Patent Description:
One closed procedure employs balloon catheterization where an expandable stent encloses an inflatable balloon. In this procedure, the stent is implanted by inflating the balloon, which causes the stent to expand. The actual positioning of the stent cannot be determined until after the balloon is deflated and, if there is a misplacement of the stent, the process cannot be reversed to reposition the stent.

The other closed procedure employs a compressed stent enclosed by a removable sheath. In this procedure, a stent made from a shape memory alloy, such as Nitinol, is held in a compressed state by a sheath. The stent is implanted by withdrawing the sheath, causing the stent to expand to its nominal shape. Again, if there is a misplacement of the stent, the process cannot be reversed to reposition the stent.

Positioning errors are particularly dangerous when the stent is used to support a cardiac valve. Serious complications and patient deaths have occurred due to malpositioning of the valve at the implant site in the body, using the available stent-mounted valves. Malpositioning of the valve has resulted in massive paravalvular leakage, device migration, and coronary artery obstruction. The majority of these complications were unavoidable, but detected at the time of the procedure. However, due to inability to reposition or retrieve the device, these problems were impossible to reverse or mitigate during the procedure.

<CIT> discusses a luminal medical implant and delivery system therefor. The implants have joint elements for improved expansion characteristics. In an embodiment, a tubular medical implant collapsible for catheter based luminal delivery to a site in a body is provided. The medial implant comprises a first ring element; a second ring element; and a plurality of pivot joints connective said first ring element to said second ring element.

<CIT> discusses an automatically controlled expansion stent having an expansible stent body, actuation means for expanding the stent body, and control means for actively controlling the actuation means. The stent body is substantially tubular and includes material layers covering a plurality of radial expansion trusses. The stent employs MEMS motors under the control of a programmable logic device to expand the trusses and the stent body. The trusses comprise a plurality of hinged links which produce symmetrical expansion of the stent body when actuated by the MEMS motor.

An endoluminal support structure or stent in accordance with certain embodiments of the invention solves certain deficiencies found in the prior art. In particular, the support structure can be repositioned within the body lumen or retrieved from the lumen.

A particular embodiment of the invention includes a support apparatus implantable within a biological lumen. The support apparatus can include a plurality of elongated strut members interlinked by a plurality of swivel joints, wherein the swivel joints can cooperate with the stent members to adjustably define a shaped structure between a compressed orientation and an expanded orientation.

More particularly, the shaped structure can be one of a cylindrical, a conical, or an hourglass shape. A swivel joint can form a scissor mechanism with a first strut member and a second strut member. Furthermore, the strut members can be arranged as a series of linked scissor mechanisms. The apparatus can further include an actuation mechanism to urge the swivel joints within a range of motion.

The apparatus can also include a prosthetic valve coupled to the shaped structure.

Another particular embodiment of the invention can include a medical stent implantable within a biological lumen. The medical stent can include a plurality of elongated strut members, including a first strut member and a second strut member, and a swivel joint connecting the first strut member and the second strut member.

In particular, the swivel joint can form a scissor mechanism with the first strut member and the second strut member. The swivel joint can bisect the first strut member and the second strut member. The swivel joint can interconnect a first end of the first strut member with a first end of the second strut member.

The plurality of strut members can be arranged as a series of linked scissor mechanisms. The strut members can also be non-linear. The strut members can be arranged to form one of a cylindrical, a conical, or an hourglass shape.

The stent can further include an adjustment mechanism to exerting a force to urge the strut members about the swivel joint within a range of motion.

The stent can include a prosthetic valve coupled to the strut members.

Specific embodiments of the invention can include prosthetic valves that are rotatable or conventional.

A rotatable prosthetic valve can include a first structural member coupled to the strut members, a second structural member rotatable relative to the first structural member, and a plurality of pliable valve members connecting the first structural member with the second structural member such that rotation of the second structural member relative to the first structural member can urge the valve members between an open and a closed state. In particular, the rotation of the second structural member can be responsive to the natural flow of a biological fluid.

A conventional prosthetic valve can include a plurality of pliable valve leaflets having commissures at the intersection of two strut members. The prosthetic valve can further include a skirt material coupled to the strut members.

A particular advantage of a support structure in accordance with embodiments of the invention is that it enables a prosthetic valve to be readily retrieved and repositioned in the body. If following deployment, the valve is mal-positioned or deemed dysfunctional, the support structure allows the valve to be readily repositioned and re-deployed at a new implant site, or removed from the body entirely. This feature of the device can prevent serious complications and save lives by enabling the repair of mal-positioned devices in the body.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of particular embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views.

Particular embodiments of the invention include endoluminal support structures (stents) and prosthetic valves.

