US 20050137694 A1
The present invention provides methods and apparatus for endovascularly replacing a patient's heart valve. The apparatus includes a replacement valve and an anchor having an expandable braid. In some embodiments, the expandable braid is fabricated from a single strand of wire. In some embodiments, the expandable braid comprises at least one turn feature. The anchor and the valve preferably are configured for endovascular delivery and deployment.
1. Apparatus for replacing a native aortic valve, the apparatus comprising:
an anchor comprising an expandable braid, the anchor being adapted to be endovascularly delivered and expanded via active foreshortening at an anchor site within the native aortic valve; and
a replacement valve configured to be secured within the anchor.
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This application is a continuation-in-part application of U.S. Ser. No. 10/746,280, filed Dec. 23, 2003.
Heart valve surgery is used to repair or replace diseased heart valves. Valve surgery is an open-heart procedure conducted under general anesthesia. An incision is made through the patient's sternum (sternotomy), and the patient's heart is stopped while blood flow is rerouted through a heart-lung bypass machine.
Valve replacement may be indicated when there is a narrowing of the native heart valve, commonly referred to as stenosis, or when the native valve leaks or regurgitates. When replacing the valve, the native valve is excised and replaced with either a biologic or a mechanical valve. Mechanical valves require lifelong anticoagulant medication to prevent blood clot formation, and clicking of the valve often may be heard through the chest. Biologic tissue valves typically do not require such medication. Tissue valves may be obtained from cadavers or may be porcine or bovine, and are commonly attached to synthetic rings that are secured to the patient's heart.
Valve replacement surgery is a highly invasive operation with significant concomitant risk. Risks include bleeding, infection, stroke, heart attack, arrhythmia, renal failure, adverse reactions to the anesthesia medications, as well as sudden death. Two to five percent of patients die during surgery.
Post-surgery, patients temporarily may be confused due to emboli and other factors associated with the heart-lung machine. The first 2-3 days following surgery are spent in an intensive care unit where heart functions can be closely monitored. The average hospital stay is between 1 to 2 weeks, with several more weeks to months required for complete recovery.
In recent years, advancements in minimally invasive surgery and interventional cardiology have encouraged some investigators to pursue percutaneous replacement of the aortic heart valve. See, e.g., U.S. Pat. No. 6,168,614. In many of these procedures, the replacement valve is deployed across the native diseased valve to permanently hold the valve open, thereby alleviating a need to excise the native valve and to position the replacement valve in place of the native valve.
In the endovascular aortic valve replacement procedure, accurate placement of aortic valves relative to coronary ostia and the mitral valve is critical. Some self-expanding valve anchors have had very poor accuracy in deployment, however. In a typical deployment procedure, the proximal end of the stent is not released from the delivery system until accurate placement is verified by fluoroscopy. The stent often jumps to another position once released, making it impossible to know where the ends of the stent will be after release with respect to the native valve, the coronary ostia and the mitral valve.
Also, visualization of the way the new valve is functioning prior to final deployment is very desirable. Due to the jumping action of some self-expanding anchors, and because the replacement valve is often not fully functional before final deployment, visualization of valve function and position prior to final and irreversible deployment is often impossible with these systems.
Another drawback of prior art self-expanding replacement heart valve systems is their relative lack of radial strength. In order for self-expanding systems to be easily delivered through a delivery sheath, the metal needs to flex and bend inside the delivery catheter without being plastically deformed. Expandable stent designs suitable for endovascular delivery for other purposes may not have sufficient radial strength to serve as replacement heart valve anchors. For example, there are many commercial arterial stent systems that apply adequate radial force against the artery wall to treat atherosclerosis and that can collapse to a small enough of a diameter to fit inside a delivery catheter without plastically deforming. However when the stent has a valve fastened inside it, and that valve must reside within the heart, as is the case in aortic valve replacement, the anchoring of the stent to vessel walls takes significantly more radial force, especially during diastole. The force to hold back arterial pressure and prevent blood from going back inside the ventricle during diastole will be directly transferred to the stent/vessel wall interface. Therefore, the amount of radial force required to keep the self-expanding stent/valve in contact with the vessel wall and not sliding is much higher than in stents that do not have valves inside of them. Moreover, a self-expanding stent without sufficient radial force will end up dilating and contracting with each heartbeat, thereby distorting the valve, affecting its function and possibly causing it to migrate and dislodge completely. Simply increasing strut thickness of the self-expanding stent is not a good solution as it increases profile and/or a risk of plastic deformation of the self-expanding stent.
