Abstract:
Disclosed herein is a stent which is inserted into a blood vessel of a patient who has to periodically undergo hemodialysis. The stent includes a wire frame which has a hollow cylindrical structure, and a window which is formed in a predetermined portion of a circumferential surface of the wire frame. The window has no wire therein. In an embodiment, the stent may further a graft which covers the wire frame and the window. The present invention can solve problems not only of deformation of the stent graft which occurs when a hemodialysis needle is inserted into the stent in the conventional technique, but also of patient discomfort when having skin punctured high cost, thrombopoiesis, a risk of recurrence, etc.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a stent provided with a window, and an artificial vessel having the stent. 
         [0003]    2. Description of the Related Art 
         [0004]    Maintenance of function of the arteriovenous fistula is so indispensable to renal failure patients who are undergoing maintenance hemodialysis that it is sometimes called a lifeline. However, there is no arteriovenous fistula which over the course of a patient&#39;s life can be used problem-free once the operation is performed. Typically, an arteriovenous fistula leads to complications in the long-term. A false or true aneurismal change causes a lot of problems in terms of not only appearance but also blood flow. Moreover, an aneurismal change may cause massive hemorrhage resulting from rupture, so that it may threaten a patient&#39;s life. Therefore, such an aneurismal change has to be treated. As for treatment methods, surgical treatment and minimally invasive treatment, for example, inserting a stent graft into a blood vessel of a patient, are representative examples. 
         [0005]    However, even if such a stent graft is inserted into the body of a renal failure patient, the patient must regularly undergo hemodialysis. 
         [0006]    To conduct hemodialysis, a hemodialysis needle  10  which is comparatively thick should be punctured on a stent graft  20 . Here, as shown in  FIG. 1 , a problem that frequently occurs is that wire frame  30  of the stent graft  20  is deformed when frequently inserting a hemodialysis needle  10  into the stent graft  20 . 
       SUMMARY OF THE INVENTION 
       [0007]    Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a stent and an artificial vessel having the stent which is configured such that even if repeated puncture by means of a hemodialysis needle occurs, a wire frame of the stent can be prevented from being deformed. 
         [0008]    In order to accomplish the above object, based on TRIZ that is a problem-solving theory derived from the study of patterns of invention, the inventor of the present invention defined the above-stated object as follows. 
         [0009]    “To prevent a wire frame from being deformed when conducting a needle puncture for hemodialysis, there must be no wire frame in physical terms, but the wire frame is essential to ensure the function of the stent.” 
         [0010]    In other words, the wire frame must be present despite the problems associated with it. According to TRIZ, this is physical contradiction. The inventor of the present invention gives attention to “separation in space” of principles of separation which are principles of solution of the physical contradiction, and to “local quality” of forty kinds of principles (40 principles). Therefore, the inventor has devised a stent and an artificial vessel having the stent, which is defined by the accompanying claims, using notions “separation in space” and “local quality.” 
         [0011]    In an aspect, the present invention provides a stent, including: a wire frame having a hollow cylindrical structure; and a window formed in a predetermined portion of a circumferential surface of the wire frame, the window having no wire therein. The stent may further include an outer covering which covers the wire frame and the window. 
         [0012]    The predetermined portion of the circumferential surface of the wire frame may be a portion of an upper half area or a lower half area of the wire frame. A portion of the outer covering that covers the window may be thicker than a portion of the outer covering that covers the wire frame other than the window. The outer covering may comprise a graft. 
         [0013]    In another aspect, the present invention provides an artificial vessel, including: a stent comprising a wire frame having a hollow cylindrical structure, and a window formed in a predetermined portion of a circumferential surface of the wire frame, the window having no wire therein; and a graft covering the stent. The predetermined portion of the circumferential surface of the wire frame may be a portion of an upper half area or a lower half area of the wire frame. A portion of the graft that covers the window may be thicker than a portion of the graft that covers the wire frame other than the window. The artificial vessel may further include a marker indicating a location of the window. The marker may be made of a radio-opaque material. In a further aspect, the present invention provides a puncture method, including: disposing the stent according to any one of claims  1  through  4  in a blood vessel of a patient using a dispenser; and puncturing a skin of the patient using a needle and inserting the needle into the stent in such a way that the needle passes through the window of the stent. In still another aspect, the present invention provides a puncture method, including: disposing the artificial vessel according to any one of claims  6  through  8  in a blood vessel of a patient using a dispenser; and puncturing a skin of the patient using a needle and inserting the needle into the stent in such a way that the needle passes through the window of the stent. 