<FIG> is a perspective view of a particular endoluminal support structure. As shown, the support structure <NUM> is a medical stent that includes a plurality of longitudinal strut members <NUM> interconnected by a plurality of swivel joints <NUM>. In particular, the swivel joints <NUM> allow the interconnected strut members <NUM> to rotate relative to each other. As shown, there are eighteen struts <NUM>.

The strut members <NUM> are fabricated from a rigid or semi-rigid biocompatible material, such as plastics or other polymers and metal alloys, including stainless steel, tantalum, titanium, nickel-titanium (e.g. Nitinol), and cobalt-chromium (e.g. ELGILOY). The dimensions of each strut can be chosen in accordance with its desired use. In a particular embodiment, each strut member is made from stainless steel, which is <NUM> - <NUM> (<NUM>-<NUM> inch) thick. More particularly, each strut is <NUM> (<NUM> inch) thick <NUM> series stainless steel. While all struts <NUM> are shown as being of uniform thickness, the thickness of a strut can vary across a strut, such as a gradual increase or decrease in thickness along the length of a strut. Furthermore, individual struts can differ in thickness from other individual struts in the same support structure.

As shown, each strut member <NUM> is bar shaped and has a front surface 11f and a back surface 11b. The strut members can however be of different geometries. For example, instead of a uniform width, the struts can vary in width along its length. Furthermore, an individual strut can have a different width than another strut in the same support structure. Similarly, the strut lengths can vary from strut to strut within the same support structure. The particular dimensions can be chosen based on the implant site.

Furthermore, the struts can be non-flat structures. In particular, the struts can include a curvature, such as in a concave or convex manner in relationship to the inner diameter of the stent structure. The struts can also be twisted. The non-flatness or flatness of the struts can be a property of the material from which they are constructed. For example, the struts can exhibit shape-memory or heat- responsive changes in shape to the struts during various states. Such states can be defined by the stent in the compressed or expanded configuration.

Furthermore, the strut members <NUM> can have a smooth or rough surface texture. In particular, a pitted surface can provide tensile strength to the struts. In addition, roughness or pitting can provide additional friction to help secure the support structure at the implant site and encourage irregular encapsulation of the support structure <NUM> by tissue growth to further stabilize the support structure <NUM> at the implant site over time.

In certain instances, the stent could be comprised of struts that are multiple members stacked upon one another. Within the same stent, some struts could include elongated members stacked upon one another in a multi-ply configuration, and other struts could be one-ply, composed of single-thickness members. Within a single strut, there can be areas of one-ply and multi-ply layering of the members.

Each strut member <NUM> also includes a plurality of orifices <NUM> spaced along the length of the strut member <NUM>. On the front surface 11f, the orifices are countersunk <NUM> to receive the head of a fastener. In a particular embodiment, there are thirteen equally spaced orifices <NUM> along the length of each strut member <NUM>, but more or less orifices can be used. The orifices <NUM> are shown as being of uniform diameter and uniform spacing along the strut member <NUM>, but neither is required.

The strut members <NUM> are arranged as a chain of four-bar linkages. The strut members <NUM> are interconnected by swivelable pivot fasteners <NUM>, such as rivets, extending through aligned orifices <NUM>. It should be understood that other swivelable fasteners <NUM> can be employed such as screws, bolts, ball-in-socket structures, nails, or eyelets, and that the fasteners can be integrally formed in the struts <NUM> such as a peened semi-sphere interacting with an indentation or orifice, or a male-female coupling. In addition to receiving a fastener, the orifices <NUM> also provide an additional pathway for tissue growth-over to stabilize and encapsulate the support structure <NUM> over time.

<FIG> is a perspective view of a four strut section of the stent of <FIG>. As shown, two outer strut members <NUM>-<NUM>, <NUM>-<NUM> overlap two inner strut members <NUM>-<NUM>, <NUM>-<NUM>, with their back surfaces in communication with each other.

In particular, the first strut member <NUM>-<NUM> is swivelably connected to the second strut member <NUM>-<NUM> by a middle swivel joint <NUM>-<NUM> using a rivet <NUM>-<NUM>, which utilizes orifices <NUM> that bisect the strut members <NUM>-<NUM>, <NUM>-<NUM>. Similarly, the third strut member <NUM>-<NUM> is swivelably connected to bisect the fourth strut member <NUM>-<NUM> by a middle swivel joint <NUM>-<NUM> using a rivet <NUM>-<NUM>. It should be understood that the middle swivel joints <NUM>-<NUM>, <NUM>-<NUM> function as a scissor joint in a scissor linkage or mechanism. As shown, the resulting scissor arms are of equal length. It should also be understood that the middle joint <NUM>-<NUM>, <NUM>-<NUM> need not bisect the joined strut members, but can instead utilize orifices <NUM> offset from the longitudinal centers of the strut members resulting in unequal scissor arm lengths.

