Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Heart valve – Flexible leaflet
Reexamination Certificate
2001-03-23
2004-05-11
Snow, Bruce (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Heart valve
Flexible leaflet
C623S002140, C623S002170, C623S002180, C623S001240, C623S900000
Reexamination Certificate
active
06733525
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to medical devices and particularly to expandable heart valve prostheses especially for use in minimally-invasive surgeries.
BACKGROUND OF THE INVENTION
Prosthetic heart valves are used to replace damaged or diseased heart valves. In vertebrate animals, the heart is a hollow muscular organ having four pumping chambers: the left and right atria and the left and right ventricles, each provided with its own one-way valve. The natural heart valves are identified as the aortic, mitral (or bicuspid), tricuspid and pulmonary valves. Prosthetic heart valves can be used to replace any of these naturally occurring valves, although repair or replacement of the aortic or mitral valves is most common because they reside in the left side of the heart where pressures are the greatest.
Where replacement of a heart valve is indicated, the dysfunctional valve is typically cut out and replaced with either a mechanical valve, or a tissue valve. Tissue valves are often preferred over mechanical valves because they typically do not require long-term treatment with anticoagulants. The most common tissue valves are constructed with whole porcine (pig) valves, or with separate leaflets cut from bovine (cow) pericardium. Although so-called stentless valves, comprising a section of porcine aorta along with the valve, are available, the most widely used valves include some form of stent or synthetic leaflet support. Typically, a wireform having alternating arcuate cusps and upstanding commissures supports the leaflets within the valve, in combination with an annular stent and a sewing ring. The alternating cusps and commissures mimic the natural contour of leaflet attachment. Importantly, the wireform provides continuous support for each leaflet along the cusp region so as to better simulate the natural support structure.
A conventional heart valve replacement surgery involves accessing the heart in the patient's thoracic cavity through a longitudinal incision in the chest. For example, a median sternotomy requires cutting through the sternum and forcing the two opposing halves of the rib cage to be spread apart, allowing access to the thoracic cavity and heart within. The patient is then placed on cardiopulmonary bypass which involves stopping the heart to permit access to the internal chambers. Such open heart surgery is particularly invasive and involves a lengthy and difficult recovery period.
Some attempts have been made to enable less traumatic delivery and implantation of prosthetic heart valves. For instance, U.S. Pat. No. 4,056,854 to Boretos discloses a radially collapsible heart valve secured to a circular spring stent that can be compressed for delivery and expanded for securing in a valve position. Also, U.S. Pat. No. 4,994,077 to Dobbin describes a disk-shaped heart valve that is connected to a radially collapsible stent for minimally invasive implantation,
Recently, a great amount of research has been done to reduce the trauma and risk associated with conventional open heart valve replacement surgery. In particular, the field of minimally invasive surgery (MIS) has exploded since the early to mid-1990s, with devices now being available to enable valve replacements without opening the chest cavity. MIS heart valve replacement surgery still typically requires bypass, but the excision of the native valve and implantation of the prosthetic valve are accomplished via elongated tubes or cannulas, with the help of endoscopes and other such visualization techniques.
Some examples of more recent MIS heart valves are shown in U.S. Pat. No. 5,411,552 to Anderson, et al., U.S. Pat. No. 5,980,570 to Simpson, U.S. Pat. No. 5,984,959 to Robertson, et al., PCT Publication No. 00/047139 to Garrison, et al., and PCT Publication No. WO 99/334142 to Vesely. Although these and other such devices provide various ways for collapsing, delivering, and then expanding a “heart valve” per se, none of them disclose an optimum structure for tissue valves. For instance, the publication to Vesely shows a tissue leaflet structure of the prior art in
FIG. 1
, and an expandable inner frame of the invention having stent posts in
FIGS. 3A-3C
. The leaflets are “mounted to the stent posts
22
in a manner similar to that shown in FIG.
1
.” Such general disclosures as in Vesely stop short of explaining how to construct a valve in a manner that maximizes long-term efficacy. In particular, the means of attaching the leaflets to the MIS stent is critical to ensure the integrity and durability of the valve once implanted. All of the prior art MIS valves are inadequate in this regard.
Another problem with MIS valves of the prior art is their relatively large radial dimension during implantation. That is, these valves all utilize one or more radially-expanding stents coupled to a biological valve, and the assembly must be compressed radially and then passed through the lumen of a large bore catheter. Reducing the radial profile of the constricted valve via radial compression is problematic and conflicts with the need for sufficient circumferential length of the valve in its expanded state to fit within an adult heart valve annulus. Moreover, radial compression of the stent and biological valve must be done with great care so as not to damage the valve.
Some MIS valves of the prior art are intended to be used without removing the natural valve leaflets. Sometimes the natural leaflets are heavily calcified, and their removal entails some risk of plaque particles being released in the bloodstream. Therefore some of the MIS valves are designed to expand outward within the annulus and native leaflets, and compress the leaflets against the annulus. In doing so, a relatively uneven surface against which the valve is expanded outward is created. This irregularity creates sizing problems, and also may adversely affect the circularity of the expanded valve which negatively affects the valve efficacy by impairing leaflet coaptation.
Despite some advances in MIS valve design, there remains a need for a valve that can be constricted into a smaller package without damaging the biological valve within, and which can be reliably expanded generally into a tube against the relatively uneven surface of the annulus or annulus and intact native leaflets.
SUMMARY OF THE INVENTION
The present invention provides an expandable prosthetic heart valve for placement in a host heart valve annulus, comprising a stent body that is rolled into a compact configuration, implanted, then unrolled into a tubular shape and secured into place in the valve annulus. The valve is small enough in its contracted state to be passed down a delivery tube, thus avoiding the need for open heart surgery. Flexible membranes attach around large apertures in the inner wall of the stent body and have sufficient play to billow inward into contact with one another and form the one-way valve occluding surfaces. The stent may be one or two pieces, and the delivery and implantation may occur in one or two steps using one or two delivery tubes.
In a preferred embodiment, a prosthetic heart valve of the present invention suitable for minimally invasive delivery comprises a generally sheet-like stent body and a plurality of flexible, biocompatible membranes incorporated into the stent body to form heart valve leaflets. The stent body has a first, contracted configuration in which it is spirally-wound about an axis such that at least one winding of the stent body surrounds another winding. The stent body further has a second, expanded configuration in which it is substantially unwound and at least partly forms a tube centered about the axis and sized to engage an annulus of a patient's heart valve. In accordance with one aspect, the stent body comprises a primary stent coupled to a secondary stent that at least partially fits within the primary stent. The flexible, biocompatible membranes are incorporated into the secondary stent. Alternatively, the stent body is formed of a single stent.
The stent body may have a plura
Pease Matthew L.
Walsh Brandon G.
Yang Ji-bin
Cumberbatch Guy L.
Edwards Lifesciences Corporation
James John Christopher
Miller Cheryl
Snow Bruce
LandOfFree
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