Abstract:
An expanding vascular stent is disclosed that is inserted into a blood vessel in the human body and expands the blood vessel. The stent is configured in such a way that adjacent rows, each of which is comprised of a plurality of identical cells, are symmetrically arranged, in an out of phase manner. When the stent is expanded in the radial direction, the adjacent rows are expanded in opposite directions, maintaining their linearly symmetrical state. Therefore, the reduction in the length of the stent can be minimized. Since the stent has also a great degree of flexibility, when it is inserted into the blood vessel, it can minimize the damage to the blood vessel wall.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to medical devices, and more particularly to an expanding vascular stent that is inserted into a blood vessel in the human body and expands the blood vessel, where it is improved in terms of structure to enhance its performance, compared with conventional stents. 
         [0003]    2. Background of the Invention 
         [0004]    A stent is an artificial tube inserted into a conduit in the human body, such as a blood vessel, etc., to hold the conduit open. The stent is shaped as a cylindrical hollow. The stent is inserted into a blood vessel, etc., opens a strangulated portion and holds it open. 
         [0005]    First, the stent needs a high expansion force to hold its cylindrical hollow shape. Second, it is preferable that the stent is as small as possible in the lengthwise and radial directions when it is initially expanded in the radial direction. Third, the stent requires a large degree of flexibility so that it does not damage the blood vessel wall or a balloon catheter when being inserted into a zigzagged blood vessel. 
         [0006]    In order to faithfully follow the conditions described above, research and development have been performed using conventional stents. According to US FDA guidelines, when a stent is initially expanded in the radial direction, the change in the length and radius of the stent is restricted to 5˜7%. In particular, they treat the expansion of the stent in the radial direction as an important factor. 
         [0007]    A great deal of research has been conducted on conventional stents conforming to the conditions described above, which were disclosed in Korean Patent Publication No. 10-2004-0075346, U.S. Pat. Nos. 7,326,241 and 7,442,203. For example, they have disclosed stents having the same cells being regularly repeated. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention solves the above problems, and provides an expanding vascular stent that is minimized in length and radial directions when it is inserted into a blood vessel in the body and initially expands in the radial direction, but that has a high degree of flexibility in the radial direction, thereby minimizing the damage to the blood vessel. 
         [0009]    In accordance with an exemplary embodiment of the present invention, there is provided an expanding vascular stent including: a body that is hollow in the lengthwise direction. The body includes a plurality of rows connected to each other, each row including a plurality of cells joined together. The adjacent rows are located in such a way that the plurality of cells in one row are symmetrically formed to the plurality of cells in another row, in an out of phase array. 
         [0010]    In accordance with another exemplary embodiment of the present invention, there is provided an expanding vascular stent including a body that is hollow in the lengthwise direction, including a plurality of cells joined together. Each of the plurality of cells includes at least two or more parts whose body is curved numerous times and whose one side is opened, in which both ends of the part are extended with a curved portion, the curved portions being curved in the same direction. 
         [0011]    Preferably, each of the plurality of cells includes first, second and third parts. The first part has a plurality of curved portions. The first part is symmetrically formed and opens on one side. The a second part has a plurality of curved portions, wherein the second part is joined to the first part, one end of the second part is symmetrically formed to the other end of the second part, and the second part is open on one side. The third part is symmetrically formed to the first part. The third part is joined to the second part. 
         [0012]    Preferably, the first cell includes a first unit having at least four curved portions and a second unit having at least two curved portions, where the second unit is joined to the first unit. 
         [0013]    Preferably, the second cell includes a unit having at least four curved portions, located at its one side, and another unit at the other side, in which the unit is symmetrically joined to another unit. 
         [0014]    Preferably, the body includes a plurality of rows each of which is comprised of a plurality of cells joined together. The plurality of rows are symmetrical with respect to the lengthwise direction of the rows and out of phase to each other. 
         [0015]    Preferably, the body includes first and second rows each of which is comprised of the plurality of cells joined together, and links each of which connects a first part of the first row to a third part of the second row. 