In addition to the middle scissor joint <NUM>-<NUM>, the first strut member <NUM>-<NUM> is swivelably connected to the third strut member <NUM>-<NUM> by a distal anchor swivel joint <NUM>-<NUM>, located near the distal ends of the strut members <NUM>-<NUM>, <NUM>-<NUM>. Similarly, the first strut member <NUM>-<NUM> is swivelably connected to the fourth strut member <NUM>-<NUM> by a proximal anchor swivel joint <NUM>-<NUM>, located near the proximal ends of the strut members <NUM>-<NUM>, <NUM>-<NUM>. To reduce stresses on the anchor rivets <NUM>-<NUM>, <NUM>-<NUM>, the distal and proximal ends of the struts <NUM> can be curved or twisted to provide a flush interface between the joined struts.

As can be seen, the support structure <NUM> (<FIG>) is fabricated by linking together a serial chain of scissor mechanisms. The chain is then wrapped to join the last scissor mechanism with the first scissor mechanism in the chain. By actuating the linkage the links can be opened or closed, which results in expanding or compressing the stent <NUM> (<FIG>).

Returning to <FIG>, by utilizing the swivel joints <NUM>, the diameter of the stent can be compressed for insertion through a biological lumen, such as an artery, to a selected position. The stent can then be expanded to secure the stent at the selected location within the lumen. Furthermore, after being expanded, the stent can be recompressed for removal from the body or for repositioning within the lumen.

<FIG> is a perspective view of a compressed support structure of <FIG>. When compressed, the stent <NUM> is at its maximum length and minimum diameter. The maximum length is limited by the length of the strut members, which in a particular embodiment is <NUM>. The minimum diameter is limited by the width of the strut members, which in a particular embodiment is <NUM> (<NUM> inch).

<FIG> is a perspective view of the support structure of <FIG> in a fully expanded state. As shown, the fully expanded support structure <NUM> forms a ring, which can be used as an annuloplasty ring.

In particular, if one end of the stent circumference is attached to tissue, the compression of the stent will enable the tissue to cinch. Because the stent has the ability to have an incremental and reversible compression or expansion, the device could be used to provide an individualized cinching of the tissue to increase the competency of a heart valve. This could be a useful treatment for mitral valve diseases, such as mitral regurgitation or mitral valve prolapse.

While the support structure <NUM> can be implanted in a patient during an open operative procedure, a closed procedure will often be more desirable. As such, the support structure <NUM> can include an actuation mechanism to allow a surgeon to expand or compress the support structure from a location remote from the implant site. Due to the properties of a scissor linkage wrapped into a cylinder (<FIG>), actuation mechanisms can exert work to expand the stent diameter by either increasing the distance between neighboring scissor joints, and decreasing the distance between the anchor joints.

<FIG> is a perspective view of the support structure of <FIG> having a particular actuator mechanism. As shown, the actuator mechanism <NUM> includes a dual-threaded rod <NUM> positioned on the inside of the support structure <NUM> (<FIG>). It should be understood, however, that the actuator mechanism <NUM> can instead be positioned on the outside of the support structure <NUM>. Whether positioned on the inside or outside, the actuator mechanism <NUM> operates in the same way.

The rod includes right-hand threads 34R on its proximal end and left-hand threads <NUM> on its distal end. The rod <NUM> is mounted the anchor points <NUM>-<NUM>, <NUM>-<NUM> using a pair of threaded low-profile support mounts <NUM>-<NUM>, <NUM>-<NUM>. Each end of the rod <NUM> is terminated by a hex head <NUM>-<NUM>, <NUM>-<NUM> for receiving a hex driver (not shown). As should be understood, rotating the rod <NUM> in one direction will urge the anchor points <NUM>-<NUM>, <NUM>-<NUM> outwardly to compress the linkages while rotating the rod <NUM> in the opposite direction will urge the anchor points <NUM>-<NUM>, <NUM>-<NUM> inwardly to expand the linkages.

<FIG> is a perspective view of the support structure of <FIG> having another particular actuator mechanism. As shown, the actuator mechanism <NUM>' includes a single-threaded rod <NUM>' positioned on the inside of the support structure <NUM> (<FIG>). The rod <NUM>' includes threads <NUM>' on one of its ends. The rod <NUM>' is mounted to low-profile anchor points <NUM>-<NUM>, <NUM>-<NUM> using a pair of support mounts <NUM>'-<NUM>, <NUM>'-<NUM>, one of which is threaded to mate with the rod threads <NUM>'. The unthreaded end of the rod <NUM>' includes a retaining stop <NUM>' that bears against the support mount <NUM>'-<NUM> to compress the support structure. Each end of the rod <NUM>' is terminated by a hex head <NUM>'-<NUM>, <NUM>'-<NUM> for receiving a hex driver (not shown). Again, rotating the rod <NUM>' in one direction will urge the anchor points <NUM>-<NUM>, <NUM>-<NUM> outwardly to compress the linkages while rotating the rod <NUM>' in the opposite direction will urge the anchor points <NUM>-<NUM>, <NUM>-<NUM> inwardly to expand the linkages.

