Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Heart valve – Flexible leaflet
Reexamination Certificate
2000-04-06
2002-09-24
McDermott, Corrine (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Heart valve
Flexible leaflet
C623S002100, C623S002140, C623S002170, C623S002280, C623S002330
Reexamination Certificate
active
06454799
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.
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 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 MIS heart valves are shown in U.S. Pat. No. 5,980,570 to Simpson, U S. Pat. No. 5,984,959 to Robertson, 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 a general disclosure stops short of explaining how to construct an optimum valve. 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 fall short in this regard.
In view of the foregoing, it is evident that an improved sewing ring that addresses the apparent deficiencies in existing expandable heart valves is necessary and desired.
SUMMARY OF THE INVENTION
The present invention provides an expandable prosthetic heart valve for placement in a host heart valve annulus, comprising an expandable stent system adapted to be delivered in a collapsed state to an implantation site and expanded, and a plurality of prosthetic leaflets attached to the stent system. Each leaflet has an approximately semi-circular cusp edge terminating at each end in commissure portions, and a coapting edge extending between the commissure portions. Each leaflet is attached to the stent system substantially entirely along the cusp edge and at both commissure portions, with a coapting edge remaining unattached. The stent system may comprise an expandable generally annular tissue-engaging base and an elastic generally annular wireform attached thereto. The base is adapted to be delivered in a radially collapsed state and expanded into contact with the host annulus. The annular wireform defines a plurality of upstanding commissures and a plurality of arcuate cusps between adjacent commissures, and the prosthetic leaflets are attached to the wireform along the cusps and commissures, wherein the wireform and leaflets are configured to be radially compressed.
In one embodiment, the heart valve includes a plurality of upstanding posts attached to one of the tissue-engaging base and elastic wireform, each post having a connector. A plurality of mating connectors are provided on the other of the tissue-engaging base and elastic wireform for mating with the post connectors. The posts and mating connectors may be provided for each commissure and each cusp of the elastic wireform so that the valve includes a number of posts and mating connectors equal to the number of commissures plus the number of cusps. Further, the expandable stent system may include an undulating wireform defining a plurality of commissures and a plurality of cusps between adjacent commissures. The cusp edge of each of the prosthetic leaflets attaches along a wireform cusp, and the commissure portions of each leaflet terminate in outwardly extending tabs that each attach to a wireform commissure, wherein tabs from adjacent leaflets are attached together at each of the wireform commissures.
In another aspect of the invention, an expandable prosthetic heart valve for placement in a host heart valve annulus is provided. The heart valve comprises an expandable stent portion and an elastic leaflet portion connectable to the stent portion. The stent portion defines an inflow end of the valve and is adapted to be delivered in a collapsed state and expanded into contact with the host annulus. The leaflet portion forms a one-way flow occluder on an outflow end of the valve and includes an elastic wireform defining alternating cusps and commissures and prosthetic tissue attached substantially entirely therealong. The stent portion desirably includes a tubular member and a plurality of connectors, and wherein a plurality of connectors are provided on the elastic wireform for mating with the tubular member connectors. The wireform connectors may be provided on each commissure and on each cusp of the wireform so that the valve includes a number of mating connectors equal to the number of commissures plus the number of cusps. In a preferred embodiment, the prosthetic tissue comprises a plurality of individual leaflets secured along the alternating cusps and commissures of the elastic wireform. Additionally, the wireform may have a fabric covering, wherein the individual leaflets are stitched along the fabric covering. The fabric covering continues toward an inflow end of the valve in a skirt that surrounds the stent portion and is adapted to be captured between the expanded stent portion and the host annulus. A plurality of posts rigidly may connect to the stent portion and extend upward within the skirt into mating connection with the elastic wireform.
In a still f
Condino Debra D.
Cumberbatch Guy L.
Edwards Lifesciences Corporation
James John Christopher
McDermott Corrine
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