In view of drawbacks associated with previously known techniques for endovascularly replacing a heart valve, it would be desirable to provide methods and apparatus that overcome those drawbacks.
The present invention relates to an apparatus for replacing a patient's native heart valve. The apparatus comprises an anchor having an expandable braid adapted for endovascular delivery. The anchor is further adapted for expansion via active foreshortening at an anchor site within the native valve. The apparatus also includes a replacement valve adapted to be secured within the patient. In some embodiments, the anchor braid is further adapted to remain substantially undeformed in response to a pressure up to 0.5 atm or 2 atm directed substantially radially inward toward the central axis. In some embodiments, the anchor braid comprises a first region and a second region having a diameter larger than a diameter of the first region when the anchor is expanded. In some embodiments, the anchor braid is configured to have an expanded shape that is radially symmetrical, bilaterally symmetrical, or asymmetrical. In some embodiments, the anchor comprises first and second wires, the first wire having a diameter smaller than a diameter of the second wire. In some embodiments, the anchor comprises first and second wires formed from different materials. In some embodiments, the anchor has a collapsed delivery configuration, an at-rest configuration and an expanded deployed configuration.
In some embodiments, the apparatus herein further comprises a lock or a plurality of locks configured to maintain expansion of the braid. In some embodiments, the apparatus herein further comprises a valve support adapted to support the replacement valve within the anchor. In some embodiments, the anchor herein comprises a distal deployment system interface at a distal end of the anchor, the distal deployment system interface being adapted to permit a deployment system to apply a proximally directed force on the distal end of the anchor. In some embodiments, the anchor comprises a proximal deployment system interface at a proximal end of the anchor, the proximal deployment system interface being adapted to permit a deployment system to apply a distally directed force on the proximal end of the anchor.
All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.
The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:
The present invention relates to a delivery system, apparatus and methods for endovascularly delivering and deploying an aortic prosthesis within a patient's native heart valve, referred to here out as replacing a patients heart valve. The delivery system includes a sheath assembly and a guide wire for placing the apparatus endovascularly within a patient and a user control allowing manipulation of the aortic prosthesis. The apparatus includes an anchor and a replacement valve. The anchor includes an expandable braid. In preferred embodiments, the expandable braid includes closed edges. The replacement valve is adapted to be secured within the anchor, and as such, be delivered endovascularly to patient's heart to replace the patient's native heart valve. More preferably, the apparatus and methods of the present invention contemplate the replacement of a patient's aortic valve.
Control handle 120 is coupled to multi-lumen shaft 108. A knob 122 disposed in slot 123 is coupled to the distal region control wires for controlling movement of the distal region of apparatus 10. Likewise, a knob 124 disposed in slot 125 is coupled to proximal region control wires 112 for control of the proximal region of apparatus 10. Handle 120 may also have a knob 126 for, e.g., decoupling the proximal and/or distal region control wires from apparatus 10, or for performing other control functions.
Apparatus 10 has an anchor 30 and a replacement valve 20. Anchor 30 preferably comprises a braid. Such braid can have closed ends at either or both its ends. Replacement valve 20 is preferably coupled to the anchor along posts 32. Post 32 therefore, may function as valve support and may be adapted to support the replacement valve within the anchor. In the embodiment shown, there are three posts, corresponding to the valve's three commissure points. The posts can be attached to braid portion of anchor 30. The posts can be attached to the braid's distal end, as shown in
Anchor 30 has also a plurality of buckles 34 attached to its proximal region, one for each post 32. Posts 32 and buckles 34 form a two-part locking mechanism for maintaining anchor 30 in a deployed or expanded configuration (e.g., as illustrated in
In this embodiment, anchor 30 is formed from collapsible and expandable wire braid. Anchor braid 30 is preferably self-expanding and is preferably formed from a material such as Nitinol, cobalt-chromium steel or stainless steel wire using one or more strands of wire. While the illustrated embodiment is formed from a single strand of wire, in other embodiments may benefit from a wire braid formed of 2-20 wires, more preferably 3-15 wires, or more preferably 4-10 wires.