In addition, because the struts overlap, a ratcheting mechanism can be incorporated to be utilized during the sliding of one strut relative to the other. For example, the stent could lock at incremental diameters due to the interaction of features that are an integral part of each strut. An example of such features would be a male component (e.g. bumps) on one strut surface which mates with the female component (e.g. holes) on the surface of the neighboring strut surface, as the two struts slide pass one another. Such structures could be fabricated to have an orientation, such that they incrementally lock the stent in the expanded configuration as the stent is expanded. Such a stent could be expanded using a conventional balloon or other actuation mechanism described in this application.

Because the support structure <NUM> of <FIG> are intended to be implanted during a closed surgical procedure, the actuator mechanism is controlled remotely by a surgeon. In a typical procedure, the support structure <NUM> is implanted through a body lumen, such as the femoral artery using a tethered endoluminal catheter. As such, the actuator mechanism <NUM> can be controlled via the catheter.

<FIG> is a perspective view of a particular support structure and control catheter assembly usable with the actuator mechanisms of <FIG>. The control catheter <NUM> is dimensioned to be inserted with the support structure through a biological lumen, such as a human artery. As shown, the control catheter <NUM> includes a flexible drive cable <NUM> having a driver <NUM> on its distal end that removably mates with a hex head <NUM>, <NUM>' of the actuator mechanism (<FIG>). The proximal end of the cable <NUM> includes a hex head <NUM>. In operation, the proximal hex head <NUM> of the cable <NUM> is rotated by a surgeon, using a thumb wheel or other suitable manipulator (not shown). Rotation of the hex head <NUM> is transferred by the cable <NUM> to the driver head <NUM> to turn the actuator rod <NUM>, <NUM>' (<FIG>).

The cable <NUM> is encased by a flexible outer sheath <NUM>. The distal end of the outer sheath <NUM> includes a lip or protuberance <NUM> shaped to interface with the support structure <NUM>. When the cable <NUM> is turned, the outer sheath lip <NUM> interacts with the support structure <NUM> to counteract the resulting torque.

By employing threads, the rod is self-locking to maintain the support structure in the desired diameter. In a particular embodiment, the rod <NUM>, <NUM>' has a diameter of <NUM> and a thread count of <NUM> turns/inch. While a threaded rod and drive mechanism are described, other techniques can be employed to actuate the linkages depending on the particular surgical application. For example, the actuator mechanism can be disposed within the thickness of the strut members, instead of inside or outside of the stent. For example, worm gears or a rack and pinion mechanism can be employed as known in the art. One of ordinary skill in the art should recognize other endoluminal actuation techniques. In other situations, the support structure can be implanted during an open procedure, which may not require an external actuation mechanism.

Although there are other uses for the described support structure, such as drug delivery, a particular embodiment supports a prosthetic valve. In particular, the support structure is used in combination with a prosthetic valve, such as for an aortic valve replacement.

<FIG> is a perspective view of a particular rotating prosthetic valve assembly. The prosthetic valve <NUM> comprises a three leaflet configuration shown in an open position. The leaflets are derived from a biocompatible material, such as animal pericardium (e.g. bovine, porcine, equine), human pericardium, chemically-treated pericardium, gluteraldehyde-treated pericardium, tissue engineered materials, a scaffold for tissue engineered materials, autologous pericardium, cadaveric pericardium, Nitinol, polymers, plastics, PTFE, or any other material known in the art.

The leaflets 101a, 101b, 101c are attached to a stationary cylindrical member <NUM> and a non-stationary cylindrical member <NUM>. One side of each leaflet <NUM> is attached to the non-stationary cylindrical member <NUM>. The opposing side of each leaflet <NUM> is attached to the stationary cylindrical member <NUM>. The attachment of each leaflet <NUM> is in a direction generally perpendicular to the longitudinal axis of the cylindrical members <NUM>, <NUM>. In this embodiment, each leaflet <NUM> is pliable, generally rectangular in shape, and has a <NUM> degree twist between its attachments to stationary member <NUM> and non-stationary member <NUM>. Each leaflet <NUM> has an inner edge <NUM> and an outer edge <NUM>, with the edges 102c, 103c of one leaflet 101c being referenced in the figure. As known in the art, the leaflets can be fabricated from either biological or non-biological materials, or a combination of both.

