US 20080015679 A1
An intravascular support device includes a support or reshaper wire, a proximal anchor and a distal anchor. The support wire engages a vessel wall to change the shape of tissue adjacent the vessel in which the intravascular support is placed. The anchors and support wire are designed such that the vessel in which the support is placed remains open and can be accessed by other devices if necessary. The device provides a minimal metal surface area to blood flowing within the vessel to limit the creation of thrombosis. The anchors can be locked in place to secure the support within the vessel.
1. A device for modifying the shape of tissue adjacent to a lumen, the device comprising:
an anchor adapted to be deployed by a catheter and expanded to an expanded condition to engage the lumen after deployment from the catheter;
a support extending from the anchor along a longitudinal axis and adapted to engage the lumen; and
a recapture mechanism adapted to assist the recapture of at least a portion of the device into the catheter, wherein the recapture mechanism comprises a first surface on the anchor and a second surface on the anchor, the slope of the first surface with respect to the longitudinal axis being less than the slope of the second surface with respect to the longitudinal axis, the first surface being closer to the longitudinal axis than the second surface is to the longitudinal axis.
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12. A device for modifying the shape of tissue adjacent to a lumen, the device comprising:
an anchor adapted to be deployed by a catheter and expanded to an expanded condition to engage the lumen after deployment from the catheter, the anchor comprising a wire;
a support extending from the anchor and adapted to engage the lumen;
a crimp attaching the wire to the support; and
a recapture mechanism adapted to assist the recapture of at least a portion of the device into the catheter by compressing the anchor from the expanded condition to a collapsed shape, wherein the recapture mechanism comprises a first surface on the anchor wire and a second surface on the anchor wire, the slope of the first surface with respect to the crimp less than the slope of the second surface with respect to the crimp, the first surface being closer to the crimp than the second surface is to the crimp.
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This application is a continuation of pending U.S. application Ser. No. 10/429,172, filed May 2, 2003, entitled “Device and Method for Modifying the Shape of a Body Organ,” which application is incorporated by reference as if fully set forth herein.
The present invention relates to medical devices in general, and in particular to devices for supporting internal body organs.
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.
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.
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.
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.
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.
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.
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.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
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.
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.
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
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.
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
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 110 a and 110 b 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.
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.
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.
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.
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.
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
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
As can be seen by comparing the proximal anchor 140 with the distal anchor 120 in
Upon expansion, the proximal 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. 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.
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.
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.
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.
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%.
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.
In one embodiment of the invention, proximal anchor 140 includes a recapture guidance and compression element. In the embodiment shown in
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.
As shown in
The proximal anchor 306 is formed from a separate wire as shown in
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.