Stent for the positioning and anchoring of a valvular prosthesis in an implantation site in the heart of a patient
A device configured for implantation at a heart valve comprises an expandable stent. The stent comprises a first stent segment extending along a first length portion of the stent. The first stent segment is configured to be positioned and radially expanded against a vascular wall of a native aortic valve site. The first stent segment comprises a plurality of closed cell structures defining a circumference of the stent along the first length portion. The plurality of closed cell structures has a uniform density around the circumference. The stent also comprises a second stent segment disposed along a second length portion of the stent. The second stent segment comprises a plurality of interconnected strut members disposed around a circumference of the stent in alternating regions having a first strut density and a second strut density. The first strut density is higher than the second strut density.
1. A device configured for implantation at a heart valve, the device comprising:
an expandable stent comprising:
a first stent segment extending along a first length portion of the stent, the first stent segment configured to be positioned and radially expanded against a vascular wall of a native aortic valve site, the first stent segment comprising a plurality of closed cell structures defining a circumference of the stent along the first length portion, the plurality of closed cell structures having a uniform density around the circumference; and
a second stent segment disposed along a second length portion of the stent, the second stent segment comprising a first plurality of interconnected strut members having a first strut density and a second plurality of interconnected strut members having a second strut density, the first and second plurality of interconnected strut members being disposed in alternating regions around a circumference of the stent, the first strut density being higher than the second strut density,
wherein, in an implanted position of the stent at the heart valve, regions of the alternating regions having the first strut density are configured to be aligned with respective commissures of the heart valve and regions of the alternating regions having the second strut density are configured to be aligned with respective cusps of the heart valve.
2. The device of claim 1 , further comprising:
a valve prosthesis comprising a plurality of prosthetic valve leaflets attached to the expandable stent;
wherein:
the regions of the alternating regions of the second stent segment having the first strut density are located on an inflow side of the valve prosthesis, and
the regions of the alternating regions of the second stent segment having the second strut density are located on an outflow side of the valve prosthesis.
3. The device of claim 1 , wherein the first stent segment includes an inflow end of the stent when the stent is in an implanted position at the heart valve.
4. The device of claim 3 , wherein the inflow end of the stent is configured to expand radially more than an oppositely disposed, outflow end of the stent.
5. The device of claim 4 , wherein the inflow end of the stent is configured to expand to a diameter ranging from about 22 mm to about 33 mm.
6. The device of claim 4 , wherein the stent has a concave outer surface tapering toward the outflow end of the stent.
7. The device of claim 3 , wherein, in an expanded configuration of the stent, the first stent segment is more rigid than the second stent segment.
8. The device of claim 3 , wherein, in an implanted position of the stent at the heart valve:
the first stent segment is configured to provide a first outward radial force against a vascular wall,
the second stent segment is configured to provide a second outward radial force against a vascular wall, and
the first outward radial force is greater than the second outward radial force.
9. The device of claim 8 , wherein, in the implanted position of the stent at the heart valve, the uniform density of the plurality of closed cell structures of the first stent segment is configured to uniformly distribute the first outward radial force along the vascular wall.
10. The device of claim 1 , wherein the first stent segment comprises a plurality of axially stacked rows of closed cell structures.
11. The device of claim 1 , wherein the regions of the alternating regions having the first strut density are configured to minimize blood leakage when the stent is in an implanted position at the heart valve.
12. The device of claim 1 , wherein the regions of the alternating regions having the second strut density each comprise:
a positioning arch extending along the second length portion of the stent, the positioning arch terminating in an apex facing in a direction toward the first length portion of the stent; and
a retaining arch circumferentially aligned with and substantially enclosing the positioning arch.
13. The device of claim 12 , wherein the apex of each positioning arch terminates at an axial location along the stent where the second stent segment meets the first stent segment.
14. The device of claim 12 , wherein end sections of the strut members forming the regions of the alternating regions having the first strut density are connected to respective arms of the retaining arches.
15. The device of claim 14 , wherein the end sections have a larger diameter than the rest of the strut members forming the regions of the alternating regions having the first strut density.
16. The device of claim 1 , wherein the alternating regions of the second stent segment comprise three regions having the first strut density and three regions having the second strut density.