One way to actuate the valve to close is by utilizing the forces exerted by the normal blood flow or pressure changes of the cardiac cycle. More specifically, the heart ejects blood through the fully open valve in the direction of the arrow shown in <FIG>. Shortly thereafter, the distal or downstream blood pressure starts to rise relative to the proximal pressure across the valve, creating a backpressure on the valve.

<FIG> is a perspective view of the valve assembly of <FIG> while being closed. That backpressure along the direction of the arrow causes the axially displacement of the leaflets <NUM> and non-stationary member <NUM> towards the stationary cylindrical member <NUM>. As the leaflets <NUM> move from a vertical to horizontal plane relative to the longitudinal axis, a net counter-clockwise torque force is exerted on the non-stationary member <NUM> and leaflets <NUM>. The torque force exerts a centripetal force on the leaflets <NUM>.

<FIG> is a perspective view of the valve assembly of <FIG> once completely closed. Complete closure of the valve <NUM> occurs as the leaflets <NUM> displace to the center of the valve and the non-stationary cylindrical member <NUM> rests upon the stationary member <NUM>, as shown.

The function of the valve <NUM> opening can be understood by observing the reverse of the steps of valve closing, namely following the sequence of drawings from FIG. <NUM> to FIG.

In considering the valve <NUM> as an aortic valve replacement, it would remain closed as shown in <FIG>, until the heart enters systole. During systole, as the myocardium forcefully contracts, the blood pressure exerted on the valve's proximal side (the side closest to the heart) is greater than the pressure on the distal side (downstream) of the closed valve. This pressure gradient causes the leaflets <NUM> and non-stationary cylindrical member <NUM> to displace away from the stationary member <NUM> along the axial plane. The valve <NUM> briefly assumes the half-closed transition state shown in <FIG>.

As the leaflets <NUM> elongate from a horizontal to vertical orientation along the axial plane, a net torque force is exerted on the leaflets <NUM> and non-stationary cylindrical member <NUM>. Since the valve <NUM> is opening, as opposed to closing, the torque force exerted to open the valve is opposite to that exerted to close the vlave. Given the configuration of embodiment shown in <FIG>, the torque force that opens the valve would be in clockwise direction.

The torque forces cause the leaflets <NUM> to rotate with the non-stationary member <NUM> around the longitudinal axis of the valve <NUM>. This, in turn, exerts a centrifugal force on each leaflet <NUM>. The leaflets <NUM> undergo radial displacement away from the center, effectively opening the valve and allowing blood to flow away from the heart, in the direction shown by the arrow in <FIG>.

To summarize, the valve passively functions to provide unidirectional blood flow by linking three forces. Axial, torque, and radial forces are translated in a sequential and reversible manner, while encoding the directionality of prior motions. First, the axial force of blood flow and pressure causes the displacement of the leaflets <NUM> and non-stationary members <NUM> relative to the stationary member <NUM> along the axial plane. This is translated into a rotational force on the leaflets <NUM> and non-stationary member <NUM>. The torque force, in turn, displaces the leaflets <NUM> towards or away from the center of the valve, along the radial plane, which closes or opens the valve <NUM>. The valve <NUM> passively follows the pathway of opening or closing, depending on the direction of the axial force initially applied to the valve by the cardiac cycle.

In the body, the stationary cylindrical member <NUM> can secured and fixed in position at the implant site, while the non-stationary member <NUM> and distal ends of leaflets <NUM> are free to displace along the axial plane. In using the prosthetic valve as an aortic valve replacement, the stationary member <NUM> would be secured in the aortic root. As the blood pressure or flow from the heart, increases, the valve <NUM> changes from its closed configuration to the open configuration, with blood ejecting through the valve <NUM>.

Specific advantages of the rotating valve of <FIG>, along with further embodiments, are described in the above-incorporated parent provisional patent application.

<FIG> is a perspective view of the valve of <FIG> in combination with the support structure of <FIG>. As shown in the closed position, the valve's stationary member <NUM> is attached to the support structure <NUM>. The valve's non-stationary member <NUM> is not attached to the support structure <NUM>. This enables the non-stationary member <NUM> to displace along the axial plane along with the leaflets <NUM> during valve opening or closing. In this particular embodiment, the valve <NUM> occupies a position that is closer to one end of the support structure <NUM>, as shown.

<FIG> is a perspective view of the valve of <FIG> in the open position. As noted above, the non-stationary member <NUM> is not attached to support structure <NUM>, and is thus free to displace along the axial plane, along with the leaflets <NUM>. In this particular embodiment, during full opening, non-stationary member <NUM> and the leaflets <NUM> remain within the confines of the support structure <NUM>.

