Patent Application
20100256723
The invention relates generally to a prosthetic valve for replacing a native or previously implanted prosthetic valve in a non-surgical interventional procedure. More particularly, the invention relates to a prosthetic heart valve having a stent structure that is restricted or otherwise prevented from overexpansion when deployed in vivo.
A wide range of medical treatments are known that utilize “endoluminal prostheses.” As used herein, endoluminal prostheses are intended to mean medical devices that are adapted for temporary or permanent implantation within a body lumen, including both naturally occurring and artificially made lumens. Examples of lumens in which endoluminal prostheses may be implanted include, without limitation: arteries, veins, gastrointestinal tract, biliary tract, urethra, trachea, hepatic and cerebral shunts, and fallopian tubes.
Stent prostheses are known for implantation within a body lumen for providing artificial radial support to the wall tissue that defines the body lumen. To provide radial support to a blood vessel, such as one that has been widened by a percutaneous transluminal coronary angioplasty, commonly referred to as “angioplasty,” “PTA” or “PTCA”, a stent may be implanted in conjunction with the procedure. Under this procedure, the stent may be collapsed to an insertion diameter and inserted into the vasculature at a site remote from the diseased vessel. The stent may then be delivered to the desired treatment site within the affected vessel and deployed, by self-expansion or radial expansion, to its desired diameter for treatment.
Recently, flexible prosthetic valves supported by stent structures that can be delivered percutaneously using a catheter-based delivery system have been developed for heart and venous valve replacement. These prosthetic valves may include either self-expanding or balloon-expandable stent structures with valve leaflets disposed within the interior of the stent structure. The prosthetic valve can be reduced in diameter, by being contained within a sheath component of a delivery catheter or by crimping onto a balloon catheter, and advanced through the venous or arterial vasculature. Once the prosthetic valve is positioned at the treatment site, for instance within an incompetent native or previously implanted prosthetic valve, the stent structure may be expanded to hold the prosthetic valve firmly in place. One embodiment of a prosthetic valve having a stent structure is disclosed in U.S. Pat. No. 5,957,949 to Leonhardt et al. entitled “Percutaneous Placement Valve Stent”, which is incorporated by reference herein in its entirety.
Valvular heart disease is any disease process involving one or more of the valves of the heart, i.e., the aortic and mitral valves on the left and the pulmonary and tricuspid valves on the right. When a prosthetic valve is percutaneously delivered to replace a stenotic or insufficient heart valve, a fundamental concern is that the prosthesis be deployed as precisely as possible so as to assure proper functioning and avoid paravalvular leakage. In addition, the deployed prosthetic heart valve must be properly sized so as not to interfere with operation of the heart. For instance if the prosthetic heart valve includes a self-expanding stent-like support structure that has an expanded diameter that is either over-sized for the valve annulus in which it has been deployed and/or that continues to “grow” after implantation, the support structure of the prosthesis may exert an undesirable radial force upon the surrounding heart tissue during and/or after initial expansion. The application of such a radial force on the surrounding heart tissue by the self-expanding stent structure may inadvertently interfere with the electrical conduction system of the heart so as to cause heart block, which may cause lightheadedness, syncope (fainting), and/or palpitations in the patient. As such, a prosthetic heart valve having a stent structure that is prevented from being oversized upon deployment and from continued expansion in vivo may be a desirable addition to the art.
Embodiments hereof are directed to a prosthetic valve having a stent structure with a prosthetic valve component secured therein that includes a device for restricting expansion, i.e., an expansion restrictor device, disposed at a blood inflow end of the stent structure. The expansion restrictor device defines a deployed diameter of the stent structure to prevent the prosthetic valve from being over-sized upon initial deployment and/or from continued expansion in vivo. The expansion restrictor device may be a loop of suture or other thread-like structure having a loop diameter that is less than or substantially equal to a diameter of the treatment site in which the prosthetic valve is to be deployed in vivo. In an embodiment, the looped suture may be pre-knotted so that the knot may be tightened in vivo to secure a final diameter of the loop. In another embodiment, the looped suture may be tied to a preset diameter prior to introduction into the vasculature. In various embodiments hereof, the stent structure may be either self-expanding or balloon-expandable.
The foregoing and other features and advantages of the invention will be apparent from the following description of embodiments hereof as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and form a part of the specification, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. The drawings are not to scale.