Delivery and deployment of braided anchor 30 is similar to the delivery and deployment of the anchors described in U.S. patent application Ser. No. 10/746,280 filed Dec. 23, 2003, the disclosure of which is incorporated herein by reference. Specifically, in one embodiment described below, during deployment braided anchor 30 is actively foreshortened by proximally retracting the distal region control wires relative to control tubes 106 to expand and lock the anchor in place. In some embodiments, foreshortening expands anchor 30 to a radially symmetrical, bilaterally symmetrical, or asymmetrical expanded shape (as further described below). The foreshortening step can include expanding a first region of the anchor to a first diameter and a second region of the anchor to a second diameter larger than the first diameter. A third region may also be expanded to a diameter larger than the first diameter. The expansion of various regions of the anchor (e.g., the distal region) can be especially useful in locating the aortic valve and centering the anchor within it. Preferably, the secured anchor does not interfere with the mitral valve or the ostias. In some embodiments, the anchor is allowed to self expand prior to the foreshortening step.
As seen in
In its collapsed configuration, anchor 30 preferably has a collapsed delivery diameter between about 3 to 30 Fr, or more preferably 6 to 28 Fr, or more preferably 12 to 24 Fr. In some embodiments, anchor 30 in its collapsed configuration will have a length ranging from about 5 to about 170, more preferably from about 10 to about 160, more preferably from about 15 to about 150, more preferably from about 20 to about 140 mm, or more preferably from about 25 mm to about 130.
Similarly, in its expanded configuration, anchor 30 preferable has a diameter ranging between about 10 to about 36 mm, or more preferably from about 24 to about 33 mm, or more preferably from about 24 to about 30 mm. In some embodiments, anchor 30 in its expanded configuration will have a length ranging from about 1 to about 50, more preferably from about 2 to about 40, more preferably from about 5 to about 30, or more preferably from about 7 to about 20 mm.
Overall, the ratio of deployed to collapsed/sheathed lengths is preferably between about 0.05 and 0.5, more preferably about 0.1 to 0.35, or more preferably about 0.15 to 0.25. In any of the embodiments herein, anchor 30 in its expanded configuration preferably has a radial crush strength that maintains the anchor substantially undeformed in response to a pressure of up to 0.5 atm directed substantially radially inward toward the central axis, or more preferably up to 2 atm directed substantially radially inward toward the central axis. In addition, in any of the embodiments herein, the anchor has an axial spring constant of between about 10 to 250 g/cm, more preferably between about 20 to 200 g/cm, or more preferably between about 40 to 160 g/cm. In addition, in any of the embodiments herein, the anchor is preferably adapted to support the replacement valve at the anchor site in response to a differential pressure of up to 120 mm Hg, more preferably up to 240 mm Hg, or more preferably up to 320 mm Hg.
These parameters are not intended to be limiting. Additional parameters within the scope of the present invention will be apparent to those of skill in the art.
As seen in
The distal deployment system interface may include control wires that are controlled, e.g., by control knob 122 of control handle 120. Similarly, the proximal regions of anchor 30 may be pushed distally via a proximal deployment system interface at the proximal end of the anchor. The proximal deployment system interface is adapted to permit deployment system to apply a distally directed force to the proximal end of anchor 30 through, e.g., fingers 106, which are controlled by, e.g., Control knob 124 of control handle 120. The proximal deployment system interface may be further adapted to expand radially during application of a distally directed force on the proximal end of the anchor. Preferably, the proximal deployment system interface is adapted to permit deployment system to apply a distally directed force on the proximal end of the anchor system through a plurality of deployment system fingers or tubes 160. Such expansion optionally may be assisted via inflation of a balloon catheter (not shown) reversibly disposed within apparatus 10, as described in U.S. patent application Ser. No. 10/746,280.