The stented valve <NUM> can be implanted during a closed procedure as described above. However, because of the operation of the non-stationary member within the body of the stent, the actuator mechanism to compress and expand the stent would not be disposed within the stent.

Further embodiments of the stented valve <NUM>, positioning of the valve in the body, and procedures for implantation are described in the above-incorporated parent provisional patent application. In addition, a tissue valve can be draped on the support structure. Additional embodiments should be apparent to those of ordinary skill in the art.

<FIG> is a perspective view of a traditional tissue valve mounted to the support structure of <FIG>. As shown, a stented valve <NUM> includes a prosthetic tissue valve <NUM> attached to a support structure <NUM>, such as that described above.

The tissue valve <NUM> includes three pliable semi-circular leaflets 121a, 121b, 121c, which can be derived from biocompatible materials as noted with reference to <FIG>. Adjacent leaflets are attached in pairs to commissures 123x, 123y, 123z on the support structure <NUM>. In particular, the commissures 123x, 123y, 123z correspond with spaced-apart distal anchor points 13x, 13y, 13z on the support structure <NUM>. In an <NUM>-strut stent, the commissures are attached the structure <NUM> via corresponding fasteners <NUM> at every third distal anchor point.

From the commissures, the leaflet sides are connected to the adjacent diagonal struts. That is, the sides of the first leaflet 121a are sutured to the struts <NUM>-Xa and <NUM>-Za, respectively; the sides of the second leaflet 121b are sutured to the struts <NUM>-Xb and <NUM>-Yb, respectively; and the sides of the third leaflet 121c are sutured to the struts <NUM>-Yc and <NUM>-Zc, respectively. Those sutures end at the scissor pivot points on the diagonal struts.

In the configuration shown, neighboring struts <NUM> are attached to one another in a manner that creates multiple arches <NUM> at the ends of the stent. Posts for leaflet attachment, or commissures, are formed by attaching neighboring leaflet to each of the struts that define a suitable arch 128x, 128y, 128z. In the configuration shown, there are three leaflets 121a, 121b, 121c, each of which is attached to a strut along two of its opposing borders. The commissures are formed by three equi-distance arches 128x, 128y, 128z in the stent.

The angled orientation of a strut in relationship to its neighboring strut enables the leaflets 121a, 121b, 121c to be attached to the stent in an triangular configuration. This triangular configuration simulates the angled attachment of the native aortic leaflet. In the native valve this creates an anatomical structure between leaflets, known as the inter-leaflet trigone. Because the anatomical inter-leaflet trigone is believed to offer structural integrity and durability to the native aortic leaflets in humans, it is advantageous to simulate this structure in a prosthetic valve.

One method of attachment of the leaflets to the struts is to sandwich the leaflet between a mutli-ply strut. The multiple layers are then held together by sutures. Sandwiching the leaflets between the struts helps to dissipate the forces on leaflets and prevent the tearing of sutures through the leaflets.

The remaining side of each leaflet 121a, 121b, 121c is sutured annularly across the intermediate strut members as shown by a leaflet seam. The remaining open spaces between the struts are draped by a biocompatible skirt <NUM> to help seal the valve against the implant site and thus limit paravalvular leakage. As shown, the skirt <NUM> is shaped to cover those portions of the stent below and between the valve leaflets.

In more detail, the skirt <NUM> at the base of the valve is a thin layer of material that lines the stent wall. The skirt material can be pericardial tissue, polyester, PTFE, or other material or combinations of materials suitable for accepting tissue in growth, including chemically treated materials to promote tissue growth or inhibit infection. The skirt layer functions to reduce or eliminate leakage around the valve, or "paravalvular leak". To that end, there are a number of ways to attach the skirt material layer to the stent, including:.

The above list is not necessarily limiting as those of ordinary skill in the art may recognize alternative draping techniques for specific applications.

<FIG> is a perspective view of the valve structure of <FIG> having a full inner skirt. A stented valve <NUM>' includes a prosthetic tissue valve <NUM>' having three leaflets 121a', 121b', 121c'attached to a support structure <NUM>. A skirt layer <NUM>' covers the interior surface of the stent <NUM>. As such, the valve leaflets 121a', 121b', 121c' are sutured to the skirt layer <NUM>'.

<FIG> is a perspective view of the valve structure of <FIG> having a full outer skirt. A stented valve <NUM>" includes a prosthetic tissue valve <NUM>'' having three leaflets 121a", 121b", 121c" attached to a support structure <NUM>, such as that described in <FIG>. A skirt layer <NUM>'' covers the exterior surface of the stent <NUM>.

