Abstract:
A very small diameter intravascular stent device which may be used to occlude or partially occlude an aneurysm in the human brain which is comprised of a thin-walled skeletal cylindrical tube formed of S-shaped or sinusoidal elements which, when compressed, nest tightly with each other.

Description:
This application is a Provisional of U.S. patent application Ser. No. 60/298,326 filed on 06/14/2001. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to intravascular devices for implantation within a vessel of the body, and more particularly to a stent device which may be used in the treatment of blood vessel disorders. More specifically, the intravascular device may take the form of an aneurysm cover to be used in the treatment of aneurysms which occur in the brain. 
     2. Description of the Prior Art 
     On a worldwide basis, nearly one million balloon angioplasties were performed in 1997 to treat vascular disease, including blood vessels clogged or narrowed by a lesion or stenosis. The objective of this procedure is to increase the inner diameter or cross-sectional area of the vessel passage, or lumen, through which blood flows. 
     Another serious vascular defect is an area of weakened vessel wall that causes a bulge, or bubble, to protrude out in a radial direction from the vessel. This type of defect is called an aneurysm. If untreated, the aneurysm may continue expanding until it bursts thereby causing hemorrhaging from the vessel. 
     In an effort to prevent restenosis or treat an aneurysm without requiring surgery, short flexible cylinders or scaffolds, made of metal or polymers, are often placed into a vessel to maintain or improve blood flow. Referred to as stents, various types of these devices are widely used for reinforcing diseased blood vessels, for opening occluded blood vessels, and for defining an internal lumen to relieve pressure in an aneurysm. The stents allow blood to flow through the vessels at an improved rate while providing the desired lumen opening or structural integrity lost by the damaged vessels. Some stents are expanded to the proper size by inflating a balloon catheter, referred to as “balloon expandable” stents, while others are designed to elastically resist compression in a “self-expanding” manner. 
     Balloon expandable stents and self-expanding stents are generally delivered in a cylindrical form, crimped to a smaller diameter and are placed within a vessel using a catheter-based delivery system. When positioned at a desired site within a vessel, these devices are expanded by a balloon, or allowed to “self-expand,” to the desired diameter. 
     One such stent for treatment of abdominal aortic aneurysms is disclosed in U.S. Pat. No. 6,267,783 to Robert P. Letendre, et al. This patent discloses a self-expanding stent which may be used in the treatment of aortic aneurysms. This device may be easily recaptured after placement and repositioned to a new position within the vessel. This patent, assigned to a related company, is subsequently referred to and the disclosure therein is incorporated and made a part of the subject patent application. 
     Another stent aneurysm treatment device is disclosed in U.S. Pat. No. 6,361,558, assigned to the same assignee as the present application. This patent discloses vasculature stents of various configurations which may be used as aneurysm covers for occluding, or partially occluding, aneurysms located at various positions along the blood vessels. 
     SUMMARY OF THE INVENTION 
     There is a need for an improved stent which may be easily delivered to a vasculature site through a very small catheter, is capable of being repositioned and which exhibits sufficient structural integrity and resilience under radial compressive forces. More particularly, there is a need for such a stent that, in its compressed state prior to delivery of the stent, has a diameter which is extremely small. Such a stent could be placed in a very small microcatheter for subsequent positioning within a vessel of the human brain. Obviously, such vessels are extremely small and very tortuous throughout their length. 
     In accordance with one aspect of the present invention, there is provided a self-expanding stent which includes a small diameter skeletal tubular member. The skeletal tubular member is comprised of a plurality of cells which are formed by a plurality of interconnected, non-inverted horizontal and inverted horizontal S-shaped members. The S-shaped members are generally parallel to the longitudinal axis of the tubular member and are interconnected in a repeating pattern. Each of the S-shaped members has a proximal end, a distal end, a proximal intermediate section and a distal intermediate section. The proximal end of each non-inverted horizontal S-shaped member is attached to the distal intermediate section of an adjacent inverted horizontal S-shaped member, the distal end of each non-inverted horizontal S-shaped member is attached to the proximal intermediate section of another adjacent inverted horizontal S-shaped member, the proximal end of each inverted horizontal S-shaped member is attached to the distal intermediate section of an adjacent non-inverted horizontal S-shaped member, and the distal end of each inverted horizontal S-shaped member is attached to said proximal intermediate section of another adjacent non-inverted horizontal S-shaped member. With this configuration, the skeletal tubular member may be compressed to a very small diameter because of “nesting” of adjacent S-shaped members. 