         [0016]    Preferably, each of the first and third parts includes: a first unit having at least four curved portions; and a second unit having at least two curved portions, the second unit being joined to the first unit. The link connects the first unit of the first part in the first row to the first unit of the third part in the second row. 
         [0017]    Preferably, the body includes: a first row comprised of a plurality of cells joined together; a second row comprised of a plurality of cells joined together; and a link connecting the second part in the first row to the second part in the second row. 
         [0018]    Preferably, the second part includes: a first unit having at least four curved portions, located at one side of the second part; and a second unit that is located at the other side of the second part and symmetrically joined to the first unit. The link connects the second unit of the second part in the first row to the first unit of the second part in the second row. 
         [0019]    Preferably, the body includes: a first row having a plurality of cells joined together; a second row having a plurality of cells joined together; a third row having a plurality of cells joined together; a first link connecting the first part in the first row to the third part in the second row; and a second link connecting the second part in the first row to the second part in the second row. The first and the second links are out of phase. 
         [0020]    In accordance with another exemplary embodiment of the present invention, there is provided an expanding vascular stent including: a body that is hollow in the lengthwise direction, having a plurality of cells joined together. Each of the plurality of cells includes: a plurality of first units each of which has at least four curved portions; and a plurality of second units each of which has at least two curved portions. Two first units and one second unit are located on one side and they are symmetrical to the units on the other side. 
         [0021]    Preferably, the plurality cells are joined together in order as the first unit, second unit, and first unit, with respect to a virtual axis. 
         [0022]    As described above, the stent is configured in such a way that adjacent rows, each of which is comprised of a plurality of identical cells, are symmetrically located in relation to each other, with being out of phase. Although the stent is expanded in the radial direction, the adjacent rows are expanded in the opposite directions, maintaining their linearly symmetrical state, thereby minimizing any reduction in the length of the stent. 
         [0023]    In addition, since the stent is configured in such a way that adjacent rows, each of which is comprised of a plurality of identical cells, are symmetrically located to each other, with being out of phase, it has a high degree of flexibility. The flexibility indicates the degree to which the stent is curved when an external force is applied to one side of the stent where the other side of the stent is fixed. When a stent with a high degree of flexibility is inserted into a zigzagged blood vessel, it can minimize damage to the blood vessel wall in the human body. 
         [0024]    Also, since the cells of the stent are symmetrically formed, when the stent is expanded in the radial direction, the plurality of parts composing the cells are symmetrically formed. Therefore, one cell can be uniformly expanded in both directions. 
         [0025]    Furthermore, since one cell of the stent is comprised of at least two or more parts and each of the parts forms a plurality of convex and concave portions in the same directions, correspondingly and respectively, when the stent is compressed in the radial direction and inserted into the human body, the convex and concave portions are compressed in the same directions correspondingly and respectively. Therefore, the stent can be compressed to the highest degree possible. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The features and advantages of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings, in which 
           [0027]      FIGS. 1A and 2B  illustrate an expanding vascular stent according to an embodiment of the present invention; 
           [0028]      FIGS. 2A and 2B  illustrate one of the plurality of cells that compose an expanding vascular stent according to an embodiment of the present invention; 
           [0029]      FIG. 3  is a detailed view illustrating the plurality of cells that compose an expanding vascular stent according to an embodiment of the present invention; 
           [0030]      FIG. 4  is a detailed view illustrating two rows joined together, composing an expanding vascular stent according to an embodiment of the present invention; 
           [0031]      FIG. 5  is a detailed view illustrating three rows joined together, composing an expanding vascular stent according to an embodiment of the present invention; and 
           [0032]      FIG. 6  is a view illustrating a cell showing side branch access and a closed curve of the cell, composing an expanding vascular stent according to an embodiment of the present invention. 
       
