Site News  |   Monitor Keywords  |   Monitor Archive  |   Organizer  |   Account Info  |

Endoprosthesis structures having supporting features

Endoprosthesis structures having supporting features description/claims

This application claims the benefit of provisional application 60/885,700 (Attorney Docket No. 022265-000500US), filed on Jan. 19, 2007, the full disclosure of which is incorporated herein by reference.

1. Field of the Invention

The present invention relates to endoprosthesis designs, in particular biodegradable and non-biodegradable stents and grafts, which are adapted to be implanted into a patient's body lumen, such as coronary artery or other blood vessel or body lumen. Stents are particularly useful in the treatment of atherosclerotic stenosis in arteries and veins.

Stents are generally tubular-shaped devices which function to hold open or reinforce a segment of a blood vessel or other body lumen such as a coronary artery, carotid artery, saphenous vein graft, or femoral artery. They also are suitable to support and hold back a dissected arterial lining that can occlude the fluid passageway, to stabilize plaque, or to support bioprosthetic valves. Stents can be formed from various materials, particularly polymeric and/or metallic materials, and may be non-degradable, biodegradable, or be formed from both degradable and non-degradable components. Stents are typically delivered to the target area within the body lumen using a catheter. With balloon-expandable stents, the stent is mounted to a balloon catheter, navigated to the appropriate area, and the stent expanded by inflating the balloon. A self-expanding stent is delivered to the target area and released, expanding to the required diameter to treat the disease. Stents may also elute various drugs and pharmacological agents.

Referring to FIG. 1, a common pattern employed in present cardiovascular stents comprises a plurality of serpentine rings 12 joined by short axial links 14. The serpentine rings comprise axial struts 16, where circumferentially adjacent struts are connected by crowns 18 which act as hinges in permitting circumferential expansion of the individual rings 12. These patterns can be used for both degradable and non-degradable stents and other endoprostheses.

In the design of stents and other endoprostheses, a number of competing objectives must be addressed. For coronary artery stents, it is usually desirable to be able to collapse the stent to minimize the cross-sectional area for delivery while maximizing the surface area of the stent after expansion. A maximized surface area provides both enhanced wall support to reduce vessel recoil and a greater capacity to deliver drugs when employing drug-coated stents. A further design objective is to allow the stent to be compressed with a minimum force while still maintaining a good hoop strength after expansion to further resist vessel recoil.

Thus, what is needed is a stent design or stent material which enhances radial or hoop strength, reduces vessel recoil after implantation, provides an increased surface area while maintaining or reducing the size and mass of the stent. The present invention meets at least some of these requirements.

2. Description of the Background Art

U.S. Pat. No. 6,773,455 describes a stent having serpentine rings axially connected via internal expansion elements. US 2003/0093143 describes a stent comprising box structures joined circumferentially by U-shaped connectors. US2003/0144729 describes a stent comprising axially spaced serpentine bands connected by wishbone connectors. See also U.S. Pat. No. 7,291,166 and U.S. Pat. No. 6,896,695.

The present invention provides an endoprosthesis, such as a stent, graft or other scaffold-like luminal prosthesis, that is used for treating vascular and other luminal conditions. The endoprosthesis includes supporting features or elements added to a base structure. The base structure of the stent is formed from a series of circumferential serpentine rings connected directly to each other or with at least one link or strut, generally as shown in FIG. 1 discussed above, where each ring comprises multiple expansion segments constructed from crowns and struts. In accordance with the present invention, the base structure is reinforced with supporting features which can increase radial strength and/or reduce recoil upon expansion of the stent compared to the structure without the supporting features. The supporting features can contain varying types of shapes such as an I-shape, C-shape, V-shape, U-shape, S-shape, Y-shape, M-shape, W-shape, Z-shape, spiral-shape or other types. In a first embodiment, the supporting features connect at least some of the adjacent struts. In another embodiment at least one supporting feature connects to at least one axially connecting link.