     In accordance with another aspect of the present invention, as the skeletal tubular member is compressed into a small diameter, each proximal intermediate section of each non-inverted horizontal S-shaped member pulls on a distal end of an adjacent inverted horizontal S-shaped member, each distal intermediate section of each non-inverted horizontal S-shaped member pulls on a proximal end of another adjacent inverted horizontal S-shaped member, each proximal intermediate section of each inverted horizontal S-shaped member pulls on the distal end of an adjacent non-inverted horizontal S-shaped member, and each distal intermediate section of each inverted S-shaped member pulls on the proximal end of an adjacent non-inverted horizontal S-shaped member thereby causing the “cells” of the S-shaped member, “nest” and cause the tubular member to attain the small diameter. 
     In accordance with another aspect of the present invention, the skeletal tubular member includes at least two proximal legs which are attached to the skeletal tubular member and which extend generally parallel to the longitudinal axis of the tubular member. At least one of the proximal legs includes a T-shaped flange adjacent to the end of the proximal leg for attachment to a stent release mechanism. 
     In accordance with another aspect of the present invention, the legs are biased outwardly away from the longitudinal axis of the skeletal tubular member. The legs may also include radiopaque markers for providing an indication of the location of the stent device as the device is positioned within a vessel. 
     In accordance with still another aspect of the present invention, the skeletal tubular member may include distal legs which are attached to and extend generally parallel to the longitudinal axis of the skeletal tubular member. These legs may also include radiopaque markers for providing positioning information. 
     In accordance with still another aspect of the present invention there is provided a self-expanding stent device which includes a small diameter skeletal tubular member. The wall of the skeletal tubular member is comprised of a plurality of cells which are formed by interconnected sinusoidal members. The sinusoidal members are generally parallel to the longitudinal axis of the tubular member. Each sinusoidal member extends for one and a half sinusoidal periods, or about 540 degrees. Each sinusoidal member has a proximal end, a distal end, a proximal peak and a distal peak. The sinusoidal members have a repeating pattern in which the proximal end of each sinusoidal member is attached to the distal peak of an adjacent sinusoidal member. Also, the distal end of each sinusoidal member is attached to the proximal peak of another adjacent sinusoidal member. 
     In accordance with another aspect of the present invention, in its compressed state, the proximal peak of each sinusoidal member pulls the distal end of an adjacent sinusoidal member and the distal peak of each sinusoidal member pulls the proximal end of an adjacent sinusoidal member causing the cells of the wall to collapse, or “nest,” thereby allowing the skeletal tubular member to attain a small compressed diameter. 
     In accordance with still another aspect of the present invention, a self-expanding aneurysm cover is provided which when placed across an aneurysm of a blood vessel reduces, or obstructs, the flow of blood between the aneurysm and its related blood vessel. The aneurysm cover includes a small diameter skeletal tubular member which is comprised of a plurality of cells which are formed by a plurality of interconnected, non-inverted horizontal and inverted horizontal S-shaped members. The S-shaped members are generally parallel to the longitudinal axis of the tubular member and are interconnected in a repeating pattern. Each of the S-shaped members has a proximal end, a distal end, a proximal intermediate section and a distal intermediate section. The proximal end of each non-inverted horizontal S-shaped member is attached to the distal intermediate section of an adjacent inverted horizontal S-shaped member, the distal end of each non-inverted horizontal S-shaped member is attached to the proximal intermediate section of another adjacent inverted horizontal S-shaped member, the proximal end of each inverted horizontal S-shaped member is attached to the distal intermediate section of an adjacent non-inverted horizontal S-shaped member, and the distal end of each inverted horizontal S-shaped member is attached to said proximal intermediate section of another adjacent non-inverted horizontal S-shaped member. With this configuration, the skeletal tubular member may be compressed to a very small diameter because of “nesting” of adjacent S-shaped members. 
