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 undulating or sinusoidal elements which, when compressed, nest tightly with each other.

Description:
This is a divisional of U.S. application Ser. No. 10/163,248, filed Jun. 5, 2002 now U.S. Pat. No. 6,881,013, which claims the benefit of provisional patent Application No. 60/298,325, filed Jun. 14, 2001. 
    
    
     BACKGROUND 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. 
     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 device 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 generally undulating members and a plurality of struts. The undulating members are generally parallel with the longitudinal axis of the tubular member and are generally parallel to each other. In addition, the undulating members have a plurality of peaks. The undulating members and struts are interconnected and have a repeating pattern in which the proximal ends of the struts are attached to the peaks of the undulating members and the distal end of the struts are attached to the peaks of adjacent undulating members. 
     In accordance with another aspect of the present invention, the skeletal tubular member has a very small compressed diameter for delivery within a vessel and a normally biased expanded diameter for retaining the stent against the walls of the vessel. As the tubular member is compressed to its small diameter, the peaks of the undulating members pull upon the proximal end of the struts and the distal ends of the struts pull upon peaks of adjacent undulating members thereby causing the cells of the tubular members to collapse and “nest” together. This nesting causes the skeletal tubular member to retain a very small diameter. 
     In accordance with another aspect of the present invention, the skeletal tubular member includes at least two proximal legs which extend generally parallel to the longitudinal axis of the tubular member and are attached to the proximal end of the tubular member. At least one of the proximal legs includes a T-shaped or I-shaped attachment flange. 
     In accordance with still another aspect of the present invention, the proximal legs are biased outwardly from the longitudinal axis of the tubular member. The proximal legs preferably include a radiopaque marker for positioning the stent within a vessel. 
     In accordance with another aspect of the present invention, the tubular member includes at least one distal leg which extends generally parallel to the longitudinal axis of the tubular member and is attached to the distal end of the tubular member. The distal leg preferably includes a radiopaque marker for locating the distal end of the stent as the stent is placed in a vessel. 
     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 which is formed with a thin wall. The wall of the tubular member includes a plurality of cells which are formed by a plurality of sinusoidal members and a plurality of struts. The sinusoidal members are generally parallel to the longitudinal axis of the tubular member and are generally parallel to each other. Each sinusoidal member has a plurality of positive peaks and negative peaks. The sinusoidal members and the struts are interconnected and have a repeating pattern in which each strut connects a positive peak of a sinusoidal member with a negative peak of an adjacent sinusoidal member. 
     In accordance with still anther aspect of the present invention, the skeletal tubular member has a very small compressed diameter for delivery within a vessel and a normally biased expanded diameter for retaining the stent device against the walls of a vessel. As the tubular member is compressed to its small diameter, the positive peaks of the sinusoidal members pull the struts, and the struts pull the negative peaks of adjacent sinusoidal members thereby causing the cells of the tubular member to collapse with the result that the sinusoidal members “nest” together with adjacent sinusoidal members in order to provide a very small diameter stent device. 
     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 generally undulating members and a plurality of struts. The undulating members are generally parallel with the longitudinal axis of the tubular member and are generally parallel to each other. In addition, the undulating members have a plurality of peaks. The undulating members and struts are interconnected and have a repeating pattern in which the proximal ends of the struts are attached to the peaks of the undulating members and the distal end of the struts are attached to the peaks of adjacent undulating members. 
     These and other aspects of the present invention and the advantages thereof will be more clearly understood from the foregoing description in 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 which is laser cut to form a thin-walled, skeletal tubular member  11  comprised of nickel-titanium alloy. Once cut, the wall 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 reduce 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 undulating members  24  and struts  26 . Each strut  26  has a proximal end  28  and a distal end  30 . Each undulating member  24  has a proximal end  32 , a plurality of peaks  34 , and a distal end  36 . The proximal end  32  is the left tip of an undulating member  24 . The peaks  34  are the highest and lowest points of an undulating member  24 . The distal end  36  is the right tip of an undulating member  24 . 
     The undulating members  24  and struts  26  are interconnected in a way to maximize “nesting” of the undulating members  24  to thereby minimize the compressed diameter of the skeletal tubular member  11  during deployment. The proximal end  28  of each strut  26  is attached to a peak  34  of an undulating member  24  and the distal end  30  of the same strut  26  is attached to a peak  34  of an adjacent undulating member  24 . This interconnection of undulating members  24  and struts  26  permits the cells  14  of the skeletal tubular member  11  to collapse and allows the tubular member  11  to attain a compressed diameter. 
     The repetitive cell pattern of the skeletal tubular member  11  may also be formed by interconnected sinusoidal members  38  and struts  26 . Each sinusoidal member  38  has a proximal end  40 , a plurality of positive peaks  42 , a plurality of negative peaks  44 , and a distal end  45 . The proximal end  40  is the left tip of a sinusoidal member  38 . The positive peaks  42  are the highest points of a sinusoidal member  38 . The negative peaks  44  are the lowest points of a sinusoidal member  38 . The distal end  45  is the right tip of a sinusoidal member  38 . 
     The sinusoidal members  38  and struts  26  are interconnected in a way to maximize “nesting” of the sinusoidal members  38  thereby minimizing the compressed diameter of the skeletal tubular member  11  during deployment. Each strut  26  connects a positive peak  42  of a sinusoidal member  38  with a negative peak  44  of an adjacent sinusoidal member  38 . This interconnection of sinusoidal members  38  and struts  26  permits the cells  14  of the skeletal tubular member  11  to collapse and allows the tubular member  11  to attain 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 undulating members  24  and struts  26 , the proximal legs  18 ,  18   a , and  18   b  are connected to the proximal ends  32  of undulating members  24 , and the distal legs  22  and  22   a  are connected to the distal ends  36  of undulating members  24 . In the repetitive cell pattern formed by sinusoidal members  38  and struts  26 , the proximal legs  18 ,  18   a , and  18   b  are connected to the proximal ends  40  of sinusoidal members  38 , and the distal legs  22  and  22   a  are connected to the distal ends  45  of sinusoidal members  38 . 
     It should be understood that the stent device of the present invention may alternatively be coated with an agent, such as heparin or rapamycin, 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.