Patent Description:
Diseased and/or defective heart valves may lead to serious health complications. One method of addressing this condition is to replace a non-functioning heart valve with a prosthetic valve. Prosthetic heart valves that are collapsible to a relatively small circumferential size can be delivered into a patient less invasively than valves that are not collapsible. For example, a collapsible valve may be delivered into a patient via a tube-like delivery apparatus such as a catheter, a trocar, a laparoscopic instrument, or the like. This collapsibility can avoid the need for a more invasive procedure such as full open-chest, open-heart surgery.

Collapsible prosthetic heart valves typically take the form of a valve structure mounted on a stent. There are two types of stents on which the valve structures are ordinarily mounted: a self-expanding stent and a balloon-expandable stent. To place such valves into a delivery apparatus and ultimately into a patient, the valve must first be collapsed or crimped to reduce its circumferential size.

When a collapsed prosthetic valve has reached the desired implant site in the patient (e.g., at or near the annulus of the patient's heart valve that is to be replaced by the prosthetic valve), the prosthetic valve can be deployed or released from the delivery apparatus and re-expanded to full operating size. For balloon-expandable valves, this generally involves releasing the entire valve, assuring its proper location, and then expanding a balloon positioned within the valve stent. For self-expanding valves, on the other hand, the stent automatically expands as the sheath covering the valve is withdrawn.

<CIT> describes a device for placing in a cardiac valve to assist operation of natural cardiac valve leaflets, the device including a frame for anchoring the device, configured to be placed upstream of the cardiac annulus and shaped to prevent the frame from shifting downstream of the cardiac valve annulus, and at least one anchor extension attached to the frame, the anchor extension configured to extend through the leaflets of the cardiac valve at commissures of the cardiac valve and behind the natural leaflets, preventing the anchor extensions from shifting back from the downstream side of the annulus to the upstream side of the annulus.

<CIT> describes prosthetic heart valve devices for percutaneous replacement of native heart valves. A prosthetic heart valve device can include an expandable support having an outer surface and configured for placement between leaflets of the native valve. The device can also include a plurality of asymmetrically arranged arms coupled to the expandable support and configured to receive the leaflets of the native valve between the arms and the outer surface. The arms can include tip portions for engaging a subannular surface of the native valve.

<CIT> discloses that a valve prosthesis includes an expandable frame comprising an outflow portion and an inflow portion connected to the outflow portion.

<CIT> discloses that a prosthetic heart valve may include a stent having an inflow end an outflow end, a collapsed condition, and an expanded condition.

Prior art document <CIT> discloses a prosthetic heart valve with an outflow portion and an inflow portion and where when the frame is in the fully expanded configuration, an outer surface of the inflow portion is concave.

The invention relates to a prosthetic heart valve and is defined by appended claim <NUM>.

Various embodiments of the present disclosure are disclosed herein with reference to the drawings, wherein:.

Various embodiments of the present disclosure will now be described with reference to the appended drawings. It is to be appreciated that these drawings depict only some embodiments of the disclosure and are therefore not to be considered limiting of its scope.

In conventional collapsible prosthetic heart valves, the stent is usually anchored within the native valve annulus via radial forces exerted by the expanding stent against the native valve annulus. If the radial force is too high, damage may occur to heart tissue. If, instead, the radial force is too low, the heart valve may move from its implanted position, for example, into the left ventricle. Because such anchoring partly depends on the presence of calcification or plaque in the native valve annulus, it may be difficult to properly anchor the valve in locations where plaque is lacking (e.g., the mitral valve annulus). Additionally, in certain situations it may be preferable to restore native valve leaflet function instead of implanting a prosthetic device to replace that function.