     These and other aspects of the invention and the advantages thereof will be clearly understood from the following description and drawings of a preferred embodiment of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an oblique prospective view of an intravascular stent constructed in accordance with a preferred embodiment of the present invention; 
     FIG. 1 a  is an expanded view of the proximal portion of the retaining legs shown in FIG. 1; 
     FIG. 2 is a side elevational view of the intravascular stent illustrated in FIG. 1 with the tubular stent being cut along a line and flattened into a single plane; and, 
     FIG. 3 illustrates in more detail the proximal retaining legs of FIG. 1 a  and the interconnecting elements between the intravascular stent and a positioning catheter. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a self-expanding stent device  10  which is laser cut to form a thin-walled, skeletal tubular member  11  comprised of nickel-titanium alloy. Once cut, the wall  12  of the tubular member  11  includes several openings, or cells  14 . When the skeletal tubular member  11  is placed over an aneurysm, a physician is able to deliver embolic coils or other such devices through the cells  14  and into the aneurysm. The tubular member  11  also functions to cover the mouth of the aneurysm thus obstructing, or partially obstructing, the flow of blood into the aneurysm. Also, the tubular member  11  prevents medical devices such as embolic coils from escaping the aneurysm. 
     The preferred length of the skeletal tubular member  11  may range from 0.0795 inches to 3.15 inches. The diameter of the tubular member  11  varies depending on its deployment configuration. In a non-deployed or expanded state, the diameter of the tubular member  11  may extend up to about 0.4 inches. When the skeletal tubular member  11  is compressed to fit within the lumen of a deployment catheter, the diameter may be reduced to about 0.014 inches. 
     Attached to the proximal end  16  of the skeletal tubular member  11  are three proximal legs  18 ,  18   a,  and  18   b  that extend longitudinally from the tubular member  11 . The proximal legs  18 ,  18   a,  and  18   b  are preferably biased outwardly from the longitudinal axis of the tubular member  11 . This outwardly biased configuration aids in the deployment system as subsequently described. 
     T-shaped or I-shaped attachment flanges  20 ,  20   a,  and  20   b  are attached to the tips of each proximal leg  18 ,  18   a,  and  18   b.  FIG. 1 a  describes the T-shaped or I-shaped flanges  20 ,  20   a,  and  20   b  in more detail. Attached to the distal end  21  of the skeletal tubular member  11  are two distal legs  22  and  22   a  that extend longitudinally away from the tubular member  11 . 
     FIG. 1 a  illustrates in detail one of the T-shaped or I-shaped attachment flanges  20  which is also laser cut from the skeletal tubular member  11  at the proximal end of one of the proximal legs  18 . The T-shaped or I-shaped attachment flange  20  is slightly arched and oriented on the proximal leg  18  such that the arch coincides with the wall  12  of the tubular member  11 . 
     FIG. 2 illustrates the repetitive cell pattern of the skeletal tubular member  11 . The cell pattern may be formed by interconnected non-inverted horizontal S-shaped members  24  and inverted horizontal S-shaped members  26 . Each S-shaped member has a proximal end  28 , a proximal intermediate section  30 , a proximal portion  31 , a distal intermediate section  32 , and a distal end  34 . The non-inverted horizontal S-shaped members  24  are slightly flattened “S” configurations laying horizontal to the axis of the skeletal tubular member  11  and having its proximal portion  31  pointing up. The inverted horizontal S-shaped members  26  are slightly flattened “S” configurations laying horizontal to the axis of the tubular member  11  and having its proximal portion  31  pointing down. The proximal end  28  is the left tip of an S-shaped member. The proximal intermediate section  30  of a non-inverted horizontal S-shaped member  24  is the negative (down) peak of an S-shaped member. The proximal intermediate section  30  of an inverted horizontal S-shaped member  26  is the positive (up) peak of an S-shaped member. The proximal portion  31  is the portion of an S-shaped member between the proximal end  28  and the proximal intermediate section  30 . The distal intermediate section  32  of a non-inverted horizontal S-shaped member  24  is the positive peak of an S-shaped member. The distal intermediate section  32  of an inverted horizontal S-shaped member  26  is the negative peak of an S-shaped member. The distal end  34  is the right tip of an S-shaped member. 
     The S-shaped members are interconnected in a way to maximize “nesting” of the S-shaped members to thereby minimize the compressed diameter of the skeletal tubular member  11  during deployment. The proximal end  28  of each non-inverted horizontal S-shaped member  24  is connected to the distal intermediate section  32  of an adjacent inverted horizontal S-shaped member  26 . The distal end  34  of each non-inverted horizontal S-shaped member  24  is connected to the proximal intermediate section  30  of another adjacent inverted horizontal S-shaped member  26 . The proximal end  28  of each inverted horizontal S-shaped member  26  is connected to the distal intermediate section  32  of an adjacent non-inverted horizontal S-shaped member  24 . The distal end  34  of each inverted horizontal S-shaped member  26  is connected to the proximal intermediate section  30  of another adjacent non-inverted horizontal S-shaped member  24 . This interconnection of S-shaped members permits the cells  14  of the skeletal tubular member  11  to collapse and allows the tubular member  11  to attain a compressed diameter. 