Once anchor 30 is fully deployed, posts 32 and buckles 34 of anchor 30 may be used to lock and maintain the anchor in the deployed configuration. In one embodiment, the control wires attached to posts 32 are threaded through buckles 34 so that the proximally directed force exerted on posts 32 by the control wires during deployment pulls the proximal locking end of posts 32 toward and through buckles 34. Such lock optionally may be selectively reversible to allow for repositioning and/or retrieval of apparatus 10 during or post-deployment. Apparatus 10 may be repositioned or retrieved from the patient until the two-part locking mechanism of posts 32 and buckles 34 of anchor 30 have been actuated. When the lock is selectively reversible, the apparatus may be repositioned and/or retrieved as desired, e.g., even after actuation of the two-part locking mechanism. Once again, further details of this and other anchor locking structures may be found in U.S. patent application Ser. No. 10/746,280. Locking mechanisms used herein may also include a plurality of levels of locking wherein each level of locking results in a different amount of expansion. For example, the proximal end of the post can have multiple configurations for locking within the buckle wherein each configuration results in a different amount of anchor expansion.
When apparatus 10 is placed across a patient's diseased heart valve, anchor 30 may be used to displace the patient's native valve leaflets, and replacement valve 20 will thereafter serve in place of the native valve. After final positioning and expansion, apparatus 10 may be decoupled from delivery system 100 by decoupling the proximal and distal region control wires from anchor 30. Decoupling may be actuated using knob 126 of handle 120. After decoupling, delivery system 100 then may be removed from the patient, thereby completing endovascular replacement of a patient's heart valve.
Prior to implantation of replacement valve apparatus described herein, it may be desirable to perform a valvuloplasty on the patient's diseased valve by inserting a balloon into the valve and expanding it using, e.g., saline mixed with a contrast agent. In addition to preparing the valve site for implant, fluoroscopic viewing of the valvuloplasty will help determine the appropriate size of replacement valve implant to use.
FIGS. 2A-F show further details of anchor 30 of apparatus 10.
As shown in
Posts 32 may be coupled to anchor braid 30 via one or more distal holes 36 b. For example, anchor braid 30 may be woven through holes 36 b, or a suture may be routed through holes 36 b and tied to the braid. Buckles 34 may likewise be attached to anchor braid 30 via weaving or suturing.
Alternative locks may be used to lock the anchor of the present invention in the foreshortened configuration. Preferably, a locking mechanism of the present invention can have multiple locking options such that locking can confer a plurality of amounts of expansion. Furthermore, the locking option can be employed asymmetrically to confer non-cylindrical shapes to the anchor. In
Advantageously, providing multiple arrowheads 46 along posts 32 yields a ratchet that facilitates in-vivo determination of a degree of foreshortening imposed upon apparatus of the present invention. Furthermore, optionally constraining appendages 48 of arrowheads 46 via eyelets 49 prevents actuation of lock 40″ (and thus deployment of apparatus of the present invention) even after male element 44′ has been advanced through female element 42. Only after a medical practitioner has removed the wire constraining appendages 48 is lock 40″ fully engaged and deployment no longer reversible.
Lock 40′″ of
In some embodiments, fixture 200 comprises approximately 6-20 posts, more preferably 8-18 posts, or more preferably 10-16 posts around its circumference, though any alternative number of posts may be provided. Likewise, fixture 200 preferably has a diameter of about 2-40 mm, more preferably 4-30 mm, or more preferably 6-20 mm, though any alternative diameter may be provided. The diameter of fixture 200 preferably is the diameter of the braid in its “at rest” configuration.
Fixture 200 can optionally further comprise circumferential grooves 206 to facilitate interweaving of a first section of wire underneath an adjacent section of wire. The fixture optionally also may comprise localized depressions or holes 208 in addition, or as an alternative, to grooves 206. Depressions 208 may be provided at locations where wire segments cross to act as a visual guide for formation of anchor braid 30, as well as to facilitate the interweaving of a first section of wire beneath an adjacent section of wire.
Referring now to FIGS. 4A-D, an illustrative method of using fixture 200 to fabricate braided anchors in accordance with the present invention is described.