         [0014]    According to the present invention, the function of arteriovenous fistula of a patient who has to periodically undergo hemodialysis can be improved, and a patency rate is increased, whereby hemodialysis can be smoothly conducted. 
         [0015]    As such, the present invention can solve problems not only of deformation of the stent graft which occurs when a hemodialysis needle is inserted into the stent in the conventional technique, but also of patient discomfort when having skin punctured, high cost, thrombopoiesis, a risk of recurrence, etc. 
         [0016]    The effects of the present invention are not limited to the above-stated effects, and those skilled in the art will clearly understand other not mentioned effects from the accompanying claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0018]      FIG. 1  is a view showing a stent graft according to a conventional technique; 
           [0019]      FIG. 2  is a perspective view illustrating a stent, according to a first embodiment of the present invention; 
           [0020]      FIG. 3  is a plan view illustrating the stent of  FIG. 2 ; 
           [0021]      FIG. 4  is a side view illustrating the stent of  FIG. 2 ; 
           [0022]      FIG. 5  is a perspective view illustrating an artificial vessel in which a stent is covered with a graft, according to a second embodiment of the present invention; 
           [0023]      FIG. 6  is a plan view illustrating the artificial vessel of  FIG. 5 ; 
           [0024]      FIG. 7  is a side view illustrating the artificial vessel of  FIG. 5 ; 
           [0025]      FIG. 8  is a sectional view taken along line A-A′ of  FIG. 7 ; 
           [0026]      FIGS. 9A and 9B  are perspective views showing an artificial vessel provided with a marker; and 
           [0027]      FIG. 10  is a view of an artificial vessel to illustrate a puncture operation. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    With regard to embodiments of the present invention that are disclosed in this specification, special structural or functional explanation is used only for illustrative purposes, and the embodiments of the present invention can be modified in a variety of forms. Therefore, the present invention must not be interpreted as being limited to the embodiments of this specification. 
         [0029]    Given the fact that various modifications of the present invention are possible, preferred embodiments of the present invention will be illustrated in the drawings and explained in this specification. However, these embodiments are not intended to limit the present invention to special forms. Rather, all changes that fall within the bounds of the present invention, or the equivalence of the bounds should be understood to be embraced by the present invention. 
         [0030]    Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. 
         [0031]      FIG. 2  is a perspective view illustrating a stent according to the present invention. As shown in the drawing, a stent  110  according to a first embodiment of the present invention includes a wire frame  130  and a window  140  which has no wire. The stent  110  has a general cylindrical structure of a predetermined width and length. The wire frame  130  forms a hollow cylindrical structure. The window  140  which has no wire is formed in a predetermined portion of a circumferential outer surface of the wire frame  130 . The portion in which window  140  is formed is disposed in an upper half area or a lower half area of the wire frame  130 . 
         [0032]    In detail, the wire frame  130  includes a plurality of rows of circumferential wires, each of which extends in a circumferential direction in a zigzag shape. The circumferential wires are spaced apart from each other at regular intervals. In portions of the wire frame  130  other than the window  140 , each circumferential wire has a circular shape. In a portion of the wire frame  130  in which the window  140  is present, each circumferential wire has a hemispheric shape. Furthermore, the cylindrical wire frame  130  includes a plurality of longitudinal wires, each of which extends a predetermined length in a longitudinal direction, and which are spaced apart from each other at regular intervals. As such, the wire frame  130  forms a hollow cylindrical structure in such a way that the zigzag circumferential wires and the longitudinal wires are connected to each other. 
         [0033]    Referring to  FIG. 3  showing a plan view of the stent  110 , zigzag circumferential wires are provided in opposite ends of the wire frame  130 , and the window  140  which has no wire is formed in a medial portion of the wire frame  130 . For the sake of understanding, a portion of the wire frame  130  that is disposed just below the window  140  is not shown in  FIG. 3 . Referring to  FIG. 4  showing a side view of the stent  110 , the zigzag circumferential wires are provided in the opposite ends of the wire frame  130 , and the window  140  is formed in an upper portion of the medial portion of the wire frame  130 . As such, the window  140  may be formed in a portion of the upper half area of the wire frame  130 , alternatively, it may be formed in a portion of the lower half area of the wire frame  130 . 
         [0034]    Meanwhile, although the wire frame  130  has predetermined elasticity, it can neither easily be contracted nor expanded by external force. The wire frame  130  maintains a cylindrical shape in the expanded state. 