In view of the foregoing, there is a need for further improvements to the devices, systems, and methods for replacing the function of a native heart valve, such as a mitral valve, a tricuspid valve, an aortic valve, or a pulmonary valve. Among other advantages, the present disclosure may address one or more of these needs. While many of the examples are described herein with reference to a specific valve (e.g., a mitral valve or a tricuspid valve), it will be understood that many of the examples are not so limited and that the concepts described apply equally to other heart valves unless expressly limited herein.

Blood flows through the mitral valve from the left atrium to the left ventricle. As used herein, the term "inflow," when used in connection with a prosthetic mitral heart valve, refers to the end of the heart valve closest to the left atrium when the heart valve is implanted in a patient, whereas the term "outflow," when used in connection with a prosthetic mitral heart valve, refers to the end of the heart valve closest to the left ventricle when the heart valve is implanted in a patient. When used in connection with a prosthetic aortic valve, "inflow" refers to the end closest to the left ventricle and "outflow" refers to the end closest to the aorta. The same convention is applicable for other valves wherein "inflow" and "outflow" are defined by the direction of blood flow therethrough. Also, as used herein, the words "substantially," "approximately," "generally" and "about" are intended to mean that slight variations from absolute are included within the scope of the structure or process recited.

<FIG> is a schematic representation of a human heart <NUM>. The human heart includes two atria and two ventricles: a right atrium <NUM> and a left atrium <NUM>, and a right ventricle <NUM> and a left ventricle <NUM>. As illustrated in <FIG>, the heart <NUM> further includes an aorta <NUM>, and an aortic arch <NUM>. Disposed between the left atrium and the left ventricle is the mitral valve <NUM>. The mitral valve <NUM>, also known as the bicuspid valve or left atrioventricular valve, is a dual-flap that opens as a result of increased pressure in the left atrium as it fills with blood. As atrial pressure increases above that of the left ventricle, the mitral valve opens and blood passes toward the left ventricle. Blood flows through heart <NUM> in the direction shown by arrows "B".

A dashed arrow, labeled "TA", indicates a transapical approach for repairing or replacing heart valves, such as a mitral valve. In transapical delivery, a small incision is made between the ribs and into the apex of the left ventricle <NUM> at position "P1" in heart wall <NUM> to deliver a prosthesis or device to the target site.

<FIG> is a more detailed schematic representation of a native mitral valve <NUM> and its associated structures. Mitral valve <NUM> includes two flaps or leaflets, a posterior leaflet <NUM> and an anterior leaflet <NUM>, disposed between left atrium <NUM> and left ventricle <NUM>. Cord-like tendons known as chordae tendineae <NUM> connect the two leaflets <NUM>, <NUM> to the medial and lateral papillary muscles <NUM>. During atrial systole, blood flows from the left atrium to the left ventricle down the pressure gradient. When the left ventricle contracts in ventricular systole, the increased blood pressure in the chamber pushes the mitral valve to close, preventing backflow of blood into the left atrium. Since the blood pressure in the left atrium is much lower than that in the left ventricle, the flaps attempt to evert to the low pressure regions. The chordae tendineae prevent the eversion by becoming tense, thus pulling the flaps and holding them in the closed position.

<FIG> is a schematic representation of mitral valve prolapse as discussed above. Posterior leaflet <NUM> has prolapsed into left atrium <NUM>. Moreover, certain chordae tendineae have stretched and others have ruptured. Because of damaged chordae 134a, even if posterior leaflet <NUM> returns to its intended position, it will eventually resume the prolapsed position due to being inadequately secured. Thus, mitral valve <NUM> is incapable of functioning properly and blood is allowed to return to the left atrium and the lungs. It will be understood that, in addition to chordae damage, other abnormalities or failures may be responsible for mitral valve insufficiency.

<FIG> is a longitudinal cross-section of prosthetic heart valve <NUM> in accordance with one embodiment of the present disclosure. Prosthetic heart valve <NUM> is a collapsible prosthetic heart valve designed to replace the function of the native mitral valve of a patient (see native mitral valve <NUM> of <FIG>). Generally, prosthetic valve <NUM> has inflow end <NUM> and outflow end <NUM>. Prosthetic valve <NUM> may be substantially cylindrically shaped and may include features for anchoring, as will be discussed in more detail below. When used to replace native mitral valve <NUM>, prosthetic valve <NUM> may have a low profile so as not to interfere with atrial function.