As seen in
After passing inner proximal posts 202 a, wire W encircles fixture 200 in a helical spiral while extending towards the distal posts, as seen in
At distal inner posts 202 b, wire W forms turn Tu and is rerouted back towards proximal inner posts 202 a. It should be noted that wire W can form turn Tu in either inner posts 202 or outer posts 204. Turn Tu forms a closed end of the braid. Additional sets of inner and outer posts are also contemplated. The wire once again encircles fixture 200 in a full 360° helical revolution plus one additional post before reaching the proximal inner posts and being rerouted back towards the distal inner posts. This process is repeated with the wire repetitively interwoven at crossing locations between the proximal and distal posts, e.g., via grooves 206 and/or depressions 208, to define the cells of the braid that will provide anchor 30 with desired characteristics. As seen in
When anchor braid 30 is formed from a shape-memory material, the braid may be heat set such that it maintains a desired degree of expansion in an at-rest configuration. The heat set at-rest configuration may comprise, for example, the delivery configuration (e.g., collapsed configuration) of
Referring now to
Stress concentration may increase the rigidity of an anchor braid and/or may impede delivery and deployment, as well as sheathing, of the braid. Thus, in preferred embodiments, a group of cells can be configured to reduce the sheathing force as described herein. Furthermore, to enhance deliverability, stress concentration may require that anchor braid 30 be fabricated from a relatively thin wire W. However, thin wire may not provide anchor braid 30 with adequate radial strength to displace a patient's diseased native heart valve leaflets and/or to anchor apparatus 10 against a patient's anatomy. Conversely, use of a relatively thick wire W may increase stiffness, thereby precluding retrograde delivery of apparatus 10, as well as a risk of kinking at turns in the braid. Thus, in some embodiments, wires varying in thickness may be used, or multiple wires having different thickness may be woven together. Also, wires made from different materials may be used to form an anchor braid.
It may be desirable to reduce stress concentration at the edges of anchor 30 where wire W changes direction and/or to reduce the circumferential stiffness of the anchor braid. The edge characteristics of the anchor may be altered by altering the shape of substantially all anchor braid cells at the anchor's edge (e.g., distal edge and/or proximal edge). Wire turns that control the shape of the edge cells may be formed within anchor braid 30 by routing wire W around optional outer posts 204 of fixture 200 during formation of the braid.
In preferred embodiments, the edge cells may be wrapped using wire, string, or sutures, at a location where the wire overlaps after an end turn as is illustrated in
The edge cell configuration of
Referring now to FIGS. 6A-E, additional configurations for reducing stress concentration and/or circumferential stiffness of anchor braid 30 are illustrated. Such configurations can be used independently or in conjunction with other configurations disclosed herein. Such configurations are preferably used at the anchor's edges to locally reduce the cross-sectional area of substantially all cells or all cells in the anchor braid's edge (e.g., proximal and/or distal). As seen in
Localized reduction may be achieved via a localized etching and/or electropolishing process. Alternatively or additionally, localized grinding of the turns may be utilized. Additional processing techniques will be apparent to those of skill in the art. As seen in
Referring now to FIGS. 7A-J, instead of terminating the beginning and end of wire W of braid 31 at an overlap within the braid, as discussed previously, the two ends of the wire may be terminated at the anchor's edge. Likewise, when braid 31 is fabricated from multiple wires W, the wires (or a subset of the wires) optionally may be joined together or terminated at turn(s) of the braid. In
With reference now to FIGS. 8A-B, alternative anchors of the present invention are described having anchor edge features that facilitate sheathing of the apparatus and reduce the sheathing force. In
Referring now to
In preferred embodiments, the middle section of the anchor may be composed of thicker wire(s) than edge section(s)
The anchors described herein can be, for example, radially symmetrical, bilaterally symmetrical, or asymmetrical. A radially symmetrical anchor is one for which symmetry exists across any diameter. A bilaterally symmetrical anchor is one for which symmetry exists across a finite number if diameters). An asymmetrical anchor is one for which there exists no diameter across which a symmetry may be found.
While preferred embodiments of the present invention are shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.