support the tissue adjacent the vessel.

[0008] In one embodiment of the invention, the proximal and distal supports are made from a wire hoop that presents a low metal coverage area to blood flowing within the vessel. The wire hoops may allow tissue to grow over the anchors to reduce the chance of thrombosis formation. The wire hoops have a figure eight configuration and can expand to maintain contact with the vessel walls if no vessel expands or changes shape.

[0009] In another embodiment of the invention, the proximal and distal anchors of the intravascular support are rotationally offset from each other. Locks on the support wire allow a physician to ensure that the anchors have been successfully deployed and prevent the support wire from collapsing within a vessel.

[0029] As indicated above, the present invention is a medical device that supports or changes the shape of tissue that is adjacent a vessel in which the device is placed. The present invention can be used in any location in the body where the tissue needing support is located near a vessel in which the device can be deployed. The present invention is particularly useful in supporting a mitral valve in an area adjacent a coronary sinus and vessel. Therefore, although the embodiments of the invention described are designed to support a mitral valve, those skilled in the art will appreciate that the invention is not limited to use in supporting a mitral valve.

[0030] FIG. 1 illustrates a mitral valve 20 having a number of flaps 22, 24 and 26 that should overlap and close when the ventricle of the heart contracts. As indicated above, some hearts may have a mitral valve that fails to close properly thereby creating one or more gaps 28 that allow blood to be pumped back into the left atrium each time the heart contracts. To add support to the mitral valve such that the valve completely closes, an intravascular support 50 is placed in a coronary sinus and vessel 60 that passes adjacent one side of the mitral valve 20. The intravascular support 50 has a proximal anchor 52, a distal anchor 54, and a support wire 56 or reshaper extending between the proximal and distal anchors. With the anchors 52 and 54 in place, the support wire 56 exerts a force through the coronary sinus wall on the postero-lateral mitral valve 20 thereby closing the one or more gaps 28 formed between the valve flaps. With the intravascular support 50 in place; the function of the mitral valve is improved.

[0031] As will be explained in further detail below, each of the proximal and distal anchors 52, 54 preferably circumferentially engages the wall of the vessel 60 in which it is placed. The support wire 56 is secured to a peripheral edge of the proximal and distal anchors such that the support wire is urged by the anchors against the vessel wall. Therefore, the support wire 56 and anchors 52, 54 present a minimal obstruction to blood flowing within the vessel.

[0032] FIG. 2 shows one possible method of delivering the intravascular support of the present invention to a desired location in a patient's body. An incision 80 is made in the patient's skin to access a blood vessel. A guide catheter 82 is advanced through the patient's vasculature until its distal end is positioned adjacent the desired location of the intravascular support. After positioning the guide catheter 82, a delivery catheter and advancing mechanism 84 are inserted through the guide catheter 82 to deploy the intravascular support at the desired location in the patient's body. Further detail regarding one suitable advancing mechanism 84 is described in commonly assigned U.S. patent application Ser. No. 10/313,914, filed Dec. 5, 2002, the disclosure of which is hereby incorporated by reference.

[0033] FIG. 3 illustrates one embodiment of an intravascular support in accordance with the present invention. The intravascular support 100 includes a support wire 102 having a proximal end 104 and a distal end 106. The support wire 102 is made of a biocompatible material such as stainless steel or a shape memory material such as nitinol wire.

[0034] In one embodiment of the invention, the support wire 102 comprises a double length of nitinol wire that has both ends positioned within a distal crimp tube 108. To form the support wire 102, the wire extends distally from the crimp tube 108 where it is bent to form a distal stop loop (see 121 in FIG. 4) having a diameter that is larger than the lumens within the distal crimp tube 108. After forming the distal stop loop, the wire returns proximally through the crimp tube 108 towards the proximal end of the support 100. Proximal to the proximal end of the crimp tube 108, is a distal lock 110 that is formed by the support wire bending away from the longitudinal axis of the support 102 and then being bent parallel to the longitudinal axis of the support before being bent again towards the longitudinal axis of the support. Therefore, the bends in the support wire form a half 110a of the distal lock that is used to secure the distal anchor in the manner described below. From the distal lock 110, the wire continues proximally through a proximal crimp tube 112. On exiting the proximal end of the proximal crimp tube 112, the wire is bent to form an arrowhead-shaped proximal lock 114. The wire of the support 102 then returns distally through the proximal crimp tube 112 to a position just proximal to the proximal end of the distal crimp tube 108 wherein the wire is bent to form a second half 110b of the distal lock 110.