Prosthetic heart valve <NUM> includes stent <NUM>, which may be formed from biocompatible materials that are capable of self-expansion, such as, for example, shape memory alloys including nitinol. Alternatively, stent <NUM> may be formed of a material suitable for balloon-expansion. Stent <NUM> may include a plurality of struts <NUM> that form cells <NUM> connected to one another in one or more annular rows around the stent. Cells <NUM> may all be of substantially the same size around the perimeter and along the length of stent <NUM>. Alternatively, cells <NUM> near inflow end <NUM> may be larger than the cells near outflow end <NUM>. Stent <NUM> may be expandable to provide a radial force to assist with positioning and stabilizing prosthetic heart valve <NUM> within the native mitral valve annulus.

Prosthetic heart valve <NUM> may also include valve assembly <NUM>, including a pair of leaflets <NUM> attached to a cylindrical cuff <NUM>. Leaflets <NUM> replace the function of native mitral valve leaflets <NUM> and <NUM> described above with reference to <FIG>. That is, leaflets <NUM> coapt with one another to function as a one-way valve. It will be appreciated, however, that prosthetic heart valve <NUM> may have more than two leaflets when used to replace a mitral valve or other cardiac valves within a patient. Valve assembly <NUM> of prosthetic heart valve <NUM> may be substantially cylindrical, or may taper outwardly from outflow end <NUM> to inflow end <NUM>. Both cuff <NUM> and leaflets <NUM> may be wholly or partly formed of any suitable biological material, such as bovine or porcine pericardium, or polymers, such as PTFE, urethanes and the like.

When used to replace a native mitral valve, valve assembly <NUM> may be sized in the range of about <NUM> to about <NUM> in diameter. Valve assembly <NUM> may be secured to stent <NUM> by suturing to struts <NUM> or by using tissue glue, ultrasonic welding or other suitable methods.

An optional frame <NUM> may surround and house valve assembly <NUM> and stent <NUM>. Frame <NUM> may be formed of a braided material in various configurations to create shapes and/or geometries for engaging tissue and filling the spaces between valve assembly <NUM> and the native valve annulus. As shown in <FIG>, frame <NUM> includes a plurality of braided strands or wires <NUM> arranged in three-dimensional shapes. In one example, wires <NUM> form a braided metal fabric that is both resilient and capable of heat treatment substantially to a desired preset shape. One class of materials which meets these qualifications is shape memory alloys. One example of a suitable shape memory alloy is Nitinol. It is also contemplated that wires <NUM> may comprise various materials other than Nitinol that have elastic and/or memory properties, such as spring stainless steel, alloys such as Elgiloy®, Hastelloy®, and MP35N®, CoCrNi alloys (e.g., trade name Phynox), CoCrMo alloys, or a mixture of metal and polymer fibers. Depending on the individual material selected, the strand diameter, number of strands, and pitch may be altered to achieve desired properties for frame <NUM>.

In the simplest configuration of frame <NUM>, shown in <FIG>, frame <NUM> may be formed in a cylindrical or tubular configuration having inlet end <NUM>, outlet end <NUM> and lumen <NUM> extending between inlet end <NUM> and outlet end <NUM> for housing stent <NUM> and valve assembly <NUM>. However, in certain embodiments stent <NUM> may be omitted, and valve assembly <NUM> may be directly attached to frame <NUM> using any of the techniques described above for attaching valve assembly <NUM> to stent <NUM>. Frame <NUM> may be radially collapsed from a relaxed or preset configuration to a compressed or reduced configuration for delivery into the patient. Once released after delivery, the shape-memory properties of frame <NUM> may cause it to re-expand to its relaxed or preset configuration. Frame <NUM> may also be locally compliant in a radial direction such that a force exerted in the direction of arrow F deforms a portion of the frame. In this manner, irregularities in the native valve annulus may be filled by frame <NUM>, thereby preventing paravalvular leakage. Moreover, portions of frame <NUM> may endothelialize and in-grow into the heart wall over time, providing permanent stability and a low thrombus surface.