         [0035]      FIG. 5  is a view illustrating an artificial vessel, according to a second embodiment of the present invention. The artificial vessel  120  according to this embodiment comprises a stent  110  of the first embodiment that is covered with an outer covering. The artificial vessel  120  of the second embodiment includes a wire frame  130  and a window  140  which has no wire, that is, substantially has the same elements as those of the stent  110  of the first embodiment. Therefore, in the explanation of the second embodiment, the same reference numerals are used to designate the same or similar elements as those of the first embodiment, and repeated explanation on the construction and function will be omitted. 
         [0036]    Referring to  FIG. 5 , the stent  110  which has a hollow cylindrical structure is covered with an outer covering  150 . Preferably, a portion of the outer covering  150  that covers the window  140  is thicker than a portion of the outer covering  150  that covers the wire frame  130  other than the window  140 . For reference, the outer covering  150  may be a polytetrafluoroethylene graft. In the same manner as the first embodiment, the stent  110  maintains a circular shape using the structure of the wire frame  130 . 
         [0037]      FIG. 6  is a plan view of the artificial vessel of the present invention, and  FIG. 7  is a side view of the artificial vessel of the present invention. As shown in the drawings, a plurality of zigzag rows circumferential wires are provided in opposite ends of the wire frame  130 , and the window  140  which has no wire is formed in a medial portion of the wire frame  130 . The portion of the outer covering  150  that covers the window  140  is thicker than, for example, is twice as thick as the portion of the outer cover  150  that covers the wire frame  130  (refer to  FIG. 8 ). The portion of the outer covering  150  that covers the window  140  is configured to have structural stability such that the artificial vessel  120  which is inserted into a blood vessel  102  of a patient can maintain the same supporting force as that of the wire frame  130  and have durability such that, even if puncture by means of a hemodialysis needle  104  is repeatedly conducted, its shape can be maintained. 
         [0038]    Referring to  FIG. 9 , to form the stent  110  covered with the outer covering  150 , markers  160  may be used to indicate the location of the window  140 . The markers  160  are disposed on predetermined portions of the outer covering  150  that corresponds to the window  140 . The markers  160  may be preferably printed on the outer covering  150  in a predetermined pattern so that a portion of the outer covering  150  that corresponds to the window  140  can be indicated on the outer surface of the outer covering  150 . In another embodiment, the markers  160  may be removably provided on the outer covering  150 . Preferably, the markers  160  are disposed adjacent to the window  140  and are made of radio-opaque material so that the markers  160  can be observed on a radiograph. When the markers  160  which are made of radio-opaque material are radiographed, the markers  160  are expressed on a radiograph so that the location of the window  140  can be easily indicated. Given the fact that, when the artificial vessel  120  is inserted into a blood vessel  102 , the location of the window  140  may be changed, it is preferable that the location of the window  140  be indicated by the markers  160 . 
         [0039]    In other words, after the artificial vessel  120  has been disposed in the blood vessel  102 , the location of the window  140  in the blood vessel  102  can be easily indicated by the markers  160  using radiography such as fluoroscopy or X-ray graphy. After the location of the window  140  has been discerned, puncture by means of the hemodialysis needle  104  can be conducted through the window  140 . 
         [0040]    A dispenser is used to insert the stent  110  of the first embodiment or the artificial vessel  120  of the second embodiment into a blood vessel of a patient, particularly, into an arteriovenous fistula of a renal failure patient. After an operation of installing the stent  110  or the artificial vessel  120  has been completed, blood dialysis for the renal failure patient is conducted as follows. Referring to  FIG. 10 , unlike the conventional technique, the hemodialysis needle  104  can be easily punctured into the stent  110  or artificial vessel  120  only through the window  140  which has no wire. Therefore, even if puncture by means of the hemodialysis needle  104  is repeated several times, the shape of the wire frame  130  of the stent  110  can be prevented from deteriorating. 
         [0041]    The fact that the window  140  is formed in the wire frame  130  and the thickness of the outer covering (graft) which covers the wire frame  130  is different between a portion corresponding to the window  140  and the other portion can be interpreted to be technical characteristics of the present invention which use notions of “separation of space” and “partial quality improvement.” 
         [0042]    Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 
         [0043]    As described above, the present invention can be used to treat an aneurismal change caused on arteriovenous fistula of a patient who must periodically have hemodialysis. The present invention makes it possible for hemodialysis to be reliably conducted.