[0035] Support wire 102 has a length that is selected based on its intended destination within a patient's vessel. For use in supporting a mitral valve, the support wire is preferably between one and six inches long and has a curved bend between its proximal end 104 and distal end 106 with a radius of curvature between 1 and 3 inches and most preferably with a radius of curvature of 1.8 inches. In addition, the wire used to form the support wire 102 is flexible enough to move with each heartbeat (thereby changing the force applied to the mitral valve annulus during the heartbeat) and stiff enough to support the mitral valve. In one embodiment, the wire used to form the support wire 102 is made of nitinol having a modulus of elasticity of 5-20×10⁶ psi and a diameter of between 0.0110″ and 0.0150″ and most preferably 0.0140″. Other shape memory materials may be used for support wire as well.

[0036] At the distal end of the support wire 102 is a distal anchor 120 that is formed of a flexible wire such as nitinol or some other shape memory material. As is best shown in FIGS. 3 and 4, the wire forming the distal anchor has one end positioned within the distal crimp tube 108. After exiting the distal end of the crimp tube 108, the wire forms a figure eight configuration whereby it bends upward and radially outward from the longitudinal axis of the crimp tube 108. The wire then bends back proximally and crosses the longitudinal axis of the crimp tube 108 to form one leg of the figure eight. The wire is then bent to form a double loop eyelet or loop 122 around the longitudinal axis of the support wire 102 before extending radially outwards and distally back over the longitudinal axis of the crimp tube 108 to form the other leg of the figure eight. Finally, the wire is bent proximally into the distal end of the crimp tube 108 to complete the distal anchor 120.

[0037] The distal anchor is expanded by sliding the double eyelet 122 of the distal anchor from a position that is proximal to the distal lock 110 on the support wire to a position that is distal to the distal lock 110. The bent-out portions 110a and 110b of support wire 110 are spaced wider than the width of double eyelet 122 and provide camming surfaces for the locking action. Distal movement of eyelet 122 pushes these camming surfaces inward to permit eyelet 122 to pass distally of the lock 110, then return to their original spacing to keep eyelet 122 in the locked position.

[0038] The dimensions of the distal anchor are selected so that the diameter of the distal anchor in a plane perpendicular to the axis of the lumen in which the anchor is deployed is preferably between 100% and 300%, most preferably between 130% and 200%, of the diameter of the lumen prior to deployment. When treating mitral valve regurgitation by placement of the device in the coronary sinus, the diameter of the coronary sinus may expand over time after deployment. Oversizing the anchor combined with the inherent deformability and recoverability properties of the anchor material (particularly nitinol or some other shape memory material) enables the anchor to continue to expand from its initial deployment size as the lumen distends and expands over time.

[0039] Upon expansion, the distal anchor circumferentially engages the vessel wall with a radially outwardly directed force that is distributed unequally around the circumference of the anchor by distending the vessel wall in variable amounts along the axial length of the anchor. The unequal distribution of force helps the anchor contact the lumen wall securely by creating bumps and ridges that are not parallel to the central axis of the lumen. In its expanded configuration the distal anchor's diameter is at least 50%-500% and most preferably 100%-300% of the anchor's diameter in the unexpanded configuration. The open cross-sectional area of the lumen through the anchor is at least 50% and most preferably 80%-100% of the lumen cross-sectional area prior to redeployment of the anchor.

[0040] In addition, the metal coverage of the anchor, as defined by the percentage of the lumen surface area through which the anchor extends that is exposed to a metal surface, is between 5% and 30% and most preferably 10%. The wire used to form the distal anchor 120 is preferably nitinol having a diameter of between 0.0110″ and 0.0150″ and most preferably 0.0140 inches. Other shape memory materials may be used as well.