<FIG> illustrates one variation in which prosthetic heart valve <NUM> includes additional features to aid in fixing the valve at a predetermined location within the native valve annulus. Prosthetic heart valve <NUM> generally extends between inflow end <NUM> and outflow end <NUM> and includes all of the elements disclosed above including stent <NUM> formed of struts <NUM>, valve assembly <NUM> having leaflets <NUM> and cuff <NUM>. Stent <NUM> may be substantially cylindrical and may further include flared portion <NUM> adjacent inflow end <NUM> that projects radially outward from the cylindrical stent to anchor the stent at a predetermined location in the native valve annulus. Flared portion <NUM> forms an angle α with the longitudinal axis of stent <NUM>. In some examples, angle α may be between about <NUM> degrees and about <NUM> degrees. In some examples, angle α may be between about <NUM> and <NUM> degrees. Moreover, as shown in <FIG>, flared portion <NUM> may be curved. Thus, flared portion <NUM> may have an initial takeoff angle α and then round out along its length to form a second angle β with the longitudinal axis of stent <NUM> near its distal end. As a result of the rounding, second angle β may between about <NUM> degrees and about <NUM> degrees. During delivery, flared portion <NUM> may be compressed against the outside of collapsed stent <NUM> within a sheath of a delivery device and may return to its flared configuration when released from the sheath. When prosthetic heart valve <NUM> is used to replace the function of a native mitral valve, flared portion <NUM> may be disposed at least partially within the left atrium. Details of flared portion <NUM> are explored further below with reference to <FIG>.

<FIG> is a developed view of a stent 500A suitable for use in a mitral heart valve prosthesis. Stent 500A generally extends in a length direction between inflow end <NUM> and outflow end <NUM> and includes a plurality of struts <NUM> forming rows of cells 510A, 520A, 530A, and a plurality of commissure features <NUM>. First row of cells 510A is disposed adjacent outflow end <NUM> and includes symmetric cells <NUM>, typically disposed adjacent commissure features <NUM>, and asymmetric cells <NUM> at selected positions within first row 510A. Symmetric cells <NUM> may be substantially diamond-shaped and include four substantially straight struts 506a-d of substantially equal length. According to the invention, asymmetric cells <NUM> include a pair of substantially straight struts 515a,515b which form a V-shape attached to substantially curved struts 516a,516b. Nested within selected ones of asymmetric cells <NUM> are engaging arms <NUM>, which extend generally from the connection of one cell <NUM> to the adjacent cells in either side thereof in row 510A, and which have a curved shape which generally follows the curved shape of struts 516a, 516b. Engaging arms <NUM> may be configured to engage portions of heart tissue by contacting, clasping, gripping, securing or otherwise preventing, minimizing or limiting the motion of stent 500A (e.g., native mitral valve leaflets) when the stent is deployed in a patient as part of a prosthetic heart valve. Second row of cells 520A may include a plurality of cells <NUM> formed by two struts shared with cells from first row 510A (e.g., struts 506c, 506d, 516a, 516b) and two substantially straight struts 526a, 526b. A third row of cells 530A includes enlarged cells <NUM> formed of struts 536a-d, each of which is longer than struts 506a-d. Third row 530A may include cells that have a length L1 that is greater than the lengths of other cells. In at least some examples, length L1 may be between about <NUM> and about <NUM>. Third row 530A of enlarged cells <NUM> may be configured to form a diameter greater than the diameter formed by the first two rows. Thus, as shown in the cross-sectional schematic of <FIG>, when stent 500A fully expands, third row 530A of enlarged cells <NUM> forms a flared portion. Optionally, a number of retainers <NUM> may be disposed on selected enlarged cells <NUM> as well as on commissure features <NUM> to help hold stent 500A in the delivery apparatus and aid in its deployment.