    
    
     BRIEF DESCRIPTION OF SYMBOLS IN THE DRAWINGS 
       [0000]    
       
         
           
               100 : stent 
               110   a : first cell 
               110   b : second cell 
               110   c : third cell 
               112   a : first part 
               112   b : second part 
               112   c : third part 
             p: first unit 
             q: second unit 
             r: third unit 
             s: fourth unit 
               120   a : first link 
               120   b : second link 
             I: row first 
             II: second row 
             III: third row 
             X: virtual axis 
           
         
       
     
       DETAILED DESCRIPTION OF THE INVENTION 
       [0050]    Hereinafter, exemplary embodiments of the present invention are described in detail with reference to the accompanying drawings. Detailed descriptions of well-known functions and structures incorporated herein may be omitted to avoid obscuring the subject matter of the present invention. 
         [0051]    Referring to  FIGS. 1A and 1B , the stent according to an embodiment of the present invention is shaped as a cylindrical hollow body that is comprised of a plurality of cells  110  joined together. The stent  100  is explained in detail with reference to  FIGS. 1A to 5  as follows. 
         [0052]    The stent  100  is structured in such a way that closed curve shapes are repeatedly joined together, forming its body. The repeatedly identical shape is called a cell  110 . A cell composing the stent  100  may be shaped differently according to the definition. In the following embodiment of the present invention, however, it is assumed that the cell  110  is shaped as shown in  FIGS. 2A and 2B . The cell  110  is configured to include first part  112   a , second part  112   b , and third part  112   c.    
         [0053]    As shown in  FIG. 2A , the first part  112   a  is shaped as the letter ‘C’. It is configured by a plurality of curves, is asymmetrical, and opens on one side. In more detail, the first part  112   a  is formed by the first unit p having four curved portions and the second unit q having two curved portions, where the first unit p is joined to the second unit q at each end of one side, so that the ends of the other side are opened. 
         [0054]    As shown in  FIG. 2B , the first unit p has four curved portions. Both opposite curved portions of the first unit p are curved facing opposite directions, so that they can be joined to the second unit q or an adjacent first unit symmetrically located to the first unit p. The four curved portions of the first unit p allow the first unit p to form two convex portions and two concave portions. 
         [0055]    In addition, both opposite curved portions of the first unit p are more curved compared with the two remaining curved portions in the middle of the first unit p, so that the four curved portions approximately form the letter ‘C’. 
         [0056]    As shown in  FIG. 2B , the second unit q of the first part  112   a  is located between the first unit p of the first part  112   a  and a first unit p of the second part  112   b . That is, the free end of the second unit q of the first part  112   a  is joined to one side end of the first unit p of the second part  112   b . The second unit q of the first part  112   a  has two curved portions. That is, the two curved portions of the second unit q allow the second unit q to form one convex portion and one concave portion. 
         [0057]    The free end of the second unit q is curved so that it can be smoothly connected to the first unit p of the second unit  112   b . The second unit q is formed in such a way that its convex and concave portions have a curvature that is smaller than the convex and concave portions of the first unit p, and the other portions (which do not include the convex and concave portions) are formed to be straight. 
         [0058]    That is, the second unit q is shaped to be angled by the straight portions, i.e., as a sigmoidal link, compared with the shape of the first unit p. 
         [0059]    The shape of the curved portion of the first unit p needs to be formed in the same direction as the shape of the curved portion of the second unit q. This is because, when the stent  100  is compressed in the radial direction, the curved portions of the first and second units p and q need to be close to each other without overlapping. In that case, the stent  100  can be maximally compressed in the radial direction. 
         [0060]    When the stent  100  is compressed in the radial direction, the entire shape of the first part  112   a  leans to the left, with respect to  FIG. 2B . This is because it is shown that the overall shape of the first unit p is shaped approximately as a straight line and the shape of the second unit q leans to the lower right. 
         [0061]    As shown in  FIG. 2A , the second part  112   b  is symmetrically formed with respect to the virtual axis X. That is, the second part  112   b  is formed in such a way that the first unit p is joined to a third unit r that is symmetrically formed as the first unit p with respect to the virtual axis X. Only the portion joining the first unit p and the third unit r is not smooth in the cell  110 , i.e., sharply bent. 
         [0062]    That is, this sharply bent portion is formed because both end portions of the first unit p and the third unit r are curved as an approximately semi-circle and they are symmetrically connected to each other with respect to the virtual axis X, as shown in  FIGS. 2A and 2B . 