     The cell pattern of the skeletal tubular member  11  may also be considered as being formed by interconnected sinusoidal members  36 . Each sinusoidal member  36  has a period of approximately one and a half, or about 540 degrees. Each sinusoidal member  36  has a proximal end  38 , a proximal peak  40 , a distal peak  42 , and a distal end  44 . The proximal end  38  is the left tip of a sinusoidal member  36 . The proximal peak  40  is the first peak to the right of the proximal end  38  and is either positive or negative. The distal peak  42  is the second peak to the right of the proximal end  38  and is either positive or negative. However, each sinusoidal member  36  has only one positive peak and one negative peak. The distal end  44  is the right tip of a sinusoidal member  36 . 
     The sinusoidal members  36  are interconnected in a way to maximize “nesting” of the sinusoidal members to thereby minimize the compressed diameter of the skeletal tubular member  11  during deployment. The proximal end  38  of each sinusoidal member  36  is connected to the distal peak  42  of an adjacent sinusoidal member  36 . The proximal peak  40  of each sinusoidal member  36  is connected to the distal end  44  of another adjacent sinusoidal member  36 . The distal peak  42  of each sinusoidal member  36  is connected to the proximal end  38  of yet another adjacent sinusoidal member  36 . The distal end  44  of each sinusoidal member  36  is connected to the proximal peak  40  of still another adjacent sinusoidal member  36 . This interconnection of sinusoidal members  36  permits the cells  14  of the skeletal tubular member  11  to collapse and allows the tubular member  11  to obtain a compressed diameter. 
     Also illustrated in FIG. 2 are the proximal legs  18 ,  18   a,  and  18   b  and the distal legs  22  and  22   a.  In the repetitive cell pattern formed by S-shaped members, the proximal legs  18 ,  18   a,  and  18   b  are connected to the proximal ends  28  of non-inverted horizontal S-shaped members  24  on the proximal end  16  of the skeletal tubular member  11 . The distal legs  22  and  22   a  are connected to the distal ends  34  of inverted horizontal S-shaped members  26  on the distal end  21  of the tubular member  11 . In the repetitive cell pattern formed by sinusoidal members  36 , the proximal legs  18 ,  18   a,  and  18   b  are connected to the proximal ends  38  of sinusoidal members  36  on the proximal end  16  of the tubular member  11 . The distal legs  22  and  22   a  are connected to the distal ends  44  of sinusoidal members  36  on the distal end  21  of the tubular member  11 . 
     It should be understood that the stent device of the present invention may alternatively be coated with an agent, such as heparin or rapamycing, to prevent stenosis or restenosis of the vessel. Examples of such coatings are disclosed in U.S. Pat. Nos. 5,288,711; 5,516,781; 5,563,146 and 5,646,160. The disclosures in these patents are incorporated herein by reference. 
     FIG. 3 illustrates the deployment system  46  for the stent device  10 . The deployment system  46  includes an outer sheath  48  which is essentially an elongated tubular member, similar to ordinary guiding catheters which are well known to those of ordinary skill in the art. The deployment system  46  also includes an inner shaft  50  located coaxially within the outer sheath  48  prior to deployment. The inner shaft  50  has a distal end  52  and a proximal end (not shown). The distal end  52  of the shaft  50  has three grooves  54 ,  54   a,  and  54   b  disposed thereon. When the deployment system  46  is not fully deployed, the stent device  10  is located within the outer sheath  48 . The T-shaped or I-shaped attachment flanges  20 ,  20   a,  and  20   b  on the proximal legs  18 ,  18   a,  and  18   b  of the tubular member  11  are set within the grooves  54 ,  54   a,  and  54   b  of the inner shaft  50 , thereby releasably attaching the stent device  10  to the inner shaft  50 . This deployment system is described in more detail in U.S. Pat. No. 6,267,783 assigned to the same assignee as the present patent application. The disclosure in this patent is incorporated herein by reference and made a part of the present patent application. 
     A novel system has been disclosed in which a self-expanding stent device comprises a laser cut, skeletal tubular member having a plurality of cells. Although a preferred embodiment of the invention has been described, it is to be understood that various modifications may be made by those skilled in the art without departing from the scope of the claims which follow.