As shown in <FIG>, stent 500A is formed of three rows of cells, each row having nine cells and is thus referred to as a nine-cell configuration. As briefly discussed, engaging arms <NUM> are nested within selected asymmetric cells <NUM> to engage the native valve leaflets. Because the native mitral valve includes two native leaflets, the illustrated example includes two engaging arms <NUM> for mating with each native valve leaflet, the first pair of engaging arms being spaced apart from the second pair of engaging arms so that they are approximately contralateral to one another. It will be understood, however, that in a nine-cell stent configuration, it may be difficult to provide pairs of engaging arms that are exactly <NUM> degrees apart from one another.

<FIG> shows a variation in which stent 500B has a twelve-cell configuration (i.e., each row of cells in stent 500B includes twelve cells). Stent 500B extends between inflow end <NUM> and outflow end <NUM> and includes a first row of cells 510B having symmetric cells <NUM> and asymmetric cells <NUM>, a second row of cells 520B having cells <NUM> and a third row of cells 530B having enlarged cells <NUM>. Engaging arms <NUM> are nested within two pairs of asymmetric cells 514a, 514b and 514c, 514d each pair of asymmetric cells being spaced from one another by a symmetric cell. In this example, pairs of engaging arms <NUM> are offset from one another as much as possible, and provide a generally more symmetric configuration than stent 500A, which allow for simpler coupling of the belly and leaflets. Thus, the positioning of the engaging arms may be affected by the number of cells in rows of a stent.

As shown in <FIG>, a cuff <NUM> may be disposed over a portion of stent 500A. As illustrated, cuff <NUM> includes three separate segments 610a-c that are disposed over portions of the first and second rows of cells 510A, 520A and joined together at seams <NUM>. By using a cuff formed of three segments, greater flexibility is provided for making finer adjustments to facilitate the assembly process. <FIG> illustrates cuff segment 610a in greater detail, cuff segments 610B and 610c being substantially the same. As shown, cuff segment 610a includes a first portion <NUM> sized to be disposed over commissure feature <NUM>, a second portion <NUM> for covering symmetric cell <NUM> of first row 510A, and three substantially equal third portions <NUM>,<NUM>,<NUM> for covering three cells <NUM> of second row 520A. It will be understood that cuff <NUM> may be disposed on either the luminal or the abluminal surface of stent 500A and that the shape of the cuff may be modified as needed for a stent having a twelve-cell configuration. Additionally, a unitary cuff may be used instead of the three-segmented example shown. When disposed on the abluminal surface of stent 500A, cuff segment 610a may be configured to allow engaging arms <NUM> to extend therethrough to reach and couple to the native valve leaflets. Thus, engaging arms <NUM> are preferably unobstructed by cuff <NUM>.

In another variation shown in <FIG>, cuff <NUM> may be disposed over a portion of stent 500A. As illustrated, cuff <NUM> includes three separate segments 710a-c that are disposed over portions of the first and second rows 510A,520A and joined together at seams <NUM>. The differences between cuff <NUM> and cuff <NUM> described above are more readily identifiable by looking at the detailed view of <FIG>. As shown, cuff segment 710a includes a first portion <NUM> sized to be disposed over commissure feature <NUM>. Second portion <NUM> covers symmetric cell <NUM> of first row 510A and includes two additional peaks <NUM> for covering asymmetric cells <NUM>. A third portion <NUM> covers cells <NUM> of second row 520A and has a substantially straight edge <NUM> that runs horizontally across the lower corners of cells <NUM>. Cuff <NUM> is shaped to allow engaging arms <NUM> to extend over the cuff and couple to the native valve leaflets. Cuff segments 710b and 710c may have the same configuration as cuff segment 710a.