[0041] During insertion, a physician can tactilely feel when the eyelet 122 has been slid over the distal lock 110 in order to determine when the distal anchor has been set within a vessel lumen. In addition, if the anchor is misplaced, it can be collapsed by pulling the eyelet 122 proximally over the distal lock 110 and repositioning the anchor in the unexpanded configuration. The force required to capture the distal anchor is preferably less than 20 lbs. and more preferably less than 10 lbs.

[0042] FIG. 4 also illustrates how the crimp tube 108 is held in place between the distal lock 110 on the proximal side and the stop loop 121 at the distal end of the support wire 102. The wires of the distal anchor 120 exit the distal end of the crimp tube 108 at an angle of approximately 45 degrees before looping back over the length of the distal crimp tube 108. Therefore, the distal end of the anchor is relatively atraumatic to avoid damage to a vessel during placement.

[0043] At the proximal end of the intravascular support is a proximal anchor 140 that is preferably formed of a biocompatible, elastic wire such as stainless steel or a shape memory material such as nitinol. As is best shown in FIGS. 3 and 5, the proximal anchor 140 in one embodiment is made of a single length of wire having a first end positioned within a proximal crimp tube 112. The wire extends distally from the crimp tube 112 and bends radially outward and away from the longitudinal axis of the crimp tube 112 before being bent proximally and crossing the longitudinal axis of the crimp tube 112 in order to form a first leg of a figure eight configuration. The wire then is bent to form a double eyelet or loop 142 around the longitudinal axis of the support wire 102 wherein the eyelet 142 has a diameter that allows it to be forced over the proximal lock 114. After forming the eyelet 142, the wire extends outwardly and away from the longitudinal axis of the crimp tube 112 before being bent distally over and across the longitudinal axis of the crimp tube 112 to form the second leg of a figure eight. Finally, the wire is bent proximally and extends into the distal end of the crimp tube 112.

[0044] Like the distal anchor, the proximal anchor is expanded and locked by sliding the double eyelet 142 of the proximal anchor from a position that is proximal to the proximal lock 114 on the support wire to a position that is distal to the proximal lock 114. As can be seen in FIG. 7, the proximal lock 114 has an “arrowhead” shape whereby the proximal end of the lock is bent away from the longitudinal axis of the support wire at an angle that is less steep than the distal end of the proximal lock. The less steep section makes it easier to advance the eyelet 142 over the lock in the distal direction than to retrieve the eyelet 142 over the proximal lock 114 in the proximal direction. Distal movement of eyelet 142 cams the less steep proximal surfaces inward to permit eyelet 142 to pass distally of the lock 114, then return to their original spacing to keep eyelet 142 in the locked position.

[0045] As can be seen by comparing the proximal anchor 140 with the distal anchor 120 in FIG. 3, the proximal anchor has a larger radius of curvature because it is designed to fit within a larger diameter portion of the coronary sinus. The dimensions of the proximal anchor are selected so that the diameter of the proximal anchor in a plane perpendicular to the axis of the lumen in which the anchor is deployed is preferably between 100% and 300%, most preferably between 130% and 200%, of the diameter of the lumen prior to deployment. As with the distal anchor, oversizing the proximal anchor combined with the inherent deformability and recoverability properties of the anchor material (particularly nitinol or some other shape memory material) enables the anchor to continue to expand from its initial deployment size as the lumen distends and expands over time.

[0046] Upon expansion, the proximal anchor circumferentially engages the vessel wall with a radially outwardly directed a force that is distributed unequally around the circumference of the anchor by distending the vessel wall in variable amounts along the axial length of the anchor. As with the distal anchor, the unequal distribution of force helps the proximal anchor contact the lumen wall securely by creating bumps and ridges that are not parallel to the central axis of the lumen. In its expanded configuration the proximal anchor's diameter is at least 50%-500% and most preferably 100%-300% of the anchor's diameter in the unexpanded configuration. The open cross-sectional area of the lumen through the anchor is at least 50% and most preferably 80%-100% of the lumen cross-sectional area prior to redeployment of the anchor.

[0047] In one embodiment of the invention, the proximal and distal anchors are oriented such that the planes of the anchors are offset with respect to each other by an angle of approximately 30 degrees. The offset helps the intravascular support 100 seat itself in the coronary sinus and vessel surrounding the mitral valve in certain mammals. However, it will be appreciated that if the support is designed for other uses, the proximal and distal anchors may be offset by more or less depending upon the anatomy of the intended destination.