         [0063]    As shown in  FIG. 2A , the third part  112   c  is symmetrically formed as the first part  112   a , with respect to the virtual axis X. That is, the first unit p is configured in such a way that a third unit r, symmetrically formed as the first unit p of the first part  112   a  with respect to the virtual axis X, is joined to a fourth s that is formed as the second unit q of the first part  112   a  with respect to the virtual axis X. 
         [0064]    Therefore, the first part  112   a , second part  112   b , and third part  112   c  are joined together to form the cell  110  that is symmetrical with respect to the virtual axis X. 
         [0065]    Referring to  FIGS. 2A and 2B , the cell  110  is formed in such a way that one line is curved a number of times and has elasticity, so that it is expandable in both widthwise directions under an external force but is restored when the external force is removed. 
         [0066]    As described above, since the first to third parts  112   a ˜ 112   c  have corresponding units p, q, r and s, and the units p, q, r, and s are curved many times, respectively, the stent  100  can be made of a high density material. Therefore, the stent  100  is advantageous in that it can be effectively expanded in the radial direction. 
         [0067]    When the cell  110  described above is plurally joined together, theses calls form a structure, i.e., a rolled out stent  100 , as shown in  FIG. 3 . One cell  110  is joined to another sequentially forming a row and then the row is joined to the other rows sequentially, thereby forming the rolled out stent  100 . 
         [0068]    In more detail, as shown in  FIGS. 4 and 5 , a first row I and a second row II, each formed by joining the cells, are connected to each other according to a certain rule. That is, the adjacent first row I and second row II are arranged as their virtual axes are out of phase, as shown in  FIG. 3 . 
         [0069]    For the sake of convenience, as shown in  FIG. 4 , it is assumed that a cell in the first row I is called a first cell  110   a  and a cell in the second row II is called a second cell  110   b . The first cell  110   a  and second cell  110   b  are located symmetrically and out of phase and a third part  112   c  of the first cell  110   a  is joined to a third part  112   c  of the second cell  110   b  via a first link  120   a , so that the first row I is connected to the second row II. 
         [0070]    As shown in  FIG. 4 , the first link  120   a  joins the first cell  110   a  and the second cell  110   b  so that the straight portion of the fourth unit s of the third part  112   c  of the first cell  110   a  is parallel to that of the fourth unit s of the third part  112   c  of the second cell  110   b . Therefore, the configured shape of the first cell  110   a  of the first row I is symmetrical to that of the second cell  110   b  of second row II. If the stent  100  is expanded in the radial direction, the lengths of the first and second rows I and II are decreased in opposite directions, so that the change in the entire length of the first and second rows I and II can be reduced. 
         [0071]    As shown in  FIG. 5 , three rows, for example, first, second and third rows I, II and III are joined together. The first cell  11   a  of the first row I is the same shape as the third cell  110   c  of the third row The second cell  110   b  of the second row II is linearly symmetrical to them. The first cell  110   a  of the first row I is parallel to the third cell  110   c  of the third row III in phase. 
         [0072]    The first link  120   a  connecting the first row I and the second row II is opposite, in direction, to the second link  120   b  connecting the second row II and the third row III, with the links being out of phase. 
         [0073]    The arrangement where the first link  120   a  and the second link  120   b  face the opposite directions, thus being out of phase, is designed so that the first and second links  120   a  and  120   b  are parallel to the directions of the straight portions of the second units q, respectively. Therefore, via the second link  120   b , the portion joining the first part  112   a  and the second part  112   b  of the second cell  110   b  in the second row II is connected to the portion joining the first part  112   a  and the second part  112   b  of the third cell  110   b  in the third row III. In an embodiment of the present invention, although the first and second links  120   a  and  120   b  are formed to be straight, it should be understood that the present invention is not limited to the embodiment. For example, the first and second links  120   a  and  120   b  may have a plurality of curved portions. 
         [0074]    Via the second link  120   b , the first unit p of the second part  112   b  at a portion joining the first part  112   a  and the second part  112   b  is connected to the first unit p of the second part  112   b  at a portion joining the first part  112   a  and the second part  112   b . The second link  120   b  is parallel to the straight portions of the second unit q of the first part  112   a  of the first cell  110   a  and the second unit q of the first part  112   a  of the second cell  110   b.    
         [0075]    As shown in  FIG. 5 , the first and second links  120   a  and  120   b  connect the first, second, and third rows I, II, and III. Therefore, if the stent  100  is expanded in the radial direction, the change in its length can be minimized in the lengthwise direction. 
         [0076]    When the stent  100  is expanded in the radial direction, the change in length can be acquired via a measurement know as Foreshortening, expressed as the following equation (1). Foreshortening refers to an index to indicate a ratio of changes in the length according to pressure applied to an object in order to expand it in the radial direction. 
         [0000]    
       