Thus, according to the present invention, an endoprosthesis comprises a plurality of circumferentially expandable serpentine rings, axial links joining the adjacent rings, and supporting features. The circumferentially expandable serpentine rings each include axial struts joined by crowns, where the crowns act as hinges allowing the struts to spread as the ring opens circumferentially. The axial links join the adjacent serpentine rings by connecting at least some of the crowns on the rings. The supporting features extend between at least some of the adjacent struts of at least some of the serpentine rings, where the supporting features elongate and the struts remain substantially undeformed as the ring circumferentially expands.

The endoprosthesis may be constructed from a variety of conventional stent materials and may be either balloon-expandable, self-expanding, or a combination of both. The serpentine rings of the self-expanding endoprostheses will be sufficiently elastic so that they can be constrained in a small cross-sectional area during delivery and released within the vasculature or other body lumens to assume a circumferentially expanded configuration. In contrast, the serpentine rings of the balloon-expandable endoprostheses will be sufficiently malleable so that they can be circumferentially expanded by applying a radially outward force from within the rings, typically using an inflatable balloon or other expandable structure. Particularly preferred stent materials include metals and alloys such as iron, zinc, steel, cobalt-chromium, nickel-titanium, as well as polymers such as poly lactides, polycaprolactone, polyethylene carbonate, copolymers of polylactide-glycolide, poly lactide-trimethylenecarbonates, and the like. Particular materials and fabrication methods are described in commonly owned application Ser. No. 11/______ (Attorney Docket No. 022265-000520US), filed on the same day as the present application.

The supporting features may have a variety of specific configurations or patterns which are selected to elongate or otherwise expand as the serpentine rings of the endoprosthesis are expanded. Exemplary supporting feature configurations include U-shaped connectors, V-shaped connectors, S-shaped connectors, spiral-shaped connectors, W-shaped connectors, N-shaped connectors, Z-shaped connectors, and the like. In order to increase or control the exposed surface area of the endoprosthesis, the supporting structures may have variable widths, for example the spiral-shaped connectors may include ring or disk-shaped cores to enhance or control the surface area. While the width and cross-sectional area of the supporting feature will usually be less than the width and cross-sectional area of the serpentine rings so that expansion of the supporting features does not deform or deflect the main ring structure, it will be possible to increase the area of the supporting feature by providing deflection points which allow the supporting feature to yield preferentially relative to the serpentine rings. For example, portions of the supporting feature may be notched so that they yield first as the endoprosthesis is expanded.

In some embodiments, one or more additional supporting features may be disposed between at least some of the adjacent struts. When a single supporting feature is employed, it will usually extend generally between the mid-points on the adjacent struts, but in other instances could be disposed closer to the ends of the struts which are not connected together with a crown. In cases where two or more supporting features are provided between adjacent pairs of struts, they may be located at any point along the length of the strut, typically with one being located near the midpoint and another being located near the free ends (i.e., ends which are not joined together with the crown).

The axial links will usually comprise short linear beams, where the linear beams are axially aligned with the axis of the endoprosthesis. In other cases, the linear beams may be aligned at a shallow angle relative to the axis, typically from zero degrees to 45 degrees.

Endoprostheses according to the present invention may comprise a plurality of circumferentially expandable serpentine rings joined by axial links, where the supporting features extend between at least some adjacent axial links between adjacent serpentine rings. These supporting features between the adjacent axial links elongate as the rings circumferentially expand. Exemplary supporting features which are connected between the adjacent axial links include serpentine connectors, usually where folded portions of the connectors extend into the region between adjacent axial struts. Alternatively, the connectors could comprise “box” connectors having symmetric extending lengths which project into the regions between axial struts.

• Provisional Patent
• Utility Patent

• What Is a Patent?
• What Is a Trademark or Servicemark?
• What Is a Copyright?
• Patent Laws