[0048] FIGS. 6A-6C illustrate cross-sectional views of the crimp tubes in which the wires that form the support wire 102 and proximal and distal anchors 120, 140 are threaded. In one embodiment, the crimp tubes comprise a biocompatible material such as titanium having a number of holes extending longitudinally through the tube through which the wires are threaded. In FIG. 6A, a tube 150 has four holes 152, 154, 156, 158 positioned in approximately a square configuration within the circumference of the tube 150. As shown in FIG. 6B, a tube 160 includes four holes 162, 164, 166, 168 therein that are positioned in a diamond configuration. FIG. 6C shows another tube 170 having four holes 172, 174, 176, 178. Here the holes 172, 174 lie in a first plane and the second pair of holes 176, 178 lie in a second plane that is offset from the plane of the holes 172, 174. By changing the orientation of the holes 176, 178 with respect to the holes 172, 174, the relative plane of wires passing through the holes can be adjusted. Thus in the example shown in FIG. 3, the proximal anchor may be formed with a crimp tube such as that shown in FIG. 6A or FIG. 6B while the proximal anchor may be formed in a crimp tube such as that shown in FIG. 6C in order to adjust the angular orientation between the proximal anchor and the distal anchor. In an alternative embodiment, the crimp tubes at the proximal and distal ends of the support wire 102 are the same and the angular offset between the proximal and distal anchor is achieved by bending the wires at the desired angle. Although the crimp tubes shown use one hole for each wire passing through the crimp tube, it will be appreciated that other configurations may be provided such as slots or other passages for the wires to pass through.

[0049] In another embodiment, the distal and proximal anchors are attached to the support wire by a wire, such as nitinol wire or other shape memory material. The attaching wire may be spiral wrapped around the base of each anchor and around the support wire. In another embodiment, each anchor may be attached to the support wire by wrapping the anchor wire around the support wire. In yet another embodiment, the two anchors and the support wire may be made from a single wire, such as nitinol wire or other shape memory material.

[0050] FIG. 8 illustrates one method for delivering an intravascular support 100 in accordance with the present invention to a desired location in the body. As indicated above, intravascular support 100 is preferably loaded into and routed to a desired location within a catheter 200 with the proximal and distal anchors in a collapsed or deformed condition. That is, the eyelet 122 of the distal anchor 120 is positioned proximally of the distal lock 110 and the eyelet 142 of the proximal anchor 140 is positioned proximal to the proximal lock 114. The physician ejects the distal end of the intravascular support from the catheter 200 into the lumen by advancing the intravascular support or retracting the catheter or a combination thereof. A pusher (not shown) provides distal movement of the intravascular support with respect to catheter 200, and a tether 201 provides proximal movement of the intravascular support with respect to catheter 200. Because of the inherent recoverability of the material from which it is formed, the distal anchor begins to expand as soon as it is outside the catheter. Once the intravascular support is properly positioned, the eyelet 122 of the distal anchor is pushed distally over the distal lock 110 so that the distal anchor 120 further expands and locks in place to securely engage the lumen wall and remains in the expanded condition. Next, the proximal end of the support wire 102 is tensioned by applying a proximally-directed force on the support wire and distal anchor to apply sufficient pressure on the tissue adjacent the support wire to modify the shape of that tissue. In the case of the mitral valve, fluoroscopy, ultrasound or other imaging technology may be used to see when the support wire supplies sufficient pressure on the mitral valve to aid in its complete closure with each ventricular contraction without otherwise adversely affecting the patient. A preferred method of assessing efficacy and safety during a mitral valve procedure is disclosed in copending U.S. patent application Ser. No. 10/366,585, filed Feb. 12, 2003, and titled “Method of Implanting a Mitral Valve Therapy Device,” the disclosure of which is incorporated herein by reference. Once the proper pressure of the support wire has been determined, the proximal anchor is deployed from the catheter and allowed to begin its expansion. The eyelet 142 of the proximal anchor 140 is advanced distally over the proximal lock 114 to expand and lock the proximal anchor, thereby securely engaging the lumen wall and maintaining the pressure of the support wire against the lumen wall. Finally, the mechanism for securing the proximal end of the intravascular support can be released. In one embodiment, the securement is made with a braided loop 202 at the end of tether 201 and a hitch pin 204. The hitch pin 204 is withdrawn thereby releasing the loop 202 so it can be pulled through the proximal lock 114 at the proximal end of the intravascular support 100.