Specific embodiments of the present invention are now described with reference to the figures, wherein like reference numbers indicate identical or functionally similar elements. The terms “distal” and “proximal” are used in the following description with respect to a position or direction relative to the treating clinician. “Distal” or “distally” are a position distant from or in a direction away from the clinician. “Proximal” and “proximally” are a position near or in a direction toward the clinician. However, when discussing positions of the delivery system and/or the prosthetic valve within the aorta proximate the heart, the terms “distal” and “proximal” are used in the following description with respect to the heart. More particularly, “distal” or “distally” are a position away from the heart and “proximal” or “proximally” are a position near or closer to the heart
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Although the description of embodiments hereof is in the context of heart valve replacement, the invention may also be used for valve replacement in other body passageways where it is deemed useful. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.
A prosthetic valve 100 in accordance with an embodiment hereof is shown and described with reference to
Valve leaflets 104′ of prosthetic valve component 104 may be of a synthetic material, a xenograft natural tissue and/or a homograft natural tissue and, as shown in
Self-expanding stent structure 102 is a tubular structure, and in the embodiment of
In order to prevent self-expanding stent structure 102 of prosthetic valve 100 from being oversized upon deployment and/or from continuing to expand after deployment, an expansion restrictor device 120 encircles a circumference of prosthetic valve 100 proximate distal end 108. In an embodiment, expansion restrictor device 120 may be a suture or other thread-like structure that has been weaved through adjacent connectors 112 and knotted to form a loop that constrains or defines a deployed diameter of self-expanding stent structure 102. The looped suture is knotted in such a fashion that permits tightening of the knot after deployment. In such an embodiment after self-expanding stent 102 has been delivered to the treatment site and allowed to reach an expanded diameter in vivo, a knot puller/pusher device may be used to tighten the knot and secure the looped suture to a final diameter that fixes the deployed diameter of self-expanding stent structure 102. Knot puller/pusher devices as shown and described in U.S. Pat. No. 5,423,837 to Mericle et al, U.S. Pat. No. 5,693,061 to Pierce et al., U.S. Pat. No. 5,752,964 to Mericle, U.S. Pat. No. 6,511,488 to Marshall et al., and U.S. Pat. No. 7,270,672 to Singer, which are incorporated by reference herein in their entirety, may be adapted for use in embodiments hereof. In this manner, self-expanding stent structure 102 is indefinitely held at the deployed diameter and prevented from continued expansion after deployment, which avoids adversely affecting surrounding bodily structures that may be sensitive to radial pressure exerted by stent structure 102.
In embodiments hereof, expansion restrictor device 120 may be a pre-tied loop of suture, flexible line, thread or cord of a set diameter that constrains or defines a deployed diameter of self-expanding stent structure 102. In such an embodiment prior to delivery of prosthetic valve 100 to a treatment site, such as the aortic annulus when prosthetic valve 100 is a replacement aortic heart valve, a diameter of the treatment site/aortic annulus is measured via ultrasound, a CT scan or fluoroscopy and a suture, flexible line, thread or cord of a length suitable to be tied to a preset diameter that is at or slightly below the treatment site diameter is weaved around or otherwise secured to stent structure 102 and tied to form a loop with the preset diameter. Upon deployment of prosthetic valve 100 at the treatment site, the pre-tied loop of suture, flexible line, thread or cord will than fix or hold the deployed diameter of stent structure 102 at or slightly below the treatment site diameter to prevent prosthetic valve 100 from being over-sized and/or from continued expansion after deployment.
In an exemplary embodiment that represents the function of expansion restrictor devices according to embodiments hereof, self-expanding stent structure 102 may have an expanded diameter of 26 mm, for e.g., that is constrained to a deployed diameter of 25 mm, for e.g., at a blood inflow end thereof by expansion restrictor device 120. Expansion restrictor device 120 does not constrain expansion of the entire stent structure 102, such that a second deployed diameter larger than the deployed diameter of stent structure 102 at expansion restrictor device 120 occurs at least at a blood outflow end of stent structure 102. In an embodiment, the second deployed diameter may be substantially equal to the expanded diameter of self-expanding stent structure 102. Expansion restrictor device 120 continues to constrain/fix the deployed diameter of the blood inflow end of self-expanding structure 102 after initial deployment to prevent the stent structure from growing or creeping to or beyond its expanded diameter.