         
           
             
               
                 
                   Foreshortening 
                   = 
                   
                     
                       
                         
                           L 
                           original 
                         
                         - 
                         
                           L 
                           load 
                         
                       
                       
                         L 
                         original 
                       
                     
                      
                     
                       ( 
                       % 
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0077]    Where L original  denotes the initial length of the stent  100  and L load  denotes a length when the stent  100  is load expanded in the radial direction. In an embodiment of the present invention, Foreshortening is calculated as 2˜3%. 
         [0078]    The relationship between the change in the length and the radius of the stent  100  when the stent  100  is expanded in the radial direction at the initial state and the change of the length and the radius of the stent  100  when the expanded stent  100  is reduced can be checked by a measurement known as Recoil. Recoil is distinguished between Longitudinal Recoil indicating the change in the length in the length direction of the stent  100  and Radial Recoil indicating the change in the radius in the radial direction, which are expressed as following equations (2) and (3), respectively. 
         [0000]    
       
         
           
             
               
                 
                   
                     Logitudinal 
                      
                     
                         
                     
                      
                     Recoil 
                   
                   = 
                   
                     
                       
                         
                           L 
                           load 
                         
                         - 
                         
                           L 
                           unload 
                         
                       
                       
                         L 
                         load 
                       
                     
                     × 
                     100 
                      
                     % 
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0079]    Where L load  denotes a length when the stent  100  is expanded in the radial direction and L unload  denotes a length when it is shrunk. 
         [0000]    
       
         
           
             
               
                 
                   
                     Radial 
                      
                     
                         
                     
                      
                     Recoil 
                   
                   = 
                   
                     
                       
                         
                           D 
                           load 
                         
                         - 
                         
                           D 
                           unload 
                         
                       
                       
                         D 
                         load 
                       
                     
                     × 
                     100 
                      
                     % 
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
         [0080]    Where D load  denotes a radius when the stent  100  is expanded in the radial direction and D unload  denotes a radius when it is reduced. In an embodiment of the present invention, Redial Recoil is calculated as 13˜16%. 
         [0081]    As shown in  FIG. 6 , Side Branch Access measures how far a new stent can be inserted into a blood vessel where another stent has already been inserted into another blood vessel adjacent to the blood vessel by comparing the entire area of a closed curve formed by a primary cell and connected cells or the length thereof between the two stents. Therefore, the larger the entire area of the length of the closed curve, the easier it is for the stent  100  to be inserted into the blood vessel. 
         [0082]    It is preferable that the stent  100  is made of material harmless to the human body, for example, Co—Cr alloy group, stainless material, Nitinol, etc. 
         [0083]    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.