In addition to the cuff, a skirt may be disposed over the third row of cells 530A,530B to cover flared portion <NUM> of the stent. <FIG> illustrates one example of a skirt 800A configured to cover the third row of cells in a twelve-cell stent configuration (e.g., stent 500B of <FIG>). For the sake of clarity, skirt 800A will be described as having multiple portions or components. It will be understood, however, that the skirt may be formed of a single piece of tissue, fabric or polymeric material cut into a predetermined shape and that the portions or components described herein are only indicated for the sake of description and may not be readily discernible from the whole.

As shown, skirt 800A generally includes a hub <NUM> having a number of sides <NUM>. Hub <NUM> is shown in the shape of a dodecagon in order to complement a twelve-celled stent. A circular cutout <NUM> is formed in the center of hub <NUM> to form void <NUM> for accepting a portion of the stent. In at least some examples, cutout <NUM> is formed having a circumference approximately equal to the circumference of a fully expanded stent at the second row of cells. A plurality of quadrilateral tabs <NUM> extend from the sides of hub <NUM>. In the case of a dodecagon hub, twelve quadrilateral tabs <NUM> are formed around the perimeter of the hub, one extending from each side <NUM> of hub <NUM>.

Due to the desired increasing diameter of flared portion <NUM> of the stent, triangular slits <NUM> are provided between quadrilateral tabs <NUM>. However, when fully assembled to the stent, edges 811a,811b of adjacent quadrilateral tabs 810a, 810b will be sewn or otherwise coupled together to close slits <NUM>. <FIG> are photographs illustrating the assembly of a mock skirt 800B having nine quadrilateral tabs <NUM> to a stent having nine cells in each row. For the sake of clarity, the valve assembly including the cuff and the leaflets is not shown. Quadrilateral tabs <NUM> are coupled to one another at seams <NUM> to form a continuous surface. It will be understood that quadrilateral tabs <NUM> may be formed such that seams <NUM> align with struts of stent 500A as shown.

Instead of being formed as a single piece of material, a skirt may be formed in multiple segments. As seen in <FIG>, skirt <NUM> is formed of three equal segments 901A-C. As shown in <FIG>, each segment 901A-C may include a fraction of a hub, such as portion 902A defining an arc <NUM>. Each portion 901A-C may also include a number of quadrilateral tabs 910a-d extending from portion 902A. It will be understood that each of segments 901A-C may be formed to be substantially the same size and may include the same number of quadrilateral tabs. An optional coupling <NUM> may be added to each of segments 910A-C and configured to overlap with an adjacent segment to add integrity to the assembly. It will be understood that variations are possible by changing the size and/or shape of the segments. For example, segments 901D, one of which is shown in <FIG>, may be formed to complement a stent of nine cells per row by having only three quadrilateral tabs 910e-g each.

In another variation, shown in <FIG>, skirt <NUM> includes more slits to reduce puckering at the seams. Similar to skirt 800A, skirt <NUM> includes a hub <NUM> having circular cutout <NUM> at its center to form void <NUM> for accepting a portion of the stent. Extending from hub <NUM> and disposed on its perimeter are a series of alternating wedges including first wedges <NUM> and second wedges <NUM>. In the examples shown, first wedges <NUM> are substantially triangular and are attached at an edge of the triangle to hub <NUM>, and second wedges <NUM> are substantially triangular and are attached to hub <NUM> at a point of the triangle. Collectively, wedges <NUM> and <NUM> define a series of triangles that alternate in their connection to hub <NUM>. Each first wedge <NUM> is disposed between adjacent second wedges <NUM> and spaced from the second wedges by slits 1030a, 1030b. When fully assembled, edges of first and second wedges <NUM>, <NUM> adjoin to one another to provide a continuous layer over a row of cells forming a flared portion <NUM>. It will be understood, however, that the shapes of first and second wedges <NUM>, <NUM> may be varied from the shapes shown and described herein and that skirt <NUM> may, for example, include a series of wedges in the shape of triangles instead of concave quadrilaterals that are arranged so that each triangle is inverted with respect to an adjacent triangle.

