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Patent Issued for Expandable Stent That Collapses into a Non-Convex Shape and Expands into an Expanded, Convex Shape

May 5, 2014



By a News Reporter-Staff News Editor at Cardiovascular Week -- A patent by the inventors Kheradvar, Arash (Irvine, CA); Gharib, Morteza (Altadena, CA), filed on April 7, 2011, was published online on April 22, 2014, according to news reporting originating from Alexandria, Virginia, by NewsRx correspondents (see also California Institute of Technology).

Patent number 8702788 is assigned to California Institute of Technology (Pasadena, CA).

The following quote was obtained by the news editors from the background information supplied by the inventors: "(1) Field of Invention

"The present invention relates to an expandable stent and, more particularly, to an expandable stent that collapses into a non-convex shape and expands into a convex shape.

"(2) Description of Related Art

"Stents have been devised for a variety of purposes. For example, stents are often formed as coronary stents or used in cardiac valve prostheses for implantation into the human body. Previously, the large diameter and bulky structure of common prosthetic valves required implementation via open heart surgeries. During the past few years, percutaneous heart valve (PHV) replacement and repair has emerged as an additional therapy to potentially avoid the re-operation in young patients with congenital heart disease or severely sick patients. The challenge in PHV technology is to develop a collapsible and durable PHV that can be delivered through a reasonably small diameter lumen catheter, non-interfering with the normal anatomy, and being competent without significant valve stenosis.

"For example, a fully formed valve which is deliverable via a catheter is disclosed in U.S. Pat. No. 6,582,462 to Andersen et al. (the '462 patent), the entire contents of which are incorporated herein by reference. The '462 patent discloses a fully formed valve prosthesis comprising a collapsible elastic valve mounted on an elastic stent. The commissural points of the elastic collapsible valve are mounted on the cylindrical surface of the elastic stent. A catheter technique permits delivery of the fully formed valve to the target area without the need for surgical intervention in the body. Once at the target site, the collapsed and fully-formed valve and elastic stent are expanded. A disadvantage to this design is the relatively large size of the compressed radial diameter of the fully formed valve and corresponding stent when delivered to the target area.

"Another example is U.S. Pat. No. 6,530,952 to Vesely (the '952 patent), the entire contents of which are incorporated herein by reference. The '952 patent discloses a cardiovascular valve system including a permanent base unit that is affixed to the patient using conventional sutures or staples, and a collapsible valve having a collapsible frame that mates with the permanent base unit, and supports valve leaflets. An installed collapsible frame may be re-collapsed and disengaged from the permanent housing whereas a new collapsible valve is then installed, to resume the function of the prosthesis. As was the case above, a drawback to the device of the '952 patent is that, although collapsed, the valve and corresponding stent have a relatively large, radial diameter.

"Another example can be found in U.S. Pat. No. 7,803,168 to Gifford (the '168 patent), the entire contents of which are incorporated herein by reference. The '168 patent teaches a device for decalcifying an aortic valve. The device breaks up calcific deposits in and around the aortic valve through application or removal of heat energy from the calcific deposits. In doing so, the device includes an implantable structure with a balloon. To expand to the structure, the balloon is inflated. Again, the structure includes a relatively large, radial diameter which can create some difficulties in some patients.

"The examples provided above illustrate various devices that expand upon arrival at the expansion point within the heart or other desired location. While operable for percutaneous insertion or other uses, the examples require stents having a relatively large, radial diameter.

"Another example can be found in U.S. Pat. No. 7,175,656 to Khairkhahan (the '656 patent), the entire contents of which are incorporated herein by reference. The '656 patent teaches a different form of a valve replacement in which additional stent deployment mechanisms are obviated. As described in the '656 patent, the stent mechanism can be formed of a framework of resilient metals, such as superelastic shape memory alloys. Thus, once deployed to the appropriate location, the material of the stent itself causes its expansion into the requisite shape. While the '656 patent teaches use of a superelastic shape memory alloy, it still requires a stent with a relatively large, radial diameter.

"Each of the prior art designs has certain disadvantages. However, they all share the common disadvantage in that the stents possess a radial diameter that is undesirable.

"Thus, a continuing need exists for a deployable stent which has a minimal radial profile to increase the efficacy of reaching the desired deployment location and minimize the risk to a patient."

In addition to the background information obtained for this patent, NewsRx journalists also obtained the inventors' summary information for this patent: "The present invention relates to an expandable construct (e.g., stent) that can transform between a collapsed state and an expanded state. The stent includes a first cross-sectional shape and a second cross-sectional shape. The first cross-sectional shape is a non-convex shape when the stent is in the collapsed state. Alternatively, the second cross-sectional shape is a convex shape when the stent is in an expanded state. Thus, the stent is expandable from the collapsed state to the expanded state, such that upon expansion, the stent transforms from having the first cross-sectional non-convex shape into the second cross-sectional convex shape.

"To form the con-convex shape, the stent is made of a material that allows it to be shape set. For example, the stent can be formed of an elastic material, a super elastic material (e.g., super elastic Nitinol), a shape memory material (e.g., a shape memory alloy such as Nitinol), and a magnetic memory material (e.g., magnetic shape memory alloys, such as Ni.sub.2MnGa). In another aspect, the stent can be formed of a dissolving material (e.g., polylactic acid) to allow it to dissolve after being applied for a certain amount of time.

"As can be appreciated by one skilled in the art, due to its shape setting properties and the non-convex cross-section, the stent is capable of dramatically reducing its cross-sectional radial profile which is beneficial in a variety of procedures. For example, the stent can be formed as a component of a heart valve. As another example, the stent can be a component of a coronary stent system. In yet another example, the stent is a ureteral stein used to maintain the patency of a ureter. The stent can also be formed as a prostatic stent, or be drug coated to operate as a drug eluting stent. In another example, the stent can be a component of a peripheral artery angioplasty. Further, the stent can be formed as a component of a stent graft used for endovascular surgery. Thus, while the examples provide above enable one skilled in the art to envision various forms and uses of the stent, the present invention is not intended to be limited thereto as the stent can be used in any circumstance where a reduced radial diameter is desirable.

"Finally, as can be appreciated by one skilled in the art, the present invention also comprises a method for forming and using the invention described herein. For example, the construct (e.g., stent) can be formed by performing acts of collapsing a stent radially into a stent having a cross-sectional convex shape; applying a load to at least one location on the stent to form a collapsed stent having a cross-sectional non-convex shape; and shape setting the stent to having a shape set cross-sectional non-convex shape. Alternatively, the stent can be applied to a desired location by performing acts of inserting the collapsed stent having a cross-sectional non-convex shape into a user until reaching a desired location; and causing the collapsed stent to transform into an expanded stent having a cross-sectional convex shape."

URL and more information on this patent, see: Kheradvar, Arash; Gharib, Morteza. Expandable Stent That Collapses into a Non-Convex Shape and Expands into an Expanded, Convex Shape. U.S. Patent Number 8702788, filed April 7, 2011, and published online on April 22, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=104&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=5175&f=G&l=50&co1=AND&d=PTXT&s1=20140422.PD.&OS=ISD/20140422&RS=ISD/20140422

Keywords for this news article include: Cardio Device, Medical Devices, California Institute of Technology.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


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Source: Cardiovascular Week


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