Prosthetic valve 100 is disposed within the native aortic valve with proximal end 106, viz., the blood flow outlet, positioned in apposition with the displaced native aortic valve leaflets and with distal end 108, viz., the blood flow inlet, concentrically disposed within the aortic annulus but spaced therefrom by expansion restrictor device 120, which constrains the deployed diameter of self-expanding stent structure 102 at distal end 108 to be less than a diameter of the opposing portion of the aortic annulus. Thus as shown in
In the embodiment of
In the embodiment of
In order to prevent self-expanding stent structure 402, and more particularly tubular base portion 418, of prosthetic valve 400 from being oversized upon initial deployment and/or from continuing to expand in vivo after deployment, an expansion restrictor device 420 encircles a circumference of prosthetic valve 400 proximate distal end 408. In the embodiment of
Prosthetic valve 400 is disposed within the native aortic valve with tubular base portion 418 positioned in apposition with the displaced native aortic valve leaflets and with distal end 408, viz., the blood flow inlet, concentrically disposed within the aortic annulus but spaced therefrom by expansion restrictor device 420, which constrains the deployed diameter of self-expanding stent structure 402 at distal end 408 to be less than a diameter of the opposing portion of the aortic annulus. In another embodiment, distal end 408 of prosthetic valve 400 may be sized by expansion restrictor device 420 to have a deployed diameter that permits contact between an outer surface of tubular base portion 418 of self-expanding stent structure 402 and the opposing portion of the aortic annulus without exerting a radial force thereon.
In each of the preceding embodiments, a suture, flexible line, thread or cord for use as an expansion restrictor device may be an elongate flexible filament of biocompatible material having sufficient strength to aid in setting the deployed diameter of the stent structure. In one embodiment, such an expansion restrictor device is a monofilament. In various other embodiments, such an expansion restrictor may be a braid of a plurality of filaments of the same or different materials. In still other embodiments, such an expansion restrictor may include a braided sheath with a single filament core, or a braided sheath with a braided core. A suture, flexible line, thread or cord for use as an expansion restrictor is constructed from a material with good tensile strength that will not stretch and/or may be pre-stressed to prevent stretching or elongation during use. Suitable biocompatible materials for such expansion restrictors include but are not limited to silk, nylon, polyethylene, and polyester, as well as other high strength materials conventionally used for sutures. In an embodiment, such expansion restrictors may include one or more pre-stretched filaments of an ultra high molecular weight polyethylene, such as a filament made from DYNEEMA fibers. Various embodiments hereof include expansion restrictors of one or more sutures, flexible lines, threads or cords having diameters in the range of 0.015 inches and 0.050 inches. However, depending on the application, one or more sutures, flexible lines, threads or cords having diameters smaller than 0.015 inches or larger than 0.050 inches may be used. Although not shown in each embodiment, expansion restrictor devices 120, 320, 420 may include one or more loops of suture, flexible line, thread or cord, which may be spaced apart as shown in the embodiment of
It will be appreciated by one of ordinary skill in the art that the stent structures shown in the preceding embodiments are merely exemplary in nature and that either self-expanding or balloon-expandable stents of various forms may be adapted for use in accordance with the teaching hereof. Some examples of stent configurations that are suitable for use in embodiments hereof are shown in U.S. Pat. No. 4,733,665 to Palmaz, U.S. Pat. No. 4,800,882 to Gianturco, U.S. Pat. No. 4,886,062 to Wiktor, U.S. Pat. No. 5,133,732 to Wiktor, U.S. Pat. No. 5,292,331 to Boneau, U.S. Pat. No. 5,421,955 to Lau, U.S. Pat. No. 5,776,161 to Globerman, U.S. Pat. No. 5,935,162 to Dang, U.S. Pat. No. 6,090,127 to Globerman, U.S. Pat. No. 6,113,627 to Jang, U.S. Pat. No. 6,663,661 to Boneau, and U.S. Pat. No. 6,730,116 to Wolinsky et al., each of which is incorporated by reference herein in its entirety.
While various embodiments according to the present invention have been described above, it should be understood that they have been presented by way of illustration and example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the appended claims and their equivalents. It will also be understood that each feature of each embodiment discussed herein, and of each reference cited herein, can be used in combination with the features of any other embodiment. All patents and publications discussed herein are incorporated by reference herein in their entirety.