[0051] In many contexts, it is important for the device to occupy as little of the lumen as possible. For example, when using the device and method of this invention to treat mitral valve regurgitation, the device should be as open as possible to blood flow in the coronary sinus (and to the introduction of other medical devices, such as pacing leads) while still providing the support necessary to reshape the mitral valve annulus through the coronary sinus wall. The combination of the device's open design and the use of nitinol or some other shape memory material enables the invention to meet these goals. When deployed in the coronary sinus or other lumen, the device preferably occupies between about 1.5% and about 5.5% of the overall volume of the section of lumen in which it is deployed.

[0052] In many embodiments of the invention, the use of a shape memory material such as nitinol is particularly important. The percentage of shape memory material by volume in the device is preferably between about 30% and 100%, most preferably between about 40% and 60%.

[0053] In some instances it may be necessary to move or remove an intravascular support after deployment by recapturing the device into a catheter. Prior to deployment of the proximal anchor, the distal anchor may be recaptured into the delivery catheter by simultaneously holding the device in place with tether 201 while advancing catheter distally over distal anchor 120 so that the entire device is once again inside catheter 200. The distally directed force of the catheter collapses distal anchor 120 into a size small enough to fit into catheter 200 again. Likewise, after deployment of both anchors but prior to releasing the securement mechanism as described above, the intravascular support may be recaptured into the delivery catheter by simultaneously holding the device in place with tether 201 while advancing catheter distally first over proximal anchor 140, over support wire 102, and finally over distal anchor 120. The distally directed forced of catheter 200 collapses anchors 120 and 140 into a size small enough to fit into catheter 200 again. If the securement mechanism has been detached from the device prior to recapture, the device still may be recaptured into the delivery catheter or another catheter by grasping the proximal end of the device with a grasper or tether and by advancing the catheter distally over the device.

[0054] In one embodiment of the invention, proximal anchor 140 includes a recapture guidance and compression element. In the embodiment shown in FIG. 5, the slope of the two proximal arms 143 and 144 of proximal anchor 140 is small in proximal portions 145 and 146 of the arms, then increases in more distal portions 147 and 148 of the arms. This shape guides the catheter to move distally over the anchor more easily and to help compress the anchor to a collapsed shape as the catheter advances during recapture.

[0055] Likewise, the two proximal arms 123 and 124 of distal anchor 120 have a shallower slope in their proximal portions 145 and 146 and an increased slope in more distal portions 147 and 148. While recapture of the distal anchor is somewhat easier due to its smaller size compared to the proximal anchor, this recapture guidance and compression feature enhances the ease with which recapture is performed.

[0056] FIG. 9 illustrates an alternative embodiment of the intravascular support of the present invention. In this embodiment, an intravascular support 250 has a support wire 252 and a distal anchor 254 and a proximal anchor 256. In the embodiment shown in FIG. 9, the distal anchor 254 is made from the same wire used to form the support wire 252. As best shown in FIG. 10, the wire used to form the support wire 252 extends distally through a distal crimp tube 260 before looping radially outward and returning proximally and across the longitudinal axis of the crimp tube 260 to form one leg of a figure eight. The wire then winds around the axis of the suspension wire 252 to form an eyelet 262. The wire then continues radially outward and distally across the longitudinal axis of the crimp tube 260 to form the second leg of a figure eight. After forming the figure eight, the wire enters the distal end of the crimp tube 260 in the proximal direction to form the other half of the support wire 252. A distal lock 264 is formed proximal to the distal crimp tube 260 by outwardly extending bends in the wires that form the support wire 252. The distal lock 264 prevents the double eyelet 262 from sliding proximally and collapsing the distal anchor 254 when positioned in a vessel.