<FIG> illustrates one possible suture pattern for attaching a skirt, such as skirt 800A, to stent 500A having cuff <NUM>. A first suture pattern S1 may be formed across the tops of cells <NUM> in third row of cells 530A at inflow end <NUM> of stent 500A, and around the circumference of the stent to attach skirt 800A to the stent. A second suture pattern S2 may be formed parallel to the first suture pattern S1 and across the ends of cells <NUM>, <NUM> in first row of cells 510A and approximately halfway through cells <NUM> in second row of cells 520A. A third suture pattern S3 may consist of a zigzag pattern along the upper half of enlarged cells <NUM> of third row of cells 530A, and a fourth suture pattern S4 may form a second zigzag pattern along the lower half of enlarged cells <NUM>, the fourth suture pattern S4 being a mirror image of the third suture pattern S3.

A fully assembled prosthetic heart valve <NUM> is shown in <FIG> and includes stent 500A having inflow end <NUM> and outflow end <NUM>. Inflow and outflow end views of prosthetic heart valve <NUM> are shown in <FIG>, respectively. Cuff <NUM> is disposed on a portion of stent 500A adjacent outflow end <NUM> and skirt 800A is disposed on the flared portion <NUM> of stent 500A adjacent inflow end <NUM>, as described above with reference to <FIG>. Additionally, three leaflets <NUM> have been added to the interior of stent 500A and attached to commissure features <NUM> and to selected struts of stent 500A and/or cuff <NUM> to form a valve assembly as known in the art. Engaging arms <NUM> may also extend toward inflow end <NUM> and clip onto, or otherwise couple to, native valve leaflets to aid in anchoring stent 500A to the surrounding tissue. Though cuff <NUM> covers many cells of stent 500A, engaging arms <NUM> remain unobstructed to adequately perform their function. When deployed at the mitral valve position, prosthetic heart valve <NUM> allows flow of blood from atrium <NUM> to left ventricle <NUM> and impedes blood backflow from left ventricle <NUM> to left atrium <NUM>. Flared portion <NUM> may be disposed at least partially within the native valve annulus and/or left atrium <NUM> to anchor prosthetic heart valve <NUM> (e.g., reduce the possibility of prosthetic heart valve <NUM> migrating into left ventricle <NUM>) and/or seal regions around prosthetic heart valve <NUM> to reduce paravalvular leakage.

Several variations of the stent for a prosthetic heart valve are possible. For example, <FIG> illustrates stent <NUM> extending generally between inflow end <NUM> and outflow end <NUM> and having three rows of cells <NUM>,<NUM>,<NUM>, similar to the cells of stent 500A described above with reference to <FIG>. As shown, each row includes nine cells. The main difference between stent 500A and stent <NUM> is the inclusion of horseshoes <NUM>,<NUM> to aid in suturing stent <NUM> to a cuff and a skirt. Specifically, corners C1 of cells <NUM> closest to inflow end <NUM> include first horseshoes <NUM> to prevent slippage of sutures when coupling stent <NUM> to a cuff, and corners C2 of enlarged cells <NUM> closest to inflow end <NUM> include second horseshoes <NUM> to prevent slippage of sutures when coupling stent <NUM> to a skirt.