The tissue valve structures <NUM>, <NUM>', <NUM>'' can also be implanted during a closed procedure as described above. However, the actuator mechanism to compress and expand the stent would be attached to avoid the commissure points and limit damage to the skirt layer <NUM>, <NUM>', <NUM>", such as by mounting the actuator mechanism on the outer surface of the stent <NUM>.

While the above-described embodiments have featured a support structure having linear strut bars and equal length scissor arms, other geometries can be employed. The resulting shape will be other than cylindrical and can have better performance in certain applications.

<FIG> is a perspective view of the arrangement of strut members in a conical-shaped support structure configuration. In the conical structure <NUM>', the strut members <NUM> are arranged as shown in <FIG>, except that the middle scissor pivots do not bisect the struts. In particular, the middle scissor pivots (e.g. <NUM>'-<NUM>, <NUM>'-<NUM>) divide the joined strut members (e.g. <NUM>'-<NUM>, <NUM>'-<NUM> and <NUM>'-<NUM>, <NUM>'<NUM>) into unequal segments of <NUM>/<NUM> and <NUM>/<NUM> lengths. When fully assembled, the resulting support structure thus conforms to a conical shape when expanded. For illustration purposes, the stent <NUM>' is shown with a single-threaded actuator rod <NUM>' (<FIG>), but it is not a required element for this stent embodiment.

The stent <NUM>' can also assume a cone shape in its expanded configuration by imposing a convex or concave curvature to the individual strut members <NUM> that comprise the stent <NUM>'. This could be achieved by using a material with memory, such as shape-memory or temperature sensitive Nitinol.

A valve can be orientated in the cone-shaped stent <NUM>' such that the base of the valve was either in the narrower portion of the cone-shaped stent, with the non-base portion of the valve in the wider portion of the cone. Alternatively, the base of the valve can be located in the widest portion of the stent with the non-base portion of the valve in the less-wide portion of the stent.

The orientation of a cone-shaped stent <NUM>' in the body can be either towards or away from the stream of blood flow. In other body lumens (e.g. respiratory tract or gastrointestinal tract), the stent could be orientated in either direction, in relationship to the axial plane.

<FIG> is a perspective view of an hourglass-shaped support structure configuration. In this configuration, the circumference around the middle pivot points <NUM>"-<NUM>, <NUM>''-<NUM>, <NUM>"-<NUM> (the waist) is less than the circumference at either end of the stent <NUM>''. As shown, the hourglass shaped support structure <NUM>'' is achieved by reducing the number of strut members <NUM>'' to six and shortening the strut members <NUM>" in comparison to prior embodiments. As a result of the shortening, there are fewer orifices <NUM>'' per strut member <NUM>". Because of the strut number and geometry, each strut member <NUM>'' includes a twist at points <NUM>'' along there longitudinal planes. The twists provide a flush interface between joined strut <NUM>''-<NUM>.

An hourglass stent configuration could also be achieved by imposing concave or convex curvatures in individual bars <NUM>''. The curvature could be a property of the materials (e.g. shape-memory or heat-sensitive Nitinol). The curvature could be absent in the compressed stent state and appear when the stent is in its expanded state.

It should be noted that any of the above-described support structures can be extended beyond the anchor joints at either of both ends of the stent. By coupling a series of stents in an end-to-end chain fashion, additional stent lengths and geometries can be fabricated. In particular, an hourglass-shaped stent could be achieved by joining two cone-shaped stents at their narrow ends. The hourglass shape can also be modified by assembling the middle scissor pivots off center as shown in <FIG>.

Particular embodiments of the invention offer distinct advantages over the prior art, including in their structure and applications. While certain advantages are summarized below, the summary is not necessarily a complete list as there may be additional advantages.

The device allows the user to advert the serious complications that can occur during percutaneous heart valve implantation. Because the device is retrievable and re-positionable during implantation into the body, the surgeon can avoid serious complications due to valve mal-positioning or migration during implantation. Examples of these complications include occlusion of the coronary arteries, massive paravalvular leakage, or arrthymias.

The device can also decrease vascular access complications because of the device's narrow insertion profile. The device's profile is low, in part, due to its unique geometry, which allows neighboring struts in the stent to overlap during stent compression. The device's low profile is further augmented by eliminating the necessity for a balloon or a sheath. The device's narrow profile offers the advantage of widening the vascular access route options in patients. For instance, the device can enable the delivery of the prosthetic valve through an artery in the leg in a patient whom would have previously been committed to a more invasive approach through the chest wall. The device therefore aims to decrease complications associated with the use of large profile devices in patients with poor vascular access.