[0057] As shown in FIG. 11, a proximal anchor 256 is constructed in a fashion similar to the proximal anchor 140 shown in FIG. 3. That is, the proximal anchor 256 is formed of a separate wire than the wire sued to form the support wire 252 and distal anchor 254. The wire of the proximal anchor has one end within a proximal crimp tube 270. The wire extends distally out of the end of the crimp tube and bends radially outward before returning back and across the longitudinal axis of the crimp tube 270. At the proximal end of the crimp tube 270, the wire of the proximal anchor forms a double eyelet 272 around the longitudinal axis of the support wire 252. The wire then continues radially outward and distally over the longitudinal axis of the crimp tube 270 to form the second leg of the figure eight whereupon it is bent proximally into the distal end of the crimp tube 270.

[0058] FIG. 12 shows yet another embodiment of an intravascular support in accordance with the present invention. Here, an intravascular support 300 comprises a support wire 302, a distal anchor 304 and a proximal anchor 306. As in the embodiment shown in FIG. 9, the distal anchor 304 and the support wire 302 are formed of the same wire. To form the distal anchor, the wire extends distally through a distal crimp tube 310 and exits out the distal end before extending radially outward and bending back and across the longitudinal axis of the crimp tube 310 to form one leg of a figure eight. The loop then forms an eyelet 312 around the longitudinal axis of the support wire 302 before bending radially outward and distally across the longitudinal axis of the crimp tube 310 to form a second leg of the figure eight. The wire then enters the distal end of the crimp tube 310 in the proximal direction. The support wire 302 may have one or two outwardly extending sections that form a distal stop 314 to maintain the position of the eyelet 312 once the distal anchor is set in the expanded configuration.

[0059] The proximal anchor 306 is formed from a separate wire as shown in FIG. 14. The wire has one end positioned within the proximal crimp tube 320 that extends distally outward and radially away from the longitudinal axis of the crimp tube 320 before being bent proximally and across the longitudinal axis of the crimp tube 320 to form one leg of the figure eight. The wire then winds around the longitudinal axis of the support wire to form an eyelet 322 before being bent distally and across the longitudinal axis of the crimp tube 320 to enter the distal end of the crimp tube 320 in the proximal direction. As will be appreciated, the proximal crimp tube 320 of the embodiment shown in FIG. 12 holds four wires wherein the distal crimp tube 310 need only hold two wires.

[0060] FIGS. 15-18 show other embodiments of the invention. In the embodiment shown in FIG. 15, the intravascular support has an anchor 400 formed as a loop 404 emerging from a window 406 in a crimp tube 408. Extending from one end 411 of crimp tube 408 is a support strut 410 which connects with loop 404. Also extending from the crimp tube 408 is a support wire 412. Loop 404 and support 410 may be formed from nitinol, stainless steel, or any other appropriate material. The intravascular support includes another anchor. The intravascular support of this embodiment may be delivered and deployed in the manner discussed above with respect to the embodiment described above.

[0061] FIG. 16 shows another embodiment of an anchor 450 for an intravascular support. Anchor 450 is formed from two loops 452 and 454 emerging from a window 456 and an end 457 of a crimp tube 458. A support wire 462 also extends from the crimp tube. Loops 452 and 454 may be formed from nitinol, stainless steel, or any other appropriate material. The intravascular support includes another anchor. The intravascular support of this embodiment may be delivered and deployed in the manner discussed above with respect to the embodiment described above.

[0062] FIG. 17 shows yet another embodiment of an anchor 500 for an intravascular support according to this invention. Anchor 500 is formed from two loops 502 and 504 emerging from a window 506 and an end 507 of a crimp tube 508. A cross strut 505 connects the loops. A support wire 512 also extends from the crimp tube. Loops 502 and 504 and strut 505 may be formed from nitinol, stainless steel, or any other appropriate material. The intravascular support includes another anchor. The intravascular support of this embodiment may be delivered and deployed in the manner discussed above with respect to the embodiment described above.

[0063] FIG. 18 is a modification of the embodiment shown in FIGS. 3-7. In this embodiment, torsional springs 558 of proximal anchor 550 have been formed as single loops or eyelets in the anchor's wire 552. These springs make the anchor 550 more compliant by absorbing some of the force applied to the anchor during locking. While FIG. 18 shows a proximal anchor with two springs 558, any number of springs could be used on either the proximal or the distal anchor.

[0064] While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the scope of the invention. Therefore, the scope of the invention is to be determined from the following claims and equivalents thereto.