The shape of the engaging arms may also be modified in several ways. In the simplest configuration, not falling under the scope of the claims and shown in <FIG>, stent 1400A includes a first row 1410A of cells 1412A. Each substantially diamond-shaped cell 1412A is composed of four struts 1416a-d joined to one another as shown, struts 1416a and 1416b forming an angle β1 therebetween. Nested engaging arms 1418A are formed of two substantially straight struts <NUM> that are coupled to struts 1416c and 1416d at first ends r1 and to each other at second ends r2. Because of the shape of cells 1412A there is little room to form engaging arms 1418A resulting in a sharp tip at second ends r2 and a tight angle at first ends r1.

Instead of laser cutting a tube to create a stent in a collapsed state, the tube may be laser cut to create a stent in a partially expanded state. Cutting a stent from a larger diameter tube provides a larger area inside the cells of the stent to form engaging arms. Stent 1400B of <FIG> has been formed using this method and generally includes first row of cells 1410B having first cells 1411B and second cells 1412B, second cells 1412B being formed of struts 1417a-d. First cells 1411B that will not receive engaging arms may be substantially diamond-shaped, while second cells 1412B that receive engaging arms have a second shape that does not form a diamond. Specifically, struts 1417a and 1417b of cell 1412B may form a slight curvature such that the upper portion of cell 1412B is rounded and forms an angle β2, larger than angle β1, for receiving engaging arms. With the larger angle β2, an engaging arm may be formed with a curved loop <NUM> having a smooth surface at position r2 that would be less traumatic if brought in contact with body tissue. Additionally, curved loop <NUM> includes a wider takeoff at position r1 to reduce or eliminate a pinch point, resulting in less of a stress concentration on the anatomy that is contacted and easier loading within a delivery device.

As described in the previous examples, engaging arms are not disposed within each cell of first row 1410B. Thus, in forming a stent having engaging arms, the various features of stent 1400B may be cut from a metal tube under different conditions. For example, cells 1411B that do not have engaging arms 1418B may be cut when the tube is in a radially collapsed condition, and cells that include engaging arms 1418B may be cut when the tube is in a partially expanded condition. This approach avoids the need for cutting stent 1400B out of a large tube as the large tube can be expensive and more difficult to manufacture. Selectively cutting portions in the collapsed and partially expanded conditions allows for manufacturing the configurations as shown out of a relatively small diameter of tubing.

Claim 1:
A prosthetic heart valve (<NUM>) having an inflow end (<NUM>, <NUM>) and an outflow end (<NUM>, <NUM>), comprising:
a collapsible and expandable stent (500A, 500B, <NUM>) including a plurality of cells arranged in rows (510A, 520A, 530A, 510B, 520B, 530B, <NUM>, <NUM>, <NUM>), the rows comprising a first row, each of the rows extending around a circumference of the stent (500A, 500B, <NUM>), at least one of the rows (530A, 530B, <NUM>) forming a flared portion (<NUM>) having a diameter that is larger than diameters of others of the rows (510A, 520A, 510B, 520B, <NUM>, <NUM>); and
a collapsible and expandable valve assembly (<NUM>) disposed within the stent (500A, 500B, <NUM>), the valve assembly having a plurality of leaflets (<NUM>),
characterized in that the first row (510A, 510B, <NUM>) is disposed adjacent the outflow end (<NUM>, <NUM>) and includes symmetric cells (<NUM>) and asymmetric cells (<NUM>), the asymmetric cells (<NUM>) include a pair of substantially straight struts (515A, 515B) which form a V-shape attached to substantially curved struts (516A, 516B), and where engaging arms (<NUM>, 1418A, 1418B, <NUM>) extend toward the inflow end, the engaging arms (<NUM>, 1418A, 1418B, <NUM>) are nested within select ones of the asymmetric cells, the engaging arms (<NUM>, 1418A, 1418B, <NUM>) being arranged to couple to heart tissue to anchor the stent (500A, 500B, <NUM>),
each engaging arm being nested within an asymmetric cell, the engaging arms extending from the connection of a first cell to adjacent cells of the first cell on either side of the first cell in the first row, the engaging arms having a curved shape that follows the shape of the curved struts (516A, 516B).