The tissue valve embodiments can offer improved durability by allowing for attachment of the leaflets to flexible commissural posts. The flexible posts allow dissipation of the stress and strain imposed on the leaflet by the cardiac cycle. The use of multi-ply struts enables the leaflets to be sandwiched in between the struts, which re-enforces the leaflet attachments and prevents tearing of sutures. The valve further assumes a desirable leaflet morphology, which further reduces the stress and strain on leaflets. Namely, the angled leaflet attachment to the stent is similar to the native human aortic valve's inter-leaflet trigone pattern. These properties significantly improve the longevity of percutaneous heart valve replacement therapies.

The device could reduce or eliminate arrthymia complications due to the incremental expansion or compression of the stent. The stent can employ a screw mechanism for deployment, which enables the stent to self-lock or un-lock at all radii. This enables more controlled deployment and the potential for individualizing the expansion or compression of the device in each patient. Because the expansion or compression of the device is reversible at any stage during the procedure, the surgeon can easily reverse the expansion of the device to relieve an arrythmia. In addition, if an arrythmia is detected during implantation, the device can be re-positioned to further eliminate the problem.

The device can reduce or eliminate paravalvular leak due to the device's ability to be accurately positioned, and re-positioned, if necessary. That can considerably decrease the occurance and severity of paravalular leaks.

The device eliminates balloon-related complications. The screw mechanism of deployment exploits the mechanical advantage of a screw. This provides for forceful dilation of the stent. The lever arms created by the pivoting of the struts in the scissor linkage of the stent, transmits a further expansion force to the stent. The stent is expanded without the need for a balloon. In addition, the ability of the device to be forcefully dilated reduces or eliminates the need for pre- or post-ballooning during the implantation procedure in patients.

The device has more predictable and precise positioning in the body because the difference between the height of the stent in the compressed and expanded position is small. This "reduced foreshortening" helps the surgeon to position the device in the desirable location in the body. The ability to re-position the device in the body further confers the ability to precisely position the device in each individual.

In addition to the mechanical advantages, the device enables a wider population of patients to be treated by a less invasive means for valve replacement. For example, the device enables patients with co-morbidites, whom are not candidates for open chest surgical valve replacement, to be offered a treatment option. The device's ability to assume a narrow profile also enables patients who were previously denied treatment due to poor vascular access (e.g. tortuous, calcified, or small arteries), to be offered a treatment option. The durability of the valve should expand the use of less-invasive procedures to the population of otherwise healthy patients, whom would otherwise be candidates for open chest surgical valve replacement. The device's ability to be forcefully expanded, or assume hourglass, or conical shapes, potentially expands the device application to the treatment of patients diagnosed with aortic insufficiency, as well as aortic stenosis.

The device can also provide a less invasive treatment to patients with degenerative prosthesis from a prior implant, by providing for a "valve-in-valve" procedure. The device could be accurately positioned inside the failing valve, without removing the patient's degenerative prosthesis. It would help the patient by providing a functional valve replacement, without a "re-do" operation and its associated risks.

Claim 1:
An endoluminal support structure or stent, comprising:
a frame comprising a first opening, a second opening, and a longitudinal axis therebetween, and comprising a plurality of elongated strut members (<NUM>) interlinked by a plurality of swivel joints (<NUM>), wherein the swivel joints (<NUM>) comprise a rotation axis perpendicular to the longitudinal axis of the frame and cooperate with the strut members (<NUM>) to adjustably define a shaped structure between a compressed orientation and an expanded orientation, wherein each swivel joint (<NUM>) forms a scissor mechanism with a first strut member (<NUM>-<NUM>) and a second strut member (<NUM>-<NUM>), wherein the strut members (<NUM>) are arranged as a serial chain of linked scissor mechanisms, wherein the last scissor mechanism is joined to the first scissor mechanism in the chain; and
an actuation mechanism comprising a rod (<NUM>), a first support mount (<NUM>-<NUM>) configured to couple the rod (<NUM>) to the frame at a first anchor point (<NUM>-<NUM>) and a second support mount (<NUM>-<NUM>) configured to couple the rod (<NUM>) to the frame at a second anchor point (<NUM>-<NUM>);
wherein the first support mount (<NUM>-<NUM>) comprises a first threaded mount, the rod (<NUM>) comprises a first helical thread, and the first threaded mount is configured to cooperate with the first helical thread;
wherein the actuation mechanism is configured such that rotation of the rod (<NUM>) in a first direction urges the anchor points (<NUM>-<NUM>, <NUM>-<NUM>) outwardly to actuate collapse of the frame to the compressed orientation, and rotation of the rod (<NUM>) in a second direction opposite to the first direction urges the anchor points (<NUM>-<NUM>, <NUM>-<NUM>) inwardly to actuate expansion of the frame to the expanded orientation;
wherein the actuation mechanism is self-locking to maintain the frame at a desired diameter; and
wherein the endoluminal support structure or stent is configured to be implanted into a biological lumen.